Deep Eddies in the Gulf of Mexico Observed with Floats

Furey, Heather H.; Bower, Amy S.; Pérez-Brunius, Paula; Hamilton, Pat B.; Leben, R. R.

doi:10.1175/jpo-d-17-0245.1

Cited by 28 publications

(22 citation statements)

References 44 publications

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“…Eddies in the southwest, near the passage towards the Norwegian Sea, had radii of about 3 km and velocities of 3 to 5 cm s -1 . In this area, where the EIC leaves the Iceland Sea, the coherent "boundary" eddies spin up inshore of the main boundary current and slope are similar to the type of anti-cyclonic eddies that were present in the Gulf of Mexico between the cyclonic boundary current and slope (Furey et al 2018).…”

Section: Mesoscale and Other Small Scale Motionsmentioning

confidence: 79%

The subsurface circulation of the Iceland Sea observed with RAFOS floats

Jong

Søiland

Bower

et al. 2018

Deep Sea Research Part I: Oceanographic Research Papers

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The pathways of dense waters located above the sill depth of Denmark Strait were investigated in the Iceland Sea using 52 acoustically tracked RAFOS floats. These floats were deployed in summer 2013 and 2014, with a target depth of 500 m, resulting in a total of 40.9 float-years of track data covering the Iceland Sea basin. In the interior Iceland Sea basin, the float tracks showed a double gyre circulation, out of which floats eventually escaped towards the Norwegian Sea in the East Icelandic Current, with some appearing to be en route to the Faroe Bank Channel. Four floats exited through Denmark Strait and surfaced in the Labrador and Irminger Seas. Four other floats deployed west of the Kolbeinsey Ridge at 70˚N show the connection between the East Greenland Current and the East Icelandic Current. Floats deployed east of the Kolbeinsey Ridge along the Icelandic slope were captured in a region with no clear main flow. Eddy motions, mainly small scale (radii of 0.5 to 3 km), are seen throughout the Iceland Sea. Several floats were grounded on the Icelandic slope both east and west of the Kolbeinsey Ridge due to upslope currents, which created a rim of cold water along the slope. While this water was indicative of the presence of the North Icelandic Jet, no connection between the eastern Iceland Sea and Denmark Strait sill was found. Our investigation of wind stress curl fields from atmospheric reanalysis data suggests that high wind stress curl conditions may have been unfavorable for a westward connection by the North Icelandic Jet at the time of the float observations.

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Section: Mesoscale and Other Small Scale Motionsmentioning

confidence: 79%

The subsurface circulation of the Iceland Sea observed with RAFOS floats

Jong

Søiland

Bower

et al. 2018

Deep Sea Research Part I: Oceanographic Research Papers

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“…Journal of Geophysical Research: Oceans 10.1029/2020JC016488 and topographic Rossby waves (TRWs) (e.g., Furey et al, 2018;Hamilton, 1990;Kolodziejczyk et al, 2011;Tenreiro et al, 2018), which are nearly depth independent or bottom intensified in the deep layer. Also, because group speeds of the TRWs are faster than the LCE propagation speeds, deep ocean motions become progressively decoupled from those in the upper layer from east to west (Hamilton, 1990).…”

Section: Research Articlementioning

confidence: 99%

“…In the vertical direction, the LC and the LCEs can extend to 800–1,000 m, where the weakest currents are usually observed (Hamilton et al, 2000). Below that level, limited observations from mooring arrays and deep ocean floats indicate that the current variability in the lower layer is largely from mesoscale eddies and topographic Rossby waves (TRWs) (e.g., Furey et al, 2018; Hamilton, 1990; Kolodziejczyk et al, 2011; Tenreiro et al, 2018), which are nearly depth independent or bottom intensified in the deep layer. Also, because group speeds of the TRWs are faster than the LCE propagation speeds, deep ocean motions become progressively decoupled from those in the upper layer from east to west (Hamilton, 1990).…”

Section: Introductionmentioning

confidence: 99%

Coupling of the Surface and Near‐Bottom Currents in the Gulf of Mexico

Zhu

Liang

2020

JGR Oceans

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Coupling between the surface and near-bottom currents in the Gulf of Mexico (GoM) has been reported in many case studies. However, geographical variations of this coupling need more examination. In this study, surface geostrophic currents derived from satellite-observed sea surface height and subsurface currents from a collection of deep ocean moorings are used to examine the surface and bottom coupling in different parts of the GoM. The short-period (30-90 days) fluctuations generated by the Loop Current (LC) and the LC eddies (LCEs) have a more vertically coherent structure and stronger deep ocean expressions than the long-period fluctuations (>90 days). In addition, the strength of the coupling is modulated by the long-period variations of the LC and LCE sheddings. Moreover, the surface and bottom coupling varies geographically. In the LC region, the surface fluctuations along the eastern side of the LC are important in causing the bottom current fluctuations through baroclinic instability under the LC and through traveling topographic Rossby waves (TRWs) north of the LC. In the central deep GoM, the bottom currents are affected by the upper fluctuations of the northern LC through both local baroclinic instability and remote TRW propagation. In the northwestern GoM, the bottom current fluctuations are largely related to the remote surface variability from the west side of the LC by TRWs propagating northwestward. This study will help us better understand mechanisms of the bottom current fluctuations that are important for the dispersal of deep ocean materials and properties. Plain Language Summary Bottom currents in the Gulf of Mexico (GoM) are important in many ways, such as transporting fish larvae and spilled oil. However, in contrast to surface currents that are easily derived from the abundant satellite observations, our understanding of the bottom currents is very limited. In this study, the relationships between surface and near-bottom current fluctuations in different parts of the GoM are investigated by combining a collection of historical near-bottom current measurements and satellite data. The results show that the bottom current variability is linked to local processes such as current instability or remote processes through planetary wave propagation. The surface and bottom coupling is mainly related to the short-period variability generated along the Loop Current and the Loop Current eddies and has a significant influence on the bottom currents. Although the long-period fluctuations have weak bottom expressions, they can modulate the strength of the short-period coupling. Studying the coupling between the surface and bottom current fluctuations in the GoM can advance our understanding of mechanisms of the bottom currents that are important for the deep ocean ecosystem and industrial operations.

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“…This supposition would support the behavioral argument posited above. Given that the influence of anticyclonic features can be detected well into, and at times below, the 600-1000 m depth interval (Godø et al, 2012;Furey et al, 2018), it is not surprising to see a response in the sound scattering layers. In our case we detected not only an increase in biomass, but also deepening of the layers associated with LCOW.…”

Section: Sound Scattering Layer Response To Oceanographic Featuresmentioning

confidence: 99%

Oceanographic Structure and Light Levels Drive Patterns of Sound Scattering Layers in a Low-Latitude Oceanic System

et al. 2020

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Several factors have been reported to structure the spatial and temporal patterns of sound scattering layers, including temperature, oxygen, salinity, light, and physical oceanographic conditions. In this study, we examined the spatiotemporal variability of acoustically detected sound scattering layers in the northern Gulf of Mexico to investigate the drivers of this variability, including mesoscale oceanographic features [e.g., Loop Current-origin water (LCOW), frontal boundaries, and Gulf Common Water]. Results indicate correlations in the vertical position and acoustic backscatter intensity of sound scattering layers with oceanographic conditions and light intensity. LCOW regions displayed consistent decreases, by a factor of two and four, in acoustic backscatter intensity in the upper 200 m relative to frontal boundaries and Gulf Common Water, respectively. Sound scattering layers had greater backscatter intensity at night in comparison to daytime (25x for frontal boundaries, 17x for LCOW, and 12x for Gulf Common Water). The importance of biotic (primary productivity) and abiotic (sea surface temperature, salinity) factors varied across oceanographic conditions and depth intervals, suggesting that the patterns in distribution and behavior of mesopelagic assemblages in low-latitude, oligotrophic ecosystems can be highly dynamic.

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Deep Eddies in the Gulf of Mexico Observed with Floats

Cited by 28 publications

References 44 publications

The subsurface circulation of the Iceland Sea observed with RAFOS floats

The subsurface circulation of the Iceland Sea observed with RAFOS floats

Coupling of the Surface and Near‐Bottom Currents in the Gulf of Mexico

Oceanographic Structure and Light Levels Drive Patterns of Sound Scattering Layers in a Low-Latitude Oceanic System

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