Antarctic Ice Sheet Freshwater Discharge Drives Substantial Southern Ocean Changes Over the 21st Century

Multidecadal satellite observations indicate that the Antarctic Ice Sheet (AIS) is losing mass at an accelerating rate, which has the potential to impact many aspects of the climate system. While previous studies demonstrated the importance of AIS freshwater (FW) discharge for regional and global climate processes using climate model experiments, many have applied unrealistic FW forcings. Here, we explore potential Southern Ocean (SO) impacts of realistic AIS mass loss over the 21st century in the Community Earth System Model version 2 by applying observation-based historical and ice sheet model-based future AIS FW forcing. The added FW reduces wintertime deep convective area by 72% while retaining 83% more sea ice. Congruent with other studies, we find the increased FW discharge extensively impacts local and remote SO surface and subsurface temperature and stratification. These results demonstrate the necessity of accounting for AIS mass loss in global climate models for projecting future climate. We know from several decades of satellite observations that the Antarctic Ice Sheet is losing mass at an accelerating rate. This accelerated mass loss (solid and liquid FW) is often poorly represented-if at all-in global climate models (GCM) and previous studies indicate that even a simple representation of mass loss can have profound climate impacts. Here, we apply a more realistic (in space and time) representation of Antarctic mass loss to a GCM. We find that the added FW leads to more retention of Antarctic sea ice, a decline in wintertime convection of surface waters to the interior ocean, a cooler surface but warmer interior ocean, and a more strongly stratified upper ocean. As such, we argue that properly accounting for Antarctic mass loss in GCMs is imperative for accurately projecting long-term future climate change. We explore impacts of realistic Antarctic Ice Sheet (AIS) freshwater discharge on the Southern Ocean (SO) using a state-of-the-art climate modelAIS discharge drives drastic changes in SO stratification, winter deep convection, surface and interior temperature, and sea iceOur results suggest that regional AIS discharge can have far-reaching impacts on the SO that can feedback on the climate system

Automated summary

Long-term satellite observations show that the Antarctic Ice Sheet is losing mass at an accelerating rate, which has significant implications for the climate system. This study investigates the potential impacts of realistic Antarctic mass loss on the Southern Ocean using a state-of-the-art climate model. The results demonstrate the importance of accounting for Antarctic mass loss in global climate models for accurate projections of future climate.