Harvard University, Department of Earth and Planetary Sciences, Cambridge, Massachusetts 02138, USA.
Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, Oregon 97331, USA.
Nat Commun. 2017 May 30;8:15612. doi: 10.1038/ncomms15612.
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.
美国大西洋中部的海平面记录对 Laurentide 冰盖的历史非常敏感，因为海岸线位于冰盖的外围隆起处。然而，弗吉尼亚州和北卡罗来纳州现代海岸线的古海平面标记，其年代可追溯到海洋同位素阶段 3（MIS 3），即 50 至 35 千年前，对于这个冰川时期来说非常高，这是以前的冰河时代调整模型或其他局部（例如构造）效应无法解释的。在这里，我们使用一个经过修正的冰川均衡调整模型来协调这个海平面记录，该模型的特点是在 MIS 3 期间全球平均海平面峰值约为-40m，并且 Laurentide 冰盖东部地区的冰量远远小于这一时期的传统重建。我们的结论是，Laurentide 冰盖在进入末次冰盛期的 15 千年中经历了一个非常快速的增长阶段，这凸显了中场海平面记录在冰川时期对限制冰盖面积的潜力，因为这个时期的地质观测结果很少。
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