Variability of the Ross Gyre, Southern Ocean: Drivers and Responses Revealed by Satellite Altimetry

Dotto, Tiago S.; Garabato, Alberto C. Naveira; Bacon, Sheldon; Tsamados, Michel; Holland, Paul R.; Hooley, Jack; Frajka‐Williams, Eleanor; Ridout, A.; Meredith, Michael P.

doi:10.1029/2018gl078607

Cited by 84 publications

(131 citation statements)

References 63 publications

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“…Furthermore, the deployment of fixed instruments in the top 500 m of the water column is high risk due to the presence of drifting icebergs. Recently, estimates of the barotropic component of the flow on the Antarctic slope have been obtained through the use of satellite altimeters (Armitage et al, ; Dotto et al, ) and a few moored arrays (e.g., Núñez‐Riboni & Fahrbach, ; Peña‐Molino et al, ). Those estimates are consistent with the results of our model: the westward flow associated with the Antarctic Slope Current is stronger in autumn and winter while it is weaker in spring and summer.…”

Section: Discussionmentioning

confidence: 99%

Seasonality of Warm Water Intrusions Onto the Continental Shelf Near the Totten Glacier

et al. 2019

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Warm Modified Circumpolar Deep Water (MCDW) from the Southern Ocean drives rapid basal melt of the Totten Ice Shelf on the Sabrina Coast (East Antarctica), affecting the mass balance of the grounded Totten Glacier. Recent observations show that MCDW intrudes onto the continental shelf through a depression at the shelf break. Here we investigate such intrusions by combining (1) new oceanographic and bathymetric observations collected for two consecutive years by profiling floats in the depression south of the shelf break, (2) oceanographic measurements collected by conductivity‐temperature‐depth‐instrumented seals on continental slope, and (3) an ocean model. The depression provides a pathway for persistent inflow of warm (0‐1°C) MCDW to the inner shelf. In austral autumn and early winter MCDW intrusions were up to 0.5°C warmer and were ~75 m thicker than in spring and summer. The seasonality of the flow on the continental slope explains the seasonality of the intrusions. The MCDW layer on the continental slope is warmer and thicker to the east of the depression than to the west. In autumn and early winter a strong, top‐to‐bottom westward current (Antarctic Slope Current) transports the warmer and thicker MCDW layer along the slope and is diverted poleward at the eastern entrance of the depression. A bottom‐intensified eastward current (Antarctic Slope Undercurrent) develops in other months, allowing cooler and thinner intrusions to enter the depression from the west. Our study illustrates how circulation on the Antarctic slope regulates the ocean heat delivery to the continental shelf and ultimately to the ice shelves.

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Section: Discussionmentioning

confidence: 99%

Seasonality of Warm Water Intrusions Onto the Continental Shelf Near the Totten Glacier

et al. 2019

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“…Most inflow enters through the northeast corner, near the separation of the gyre boundary from the Pacific‐Antarctic Ridge, and along the eastern boundary of the gyre. The separation of the gyre from the PAR allows a wider range of seasonal variability in the gyre boundary (Dotto et al, ) and likely enhances generation of eddies (Bracco & Pedlosky, ; Thompson & Sallée, ). There is also significant inflow in the far‐western region of the gyre.…”

Section: Discussionmentioning

confidence: 99%

“…Considering previous studies (Dellnitz et al, ; Dotto et al, ) which identify significant variability in gyre structure we considered using a time‐varying boundary. However, while we found significant variability (white contours if Figure show a subset of time‐varying −8‐Sv contours) we did not find a clear separation of gyre structure into a monthly or semiannual component with our definition of depth‐integrated transport.…”

Section: Methodsmentioning

confidence: 99%

Exchange of Water Between the Ross Gyre and ACC Assessed by Lagrangian Particle Tracking

Roach

Speer

2019

JGR Oceans

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To reach upwelling and downwelling zones deep within the Southern Ocean seasonal sea ice cover, water masses must move across the Antarctic Circumpolar Current and through current systems including the Ross Gyre, Weddell Gyre, and Antarctic Slope Current. In this study we focus our attention on the Lagrangian exchange between the Ross Gyre and surrounding current systems. We conducted numerical experiments using five‐day 3‐D velocity fields from the Southern Ocean State Estimate with a particle tracking package to identify pathways by which waters move from near the Antarctic coastal margins or Antarctic Circumpolar Current into the interior of the Ross Gyre, and to identify the time scales of variability associated with these pathways. Waters from near the Antarctic margins enter the Ross Gyre along the western and northern boundaries of gyre until the gyre separates from the Pacific‐Antarctic Ridge near fracture zones. At this juncture, Antarctic Circumpolar Current‐derived inflow dominates the across‐gyre transport up to the Antarctic margin. Transport and exchange associated with different time‐average components of flow are calculated to determine the relative contributions of high‐ and low‐frequency and time‐mean components.

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“…where g is gravity, f is the Coriolis parameter, and x and y are the meridional distances. The uncertainty for the gridded SSH is 1.5 cm (Dotto et al, ).…”

Section: Methodsmentioning

confidence: 99%

Phased Response of the Subpolar Southern Ocean to Changes in Circumpolar Winds

Garabato

Dotto

Hooley

et al. 2019

Geophysical Research Letters

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The response of the subpolar Southern Ocean (sSO) to wind forcing is assessed using satellite radar altimetry. sSO sea level exhibits a phased, zonally coherent, bimodal adjustment to circumpolar wind changes, involving comparable seasonal and interannual variations. The adjustment is effected via a quasi‐instantaneous exchange of mass between the Antarctic continental shelf and the sSO to the north, and a 2‐month‐delayed transfer of mass between the wider Southern Ocean and the subtropics. Both adjustment modes are consistent with an Ekman‐mediated response to variations in surface stress. Only the fast mode projects significantly onto the surface geostrophic flow of the sSO; thus, the regional circulation varies in phase with the leading edge of sSO sea level variability. The surface forcing of changes in the sSO system is partly associated with variations of surface winds linked to the Southern Annular Mode and is modulated by sea ice cover near Antarctica.

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Variability of the Ross Gyre, Southern Ocean: Drivers and Responses Revealed by Satellite Altimetry

Cited by 84 publications

References 63 publications

Seasonality of Warm Water Intrusions Onto the Continental Shelf Near the Totten Glacier

Seasonality of Warm Water Intrusions Onto the Continental Shelf Near the Totten Glacier

Exchange of Water Between the Ross Gyre and ACC Assessed by Lagrangian Particle Tracking

Phased Response of the Subpolar Southern Ocean to Changes in Circumpolar Winds

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