Historical Variability of Circumpolar Deep Water in the Bellingshausen Sea, Antarctica

Subsurface water masses, especially Circumpolar Deep Water (CDW), in the Southern Ocean waters surrounding Antarctica have experienced dramatic warming and freshening over recent decades. Observations show that the most dramatic of this warming occurs west of the Antarctic Peninsula, especially in the Bellingshausen Sea. The subsurface warming is believed to contribute to increased basal melting of floating ice shelves in the Bellingshausen Sea where some of the largest glacial melt rates in Antarctica have been observed in the recent decades.

In this study, we explore available hydrographic data on the Bellingshausen Sea continental shelf in order to explore changes of CDW properties. Three data sets, from 1994, 2007, and 2019, are available and used here, with stations spanning the entirety of the Bellingshausen Sea. Changes in the CDW layer are explored by analyzing the relationship of the CDW maximum temperature, layer thickness and its heat content. An increase in the CDW temperature and heat content would in turn point to changes in the ice pattern and melting rates, and hence the meltwater content of the water column. Using the available hydrographic data, the meltwater fractions are calculated and a relationship to surface wind forcing and ice patterns is explored.