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

Antarctic coastal polynyas play a vital role in atmosphere–ocean interactions and local ecosystems. This study investigates the interannual variability of springtime coastal polynyas over the Ross Sea based on satellite-retrieved sea-ice concentration (SIC) data from 1992 to 2021. Firstly, the springtime coastal polynya areas display large interannual variability as well as a positive trend of about 2000 km² (10 yr)⁻¹ over the 30 years. Secondly, based on composite analysis, in spring, we find that a 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 m⁻²), resulting in upper-ocean warming (~0.4°C) and significant sea-ice loss in late summer (~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 highly consistent with that of observations. This further confirms the circulations–polynyas–sea-ice physical linkages. 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.