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

该项目的目的是确定最后一次冰川消退期间北极西北劳伦斯冰盖（LIS）的Keewatin圆顶退缩的时间，并测试冰退缩的时间和速度，向北冰洋排放的融水与气候突变之间的关系。该研究还将记录与北极西北冰原消退相关的融水如何导致冰川消融的海平面上升。研究人员将沿着1000公里的东西样带从11个地点的80块巨石中测量宇宙核素铍-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、古气候学和北极野外考察方面的培训。计划在达芬奇日和俄勒冈州科瓦利斯的一个农市场进行公众宣传，并通过一年一度的耶洛奈夫地球科学论坛向北部社区和当地地球科学家进行宣传。该项目将对北极冰盖退缩、大西洋经向翻转环流和气候变化之间的关系提供新的认识。北极西北劳伦泰德冰盖（LIS）的退缩将使用铍-10表面暴露年龄对11个地点的80多块巨石进行测年，这些地点位于北纬65度垂直于LIS退缩的1000公里长的样带上。采样密度为100公里，可通过冰盖模型进行解析。研究者将解决两个主要问题：1)北极西北冰川消融的时空模式是什么？退缩是单调的还是加速退缩的时期？2)北极NW LIS后退速率的变化是否与北半球气候突变（如新仙女木期）的去冰期相对应？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11个采样点的北极西北大陆架退缩的时间与最后一次冰川消融的气候突变事件来解决。为了将冰缘退缩记录转换为冰体积和融水流量的变化，研究者将使用年代学来过滤贝叶斯冰川消融gis模型模拟，这将迫使海平面/地球模型，并与冰川消融气候模拟进行比较。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.