Deglacial Thinning of the Laurentide Ice Sheet in the Adirondack Mountains, New York, USA, Revealed by ³⁶Cl Exposure Dating

Future changes in sea level will largely be dictated by changes in the world's ice sheets. Yet the magnitude and rate at which these ice sheets will respond to climate change remain uncertain, necessitating a deeper investigation into past ice sheet-climate interactions. Numerous studies have documented the timing and pattern of Laurentide Ice Sheet margin retreat since the Last Glacial Maximum, but few studies have provided vertical constraints necessary for accurate sea level contribution estimates. Here we present 21 ³⁶Cl ages from boulder and bedrock samples along vertical transects spanning ~1,000 m of relief from multiple peaks in the Adirondack Mountains of northeastern New York, USA. Our exposure ages span the Last Glacial Maximum through the last deglaciation, with the highest-elevation sites (~1,500 m) ranging between 25 and 19 ka, and the lower elevation sites (≤1,300 m) between 16 and 13 ka. These data suggest gradual ice sheet thinning of 200 m initiated at ~20 ka followed by more rapid surface lowering of 1,000 m approximately coincident with Bølling-Allerød warming.