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Observing the Flow of Ocean Currents and Circulation Using Remote Sensing

A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Ocean Remote Sensing".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 28897

Special Issue Editors

Senior scientist, National Institute of Oceanography and Applied Geophysics - OGS, Borgo Grotta Gigante 42/c, 34010 Sgonico (Trieste), Italy
Interests: long-term variations of the ocean circulation; semi-enclosed seas and Mediterranean; water exchange between adjacent basins; coastal basins and lagoons
Scientist, National Institute of Oceanography and Applied Geophysics – OGS, Borgo Grotta Gigante 42/c, 34010 Sgonico (Trieste), Italy
Interests: ocean circulation; mesoscale and sub-basin scale eddies; currents and water mass properties in semi-enclosed seas; remote sensing (satellites) and autonomous measurement instruments (drifter and floats)
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Remote sensing techniques, both satellite and land-based, are powerful tools for ocean monitoring on a global, regional, and even local scale. Offering much higher temporal and spatial resolution compared to in situ methods, remote sensing has become a particularly important component in studies of ocean circulation. Over the last decade, the monitoring of ocean surface currents has been attracting greater interest not only for the better understanding the complex ocean–atmosphere–biosphere interactions, but also for a wide range of applications (ship routing, search and rescue, pollution monitoring, weather forecasting, etc.)

However, remotely sensed data can only provide the complete picture of the circulation of the ocean if combined with in situ measurements (moorings, floats, gliders, oceanographic cruises) that give the vertical distribution of ocean physical and biogeochemical properties. The spatial resolution of remotely sensed data ranges from a kilometer to a meter and, thus, we can resolve all the spatial spectrum of phenomena in the ocean from the large basin-scale to the small submesoscale features. Finally, assimilation of both in situ and remotely sensed data into numerical models enables us to interpolate oceanographic fields in three dimensions. This Special Issue calls for the submission of manuscripts dealing with the remotely sensed data used for the interpretation and understanding of oceanographic processes and circulation features. Interdisciplinary studies are very much encouraged.

Dr. Miroslav Gačić
Dr. Milena Menna
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • ocean currents
  • ocean monitoring
  • physical and biogeochemical properties
  • ocean vertical structure
  • remote sensing applications (biogeochemical properties, fisheries, ecology)
  • mesoscale and sub-mesoscale eddies

Published Papers (11 papers)

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24 pages, 8840 KiB  
Article
Climatic, Decadal, and Interannual Variability in the Upper Layer of the Mediterranean Sea Using Remotely Sensed and In-Situ Data
by Milena Menna, Miroslav Gačić, Riccardo Martellucci, Giulio Notarstefano, Giusy Fedele, Elena Mauri, Riccardo Gerin and Pierre-Marie Poulain
Remote Sens. 2022, 14(6), 1322; https://doi.org/10.3390/rs14061322 - 09 Mar 2022
Cited by 18 | Viewed by 2894
Abstract
The Mediterranean Sea is considered a hot spot of global warming because it has been changing faster than the global ocean, creating a strong impact on the marine environment. Recent studies agree on the increase in the sea level, in the sea surface [...] Read more.
The Mediterranean Sea is considered a hot spot of global warming because it has been changing faster than the global ocean, creating a strong impact on the marine environment. Recent studies agree on the increase in the sea level, in the sea surface temperature, and in the sea surface salinity in the Mediterranean Sea over the last two decades. In this research, the possible interconnection between these and other parameters that contribute to the regulatory effect of the sea on the climate are identified and discussed. Spatio-temporal variability of four oceanographic and air–sea interaction parameters (sea-level, sea surface temperature, sea surface salinity, and freshwater flux) are estimated over the last 27 years by performing the empirical orthogonal function analysis. Climatic trends, and interannual and decadal variability of the different datasets are delineated and described in the whole Mediterranean and in its sub-basins. On the climatic scale, the Mediterranean and its sub-basins behave in a coherent way, showing the seal level, temperature, salinity, and freshwater flux rise. On the interannual scale, the temporal evolution of the sea level and sea surface temperature are highly correlated, whereas freshwater flux affects the variability of sea level, temperature, and the salinity field mainly in the Western and Central Mediterranean. The decadal signal associated with the Northern Ionian Gyre circulation reversals is clearly identified in three of the four parameters considered, with different intensities and geographical extents. This signal also affects the intermediate layer of the Eastern Mediterranean, from where it is advected to the other sub-basins. Decadal signal not associated with the Northern Ionian Gyre reversals is strongly related to the variability of main sub-basin scale local structures. Full article
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26 pages, 118357 KiB  
Article
Drifting Speed of Lagrangian Fronts and Oil Spill Dispersal at the Ocean Surface
by Gina Fifani, Alberto Baudena, Milad Fakhri, Georges Baaklini, Yannice Faugère, Rosemary Morrow, Laurent Mortier and Francesco d’Ovidio
Remote Sens. 2021, 13(22), 4499; https://doi.org/10.3390/rs13224499 - 09 Nov 2021
Cited by 7 | Viewed by 2800
Abstract
Due to its dire impacts on marine life, public health, and socio-economic services, oil spills require an immediate response. Effective action starts with good knowledge of the ocean dynamics and circulation, from which Lagrangian methods derive key information on the dispersal pathways present [...] Read more.
Due to its dire impacts on marine life, public health, and socio-economic services, oil spills require an immediate response. Effective action starts with good knowledge of the ocean dynamics and circulation, from which Lagrangian methods derive key information on the dispersal pathways present in the contaminated region. However, precise assessments of the capacity of Lagrangian methods in real contamination cases remain rare and limited to large slicks spanning several hundreds of km. Here we address this knowledge gap and consider two medium-scale (tens of km wide) events of oil in contrasting conditions: an offshore case (East China Sea, 2018) and a recent near-coastal one (East Mediterranean, 2021). Our comparison between oil slicks and Lagrangian diagnostics derived from near-real-time velocity fields shows that the calculation of Lagrangian fronts is, in general, more robust to errors in the velocity fields and more informative on the dispersion pathways than the direct advection of a numerical tracer. The inclusion of the effect of wind is also found to be essential, being capable of suddenly breaking Lagrangian transport barriers. Finally, we show that a usually neglected Lagrangian quantity, the Lyapunov vector, can be exploited to predict the front drifting speed, and in turn, its future location over a few days, on the basis of near-real-time information alone. These results may be of special relevance in the context of next-generation altimetry missions that are expected to provide highly resolved and precise near-real-time velocity fields for both open ocean and coastal regions. Full article
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18 pages, 3283 KiB  
Article
Connectivity Analysis Applied to Mesoscale Eddies in the Western Mediterranean Basin
by Yuri Cotroneo, Paolo Celentano, Giuseppe Aulicino, Angelo Perilli, Antonio Olita, Pierpaolo Falco, Roberto Sorgente, Alberto Ribotti, Giorgio Budillon, Giannetta Fusco and Federica Pessini
Remote Sens. 2021, 13(21), 4228; https://doi.org/10.3390/rs13214228 - 21 Oct 2021
Cited by 6 | Viewed by 2143
Abstract
The Western Mediterranean basin (WMED) is characterized by the presence of energetic and dynamic mesoscale cyclonic and anticyclonic eddies. They mainly originate along the Algerian and the Northern currents and have a large influence on the basin circulation. Eddies can last for months, [...] Read more.
The Western Mediterranean basin (WMED) is characterized by the presence of energetic and dynamic mesoscale cyclonic and anticyclonic eddies. They mainly originate along the Algerian and the Northern currents and have a large influence on the basin circulation. Eddies can last for months, with longer lifetimes associated with the anticyclones, which can move far from their areas of origin. As they partially isolate and transfer water masses, they also have an impact on water properties (physical, chemical and biological), pollutant’s dispersion and transport of eggs, larvae and planktonic organisms. In this study, a connectivity analysis method is applied to the anticyclonic eddies (AEs) identified by an automated hybrid detection and tracking algorithm south of 42°N in the WMED. The same methodology is also applied to the trajectories of Lagrangian surface drifters available in the study area. The purpose is to highlight the connections between different areas of the basin linked to eddy activities in addition to the connectivity due to the mean surface circulation. Drifter data analysis showed that all the WMED sub-basins are strongly interconnected, with the mean surface circulation allowing a shortcut connection among many areas of the basin. The connectivity analysis of the AEs tracks shows that although AEs are ubiquitous in the WMED, their connectivity is limited to well-defined regions, depending on their origin location. Three main regions: the south-western, the south-eastern and the northern parts of the basin are characterized by AEs recirculation, with sporadic export of eddies to the other WMED zones. Full article
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14 pages, 2939 KiB  
Article
High-Resolution Ocean Currents from Sea Surface Temperature Observations: The Catalan Sea (Western Mediterranean)
by Jordi Isern-Fontanet, Emilio García-Ladona, Cristina González-Haro, Antonio Turiel, Miquel Rosell-Fieschi, Joan B. Company and Antonio Padial
Remote Sens. 2021, 13(18), 3635; https://doi.org/10.3390/rs13183635 - 11 Sep 2021
Cited by 8 | Viewed by 2665
Abstract
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 [...] Read more.
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. Full article
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19 pages, 8951 KiB  
Article
Observations of Surface Currents and Tidal Variability Off of Northeastern Taiwan from Shore-Based High Frequency Radar
by Yu-Ru Chen, Jeffrey D. Paduan, Michael S. Cook, Laurence Zsu-Hsin Chuang and Yu-Jen Chung
Remote Sens. 2021, 13(17), 3438; https://doi.org/10.3390/rs13173438 - 30 Aug 2021
Cited by 4 | Viewed by 1747
Abstract
A network of high-frequency radars (HFRs) has been deployed around Taiwan. The wide-area data coverage is dedicated to revealing near real-time sea-surface current information. This paper investigates three primary objectives: (1) describing the seasonal current synoptic variability; (2) determining the influence of wind [...] Read more.
A network of high-frequency radars (HFRs) has been deployed around Taiwan. The wide-area data coverage is dedicated to revealing near real-time sea-surface current information. This paper investigates three primary objectives: (1) describing the seasonal current synoptic variability; (2) determining the influence of wind forcing; (3) describing the tidal current field pattern and variability. Sea surface currents derived from HFR data include both geostrophic components and wind-driven components. This study explored vector complex correlations between the HFR time series and wind, which was sufficient to identify high-frequency components, including an Ekman balance among the surface currents and wind. Regarding the characteristics of mesoscale events and the tidal field, a year-long high-resolution surface dataset was utilized to observe the current–eddy–tide interactions over four seasons. The harmonic analysis results derived from surface currents off of northeastern Taiwan during 2013 are presented. The results agree well with the tidal parameters estimated from tide-gauge station observations. The analysis shows that this region features a strong, mixed, mainly semidiurnal tide. Continued monitoring by a variety of sensors (e.g., satellite and HFR) would improve the understanding of the circulation in the region. Full article
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25 pages, 9736 KiB  
Article
On the Structure and Kinematics of an Algerian Eddy in the Southwestern Mediterranean Sea
by Pierre-Marie Poulain, Luca Centurioni, Tamay Özgökmen, Daniel Tarry, Ananda Pascual, Simon Ruiz, Elena Mauri, Milena Menna and Giulio Notarstefano
Remote Sens. 2021, 13(15), 3039; https://doi.org/10.3390/rs13153039 - 03 Aug 2021
Cited by 6 | Viewed by 2005
Abstract
An Algerian Eddy, anticyclonic vortex generated by the instability of the Algerian Current in the southwestern Mediterranean Sea, is studied using data provided by drifters (surface currents), Argo floats (temperature and salinity profiles), environmental satellites (absolute dynamic topography maps and ocean color images) [...] Read more.
An Algerian Eddy, anticyclonic vortex generated by the instability of the Algerian Current in the southwestern Mediterranean Sea, is studied using data provided by drifters (surface currents), Argo floats (temperature and salinity profiles), environmental satellites (absolute dynamic topography maps and ocean color images) and operational oceanography products. The eddy was generated in May 2018 and lasted as an isolated vortex until November 2018. Its morphology and kinematics are described in June–July 2018 when drifters were trapped in its core. During that period, the eddy was slowly moving to the NE (~2 km/day), with an overall diameter of about 200 km (slowly growing with time) and maximal surface swirl velocity of ~50 cm/s at a radius of ~50 km. Geostrophic currents derived from satellite altimetry data compare well with low-pass filtered drifter velocities, with only a slight overestimation, which is expected as its maximum vorticity corresponds to a small Rossby number of ~0.6. Satellite ocean color images and some drifters show that the eddy has an elliptical spiral structure. The looping tracks of the drifters trapped in the eddy were analyzed using two statistical methods: least-squares ellipse fitting and wavelet ridge analysis, revealing a typical eccentricity of about 0.5, a wide range of inclination and a rotation period between 3 and 10 days. Clusters of drifters on the northeastern limb of the eddy were also considered to estimate divergence and vorticity. The results indicate convergence (divergence) and downwelling (upwelling) at scales of 20–50 km near the northeastern (northwestern) edge of the eddy, in agreement with the quasi-geostrophic theory. Vertically, the eddy extends mostly down to 250 m depth, with a warm, low-salinity and low-density signature and with geostrophic currents near 50 cm/s in the top layer (down to ~80 m) reducing to less than 10 cm/s near 250 m. Near the surface, colder water is advected into it. Full article
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28 pages, 20495 KiB  
Article
Spreading of Lagrangian Particles in the Black Sea: A Comparison between Drifters and a High-Resolution Ocean Model
by Maher Bouzaiene, Milena Menna, Dalila Elhmaidi, Ahmad Fehmi Dilmahamod and Pierre-Marie Poulain
Remote Sens. 2021, 13(13), 2603; https://doi.org/10.3390/rs13132603 - 02 Jul 2021
Cited by 8 | Viewed by 2345
Abstract
The Lagrangian dispersion statistics of the Black Sea are estimated using satellite-tracked drifters, satellite altimeter data and a high-resolution ocean model. Comparison between the in-situ measurements and the model reveals good agreement in terms of the surface dispersion. The mean sub-basin coherent structures [...] Read more.
The Lagrangian dispersion statistics of the Black Sea are estimated using satellite-tracked drifters, satellite altimeter data and a high-resolution ocean model. Comparison between the in-situ measurements and the model reveals good agreement in terms of the surface dispersion. The mean sub-basin coherent structures and currents of the Black Sea are well reproduced by the model. Seasonal variability of the dispersion in the upper (15 m), intermediate (150 m) and deep (750 m) layers are discussed with a special focus of the role of sub-basin scale structures and currents on the turbulent dispersion regimes. In terms of the surface relative dispersion, the results show the presence of the three known turbulent exponential, Richardson and diffusive-like regimes. The non-local exponential regime is only detected by the model for scales <10 km, while the local Richardson regime occurs between 10 and 100 km in all cases due to the presence of an inverse energy cascade range, and the diffusive-like regime is well detected for the largest distance by drifters (100–300 km) in winter/spring. Regarding the surface absolute dispersion, it reflects the occurrence of both quasi-ballistic and random-walk regimes at small and large times, respectively, while the two anomalous hyperbolic (5/4) and elliptic (5/3) regimes, which are related to the topology of the Black Sea, are detected at intermediate times. At depth, the signatures of the relative and absolute dispersion regimes shown in the surface layer are still valid in most cases. The absolute dispersion is anisotropic; the zonal component grows faster than the meridional component in any scenario. Full article
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22 pages, 22419 KiB  
Article
Ocean Currents Reconstruction from a Combination of Altimeter and Ocean Colour Data: A Feasibility Study
by Daniele Ciani, Elodie Charles, Bruno Buongiorno Nardelli, Marie-Hélène Rio and Rosalia Santoleri
Remote Sens. 2021, 13(12), 2389; https://doi.org/10.3390/rs13122389 - 18 Jun 2021
Cited by 7 | Viewed by 2419
Abstract
Measuring the ocean surface currents at high spatio-temporal resolutions is crucial for scientific and socio-economic applications. Since the early 1990s, the synoptic and global-scale monitoring of the ocean surface currents has been provided by constellations of radar altimeters. By construction, altimeter constellations provide [...] Read more.
Measuring the ocean surface currents at high spatio-temporal resolutions is crucial for scientific and socio-economic applications. Since the early 1990s, the synoptic and global-scale monitoring of the ocean surface currents has been provided by constellations of radar altimeters. By construction, altimeter constellations provide only the geostrophic component of the marine surface currents. In addition, given the effective spatial-temporal resolution of the altimeter-derived products (O (100 km) and O (10 days), respectively), only the largest ocean mesoscale features can be resolved. In order to enhance the altimeter system capabilities, we propose a synergistic use of high resolution sea surface Chlorophyll observations (Chl) and altimeter-derived currents’ estimates. The study is focused on the Mediterranean Sea, where the most energetic signals are found at spatio-temporal scales up to 10 km and a few days. The proposed method allows for inferring the marine surface currents from the evolution of the Chl field, relying on altimeter-derived currents as a first-guess estimate. The feasibility of this approach is tested through an Observing System Simulation Experiment, starting from biogeochemical model outputs distributed by the European Copernicus Marine Service. Statistical analyses based on the 2017 daily data showed that our approach can improve the altimeter-derived currents accuracy up to 50%, also enhancing their effective spatial resolution up to 30 km. Moreover, the retrieved currents exhibit larger temporal variability than the altimeter estimates over annual to weekly timescales. Our method is mainly limited to areas/time periods where/when Chl gradients are larger and are modulated by the marine currents’ advection. Its application is thus more efficient when the surface Chl evolution is not dominated by the biological activity, mostly occurring in the mid-February to mid-March time window in the Mediterranean Sea. Preliminary tests on the method applicability to satellite-derived data are also presented and discussed. Full article
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25 pages, 3736 KiB  
Article
Temporal Variability of Oceanic Mesoscale Events in the Gulf of California
by Edgardo Basilio Farach-Espinoza, Juana López-Martínez, Ricardo García-Morales, Manuel Otilio Nevárez-Martínez, Daniel Bernardo Lluch-Cota and Sofia Ortega-García
Remote Sens. 2021, 13(9), 1774; https://doi.org/10.3390/rs13091774 - 02 May 2021
Cited by 8 | Viewed by 2804
Abstract
Oceanic mesoscale events such as eddies, coastal upwelling, filaments and fronts created by water mass intrusion present properties allowing them to concentrate, transport and disperse salt, nutrients and plankton, among other important constituents in the ocean. The use of satellite images enables the [...] Read more.
Oceanic mesoscale events such as eddies, coastal upwelling, filaments and fronts created by water mass intrusion present properties allowing them to concentrate, transport and disperse salt, nutrients and plankton, among other important constituents in the ocean. The use of satellite images enables the continuous monitoring of the ocean dynamics at different temporal and spatial scales, aiding the study of its variability. This study focuses on the identification of these mesoscale events in the Gulf of California (GC) by means of sea surface temperature (SST) and chlorophyll a (Chl a) fronts (edge) detection by processing 5-day satellite images from the 1998–2019 period. The annual occurrence or frequency and duration of each event was identified; the interannual variability was evaluated and underlying correlations with the Multivariate El Niño Index (MEI) and the Pacific Decadal Index (PDOI) were assessed via Principal Component Analysis. Most events showed a seasonal variability due to the seasonal behavior of forcing agents (i.e., Pacific Ocean and winds) that stimulate their formation or presence in the GC; seasonality was more evident in the northern region than in the southern region. The interannual variability of their frequency or duration was associated with strong and intense El Niño and La Niña conditions (positive or negative MEI values) together with positive or negative phases of the PDOI. The use of SST and Chl a satellite images with a 5-day temporal resolution allowed to better identify and quantify the annual frequency and duration of each mesoscale event. It allowed to detect a seasonal behavior of these events in the northern region, followed by the central region. The southern region, due to the interaction of different water masses with unique characteristics, exhibited a less evident seasonality in the frequency of eddies, and no apparent association between their interannual frequency and duration with the MEI and PDOI. Constantly monitoring these oceanic events and their variability will help in the understanding of how the different regions of this large marine ecosystem respond to these variations in the long term. Full article
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18 pages, 11226 KiB  
Article
Occurrence and Evolution of Mesoscale Thermodynamic Phenomena in the Northern Part of the East Sea (Japan Sea) Derived from Satellite Altimeter Data
by Taekyun Kim, Hyeong-Jun Jo and Jae-Hong Moon
Remote Sens. 2021, 13(6), 1071; https://doi.org/10.3390/rs13061071 - 11 Mar 2021
Cited by 5 | Viewed by 2032
Abstract
Based on satellite measurements and oceanic reanalysis data, it has been possible to investigate the spatiotemporal variability of the mesoscale phenomena in the northern part of the East Sea (NES) where direct observations of currents and hydrographical conditions are scarce. For the first [...] Read more.
Based on satellite measurements and oceanic reanalysis data, it has been possible to investigate the spatiotemporal variability of the mesoscale phenomena in the northern part of the East Sea (NES) where direct observations of currents and hydrographical conditions are scarce. For the first time, this study identifies the detailed spatiotemporal structure of the mesoscale features in the NES and the mechanism of its occurrence and evolution, which have important consequences on the distribution of the intermediate water masses in the East Sea. Here, we show that mesoscale thermodynamic phenomena in the northwestern region of the East Sea are characterized by a dipole structure associated with positive and negative sea surface height anomalies. These result in a strong thermal gradient between the seasonally non-persistent anomalies, which emerge and strengthen during late fall and early winter. In contrast to the previous finding of the relationship between winter monsoon winds and mesoscale features in the NES, we found that this relationship is crucial only to the emergence of the mesoscale phenomena. Consequently, we present a new perspective on the evolution mechanism of the mesoscale features in the NES. Of direct significance to the present study, thermohaline transport into the northwestern region of the East Sea regulates the strengthening and weakening of mesoscale features in the NES. Wind forcing may contribute to the emergence of the mesoscale features in the NES and then the intensification of the mesoscale activities is attributed to the intrusion of warm and fresh surface water advected from the southern part of the East Sea. Full article
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15 pages, 3751 KiB  
Technical Note
Coastal Current Intrusions from Satellite Altimetry
by Daniele Casella, Marco Meloni, Anne A. Petrenko, Andrea M. Doglioli and Jerome Bouffard
Remote Sens. 2020, 12(22), 3686; https://doi.org/10.3390/rs12223686 - 10 Nov 2020
Cited by 5 | Viewed by 2626
Abstract
The use of satellite-based data in coastal regions for the monitoring of fine-scale ocean dynamics, impacting marine ecosystems, is a difficult challenge. A random forest algorithm to detect slope current intrusions into the Gulf of Lion, Mediterranean Sea, has been developed using both [...] Read more.
The use of satellite-based data in coastal regions for the monitoring of fine-scale ocean dynamics, impacting marine ecosystems, is a difficult challenge. A random forest algorithm to detect slope current intrusions into the Gulf of Lion, Mediterranean Sea, has been developed using both improved coastal altimetry data and 10 year-long numerical simulations. The results have been compared to an independent dataset of in situ measurements from a bottom-moored Acoustic Doppler Current Profiler. The algorithm results are very promising: 93% of slope current intrusions have been correctly identified, and the number of false alarms is moderate. The dependence of the algorithm on several environmental factors is discussed in the paper. From the oceanographic point of view, our results confirm the strong impacts of horizontal winds in the dynamic of the intrusion events in the study area. Our methodology combining numerical modeling, in situ data and new machine-learning tools proves effective in improving the capabilities of ocean remote sensing in coastal areas. Full article
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