COMBINATION OF SPACEBORNE, AIRBORNE AND SURFACE GRAVITY IN SUPPORT OF ARCTIC OCEAN SEA-ICE AND MDT MAPPING

摘要

Improved knowledge of the gravity field in the Arctic is a key to the utilization of satellite altimetry to determine sea-ice thickness and mean dynamic topography (MDT). In the paper we outline the construction of a new gravity field of the Arctic Ocean region, combining new GRACE and ICESat observations with earlier compilations of airborne, surface, and submarine gravity data from the Arctic Gravity Project. We compare the corresponding geoid model to a mean sea surface (MSS) model derived from ICESat lowest-level filtered laser altimetry and retracked radar altimetry, to allow for a consistent estimate of the Arctic Ocean MDT. Results are compared to oceanographic models, and show an overall absolute consistency is achieved at the decimeter-level. Arctic Ocean sea ice freeboard heights (and thus ice thickness) are an integral part of these investigations, and ICESat-derived freeboard heights show a good correlation to multi-year ice distribution as determined from Quikscat. The investigations represent the core of the ongoing ESA project "ArcGICE". One of its major objectives is to provide a practical algorithm for the estimation of sea surface heights including the associated errors. These parameters can further be used for example as a reference for Cryosat-2 measurements of sea ice freeboard. The ArcGICE study includes detailed error estimates and covariance studies, and it is clear that the inclusion of GOCE data will significantly enhance ice thickness and MDT mapping from e.g. CryoSat-2.