Spatial and temporal variability of the Antarctic Slope Current in an eddying ocean-sea ice model

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• Wilma Huneke (Australian National University)
• Wednesday 24 March 2021, 09:00-10:00
• British Antarctic Survey, Zoom.

If you have a question about this talk, please contact Dr Irena Vankova.

The basal melt rate of Antarctica’s ice shelves is largely controlled by heat delivered from the Southern Ocean to the Antarctic continental shelf. The Antarctic Slope Current (ASC) is an almost circumpolar feature that encircles Antarctica along the continental shelf break in an anti-clockwise direction. Because the circulation is to first order oriented along the topographic slope, it inhibits exchange of water masses between the Southern Ocean and the Antarctic continental shelf and thereby impacts cross-slope heat supply. Direct observations of the ASC system are sparse, but indicate a highly variable flow field both in time and space. Given the importance of the circulation near the shelf break for cross-shelf exchange of heat, it is timely to further improve our knowledge of the ASC system. This study makes use of the global ocean-sea ice model ACCESS -OM2-01 with a 1/10 degree horizontal resolution and describes the spatial and temporal variability of the velocity field. We categorise the modelled ASC into three different regimes, similar to previous works for the associated Antarctic Slope Front: (i) A surface-intensified current found predominantly in East Antarctica, (ii) a bottom-intensified current found downstream of the dense shelf water formation sites in the Ross, Weddell, and Prydz Bay Seas, and (iii) a reversed current found in West Antarctica where the eastward flowing Antarctic Circumpolar Current impinges onto the continental shelf break. We show that the regional distribution of the ASC regimes aligns well with that of the frontal structures. Looking at the temporal variability, we find differences in the seasonal characteristics for each regime. The surface-intensified ASC exhibits the largest seasonal variability with larger velocities in the autumn and winter months as a response to the variability in the wind field. As a final addendum, note that both spatial and temporal variability is extensive within each ASC regime.

This talk is part of the British Antarctic Survey - Polar Oceans seminar series series.

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