Arctic Surface Water Mass Variations from GRACE Gravimetry versus Combined Satellite Altimetry and Ocean Temperature.

The Arctic is an extremely challenging region for the use of remote sensing for ocean studies. Cryosat-2 SAR altimetry and GRACE satellite gradiometry is improving this situation. However direct estimation of Arctic surface water mass variations is not straight forward. Satellite altimetry is degraded due to the presence of sea ice within the radar footprint and grace gradiometry is severely limited in spatial resolution. We have processed 5 years of Cryosat-2 data quantified as either Lead or Ocean data within the Cryosat-2 SAR mask in the Arctic Ocean and carefully reprocessing and reedited conventional altimetry from ERS-1/ERS-2 and Envisat. So we now have 13 years of data from both GRACE and satellite altimetry. Initial investigations over the first 10 years yield high similarity of the estimates in water mass variations between GRACE on the one side and satellite altimetry + surface temperature from modelling. During the 2003 to 2011 period we found a decrease in surface water mass from both satellite altimetry and GRACE gradiometry, however the large scale patterns were slightly different. The implication of this approach indicates that the sea level budget for the Arctic Ocean can actually be closed reasonable well using remote sensing.