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地球仪产生了显著的影响：永久冻土融化释放温室气体，海冰减少改变了北方半球的风模式，格陵兰岛的冰减少导致海平面上升。随着人为变暖的继续，重要的是要测试我们对北极气候可能如何变化的理解，以便我们能够做好准备。该项目将利用加拿大西北部的洞穴沉积物来重建北极气候在过去150万年温暖时期的反应，这些洞穴沉积物记录了有关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，帮助测试在冰较少的世界中发生意外变化的可能性。该项目将通过创建将在K-12课堂访问中分享的视频，召开教师研讨会以设计与气候变化教育相关的教师培训计划，并与研究领域的第一民族乐队分享项目设计和成果，为教育和推广做出贡献。该项目还将涉及本科生，并培训一名研究生，该项目将利用加拿大西北部洞穴的独特洞穴沉积物收集，建立400 ka至1.5 Ma间冰期洞穴温度和降水氧同位素组成的日期明确的记录。洞穴温度将通过比较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来重建，从而可以估计洞穴外的年平均温度变化和降水的同位素组成。这些数据将提供一些唯一的限制条件，在中更新世间冰期从高纬度北方半球的陆地，使测试的假设，为什么北方半球冰冻圈是在400万年前的间冰期弹性小得多。在这里开发的降水同位素重建将提供一个必要的更深的时间补充基础记录从格陵兰冰盖在最后一次冰期循环。这项研究也代表了当前一代流体包裹体测量的第一个应用到高纬度洞穴，可能打开类似的应用在其他高纬度caves.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

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.