Collaborative Research: Temperature and atmospheric circulation history of high-latitude Canada across interglacials of the past 1.5 Myr from cave deposits

北极地区的变暖速度是全球平均水平的两倍多，导致永久冻土、海冰和格陵兰冰盖迅速融化。这些高纬度的变化对全球产生了显著的影响：永久冻土融化释放温室气体，海冰减少改变了北半球的风型，格陵兰岛冰的减少导致海平面上升。随着人为变暖的持续，测试我们对北极气候可能如何变化的理解是很重要的，这样我们才能做好准备。该项目将利用加拿大西北部的洞穴沉积物，重建北极气候在过去150万年的温暖时期是如何反应的，这些洞穴沉积物记录了温度和降水模式的信息。我们将特别关注记录过去永久冻土、海冰和格陵兰冰盖都不如今天广泛的时期的北极气候，这有助于测试在一个冰减少的世界中发生意外变化的可能性。该项目将通过以下方式促进教育和推广：制作视频，在幼儿园至12年级的课堂访问中分享；召开教师研讨会，设计与气候变化教育相关的教师培训计划；与研究地区的原住民部落分享项目设计和成果。该项目还将涉及本科生和培养一名研究生。该项目将使用来自加拿大西北部洞穴的独特洞穴沉积物收集，以建立400 ka至1.5 Ma间冰期降水的洞穴温度和氧同位素组成的准确年代记录。通过将所含流体的氧同位素测量值与周围碳酸钙的氧同位素测量值进行比较，可以重建洞穴温度，从而估计洞穴外的平均年温度变化以及降水的同位素组成。这些数据将提供北半球高纬度大陆在更新世中期间冰期条件的一些唯一约束条件，从而能够检验关于北半球冰冻圈在400 ka之前的间冰期为什么弹性要小得多的假设。这里开发的降水同位素重建将为格陵兰冰盖在最后一次冰期旋回的基础记录提供重要的更深时间补充。该研究还代表了当代流体包裹体测量在高纬度洞穴中的首次应用，有可能在其他高纬度洞穴中开辟类似的应用。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。

Arctic regions are warming at more than twice the global average, causing rapid melting of permafrost, sea ice and the Greenland ice sheet. These high-latitude changes have pronounced impacts around the globe: permafrost melting releases greenhouse gases, declining sea ice changes wind patterns around the Northern Hemisphere, and loss of ice in Greenland causes sea level rise. As anthropogenic warming continues, it is important to test our understanding of how Arctic climate is likely to change so that we can prepare. This project will reconstruct how Arctic climate has responded during warm periods of last 1.5 million years, using cave deposits from northwestern Canada that archive information about both temperature and precipitation patterns. We will focus particular attention on documenting Arctic climate during periods in the past when permafrost, sea ice and the Greenland ice sheet were all less extensive than today, helping test the potential for unexpected shifts in a world with less ice. The project will contribute to education and outreach by creating videos that will be shared in K-12 classroom visits, convening a teacher workshop to design a teacher training program related to climate change education, and sharing project design and outcomes with First Nations bands in the study area. The project will also involve undergraduate students and train a graduate student.This project will use a unique collection of cave deposits from caves in northwestern Canada to build well-dated records of cave temperature and the oxygen isotope composition of precipitation across interglacials between 400 ka and 1.5 Ma. Cave temperatures will be reconstructed by comparing the oxygen isotope measurements of included fluids to that of the surrounding calcium carbonate, allowing estimates of mean annual temperature changes outside the caves and of the isotopic composition of precipitation. These data will provide some of the only constraints on conditions during mid-Pleistocene interglacials from high-latitude Northern Hemisphere landmasses, enabling testing of hypotheses as to why the Northern Hemisphere cryosphere was much less resilient during interglacials prior to 400 ka. The precipitation isotope reconstructions developed here will offer an essential deeper-time complement to foundational records from the Greenland ice sheet over the last glacial cycle. The study also represents the first application of current-generation fluid inclusion measurements to high-latitude speleothems, potentially opening up similar applications in other high-latitude caves.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.