Degree 1 and 2 Temporal Gravity, Ice Sheet Mass Loss and Glacier Mass Change.

Abstract:

In order to estimate the present day contribution of ice sheets and glaciers to sea level change we rely on a global mascon inversion approach applied to GRACE monthly potential coefficient sets collected since 2002. This method assumes that the monthly GRACE product is de-aliased, but also that degree-2 terms are obtained from satellite laser ranging solutions. In addition use is made of glacial isostatic adjustment models that take away the rebound effect in the mantle which is seen by both GRACE and SLR. Next an integral equation approach is used to estimate geo-center related geophysical loading, yet, the method is affected by all de-aliasing corrections that are applied to GRACE, including the GIA correction. In our earlier studies we showed that degree and order 1 terms result in a global mass balance of approximately 70 Gt/yr which is around 20% of the ocean signal determined by mass loss. This paper will re-evaluate the definition of the geo-center motion with the help of new GIA models such as ICE-6G and alternative models based on an Earth model that includes lateral heterogeneities. We will focus on the effect of degree 1 terms in the GIA models and the de-aliasing products in relation to sea level change estimates.