Speaker: Nicholas Foukal (WHOI)
Title: Ocean heat transport from the subtropical gyre to the subpolar gyre in the North Atlantic
For decades, the physical oceanographic and climate community has treated the Atlantic meridional overturning circulation (AMOC) and its associated meridional heat transport (MHT) as a source of low-frequency variability in the climate system. However, recent results from satellites, basin-wide in situ monitoring arrays, and a range of models have shown that even the AMOC has strong high-frequency variability that needs to be considered when interpreting long-term trends. In addition, it has been shown that the AMOC in the subtropics does not co-vary with the AMOC at subpolar latitudes on monthly to even decadal time scales. Thus a single measure of the AMOC is not sufficient to summarize its variability over the entire North Atlantic. In this talk, I will discuss a series of papers in which we attempt to bring the MHT literature up-to-date with these new results from the AMOC literature. How is heat conveyed from the subtropical Gulf Stream region to the eastern subpolar gyre? Does a coherent SST pathway exist? How does our recent understanding of a sub-surface connection from the subtropical gyre to the subpolar gyre influence how we expect the inter-gyre MHT to operate? We test a series of mechanisms put forth in the literature using satellite data and simulated Lagrangian trajectories, and then close a heat budget for the eastern subpolar gyre in two ocean circulation models. I will then discuss the implications of our results on seasonal-to-interannual climate predictability and on observed ocean temperature variability such as the warming hole in the subpolar North Atlantic.