Abstract
The Southern Ocean is an important driver for the meridional overturning circulation and it plays a major role in the transport of heat, the uptake of carbon and the global climate system. The strength of the global abyssal overturning circulation is proportional to the rate at which Antarctic bottom water (AABW) is produced and this production rate is determined by net surface buoyancy loss. Due to the low thermal expansion of seawater at low temperatures, buoyancy loss in polar waters is strongly dominated by the surface freshwater flux rather than heat flux. Data-assimilating models show that sea-ice formation and melting are the most important processes for water-mass formation over the Southern Ocean, followed by precipitation. Even though glacial melt is relatively small in magnitude, it is located spatially very close to convection areas, where it may also have an influence on dense water formation. Furthermore, ice shelves can contribute to the freshwater flux both directly by meltwater input, and indirectly by impacting stratification and circulation in ways that feedback on sea-ice formation and melt. Recently, the Department of Energy (DOE) has developed a new global coupled climate model, the Energy Exascale Earth System Model (E3SM) version 1. Using coupled and ocean/sea-ice stand-alone simulations from E3SM, we analyze the impacts of glacial melt over the Southern Ocean on water-mass transformation/formation. Both simulations show that the freshwater flux from land ice to the ocean increase upwelling water as a direct impact and that it can also affect water-mass transformation caused by sea-ice formation as an indirect impact.