Improved polar ocean surface wave height and surface elevation data from CryoSat-2 using a semi-analytical physical retracker

Abstract:

The Arctic Ocean has seen rapid changes in climate over the past decades resulting in a reduction in summer sea ice extent. This reduction has resulted in a greater expanse of open ocean potentially driving changes in the atmosphere and ocean interaction in this region and globally. The CryoSat-2 satellite with its SAR (Synthetic Aperture Radar) Interferometric Radar Altimeter (SIRAL) instrument and polar orbit gives us state of the art Arctic and Antarctic data to investigate the polar oceans for the past decade. The radar echoes are analyzed with a semi-analytical waveform model of the echo power convolution in open ocean conditions in both SAR and LRM modes to retrieve along-track amplitude, epoch, surface elevation deviation, and significant wave height.

The surface elevation from the open ocean and from leads, cracks in the sea ice cover, can be combined with Earth geoid data to give the dynamic ocean topography and geostrophic ocean surface currents for the entire Arctic Ocean. Here we present data for the entire CryoSat-2 record to date, showing the changes and average climatology of ocean surface waves and surface geostrophic currents. We compare our open ocean SAR and LRM significant wave height data to existing datasets and in-situ buoy observations to focus on the role of SAR and LRM modes and the benefits of a full echo power convolution. Particular benefits are shown in the seasonally ice-covered seas of the Arctic Ocean, showing the wave state of the increasingly exposed open ocean.