Variability of Springtime Coastal Polynyas over the Ross Sea and its Impact on the Following Sea Ice Evolution

Antarctic coastal polynyas play a pivotal role in atmosphere-ocean interactions and local ecosystems. This study investigates interannual variability of the springtime coastal polynyas over the Ross Sea based on satellite-retrieved sea ice concentration (SIC) from 1992 to 2021. Firstly, the springtime coastal polynya areas display large interannual variability as well as a positive trend of about 0.002 million km2 per decade over the 30 years. Secondly, based on the composite analysis, in spring, we find that deepened Amundsen Sea Low (ASL) induces stronger meridional winds over the eastern Ross Sea, leading to stronger sea ice advection and expansion of coastal polynya areas. This is accompanied by more solar radiation absorption in early summer (about 16 W/m2), resulting in the upper ocean warming (about 0.4°C) and significant sea ice loss in late summer (about 50% SIC). Additionally, the physical processes are validated by 500-year piControl simulations of a state-of-the-art Earth system model. Based on the same composite analysis, the results show that the sea ice decline is consistent with the deepening of the ASL and the increase of the meridional sea ice advection of the preceding spring, which is very consistent with that of observations. This further confirms the physical linkages of circulations-polynyas-seaice. Since the springtime ASL is strongly modulated by the tropical Pacific variability and the stratospheric polar vortex, changes in the polynya areas of the Ross Sea can be traced back to remote regions.