Seasonality of Abrupt Climate Change over Greenland: Direct Tests for the Younger Dryas and 8.2 ka event using Paleolimnology

格陵兰岛气候突变的季节性：利用古湖沼学对新仙女木期和 8.2ka 事件进行直接测试

• 批准号: 2002515
• 负责人: Yarrow Axford
• 金额: $ 64.06万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2002515&HistoricalAwards=false
• 关键词: Seasonality; Abrupt; Climate; Change; over

The Younger Dryas (YD) is the best documented example of abrupt climate change in Earth’s history, yet fundamental traits of the YD remain enigmatic. Greenland sat at the epicenter of YD climate change, with intense cooling registered in ice cores, but nevertheless the Greenland Ice Sheet retreated during the YD. An influential hypothesis suggests that North Atlantic abrupt climate changes were characterized by extreme seasonality, with mild summers that explain counterintuitive YD glacier retreat. Resolving seasonality is crucial to understanding the impacts of past and future climate change on all aspects of the Arctic system – including the ice sheet, because summer temperatures drive surface melt. This study will directly assess seasonality of the YD on Greenland for the first time by developing quantitative summer and winter temperature reconstructions. This study will also assess seasonality of the major cold snap over Greenland 8,200 years ago. Intriguingly, despite being shorter and smaller in annual magnitude than the YD, that event drove glacier advances around Greenland.This research will clarify how abrupt climate change affects the Arctic/subarctic North Atlantic region, especially Greenland and its ice sheet. By resolving seasonality of air temperatures during the YD, when the ice sheet retreated despite evidence for extremely cold (annual) air temperatures, this study will also clarify the competing roles of precipitation and ocean temperatures in driving past ice sheet behavior – with implications for projections of future ice sheet mass loss. This study will test whether the Holocene 8.2 ka event was essentially a mini YD, or fundamentally different. The latter could make the YD a poor analog for future abrupt climate change, which would unfold in an interglacial world. The 8.2 ka event has been described as an ideal target for testing climate models, but the quantitative reconstructions of associated terrestrial climate changes needed to optimize such tests are rare.Another major contribution of this work is calibration and advancement of season-specific methods for reconstructing arctic climate. Such methods are needed to address questions about seasonality on diverse Quaternary timescales, providing essential tests for climate models. The proposed work will also enable more sophisticated interpretations of stable isotope records and paleotemperature reconstructions from the Greenland ice cores by providing direct comparisons. This may yield new insights from those iconic records, once seasonality of the climate changes they capture is clarified.This project will utilize classic sites that preserve rare, readily dateable YD lake sediment records. Multiple calibrated, season-specific proxies in sediment cores – including insect and pollen assemblages, terrestrial leaf wax δ2H, and aquatic insect δ18O – will test and complement one another and provide new comparisons to annually integrated records from ice cores. This work will build upon the research team’s experience calibrating and applying these proxies in Greenland. A new calibration study will verify the seasonality of leaf wax δ2H in a range of Greenland climates.The possibility of future abrupt climate change is a major societal concern. As evidence accumulates for recent and ongoing changes in North Atlantic Ocean circulation, past abrupt changes in the subpolar North Atlantic are increasingly relevant to the future. This project will train two Ph.D. students and at least six undergraduates. In addition to conducting research during the academic year, students will participate in mentored summer research institutes to build research and communication skills. To share science beyond academia and hone outreach skills, students will conduct outreach (a) in Greenland near the study site, and (b) in a Chicago area high school serving a diverse population of 3200 students, in partnership with teachers who participated in the PI’s 2018 climate science workshop for high school teachers.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.

年轻的德莱斯（YD）是地球历史上突然发生气候变化的最佳示例，但YD的基本特征仍然神秘。格陵兰岛坐在YD气候变化的震中，在冰芯中注册了强烈的冷却，但格陵兰冰盖在YD期间撤退了。一个有影响力的假设表明，北大西洋突然的气候变化的特征是极端季节性，温和的夏季解释了违反直觉的YD冰川静修。解决季节性对于理解过去和未来气候变化对北极系统各个方面的影响至关重要 - 包括冰盖，因为夏季温度驱动了表面融化。这项研究将通过开发定量的夏季和冬季温度重建，首次直接评估格陵兰岛的YD季节性。这项研究还将评估8,200年前格陵兰岛主要冷的季节性。有趣的是，dospite的年度比YD较短，更小，该事件驱动了冰川周围的冰川前进。这项研究将阐明突然的气候变化如何影响北极/亚北方大西洋亚大西洋地区，尤其是格陵兰岛及其冰盖。通过解决YD期间空气温度的季节性，当冰盖撤退的任务证据证明极度寒冷（年度）空气温度时，这项研究还将阐明降水和海洋温度在推动过去的冰盖行为中的竞争作用 - 对未来冰盖质量损失的项目产生影响。这项研究将测试全新世8.2 ka事件本质上是微型YD，还是从根本上不同。后者可以使YD成为未来突然的气候变化的糟糕类似物，这将在冰川间世界中展现。 8.2 KA事件被描述为测试气候模型的理想目标，但是相关的优化此类测试所需的相关陆地气候变化的定量重建是罕见的。这项工作的另一个主要贡献是校准和改进季节特定方法以重建北极气候。需要这样的方法来解决有关潜水员第四纪时间尺度上季节性的问题，从而为攀岩模型提供了必不可少的测试。拟议的工作还将通过提供直接比较来对稳定的同位素记录和古植物的重建进行更复杂的解释。这可能会从这些标志性记录中产生新的见解，一旦阐明了气候变化的季节性，就可以阐明。该项目将利用经典的网站，这些网站可保留罕见的，容易数据的YD湖沉积物记录。沉积物核中多个经过校准的季节特异性代理，包括绝缘和花粉组合，地面叶蜡Δ2H和水生隔热Δ18O-将互相测试和补充，并提供与冰芯中每年集成记录的新比较。这项工作将基于研究团队在格陵兰岛进行校准和应用这些代理的经验。一项新的校准研究将在一系列格陵兰气候中验证叶蜡Δ2H的季节性。未来突然气候变化的可能性是一个主要的社会关注点。随着证据积累了北大西洋循环的最新变化和正在进行的变化，北大西洋亚北大西洋的过去的突然变化与未来越来越相关。该项目将培训两位博士学位。学生和至少六名本科生。除了在学年进行研究外，学生还将参加修订的夏季研究机构，以建立研究和沟通技巧。要分享科学以外的科学和磨练的宣传技巧，学生将在研究站点附近的格陵兰进行外展（a），以及（b）在芝加哥地区的高中，为3200名学生提供服务，与PI的教师合作，他们与PI参加2018年2018年气候科学工厂的教师合作。影响审查标准。

项目成果

Arctic chironomid training set from Canada, Greenland, Iceland and Svalbard for estimating paleotemperatures (2022)

来自加拿大、格陵兰岛、冰岛和斯瓦尔巴群岛的北极摇蚊训练集，用于估算古气温（2022 年）

• DOI: 10.18739/a27h1dn9q
• 发表时间: 2022
• 期刊: NSF Arctic Data Center
• 作者: Medeiros, Andrew;Axford, Yarrow;Chipman, Melissa;Francis, Donna;Hamerlik, Ladislav;Langdon, Peter;Schellinger, Grace;Puleo, Peter;Steigleder, Regan;Walker, Ian
• 通讯作者: Walker, Ian

Chironomid species counts and chironomid-inferred summer temperatures, Lake N14, Greenland (early Holocene and late glacial) (2022)

摇蚊物种计数和摇蚊推断的夏季温度，格陵兰岛 N14 湖（全新世早期和冰川晚期）（2022 年）

• DOI: 10.18739/a2qb9v69x
• 发表时间: 2022
• 期刊: NSF Arctic Data Center
• 作者: Axford, Yarrow;Medeiros, Andrew;Puleo, Peter;Schellinger, Grace;Steigleder, Regan;Woodroffe, Sarah
• 通讯作者: Woodroffe, Sarah

Direct evidence for thinning and retreat of the southernmost Greenland ice sheet during the Younger Dryas

• DOI: 10.1016/j.quascirev.2021.107105
• 发表时间: 2021-09
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: A. Carlson;A. Reyes;Emily Gusterson;Y. Axford;K. Wilcken;D. Rood

Younger Dryas and early Holocene climate in south Greenland inferred from oxygen isotopes of chironomids, aquatic Moss, and Moss cellulose

• DOI: 10.1016/j.quascirev.2022.107810
• 发表时间: 2022-11
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: P. Puleo;A. Masterson;A. Medeiros;G. Schellinger;Regan Steigleder;S. Woodroffe;M. Osburn;Y. Axford

NOAA/WDS Paleoclimatology - South Greenland Chironomid, Moss, and Cellulose Oxygen Isotope Data during the Younger Dryas and Early Holocene

NOAA/WDS 古气候学 - 新仙女木期和全新世早期的南格陵兰摇蚊、苔藓和纤维素氧同位素数据

• DOI: 10.25921/bdkp-mv47
• 发表时间: 2022
• 期刊: NOAA National Centers for Environmental Information
• 作者: Puleo, P.;Masterson, A.L.;Medeiros, A.;Schellinger, G.C.;Steigleder, R.;Woodroffe, S.;Osburn, M.R.;Axford, Y.
• 通讯作者: Axford, Y.