2024 Abstracts

Dynamics of Interconnected Surface-Subsurface Flow and Reactive Transport Processes Across the Hillslope-Riparian Zone River Corridor Continuum of Cold, High-Latitude Watersheds


M. Bayani Cardenas1* (cardenas@jsg.utexas.edu), Bethany T. Neilson2, Pin Shuai2, Rose M. Cory3, George W. Kling3, Neelarun Mukherjee1, Bo Gao4, Ethan T. Coon4


1University of Texas, Austin, TX; 2Utah State University, Logan, UT; 3University of Michigan, Ann Arbor, MI; 4Oak Ridge National Laboratory, Oak Ridge, TN


The Arctic is warming almost four times faster than the rest of the world and is in the process of thawing large stores of permafrost soil carbon (C). The conversion of soil C to greenhouse gases within watersheds is controlled by redox chemistry that is, in turn, controlled by how water flows through the soils from hillslopes to valley bottoms to streams. Watersheds are shifting in response to dramatic changes in extreme weather events like heat waves, flooding and storms, and more frequent wildfires, along with a shorter cold season and longer summer thaw season. The need is to improve models of cold-region watershed hydrology and biogeochemistry in order to predict how warming and permafrost thaw will affect greenhouse gas release in the future.

This research is integrating models of highly dynamic water flow over the landscape, through soils, and to rivers with key physical, biological, and chemical processes that control greenhouse gas generation and transport. Realistic coupling of the hydrology, biology, and chemistry in these models will be validated by key field observations. Expectations are that (1) hydrological flow patterns from hillslopes through valley bottoms control the landscape export of C from soils to rivers and the relative production of carbon dioxide versus methane; (2) variability in extreme events, freeze-thaw cycles, and day-to-day weather will alter the magnitudes of biological and chemical reactions through the hillslope to valley bottom and then to the river; and (3) watershed-scale C exports are controlled by valley-bottom processes, but hillslope and stream processes can dominate as climate change alters weather patterns and hydrology. Researchers will test these ideas under scenarios of shifting cold- and warm-season climate, by adding novel physics and chemistry to two coupled DOE models, the Advanced Terrestrial Simulator model for thermal hydrology and PFLOTRAN for reactive chemical transport.