Impacts of Antarctic runoff changes on the Southern Ocean sea ice in an eddy-permitting sea ice-ocean model
Verena Haid1, Dorotea Iovino1, and Simona Masina1,21Ocean Dynamics and Data Assimilation, Centro Euro-Mediterraneo sui Cambiamenti Climatici, Bologna, 40128, Italy 2Istituto Nazionale di Geofisica e Vulcanologia (INGV), Bologna, 40128, Italy
Received: 06 Apr 2016 – Accepted for review: 08 May 2016 – Discussion started: 13 Jun 2016
Abstract. In a warming climate, observations indicate that the sea ice extent around Antarctica has increased over the last decades. One of the suggested explanations is the stabilizing effect of increased mass loss of the Antarctic ice sheet. We investigated the sea ice response to changes in the amount and especially the spatial distribution of freshwater. We performed a sensitivity study by comparing a set of numerical simulations with additional supply of water at the Antarctic ocean surface. Here, we analyse the response of the sea ice cover and the on-shelf water column to variations in the amount and distribution of the prescribed surface freshwater flux.
Our results confirm that an increase in fresh water input can increase the sea ice extent. However, a very strong increase of freshwater will eventually invert the trend. Our experiments suggest that the spatial distribution of the freshwater is of great influence. It affects sea ice dynamics and can strongly alter regional sea ice concentration and thickness. For strong regional contrasts in the freshwater addition the local change in sea ice is dominated by the dynamic response, which generally opposes the thermodynamic response. Furthermore, we find that additional coastal runoff generally leads to fresher and warmer dense shelf waters. Comparing our results with the observed trend, we estimate that the current increase of fresh water originating from the Antarctic Ice Sheet contributes between 5 % and 24 % to the trend observed in the sea ice extent.
Haid, V., Iovino, D., and Masina, S.: Impacts of Antarctic runoff changes on the Southern Ocean sea ice in an eddy-permitting sea ice-ocean model, The Cryosphere Discuss., doi:10.5194/tc-2016-81, in review, 2016.