Combining ICESat Altimetry, GRACE Ocean Bottom Pressure, and In Situ Observations to Understand Recent Changes in Arctic Ocean Circulation

A three-way comparison among dynamic ocean topography (DOT) from ICESat altimetry and geodetic data, ocean bottom pressure (OBP) from the Gravity Recovery and Climate Experiment (GRACE), and in situ hydrographic measurements show that the ICESat-derived DOT and resultant surface currents are representative of the circulation relative to the 500 dbar level derived from hydrography. Furthermore, subtracting ICESat DOT from GRACE OBP gives a good representation of the steric pressure and freshwater content of the Arctic Ocean. The trends in ICESat DOT and GRACE OBP in the Arctic Ocean from 2005 to 2008 indicate an anticyclonic spin up in the Beaufort Sea and cyclonic spin up along the Russian shelf break. The pattern is ideal for diverting freshwater from the Russian rivers eastward and collecting it in the Beaufort Gyre. Annual averages suggest the shift in freshwater trajectory was related to an increase in the Arctic Oscillation index starting in 2007.