Climatic Forcing for Contemporary Greenland Ice Sheet Change

Abstract:

Despite the wealth of observations of spatio-temporal changes in ice elevation, or ice velocity, it is extremely challenging for ice sheet models to reproduce these observed contemporary changes. However, if ice sheet models could replicate the observed thinning/thickening, it would increase confidence in their capability of projecting ice sheet evolution, hence future sea level. The challenge therefore becomes how to obtain a set of contemporary forcing that can be applied to ice sheet models and result in ice evolution that reproduces the observed behavior. Three type of forcing need to be estimated: i) the surface mass balance and temperature, ii) the change in basal lubrication due to surface runoff reaching the base of the ice sheet and iii) the oceanic forcing. Nonetheless, the SeaRISE effort (Sea level Response to Ice Sheet Evolution) has demonstrated that ice sheet models have a characteristic and distinct thickness response, or thickness fingerprint, depending on the type of forcing. In addition, the linear combination of the thickness fingerprint resulting from distinct forcing (for example, atmospheric and oceanic) closely resembles the thickness fingerprint resulting from multiple forcing applied simultaneously. We use this fingerprint technique along with the NASA GEOS-5 climate and ISSM ice sheet models to seek a set of forcing that may be used to reproduce contemporary Greenland Ice Sheet change.