<p>Dense shelf water (DSW) overflows around Antarctica leads to the formation of antarctic bottom water, thereby driving the lower cell of global overturning circulation. Some previous ocean modelling studies simulate the effects of future Antarctic glacial meltwater fluxes by adding prescribed freshwater runoff flux from the Antarctic continent. They conclude that increased meltwater is the key concern for a&#xa0;weakening of DSW overflows and may be responsible for a collapse of the lower cell circulation by the mid-twenty-first century. In this study, we analyze the response of DSW overflows to anthropogenic climate change in&#xa0;the high-resolution (0.1° ocean model) Community Earth System Model CESM1.3. In this climate model, there is no coupled dynamic ice-sheet component, and not added in prescribed glacial meltwater (although the Antarctic continent runoff is increasing under climate change forcing). Our results show that under a high-emission scenario (the Representative Concentration Pathway 8.5), the formation of DSW gradually weakens and the overflows shut down around 2040, owing to the freshening of the Antarctic shelf water. We find that over the Antarctic shelf, a reduction in sea-ice brine rejection is the dominant factor in driving the changing surface freshwater forcing (58%), while the freshwater flux from the Antarctic continent plays a secondary role (26%) and precipitation minus evaporation plays a further minor role (16%). The slowdown and eventual cessation of DSW overflow greatly weakens the lower cell of global overturning circulation. Our results highlight the critical importance of reducing the uncertainty in projected freshwater forcing related to sea ice on the Antarctic shelf, in addition to reducing the uncertainty in the glacial meltwater forcing. This study may help provide a more comprehensive understanding and improved future projections of the DSW overflow in future warming climates.</p>