A new mesoscale Regional Arctic ocean/sea ice REanalysis (RARE) is Used to Examine Climate Variability

First results are presented for a new eddy-resolving Regional Arctic ocean/sea ice REanalysis (RARE), whose domain extends poleward from the subpolar North Atlantic and the Bering Sea and spans the central basin. The system is built on GFDL MOM numerics with 3-4 km horizontal and 1 m nearsurface vertical resolution, with ECMWF ERA5 hourly surface forcings, and monthly continental discharge from a combination of in situ and satellite sources. Constraining observations are based on the NOAA NCEI hydrography data set, the NOAA STAR nearsurface temperature observation sets, and satellite ice thickness and extent, with assimilation algorithms borrowed from the Simple Ocean Data Assimilation v3 (SODA3). Two system configurations are described. In the first the ocean state is constrained by observations only in the subpolar gyre and the Bering Sea, allowing the Arctic Ocean/sea ice system to evolve in response to changes in the North Atlantic and North Pacific, as well as local meteorology. In the second configuration the ocean/sea ice system is fully constrained, providing an historical reanalysis of the ocean/sea ice system. The first half of the talk will describe this new system and present a comparison of time mean circulation and water mass properties to the 1/4-degree SODA3 reanalysis system. This comparison highlights the importance of both horizontal and vertical resolution.

A striking feature of the physical oceanography of the Nordic and Barents Seas is the appearance of strong interannual to decadal variability, which is carried downstream into the central basin. The second half of the talk will explore RARE by applying it to examine the movement and transformations of anomalous water during the 2000s. The regional model configuration allows us to separate contributions of input of anomalous subpolar North Atlantic water and the changing regional meteorology on these water masses.