ABSTRACT

In a warmer world, the Arctic is projected to become cloudier and rainier. As the Arctic warms more than twice as fast as the rest of the world, resulting changes in clouds can subsequently affect sea ice extent, permafrost thaw, and regional and global weather. However, the formation and evolution of Arctic clouds remain highly uncertain in part due to a limited understanding of airborne particles known as aerosols that seed clouds, specifically aerosols that form cloud ice crystals. These ice crystals, called ice nucleating particles or INPs, can originate from soil, plants, oceans, lakes, and rivers. In particular, the sources and abundance of INPs from Earth?s biome are poorly understood yet may be crucial for cloud ice formation. Warmer temperatures are also triggering rapid and extensive permafrost thaw at high latitudes, which has implications for communities and wildlife living in these regions. Thawing permafrost additionally releases greenhouse gases and promotes metabolic activity in microbes such as bacteria?suggesting the intriguing possibility that as permafrost thaws, the microbes themselves and their byproducts could be released into lakes, rivers, and the ocean, and potentially into the atmosphere to impact cloud formation. However, permafrost has not been previously evaluated as a source of seeds for clouds. Because permafrost covers approximately 15% of Northern Hemisphere land, this novel but potentially widespread INP source may be important for predictions of Arctic clouds.

The overarching hypothesis of this project is that INPs released from thawing permafrost significantly influence cloud properties in the Arctic. The field deployment called ARCSPIN (ARCtic Study of Permafrost Ice Nucleation) involves collection and measurement of INPs in permafrost soil, lake water, river water, and aerosols at two NSF-supported facilities on the North Slope of Alaska. Additionally, this study leverages existing NSF shipborne opportunities to collect aerosol and seawater samples from the Bering and Chukchi Seas for INPs. Land-based measurements provide a detailed assessment of permafrost INP sources, while the shipborne measurements clarify the spatial reach of such INPs. The researchers use climate and earth system models to tie together observations in terrestrial and marine environments, and to assess the effects of clouds formed by permafrost INPs on sunlight and heat in the broader Arctic region. The proposed joint observational-modeling study advances the understanding of the Arctic as a coupled system through an interdisciplinary approach to assess interactions among physical, biological, and atmospheric climate system processes.

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.

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