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Abstract:
Ice sheet melting into the Southern Ocean increases the upper ocean stratification and sea ice production, and thus can change the formation and properties of the Antarctic Bottom Water (AABW). Indeed, both the AABW freshening, and sea ice expansion have been observed in the Southern Ocean from the late 1980s until 2014, raising the question as to what extent increasing ice sheet melting could explain the observed patterns. However, it is challenging to address this question using observations due to the scarcity of direct observations along the Antarctic shelf and slope. Until recently, most ocean models could not form AABW efficiently along the Antarctic shelf either, precluding further investigation. In this study, we use a global ocean & sea ice model to explore how increasing ice sheet melting can alter the AABW properties and sea ice production Here, we explore three observation-based ice sheet melting scenarios based on historical observations (i.e., 5, 12, and 18%) for the historical period of 1958-2017. Our model results indicate a 12% increase in ice sheet melting may lead to a freshening of AABW at a rate similar to that observed since the early 1980s. This suggests that the observed AABW freshening could be driven by the increasing Antarctic meltwater discharge. Sea ice did not show any robust response to any of the three ice sheet melting scenarios.
