Arctic Ocean-Sea ice reanalysis for the period 2007-2016 using the adjoint method
We present an Arctic ocean-sea ice reanalysis covering the period 2007-2016 based on the adjoint approach of the ECCO consortium. The spatiotemporal variation of Arctic sea surface temperature (SST), sea ice concentration (SIC), and sea ice thickness (SIT) are substantially improved after the assimilation of the ocean and sea ice observations. By assimilating additional WOA18 hydrographic data, the freshwater content of the Canadian Basin becomes closer to the observations and translates into changes of the ocean circulation and of transports through the Fram and Davis straits. The new reanalysis compares well with previous filter-based (TOPAZ4) and nudging-based (PIOMAS) reanalyses regarding SIC and SST. However, the mean state and variability of the freshwater content and the transport properties of our reanalysis are different from the TOPAZ4 reanalysis, likely due to a lack of hydrographic observations.