Rapid retreat of the southwestern Laurentide Ice Sheet during the Bølling-Allerød interval

Abstract The timing of Laurentide Ice Sheet deglaciation along its southwestern margin controlled the evolution large glacial lakes and has implications for human migration into Americas. Accurate reconstruction ice sheet's retreat also constrains isostatic adjustment models is important understanding ice-sheet sensitivity to climate forcing. Despite significance, (SWLIS) poorly constrained by minimum-limiting 14C data. We present 26 new cosmogenic 10Be exposure ages spanning western Interior Plains, Canada. Using a Bayesian framework, we combine these data with geomorphic mapping, 10Be, high-quality provide an updated chronology. This dataset presents internally consistent record indicates that initial detachment SWLIS from convergence Cordilleran began ca. 15.0 ka, concurrent or slightly prior onset Bølling-Allerød interval (14.7–12.9 ka) retreated >1200 km Younger Dryas (YD) position in ~2500 yr. Ice-sheet stabilization at Cree Lake Moraine facilitated meltwater drainage route Arctic Agassiz within YD, but not necessarily beginning. Our YD constraints demonstrate Plains was ~60% faster than suggested minimum alone. Numerical modeling this rapid estimates loss ~3.7 m sea-level equivalent during interval.