Spatiotemporal Dynamics of CO2 Gas Exchange From Headwater Mountain Streams

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• CO2 Gas Exchange from Mountain Streams

Researchers at the USGS are studying mountain streams in Rocky Mountain National Park to determine how these systems contribute to the global carbon (C) cycle. In mountain landscapes, part of this cycle includes the flux, or transfer, of carbon between streams and the atmosphere in the form of CO₂ gas exchange. Historically, researchers believed mountain streams contributed relatively small amounts of CO₂ (a greenhouse gas) to the atmosphere; however, a 2019 study by Horgby and others suggested that high turbulence in steep mountain streams may cause high

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• Loch Vale Meteorological Data
• Andrews Creek Stream Gage Data

CO₂ exchange rates and greater contributions to the global evasion flux than previously thought. By studying the timing and quantity of CO₂ gas exchange in mountain streams like those in RMNP, researchers can better constrain their global contribution to atmospheric CO₂ and to what extent these systems may influence warming and climate change.

The USGS researchers found that precipitation events flush carbon from soils into streams, driving stream CO₂ concentration and subsequent CO₂ gas exchange at short time scales.
 

Loch Vale Outlet in RMNP.

NPS Photo

At seasonal scales, CO₂ concentrations in Rocky Mountain streams were strongly related to the accumulation and melt of snow. In winter, the snowpack acts as a barrier, limiting gas exchange between streams and the atmosphere and increasing aquatic CO₂ concentrations in streams. During peak snowmelt, exchange increases strongly as the snowpack melts and runoff flushes CO₂ from soil into streams

At annual scales, researchers found that stream CO₂ concentrations and CO₂ evasion fluxes were positively related to the amount of annual precipitation. Current climate models predict changes in precipitation types and patterns under warming temperatures. The relationship between precipitation patterns and CO₂ concentrations and fluxes described in this study suggest that climate-driven changes in precipitation may induce positive or negative feedback loops between aquatic, terrestrial, and atmospheric components of the global carbon cycle.

Meet the Scientist

David Clow is a research hydrologist with the U.S. Geological Survey based in Denver. He graduated with a Ph.D. in geochemistry from the University of Wyoming in 1992.

"Place-based science in highly instrumented sites like Loch Vale allow researchers to dig deeply into mechanisms and processes that control how natural systems work, and how they respond to perturbations, like air pollution or climate change."