Abstract
The U.S. mid-Atlantic sea-level record is sensitive to the history of the Laurentide Ice Sheet as the coastline lies along the ice sheet’s peripheral bulge. However, paleo sea-level markers on the present-day shoreline of Virginia and North Carolina dated to Marine Isotope Stage (MIS) 3, from 50 to 35 ka, are surprisingly high for this glacial interval, and remain unexplained by previous models of ice age adjustment or other local (for example, tectonic) effects. Here, we reconcile this sea-level record using a revised model of glacial isostatic adjustment characterized by a peak global mean sea level during MIS 3 of approximately −40 m, and far less ice volume within the eastern sector of the Laurentide Ice Sheet than traditional reconstructions for this interval. We conclude that the Laurentide Ice Sheet experienced a phase of very rapid growth in the 15 kyr leading into the Last Glacial Maximum, thus highlighting the potential of mid-field sea-level records to constrain areal extent of ice cover during glacial intervals with sparse geological observables.
Highlights
The U.S mid-Atlantic sea-level record is sensitive to the history of the Laurentide Ice Sheet as the coastline lies along the ice sheet’s peripheral bulge
Oxygen isotope records from marine sediment cores provide a proxy for global ice volume after correcting for temperature-dependent fractionation[3], uncertainties in this correction and other complications in mapping isotope values to ice volumes have yielded estimates of peak Marine Isotope Stage (MIS) 3 global mean sea level (GMSL) that range from À 30 to À 60 m relative to present day[1]
This record indicates that Marine Isotope Stage 3 (MIS 3) relative sea level (RSL) reached present-day levels from B50 to 35 ka in this region[11,12,13,14,15,16] (Fig. 1; Supplementary Table 1), but glacial isostatic adjustment (GIA) calculations predict that these markers should presently be found as much as B70 m below sea level[8]
Summary
The U.S mid-Atlantic sea-level record is sensitive to the history of the Laurentide Ice Sheet as the coastline lies along the ice sheet’s peripheral bulge. Paleo sea-level markers on the present-day shoreline of Virginia and North Carolina dated to Marine Isotope Stage (MIS) 3, from 50 to 35 ka, are surprisingly high for this glacial interval, and remain unexplained by previous models of ice age adjustment or other local (for example, tectonic) effects We reconcile this sea-level record using a revised model of glacial isostatic adjustment characterized by a peak global mean sea level during MIS 3 of approximately À 40 m, and far less ice volume within the eastern sector of the Laurentide Ice Sheet than traditional reconstructions for this interval. We conclude that a revised GIA model can reconcile the MIS 3 sea-level record at the Albemarle Embayment under two conditions: (1) peak GMSL reached near À 40 m and (2) the eastern sector of LIS was significantly reduced during MIS 3 compared with previous reconstructions of ice extent
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