FILLING IN THE GAPS FOR LAURENTIDE DEGLACIAL THINNING IN THE ADIRONDACK MOUNTAINS, NEW YORK, USA

The timing of Laurentide Ice Sheet (LIS) retreat during the last deglaciation is well-constrained through various geochronometers including basal radiocarbon ages, varves, and cosmogenic nuclide surface exposure dating. Less constrained, however, is how the surface of this ice sheet thinned at the same time. Such information is vital when considering ice-volume estimates and contribution of ice sheets to sea-level rise. Using ³⁶Cl surface exposure dating methodologies, we aim to vertically constrain the surface of the ice as it thinned through the Adirondack Mountains of New York. These data provide a geologic constraint for the ice surface thus providing insight for ice volume and sea level rise estimations. Additionally, we pair these exposure ages with a high-resolution ice sheet model (ISSM) to address the characteristics of ice sheet thinning for the southeastern portion of the LIS. Here we present 21 ³⁶Cl exposure ages from boulders and bedrock collected over a vertical transect of multiple peaks in the Adirondacks along with preliminary modeling results and future plans. These initial ages demonstrate gradual, early thinning of the ice surface ~20 ka followed by rapid thinning of ~1000 m broadly synchronous with Bølling-Allerød warming (~14.5 ka). This later-phase thinning correlates with similar studies from the region and suggests some contribution of the LIS to rapid sea-level rise during Meltwater Pulse 1a. Additional samples collected over the summer of 2022 will provide a significantly more precise age relationship by filling in elevational gaps and targeting high peaks (>1400 m) to address scatter in existing ages.