| Summary: | This award will support the development and interpretation of a new generation of records of short-lived aerosols from biomass burning, dust, sea spray, volcanism, and industrial pollution in the Arctic during the past 2000 years and for selected time periods during the past >130,000 years. These objectives will be accomplished using a unique, NSF-funded analytical system developed specifically for such measurements in ice cores and recently expanded to include detailed measurements of black carbon (BC; soot) and a range of new aerosol source tracers. Proposed measurements of aerosols during the past 2000 years - building on a series of recently published findings from similar measurements in shallower ice cores - will be made on samples from a 400 m shallow core collected by Danish collaborators in 2008 and 2009 at the NorthEem (NEEM) drilling site in northern Greenland. To place the NEEM measurements in larger Arctic and global perspective, samples from a broad array of ~1000 year archived Arctic ice cores also will be analyzed and results from the Arctic measurements compared with similar century to millennial scale aerosol measurements already underway in Antarctic ice cores. Intellectual Merit: Natural changes in the Earth's climate are well documented in paleoclimate records, but the climate history provided by deep ice cores needs to be complemented by better understanding of how recent climate changes have affected different regions and relationships among high-, mid-, and lowlatitude processes. Short-lived aerosols - including those generated by wildfires - are important environmental and global climate forcing agents and, because of the snow-albedo feedback, particularly important to Arctic forcing when deposited in snow and ice. Their sources are primarily in the low- and mid-latitudes, but their impacts on the Polar Regions - poorly quantified because of the paucity of reliable, long-term measurements - are profound. The rich glaciochemical records developed from the NEEM and archived ice cores, especially when compared to similar Antarctic ice core aerosol records and the results synthesized through collaborative modeling studies, will transform global understanding of the sources and histories of short-lived BC, dust, volcanic, sea salt, and pollution aerosols and their impacts on climate forcing, ecosystems, and human health. Moreover, because wildfire emissions are one factor directly modulating GHG concentrations, the independent history of fire emissions provided by this and related Antarctic research will contribute to a quantitative interpretation of changing GHG concentrations measured in the deep NEEM and WAIS Divide ice cores. Broader Impacts: Policy decisions are guided by global climate model (GCM) predictions of climate under different scenarios of societal behavior; climate predictions are critically dependent on well-tuned, validated models. Despite large uncertainties in aerosol forcing identified by the IPCC, ice core aerosol records seldom are used in GCM calibration, parameterization, or tuning because of the limited scope and reliability of past ice core aerosol measurements. New generation aerosol measurements from this ice core analytical system are suitable and have enabled recent collaborations with the GCM community. To ensure the broadest impact of the proposed research in climate change and policy arenas (e.g., recent testimony before the U.S. Congress on short-lived pollutants and Arctic climate change), ongoing collaborations with modelers at NCAR, NOAA/GFDL and NASA/GISS will be expanded to incorporate the proposed ice core measurements into GCM studies. This proposal also directly addresses a thrust of the NSF-sponsored International Partnerships in Ice Core Sciences (IPICS) initiative - development of an array of detailed ice core records spanning the last 2000 years aimed at better understanding long-term climate records thorough improved, quantitative investigation of recent climate change and the role of human activities in climate forcing and on the environment. The NEEM project provides many national and international opportunities for education and outreach. The proposed effort will leverage these opportunities to the fullest extent and continue the long-term record of high school, undergraduate and graduate student, and post-doctoral fellow involvement in the laboratory; K-12 educational efforts; and dissemination of results through high visibility publications and outreach to the public, popular media, and policy makers.
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