Research papers

The current filters are: Starting year = 2021, Ending year = 2022
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Biguino B., Olmedo E., Ferreira A., Zacarias N., Lamas L., Favareto L., Palma C., Borges C., Teles-Machado A., Dias J., Castellanos P., Brito A.C. (2022)
Remote Sensing, 14, 2, 423. DOI: 10.3390/rs14020423. (BibTeX: biguino.etal.2022)
Abstract: See
Salinity is one of the oldest parameters being measured in oceanography and one of the most important to study in the context of climate change. However, its quantification by satellite remote sensing has been a relatively recent achievement. Currently, after over ten years of data gathering, there are still many challenges in quantifying salinity from space, especially when it is intended for coastal environments study. That is mainly due to the spatial resolution of the available products. Recently, a new higher resolution (5 km) L4 SMOS sea surface salinity (SSS) product was developed by the Barcelona Expert Center (BEC). In this study, the quality of this product was tested along the Western Iberian Coast through its comparison with in situ observations and modelled salinity estimates (CMEMS IBI Ocean Reanalysis system). Moreover, several parameters such as the temperature and depth of in situ measurements were tested to identify the variables or processes that induced higher errors in the product or influenced its performance. Lastly, a seasonal and interannual analysis was conducted considering data between 2011 to 2019 to test the product as a potential tool for long-term studies. The results obtained in the present analysis showed a high potential of using the L4 BEC SSS SMOS product in extended temporal and spatial analyses along the Portuguese coast. A good correlation between the satellite and the in situ datasets was observed, and the satellite dataset showed lower errors in retrieving coastal salinities than the oceanic model. Overall, the distance to the coast and the closest rivers were the factors that most influenced the quality of the product. The present analysis showed that great progress has been made in deriving coastal salinity over the years and that the SMOS SSS product is a valuable contribution to worldwide climatological studies. In addition, these results reinforce the need to continue developing satellite remote sensing products as a global and cost-effective methodology for long-term studie
Keywords: surface salinity, SMOS, coastal ocean, CMEMS IBI Ocean reanalysis system, climate change
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Cazzaniga I., Zibordi G., Mélin F., Kwiatkowska E., Talone M., Dessailly D., Gossn J.I., Müller D. (2022)
IEEE Geoscience and Remote Sensing Letters, 19, 1-5. DOI: 10.1109/LGRS.2021.3136291. (BibTeX: cazzaniga.etal.2022)
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Radiometric water products from the Neural Network (NNv2) in the Alternative Atmospheric Correction (AAC) processing chain of Ocean and Land Colour Instruments (OLCI) were assessed over different marine regions. These products, not included among the operational ones, were custom produced from the Copernicus Sentinel-3 OLCI Baseline Collection 3. The assessment benefitted of in situ reference data from the Ocean Color component of the Aerosol Robotic Network (AERONET-OC) from sites representative of different water types. These included clear waters in the Western Mediterranean Sea, optically-complex waters characterized by varying concentrations of total suspended matter and chromophoric dissolved organic matter (CDOM) in the northern Adriatic Sea, and optically-complex waters characterized by very high concentrations of CDOM in the Baltic Sea. The comparison of the water-leaving radiances 𝑳𝑾𝑵 derived from OLCI data on board Sentinel-3A and Sentinel-3B with those from AERONETOC confirmed consistency between the products from the two satellite sensors. However, the accuracy of satellite data products exhibited dependence on the water type. A general underestimate of 𝑳𝑾𝑵 was observed for clear waters. Conversely, overestimates were observed for data products from optically-complex waters with the worst results obtained for CDOM-dominated waters. These findings suggest caution in exploiting NNv2 radiometric products, especially for highly absorbing and clear waters.
Keywords: Remote Sensing, Ocean Color, Validation
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González-Gambau V., Olmedo E., Turiel A., González-Haro C., García-Espriu A., Martínez J., Alenius P., Tuomi L., Catany R., Arias M., Gabarró C., Hoareau N., Umbert M., Sabia R., Fernández D. (2022)
Earth System Science Data, 14, 2343-2368. DOI: 10.5194/essd-14-2343-2022. (BibTeX: gonzalezgambau.etal.2022)
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This paper presents the first Soil Moisture and Ocean Salinity (SMOS) Sea Surface Salinity (SSS) dedicated products over the Baltic Sea. The SSS retrieval from L-band brightness temperature (TB) measurements over this basin is really challenging due to important technical issues, such as the land–sea and ice–sea contamination, the high contamination by radio-frequency interference (RFI) sources, the low sensitivity of L-band TB at SSS changes in cold waters, and the poor characterization of dielectric constant models for the low SSS range in the basin. For these reasons, exploratory research in the algorithms used from the level 0 up to level 4 has been required to develop these dedicated products. This work has been performed in the framework of the European Space Agency regional initiative Baltic+ Salinity Dynamics. Two Baltic+ SSS products have been generated for the period 2011–2019 and are freely distributed: the Level 3 (L3) product (daily generated 9 d maps in a 0.25◦ grid; https://doi.org/10.20350/digitalCSIC/13859, González-Gambau et al., 2021a) and the Level 4 (L4) product (daily maps in a 0.05◦ grid; https://doi.org/10.20350/ digitalCSIC/13860, González-Gambau et al., 2021b), which are computed by applying multifractal fusion to L3 SSS with SST maps. The accuracy of L3 SSS products is typically around 0.7–0.8 psu. The L4 product has an improved spatiotemporal resolution with respect to the L3 and the accuracy is typically around 0.4 psu. Regions with the highest errors and limited coverage are located in Arkona and Bornholm basins and Gulfs of Finland and Riga. The impact assessment of Baltic+ SSS products has shown that they can help in the understanding of salinity dynamics in the basin. They complement the temporally and spatially very sparse in situ measurements, covering data gaps in the region, and they can also be useful for the validation of numerical models, particularly in areas where in situ data are very sparse.
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Isern-Fontanet J., Capet X., Turiel A., Olmedo E., González-Haro C. (2022)
Geophysical Research Letters, 49 DOI: 10.1029/2022GL098038. (BibTeX: isernfontanet.etal.2022)
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The contribution of ocean fronts to the properties and temporal evolution of Sea Surface Temperature (SST) structure functions have been investigated using a numerical model of the California Current system. First, the intensity of fronts have been quantified by using singularity exponents. Then, leaning on the multifractal theory of turbulence, we show that the departure of the scaling of the structure functions from a straight line, known as anomalous scaling, depends on the intensity of the strongest fronts. These fronts, at their turn, are closely related to the seasonal change of intensity of the coastal upwelling characteristics of this area. Our study points to the need to correctly reproduce the intensity of the strongest fronts and, consequently, properly model processes such as coastal upwelling in order to reproduce SST statistics in ocean models.
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King G.P., Portabella M., Lin W., Stoffelen A. (2022)
Remote Sensing, 14, 5, 1147. DOI: 10.3390/rs14051147. (BibTeX: king.etal.2022)
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Air–sea fluxes are greatly enhanced by the winds and vertical exchanges generated by mesoscale convective systems (MCSs). In contrast to global numerical weather prediction models, space-borne scatterometers are able to resolve the small-scale wind variability in and near MCSs at the ocean surface. Downbursts of heavy rain in MCSs produce strong gusts and large divergence and vorticity in surface winds. In this paper, 12.5 km wind fields from the ASCAT-A and ASCAT-B tandem mission, collocated with short time series of Meteosat Second Generation 3 km rain fields, are used to quantify correlations between wind divergence and rain in the Inter-Tropical Convergence Zone (ITCZ) of the Atlantic Ocean. We show that when there is extreme rain, there is extreme convergence/divergence in the vicinity. Probability distributions for wind divergence and rain rates were found to be heavy-tailed: exponential tails for wind divergence (P∼e −αδ with slopes that flatten with increasing rain rate), and power-law tails for rain rates (P∼(R ∗ ) −β with a slower and approximately equal decay for the extremes of convergence and divergence). Co-occurring points are tabulated in two-by-two contingency tables from which cross-correlations are calculated in terms of the odds and odds ratio for each time lag in the collocation. The odds ratio for extreme convergence and extreme divergence both have a well-defined peak. The divergence time lag is close to zero, while it is 30 min for the convergence peak, implying that extreme rain generally appears after (lags) extreme convergence. The temporal scale of moist convection is thus determined by the slower updraft process, as expected. A structural analysis was carried out that demonstrates consistency with the known structure of MCSs. This work demonstrates that (tandem) ASCAT winds are well suited for air–sea exchange studies in moist convection
Keywords: air–sea interaction; scatterometer winds; ASCAT; Meteosat Second Generation; ocean wind divergence; tropical convection; mesoscale convective systems; compound extremes; heavytailed PDFs
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Latasa M., Scharek R., Anxelu X., Morán G., Gutiérrez-Rodríguez A., Emelianov M., Salat J., Vidal M., Estrada M. (2022)
Progress in Oceanography, 201, 102737 DOI: 10.1016/j.pocean.2021.102737. (BibTeX: latasa.etal.2022)
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A detailed study of phytoplankton composition and dynamics was carried out during three contrasting situations (cruises F1, F2, and F3) in the northwestern (NW) Mediterranean Sea. Haptophytes, diatoms, and green algae dominated in F1, during the spring bloom, with high nutrients and high phytoplankton biomass. In F2, the postbloom situation with a still weak stratification and lower nutrient concentrations, we found a high spatial variability. Stations were clearly dominated by either Synechococcus, haptophytes or cryptophytes; with Syn echococcus reaching the highest abundance (4 × 105 cells mL− 1, 60% of the integrated chlorophyll a) reported to date for the open Mediterranean Sea. Cryptophytes accumulated close to the surface in very shallow mixed layer stations. In late summer, F3 revealed a fully developed stratification with low nutrients and a marked deep chlorophyll maximum (DCM). Prochlorococcus was present only during this cruise, mainly in deep layers together with haptophytes and pelagophytes, while haptophytes and Synechococcus dominated the upper mixed layer. Flow cytometry (FCM) and pigment-based abundance estimates for Prochlorococcus, Synechococcus and cryptophytes were well correlated, as happened also between small picoeukaryotes (FCM) and green algae (pigments), and between large picoeukaryotes (FCM) and haptophytes (pigments). Dinoflagellate abundance by microscopy and by pigments did not agree well, probably due to the presence of heterotrophic forms or because they contained pigments other than peridinin, the standard dinoflagellate marker. The decrease in size of the FCM large picoeukaryotes group with depth was presumably related to the increasing contribution of pelagophytes, with smaller cells than haptophytes, the other main component of this fraction. Cell size increase of Prochlorococcus and Synechococcus with depth suggests vertical segregation of genotypes or photoadaptation. The groups’ ecological preferences are presented with respect to depth and nutrient concentrations. Synechococcus and cryptophytes occupied shallow layers; diatoms, green algae and Prochlorococcus showed a tendency for deep layers and pelagophytes for even deeper layers, while haptophyte and dinoflagellate allocations were less clear. As for nutrients, the maximum relative contributions of green algae and especially diatoms occurred when dissolved inorganic phosphorus (DIP) concentrations were highest, of Prochlorococcus, dinoflagellates and pelagophytes when lowest, and of Synechococcus and cryptophytes when DIP concentrations were low but not minimal. The contribution of haptophytes did not show a relationship with DIP concentration. These results from individual groups stand as significant exceptions to the general relationship between phytoplankton cell size and nutrient availability.
Keywords: HPLC CHEMTAX Spring bloom Synechococcus bloom Ecological preferences Size distribution
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Liu S., Lin W., Portabella M., Wang Z. (2022)
Remote Sensing, 14, 4, 1035. DOI: 10.3390/rs14041035. (BibTeX: liu.etal.2022)
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The estimation of tropical cyclone (TC) intensity using Ku-band scatterometer data is challenging due to rain perturbation and signal saturation in the radar backscatter measurements. In this paper, an alternative approach to directly taking the maximum scatterometer-derived wind speed is proposed to assess the TC intensity. First, the TC center location is identified based on the unique characteristics of wind stress divergence/curl near the TC core. Then the radial extent of 17-m/s winds (i.e., R17) is calculated using the wind field data from the Haiyang-2B (HY-2B) scatterometer (HSCAT). The feasibility of HSCAT wind radii in determining TC intensity is evaluated using the maximum sustained wind speed (MSW) in the China Meteorological Administration best-track database. It shows that the HSCAT R17 value generally better correlates with the best-track MSW than the HSCAT maximum wind speed, therefore indicating the potential of using the HSCAT data to improve the TC nowcasting capabilities.
Keywords: scatterometer; tropical cyclone; wind radii; intensity; HY-2 satellite
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Lloret J., Turiel A., Solé J., Berdalet E., Sabatés A., Olivares A., Gili J.M., Vila-Subirós J., Sardá R. (2022)
Science of The Total Environment, 824, 153803 DOI: 10.1016/j.scitotenv.2022.153803. (BibTeX: lloret.etal.2022)
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The need for alternative energy systems like offshore wind power to move towards the Green Deal objectives is undeniable. However, it is also increasingly clear that biodiversity loss and climate change are interconnected issues that must be tackled in unison. In this paper we highlight that offshore wind farms (OWF) in the Mediterranean Sea (MS) pose serious environmental risks to the seabed and the biodiversity of many areas due to the particular ecological and socioeconomic characteristics and vulnerability of this semi-enclosed sea. The MS hosts a high diversity of species and habitats, many of which are threatened. Furthermore, valuable species, habitats, and seascapes for citizens\' health and well-being coexist with compounding effects of other economic activities (cruises, maritime transport, tourism activities, fisheries and aquaculture) in a busy space on a narrower continental shelf than in other European seas. We argue that simply importing the OWF models from the northern European seas, which are mostly based on large scale projects, to other seas like the Mediterranean is not straightforward. The risks of implementing these wind farms in the MS have not yet been well evaluated and, considering the Precautionary Principle incorporated into the Marine Strategy Framework Directive and the Maritime Spatial Planning Directive, they should not be ignored. We propose that OWF development in the MS should be excluded from high biodiversity areas containing sensitive and threatened species and habitats, particularly those situated inside or in the vicinity of Marine Protected Areas or areas with valuable seascapes. In the absence of a clearer and comprehensive EU planning of wind farms in the MS, the trade-off between the benefits (climate goals) and risks (environmental and socioeconomic impacts) of OWF could be unbalanced in favor of the risks
Keywords: Offshore energy Marine protected areas, environmental impacts, biodiversity Maritime spatial planning, seascape Renewable energy Mediterranean Sea
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Marín-Beltrán I., Demaria F., Ofelio C., Serra L.M., Turiel A., Ripple W.J., Mukul S.A., Costa M.C. (2022)
Science of The Total Environment, 811, 151359 DOI: 10.1016/j.scitotenv.2021.151359. (BibTeX: marinbeltran.etal.2022)
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The metabolism of contemporary industrialized societies, that is their energy and material flows, leads to the overconsumption and waste of natural resources, two factors often disregarded in the global ecological equation. In this Discussion article, we examine the amount of natural resources that is increasingly being consumed and wasted by humanity, and propose solutions to reverse this pattern. Since the beginning of the 20th century, societies, especially from industrialized countries, have been wasting resources in different ways. On one hand, the metabolism of industrial societies relies on non-renewable resources. On the other hand, yearly, we directly waste or mismanage around 78% of the total water withdrawn, 49% of the food produced, 31% of the energy produced, 85% of ores and 26% of non-metallic minerals extracted, respectively. As a consequence, natural resources are getting depleted and ecosystems polluted, leading to irreversible environmental changes, biological loss and social conflicts. To reduce the anthropogenic footprint in the planet, and live in harmony with other species and ourselves, we suggest to shift the current economic model based on infinite growth and reduce inequality between and within countries, following a degrowth strategy in industrialized countries. Public education to reduce superfluous consumption is also necessary. In addition, we propose a set of technological strategies to improve the management of natural resources towards circular economies that, like ecosystems, rely only upon renewable resources.
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Martínez J., Gabarró C., Turiel A., González-Gambau V., Umbert M., Hoareau N., González-Haro C., Olmedo E., Arias M., Catany R., Bertino L., Raj R.P., Xie J., Sabia R., Fernández D. (2022)
Earth System Science Data, 14, 1, 307–323. DOI: 10.5194/essd-14-307-2022. (BibTeX: martinez.etal.2022)
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Measuring salinity from space is challenging since the sensitivity of the brightness temperature (TB) to sea surface salinity (SSS) is low (about 0.5 K psu−1 ), while the SSS range in the open ocean is narrow (about 5 psu, if river discharge areas are not considered). This translates into a high accuracy requirement of the radiometer (about 2–3 K). Moreover, the sensitivity of the TB to SSS at cold waters is even lower (0.3 K psu−1 ), making the retrieval of the SSS in the cold waters even more challenging. Due to this limitation, the ESA launched a specific initiative in 2019, the Arctic+Salinity project (AO/1-9158/18/I-BG), to produce an enhanced Arctic SSS product with better quality and resolution than the available products. This paper presents the methodologies used to produce the new enhanced Arctic SMOS SSS product (Martínez et al., 2019) . The product consists of 9 d averaged maps in an EASE 2.0 grid of 25 km. The product is freely distributed from the Barcelona Expert Center (BEC, http://bec.icm.csic.es/, last access: 25 January 2022) with the DOI number https://doi.org/10.20350/digitalCSIC/12620 (Martínez et al., 2019). The major change in this new product is its improvement of the effective spatial resolution that permits better monitoring of the mesoscale structures (large than 50 km), which benefits the river discharge monitoring.
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Miracca-Lage M., González-Haro C., Campagnoli-Napolitano D., Isern-Fontanet J., Simionatto-Polito P. (2022)
Journal of Geophysical Research: Oceans, 127 DOI: 10.1029/2021JC018001. (BibTeX: miraccalage.etal.2022)
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Satellite altimeters provide quasi-global measurements of sea surface height, and from those the vertically integrated geostrophic velocity can be directly estimated, but not its vertical structure. This study discusses whether the mesoscale (30–400 km) dynamics of three regions in the South Atlantic can be described by the surface quasi-geostrophic (SQG) theory, both at the surface and in depth, using outputs from an ocean general circulation model. At these scales, the model surface eddy kinetic energy (EKE) spectra show slopes close to k−5/3 (k−3) in winter (summer), characterizing the SQG and quasi-geostrophic (QG) turbulence regimes. We use surface density and temperature to (a) reconstruct the stream function under the SQG theory, (b) assess its capability of reproducing mesoscale motions, and (c) identify the main parameters that improve such reconstruction. For mixed layers shallower than 100 m, the changes in the mixed-layer depth contributes nine times more to the surface SQG reconstruction than the EKE, indicating the strong connection between the quality of the reconstruction and the seasonality of the mixed layer. To further explore the reconstruction vertical extension, we add the barotropic and first baroclinic QG modes to the surface solution. The SQG solutions reproduce the model density and geostrophic velocities in winter, whereas in summer, the interior QG modes prevail. Together, these solutions can improve surface correlations (>0.98) and can depict spatial patterns of mesoscale structures in both the horizontal and vertical domains. Improved spatial resolution from upcoming altimeter missions poses a motivating scenario to extend our findings into future observational studies.
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Nicolaus M., Perovich D.K., Spreen G., Granskog M.A., von Albedyll L., Angelopoulos M., Anhaus P., Arndt S., Belter H.J., Bessonov V., , Brauchle J., Calmer R., Cardellach E., Cheng B., , Dadic R., Damm E., de Boer G., Demir O., Dethloff K., Divine D.V., Fong A.A., Fons S., Frey M.M., Fuchs N., Gabarró C., , Goessling H.F., Gradinger R., Haapala J., Haas C., , Hannula H.R., Hen.dricks S, Herber A., Heuzé C., , Hoyland K.V., Huntemann M., Hutchings J.K., Hwang B., , Jacobi H.W., Jaggi M., Jutila A., Kaleschke L., Katlein C., , Krampe D., Kristensen S.S., Krumpen T., Kurtz N., , Lange B.A., Lei R., Light B., Linhardt F., Liston G.E., , Macfarlane A.R., Mahmud M., Matero I.O., Maus S., , Naderpour R., Nandan V., Niubom A., Oggier M., Oppelt N., Pätzold F., Perron C., Petrovsky T., Pirazzini R., Polashenski C., , Raphael I.A., Regnery J., Rex M., Ricker R., Riemann-Campe K., Rinke A., Rohde J., Salganik E., Scharien R.K., Schiller M., , Semmling M., Shimanchuk E., Shupe M.D., Smith M.M., , Sokolov V., Stanton T., Stroeve J., Thielke L., , Tonboe R.T., Tavri A., Tsamados M., Wagner D.N., , Webster M., Wendisch M. (2022)
Elementa: Science of the Anthropocene, 10, 1 DOI: 10.1525/ elementa.2021.000046. (BibTeX: nicolaus.etal.2022a)
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Year-round observations of the physical snow and ice properties and processes that govern the ice pack evolution and its interaction with the atmosphere and the ocean were conducted during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition of the research vessel Polarstern in the Arctic Ocean from October 2019 to September 2020. This work was embedded into the interdisciplinary design of the 5 MOSAiC teams, studying the atmosphere, the sea ice, the ocean, the ecosystem, and biogeochemical processes.The overall aim of the snow and sea ice observations during MOSAiC was to characterize the physical properties of the snow and ice cover comprehensively in the central Arctic over an entire annual cycle. This objective was achieved by detailed observations of physical properties and of energy and mass balance of snow and ice. By studying snow and sea ice dynamics over nested spatial scales from centimeters to tens of kilometers, the variability across scales can be considered. On-ice observations of in situ and remote sensing properties of the different surface types over all seasons will help to improve numerical process and climate models and to establish and validate novel satellite remote sensing methods; the linkages to accompanying airborne measurements, satellite observations, and results of numerical models are discussed. We found large spatial variabilities of snow metamorphism and thermal regimes impacting sea ice growth. We conclude that the highly variable snow cover needs to be considered in more detail (in observations, remote sensing, and models) to better understand snow-related feedback processes.The ice pack revealed rapid transformations and motions along the drift in all seasons. The number of coupled ice–ocean interface processes observed in detail are expected to guide upcoming research with respect to the changing Arctic sea ice
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Olmedo E., Turiel A., González-Gambau V., González-Haro C., García- Espriu A., Gabarró C., Portabella M., Corbella I., Martín-Neira M., Arias M., Catany R., Sabia R., Oliva R., Scipal K. (2022)
Scientific Reports, 12, 6279 DOI: 10.1038/s41598-022-10265-1. (BibTeX: olmedo.etal.2022)
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Changes in the Earth’s water cycle can be estimated by analyzing sea surface salinity. This variable reflects the balance between precipitation and evaporation over the ocean, since the upper layers of the ocean are the most sensitive to atmosphere–ocean interactions. In situ measurements lack spatial and temporal synopticity and are typically acquired at few meters below the surface. Satellite measurements, on the contrary, are synoptic, repetitive and acquired at the surface. Here we show that the satellite-derived sea surface salinity measurements evidence an intensification of the water cycle (the freshest waters become fresher and vice-versa) which is not observed at the in-situ near-surface salinity measurements. The largest positive differences between surface and near-surface salinity trends are located over regions characterized by a decrease in the mixed layer depth and the sea surface wind speed, and an increase in sea surface temperature, which is consistent with an increased stratification of the water column due to global warming. These results highlight the crucial importance of using satellites to unveil critical changes on ocean–atmosphere fluxes.
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Ortigosa I., Bardaji R., Carbonell A., Carrasco O., Castells-Sanabra M., Figuerola R., Hoareau N., Mateu J., Piera J., Puigdefabregas J., Salvador J., Simon C., Vallès-Casanova I., Pelegrí J.L. (2022)
Journal of Marine Science and Engineering, 10, 591 DOI: 10.3390/jmse100505. (BibTeX: ortigosa.etal.2022)
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Shelf waters near large cities, such as Barcelona, are affected not only by meteorological episodes but also by anthropogenic influence. Scientists usually use data from on-site coastal platforms to analyze and understand these complex water ecosystems because remote sensing satellites have low spatiotemporal resolution and do not provide reliable data so close to the coast. However, platforms with conventional oceanographic instrumentation are expensive to install and maintain. This study presents the scientific adaptation and initial measurements from a “patí a vela”, which is a very popular unipersonal catamaran in Barcelona. This versatile sailing vessel has been adapted to contain several low-cost sensors and instruments to measure water properties. Here, we describe the setup of a multi-parameter prototype, and then focus on results obtained using a low-cost temperature profiler. First, the temperature data are compared and validated with another conventional oceanographic instrument used in monthly oceanographic cruises. Then, field measurements between July and November 2021 are used to explore the relationship between air and water temperature in the Barcelona coastal area, showing the seasonal evolution of the temperature profile. We conclude that citizen sampling from fully sustainable sailing boats may turn into an effective strategy to monitor the urban coastal waters.
Keywords: scientific sailing boat; low-cost sensors; temperature-depth profiler; citizen science
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Ostrovskii A.G., Emelianov M.V., Kochetov O.Y., Kremenetskiy V.V., Shvoev D.A., Volkov S.V., Zatsepin A.G., Korovchinsky N.M., Olshanskiy V.M., Olchev A.V. (2022)
Journal of Marine Science and Engineering, 10, 322 DOI: 10.3390/jmse10030322. (BibTeX: ostrovskii.etal.2022)
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Biogeochemical cycles of carbon transformation throughout the euphotic zone of the sea are controlled by physical processes, e.g., daily thermocline, variation in solar irradiance, thermohaline convection, and intermittent mixing. These processes should be regularly observed with sufficient time resolution at fixed geographical locations. This study provides a brief overview of the carbon observational site in the Northeastern Black Sea. The focus is on the design of a new tethered profiler Winchi for the inner continental shelf part of the site. The profiler hull and two outriggers comprise an open trimaran platform that is positively buoyant and tends to maintain a horizontal position in the water. The lower end of the winch wire is secured to the bottom anchor. By unwinding/winding the wire, the profiler ascends/descends while measuring the depth profiles of marine environment parameters ranging from the seafloor to air–sea interface. After surfacing, the profiler determines its location using the Global Positioning System (GPS) and transmits data to (and from) a server on land through the Global System for Mobile Communications (GSM). Initial field tests with the Winchi profiler at the Northeastern Black Sea shelf exhibited promising results. We report these early tests to demonstrate the use of Winchi.
Keywords: greenhouse gases; carbon flux; tethered profiler; winch; real-time data transmission; Black Sea
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Polverari F., Portabella M., Lin W., Saap J.W., Stoffelen A., Jelenak Z., Chang P.S. (2022)
IEEE Transactions on Geoscience and Remote Sensing, 60 DOI: 10.1109/TGRS.2021.3079898. (BibTeX: polverari.etal.2022)
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Accurate high and extreme sea surface wind observations are essential for the meteorological, ocean, and climate applications. To properly assess and calibrate the current and future satellite-derived extreme winds, including those from the C-band scatterometers, building a consolidated high and extreme wind reference data set is crucial. In this work, a new approach is presented to assess the consistency between moored buoys and stepped-frequency microwave radiometer (SFMR)- derived winds. To overcome the absence of abundant direct collocations between these two data sets, the reprocessed Advanced Scatterometer (ASCAT)-A winds at the 12.5-km resolution, from 2009 to 2017, have been used to perform an indirect SFMR/buoy winds’ intercomparison. The ASCAT/SFMR analysis reveals an ASCAT wind underestimation for winds of above 15 m/s. SFMR measurements are calibrated using GPS drop-wind-sondes (dropsondes) data and averaged along-track to represent ASCAT spatially. On the other hand, ASCAT and buoy winds are in good agreement up to 25 m/s. The buoy high-wind quality has been confirmed using a triple collocation approach. Comparing these results, both SFMR and buoy winds appear to be highly correlated with ASCAT at the high-wind regime; however, they show a very different wind speed scaling. An SFMR-based recalibration of ASCAT winds is proposed, the so-called ASCAT dropsonde-scale winds, for use by the extreme wind operational community. However, further work is required to reconcile dropsonde (thus, SFMR) and buoy wind measurements under extreme wind conditions
Keywords: High and extreme wind speeds, microwave radiometry, ocean wind reference, spaceborne scatterometry
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Salvador X., Fernández-Vilert R., Moles J. (2022)
Journal of Natural history, 56, 5-8, 265-310. DOI: 10.1080/00222933.2022.2040630. (BibTeX: salvador.etal.2022)
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Citizen (or community) science has provided copious and valuable information about charismatic marine taxa such as heterobranch gastropods, thus contributing enormously to the known geographic distribution of many sea slug species. This study reports new records of elusive sea slugs in the coastal western Mediterranean (especially on the Catalan and French Mediterranean coasts) and contributes to new ecological information regarding their phenology, diet and behaviour. Out of 39 species reported here, 23 are new records for the Catalan coast (NE Spain), three are new records of pelagic pteropods for the Spanish Iberian coast, and eight are new records for the French Mediterranean coast. With 25 species found active at night, this study highlights the importance of sampling at night and in shallow, often under-sampled waters with high species diversity. Shallow waters usually have less diving activity and are harder to survey with heavy scuba equipment. We believe that the high-quality photos herein and the related species information will enable researchers, divers and the community to find and recognise these rare species in the Mediterranean basin.
Keywords: marine heterobranchs; new records; uncommon species; Mediterranean Sea; byodiversity
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Viúdez A. (2022)
Journal of Fluid Mechanics, 936, A13 DOI: 10.1017/jfm.2022.73. (BibTeX: viudez.2022)
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Multipolar spherical solutions to the three-dimensional steady vorticity equation are provided. These solutions are based on the separation of radial and angular contributions in terms of the spherical Bessel functions and vector spherical harmonics, respectively. In this set of multipolar vortex solutions, the Hicks–Moffatt swirling vortex is categorized as a vortex of degree l = 1 and therefore as a vortex dipole. This swirling vortex is the three-dimensional dipole in spherical geometry equivalent to the two-dimensional Lamb–Chaplygin dipole in polar geometry. The three-dimensional dipole solution admits two linearly superposable solutions. The first one is a Trkalian flow and the second one is a cylindrical solid-body rotation with swirl. The higher l > 1 multipolar vortices found are either vanishing-helicity vortices or Trkalian flow vortices. The multipolar Trkalian flows admit two circular polarizations given by the sign of the wavenumber k. It is also found that piecewise vortex solutions, consisting of interior rotational and exterior potential flow domains, satisfying velocity continuity conditions at the vortex boundary, are possible in the general multipolar Trkalian spherical vortex. A particular polarized dipole solution in three-dimensional cylindrical geometry, consisting as well in the superposition of a Trkalian flow and a rigid motion, is also analysed. This swirling vortex may be interpreted as the three-dimensional dipole in cylindrical geometry equivalent to the two-dimensional Lamb–Chaplygin dipole in polar geometry.
Keywords: vortex flows
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Woods S.M., Daskolia M., Joly A., Bonnet P., Soacha K., Liñán S., Woods T., Piera J., Ceccaroni L. (2022)
Sustainability, 14, 4078 DOI: 10.3390/su14074078. (BibTeX: woods.etal.2022)
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There is a growing acknowledgement that citizen observatories, and other forms of citizen- generated data, have a significant role in tracking progress towards the Sustainable Development Goals. This is evident in the increasing number of Sustainable Development Goals’ indicators for which such data are already being used and in the high-level recognition of the potential role that citizen science can play. In this article, we argue that networks of citizen observatories will help realise this potential. Drawing on the Cos4Cloud project as an example, we highlight how such networks can make citizen-generated data more interoperable and accessible (among other qualities), increasing their impact and usefulness. Furthermore, we highlight other, perhaps overlooked, advantages of citizen observatories and citizen-generated data: educating and informing citizen scientists about the Sustainable Development Goals and co-creating solutions to the global challenges they addres
Keywords: citizen science; citizen observatory; Sustainable Development Goals; interoperability; co-design; education
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Zhao X., Lin W., Portabella M., Wang Z., He Y. (2022)
Remote Sensing of Environment, 274, 113015 DOI: 10.1016/j.rse.2022.113015. (BibTeX: zhao.etal.2022)
Abstract: See
The Ku-band scatterometer onboard China France Oceanography Satellite (CFOSAT) observes the sea surface with two conically scanning fan beams. Compared to the prior Ku-band pencil beam scatterometers, this innovative observing mechanism provides more independent backscatter measurements at varying incidence and azimuth angles, as such it brings challenges for the sea surface wind inversion, particularly under rainy conditions. In this paper, the rain effects on the CFOSAT SCATterometer (CSCAT) are investigated using the collocated numerical weather prediction (NWP) wind data and the Global Precipitation Measurement (GPM) microwave imager (GMI) rain data. Similar to the prior Ku-band or C-band scatterometers, the sensitivity of CSCAT radar backscatter to rain substantially varies with wind speed, radar polarization and incidence angle. However, due to the complex observation geometries, rain effects on the CSCAT retrieved winds is more complex than that of prior scatterometers, which may lead to a remarkable underestimation of CSCAT wind speed at high winds and heavy rain conditions. A simple simulation method is used to clarify the relation between the retrieved wind speed and the dependency of radar rain effects on the incidence angle. It is found that the backscatter measurements at low incidence angles, which are generally underestimated at high winds and heavy rainy conditions, have a larger influence on the wind inversion minimization, leading to much lower retrieved wind speeds than those of ECMWF and the pencil beam scatterometer (e.g., Haiyang-2B scattometer). Under low and moderate rain conditions though, a more compensated effect between low and high incidence angle measurements is found, leading to generally unbiased CSCAT high winds, in contrast to the generally underestimated pencil-beam scatterometer winds.
Keywords: CFOSAT Scatterometer Backscatter Rain effects Wind quality
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Zibordi G., Talone M., Mélin F. (2022)
IEEE Geoscience and Remote Sensing Letters, 19, 1502905, 1-5. DOI: 10.1109/LGRS.2021.3134876. (BibTeX: zibordi.etal.2022)
Abstract: See
The quantification of uncertainties affecting satellite ocean color products is a fundamental step to ensure their compliance with mission and science requirements. This work investigated a methodology relying on the use of in situ radiometric data with known uncertainties to determine those affecting matching satellite data. By exploiting in situ radiometric data from the Ocean Color component of the Aerosol Robotic Network (AERONET-OC), an advanced method was applied to radiometric data products from the Ocean and Land Color Instruments onboard the Sentinel-3A satellite (OLCI-A) and the Visible Infrared Imager Radiometer Suite onboard the Suomi National-Polar Orbiting Partnership satellite (VIIRS-S). The results from the analysis support the relevance of the method proposed.
Keywords: Ocean color, remote sensing, uncertainties
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Zibordi G., Kwiatkowska E., Mélin F., Talone M., Cazzaniga I., Dessailly D., Gossn J.I. (2022)
Remote Sensing of Environment, 272, 112911. DOI: 10.1016/j.rse.2022.112911. (BibTeX: zibordi.etal.2022a)
Abstract: See
The Ocean and Land Color Instruments (OLCI) operated onboard the Copernicus Sentinel-3 satellites are providing globally distributed Ocean Color Radiometry (OCR) data products of relevance for environmental and climate applications. This work summarizes results on the assessment of fundamental OCR data from the Operational Baseline 3 Collection OL_L2M.003.01 of OLCI-A and OLCI-B onboard Sentinel-3A and Sentinel-3B, respectively. Evaluated products are the satellite derived normalized water-leaving radiance LWN(λ), aerosol optical depth at 865 nm τa(865) and Ångstrom ¨ exponent α determined in the near-infrared spectral region. The analyses were performed relying on in situ reference data from the Ocean Color component of the Aerosol Robotic Network (AERONET-OC) from sites representative of diverse water types. The comparison of OLCI-A and OLCI-B with AERONET-OC LWN(λ) for oligotrophic/mesotrophic waters shows cross-mission consistent spectral median percent differences (i.e., biases) varying within ±6% at the blue-green center-wavelengths. The analysis of data from regions characterized by optically complex waters, however, displays systematic negative biases for both OLCI-A and OLCI-B further increasing for waters dominated by chromophoric dissolved organic matter, thus suggesting a dependence of the atmospheric correction on water type. The direct inter-comparison of OLCI-B and OLCI-A LWN(λ) from the Tandem Phase characterized by Sentinel-3B and Sentinel-3A flying 30 s apart on the same orbit, shows spectral median percent differences lower than ±1% in the 412–560 nm interval, of approximately +5% at 620 and 665 nm, and − 7% at 400 nm. However, outside the Tandem Phase, the intercomparison of OLCI-B and OLCI-A data products indicates large and systematic differences explained by a notable dependence on the viewing angle. The evaluation of τa(865) and α across different geographic regions exhibits overestimated values between +48 and + 79% for the former and underestimated values between − 28% and − 41% for the latter. A complementary evaluation of OCR data products from the Visible Infrared Imager Radiometer Suite on board the Suomi National Polar-orbiting Partnership (VIIRS-S), proposed as a further indirect term of reference for OLCI-A and OLCI-B data, shows large underestimates of LWN(λ) with respect to the in situ reference data in the various water types at 410 nm. Nevertheless, opposite to OLCI-A and OLCI-B data products, absolute differences between VIIRS-S and in situ reference data do not reveal any large or systematic dependence on water type and satellite viewing angle. Overall results suggest the need for further developing the OLCI-A and OLCI-B atmospheric correction, possibly improving the capability to identify aerosol types and to model scattering processes.
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Arjona-Camas M., Puig P., Palanques A., Durán R., White M., Paradis S., Emelianov M. (2021)
Marine Geophysical Researches, 42, 38 DOI: 10.1007/s11001-021-09457-7. (BibTeX: arjonacamas.etal.2021)
Abstract: See
Increases of water turbidity and suspended sediment transport in submarine canyons have been associated with high-energy events such as storms, river foods and dense shelf water cascading (DSWC), and occasionally with bottom trawling along canyon fanks and rims. To assess the variations on the water column turbidity and sediment transport in the Palamós Canyon linked to both natural and trawling-induced processes, an autonomous hydrographic profler, as well as a near-bottom current meter and a turbidimeter were deployed in the canyon axis (929 m depth) from February to June 2017, covering a trawling turbidity during the trawling closure were mostly associated with storms and DSWC events, transporting turbid dense waters into the canyon. In absence of such events, the water column displayed low suspended sediment concentrations (~ 0.3 mg L−1 ) until the trawling season began, when particulate matter detachments, ranging between > 1 mg L−1 and 3.8 mg L−1 , were observed at the water depths where the trawling grounds are found. During the trawling closure, high near-bottom suspended sediment fuxes (35–44 g m−2 s −1 ) were sporadically registered at ~ 920 m depth associated with a major storm and DSWC event. Smaller but more frequent increases of near-bottom suspended sediment fuxes (0.1–1.4 g m−2 s −1 ) were recorded during trawling activities. Despite these smaller trawling-induced suspended sediment fuxes, 30 days of continuous bottom trawling activity transported a total amount of 40 kg m−2 , of similar magnitude to that generated by a major DSWC event (50 kg m−2 ). Since bottom trawling in Palamós Canyon is practiced on a daily basis throughout the year, a much larger contribution of anthropogenically derived water turbidity and suspended sediment transport can be expected.
Keywords: Palamós Canyon · Dense shelf water cascading (DSWC) · Bottom trawling · Sediment transport · Nepheloid structure · NW Mediterranean
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Boutin J., Reul N., Koehler J., Martin A., Catany R., Guimbard S., Rouffi F., Vergely J.L., Arias M., Chakroun M., Corato G., Estella-Perez V., Hasson A., Josey S., Khvorostyanov D., , Mignot J., Olivier L., Reverdin G., Stammer D., Supply A., Thouvenin-Masson C., Turiel A., Vialard J., Cipollini P., Donlon C., Sabia R., Mecklenburg S. (2021)
Journal of Geophysical Research: Oceans, 126, 11 DOI: 10.1029/2021JC017676. (BibTeX: boutin.etal.2021)
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Sea Surface Salinity (SSS) is an increasingly used Essential Ocean and Climate Variable. The Soil Moisture and Ocean Salinity (SMOS), Aquarius, and Soil Moisture Active Passive (SMAP) satellite missions all provide SSS measurements, with very different instrumental features leading to specific measurement characteristics. The Climate Change Initiative Salinity project (CCI + SSS) aims to produce a SSS Climate Data Record (CDR) that addresses well-established user needs based on those satellite measurements. To generate a homogeneous CDR, instrumental differences are carefully adjusted based on in-depth analysis of the measurements themselves, together with some limited use of independent reference data. An optimal interpolation in the time domain without temporal relaxation to reference data or spatial smoothing is applied. This allows preserving the original datasets variability. SSS CCI fields are well suited for monitoring weekly to interannual signals, at spatial scales ranging from 50 km to the basin scale. They display large year-to-year seasonal variations over the 2010–2019 decade, sometimes by more than ±0.4 over large regions. The robust standard deviation of the monthly CCI SSS minus in situ Argo salinities is 0.15 globally, while it is at least 0.20 with individual satellite SSS fields. r2 is 0.97, similar or better than with original datasets. The correlation with independent ship thermosalinographs SSS further highlights the CCI data set excellent performance, especially near land areas. During the SMOS-Aquarius period, when the representativity uncertainties are the largest, r2 is 0.84 with CCI while it is 0.48 with the Aquarius original data set. SSS CCI data are freely available and will be updated and extended as more satellite data become available
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F. Child S., Stearns L.A., Van Der Veen C.J., Elósegui P. (2021)
Geophysical Research Letters, 48, 15 DOI: 10.1029/2020GL090978. (BibTeX: f.child.etal.2021)
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Linear elastic fracture mechanics suggests that short-lived flow accelerations, such as the one initiated by a flooding event beneath Byrd Glacier in 2006, can form abnormally large basal crevasses at the grounding line. Airborne radar measurements acquired in 2011 reveal hundreds of basal crevasses ranging in height from urn:x wiley:00948276:media:grl62752-math-000140–335 m. Particle tracking results show that formation of the largest basal crevasse occurred at the grounding line during the 2006 flooding event. Very large basal crevasses form distinctive surface depressions directly overhead, which are observed along the Byrd Glacier flowline to the terminus of the Ross Ice Shelf. By using these surface depressions as proxies for abnormally large basal crevasses, we create a timeline of past subglacial flooding events on Byrd Glacier. Understanding the frequency of flooding events and their effect on glacier dynamics will help inform models of ice sheet stability and subglacial hydrology
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Clavel-Henry M., Solé J., Bahamon N., Carretón M., Company J.B. (2021)
Progress in Oceanography, 192, 102515. DOI: 10.1016/j.pocean.2021.102515. (BibTeX: clavelhenry.etal.2021)
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Marine fronts are oceanographic drivers for marine species dispersal, especially for their pelagic organisms like the larvae. Larvae can aggregate at the front and consequently have a limited dispersal, which in turn reduces the connectivity between marine populations. Due to the high variations in the ocean, the fronts also have annual changes (i.e., its formation period, gradient, and position), which have poorly-documented effects on larval retention. In the northwestern Mediterranean Sea, a surface density front is localized across a continental margin which is also indented by submarine canyons. There, an abundant population of the commercial deep-sea blue and red shrimp Aristeus antennatus (Crustacea: Decapoda: Dendrobranchiata: Aristeidae) inhabits the seafloor. Each summer, the shrimp offspring are released in pelagic deep-sea and access the superficial waters divided by the density front. In this study, we focused on the interannual variability of the density front influence on the larval transport of shrimps and its repercussions on the potential connectivity between shrimp populations at each front side. A particle-tracking model simulated the larval transport of A. antennatus in hydrodynamics of the northwestern Mediterranean Sea between the years 2006 and 2016. Larval drift distance and seawater density were correlated by 98%. Over the years 2006–2016, the front region retained 86% of larvae, but this rate yearly varied due to changes in density gradient and position of the front. For example, in 2010, 48% of larvae connected to zones south of the front when the density gradient was relatively low. In 2015, 99.2% of larvae were retained in the front region when the latitudinal front position and density gradient were relatively high. Interannual variability of the front position was potentially related to the strength and position of mesoscale circulation patterns. Our findings suggest that the larval retention on habitats favored by canyon productivity because of the front could explain the persistent abundance of A. antennatus population. This information is important to set or improve the fisheries management in zones with strong interannual hydrodynamic variability
Keywords: Spain, Mediterranean Sea, Deep-sea shrimp, Oceanic front, Interannual variability, Larval transport
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Clavel-Henry M., North E.W., Solé J., Bahamon N., Carretón M., Company J.B. (2021)
Deep-Sea Research. Part I: Oceanographic Research Papers, 174 DOI: 10.1016/j.dsr.2021.103558. (BibTeX: clavelhenry.etal.2021a)
Abstract: See
The deep-sea red and blue shrimp Aristeus antennatus is a commercially valuable species that occurs in the northwestern Mediterranean Sea where ripe females have been found in fishing areas. In the Palamos ´ harbor, a local management plan restricts fishing in certain locations to sustain the resource. However, little is known about the dispersal of larvae; specifically, it is not known how far larvae are transported from spawning locations and if there could be mixing of larvae between different fishing areas. The objective of this study was to estimate the spawning sites of larvae collected at 35 sampling stations, evaluate uncertainty in the estimates, and determine if larvae could be exchanged between fishing areas. The spawning sites of larvae were estimated by backward simulation of larval trajectories using a 3-dimensional coupled hydrodynamic and Lagrangian transport model. The backtracked larvae were assigned temperature-dependent stage durations based on a literature review of similar species. Results of model simulations indicated that the median distances from sampling to spawning locations were 11 and 38 km when shortest and longest pelagic durations (PD) were implemented, respectively. Sensitivity studies of backward trajectories showed that distance estimates could vary by as much as 27, 3, and 8 km due to differences in simulated PD, sub-grid-scale turbulence, and advection, respectively. Larvae from 13 of the 35 sampling stations were tracked back to multiple fishing grounds, suggesting that mixing of larvae from different fishing areas could occur. For example, for the sampling stations within the restricted area of Palamos, 35% of simulated larvae came from the restricted area itself, and 0.9% and 10% of larvae came from neighboring areas to the north and south, respectively. These results suggest that larval transport may connect subpopulations of A. antennatus across different fishing areas, an idea that may help inform regional management plans.
Keywords: Aristeus antennatus Backtracking model, Larval dispersal, Northwestern Mediterranean Sea, spawning sites
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, Holben B.N., Talone M., D\'Alimonte D., Slutsker I., Giles D.M., Sorokin M. (2021)
Journal of Atmospheric and Oceanic Technology, 38, 725-746. DOI: 10.1175/JTECH-D-20-0085.1. (BibTeX: .etal.2021b)
Abstract: See
The Ocean Color Component of the Aerosol Robotic Network (AERONET-OC) supports activities related to ocean color such as validation of satellite data products, assessment of atmospheric correction schemes, and evaluation of bio-optical models through globally distributed standardized measurements of water-leaving radiance and aerosol optical depth. In view of duly assisting the AERONET-OC data user community, this work (i) summarizes the latest investigations on a number of scientific issues related to above-water radiometry, (ii) emphasizes the network expansion that from 2002 until the end of 2020 integrated 31 effective measurement sites, (iii) shows the equivalence of data product accuracy across sites and time for measurements performed with different instrument series, (iv) illustrates the variety of water types represented by the network sites ensuring validation activities across a diversity of observation conditions, and (v) documents the availability of water-leaving radiance data corrected for bidirectional effects by applying a method specifically developed for chlorophyll-a-dominated waters and an alternative one that is likely suitable for any water type
Keywords: In situ oceanic observations; Instrumentation/sensors; Quality assurance/control; Remote sensing
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Herbert C., Munoz-Martin J.F., Llaveria D., Pablos M., Camps A. (2021)
Remote Sensing, 13, 1366. DOI: 10.3390/rs13071366. (BibTeX: herbert.etal.2021)
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Several methods have been developed to provide polar maps of sea ice thickness (SIT) from L-band brightness temperature (TB) and altimetry data. Current process-based inversion methods to yield SIT fail to address the complex surface characteristics because sea ice is subject to strong seasonal dynamics and ice-physical properties are often non-linearly related. Neural networks can be trained to find hidden links among large datasets and often perform better on convoluted problems for which traditional approaches miss out important relationships between the observations. The FSSCat mission launched on 3 September 2020, carries the Flexible Microwave Payload-2 (FMPL-2), which contains the first Reflected Global Navigation Satellite System (GNSS-R) and L-band radiometer on board a CubeSat—designed to provide TB data on global coverage for soil moisture retrieval, and sea ice applications. This work investigates a predictive regression neural network approach with the goal to infer SIT using FMPL-2 TB and ancillary data (sea ice concentration, surface temperature, and sea ice freeboard). Two models—covering thin ice up to 0.6 m and full-range thickness—were separately trained on Arctic data in a two-month period from mid-October to the beginning of December 2020, while using ground truth data derived from the Soil Moisture and Ocean Salinity (SMOS) and Cryosat-2 missions. The thin ice and the full-range models resulted in a mean absolute error of 6.5 cm and 23 cm, respectively. Both of the models allowed for one to produce weekly composites of Arctic maps, and monthly composites of Antarctic SIT were predicted based on the Arctic full-range model. This work presents the first results of the FSSCat mission over the polar regions. It reveals the benefits of neural networks for sea ice retrievals and demonstrates that moderate-cost CubeSat missions can provide valuable data for applications in Earth observation.
Keywords: predictive regression neural networks, sea ice thickness, microwave radiometry, CubeSats
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Hernández-Morales D.P., Romaña-Torres Y., Jaramillo-Vélez A., Pelegrí J.L., Toro V.G. (2021)
Bulletin of Marine and Coastal Research, 50, 2, 9-30. DOI: 10.25268/bimc.invemar.2021.50.2.993. (BibTeX: hernandezmorales.etal.2021)
Abstract: See
Good knowledge of the coastal circulation patterns is essential for a proper management of the coastline, especially in areas with a high anthropic pressure. In order to determine the main characteristics of the coastal currents in the Gulf of Urabá, the seasonal patterns of surface circulation were measured and analyzed during times of high and low rainfall along 6 km of coastline, between the Punta de Las Vacas and Punta Yarumal coastal spit systems, in the municipality of Turbo, Antioquia. These measurements were made with surface drifters, which were launched at different tide stages and tracked for time periods based on the semi-diurnal cycle. The in-situ measurements were analyzed alongside tide and wind data from a climatic station located near the gulf. The circulation patterns behaved differently depending on the season of the year. In the rainy season, with southerly winds, the drifters moved mainly towards the north while during the dry season, with northerly winds, all the drifters moved to the south. Although the circulation patterns showed a strong relationship with the tidal cycle and wind conditions, the Turbo and El Uno Bays modified some of the drifter’s paths.
Keywords: surface circulation, wind, tide, drifters, coastal currents
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Isern-Fontanet J., García-Ladona E., González-Haro C., Turiel A., Rosell-Fieschi M., Company J.B., Padial A. (2021)
Remote Sensing, 13, 3635 DOI: 10.3390/rs13183635. (BibTeX: isernfontanet.etal.2021)
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Current observations of ocean currents are mainly based on altimetric measurements of Sea Surface Heights (SSH), however the characteristics of the present-day constellation of altimeters are only capable to retrieve surface currents at scales larger than 50–70 km. By contrast, infrared and visible radiometers reach spatial resolutions thirty times higher than altimeters under cloud-free conditions. During the last years, it has been shown how the Surface Quasi-Geostrophic (SQG) approximation is able to reconstruct surface currents from measured Sea Surface Temperature (SST), but it has not been yet used to retrieve velocities at scales shorter than those provided by altimeters. In this study, the velocity field of ocean structures with characteristic lengths between 10 and 20 km has been derived from infrared SST using the SQG approach and compared to the velocities derived from the trajectories of Lagrangian drifters. Results show that the SQG approach is able to reconstruct the direction of the velocity field with observed RMS errors between 8 and 15 degrees and linear correlations between 0.85 and 0.99. The reconstruction of the modulus of the velocity is more problematic due to two limitations of the SQG approach: the need to calibrate the level of energy and the ageostrophic contributions. If drifter trajectories are used to calibrate velocities and the analysis is restricted to small Rossby numbers, the RMS error in the range of 10 to 16 cm/s and linear correlations can be as high as 0.97.
Keywords: sea surface temperature; quasi-geostrophic equations; mesoscale and submesoscale dynamics; ocean velocity determination; mediterranean sea
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Isern-Fontanet J., Turiel A. (2021)
Journal of Physical Oceanography, 51, 8, 2639-2653. DOI: 10.1175/JPO-D-20-0256.1. (BibTeX: isernfontanet.turiel.2021)
Abstract: See
The multifractal theory of turbulence is used to investigate the energy cascade in the northwestern Atlantic Ocean. The statistics of singularity exponents of horizontal velocity gradients computed from in situ measurements at 2-km resolution are used to characterize the anomalous scaling of the velocity structure functions at depths between 50 and 500 m. Here, we show that the degree of anomalous scaling can be quantified using singularity exponents. Observations reveal, on one side, that the anomalous scaling has a linear dependence on the exponent characterizing the strongest velocity gradient and, on the other side, that the slope of this linear dependence decreases with depth. Since the observed distribution of exponents is asymmetric about the mode at all depths, we use an infinitely divisible asymmetric model of the energy cascade, the log–Poisson model, to derive the functional dependence of the anomalous scaling with the exponent of the strongest velocity gradient, as well as the dependence with dissipation. Using this model we can interpret the vertical change of the linear slope between the anomalous scaling and the exponents of the strongest velocity gradients as a change in the energy cascade. This interpretation assumes the validity of the multifractal theory of turbulence, which has been assessed in previous studies.
Keywords: Atlantic Ocean; Mesoscale processes; Turbulence; In situ oceanic observations
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Llaveria D., Munoz-Martin J.F., Herbet C., Pablos M., Park H., Camps A. (2021)
Remote Sensing, 13, 1139. DOI: 10.3390/rs13061139. (BibTeX: llaveria.etal.2021)
Abstract: See
CubeSat-based Earth Observation missions have emerged in recent times, achievingscientifically valuable data at a moderate cost. FSSCat is a two 6U CubeSats mission, winner ofthe ESA S3challenge and overall winner of the 2017 Copernicus Masters Competition, that waslaunched in September 2020. The first satellite,3Cat-5/A, carries the FMPL-2 instrument, an L-bandmicrowave radiometer and a GNSS-Reflectometer. This work presents a neural network approachfor retrieving sea ice concentration and sea ice extent maps on the Arctic and the Antarctic oceansusing FMPL-2 data. The results from the first months of operations are presented and analyzed,and the quality of the retrieved maps is assessed by comparing them with other existing sea iceconcentration maps. As compared to OSI SAF products, the overall accuracy for the sea ice extentmaps is greater than 97% using MWR data, and up to 99% when using combined GNSS-R and MWRdata. In the case of Sea ice concentration, the absolute errors are lower than 5%, with MWR and lowerthan 3% combining it with the GNSS-R. The total extent area computed using this methodology isclose, with 2.5% difference, to those computed by other well consolidated algorithms, such as OSISAF or NSIDC. The approach presented for estimating sea ice extent and concentration maps is acost-effective alternative, and using a constellation of CubeSats, it can be further improved
Keywords: sea ice, microwave radiometry, GNSS-R; nanosatellite, earth observation, neural networs
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Medina-Lopez E., McMillan D., Lazic J., Hart E., Zen S., Angeloudis A., Bannon E., Browell J., Dorling S., Dorrell R.M., Forster R., Old C., Payne G.S., Porter G., Rabaneda A.S., Sellar B., Tapoglou E., Trifonova N., Woodhouse I.H., Zampollo A. (2021)
Remote Sensing of Environment, 264, 112588 DOI: 10.1016/j.rse.2021.112588. (BibTeX: medinalopez.etal.2021)
Abstract: See
Can satellite data be used to address challenges currently faced by the Offshore Renewable Energy (ORE) sector? What benefit can satellite observations bring to resource assessment and maintenance of ORE farms? Can satellite observations be used to assess the environmental impact of offshore renewables leading towards a more sustainable ORE sector? This review paper faces these questions presenting a holistic view of the current interactions between satellite and ORE sectors, and future needs to make this partnership grow. The aim of the work is to start the conversation between these sectors by establishing a common ground. We present offshore needs and satellite technology limitations, as well as potential opportunities and areas of growth. To better understand this, the reader is guided through the history, current developments, challenges and future of offshore wind, tidal and wave energy technologies. Then, an overview on satellite observations for ocean applications is given, covering types of instruments and how they are used to provide different metocean variables, satellite performance, and data processing and integration. Past, present and future satellite missions are also discussed. Finally, the paper focuses on innovation opportunities and the potential of synergies between the ORE and satellite sectors. Specifically, we pay attention to improvements that satellite observations could bring to standard measurement techniques: assessing uncertainty, wind, tidal and wave conditions forecast, as well as environmental monitoring from space. Satellite–enabled measurement of ocean physical processes and applications for fisheries, mammals and birds, and habitat change, are also discussed in depth.
Keywords: Satellite data, Offshore renewable energy (ORE), Wind, Tidal, Wave, SAR, Sustainable ORE secto
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Munoz-Martin J.F., Onrubia R., Pascual D., Park H., Pablos M., Camps A., Rüdiger C., Walker J., Monerris A. (2021)
Remote Sensing, 13, 4, 797. DOI: 10.3390/rs13040797. (BibTeX: munozmartin.etal.2021)
Abstract: See
Global Navigation Satellite System—Reflectometry (GNSS-R) has already proven its potential for retrieving a number of geophysical parameters, including soil moisture. However, single-pass GNSS-R soil moisture retrieval is still a challenge. This study presents a comparison of two different data sets acquired with the Microwave Interferometer Reflectometer (MIR), an airborne-based dual-band (L1/E1 and L5/E5a), multiconstellation (GPS and Galileo) GNSS-R instrument with two 19-element antenna arrays with four electronically steered beams each. The instrument was flown twice over the OzNet soil moisture monitoring network in southern New South Wales (Australia): the first flight was performed after a long period without rain, and the second one just after a rain event. In this work, the impact of surface roughness and vegetation attenuation in the reflectivity of the GNSS-R signal is assessed at both L1 and L5 bands. The work analyzes the reflectivity at different integration times, and finally, an artificial neural network is used to retrieve soil moisture from the reflectivity values. The algorithm is trained and compared to a 20-m resolution downscaled soil moisture estimate derived from SMOS soil moisture, Sentinel-2 normalized difference vegetation index (NDVI) data, and ECMWF Land Surface Temperature
Keywords: GNSS-R; dual-band; airborne; soil moisture; surface roughness; vegetation
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Munoz-Martin J.F., Llaveria D., Herbert C., Pablos M., Park H., Camps A. (2021)
Remote Sensing, 13, 5, 994. DOI: 10.3390/rs13050994. (BibTeX: munozmartin.etal.2021a)
Abstract: See
The Federated Satellite System mission (FSSCat) was the winner of the 2017 Copernicus Masters Competition and the first Copernicus third-party mission based on CubeSats. One of FSSCat’s objectives is to provide coarse Soil Moisture (SM) estimations by means of passive microwave measurements collected by Flexible Microwave Payload-2 (FMPL-2). This payload is a novel CubeSat based instrument combining an L1/E1 Global Navigation Satellite Systems-Reflectometer (GNSS-R) and an L-band Microwave Radiometer (MWR) using software-defined radio. This work presents the first results over land of the first two months of operations after the commissioning phase, from 1 October to 4 December 2020. Four neural network algorithms are implemented and analyzed in terms of different sets of input features to yield maps of SM content over the Northern Hemisphere (latitudes above 45 ºN). The first algorithm uses the surface skin temperature from the European Centre of Medium-Range Weather Forecast (ECMWF) in conjunction with the 16 day averaged Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) to estimate SM and to use it as a comparison dataset for evaluating the additional models. A second approach is implemented to retrieve SM, which complements the first model using FMPL-2 L-band MWR antenna temperature measurements, showing a better performance than in the first case. The error standard deviation of this model referred to the Soil Moisture and Ocean Salinity (SMOS) SM product gridded at 36 km is 0.074 m3/m3. The third algorithm proposes a new approach to retrieve SM using FMPL-2 GNSS-R data. The mean and standard deviation of the GNSS-R reflectivity are obtained by averaging consecutive observations based on a sliding window and are further included as additional input features to the network. The model output shows an accurate SM estimation compared to a 9 km SMOS SM product, with an error of 0.087 m3/m3. Finally, a fourth model combines MWR and GNSS-R data and outperforms the previous approaches, with an error of just 0.063 m3/m3. These results demonstrate the capabilities of FMPL-2 to provide SM estimates over land with a good agreement with respect to SMOS SM
Keywords: GNSS-R; L-band; microwave radiometry; CubeSat; soil moisture
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Niell A.E., Barrett J.P., Cappallo R.J., Corey B.E., Elosegui P., Mondal D., Rajagopalan G., Ruszczyk C.A., Titus M.A. (2021)
Journal of Geodesy, 95, 65 DOI: 10.1007/s00190-021-01505-9. (BibTeX: niell.etal.2021)
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We measured the components of the 31-m-long vector between the two very-long-baseline interferometry (VLBI) antennas at the Kokee Park Geophysical Observatory (KPGO), Hawaii, with approximately 1 mm precision using phase delay observables from dedicated VLBI observations in 2016 and 2018. The two KPGO antennas are the 20 m legacy VLBI antenna and the 12 m VLBI Global Observing System (VGOS) antenna. Independent estimates of the vector between the two antennas were obtained by the National Geodetic Survey (NGS) using standard optical surveys in 2015 and 2018. The uncertainties of the latter survey were 0.3 and 0.7 mm in the horizontal and vertical components of the baseline, respectively. We applied corrections to the measured positions for the varying thermal deformation of the antennas on the diferent days of the VLBI and survey measurements, which can amount to 1 mm, bringing all results to a common reference temperature. The diference between the VLBI and survey results are 0.2±0.4 mm, −1.3±0.4 mm, and 0.8±0.8 mm in the East, North, and Up topocentric components, respectively. We also estimate that the Up component of the baseline may sufer from systematic errors due to gravitational deformation and uncalibrated instrumental delay variations at the 20 m antenna that may reach ±10 and −2 mm, respectively, resulting in an accuracy uncertainty on the order of 10 mm for the relative heights of the antennas. Furthermore, possible tilting of the 12 m antenna increases the uncertainties in the diferences in the horizontal components to 1.0 mm. These results bring into focus the importance of (1) correcting to a common reference temperature the measurements of the reference points of all geodetic instruments within a site, (2) obtaining measurements of the gravitational deformation of all antennas, and (3) monitoring local motions of the geodetic instruments. These results have signifcant implications for the accuracy of global reference frames that require accurate local ties between geodetic instruments, such as the International Terrestrial Reference Frame (ITRF).
Keywords: Geodetic VLBI · Reference Frames · ITRF · Global Geodetic Observing System · Core sites · Local vector ties · Phase delay VLBI · Antenna thermal deformation
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Nunziata F., Li X., Marino A., Shao W., Portabella M., Yang X., Buono A. (2021)
Remote Sensing, 13, 3126 DOI: 10.3390/rs13163126. (BibTeX: nunziata.etal.2021)
Abstract: See
In this project report, the main outcomes relevant to the Sino-European Dragon-4 cooperation project ID 32235 “Microwave satellite measurements for coastal area and extreme weather monitoring” are reported. The project aimed at strengthening the Sino-European research cooperation in the exploitation of European Space Agency, Chinese and third-party mission Earth Observation (EO) microwave satellite data. The latter were exploited to perform an effective monitoring of coastal areas, even under extreme weather conditions. An integrated multifrequency/polarization approach based on complementary microwave sensors (e.g., Synthetic Aperture Radar, scatterometer, radiometer), together with ancillary information coming from independent sources, i.e., optical imagery, numerical simulations and ground measurements, was designed. In this framework, several tasks were addressed including marine target detection, sea pollution, sea surface wind estimation and coastline extraction/classification. The main outcomes are both theoretical (i.e., new models and algorithms were developed) and applicative (i.e., user-friendly maps were provided to the end-user community of coastal area management according to smart processing of remotely sensed data). The scientific relevance consists in the development of new algorithms, the effectiveness and robustness of which were verified on actual microwave measurements, and the improvement of existing methodologies to deal with challenging test case
Keywords: microwave satellites; multipolarization; multifrequency; oceans; coastal areas; coastline; sea wind field; ocean pollution; ships
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Olivé A., Pelegrí J.L., Machín F.J., Vallès-Casanova I. (2021)
Journal of Geophysical Research: Oceans, 126, 7 DOI: 10.1029/2020JC017025. (BibTeX: olive.etal.2021)
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Southern Ocean waters enter the South Atlantic Ocean through the Scotia Sea along pathways constrained by the bathymetry of the northern Scotia Sea passages. We use the Argo profiling-float data set to calculate the water transports in and out of the region, focusing on the water balances down to the deepest isoneutral sampled in all passages (γn = 28.0 kg m−3, located between about 500 and 2,000 m in the Drake Passage and even shallower in the Northern Passages). Down to this reference level, the water inflow through the Drake Passage is 140.8 ± 7.4 Sv and the water outflow through the deeper portions of the Northern Passages is 115.9 ± 8.3 Sv, implying a leakage of about 25 ± 11.1 Sv over topography shallower than 1,000 m. Below the reference isoneutral and down to 2,000 m, an additional 23.4 Sv enter through the Drake Passage; when added to reported inputs of about 20 Sv through the South Scotia Ridge, this accounts well for the observed 43.4 Sv outflow–from 28.0 kg m−3 to 2,000 m–through the Northern Passages. Relative to the 2,000 m reference level, the mean barotropic contribution always represents over half the total transports. We also observe substantial seasonal and moderate interannual variations in the water transports and composition (peak differences occur seasonally in the Drake Passage, with a range of 111–174 Sv), associated with changes in water exchange across the frontal systems. Two independent measures set the water mean-residence time in the Scotia Sea at about 6–8 months.
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Olivé A., Vinha B., Machín F., Zerbetto F., Bakalis E., Fraile-Nuez E. (2021)
Geosciences, 11, 374 DOI: 10.3390/geosciences11090374. (BibTeX: olive.etal.2021a)
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Temperature and conductivity fluctuations caused by the hydrothermal emissions released during the degasification stage of the Tagoro submarine volcano (Canary Islands, Spain) have been analysed as a robust proxy for characterising and forecasting the activity of the system. A total of 21 conductivity-temperature-depth time series were gathered on a regular high-resolution grid over the main crater of Tagoro volcano. Temperature and conductivity time series, as manifestations of stochastic events, were investigated in terms of variance and analysed by the Generalised Moments Method (GMM). GMM provides the statistical moments, the structure functions of a process whose shape is an indicator of the underlying stochastic mechanisms and the state of activity of the submarine volcano. Our findings confirm an active hydrothermal process in the submarine volcano with a sub-normal behaviour resulting from anti-persistent fluctuations in time. Its hydrothermal emissions are classified as multifractal processes whose structure functions present a crossover between two time scales. In the shorter time scale, findings point to the multiplicative action of two random processes, hydrothermal vents, which carries those fluctuations driving the circulation over the crater, and the overlying aquatic environment. Given that both temperature and conductivity fluctuations are nonstationary, Tagoro submarine volcano can be characterised as an open system exchanging energy to its surrounding
Keywords: Tagoro submarine volcano; time series; volcanic activity; generalised moments method; stochastic processes
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Olmedo E., González-Haro C., Hoareau N., Umbert M., González-Gambau V., Martínez J., Gabarró C., Turiel A. (2021)
Earth System Science Data, 13, 857-888. DOI: 10.5194/essd-13-857-2021. (BibTeX: olmedo.etal.2021)
Abstract: See
After more than 10 years in orbit, the Soil Moisture and Ocean Salinity (SMOS) European mis-sion is still a unique, high-quality instrument for providing soil moisture over land and sea surface salinity(SSS) over the oceans. At the Barcelona Expert Center (BEC), a new reprocessing of 9 years (2011–2019)of global SMOS SSS maps has been generated. This work presents the algorithms used in the generation ofBEC global SMOS SSS product v2.0, as well as an extensive quality assessment. Three SMOS SSS fields aredistributed: a high-resolution level-3 product (with DOI https://doi.org/10.20350/digitalCSIC/12601, Olmedoet al., 2020a) consisting of binned SSS in 9 d maps at 0.25◦×0.25◦; low-resolution level-3 SSS computedfrom the binned salinity by applying a smoothing spatial window of 50 km radius; and level-4 SSS (with DOIhttps://doi.org/10.20350/digitalCSIC/12600, Olmedo et al., 2020b) consisting of daily 0.05◦×0.05◦maps thatare computed by multifractal fusion with sea surface temperature maps. For the validation of BEC SSS products,we have applied a battery of tests aimed at the assessment of quality of the products both in value and in structure.First, we have compared BEC SSS products with near-to-surface salinity measurements provided by Argo floats.Secondly, we have assessed the geophysical consistency of the products characterized by singularity analysis,and the effective spatial resolutions are also estimated by means of power density spectra and singularity densityspectra. Finally, we have calculated full maps of SSS errors by using correlated triple collocation. We have com-pared the performance of the BEC SMOS product with other satellite SSS and reanalysis products. The mainoutcomes of this quality assessment are as follows. (i) The bias between BEC SMOS and Argo salinity is lowerthan 0.02 psu at a global scale, while the standard deviation of their difference is lower than 0.34 and 0.27 psu forthe high- and low-resolution level-3 fields (respectively) and 0.24 psu for the level-4 salinity. (ii) The effectivespatial resolution is around 40 km for all SSS products and regions. (iii) The results from triple collocation showthe BEC SMOS level-4 product as the product with the lowest estimated salinity error in most of the globalocean and the BEC SMOS high-resolution level-3 as the one with the lowest estimated salinity error in regionsstrongly affected by rainfall and continental freshwater discharge
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Orué-Echevarría D., Pelegrí J.L., Alonso-González I.J., Benítez-Barrios V.M., Emelianov M., García-Olivares A., Gasser-Rubinat M., De La Fuente P., Herrero C., Isern-Fontanet J., Masdeu-Navarro M., Peña-Izquierdo J., Piola A.R., Ramírez-Garrido S., Rosell-Fieschi M., Salvador J., Saraceno M., Valla D., Vallès-Casanova I., Vidal M. (2021)
Deep-Sea Research. Part I: Oceanographic Research Papers, 172, 103533 DOI: 10.1016/j.dsr.2021.103533. (BibTeX: orueechevarria.etal.2021)
Abstract: See
The encountering of the subtropical Brazil Current (BC) and the subantarctic Malvinas Current (MC) along the western margin of the Argentine Basin forms the Brazil-Malvinas Confluence (BMC), one of the most intense open-ocean fronts in the world ocean and a site for the formation of intermediate water masses. Here, we provide a comprehensive description of the BMC based on physical and biogeochemical data – hydrographic stations, profiling floats and subsurface drifters – gathered in March 2015. We use these data in order to characterize the impinging and outflowing currents and to describe the cross- and along-frontal thermohaline structure. In addition, we compare the in-situ measurements with both climatological data and the Mercator Ocean eddy-resolving reanalysis. The hydrographic sections illustrate the contrasting properties between the two western boundary currents: warm, salty, nutrient- and oxygen-poor oligotrophic subtropical waters carried southward by the BC and the cold, fresh, oxygen- and nutrient-rich subantarctic waters carried northward by the MC. The frontal system is also characterized by the presence of thermohaline intrusions, with the cross-frontal gradients and along-front velocities sharpening as the colliding currents shape the frontal system. We also observe brackish waters spreading on top of the frontal jet as a result of both the confluence dynamics and off-shelf advection favored by north-easterly winds. These low-salinity waters are positively correlated with surface ageostrophic speeds over the frontal jet. The cruise data illustrates the high regional and mesoscale variability as compared with climatological conditions, and further document the submesoscale subsurface complexity, which is not properly captured by available operational models
Keywords: Brazil-Malvinas Confluence Ocean currents River plume Ageostrophic velocity Lagrangian description Hydrographic data
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Pontes M., Salvador X., Parera A., Álvarez G., Ballesteros M. (2021)
Monografies de la Institució Catalana d’Història Natural, 3 DOI: 10.2436/20.1502.04.03. (BibTeX: pontes.etal.2021)
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The Mediterranean Sea is a hotspot for biodiversity and endemic species (between 4 % and 18 % of known species are endemic, depending on the group), but this environment, favourable for native species, also favours exotic species. To ascertain how biodiversity has been impacted by intense human activity, we surveyed the marine life in the Barcelona Forum bathing area, an artificial beach receiving large amounts of waste from neighbouring areas and effluent from the nearby sewage treatment plant. Despite such eutrophic influences and the replacement of natural substrates with artificial ones, a surprisingly rich marine biota of 514 species was found. The groups with most species identified were molluscs (176), fish (88), crustaceans (65) and algae (50). These results include 15 exotic species that have settled in this ecosystem, such as the sea hare Bursatella leachii and the polychaete Branchiomma luctuosum, and some iconic natives such as the Fan mussel (Pinna nobilis) and the Dusky grouper (Epinephelus marginatus). Urban litter was sampled and no significant deleterious effects on the biota were detected. The site acts as a refuge for fish and is conducive to the settlement of encrusting species that colonize new substrates.
Keywords: Marinas, Biodiversity, alien species, marine litter, Barcelona Forum
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Renault L., Arsouze T., Ballabrera-Poy J. (2021)
Journal of Geophysical Research: Oceans, 126, 1 DOI: 10.1029/2020JC016664. (BibTeX: renault.etal.2021)
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The ocean Current FeedBack to the atmosphere (CFB) has been shown to be an unambiguous physical process to achieve proper equilibrium in the Ocean. However, its effects on the Western Mediterranean Sea (WMS) are not known. In this study, eddy-rich coupled ocean-atmosphere simulations are carried out for the WMS to assess the extent to which CFB alters the WMS circulation and to characterize the low-level wind and surface stress responses to CFB. By generating conduits of energy from oceanic currents to the atmosphere, CFB slows the mean circulation by about 10% and acts as an oceanic eddy killer, reducing the mesoscale activity by 25% and attenuating the intensity of their intermittency. It also alters the mean barotropic vorticity balance of the WMS Gyre, reducing the role of wind stress curl, nonlinear torque, and bottom pressure torque. By reducing the eddy-mean flow interaction, CFB has a large influence on the properties of the Algerian Current, reducing the presence of standing eddies near Sardinia and improving the realism of the circulation. It also modifies the Alboran Gyres formation and the Northern Current retroflection. Finally, coupling coefficients from the coupled simulations are estimated and are consistent with those for other regions. The CFB coupling coefficients can be used to parameterize the CFB in a forced ocean model. Overall, our results show that, as for other regions, the CFB is another physical mechanism to be considered for the representation of the WMS circulation.
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Rieger N., Corral A., Olmedo E., Turiel A. (2021)
Journal of Climate, 34, 24, 9861–9878. DOI: 10.1175/JCLI-D-21-0244.1. (BibTeX: rieger.etal.2021)
Abstract: See
A proper description of ocean–atmosphere interactions is key for a correct understanding of climate evolution. The interplay among the different variables acting over the climate is complex, often leading to correlations across long spatial distances (teleconnections). On some occasions, those teleconnections occur with quite significant temporal shifts that are fundamental for the understanding of the underlying phenomena but that are poorly captured by standard methods. Applying orthogonal decomposition such as maximum covariance analysis (MCA) to geophysical datasets allows us to extract common dominant patterns between two different variables, but generally suffers from (i) the nonphysical orthogonal constraint as well as (ii) the consideration of simple correlations, whereby temporally offset signals are not detected. Here we propose an extension, complex rotated MCA, to address both limitations. We transform our signals using the Hilbert transform and perform the orthogonal decomposition in complex space, allowing us to correctly correlate outof-phase signals. Subsequent varimax rotation removes the orthogonal constraints, leading to more physically meaningful modes of geophysical variability. As an example, we have employed this method on sea surface temperature and continental precipitation; our method successfully captures the temporal and spatial interactions between these two variables for (i) the seasonal cycle, (ii) canonical ENSO, (iii) the global warming trend, (iv) the Pacific decadal oscillation, (v) ENSO Modoki, and finally (vi) the Atlantic meridional mode. The complex rotated modes of MCA provide information on the regional amplitude and, under certain conditions, the regional time lag between changes on ocean temperature and land precipitation.
Keywords: Atmosphere-ocean interaction, Teleconnections, Precipitation, Sea surface temperature, Empirical orthogonal functions, Pattern detection, Principal components analysis, Dimensionality reduction
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Rodero C., Olmedo E., Bardaji R., Piera J. (2021)
Sensors, 21, 5537 DOI: 10.3390/s21165537. (BibTeX: rodero.etal.2021)
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Measuring the diffuse attenuation coefficient (Kd ) allows for monitoring the water body’s environmental status. This parameter is of particular interest in water quality monitoring programs because it quantifies the presence of light and the euphotic zone’s depth. Citizen scientists can meaningfully contribute by monitoring water quality, complementing traditional methods by reducing monitoring costs and significantly improving data coverage, empowering and supporting decisionmaking. However, the quality of the acquisition of in situ underwater irradiance measurements has some limitations, especially in areas where stratification phenomena occur in the first meters of depth. This vertical layering introduces a gradient of properties in the vertical direction, affecting the associated Kd . To detect and characterize these variations of Kd in the water column, it needs a system of optical sensors, ideally placed in a range of a few cm, improving the low vertical accuracy. Despite that, the problem of self-shading on the instrumentation becomes critical. Here, we introduce a new concept that aims to improve the vertical accuracy of the irradiance measurements: the underwater annular irradiance (Ea). This new concept consists of measuring the irradiance in an annular-shaped distribution. We first compute the optimal annular angle that avoids self-shading and maximizes the light captured by the sensors. Second, we use different scenarios of water types, solar zenith angle, and cloud coverage to assess the robustness of the corresponding diffuse attenuation coefficient, Ka. Finally, we derive empirical functions for computing Kd from Ka. This new concept opens the possibility to a new generation of optical sensors in an annular-shaped distribution which is expected to (a) increase the vertical resolution of the irradiance measurements and (b) be easy to deploy and maintain and thus to be more suitable for citizen scientists.
Keywords: annular irradiance; water quality; marine citizen science; diffuse attenuation coefficient; oceanography; light
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Schild K.M., Sutherland D.A., Elosegui P., Duncan D. (2021)
Geophysical Research Letters, 48, 3 DOI: 10.1029/2020GL089765. (BibTeX: schild.etal.2021b)
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Increasing freshwater input to the subpolar North Atlantic through iceberg melting can influence fjord-scale to basin-scale ocean circulation. However, the magnitude, timing, and distribution of this freshwater have been challenging to quantify due to minimal direct observations of subsurface iceberg geometry and melt rates. Here we present novel in situ methods capturing iceberg change at high-temporal and -spatial resolution using four highprecision GPS units deployed on two large icebergs (>500 m length). In combination with measurements of surface and subsurface geometry, we calculate iceberg melt rates between 0.10–0.27 m/d over the 9-day survey. These melt rates are lower than those proposed in previous studies, likely due to using individual subsurface iceberg geometries in calculations. In combining these new measurements of iceberg geometry and melt rate with the broad spatial coverage of remote sensing, we can better predict the impact of increasing freshwater injection from the Greenland Ice Sheet.
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Sotillo M.G., Campuzano F., Guihou K., Lorente P., Olmedo E., Matulka A., Santos F., Amo-Baladrón M.A., Novellino A. (2021)
Journal of Marine Science and Engineering, 9, 4, 401. DOI: 10.3390/jmse9040401. (BibTeX: sotillo.etal.2021)
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River freshwater contribution in the European Atlantic margin and its influence on the sea salinity field are analyzed. The impacts of using a new river discharge database as part of the freshwater forcing in a regional ocean model are assessed. Ocean model scenarios, based on the CMEMS (Copernicus Marine Environment Monitoring Service) operational IBI-MFC (Iberia Biscay Ireland Monitoring Forecasting Centre) model set‑up, are run to test different (observed, modeled and climatological) river and coastal freshwater forcing configurations throughout 2018. The modelled salinity fields are validated, using as a reference all known available in-situ observational data sources. The IBI model application is proven to adequately simulate the regional salinity, and the scenarios showcase the effects of varying imposed river outflows. Some model improvement is achieved using the new forcing (i.e., better capture of salinity variability and more realistic simulation of baroclinic frontal structures linked to coastal and river freshwater buoyancy plumes). Major impacts are identified in areas with bigger river discharges (i.e., the French shelf or the northwestern Iberian coast). Instead, the Portuguese shelf or the Gulf of Cadiz are less impacted by changes in the imposed river inflows, and other dynamical factors in these areas play a major role in the configuration of the regional salinity.
Keywords: river freshwater discharges; operational ocean models; sea surface salinity field, IBI region, LAMBDA river database, IBI model validation, model sensitivity tests
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Umbert M., Gabarro C., Olmedo E., Gonçalves-Araujo R., Guimbard S., Martínez J. (2021)
Remote Sensing, 13, 3828 DOI: 10.3390/rs13193828. (BibTeX: umbert.etal.2021)
Abstract: See
The overall volume of freshwater entering the Arctic Ocean has been growing as glaciers melt and river runoff increases. Since 1980, a 20% increase in river runoff has been observed in the Arctic system. As the discharges of the Ob, Yenisei, and Lena rivers are an important source of freshwater in the Kara and Laptev Seas, an increase in river discharge might have a significant impact on the upper ocean circulation. The fresh river water mixes with ocean water and forms a large freshened surface layer (FSL), which carries high loads of dissolved organic matter and suspended matter into the Arctic Ocean. Optically active material (e.g., phytoplankton and detrital matter) are spread out into plumes, which are evident in satellite data. Russian river signatures in the Kara and Laptev Seas are also evident in recent SMOS Sea Surface Salinity (SSS) Arctic products. In this study, we compare the new Arctic+ SSS products, produced at the Barcelona Expert Center, with the Ocean Color absorption coefficient of colored detrital matter (CDM) in the Kara and Laptev Seas for the period 2011–2019. The SSS and CDM are found to be strongly negatively correlated in the regions of freshwater influence, with regression coefficients between −0.72 and −0.91 in the studied period. Exploiting this linear correlation, we estimate the SSS back to 1998 using two techniques: one assuming that the relationship between the CDM and SSS varies regionally in the river-influenced areas, and another assuming that it does not. We use the 22-year time-series of reconstructed SSS to estimate the interannual variability of the extension of the FSL in the Kara and Laptev Seas as well as their freshwater content. For the Kara and Laptev Seas, we use 32 and 28 psu as reference salinities, and 26 and 24 psu isohalines as FSL boundaries, respectively. The average FSL extension in the Kara Sea is 2089–2611 km2, with a typical freshwater content of 11.84–14.02 km3. The Laptev Sea has a slightly higher mean FSL extension of 2320–2686 km2 and a freshwater content of 10.15–12.44 km3. The yearly mean freshwater content and extension of the FSL, computed from SMOS SSS and Optical data, is (as expected) found to co-vary with in situ measurements of river discharge from the Arctic Great Rivers Observatory database, demonstrating the potential of SMOS SSS to better monitor the river discharge changes in Eurasia and to understand the Arctic freshwater system during the ice-free season
Keywords: arctic; freshwater fluxes; remote sensing; physical oceanography; sea surface salinity; ocean color; data fusion
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Vargas-Yáñez M., Juza M., García-Martínez M.C., Moya F., Balbín R., Ballesteros E., Muñoz M., Tel E., Pascual J., Vélez-Belchi P., Salat J. (2021)
Frontiers in Marine Science, 8, 640535 DOI: 10.3389/fmars.2021.640535. (BibTeX: vargasyanez.etal.2021)
Abstract: See
The analysis of a 24-year time series of Conductivity-Temperature-Depth (CTD) casts collected in the Balearic Channels (1996–2019) has allowed detecting and quantifying long-term changes in water mass properties in the Western Mediterranean. For the complete period, the intermediate waters have experienced warming and salting at rates of 1.4°C/100yr and 0.3–0.6/100yr for the Western Intermediate Water, and 1°C/100yr and 0.3–0.4/100yr for the Levantine Intermediate Water. The density of these two water masses has not changed. The deep waters, defined as those denser than 29.1 kg/m3, showed positive trends in temperature, salinity, and density (0.8°C/100yr, 0.2/100yr, and 0.02 kg.m–3/100yr, respectively). The high temporal variability of the upper layer makes the detection of long-term changes more difficult. Nevertheless, combining CTD data with temperature data from the oceanographic station at L’Estartit and simulated data from the NCEP/NCAR reanalysis, it can be established that the Atlantic Water increased its temperature at a rate of 2.1–2.8°C/100yr and likely its salinity at a rate of 0.6/100yr. The water column absorbed heat at a rate equivalent to 1–1.2 W/m2. All these trends are much higher than those reported in previous works (more than double in some cases). The warming of the water column produced an increase in the thermosteric component of sea level. However, this increase was compensated by the decrease in the halosteric component. Besides these changes, other alterations related to the Western Mediterranean Transition have been observed over shorter periods. The temperature and salinity of the intermediate waters increased before the winter of 2004/2005 and then the temperature and salinity of the deep waters increased dramatically in 2005. The density of the deep water reached values unprecedented before 2005. Deep and intermediate waters were uplifted by the presence of such dense deep waters. The arrival of warmer and saltier intermediate waters from the Eastern Mediterranean is also observed, mainly after 2010.
Keywords: water mass properties, linear trends, climate change, Balearic Channels, Western Mediterranean Transition
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Viúdez A. (2021)
Physics of Fluids, 33, 054103 DOI: 10.1063/5.0048128. (BibTeX: viudez.2021)
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Solutions of robust axisymmetric neutral vortices, that is, vortices with zero amount of vorticity, in two-dimensional (2D) Euler flows with distributed vorticity are obtained. These solutions are particular linear combinations of vorticity layer-modes, which are defined as truncated, shifted, and conveniently normalized Bessel functions of order-0, each one occupying a circular layer defined by a zero of the Bessel function of order-1. It is found that some linear combinations of these modes have a vanishing net amount of vorticity and remain axysimmetrically robust to small amplitude vorticity perturbations. These neutral vortices are quiescent and remain steady in the presence of similar vortices. Other linear combinations of these vorticity layer-modes give rise to unstable neutral vortices that develop into neutral tripoles, pentapoles, etc. It is found numerically that the robustness of these neutral vortices is related to the spiralization and axisymmetrization of the initially growing vorticity disturbances as are advected by a convex azimuthal velocity distribution beyond its first inflection point. In particular, it is found that two co-rotating neutral tripoles attract due to the phase synchronization of their respective octupolar potential flow but repel when touched due to vorticity exchange. This interaction mechanism makes possible equilibrium states for sets of a large number of neutral tripoles. Other linear combinations of these vorticity layer-modes give rise to non-neutral shielded vortices which interact and may form coherent vortex structures as pairs of co-rotating shielded vortices sharing their outermost vorticity layer or counter-rotating shielded vortices translating with uniform speed as vortex dipoles
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Wagenknecht K., Woods T., García-Sanz F., Gold M., Bowser A., Rüfenacht S., Ceccaroni L., Piera J. (2021)
Data Intelligence, 3, 1, 136-149. DOI: 10.1162/dint_a_00085. (BibTeX: wagenknecht.etal.2021a)
Abstract: See
Citizen Science (CS) is a prominent field of application for Open Science (OS), and the two have strong synergies, such as: advocating for the data and metadata generated through science to be made publicly available [1]; supporting more equitable collaboration between different types of scientists and citizens; and facilitating knowledge transfer to a wider range of audiences [2]. While primarily targeted at CS, the EU-Citizen. Science platform can also support OS. One of its key functions is to act as a knowledge hub to aggregate, disseminate and promote experience and know-how; for example, by profiling CS projects and collecting tools, resources and training materials relevant to both fields. To do this, the platform has developed an information architecture that incorporates the public participation in scientific research (PPSR)—Common Conceptual Model①. This model consists of the Project Metadata Model, the Dataset Metadata Model and the Observation Data Model, which were specifically developed for CS initiatives. By implementing these, the platform will strengthen the interoperating arrangements that exist between other, similar platforms (e.g., BioCollect and SciStarter) to ensure that CS and OS continue to grow globally in terms of participants, impact and fields of application.
Keywords: Citizen Science; Metadata; Open Science; Public participation in scientific research (PPSR)
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Yahia H., Schneider N., Bontemps S., Bonne L., Attuel G., Dib S., Ossenkopf-Okada V., Turiel A., Zebadua A., Elia D., Kumar Maji S., G. Schmitt and J.F. Robitaille F. (2021)
Astronomy and Astrophysics, 649, A33 DOI: 10.1051/0004-6361/202039874. (BibTeX: yahia.etal.2021)
Abstract: See
Observations of the interstellar medium (ISM) show a complex density and velocity structure, which is in part attributed to turbulence. Consequently, the multifractal formalism should be applied to observation maps of the ISM in order to characterize its turbulent and multiplicative cascade properties. However, the multifractal formalism, even in its more advanced and recent canonical versions, requires a large number of realizations of the system, which usually cannot be obtained in astronomy. We present a self-contained introduction to the multifractal formalism in a “microcanonical” version, which allows us, for the first time, to compute precise turbulence characteristic parameters from a single observational map without the need for averages in a grand ensemble of statistical observables (e.g., a temporal sequence of images). We compute the singularity exponents and the singularity spectrum for both observations and magnetohydrodynamic simulations, which include key parameters to describe turbulence in the ISM. For the observations we focus on the 250 μm Herschel map of the Musca filament. Scaling properties are investigated using spatial 2D structure functions, and we apply a two-point log-correlation magnitude analysis over various lines of the spatial observation, which is known to be directly related to the existence of a multiplicative cascade under precise conditions. It reveals a clear signature of a multiplicative cascade in Musca with an inertial range from 0.05–0.65 pc. We show that the proposed microcanonical approach provides singularity spectra that are truly scale invariant, as required to validate any method used to analyze multifractality. The obtained singularity spectrum of Musca, which is sufficiently precise for the first time, is clearly not as symmetric as usually observed in log-normal behavior. We claim that the singularity spectrum of the ISM toward Musca features a more log-Poisson shape. Since log-Poisson behavior is claimed to exist when dissipation is stronger for rare events in turbulent flows, in contrast to more homogeneous (in volume and time) dissipation events, we suggest that this deviation from log-normality could trace enhanced dissipation in rare events at small scales, which may explain, or is at least consistent with, the dominant filamentary structure in Musca. Moreover, we find that subregions in Musca tend to show different multifractal properties: While a few regions can be described by a log-normal model, other regions have singularity spectra better fitted by a log-Poisson model. This strongly suggests that different types of dynamics exist inside the Musca cloud. We note that this deviation from log-normality and these differences between subregions appear only after reducing noise features, using a sparse edge-aware algorithm, which have the tendency to “log-normalize” an observational map. Implications for the star formation process are discussed. Our study establishes fundamental tools that will be applied to other galactic clouds and simulations in forthcoming studies.
Keywords: ISM: structure / ISM: individual objects: Musca / turbulence / ISM: clouds / magnetohydrodynamics (MHD)