Collaborative Research: CHemistry in the Arctic-Clouds, Halogens, and Aerosols (CHACHA)

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This project aims to improve understanding of atmospheric chemistry that impacts ozone, particulate matter, and cloud chemical composition in the context of a rapidly changing Arctic. The atmosphere converts pollutants by processing them into water-soluble products that are removed through precipitation (rain or snow) or by deposition onto Earth’s surface. This chemical conversion of pollution happens through a sunlight-driven (photochemical) process known as oxidation. Most of what is known about these atmospheric processes comes from measurements made at the surface in Arctic coastal environments. The CHACHA team plans to use two instrumented aircraft to conduct airborne measurements around the Chukchi Sea, the Beaufort Sea, and the Alaska North Slope region. They plan to target features that are rapidly changing - above and downwind of sea ice "leads" (areas of open water in otherwise sea-ice-covered ocean regions), and downwind of sources of combustion-derived pollutants. Researchers will also use collected data to develop atmospheric models that will be openly available for use by the broader scientific community. The team is composed of researchers at six United States universities (in Alaska, Indiana, Michigan, Pennsylvania, and New York) and will mentor a diverse group of students and postdoctoral scholars. Researchers will also engage in several additional education and outreach activities, including an “aircraft open house” and an annual three-day Science Fair in Utqiaġvik, AK. Overall, this project will enable the United States to better understand how rapid change in the Arctic impacts the chemical composition of the atmosphere and to translate what was learned to other regions - including the atmosphere above the world's oceans and in Earth's upper atmosphere. In addition, this project is co-funded by the Arctic Natural Sciences and Atmospheric Chemistry programs.This project will improve understanding of atmospheric halogen chemistry in the gas, aerosol, and cloud water phases, with a focus on how that chemistry is impacted by Arctic sea ice loss and fossil fuel extraction. The CHACHA team plans to conduct eight weeks of observations during the Arctic spring, when halogen chemistry is most active, using two aircraft: the University of Wyoming King Air and the Purdue University Airborne Laboratory for Atmospheric Research (ALAR). Aircraft will conduct complementary sampling upwind and downwind of leads (sea ice fractures), over snow-covered tundra, and downwind of the North Slope of Alaska oilfields. Sampling will occur at various altitudes from the near-surface through the boundary layer and into the free troposphere. The team will prioritize measurement of various greenhouse gases (including O3, CO2, CH4, H2O), reactive trace gases (including NO2, SO2, N2O5, HO2NO2, bromine- and chlorine-containing gases), aerosol size distributions and composition, cloud residual particle composition, and cloud particle size distributions, as well as atmospheric data. These observations will be interpreted in part using 0-D and 1-D photochemical models and a cloud parcel model, to evaluate and advance understanding of multi-phase reactions and the vertical and horizontal propagation of atmospheric halogen chemistry in the Arctic. This dataset will improve understanding of the impact of the rapidly changing Arctic on halogen chemistry and atmospheric composition, as well as to provide fundamental knowledge of halogen chemistry that can be applied globally through models. The team will mentor students, postdocs, and conduct an array of unique outreach and educational activities.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.