Mesoscale Ocean Processes: The Critical Role of Stratification in the Icelandic Region

The oceanic region around Iceland, a key component of the Atlantic meridional overturning circulation, plays a critical role in global climate through its complex system of surface and subsurface currents. Using high-resolution Surface Water and Ocean Topography (SWOT) satellite data, in situ observations, and idealized numerical simulations, this study reveals two distinct dynamical regimes in this region. South of Iceland, the mesoscale eddy field is energetic. In contrast, north of Iceland, the strong shallow stratification inhibits baroclinic instability and eddy generation, resulting in a low-energy “eddy desert”—a phenomenon observed synoptically for the first time at SWOT's unprecedented resolution. This new understanding of Iceland's dynamical regimes highlights the role of stratification in mesoscale variability. Analyzing Biogeochemical-Argo float data, it also suggests an impact of mesoscale regimes on the local biogeochemical cycles, with implications for primary production and carbon cycling as stratification patterns shift with climate change.