The Last deglaciation in Greenland: demystifying the mystery interval

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The ‘last deglaciation’ is the transition from the last Ice Age to our current climate state; a transition that took from approximately 18,000 to 11,000 years ago. The last deglaciation is the most recent natural example of large-scale global warming, which can help scientists better understand scientifically and societally important problems such as the sensitivity of climate to atmospheric carbon dioxide and the sensitivity of the Greenland ice sheet to climate change. The award supports new and improved reconstructions of Greenland temperature and snowfall rates for the last 23,000 years. The work will enhance scientific understanding of Greenland climate history, can improve Greenland ice sheet model simulations of past and future ice loss, and provides a benchmark for climate model simulations. The award supports a graduate student at Oregon State University and a summer undergraduate internship at University of Washington, contributing to the STEM (Science, Technology, Engineering and Mathematics) workforce. The researchers will visit regional middle and high schools annually for a day of polar research. The award supports the further development and professional design of a Climate Feedback boardgame – an active-learning classroom activity for teaching climate feedbacks and their role in global climate change. The researchers will use a new climate reconstruction strategy that combines four independent sources of Greenland climate information from ice cores: borehole temperatures, water stable isotope ratios of ice, isotopic fractionation in atmospheric nitrogen, and methane-based empirical constraints on the ice core gas age-ice age difference; previous reconstructions have only considered two or fewer of such constraints at a time. Targeted high-precision measurements of methane and nitrogen isotopic fractionation (∂15N-N2) will be performed on the Greenland NEEM, NGRIP and GISP2 ice cores to aid these reconstructions, and to replicate recently discovered glacial ∂15N-N2 signals in the GISP2 core. The award supports new model development to incorporate these new sources of climatic information into a single reconstruction. The work further includes a series of hypothesis-driven modeling experiments using a state-of-the-art isotope-enabled climate model that seek to answer the paradoxical observation of an extremely weak near-field Heinrich Event response in Greenland, and a strong far-field response in the global monsoon and tropical hydrology.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.