An idealized study of open water formation in sea ice

The formation of open water in sea ice has been investigated in numerical experiments under idealized conditions. In this study the widely used Hibler two category viscous-plastic sea ice model is compared to a model that additionally takes into account redistribution of the deformed ice into categories of ridged and rafted ice. Special attention is paid to the differences in the open water fractions produced by the models. Two different scenarios are considered, the first is a low pressure system crossing a uniform ice field and the second is a situation of polynya formation at a coastline under different surface winds.

It is found that in areas where the surface winds have spatial gradients the model that includes redistribution processes produces larger open water concentrations. This occurs because the ice is not treated as one level ice category but is redistributed during deformation processes to deformed ice classes. It is concluded that the introduction of redistribution processes has a non-negligible effect on open water formation. This is an important issue to be considered in global ocean circulation models, where the amount of open water influences the bottom water formation rate and thus a substantial part of the global water mass distribution.