Abstract

The efficiency of atmospheric CO2 storage by both the terrestrial biosphere and the ocean is expected to reduce in response to climate change. This would cause atmospheric CO2 to rise faster than expected from anthropogenic CO2 emissions alone. Using an ensemble of Earth System models, we show that the impact of climate-change on global air-sea CO2 flux varies both regionally and between the models. The Southern Ocean is one of the regions where the climate-carbon-cycle feedbacks can be largest and where they differ most between the models. I will demonstrate that our understanding of the processes driving the future evolution of the Southern Ocean CO2 flux is greatly improved by tracking the air-sea CO2 flux over regions constrained by evolving outcropping water-mass boundaries, rather than by fixed geographical boundaries. We isolate two geochemically-driven components—one due to rising atmospheric CO2 concentrations, and one due to localised chemical saturation. And, we isolate two climate-driven components—one due to changes in the outcrop surface areas of the water masses, and one due to the local impacts of climate-change.