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

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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.