Rapid Deglacial Response of the Laurentide Ice Sheet during the Allerød Warm Interval Through the High Peak Wilderness of the Adirondack Mountains, New York, USA

Abstract. The Laurentide Ice Sheet (LIS) was the largest ice mass by volume during the last glacial cycle, containing approximately 75–85 m of global sea-level equivalent, and representing a major component of the climate system. Constraining the timing of LIS deglaciation is critical for evaluating its contributions to sea-level rise, climate variability, and ice-climate feedback. The Adirondack Mountains of New York (ADK) represent a topographically complex and previously under sampled region of the northeastern United States. Because this ~24,000 km² region represents a more interior component of the entire LIS, it provides an opportunity to investigate both the timing and mechanisms of interior ice-retreat following the Last Glacial Maximum. Here we present ³⁶Cl surface exposure ages from the High Peaks Wilderness region of the Adirondack Mountains, integrated with high-resolution transient ice-sheet model simulations to refine the timing and pattern of ice-sheet retreat through the mountainous terrain. Results suggest complete exposure of the region by 13.5 ± 0.6 ka (2σ), with modelled deglaciation occurring over an approximately 500-year interval, consistent with minimum-limiting radiocarbon ages indicating biotic reoccupation by ~13 cal ka. This updated chronology is younger than previous estimates for deglaciation across the northeastern United States, indicating later exposure during the Allerød warm interval (~14.2 to 13.0 ka). Our reconstructed ice-retreat chronology agrees with the ice-sheet modelling, which shows rapid thinning beginning at ~13.5–13.0 ka but delayed exposure of the High Peaks until the later Allerød. Together, these results suggest that Laurentide retreat through the Adirondacks lagged the onset of Bølling–Allerød warming before proceeding rapidly across the region.