Collaborative Research: Impacts of Global Change on Terrestrial Mercury in the Arctic

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Northern hemisphere permafrost contains a large amount of mercury (Hg) bound to frozen organic matter. The Arctic is warming at two to three times the global average rate. As permafrost thaws, microbial decay of the organic matter will resume, releasing mercury into the environment. The scientific community lacks the process-based terrestrial mercury models needed to understand the impacts of permafrost thaw on the Arctic and global mercury cycles. This project will build such models by leveraging existing models of the terrestrial carbon cycle to advance our understanding of terrestrial mercury processes in permafrost regions at multiple temporal and spatial scales. The project will use these models to predict the pan-Arctic and global impacts of Hg released from thawing permafrost. For the first time, this project will reveal the emergent behavior of two linked components of the Arctic system: the carbon and mercury cycles.This project will leverage and enhance existing models to evaluate how Hg from thawing permafrost will influence the Arctic and global Hg cycles. The project has two objectives: 1) Quantify how different environmental conditions affect Hg accumulation with associated uncertainties; and 2) Quantify how Hg released from thawing permafrost impacts the global Hg cycle with associated uncertainties. This project uses three models of the terrestrial Hg cycle: 1) the full-physics Simple Biosphere Carnegie-Ames-Stanford Approach (SiBCASA) model; 2) the Global Terrestrial Mercury Model (GTMM) coupled to 3-D atmospheric transport and ocean circulation models; and 3) a simple Global Biogeochemical Box Model (GBBM). Simulations from 1400 to 2300 CE using SiBCASA will provide estimates of future Hg releases from thawing permafrost. Simulations with GTMM will quantify global impacts of Hg released from thawing permafrost. Monte Carlo simulations with GBBM will quantify uncertainty. These models require enhancement based on the latest knowledge of Hg uptake and release pathways. These enhancements include new biogeochemical pools such as soil water, new processes such as fire, and new computational techniques such as Monte Carlo simulations. The Broader Impacts of this project include the mentoring of early-career researchers, the organization of a training workshop to bridge the Hg and carbon research communities, and the production of publicly available products, which include an updated Hg emissions dataset, the models themselves, output from the models, and an on-line tool to visualize the model results. This project leverages extensive knowledge of terrestrial carbon pathways to parameterize Hg pathways and couple the terrestrial Hg and carbon cycles.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.