Oceanic Maintenance of Atmospheric Blocking

In recent years the understanding of atmospheric blocking has changed from solely a dry phenomena to one that includes moist processes. The primary source of that moisture, the ocean, has, until recently, been neglected as a driver of this basin scale structure. Here, the connection between atmospheric blocking over the North Atlantic and the diabatic influence of the Gulf Stream was investigated using potential vorticity diagnostics. In line with previous research, the reliance atmospheric blocking has on latent heat fluxes over the Gulf Stream and its extension, for induction and maintenance, was shown to be significant. It was shown that not only is it more likely for a North Atlantic block to occur after significant surface latent heat fluxes over the Gulf Stream and its extension, but the resulting block is likely to be anchored on the western flank of the Atlantic, making it more stationary and hence, more impactful. Additionally, blocks that have a longer duration were highly associated with surface latent heat fluxes over the western boundary current, while shorter blocks were not, indicating a positive feedback from the oceanic mesoscale phenomena onto this basin scale structure. Finally, the frequency of the block was seen to correspond to the amount of surplus heat content in the western boundary currents prior to the blocking event which, in the North Atlantic, had leading order dependence on the heat transport via the Gulf Stream.