Differences Between ICESat and CryoSat-2 Sea Ice Thicknesses Over the Arctic: Consequences for Analyzing the Ice Volume Trend

Abstract

Two sources of readily available and non-overlapping space-borne data on sea ice thickness over the Arctic (i.e., Ice, Cloud, and land Elevation Satellite [ICESat] and CryoSat-2 [CS2]) were compared using overlapping thermal microwave radiometer data to examine their respective differences. As a bridge connecting these two data sets, data on the vertically polarized emissivity difference between 10.65 and 18.7 GHz derived from the Advanced Microwave Sounding Radiometer were related to ICESat and CS2 thickness values via regression. The results indicate that there are substantial and systematic differences in the ice thickness between these two data sets over the Arctic; ICESat ice thickness was systematically lower than that of CS2 by ~50 cm, compared to ice thickness from Operation IceBridge and upper looking sonar data. The CS2 thickness observed later than that of ICESat was found to be thicker, contradicting the thinning expected under global warming conditions. Correcting for the 50-cm difference between ICESat or CS2 data revealed trends in ice volume that are consistent with the expected and modeled declines in the Pan-Arctic Ice-Ocean Modeling and Assimilation System data, further corroborating the 50 cm of relative bias observed between the two data sets.