Reconstructing North American rivers and lakes during the last deglaciation

Starting ~20,000 years ago, the North American Ice-sheet Complex receded. As it did, its meltwater formed proglacial lakes, altered water tables, and flowed through rivers to the sea. These waters in turn shaped the landscape and altered ocean circulation. Here we reconstruct the spatially resolved pattern of lakes, wetlands, and river discharge using an updated modeling approach. We reconstruct the Laurentide Ice Sheet using ICESHEET v2.0, which prescribes a basal stress field and mapped ice margins to produce maps of steady-state ice thickness. After accounting for glacial isostatic adjustment and past climate, we simulate groundwater and surface-water distributions using the Water Table Model (WTM) v2.0.1. Following this reconstruction, we map water routing to the ocean, including river discharge and passage through proglacial lakes. We compare these findings against the dated timing of fluvial aggradation, often driven by ice-sheet-derived sediment supply, and incision, which occurs when river discharges remain high but lakes trap incoming sediment.