Review of Radar Altimetry Techniques over the Arctic Ocean: Recent Progress and Future Opportunities for Sea Level and Sea Ice Research

Abstract. There are numerous needs for monitoring sea level and sea ice in the Arctic, ranging from concern about changes in ice cover being both an indicator and a driver of long-term climate change to shipping interest in alternative routes and the associated risks to the safety of vessels and crew. Furthermore, sea level relative to the geoid allows us to quantify the geostrophic circulation, including any changes in the flow. Radar altimeters provide an important means of quantifying changes in sea level and sea-ice thickness, although there are increased complexities in the interpretation of their data over such a variable surface. This paper reviews the techniques for deriving useful geophysical information over a mix of leads and ice floes, covering the approaches for both conventional (low rate mode) altimetry and the newer delay-Doppler (Synthetic Aperture Radar) instruments. It discusses the challenges in discriminating the returns from different surfaces, the retracking approaches and the corrections required. The review finishes with a look ahead to how new technologies, analyses and understanding may be expected to improve the monitoring in this critical environment.