The Southern Ocean Freshwater release model experiments Initiative (SOFIA): Scientific objectives and experimental design

Abstract. As the climate warms, the grounded ice sheet and floating ice shelves surrounding Antarctica are losing mass at an increasing rate and injecting the resulting meltwater into the Southern Ocean. This freshwater input could feed back onto climate change, particularly since the Southern Ocean is a key contributor to global heat and carbon uptake. Nonetheless, almost all existing coupled climate models have fixed ice sheets, and lack the physics required to represent the dominant sources of Antarctic melt. These missing ice dynamics represent a key uncertainty that is unaccounted for in current global climate change projections. Previous studies have inserted additional Antarctic meltwater into models, demonstrating that it can alter Southern Ocean stratification, circulation, and sea ice, as well as influence remote atmospheric circulation, tropical precipitation, and global temperature. However, these previous studies have used widely varying rates of freshwater forcing, been conducted using different climate models and configurations, and have reached differing conclusions on the magnitude of meltwater-climate feedbacks. The Southern Ocean Freshwater release model experiments InitiAtive (SOFIA) brings together a team of scientists to quantify the climate system response to Antarctic meltwater input. In this paper, we summarize the state of knowledge on meltwater discharge from the Antarctic ice sheet and ice shelves to the Southern Ocean and explain the scientific objectives of our initiative. We propose a series of coupled and ocean/sea-ice model experiments, including idealized meltwater experiments, historical experiments with observationally consistent meltwater input, and future scenarios driven by meltwater inputs derived from stand-alone ice sheet models. Through coordinating a multi-model ensemble of simulations, with data housed in a common archive, SOFIA will be able to produce a consistent estimate of the climate system response to Antarctic meltwater, as well as the uncertainty of this response.