CoAuthors

Kyla Drushka (University of Washington, USA); LuAnne Thompson (University of Washington, USA); Dewi Le Bars (KNMI, Netherlands); Elaine McDonagh (National Oceanography Centre, United Kingdom)

Recent measurements of the strength of the Atlantic overturning circulation at 26N show a one-year drop and partial recovery amid a gradual weakening. To examine the extent and impact of the slowdown on basin wide heat and freshwater transports for 2004-2012 a box model that assimilates hydrographic and satellite observations is used to estimate heat transport (HTC) and freshwater convergence (FWC) as residuals of the heat and freshwater budgets. Using an independent transport estimate, convergences are converted to transports, which show a high level of spatial coherence. The similarity between Atlantic heat transport and the Agulhas Leakage suggests that it is the source of the heat transport anomalies. The freshwater budget in the North Atlantic is dominated by a decrease in freshwater flux. The increasing salinity during the slowdown supports modeling studies that show that heat, not freshwater, drives trends in the overturning circulation in a warming climate.