This Work Package addresses SO2 and answers Research Question 2:

Specific Objective 2 – Improve the physical representation of the processes responsible for historical changes in Antarctic ice, ocean and atmosphere models, including the decadal growth and recent collapse

Research Question 2. Can these processes be represented reliably in models to reproduce observed changes in Antarctic sea ice extent?

To address RQ2, we will use the atmosphere, sea ice and ocean observations in WP1 to calibrate and test model physics linked to Antarctic sea ice variability. In particular, we will constrain fluxes of momentum/heat/salt/moisture between air/ice/ocean, and ocean turbulence, in sea ice (SI3) and ocean (NEMO) models, and in a coupled climate model (GC5). We will construct and analyse observationally constrained hindcasts of the ice-ocean state over the satellite era. We will perform an in-depth evaluation of CMIP6 simulations to assess how reliably the dominant processes are represented. Outputs from WP2 will directly feed into WP3 tasks and the WP4 White Paper.

Task 2.1 – Incorporate model physics into the sea ice model SI3

Task 2.2 – Calibrate and improve the ocean–sea ice model using in-situ and satellite observations

Task 2.3 – Use the Calibrated and enhanced version of NEMO-SI3 to produce observationally constrained hindcast estimates and spatiotemporal analyses of ocean and sea ice conditions.

Task 2.4 CMIP6 evaluation

Evaluate ability of models to simulate sea ice itself as well as aspects of ocean state and atmospheric circulation that are relevant for extremes

In order to

1.Put model development results in context

2.Determine which models are fit for purpose for seeking deeper understanding (-> WP3)

Task 2.5 Assess and improve the coupled GC5 model by utilising observations from WP1 and model developments from T2.1 and T2.2.