Assimilation of sea ice thickness derived from CryoSat-2 along-track freeboard measurements into the Met Office's Forecast Ocean Assimilation Model (FOAM)

Abstract. The feasibility of assimilating sea ice thickness (SIT) observations derived from CryoSat-2 along-track measurements freeboard is successfully demonstrated using a 3D-Var assimilation scheme, NEMOVAR, within the Met Office's global, coupled ocean–sea-ice model, Forecast Ocean Assimilation Model (FOAM). Arctic are produced by Centre for Polar Observation and Modelling (CPOM) converted to SIT FOAM modelled snow depth. This first time have been used in this way, with other centres gridded temporally averaged observations. leads improvements analysis forecast fields generated FOAM, particularly Canadian Arctic. Arctic-wide observation-minus-background statistics 2015–2017 show 0.75 m mean difference 0.41 root-mean-square (RMSD) freeze-up period 0.46 0.33 RMSD break-up period. Validation against independent springtime situ NASA Operation IceBridge (OIB) shows improvement 0.61 (0.42 RMSD) compared control without assimilation. Similar seen 5 d forecast. Beaufort Gyre Exploration Project (BGEP) draft does not an improvement, since assimilated compare similarly model region. Comparison airborne electromagnetic induction (Air-EM) combined depth poorer results control, despite covering similar locations OIB BGEP datasets. may be evidence sampling uncertainty matchups Air-EM validation dataset, owing limited number available over interest. also noise or uncertainties depth, observations, data validation. could improved upgrading observation Despite lack summer due detrimental effect melt ponds on retrievals, it shown that able retain field throughout months prior, wintertime regional July concentration (SIC) % European sector, slower thicker ice.