Towards constraining ocean estimates in ice-covered regions using sea level altimetry data

Estimates of ice-covered oceans are difficult to constrain using in situ observations, particularly if one needs broad spatiotemporal coverage of subsurface properties. Here we explore the value of sea level (\slv) data from the laser altimeter on ICESat-2 and multi-mission radar altimeter products distributed by the Archiving, Validation and Interpretation of Satellite Oceanographic (AVISO) data center for constraining the 3-dimensional ocean-sea ice state produced by the project for Estimating the Circulation and Climate of the Ocean (ECCO). Both Arctic and Antarctic ice-covered regions are examined. A recent ECCO solution indicates substantial baroclinic variability at seasonal and longer timescales, pointing to the potential usefulness of adding \slv ~constraints to the bottom pressure constraints already implemented in ECCO. Comparisons of ICESat-2 and AVISO \slv ~products, as well as corresponding bottom pressure data, reveal relatively noisier ICESat-2 fields compared to AVISO. The AVISO fields are also in closer agreement with the ECCO solution for both Arctic and Antarctic regions. Comparisons of \slv ~products and ECCO lead to estimates of data uncertainty that are used to assess ECCO-data differences. Results point to the potential impact of \slv ~data constraints, particularly for the case of AVISO products, on future ECCO estimates. Stronger effects are found for the Arctic, where signal-to-noise ratios of the \slv ~data are higher than in southern latitudes.