Northern Carbon Cycle

Principal Investigator:

Funding agencies:

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Project Summary:

The seasonal transition of the land surface from a frozen to thawed state represents the closest analog to a biospheric on/off switch existing in nature, initiating a number of terrestrial processes that are virtually dormant under frozen conditions. Landscape freeze/thaw transitions coincide with marked shifts in albedo, surface energy and mass exchange, including ecological trace gas, snow and river runoff dynamics. This abrupt state transition occurs each year over roughly 50 million km2 of the Earth's terrestrial surface. In any given year, the timing of seasonal thaw can vary by up to 6 weeks or more with significant impacts on regional hydrologic and ecological processes. We are currently working to enhance capabilities for regional assessment and monitoring of these processes from spaceborne satellites using active and passive microwave remote sensing and regional ecological process models. This information is being used with other information derived from regional monitoring networks, field experiments and modeling studies to better understand the role of boreal and arctic biomes in global energy, water and carbon cycles and the potential response of this region to global change.

 Related Project Websites:

Western Arctic Linkages Experiment (http://picea.sel.uaf.edu/projects/wale.html)
NASA Freeze Thaw Transition project site (http://www.forestry.umt.edu/ntsg/RemoteSensing/freezethaw/freezethaw.htm)

 

Related Project Papers

• Amthor, J. S., J. Chen, J. Clein, S. Frolking, M. Goulden, R. Grant, J. Kimball, A. King, A. McGuire, N. Nikolov, C. Potter, S. Wang, and S. Wofsy, 2001. Boreal forest CO2 exchange and evapotranspiration predicted by nine ecosystem process models: Inter-model comparisons and relationships to field measurements. Journal of Geophysical Research 106(D24), 33,623-33,648.
• Frolking S., K. McDonald, J. Kimball, R. Zimmermann, J.B. Way and S.W. Running, 1999. Using the space-borne NASA Scatterometer (NSCAT) to determine the frozen and thawed seasons of a boreal landscape. Journal of Geophysical Research 104(D22), 27,895-27,907.
• Keyser, A.R., J.S. Kimball, R.R. Nemani and S.W. Running. 2000. Simulating the effects of climate change on the carbon balance of North American high latitude forests. Global Change Biology 6(1): 185-195.
• Kimball, J.S., A.R. Keyser, S.W. Running and S.S. Saatchi. 2000. Regional assessment of boreal forest productivity using an ecological process model and remote sensing parameter maps. Tree Physiology 20, 761-775.
• Kimball, J.S., K.C. McDonald, S. Frolking and S.W. Running. 2002. Radar remote sensing of the spring thaw transition across a boreal landscape. Remote Sensing of Environment, BOREAS Special Issue (in press).
• Kimball, J.S., K. McDonald, A.R. Keyser, S. Frolking and S.W. Running. 2001. Application of the NASA Scatterometer (NSCAT) for determining the daily frozen and non-frozen landscape of Alaska. Remote Sensing of Environment 75: 113-126.
• Kimball, J.S., S.W. Running and S.S. Saatchi, 1999. Sensitivity of boreal forest regional water flux and net primary production simulations to sub-grid scale landcover complexity. Journal of Geophysical Research 104(D22), 27,789-27,801.
• Potter, C.S., J.S. Amthor, J.M. Chen, J.S. Clein, S.E. Frolking, R.F. Grant, J.S. Kimball, A.W. King, A.D. McGuire, N.T. Nikolov, and S. Wang, 2001. Comparison of boreal ecosystem model sensitivity to variability in climate and forest site parameters. J. Geophys. Res. 106(D24), 33,671-33,688.
• Running, S.W., J.B. Way, K. McDonald, J.S. Kimball, A.R. Keyser, S. Frolking and R. Zimmermann, 1999. Recent advances in the use of satellite radar data to monitor freeze/thaw transitions in boreal regions. Eos 80(19), 213-221.
• Running, S.W., J.B. Way, K. McDonald, J.S. Kimball, S. Frolking, and A.R. Keyser, 2000. Radar remote sensing proposed for monitoring freeze-thaw transitions in boreal regions. Earth in Space 12(5), 5-9.