Control of the Oceanic Heat Content of the Getz‐Dotson Trough, Antarctica, by the Amundsen Sea Low

Tiago S Dotto,Paul R Holland,Laura Herraiz‐Borreguero,Sheldon Bacon,Anna K Wåhlin,Alberto C Naveira Garabato,Satoshi Kimura,Adrian Jenkins,Ola Kalén,Michel Tsamados

doi:10.1029/2020jc016113

Abstract

AbstractThe changing supply of warm Circumpolar Deep Water (CDW) to the West Antarctic continental shelf is responsible for the basal melting and thinning of the West Antarctic ice shelves that has occurred in recent decades. Here we assess the variability in CDW supply, and its drivers, from a multiyear mooring deployed in, and a regional ocean model spanning, the Getz‐Dotson Trough, Amundsen Sea. Between 2010 to 2015, the CDW within the trough underwent a pronounced cooling and freshening, associated with changes in thermohaline properties on isopycnals. Variability in the rate of CDW inflow is controlled by local wind forcing of a shelf break undercurrent, which determines the hydrographic properties of inflowing CDW via tilting of density surfaces above the continental slope. Local wind is coupled to the Amundsen Sea Low (ASL) low‐pressure system, which is modulated by large‐scale climatic modes via atmospheric teleconnections. For the period analyzed, a deeper ASL was associated with westward wind anomaly at the shelf break. Changes in the sea surface slope decelerated the shelf break undercurrent, resulting in less heat accessing the continental shelf and, consequently, a cooling of the Getz‐Dotson Trough. Therefore, the present work suggests that the fate of the West Antarctic ice shelves is closely tied to the future evolution of the ASL.

Highlights

The West Antarctic Ice Sheet (WAIS) has lost mass at high rates in recent decades (Mouginot et al, 2014; Shepherd et al, 2018) and has been argued to be prone to irreversible retreats and a possible collapse in the future (Joughin et al, 2014; Rignot et al, 2014)
The changing supply of warm Circumpolar Deep Water (CDW) to the West Antarctic continental shelf is responsible for the basal melting and thinning of the West Antarctic ice shelves that has occurred in recent decades
Local wind is coupled to the Amundsen Sea Low (ASL) low‐pressure system, which is modulated by large‐scale climatic modes via atmospheric teleconnections

Summary

Introduction

The West Antarctic Ice Sheet (WAIS) has lost mass at high rates in recent decades (Mouginot et al, 2014; Shepherd et al, 2018) and has been argued to be prone to irreversible retreats and a possible collapse in the future (Joughin et al, 2014; Rignot et al, 2014). The thinning of the West Antarctic ice shelves is generally associated with basal melt driven by relatively warm Circumpolar Deep Water (CDW; Paolo et al, 2015). In the Amundsen Sea (Figure 1), the CDW that flows into the troughs has temperatures of 2–4°C above the seawater freezing point, and, on its way toward the ice shelves, it can mix with surrounding waters and change its thermohaline properties

Results

Discussion

Conclusion