Earth System Models
We simulate Arctic sea ice for the past, current and possible future climates, with regional sea ice-ocean and Earth System Models. Regional ocean-sea ice models have the advantage of simulating sea ice with a relatively high grid resolution (a few kilometres) forced by (realistic) atmospheric surface boundary values. The use of realistic boundary conditions allows the validation of these models with sea ice observations directly. Global coupled Climate Models are usually much coarser spatially resolved but have the advantage of simulating the atmosphere model, the ocean and the sea-ice simultaneously. Earth System Models (ESMs) additionally include vegetation and chemistry modules. These models allow projections far into the future by prescribing scenarios of greenhouse gas emissions (and other trace gases like aerosols, see IPCC AR5 WG1 SPM, figure 7b).
In our group, we analyse Arctic sea ice simulated by the CMIP5 global coupled Climate Models (and ESMs) and compare them with statistical means of satellite-derived observations. Figure 1 shows the sea ice area in the southern Barents Sea simulated by CMIP5 models.
For the ICE-ARC project, we work on improvements of sea ice parameterizations. An example of a parameterization is the sub-scale sea ice thickness distribution within one grid box (Castro-Morales et al., 2014). We test those parameterizations in regional sea ice ocean models such as NAOSIM (Köberle and Gerdes, 2003) and an Arctic model set-up of the MITgcm (Castro-Morales et al., 2014). After the testing in these regional models, the parameterizations will be used in the global coupled earth system model MPI-ESM-LR .
Figure 1: Climatological mean seasonal cycle of sea ice area in the southern Barents Sea for 1979-2005: individual simulations of CMIP5 models (red) in comparison with satellite-derived observations from OSI SAF. The black line indicates the climatological mean derived from OSI SAF ice concentration. Its standard deviation (inter-annual variability) is denoted by grey shading. Figure from ACCESS deliverable report D1.51.