Revised constraints on the final stages of the last deglaciation from high-resolution sea-level observations

Abstract

The rapid transformation of the ocean-atmosphere-cryosphere system during the last deglaciation serves as a potential model for climate change during this century and beyond. Within this context, sea-level change can be viewed as the connecting tissue, but the limited resolution of relative sea-level (RSL) records has hindered progress toward closing the ice sheet–sea level budget since the Last Glacial Maximum, the partitioning of ice melt from different sources, and assessing the role of freshwater forcing in abrupt climate change. Here we present a new RSL record from the Mississippi Delta stretching back to 11 ka and combine it with the best available published RSL data worldwide for the final episode of the last deglaciation (9-7 ka). Glacial isostatic adjustment (GIA) modelling shows that these precise data constraints demand a North American ice melt of about 14 m sea-level equivalent (SLE) during this time, 4-10 m greater than previously estimated. Our results call for a major revision of the North American deglacial ice history and our findings demonstrate the utility of high-resolution RSL observations as a pathway towards closing the ice budget of the last deglaciation and improving our understanding of the ocean-atmosphere-cryosphere system during rapid climate change.