The DTU21 Global Mean Sea Surface and First Evaluation

Abstract. A new Mean Sea Surface (MSS) called DTU21MSS for referencing sea level anomalies from satellite altimetry is introduced in this paper and a suite of evaluations are performed. One of the reasons for updating the existing Mean Sea Surface is the fact, that during the last 6 years nearly three times as much data have been made available by the space agencies, resulting in more than 15 years of altimetry from Long Repeat Orbits or Geodetic Missions. This includes the two interleaved long repeat cycles of Jason-2 with a systematic cross-track distance as low as 4 km.

A new processing chain with updated filtering and editing has been implemented for DTU21MSS. This way, the DTU21MSS has been computed from 2 Hz altimetry in contrast to the former DTU15MSS/DTU18MSS which were computed from 1 Hz altimetry. The new DTU21MSS is computed over the same 20-year averaging time from 1993.01.01 to 2012.12.31 with a well-specified central time of 2003.01.01 and is available from the following site; (https://doi.org/10.11583/DTU.19383221.v1, Andersen, 2022)

Cryosat-2 employs SAR and SARin modes in a large part of the Arctic Ocean due to the presence of sea ice. For SAR and SARin mode data we applied the SAMOSA+ physical retracking in order to make it compatible with the physical retracker used for conventional Low-Resolution Mode data in other parts of the ocean.