Influence of seasonally varying sea-ice concentration and subsurface ocean heat on sea-ice thickness and sea-ice seasonality for a ‘warm-shelf’ region in Antarctica

Abstract

Processes driving changes in sea-ice seasonality and sea-ice thickness were explored for a ‘warm-shelf’ region along the West Antarctic Peninsula using vertically coupled sea-ice-ocean thermodynamic simulations, with and without assimilated satellite sea-ice observations and moored ocean temperature observations. Simulations with assimilated sea-ice observations permitted investigation of surface [thermodynamic and dynamic (e.g., wind-driven)] processes affecting sea-ice thickness and seasonality. Assimilation of quasi-weekly variability in the depth and temperature of the deep warm pycnocline permitted examination of subsurface processes affecting sea-ice. Simulations using assimilated sea-ice observations (and implied motion) always produced greater surface heat fluxes and overall thinner sea ice. Assimilating seasonal and quasi-weekly variability in the depth and temperature of the pycnocline modified the start of the sea-ice season by −23 to +1 d, and also modified the sea ice thickness/seasonality to be thinner/shorter or thicker/longer at sub-seasonal and seasonal timescales, highlighting a mechanism where a shoaling pycnocline enhanced upward deep-water heat fluxes as transient surface-induced turbulence had a greater effect on a reduced mixed layer volume. The observed interplay of surface, subsurface, and sea-ice modulation of ocean-atmosphere heat transfer underscores the importance of representing the interaction between sea-ice concentration and upper ocean variability in climate projections.