The Younger Dryas (YD; 12.9 to 11.7 thousand years before present [ka]) was an abrupt cooling event in the North Atlantic region that interrupted the last deglaciation. This interval is an important analogue for ice inception and provides key insights into the impacts of millennial-scale climatic excursions on the broad Earth System. However, the effect of YD cooling on North American ice sheets – by far the largest ice masses in the Northern Hemisphere at that time – is poorly understood. Here, we document our current level of knowledge in ice margin behavior (stabilization, advance or continued retreat) that occurred to North American ice sheets during the YD interval. We assign a quality score for each segment of the YD ice margin that takes into account (i) our degree of confidence in the YD ice position (e.g. whether prominent moraines were formed) and (ii) the quality of chronological control on the ice position (e.g. assumed vs. directly dated). We divide the North American ice sheets into 11 regions and discuss changes in behavior during the YD interval. In some cases, our level of knowledge on the local YD ice margin behavior and chronological control is good (e.g. Ten Mile Lake moraine [Newfoundland], Collins Pond Phase [Atlantic Canada], Grand Marais I moraine, Dog Lake moraine, Hartman-Lac Seul moraine [all in the region of Lake Superior], and Cree Lake moraine [northern Saskatchewan]). In other cases, our knowledge is poor, and the ice margin behavior and age assignment are inferred or interpolated across the broad region. We also bring together paleoclimate data from 155 sites (largely lakes, ponds and peatlands) situated near the YD ice margin to provide additional context for any local or regional climate variations during that interval and to explore potential linkages between cooling and nearby ice margin behavior. We finish by discussing YD ice sheet response in other areas (ie. Svalbard and Fennoscandia); outlining the possible mechanisms for YD cooling; delving into numerical modelling through the YD interval and suggesting future improvements in empirical and numerical approaches.

中文翻译：

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北美冰盖对新仙女木期冷逆转（12.9至11.7ka）的响应


新仙女木期（YD；距今 12.9 至 11700 年[ka]）是北大西洋地区的一次突然变冷事件，中断了最后一次冰消期。这个间隔是冰形成的一个重要类比，并为了解千禧年规模的气候偏移对广泛地球系统的影响提供了重要见解。然而，YD 降温对北美冰盖（当时北半球迄今为止最大的冰块）的影响却知之甚少。在这里，我们记录了我们目前对 YD 期间北美冰盖发生的冰缘行为（稳定、前进或持续后退）的了解水平。我们为 YD 冰缘的每个部分分配质量分数，考虑到 (i) 我们对 YD 冰位置的置信度（例如是否形成明显的冰碛）和 (ii) 对冰位置的时间控制质量（例如假设与直接日期）。我们将北美冰盖分为 11 个区域，并讨论 YD 期间的行为变化。在某些情况下，我们对当地 YD 冰缘行为和年代控制的了解程度很高（例如十英里湖冰碛[纽芬兰]、柯林斯池塘阶段[加拿大大西洋]、Grand Marais I 冰碛、Dog Lake 冰碛、Hartman-Lac Seul 冰碛[全部位于苏必利尔湖地区]和Cree 湖冰碛[萨斯喀彻温省北部]）。在其他情况下，我们的知识匮乏，并且冰缘行为和年龄分配是在广阔的区域中推断或插值的。 我们还汇集了来自 YD 冰缘附近 155 个地点（主要是湖泊、池塘和泥炭地）的古气候数据，为该区间内任何当地或区域气候变化提供额外的背景信息，并探索降温与附近冰缘行为之间的潜在联系。我们最后讨论了其他地区（即斯瓦尔巴群岛和芬诺斯坎迪亚群岛）的 YD 冰盖响应；概述 YD 冷却的可能机制；通过 YD 区间深入研究数值模型，并提出经验和数值方法的未来改进建议。