Comparison of GRACE with In Situ Ocean Bottom Pressure and Hydrography in the North Pole Region

We this project will compare in situ measurements of ocean bottom pressure and hydrography with GRACE estimates of time-varying ocean bottom pressure. Arctic Bottom Pressure Recorders have been deployed and extensive hydrographic measurements have been made under other projects. Comparisons with some of these measurements suggest that GRACE can provide sorely needed large-scale, continuous information on the changing Arctic Ocean circulation. Our North Pole in situ measurements are particularly useful for GRACE validation because the GRACE footprint passes over the North Pole more frequently than any other ocean location on earth, making comparisons there robust. GRACE appears to provide our first basin-wide maps of how the Arctic Ocean circulation has been returning from a cyclonic pattern that pertained in the 1990s, to a more anticyclonic pre-1990 pattern. We will learn the impact of high frequency ocean variability on the accuracy and interpretation of GRACE, and we will assess and utilize the interpretation of long-term GRACE observations in terms of variability in the Arctic Ocean environment.