Collaborative Research: Climatic instability in interior Alaska from the isotopic record of Late Quaternary ground ice.

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Intellectual Merit : Preliminary results of 14C-dated periglacial ice wedge growth intervals and d18O profiles suggest that the last glacial climate in Arctic Alaska was characterized by millennial-scale variability. These abrupt events are characterized by alternating ice wedge growth and at least seven thaw periods over the interval of 45,000 to 20,000 yrs BP. A decrease in ice wedge d18O values with decreasing ice age indicates gradual cooling during cold stadial climates. The hypothesis that these millennial-scale ice-wedge growth/thaw events are arctic manifestations of northern hemisphere stadials and the nine warm Dansgaard/Oeschger events (stadials 3-11) evident in Greenland Ice is evaluated. To test the hypothesis, ice wedges will be dated by 14C of entrapped organic material, and paleoclimate conditions estimated via the generation of d18O and dD time series, a proxy for winter air temperature. If the hypothesis is correct, it will indicate that the abrupt and severe millennial-scale climate changes strongly manifested in Greenland and the circum-North Atlantic have a hemispheric spatial fingerprint, and highlight the sensitivity of permafrost areas to global climate change on millennial time scales. This research will utilize the unique ground ice record in the Quaternary age permafrost in the Cold Regions Research CRREL Permafrost Tunnel near Fairbanks, Alaska, under controlled and Engineering Lab (CRREL) environmental conditions that allow precise sampling in subfreezing temperatures linked to a detailed and rigorous analysis of the sediments and ice and their sedimentary and thermal history.Broader Impacts: Due to a paucity of paleoclimatic data from Arctic and permafrost regions, this work will document the sensitivity of Arctic climate to global climate changes. Few data from the last glacial period are available from Arctic environments to calibrate global climate models, thus limiting scientists' ability to predict future climate change associated with anthropogenic global warming. Yet the effects of global warming are already documented in Arctic regions where native cultures, villages and ways of life will be severely affected by large or rapid changes in climate. The detailed stable isotopic analyses of ice wedges and ground ice will provide a high resolution proxy data source for unglaciated regions of the Arctic, filling an important data gap in our understanding of ice-ocean-atmosphere interactions in global climate. Research will be a collaborative effort, supporting undergraduate and graduate students at Dartmouth College and University of Nevada-Las Vegas.