High Frequency Satellite Surveillance of Gulf of Mexico Loop Current Frontal Eddy cyclones

Walker, Nan D.; Leben, R. R.; Anderson, Steven P.; Haag, Alaric; Pilley, Chet

doi:10.23919/oceans.2009.5422154

Cited by 3 publications

(5 citation statements)

References 12 publications

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“…In the Gulf of Mexico, mesoscale circulation associated with the Loop Current forms as the Caribbean Current enters the Yucatan Channel [ 22 – 25 ]. Cyclonic and anti-cyclonic eddies are often shed from the Loop Current [ 25 ], and these features can persist for at least 1.3 to 9.6 months [ 24 ]. Due to the narrowing of the continental shelf in the northeastern regions of the NGOM, mesoscale circulation interacts frequently with coastal shelf waters, including entrainment that can transport shelf water up to 300 km seaward [ 26 – 28 ].…”

Section: Introductionmentioning

confidence: 99%

Changes in Microbial Plankton Assemblages Induced by Mesoscale Oceanographic Features in the Northern Gulf of Mexico

2015

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Mesoscale circulation generated by the Loop Current in the Northern Gulf of Mexico (NGOM) delivers growth-limiting nutrients to the microbial plankton of the euphotic zone. Consequences of physicochemically driven community shifts on higher order consumers and subsequent impacts on the biological carbon pump remain poorly understood. This study evaluates microbial plankton <10 μm abundance and community structure across both cyclonic and anti-cyclonic circulation features in the NGOM using flow cytometry (SYBR Green I and autofluorescence parameters). Non-parametric multivariate hierarchical cluster analyses indicated that significant spatial variability in community structure exists such that stations that clustered together were defined as having a specific ‘microbial signature’ (i.e. statistically homogeneous community structure profiles based on relative abundance of microbial groups). Salinity and a combination of sea surface height anomaly and sea surface temperature were determined by distance based linear modeling to be abiotic predictor variables significantly correlated to changes in microbial signatures. Correlations between increased microbial abundance and availability of nitrogen suggest nitrogen-limitation of microbial plankton in this open ocean area. Regions of combined coastal water entrainment and mesoscale convergence corresponded to increased heterotrophic prokaryote abundance relative to autotrophic plankton. The results provide an initial assessment of how mesoscale circulation potentially influences microbial plankton abundance and community structure in the NGOM.

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Section: Introductionmentioning

confidence: 99%

Changes in Microbial Plankton Assemblages Induced by Mesoscale Oceanographic Features in the Northern Gulf of Mexico

2015

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“…In the early weeks of the DH spill (the end of April/beginning of May, 2010) we identified – by preliminarily analysis of CCAR Sea Surface Anomaly interpolated data – an East-West trending “ridge" of positive SLA, possibly related to mesoscale slope eddies [8] , [16] , [17] , which appeared to be arresting southward spread of the oil slick ( Figure 1A, D ). Around May 8–9, a “valley" opened in the ridge just south of the DH site and the slick rapidly expanded southward ( Figure 1B, E ).…”

Section: Resultsmentioning

confidence: 99%

“…Around May 8–9, a “valley" opened in the ridge just south of the DH site and the slick rapidly expanded southward ( Figure 1B, E ). This “ridge effect" demonstrates an influence of SSL (and thus of SST fronts [16] , [17] ) that was not captured by ocean circulation models – stressing the role of non-geostrophic, cross-slope effects [8] , [18] on oil slick dynamics.…”

Section: Resultsmentioning

confidence: 99%

“…Pressure-driven flow magnitudes are comparable to modeled ocean current velocities, but differ in their direction. It is therefore possible that some component of oil slick movement is independent of the underlying surface ocean currents, in the presence of SSL/SST fronts [8] , [16] , [17] . This decoupling may be enhanced by the suppression of wind-driven transport, due to reduction of sea surface roughness by oil slicks [32] .…”

Section: Resultsmentioning

confidence: 99%

“…Walker et al [8] suggested that, due to its buoyancy, an oil slick may be strongly affected by variations in sea surface elevation: frontal zones recognized in SLA and SST patterns [16] , [17] may thus constitute efficient traps or natural booms for spilled oil. This work stresses the need to better understand the additional contribution that SSL patterns exert on the movement of oil spills, and in particular whether the MR plume may affect mesoscale SSL patterns.…”

Section: Introductionmentioning

confidence: 99%

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Mississippi River and Sea Surface Height Effects on Oil Slick Migration

2012

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Millions of barrels of oil escaped into the Gulf of Mexico (GoM) after the 20 April, 2010 explosion of Deepwater Horizon (DH). Ocean circulation models were used to forecast oil slick migration in the GoM, however such models do not explicitly treat the effects of secondary eddy-slopes or Mississippi River (MR) hydrodynamics. Here we report oil front migration that appears to be driven by sea surface level (SSL) slopes, and identify a previously unreported effect of the MR plume: under conditions of relatively high river discharge and weak winds, a freshwater mound can form around the MR Delta. We performed temporal oil slick position and altimeter analysis, employing both interpolated altimetry data and along-track measurements for coastal applications. The observed freshwater mound appears to have pushed the DH oil slick seaward from the Delta coastline. We provide a physical mechanism for this novel effect of the MR, using a two-layer pressure-driven flow model. Results show how SSL variations can drive a cross-slope migration of surface oil slicks that may reach velocities of order km/day, and confirm a lag time of order 5–10 days between mound formation and slick migration, as observed form the satellite analysis. Incorporating these effects into more complex ocean models will improve forecasts of slick migration for future spills. More generally, large SSL variations at the MR mouth may also affect the dispersal of freshwater, nutrients and sediment associated with the MR plume.

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Airborne Ocean Surface Current Measurements for Offshore Applications

et al. 2015

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Previous research programs have developed and demonstrated the capability to extract near-shore surface currents from airborne sequences of visual images of surface waves. This same technique can be used for remote sensing of the open ocean to retrieve surface currents over extensive areas in a relatively short period of time. Here, we demonstrate airborne current measurements over deepwater areas of the Gulf of Mexico. The system comprises a pair of digital cameras to image the surface waves, and inertial navigation system and software processing to retrieve the Doppler shift due to the ocean currents. The system measures currents in real-time along the flight path with an accuracy of 5 cm/s on 250 m ϫ 250 m scales. A typical flight can cover 1000 km of linear flight lines in a 4 hour period. The survey data provide a synoptic scale view of Loop Current eddies and detailed measurements along oceanic fronts. This new technology can fulfill a need for rapidly acquiring real-time measurements of currents over a broad region in support of oil spill response; offshore surface current monitoring; and search and rescue operations.

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High Frequency Satellite Surveillance of Gulf of Mexico Loop Current Frontal Eddy cyclones

Cited by 3 publications

References 12 publications

Changes in Microbial Plankton Assemblages Induced by Mesoscale Oceanographic Features in the Northern Gulf of Mexico

Changes in Microbial Plankton Assemblages Induced by Mesoscale Oceanographic Features in the Northern Gulf of Mexico

Mississippi River and Sea Surface Height Effects on Oil Slick Migration

Airborne Ocean Surface Current Measurements for Offshore Applications

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