Root mean square of SST anomaly difference (a) and mean SST difference (b) between the TOPAZ4 reanalysis and INTAROS-opt. Panels (c-e) are time series for the region near the Fram Strait (black box in panel (a)) from 1 September 2012 to 30 November 2012. Panel (c) shows sea ice changes due to the advective convergence term, the thermodynamic effect of the atmosphere, and the thermodynamic effect of the ocean (see legend in c). Panel (d) shows SIC from satellite observations (blue line), TOPAZ4 reanalysis (green line), and INTAROS-opt (black line). Panel (d) shows the mean SST based on the OI product in this study (Obs), INTAROS-opt, and the TOPAZ4 reanalysis (see the legend). Observation errors are shaded.