Wind-Driven Ocean Circulation Changes Can Amplify Future Cooling of the North Atlantic Warming Hole

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Abstract The North Atlantic warming hole is an area of relative cooling in the North Atlantic subpolar gyre. Observations and models have suggested numerous causes of the warming hole, including a role for wind-driven ocean circulation changes. We investigate the role of wind-driven ocean circulation changes on the development and projected future of the North Atlantic warming hole by comparing two ensembles within the Community Earth System Model, version 2 (CESM2). One ensemble includes wind-driven ocean circulation changes, while the other does not. The difference between the ensemble means isolates the role of wind-driven ocean circulation changes on the externally forced North Atlantic warming hole. We find that wind-driven ocean circulation changes do not alter the timing of the formation of an externally forced warming hole. However, anthropogenic changes to the near-surface winds lead to enhanced upwelling near Greenland, and wind stress changes enable a positive feedback loop that relies on changes to mechanical stirring. These mechanisms amplify the cooling in the high latitude North Atlantic and lead to increased sea level pressure and reduced precipitation near the southern tip of Greenland. Thus, changes to wind-driven ocean circulation are a crucial component of future changes in North Atlantic climate. Improved understanding of ocean–atmosphere coupling in this region will improve projections of sea surface temperatures and associated atmospheric impacts. Significance Statement The purpose of this study is to quantify the role that changes to the wind-driven component of ocean circulation have on future sea surface temperatures in the North Atlantic subpolar gyre region. This region has warmed less than the global average, often referred to as a “warming hole.” We use a targeted climate model experiment to demonstrate that wind-driven ocean circulation changes do not cause the modeled North Atlantic warming hole. However, wind-driven ocean circulation changes alter the warming hole beginning in 2040. This demonstrates that monitoring and understanding changes to the surface winds and ocean currents in the North Atlantic is important for understanding future climate changes in the region.