Optimal monitoring of the ocean surface by observing the transport crossroads

2021 ◽  
Author(s):  
Emilio Hernández-García ◽  
Alberto Baudena ◽  
Enrico Ser-Giacomi ◽  
Cristobal Lopez ◽  
Francesco d'Ovidio
Keyword(s):  
Time Window ◽  
Mesoscale Eddy ◽  
Surface Region ◽  
Ocean Surface ◽  
Tracer Transport ◽  
Optimal Monitoring ◽  
Larval Connectivity ◽  
Surface Circulation ◽  
Temporal Persistence ◽  
Surface Drifters

<p>In the context of tracer transport in the ocean, we introduce a quantity, the crossroadness [1], which allows identifying the optimal disposition of a set of locations in order to monitor a given ocean surface region. The optimization is performed so that these sites observe the largest amount of water coming from the region and, at the same time, monitor waters coming from separate parts of the ocean. These are key criteria when deploying a marine observing network. Considering surface circulation, crossroadness measures at any location the extent of the ocean surface which transits in its neighborhood in a given time window. When the analysis is performed backward in time, this method allows us to identify the major sources which feed a target region. The method is first applied to a minimalistic model of a mesoscale eddy field, and then to realistic satellite-derived ocean currents in the Kerguelen area. In this region, we identify the optimal location of fixed stations capable of intercepting the trajectories of 43 surface drifters. We then illustrate the temporal persistence of the stations determined in this way. Finally, we identify possible hotspots of micro-nutrient enrichment for the recurrent spring phytoplanktonic bloom occurring there. Promising applications to other fields, such as larval connectivity or contaminant detection are discussed.</p><p>[1] A. Baudena, E. Ser-Giacomi, C. López, E. Hernández-García, F. d’Ovidio, Crossroads of the mesoscale circulation, Journal of Marine Systems 192, 1-14 (2019).</p>

Evolution of Arctic Ocean surface circulation from 1958 to 2017

2021 ◽  
Vol 206 ◽  
pp. 103638
Author(s):  
Yilin Yang ◽  
Yuanzhi Zhang ◽  
X. San Liang ◽  
Qiuming Cheng ◽  
Jin Yeu Tsou
Keyword(s):  
Arctic Ocean ◽  
Ocean Surface ◽  
Surface Circulation ◽  
Ocean Surface Circulation

High dependence of Ordovician ocean surface circulation on atmospheric CO2 levels

2016 ◽  
Vol 458 ◽  
pp. 39-51 ◽  
Author(s):  
Alexandre Pohl ◽  
Elise Nardin ◽  
Thijs R.A. Vandenbroucke ◽  
Yannick Donnadieu
Keyword(s):  
Ocean Surface ◽  
Atmospheric Co2 ◽  
Surface Circulation ◽  
Co2 Levels ◽  
Ocean Surface Circulation

scholarly journals On the Variability of the Circulation and Water Mass Properties in the Eastern Levantine Sea between September 2016–August 2017

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1741 ◽  
Author(s):  
Mauri ◽  
Sitz ◽  
Gerin ◽  
Poulain ◽  
Hayes ◽  
...  
Keyword(s):  
High Salinity ◽  
Autonomous Systems ◽  
Vertical Mixing ◽  
The North ◽  
Levantine Sea ◽  
Surface Circulation ◽  
Basin Scale ◽  
Geographical Position ◽  
Surface Drifters

The surface circulation and the thermohaline properties of the water masses of the eastern Levantine Sea (Mediterranean Sea) were monitored with mobile autonomous systems (surface drifters and gliders) during the period September 2016–August 2017. The drifters provided data for more than a year and revealed complex circulation features at scales ranging from the basin scale to the sub-mesoscale. Three drifters were captured in a semi-permanent gyre (Cyprus Eddy) allowing a quantitative study of its kinematics. During the experiment, three gliders were operated, in two different periods: September to December 2016 and February to March 2017. The autonomous instruments crossed the prevailing sub-basin structures several times. The collected in-situ observations were analyzed and interpreted in concert with remote sensing products (sea surface temperature and altimetry). The evolution of some of the prevailing features confirmed the complexity of the circulation of the basin. The Cyprus Eddy is the most persistent anticyclone, moving its geographical position and sometimes merging with the North Shikmona Eddy in a bigger structure. The gliders sampled this wide anticyclonic feature revealing its vertical structure in the two different periods. In fall, in stratified conditions, a high salinity core is evident below the thermocline. The isopycnals are characterized by an upward bending over the high salinity lens and a downward bending below it, typical of an anticyclonic modewater eddy. In winter, the core disappears following the vertical mixing that, homogenizes the upper Cyprus Eddy water down to 300 m.

scholarly journals Subtropical surface circulation in the southern Indian Ocean derived from surface drifters

2016 ◽  
Vol 61 (33) ◽  
pp. 3596-3605
Author(s):  
LianYi ZHANG ◽  
Yan DU ◽  
ShaoJun ZHENG ◽  
ZhiGang HE ◽  
ShiQiu PENG
Keyword(s):  
Indian Ocean ◽  
Southern Indian Ocean ◽  
Surface Circulation ◽  
Surface Drifters

Ocean Circulation from the synergy of altimeter-derived and oceanic tracers observations

2021 ◽  
Author(s):  
Daniele Ciani ◽  
Marie-Hélène Rio ◽  
Bruno Buongiorno Nardelli ◽  
Stéphanie Guinehut ◽  
Elodie Charles ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Time Window ◽  
Ocean Surface ◽  
Global Scale ◽  
Surface Currents ◽  
Sensitivity Experiment ◽  
Daily Data ◽  
Basin Scale ◽  
Ocean Surface Currents ◽  
Spatio Temporal

<p>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. The Altimeter observations enable to derive the geostrophic component of the surface currents with effective spatial-temporal resolutions O(100 km) and O(10 days), respectively. Therefore, only the largest mesoscale oceanic features can be accurately resolved. In order to enhance the altimeter system capabilities, we propose a synergistic use of high resolution, satellite-derived Sea Surface Temperature (SST), Chlorophyll concentrations (Chl) and Altimeter-derived currents. Our approach is tested in both global-scale and regional contexts.<br>At global scale, relying on past numerical studies, we perform a sensitivity experiment based on several gap-free SST datasets, emphasizing strengths and weaknesses in ocean currents applications. Overall, the comparison with in-situ measured currents shows that our synergistic method can improve the altimeter estimates up to 30% locally.<br>Then, our method is also implemented with Chl data in the  Mediterranean Sea, where the most energetic variable signals are found at spatio-temporal scales up to 10 km and few days. We test the method feasibility in an Observing System Simulation Experiment relying on model outputs of the European Copernicus Marine Service. Statistical analyses based on the 2017 daily data show that our approach can improve the altimeter-derived currents accuracy up to 50% at the basin scale, also enhancing the effective spatial-temporal resolutions up to 30 km and less than 10 days, respectively. The method efficiency decreases when the surface Chl patterns are dominated by the biological activity rather than the currents advection, which mostly occurs in the mid-February to mid-March time window. Preliminary tests on the method applicability to satellite-derived data are also presented and discussed.</p>

scholarly journals Aegean Surface Circulation from a Satellite-Tracked Drifter Array

2007 ◽  
Vol 37 (7) ◽  
pp. 1898-1917 ◽  
Author(s):  
Donald B. Olson ◽  
Vassiliki H. Kourafalou ◽  
William E. Johns ◽  
Geoff Samuels ◽  
Milena Veneziani
Keyword(s):  
Mesoscale Eddy ◽  
Aegean Sea ◽  
Mesoscale Dynamics ◽  
The North ◽  
Rapid Sampling ◽  
Surface Circulation ◽  
Basin Topography ◽  
Salinity Water ◽  
Ekman Flow ◽  
Eddy Field

Abstract A pilot experiment using an array of 45 drifters to explore the circulation in the north and central Aegean Sea is described. The global positioning system drifters with holey-sock drogues provide positions every hour with data recovery through the Argos system. The drifters were launched in four separate deployments over a 1-yr period. The resulting trajectories confirm the existence of a current around the rim of the basin consistent with a buoyancy plume created by the outflow of Black Sea waters through the Dardanelles (Strait of Çanakkale in Turkish). The degree to which this is augmented by an Ekman response to the dominant northerly winds is not obvious in the dataset owing to mesoscale dynamics that obscure the existence of any westward Ekman flow. The mesoscale eddy field involves anticylonic eddies in the current around the rim of the basin consistent with eddies with low-salinity-water cores. Cyclones are also seen, with the most prominent forming over deep regions in the basin topography. The array also documents the interaction of the currents with the straits through the Sporades and Cyclades island groups. These interactions are complicated by the nature of the mesoscale flow and in some trajectories suggest a Bernouilli acceleration in straits; in others the flow through the island groups appears to be more diffusive and involves deceleration and eddy motions. The rapid sampling by the drifters reveals an extremely nonlinear submesoscale eddy field in the basin with length scales less than 4 km and Rossby numbers of order 1. A better understanding of the dynamics of these features is of importance for understanding the circulation of the basin.

scholarly journals Ocean Currents Reconstruction from a Combination of Altimeter and Ocean Colour Data: A Feasibility Study

2021 ◽  
Vol 13 (12) ◽  
pp. 2389
Author(s):  
Daniele Ciani ◽  
Elodie Charles ◽  
Bruno Buongiorno Buongiorno Nardelli ◽  
Marie-Hélène Rio ◽  
Rosalia Santoleri
Keyword(s):  
Mediterranean Sea ◽  
Time Window ◽  
Ocean Surface ◽  
Global Scale ◽  
Biogeochemical Model ◽  
Surface Currents ◽  
Ocean Surface Currents ◽  
Marine Surface ◽  
The Mediterranean ◽  
Spatio Temporal

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.

scholarly journals Weddell Sea Export Pathways from Surface Drifters

2015 ◽  
Vol 45 (4) ◽  
pp. 1068-1085 ◽  
Author(s):  
Madeleine K. Youngs ◽  
Andrew F. Thompson ◽  
M. Mar Flexas ◽  
Karen J. Heywood
Keyword(s):  
Continental Shelf ◽  
Wind Stress ◽  
Surface Waters ◽  
Weddell Sea ◽  
Surface Velocity ◽  
Wind Stress Curl ◽  
Weddell Gyre ◽  
Surface Circulation ◽  
Surface Drifters ◽  
The Antarctic

AbstractThe complex export pathways that connect the surface waters of the Weddell Sea with the Antarctic Circumpolar Current influence water mass modification, nutrient fluxes, and ecosystem dynamics. To study this exchange, 40 surface drifters, equipped with temperature sensors, were released into the northwestern Weddell Sea’s continental shelf and slope frontal system in late January 2012. Comparison of the drifter trajectories with a similar deployment in early February 2007 provides insight into the interannual variability of the surface circulation in this region. Observed differences in the 2007 and 2012 drifter trajectories are related to a variable surface circulation responding to changes in wind stress curl over the Weddell Gyre. Differences between northwestern Weddell Sea properties in 2007 and 2012 include 1) an enhanced cyclonic wind stress forcing over the Weddell Gyre in 2012; 2) an acceleration of the Antarctic Slope Current (ASC) and an offshore shift of the primary drifter export pathway in 2012; and 3) a strengthening of the Coastal Current (CC) over the continental shelf in 2007. The relationship between wind stress forcing and surface circulation is reproduced over a longer time period in virtual drifter deployments advected by a remotely sensed surface velocity product. The mean offshore position and speed of the drifter trajectories are correlated with the wind stress curl over the Weddell Gyre, although with different temporal lags. The drifter observations are consistent with recent modeling studies suggesting that Weddell Sea boundary current variability can significantly impact the rate and source of exported surface waters to the Scotia Sea, a process that determines regional chlorophyll distributions.

Seasonal variations of the ocean surface circulation in the vicinity of Palau

2006 ◽  
Vol 62 (4) ◽  
pp. 413-426 ◽  
Author(s):  
Scott F. Heron ◽  
E. Joseph Metzger ◽  
William J. Skirving
Keyword(s):  
Seasonal Variations ◽  
Ocean Surface ◽  
Surface Circulation ◽  
Ocean Surface Circulation
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