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Impacts of Soil Freeze/Thaw Dynamics on the North American Carbon Cycle

NASAThis project is funded by NASA


To understand the role of freeze-thaw processes in determining seasonal and interannual variability in terrestrial biomass, photosynthesis, respiration, and net CO2 fluxes over continental North America


Tingjun Zhang is the PI; and Kevin Schaefer and Lixin Lu (CIRES) are Co-Investigators.

Project Summary

We are investigating how winter snow cover, soil temperature, and soil freeze/thaw dynamics influence carbon fluxes and biomass. Understanding the potential fate of the large amount of frozen soil carbon in permafrost regions is essential to long-term climate predictions.

We will integrate remote sensing data sets, ground-based measurements, and numerical modeling to quantify the effects of soil temperature, soil freeze-thaw dynamics, and snow cover on seasonal to interannual variability in the North American terrestrial carbon cycle. Using remote sensing products, in situ observations, and a soil thermodynamic model, we will estimate soil temperatures and snow cover over North America at 25-kilometer resolution for North America from 1981 to 2003 (23 years). We will feed these estimated soil temperatures and snow cover, along with additional remote sensing data, into an ecosystem model to estimate biomass and net carbon fluxes. Both models will use the North American Regional Reanalysis, so the resulting estimates of soil thermodynamic properties, biomass, and carbon fluxes will be optimally consistent with each other and with actual weather conditions in North America. We will statistically analyze these optimal carbon fluxes to understand the environmental drivers and biophysical responses regulating the spatial patterns and temporal variability in the North American terrestrial carbon cycle. Using standard Monte Carlo techniques, we will quantify uncertainty in our estimated carbon fluxes. Lastly, we will perturb our input data to assess the sensitivity of our estimated fluxes to long-term climate change.

Our research addresses the North American Carbon Program (NACP) goals of reducing uncertainty about the buildup of greenhouse gases in the atmosphere and the dynamics of the carbon cycle. Specifically, we address the following NACP goals:

  1. Quantifying the magnitudes and distributions of terrestrial carbon sources and sinks within North America
  2. Understanding the processes controlling carbon source and sink dynamics
  3. Producing consistent analyses of the carbon budget of North America, explaining regional contributions and year-to-year variability

We will archive data products generated by this investigation at the National Snow and Ice Data Center's Frozen Ground Data Center (FGDC) for access by other NACP investigators and for general use by the scientific community.

Related Resources

NSIDC Frozen Ground Data Center (FGDC)

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