Abstract
AbstractThe dynamics and paleo‐glaciology of ice sheet interiors during the last deglaciation are poorly constrained, hindering ice sheet model reconstructions. We provide direct evidence of Fennoscandian Ice Sheet (FIS) interior behavior during deglaciation through surface exposure dating. Our results demonstrate early thinning of the FIS, prior to the Younger Dryas (YD, 12.8–11.7 ka). Interior thinning in central Norway was concurrent with retreat along the coastline, exposing ice‐free mountainous tracts, potentially as early as 20–15 ka. The FIS then formed moraines in these ice‐free tracts during the YD. This is contrary to current hypotheses advocating a landscape fully covered by cold, inactive ice during this period. Present empirical and model reconstructions fail to capture rapid interior downwastage, increasing uncertainties in ice sheet volume estimates and sea level contributions.
Highlights
Reconstructions of ice sheet behavior from the last deglaciation (≤21 ka) until the onset of the Holocene at 11.7 ka provide fundamental, long‐term insights into ice sheet‐climate interactions, internal ice dynamics (Ullman et al, 2015), sea level rise contributions (Ritz et al, 2015), and mechanisms of rapid deglaciation (DeConto & Pollard, 2016)
While we do not eliminate these samples from our study, we acknowledge that they must be treated with some caution
Our study demonstrates that interior thinning of the central and southern Fennoscandian Ice Sheet (FIS) during the last deglaciation occurred earlier than previously thought, in accordance with the Sernander‐Dahl Hypothesis
Summary
Reconstructions of ice sheet behavior from the last deglaciation (≤21 ka) until the onset of the Holocene at 11.7 ka provide fundamental, long‐term insights into ice sheet‐climate interactions, internal ice dynamics (Ullman et al, 2015), sea level rise contributions (Ritz et al, 2015), and mechanisms of rapid deglaciation (DeConto & Pollard, 2016). These are vital to constrain and calibrate ice sheet (Lecavalier et al, 2014), glacial isostatic adjustment (Whitehouse, 2018), and earth system models (Vizcaino et al, 2015). Ice thickness and interior dynamics during deglaciation are poorly constrained, limiting estimates of glacial isostatic adjustment and ice sheet sea level contributions in the paleo record and for future projections of sea level contributions
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