P2C2: Collaborative Research: The Role of Seasonality in Abrupt Climate Change - a Test by Reconstructing Fluctuations of a Late-Glacial Ice Mass in Eastern North America

P2C2：合作研究：季节性在气候突变中的作用——通过重建北美东部晚冰期冰块波动进行的测试

• 批准号: 2202791
• 负责人: Thomas Lowell
• 金额: $ 31.3万
• 依托单位: University of Cincinnati Main Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2202791&HistoricalAwards=false
• 关键词: P2C2; Collaborative; Research; Role; Seasonality

This research aims to determine the signature of summer-warming-driven ice retreat and meltwater production by reconstructing the behavior of an ice cap that persisted in northwestern Maine during the end of the last ice age. By mapping and dating glacial landforms documenting the pattern and timing of Maine ice-cap recession, as well as by reconstructing meltwater fluxes from the decaying ice cap in the Gulf of Maine on the basis of marine sediment geochemistry, the researchers will evaluate whether this ice cap system fluctuated in concert with the abrupt climate changes as registered in Greenlandic ice cores, or whether it retreated during the North Atlantic stadial episodes, reflecting summertime warming and hence intense seasonality. Informed by these geological reconstructions of glacier and meltwater change, the researchers will employ an Earth System Model to evaluate the effects of warming-induced meltwater fluxes on seasonality in the North Atlantic region. Clarifying the role of seasonality in abrupt climate change will have important implications for deciphering the origins of abrupt climate change and will help to hone understanding of the global climate dynamics that brought the ice age to an end. The overall research effort will provide field-based training and education for the next generation of scientists at the undergraduate and graduate level, as well as in-depth enhanced public engagement in cooperation with Maine’s Baxter State Park, home of Katahdin, the highest mountain in the region and the northern end of the Appalachian Trail. The researchers will work closely with the Baxter Park Authority on innovative ways to educate the public about the intertwined glacial and climatic history of the region and its greater global context. Specific objectives include developing 3D-printed landscape models, which will be displayed along with educational placards at park venues. The researchers will also collaborate with a New Media team to develop an informative smartphone app that can be used throughout the park.The termination of the last ice age featured a spectacular series of abrupt climate oscillations. In the North Atlantic region, ice cores recorded abrupt switches between ‘stadial’ intervals, such as ‘Heinrich Stadial 1’ (HS1; ~18,000 – 14,700 kyr ago) and the ‘Younger Dryas’ (YD; ~12,800 – 11,600 kyr ago), which were characterized by cold mean-annual temperatures, and the intervening Bølling-Allerød ‘interstade’ (B-A; 14,700 – 12,800 kyr ago) that was characterized by warmer mean-annual temperatures. However, emerging evidence in the North Atlantic region indicates that, because of surface-ocean freshening and sea-ice formation, the signature of mean-annual temperatures in Greenlandic ice cores may reflect episodes of extreme seasonality during stadials, with severe sea-ice-induced winter cooling masking a divergent trend of summertime warming. Because glaciers are highly sensitive to summer temperatures, records of glacier change during the termination of the last ice age can therefore be used to evaluate the role of seasonality in abrupt climate change. To test the seasonality hypothesis, the researchers will use a combination of geomorphic mapping, terrestrial glacial geochronology, and marine sediment geochemistry to reconstruct both the vertical thinning and lateral retreat of the Maine ice cap and the relative pattern of meltwater release into the Gulf of Maine. Mapping will be aided by recently acquired high-resolution LiDAR elevation data, and the terrestrial chronology will be underpinned by 10Be surface-exposure dating of glacial landforms and 14C dating lacustrine sediments. Foraminiferal trace-metal measurements will be paired with δ18O to reconstruct meltwater fluxes into the Gulf of Maine. The results of this work will be used to determine whether or not glacial ice receded during HS1 and then stabilized during B-A time, as predicted by the seasonality hypothesis and consistent with the pattern of surface-freshening registered in North Atlantic sediments. Glacier and meltwater reconstructions will serve as metrics for a GFDL suite of Earth system models employed to test the response of the North Atlantic seasonal cycle to imposed summer atmospheric warming and freshwater fluxes, affording a data-model test of the seasonality hypothesis for abrupt climate change.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

这项研究旨在通过重建上一个冰期结束时缅因州西北部持续存在的冰盖的行为，来确定夏季变暖驱动的冰川消退和融水产生的特征。通过绘制记录缅因州冰盖退缩模式和时间的冰川地貌，以及根据海洋沉积物地球化学重建缅因湾腐烂冰盖的融水通量，研究人员将评估这一冰盖系统是与格陵兰冰芯记录的气候突变同步波动，还是在北大西洋盛行时期退缩，反映夏季变暖并因此具有强烈的季节性。根据这些冰川和融水变化的地质重建，研究人员将使用地球系统模型来评估变暖导致的融水通量对北大西洋地区季节性的影响。弄清季节性在气候突变中的作用将对破译气候突变的起源具有重要意义，并将有助于磨练对导致冰河时代结束的全球气候动态的理解。总体研究工作将为下一代本科生和研究生科学家提供实地培训和教育，并与缅因州巴克斯特州立公园合作，深入加强公众参与，该公园是该地区最高的山脉卡塔赫丁的所在地，也是阿巴拉契亚小径的北端。研究人员将与巴克斯特公园管理局密切合作，以创新的方式教育公众了解该地区交织在一起的冰川和气候历史及其更广泛的全球背景。具体目标包括开发3D打印的景观模型，这些模型将与公园场馆的教育标语牌一起展示。研究人员还将与新媒体团队合作开发一款信息丰富的智能手机应用程序，可以在整个公园使用。上一次冰河时代的结束以一系列壮观的突然气候振荡为特征。在北大西洋地区，冰芯记录到了“稳定”间隔之间的突变，如‘Heinrich Staial 1’(HS1；约18,000-14,700 Kyr前)和‘Young Dryas’(YD；约12,800-11,600 Kyr前)，它们的特点是年平均温度较低，而介于两者之间的Bölling-allerødód‘(B-A；14,700-12,800 Kyr前)的特点是年平均温度较高。然而，北大西洋区域的新证据表明，由于表层-海洋淡水和海冰的形成，格陵兰冰芯年平均温度的特征可能反映了主场期间的极端季节性事件，严重的海冰引起的冬季降温掩盖了夏季变暖的不同趋势。由于冰川对夏季温度高度敏感，因此可以利用上一次冰期结束时冰川变化的记录来评估季节性在气候突变中的作用。为了验证季节性假设，研究人员将结合地貌测绘、陆地冰川年代学和海洋沉积物地球化学来重建缅因州冰盖的垂直变薄和横向后退，以及融水释放到缅因湾的相对模式。测绘将得到最近获得的高分辨率激光雷达高程数据的帮助，陆地年代学将通过冰川地貌的10Be地表暴露测年和湖泊沉积物的14C测年来支持。有孔虫痕量金属测量将与δ18O配对，以重建进入缅因湾的融水流量。这项工作的结果将被用来确定冰川冰是否如季节性假说所预测的那样在HS1期间消退，然后在B-A时间稳定下来，并与北大西洋沉积物中记录的表面清新模式一致。冰川和融水重建将作为GFDL地球系统模型套件的衡量标准，用于测试北大西洋季节循环对夏季大气变暖和淡水通量的响应，为气候突变的季节性假设提供数据模型测试。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。