High-latitude Southern Ocean warming hotspot induced by ocean mesoscale eddies

Abstract

The high-latitude (poleward of ~50° S) Southern Ocean is recognized as a region of delayed surface warming during periods of transient CO2 increase; however, the uniformity of this pattern remains unclear. Here, based on observational and reanalysis datasets, we identify locally (50° S–61° S, 80° E–130° E) accelerated surface warming of 1.5 °C per century for 1982–2023 in the high-latitude Indian Ocean sector. This warming rate is three times the average over the high-latitude Southern Ocean (0.5 °C per century) and close to the global mean of 1.6 °C per century. Analysis of a state-of-the-art high-resolution climate simulation suggests that the hotspot warming is primarily attributed to increased upward heat transport by mesoscale eddies in response to an enhanced Antarctic Circumpolar Current under anthropogenic climate change. Our findings underscore the important role of mesoscale eddies in regulating Southern Ocean warming and the need for their faithful representation in models to ensure reliable projections of future climate change. The Southern Ocean is important for anthropogenic heat uptake, and this regional analysis shows an area with enhanced warming in the high-latitude Indian sector. Model analyses indicate that mesoscale eddies drive upward heat transport, linked to a strengthening of the Antarctic Circumpolar Current.