Microbial Oceanography Links to New aerosols in Ice-covered Regions (MjOLNIR) in the Arctic Ocean

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The most dramatic environmental changes occurring on the Earth today are taking place in the Arctic Ocean. Recent models predict that complete summertime Arctic sea ice loss will likely occur in the first half of the 21st century. The rapidly-declining areal expanse of summer pack ice will lead to changes in microbial community structure and production within both sea-ice communities and in the open waters of the Arctic Ocean. As summer sea ice microbial communities are replaced by open ocean populations, identifying changes in chemical compounds, such as various aerosols, that are released to the atmosphere might play a significant role in determining the future rate and impact of sea ice decline. The aerosols produced by microorganisms will ultimately move across the sea to air boundary and could affect cloud formation and with feedbacks that impact the Arctic system. In this study, the investigators will use state-of-the art methods to measure the relative abundances of aerosols that are associated with the microbial communities found in sea ice, melt ponds, sea ice leads, and in the open ocean. Better understanding of the changes in the structure of these microbial communities will provide new information for the next generation of models and may lead to more sophisticated understanding of various climate feedback loops. In addition, the project involves a collaboration with Swedish polar researchers and will strengthen scientific linkages between scientists in the USA and Sweden. The project will support training for graduate and undergraduate students, and the investigators will share research results with the public through lectures, as part of the Cultivate Program, and social media. The investigators will investigate how in-situ microbial community composition and productivity in contrasting sea-ice and open-ocean Arctic ecosystems impact the production and release of biogenic, volatile organic carbon (VOC) compounds. These VOC compounds are instrumental in the release and production of aerosols that ultimately form cloud condensation nuclei. In addition, the investigators will perform shipboard manipulative experiments to determine the effects of elevated sea surface temperatures, enhanced light intensities, and lower salinities resulting from melting sea ice and enhanced water column stratification. These changes will impose physiological stress on microbial communities that is likely to impact both phytoplankton community structure and the flux of the biogenic sulfur trace gas dimethylsulfide (DMS). The investigators will test how temperature, salinity, and light will affect the composition of the microbial community and thereby the catabolic fate of the DMS precursor dimethylsulfoniopropionate (DMSP), to yield either DMS or methanethiol and methane (CH4). In addition, the investigators will test whether the high CH4 concentrations observed in Arctic Ocean surface waters are due to DMSP catabolism or, alternatively, the breakdown of methylphosphonate. Using state-of-the-art instrumentation, they will monitor VOC fluxes using a shipboard Proton Transfer Reaction Mass Spectrometer (PTR-MS), a Membrane Inlet Mass Spectrometer, and high speed sorting flow cytometer to measure VOCs, net community production, and microbial community composition, respectively. They will make direct measurements of VOCs within sea ice by using a newly developed ice crusher attached to the PTR-MS to provide new in-situ data on the concentrations of DMS and CH4 in sea ice communities.