ColdBlobMIP: A Multi-Model Assessment of the Atmospheric Response to the North Atlantic Warming Hole

Observations of sea surface temperature reveal a region of relative cooling in the subpolar North Atlantic commonly known as the North Atlantic warming hole (NAWH) or “cold blob.” While the origin of the NAWH has been extensively debated, its direct impact on the atmosphere has only recently garnered attention. Here, we present ColdBlobMIP, an atmospheric model intercomparison project in which 15 models from four institutions simulate the atmospheric response to the observed NAWH. The ensemble mean reveals robust and significant changes in surface wind and clouds, the latter imparting a shortwave forcing of −3.6 W/m² over the NAWH in summer—indicative of a positive feedback. Despite agreement on certain aspects of the response, the models exhibit diverse behavior that is diagnosed from their surface pressure response. Overall, ColdBlobMIP attributes a relatively modest response to the NAWH, highlighting the critical dependence of large-scale midlatitude air-sea interactions on model structure and configuration.