OCES Departmental Seminar: Future Response of the Southern Ocean to Climate Change

The Southern Ocean has undergone significant climate-related changes over recent decades, including westerly wind intensification, atmospheric warming and continental glacial melt. The relative importance of forcing components that govern the deep Southern Ocean response to climate-related changes remains unclear, with modern day coupled climate models exhibiting biases in this region. By an intermodel comparison using a global ocean–sea ice model at two horizontal resolutions: nominally, 1° and 0.1°, it suggests that the ocean model response over the Southern Ocean depends on the model resolution. The 0.1° model shows better vertical distribution of zonal-mean ocean temperature, which turns out to be critical for the ocean stratification and ocean heat transport. Using the high-resolution model at 0.1° forced by recent and projected climate change, we further assess how projected changes in glacial melt, winds, and surface warming will affect abyssal ventilation. We find that glacial melt as the most critical factor in controlling future abyssal warming and ventilation changes. In contrast, wind and thermal forcing has little impact on the export, properties, age, and volume of Antarctic Bottom Water. Our results show a profound reorganization of the overturning circulation in the Southern Ocean over the next 30 years. Abyssal warming is also projected to accelerate with an increase of ~0.2°C around the Antarctic abyss.