Arctic Dynamic Topography and Surface Currents from Cryosat-2

Abstract:

The Arctic Ocean is known to be a region of significance in global climate, and has been observed to undergo drastic changes in recent decades. As research continues to understand the Arctic and the interaction of atmosphere, ice & ocean, a key area of study is ocean circulation – the investigation of which has traditionally been hampered by the region’s harsh and ice-covered nature. However with the advent of polar altimetry and the development of lead retracking, we may draw back the veil of sea ice and study the ocean beneath.

We use UCL’s well-developed sea ice retracking techniques to acquire sea surface height (SSH) measurements at leads across the Arctic. These data are used to produce a sea surface field, which is combined with the geoid to calculate dynamic topography and associated geostrophic currents. By adjusting the processing of SSH measurements we may examine surface currents on different time scales, from the multi-year mean state to annual and monthly variations.

We demonstrate the major improvement in coverage and resolution offered by Cryosat-2, as well as comparison against in-situ data. We show the variations in currents visible on different time scales, and discuss the considerations of processing data on these time scales with reference to Cryosat’s ground track/sampling pattern. We examine the potential effect of irregular distributions of leads, and the significance of any bias introduced by melt ponds in summer. We also show the improvements offered by using a combined (rather than satellite-only) geoid solution, and the caveats thereof. Finally, we look to methods of improving Arctic dynamic topography products in the future.