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River Stories: Using Aquatic Signals to Detect Change in Arctic Watersheds

Speaker: Dr. Arial Shogren, The University of Alabama 

The Arctic region is warming at twice the rate of the rest of the planet, releasing terrestrially-stored carbon and nutrients that were previously frozen in permafrost soils. As a result of a rapid and accelerating climate change, there is strong evidence for the enhanced delivery of nutrients and carbon from land to water, suggesting that changes in river chemistry can be used as a major indicator of broad ecosystem-level change. However, identifying what is causing these changes in nutrient processing and flux remains a challenge as most long-term records of Arctic river chemistry are from large rivers that are sampled at low spatial and temporal resolution.

Dr. Shogren will present results from studies meant to fill this knowledge gap using both 1) spatially-intensive and 2) temporally-extensive river chemistry data from three watersheds associated with the Long-Term Ecological Research (LTER) site at Toolik Field Station: the Kuparuk River (low-gradient tundra), Oksrukuyik River (lake-dominated tundra), and Trevor Creek (high-gradient alpine). 

First, using spatial “ synoptic” sampling, Arial and colleagues found that the dominant spatial samples controlling organic carbon (C) and major nutrient (e.g., Nitrogen, N) fluxes were 3-30 km2, indicating a continuum of diffuse and discrete sourcing and processing dynamics. These patterns were consistent seasonally, suggesting that relatively fine-scale landscape patches drive solute generation in this region. Second, the high-frequency monitoring efforts provide critical insights into the importance of late-summer storm events that drive nutrient and carbon exports from permafrost-underlain Arctic landscapes. 

Ultimately, while frozen permafrost represents a physical constraint in Arctic biogeochemistry and hydrology, ecological conditions from stream-lake connections and terrestrial productivity modulate spatial and temporal patterns of N and C fluxes throughout the summer season. These network-scale empirical frameworks guide and benchmark future Earth system models seeking to represent lateral and longitudinal solute transport in rapidly changing Arctic landscapes.