Thermal Rossby waves explain multidecadal upper ocean heat content variability in the Subpolar North Atlantic

It is important to understanding the mechanism behind multidecadal changes in North Atlantic ocean heat storage as these directly impact the climate of the surrounding continents. We construct a multidecadal upper ocean heat budget for the North Atlantic for the period 1950 to 2020 based on multiple observational datasets and a state of the art forced global ocean model. On multidecadal timescales ocean heat transport convergence is the dominant term in all regions of the North Atlantic. In the subpolar region (north of 45N) the heat transport convergence is largely explained by anomalous geostrophic currents acting on the mean temperature gradient. The timescale and spatial distribution of the anomalous geostrophic currents are consistent with basin scale ‘thermal’ Rossby waves propagating westwards/northwestwards in the subpolar gyre. Using a forced ocean model we link the ocean heat transport convergence with variations in the Atlantic Meridional Overturning Circulation.
The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)