Deglaciation of Anticosti Island (eastern Canada) and its implications on climate-driven dynamics of the Laurentide Ice Sheet margin

Reconstructing the dynamical retreat pattern of former ice margins is essential to better understand the long-term evolution of ice-sheets and their sensitivity to climate change. Here we present a geomorphological map of ice-marginal landforms from Anticosti Island together with 31 cosmogenic nuclide surface exposure and 24 radiocarbon ages, that suggest close ties between regional deglaciation patterns and climate. These results reveal that the Laurentide Ice Sheet stabilized on Anticosti Island between ∼15.5 and ∼14.4 ka, before subsequently resuming its retreat toward the Québec North Shore and into the Gulf of St. Lawrence. Moraine ages highlight a strong sensitivity of the LIS to temperature changes in the Northern Hemisphere, as the documented ice-margin stabilizations coincide with the end of Heinrich Stadial 1, a period after the Last Glacial Maximum characterized by cold winters but warming summers. In turn, ice sheet recession in the area coincided with the onset of the Bølling-Allerød (∼14.6 ka), marked by relatively warmer atmosphere temperature year-round across the Northern Hemisphere. These results provide evidence for the synchronicity of the ice margin along the southeastern Laurentide Ice Sheet in response to abrupt cold periods and allow further discussion of the regional implications for deglaciation of the Laurentian Channel in the context of a large calving bay formation in the former Gulf of St. Lawrence.