Exploring sea ice transport dynamics at the eastern gate of the Ross Sea

Abstract

As Antarctic sea ice extent continues to reach record lows, significant efforts have been directed towards understanding the underlying processes and their regional differences within the Southern Ocean. Here, we explore the dynamics of zonal sea ice transport at the eastern gate of the Ross Sea from 1988 to 2023 using GIOMAS-model and ERA5-reanalysis data. Our analysis reveals a modest overall increase in eastward sea ice transport (3.721 ± 0.672 km³/month per decade), with diverging trends in the coastal and open ocean zones. Driven by easterly winds and the Antarctic Slope Current, the predominant westward transport in the coastal region experienced a significant rise during the early 2000s, followed by a steep decline post-2011. Conversely, driven by the Antarctic Circumpolar Current, the strong open-ocean transport exhibited a moderate increase towards the Amundsen Sea until the late 1990s, which was interrupted by a reversal in 2007. The variability of zonal sea ice transport and its underlying conditions (sea ice concentration, thickness, and zonal drift) revealed considerable shifts throughout the different decades and on seasonal scales. During austral winter, approximately half of the zonal sea ice transport variability seems to be driven by large-scale teleconnections, including the Southern Annular Mode, Southern Oscillation Index, Amundsen Sea Low and the Zonal Wave 3 with considerable impacts on the wind stress field. Whereas during summer, the Southern Oscillation Index emerges as the dominant driver, exhibiting a significant positive correlation (r=0.55, p<0.001) that reflects the influence of the El Niño-Southern Oscillation, while other teleconnections play minimal roles. Our study highlights the complex nature of sea ice transport through the eastern gate of the Ross Sea towards the Amundsen Seas, where contrasting climatic conditions are known to occur.