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Investigating sensitivity of soil freeze/thaw dynamics and cold-season respiration to snow cover changes in Alaska

Yonghong Yi, University of Montana, yonghong.yi@ntsg.umt.edu (Presenter)
John Kimball, University of Montana, johnk@ntsg.umt.edu
Donatella Zona, San Diego State University, d.zona@sheffield.ac.uk
Kyle Arndt, San Diego State University, karndt-w@sdsu.edu
Richard Chen, University of Southern California, chenrh@usc.edu
Mahta Moghaddam, University of Southern California, mahta@usc.edu
Rolf Reichle, NASA Goddard Space Flight Center, rolf.reichle@nasa.gov
Walter Oechel, San Diego State University, woechel@mail.sdsu.edu

The contribution of cold season respiration to the boreal-arctic carbon cycle and its potential feedback to climate change remain poorly quantified. Here, we developed an integrated modeling framework combining airborne low frequency (L+P-band) radar retrievals and landscape level (≥1km) satellite environmental observations with a detailed permafrost carbon model to investigate underlying processes controlling soil freeze/thaw (FT) dynamics and cold season CO2 respiration in Alaska. The permafrost carbon model simulates snow cover and soil thermal dynamics with soil water phase change included and accounts for soil carbon decomposition up to 3m below surface. Initial comparisons with tower-based measurements show that the model can well capture the soil temperature dynamics and seasonality of cold season respiration in both tundra and boreal forest areas, with large CO2 emissions in late fall and early winter that gradually diminish over the winter. Model outputs include active layer thickness (ALT) and regional carbon fluxes at 1-km resolution spanning the recent satellite era (2001-present) across Alaska. The regional simulations indicate that vegetation productivity plays a major role in controlling the total soil carbon respiration, while snow cover changes are dominant in controlling the relative contribution of different soil depths to total soil carbon emissions. In the future work, radar retrievals of soil moisture and soil organic carbon (SOC) will be used to improve the regional parameterization of the permafrost model; airborne atmospheric CO2 measurements will also be used to evaluate model processes controlling cold season respiration, particularly how a deeper unfrozen active layer with warming may contribute to changes in cold season respiration.

Associated Project(s): 

Poster Location ID: 27

Session Assigned: Carbon Dynamics

 


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