Regional Feedbacks Between the Ocean and the Atmosphere in the North Atlantic

The ocean acts to buffer changes in the climate system with the upper 800m of the ocean taking up more than 90% of the excess heat in the climate system. On interannual time scales, surface heat fluxes damp the low-frequency heat content anomalies in some areas of the ocean where heat anomalies can be released back to the atmosphere. Analysis of satellite altimetry observations of SSH (sea surface height) as a proxy for upper ocean heat content and net suface heat flux from OAFlux (Objectively Analyzed air-sea fluxes) 993-2009 allows the identification of the times of the year and the locations in the North Atlantic where heat content anomalies are driving surface fluxes. Heat content has six month persistence while surface flux has at most one month persistence. Times series for each month of the year at each location are created to examine the lagged correlation between upper ocean heat content and the net surface heat fluxes. The heat content anomalies south of the Gulf Stream in June through November are negatively correlated with surface fluxes in November with a warmer ocean leading to surface fluxes out of the ocean. In this region, the mixed-layer by November reaches 100 m and the previous summer's stored heat is accessible to the atmosphere. The high correlations continue into December and January. By February, the correlation is no longer significant. In the region between 15N and 40N off the coast of Africa, January through May heat content are anti-correlated with surface fluxes in May. In May at this location, the climatological sensible heat flux is into the ocean, the planetary boundary layer is stable and stratocumulus clouds are common. Significant correlations in the summer are also found in the central subpolar North Atlantic. This analysis suggests that locally ocean heat content anomalies can feedback to the atmosphere, but only during certain times of the year. The impact on the atmosphere in late fall and early winter can influence of the atmosphere outside of the planetary boundary layer, although the magnitude of the signal is likely small compared to the intrinsic atmospheric variability. In the regions with summer feedbacks, the impact of the heat released is likely felt only in the planetary boundary layer, although there could be an impact on the radiation balance by ocean forced changes in stratocumulus clouds.