Simple hybrid sea ice nudging method for improving control over
partitioning of sea ice concentration and thickness
Abstract
To assess the effect of ocean-atmosphere coupling in the climate
response to forced sea ice loss, the PAMIP (Polar Amplification Model
Intercomparison Project) protocol includes centennial coupled
atmosphere-ocean general circulation model simulations with imposed sea
ice loss. The protocol, which specifies sea ice concentration and
thickness distribution targets, does not prescribe a method for
achieving them. Although different methods for imposing sea ice loss (or
growth) in models have been documented, testing of the method-dependence
of the resulting climate responses has been limited. Achieving the
targeted sea ice state has proven to be challenging using the ghost-flux
nudging method, which induces ice melt from below, as this method does
not constrain the partitioning between thickness and concentration. We
propose, describe and test a Simple method that combines the advantages
of direct sea ice nudging and ghost-flux nudging. This hybrid nudging
method is able to better capture the partitioning between thickness and
concentration while conserving total water content. We document
thoroughly the ability of this novel sea ice constraining method to
reach specific targets for both polar regions.