Cosmogenic surface exposure dating of Arctic NW Laurentide ice-sheet deglaciation: implications for abrupt climate change

该项目的目标是确定最后一次冰消期间北极西北劳伦泰德冰盖（LIS）的Keewatin Dome的退缩日期，并测试冰退缩的时间和速度，融水向北冰洋的排放和气候突变之间的关系。该研究还将记录与北极西北LIS撤退相关的融水如何可能导致冰消期海平面上升。调查人员将测量沿沿着1 000公里东西向断面的11个地点的80块巨石中的宇宙成因核素铍-10。该项目将资助两名本科生，他们将接受冰川地质学、地质年代学、古气候学和北极实地考察方面的培训。计划在俄勒冈州的科瓦利斯举办“达芬奇日”和农贸市场，并通过一年一度的耶洛奈夫地球科学论坛向北方社区和当地地球科学家进行公众宣传。该项目将为北极冰盖退缩、大西洋纬向翻转环流和气候变化之间的关系提供新的认识。后退的北极西北Laurentide冰盖（LIS）将使用铍-10表面暴露年龄超过80巨石在11个站点沿着1000公里长的横断面垂直于LIS撤退北纬65度。采样密度为100公里，可通过冰盖模型解析。研究人员将解决两个主要问题：1）北极西北LIS冰川消退的时空模式是什么，退缩是单调的还是加速退缩的时期？北极西北LIS后退速率的变化是否与北方半球气候突变的冰消期相对应？第一个问题将使用铍年龄来回答，采样方法能够解决冰缘退缩的世纪尺度变化。第二个问题将通过比较北极西北LIS撤退的时间在11个采样点的最后一次冰消期的突然气候事件来解决。为了将冰缘退缩记录转换为冰量和融水排放的变化，研究人员将使用年表来过滤贝叶斯冰川消退LIS模型模拟，这将迫使海平面/地球模型，并与冰川消退气候模拟进行比较。该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The objective of this project is to date the retreat of the Keewatin Dome of the Arctic NW Laurentide ice sheet (LIS) during the last deglaciation and test the relationship among the timing and rate of ice retreat, discharge of meltwater to the Arctic Ocean, and abrupt climate change. The study will also document how meltwater associated with Arctic NW LIS retreat may have contributed to deglacial sea level rise. The investigator will measure the cosmogenic nuclide beryllium-10 from 80 boulders at 11 sites along a 1000 km east-west transect. The project will support two undergraduate students who will be trained in glacial geology, geochronology, paleoclimatology, and Arctic fieldwork. Public outreach is planned for Da Vinci Days and a farmers' market in Corvallis, Oregon, as well as to northern communities and local geoscientists through the annual Yellowknife Geoscience Forum. This project will provide new understanding of the relationship among Arctic ice-sheet retreat, Atlantic meridional overturning circulation, and climate change. Retreat of the Arctic NW Laurentide ice sheet (LIS) will be dated using beryllium-10 surface exposure ages for more than 80 boulders at 11 sites along a 1000 km long transect perpendicular to LIS retreat at 65 degrees North. Sampling density will be 100 km, resolvable by ice sheet models. The investigator will address two primary questions: 1) What are the spatiotemporal patterns of Arctic NW LIS deglaciation and was retreat monotonic or were their periods of accelerated retreat? And 2) Do Arctic NW LIS retreat-rate changes correspond with deglacial periods of Northern Hemisphere abrupt climate change, such as the Younger Dryas? The first question will be answered using beryllium ages, with the sampling approach able to resolve century-scale changes in ice-margin retreat. The second question will be addressed by comparing the timing of Arctic NW LIS retreat at the 11 sampling locations to abrupt climate events of the last deglaciation. To convert the ice-margin retreat record into changes in ice volume and meltwater discharge, the investigator will use the chronology to filter Bayesian deglacial LIS-model simulations, which will force sea-level/earth models and be compared to deglacial climate simulations.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.