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: 2202762
• 负责人: Aaron Putnam
• 金额: $ 60.17万
• 依托单位: University of Maine
• 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=2202762&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在上一个冰河时代结束时在缅因州西北部持续存在的冰盖的行为来确定夏季温暖驱动的冰撤退和融化生产的签名。通过绘制和约会冰川地面记录缅因州冰盖经济衰退的模式和时机，以及通过对缅因州海湾腐烂的冰盖中的融化液化的融合来构建融化冰盖的融化，研究人员是否会在北部冰盖的冰盖冰盖在冰上恢复的过程中是否浮出水面，是否会恢复冰盖的冰盖，是否会恢复到冰上的冰盖，这是否会逐渐变化。体育发作，反映了夏季变暖，因此季节性强烈。在这些地质重建的冰川和融合水变化的情况下，研究人员将采用地球系统模型来评估变暖诱导的融合水通量对北大西洋地区季节性的影响。澄清季节性在突然的气候变化中的作用将对破译突然的气候变化的起源具有重要意义，并将有助于对使冰河时代结束的全球气候动态的理解理解。总体研究工作将为本科和研究生层面的下一代科学家提供基于现场的培训和教育，并与缅因州的巴克斯特州立公园（Katahdin of Katahdin的所在地）合作，加强了公众的参与，研究人员将与百特公园管理局紧密合作，以对公众进行创新的方式，以教育该领域的整体和环境范围，并构成了整体的环境，并有所了解。特定的物体包括开发3D打印的景观模型，该模型将与公园场所一起展示。研究人员还将与一个新媒体团队合作开发一个可用的智能手机应用程序，该应用程序可以在整个公园内使用。最后一个冰河时代的终止效果着一系列突然的气候振荡。在北大西洋地区，冰芯在“体型”间隔之间记录了突然的切换，例如“ Heinrich Stadial 1”（HS1； 〜18,000 - 14,700 Kyr）和“年轻的Dryas”（YD; 〜12,800 - 11,600 Kyr），这些吉尔（yd; 〜12,800; （B-A; 14,700 - 12,800 Kyr of）的特征是均值较高的温度。然而，北大西洋地区的新兴证据表明，由于表面海洋的鲜明和海冰形成，绿色冰岩心中平均温度的标志可能反映了体型期间极端季节性的发作，严重的Sea-Ice引起的冬季冬季冷却掩盖了夏季时间的夏季潮流趋势。由于冰川对夏季温度高度敏感，因此可以使用最后一个冰河时代终止冰川变化的记录来评估季节性在突然的气候变化中的作用。为了检验季节性假设，研究人员将使用地貌映射，地面冰川学和海洋沉积物地球化学的结合，以重建缅因州冰盖的垂直稀疏和侧向撤退以及梅尔特沃特释放的相对模式。最近获得的高分辨率激光振荡数据数据将有助于映射，陆地年表将受到冰川地面的10BE表面暴露年代和14C约会湖泊沉积物的支持。有孔虫痕量 - 金属测量将与Δ18O配对，以重建融化液通量到缅因州的海湾。如季节性假设所预测的那样，这项工作的结果将用于确定是否在HS1期间退缩，然后在B-A时间内稳定，并与北大西洋沉积物注册的表面效应模式一致。冰川和融水的重建将作为GFDL套件的地球系统模型的度量更广泛的影响审查标准。