The Response of the Southern Ocean to Climatological Iceberg Freshwater Forcing

Antarctic icebergs, as a moving source of freshwater while drifting in the Southern Ocean, have been suggested to play a significant role in altering water masses and sea ice dynamics, especially during recent increases in Antarctic ice discharge. Many current climate models, however, misrepresent Antarctic iceberg melt by assuming it is released along the coast, largely due to the lack of comprehensive assessments that quantify the associated biases and capture the full impacts of this assumption on sea ice and ocean dynamics. In this study, we investigate how the spatial distribution of iceberg melt influences the Southern Ocean by implementing a recent simulation of iceberg melt pattern into a global ocean–sea ice model. Our results show that widespread iceberg melt decreases surface salinity and enhances stratification, which suppresses vertical convection and mixing. This, in turn, reduces upward heat transport, leading to subsurface heat accumulation, surface cooling, and enhanced formation of sea ice and Antarctic Bottom Water. Additionally, we emphasize the importance of incorporating a more realistic distribution of iceberg melt into ocean models, which can reduce the model bias of salinity and temperature climatology by ~ 30% compared with observations in the high latitudes of the Southern Ocean. Our results underscore the necessity of considering iceberg drifting pattern in climate/ocean models. Current models that neglect drifting icebergs should be interpreted by incorporating findings from this study.