Impact of strong katabatic wind event variability on sea ice dynamics in Terra Nova Bay Polynya, Antarctica

Abstract

Polynyas along the Antarctic coastline are essential for sea ice production and the formation of Antarctic Bottom Water (AABW). They are formed and maintained by strong and persistent katabatic winds that push the ice away from the coast. Satellite data, in-situ meteorological observations and Reanalysis datasets all indicate a decline in sea ice concentration (SIC) over the Terra Nova Bay Polynya (TNBP) from 2013 to 2022, consistent with the occurrence of an increasing trend of strong katabatic wind events (SKWEs). On the interannual timescale, significant correlations between the TNBP area and the duration of SKWEs were observed in austral summer, autumn and winter, and also in April and October during 2003？2022. Sea ice volume budget analysis shows that SKWEs drive rapid sea-ice removal through advection and divergence, whereas thermodynamic processes dominate sea ice formation on an annual basis. The increase in SKWEs was associated with a deepened and southwestward-displaced Amundsen Sea Low (ASL) and an enhanced pressure gradient between the interior plateau and the coast, both potentially linked to a more positive Southern Annular Mode (SAM). These findings provide a mechanistic understanding of long-term polynya variability, with implications for regional sea-ice changes and AABW.