Past versus future impacts of changing sea ice cover on the Greenland Ice Sheet (Task 3.1)

The Global Climate Models-GCMs (EC-Earth and NorESM) improved through the paleo- and process-studies in work package 1 and Work package 2 will be used to simulate the sea ice conditions and ice sheet response for the Eemian and the Marine Interstadial 3 (MIS3) time slice intervals along with a future warming scenario. Long runs will be performed with the coupled Global Climate Model- Ice Sheet Model (GCM-ISM) systems for each time interval (including the pre-industrial period) to ensure stability of the climate system. From the pre-industrial state a future warming scenario will then be started by raising atmospheric CO2 concentration by 1%/year until a quadrupling relative to pre-industrial values. This run will be extended to about a millennium to provide us with a significantly warmed climate to which we can compare the paleo-responses.

The detailed Greenland Ice Sheet response will be assessed with high-resolution coupled Regional Climate Model-Ice Sheet Model (RCM-ISM) experiments forced on the boundary with the climates from the above ESM experiments. The same time slices and future projection will be performed and the increased horizontal and vertical resolution will allow for a more realistic surface mass balance representation and a more direct comparison to the localized Renland site.

The paleo-climatic states will both be analyzed in terms of their internal dynamics and compared to the reconstructed sea surface conditions from work package 1. A high risk here is that the responses will not be similar to the reconstructions and our efforts must then focus on determining the causes of these differences, changing or nudging the runs and identifying avenues of model development.