Collaborative Research: Arctic Stream Networks as Nutrient Sensors in Permafrost Ecosystems

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Permafrost is ground that remains frozen for at least two consecutive years. It is found approximately one fourth of the northern hemisphere's land surface and contains large stores of carbon and nutrients such as nitrogen and phosphorus. As Arctic Alaska warms and permafrost thaws, these nutrients are released, which supports plant growth but also can accelerate the production of greenhouse gases, affecting local habitat and strengthening the permafrost climate feedback. Because snowmelt and rain transport some nutrients from land to water, variations in nutrient concentrations within Arctic stream networks can reveal where permafrost nutrients are released and why some areas release more than others. This research greatly improves understanding of how water flow, plant life, and conditions in the soil and bedrock are affected by wildfire, permafrost degradation, and extreme weather conditions. Such knowledge is crucial to protect Arctic communities and forecast how environmental change in the permafrost region could disrupt climate and weather patterns throughout the U.S. This project also transfers improved understanding of the Arctic system directly to the public by creating a network of researchers, writers, performers, and outreach organizations that 1) visits local communities in the Arctic, 2) creates a children?s book inspired by Arctic systems, 3) brings Arctic systems and climate science directly to about 30,000 high school students, and 4) connects remotely with K-12 classrooms in rural Alaska and the contiguous U.S. via video chats.The project applies a combination of novel and conventional approaches to quantify nutrient dynamics across scales and biomes. 1) High-resolution spatial sampling of stream network chemistry and high-frequency monitoring at watershed outlets quantify lateral carbon and nutrient flux across ecosystem gradients (e.g. Arctic-Boreal and coastal-upland) and scales (0.1 to 1,000 square kilometers). 2) Robust nutrient-limitation assays and tracer injection methods estimate the magnitude of instream removal and release of nutrients in locations that exert a strong influence on watershed-scale nutrient flux. 3) Spatial analysis, statistical modeling, and geochemical tracers link multi-scale nutrient fluxes with ecohydrological characteristics and thus identify drivers of hydrochemical change in the Arctic. The spatial and temporal data collected by the project test a series of long-standing and emerging hypotheses about how active-layer thickness, vegetation community, topography, hydrology, and current and past wildfire and permafrost degradation interactively influence carbon and nutrient flux. More generally, this research generates multi-scale targets for earth system models that incorporate lateral and longitudinal nutrient flux, reducing one of the largest sources of uncertainty in predicting net ecosystem carbon balance of the permafrost region.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.