Northern Carbon Cycle
Terrestrial Ecology and Land cover / Land use Change programs; NSF
Office of Polar Programs;
of Montana; NASA Jet Propulsion Laboratory; University of Alaska
Fairbanks, San Diego State University; University of New Hampshire.
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.
Arctic Linkages Experiment (http://picea.sel.uaf.edu/projects/wale.html)
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
- 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
- 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),
- 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.