Lagrangian pathways and residence time of warm Circumpolar Deep Water on the Antarctic continental shelf

Veronica Tamsitt, University of New South Wales, Climate Change Research Centre, Sydney, NSW, Australia, Matthew H England, Univ New South Wales, Sydney, Australia and Stephen R Rintoul, Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC), Hobart, Australia
The inflow of relatively warm modified Circumpolar Deep Water (CDW) onto the Antarctic Continental Shelf and into ice shelf cavities is a key driver of Antarctic ice shelf mass loss. While there have been recent advances in understanding the processes that control the rate of CDW transport onto the continental shelf in different regions around Antarctic, there is a gap in understanding the fate and residence time of the CDW on the shelf. Here we use Lagrangian particle tracking experiments in a high resolution circum-Antarctic ocean-ice model to map both the pathways and residence times of CDW on the Antarctic continental shelf. We investigate how residence times and transformation of CDW vary by region along the continental shelf. Results show complex spatial heterogeneity in residence times of CDW in the shelf, with generally shorter residence times in regions of rapid water mass transformation on the shelf and much longer residence times elsewhere. These results emphasize that it is the residual of the heat transport of CDW onto the shelf and the transformation into denser waters on the shelf, rather than the heat transport of CDW onto the shelf alone, that is relevant for the reservoir of warm waters on the shelf available to melt the ice shelves.