Marine heatwaves suppress ocean circulation and large vortices in the Gulf of Alaska

Large-scale anticyclonic vortices forming along the Gulf of Alaska continental slope serve as fertile ecosystems for marine life, significantly shaping the distribution of primary productivity, with 40–80% of the gulf’s open ocean surface chlorophyll-a concentrated in their cores. Between 2013 and 2023, Alaska experienced some of the largest and longest marine heatwaves ever recorded in the world’s oceans, persistently altering its ecosystem and fisheries. Here, using 30 years of satellite and reanalysis data, we find that the coastal upwelling atmospheric forcing conditions associated with the heatwaves have also significantly suppressed the Gulf of Alaska’s ocean circulation and the formation of large anticyclones. Climate model simulations spanning from 1850 to 2100 suggest that future changes in the Aleutian Low pressure system will lead to a 60% increase in upwelling extremes (>2 standard deviations), further weakening the ocean anticyclones. However, large uncertainties remain in the mechanisms controlling the Aleutian Low’s response to climate forcing in the models. Between 2013 to 2023, marine heatwaves and changing atmospheric conditions have suppressed ocean circulation and anticyclonic vortices formation in the Gulf of Alaska, with future climate changes likely to intensify this trend, according to results from 30 years of satellite and reanalysis data as well as climate model simulations.