RAPID: Investigation of Microbial:Black Carbon feedback Processes that Impact Icefield Melt in High Latitude Systems.

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Solar radiation is a primary driver of melting glacial ice and snow. Glaciers and high-elevation mountain snowpacks are therefore especially sensitive to even small changes in the concentration of light absorbing particles. Surface melt of snow and glacial ice is substantially higher if impurities such as mineral dust and organic matter are present in significant quantities. Bacteria and algae further promote darkening of the glacial surface and melting by aggregating these impurities in the form of biofilm. Like many mountain glaciers of the Alaskan region, the Juneau Icefield has seen extensive mass loss. Between 2005-2019 alone, sixty-three glaciers have disappeared. Models predict that the entire icefield will display a negative mass balance by the mid-21st century, with surface melt likely the driving mechanism of Alaskan glacier loss. Black carbon released by human and natural activities has become a major contributor to reducing snow and ice albedo. Microbes can affect the dynamics of black carbon on glacial surfaces, with biodegradation having profound implications on its residence time, light absorbance, and output to adjacent and downstream aquatic ecosystems.The proposed research leverages a Facilities Integrating Collaborations for User Science (FICUS) grant from Pacific Northwest National Laboratory (PNNL). The analytical support, access to state-of-the-art instrumentation, and expertise provided by the FICUS award will accelerate the speed of this timely research. The goals of the proposed study are to determine (i) the anthropogenic perturbation of the glacial carbon cycle due to black carbon depositions and (ii) degradation and transformation of black carbon by microbes. This project supports the necessary field work and associated costs, resources to disseminate results, and student involvement in sample analysis. Given the demonstrated sensitivity of the Juneau Icefields to ice loss and the broad implications for society and the environment it is timely and relevant to explore the relationship between black carbon-microbial processing-and ice loss, as well as determine how these complex interactions shape the fate of ice field and glacial environments.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.