Arctic sea ice thickness retrievals from CryoSat-2: seasonal and interannual comparisons of three different products

ABSTRACT

As a fundamental climate state variable, sea ice thickness (SIT) has exhibited a declining trend over the past five decades. Here, we present a quantitative comparison of three CryoSat-2 (CS-2) SIT products from the Alfred-Wegener-Institute (AWI), the National Snow and Ice Data Centre (NSIDC), and the European Space Agency (ESA) during the growth season (October to April) from 2010 to 2018 with Operation IceBridge (OIB) data. The results show that the NSIDC SIT product is the closest to the OIB SIT, with ESA SIT exhibiting the highest bias. During each growth season, the SIT differences between AWI and NSIDC gradually decrease, while such differences between ESA and NSIDC increase for first-year ice (FYI) and decrease then increase for multiyear ice (MYI). The difference between ESA and NSIDC is larger than that between AWI and NSIDC. Moreover, the rather large differences between ESA and NSIDC are mainly located in thin ice areas. Consistent to SIT comparative results, sea ice freeboard for ESA is higher than that for OIB, AWI and NSIDC, especially FYI freeboard. Sea ice freeboard for NSIDC is the closest to that for OIB. The comparative results indicate that the sources of the differences in SIT between the products mainly originate from the sea ice density and freeboard retrieval methods. The choices of different waveform retrackers and threshold assignments significantly influence the MYI freeboard retrievals due to the relatively thick snow depth and high surface roughness over MYI.

Acknowledgements

The sea ice freeboard data for CryoSat-2 Level 2I are provided by the European Space Agency (http://science-pds.cryosat.esa.int/). The CryoSat-2 sea ice thickness, snow depth and snow density data are from the Alfred-Wegener-Institute (https://www.meereisportal.de/en/). The sea ice type data are from the Ocean and Sea Ice Satellite Application Facility (http://www.osi-saf.org/). The CryoSat-2 sea ice thickness and sea ice data for the Operation IceBridge are from the National Snow and Ice Data Center (http://nsidc.org).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is supported financially by the Programs for National Key R&D Program of China [2018YFC1407200, 2018YFC1407203] and National Natural Science Foundation of China [No. 41830105].