HR: 0800h
AN: C31A-1117    [Abstracts]
TI: Variability in Seasonal Freeze-Thaw in the Terrestrial High Latitudes and Their Relationships with Land-Atmosphere CO₂ Exchange: Characterization with Spaceborne Microwave Remote Sensing
AU: * McDonald, K C
EM: kyle.mcdonald@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Kimball, J S
EM: johnk@ntsg.umt.edu
AF: The University of Montana Flathead Lake Biological Station, 311 Biostation Lane, Polson, MT 59860 United States
AU: Kimball, J S
EM: johnk@ntsg.umt.edu
AF: NTSG, College of Forestry and Conservation, University of Montana, Missoula, MT 59812 United States
AU: Zhao, M
EM: zhao@ntsg.umt.edu
AF: NTSG, College of Forestry and Conservation, University of Montana, Missoula, MT 59812 United States
AU: Chan, S
EM: steven.chan@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Njoku, E
EM: eni.njoku@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AB: Landscape transitions between seasonally frozen and thawed conditions occur each year over roughly 50 million square kilometers of Earth's Northern Hemisphere. These relatively abrupt transitions represent the closest analog to a biospheric and hydrologic on/off switch existing in nature, affecting surface meteorological conditions, ecological trace gas dynamics, energy exchange and hydrologic activity profoundly. We utilize time series satellite-borne microwave remote sensing to examine spatial and temporal variability in seasonal freeze/thaw cycles for the pan-Arctic basin and Alaska. Regional measurements of spring thaw and autumn freeze timing are derived using daily brightness temperature measurements from the Special Sensor Microwave Imager (SSM/I), the Advanced Microwave Scanning Radiometer on EOS (AMSR-E), and the SeaWinds-on-QuikSCAT scatterometer. We examine relationships between freeze/thaw timing as related to sensor, satellite overpass time, and landcover. We compare these products with seasonal atmospheric CO₂ concentration anomalies derived from NOAA CMDL arctic and subarctic monitoring stations. Spatial and temporal patterns in regional freeze/thaw dynamics show distinct differences between North America and Eurasia, and boreal forest and Arctic tundra biomes. Annual anomalies in the timing of thawing in spring also correspond closely to those of the CO₂ measurements. Classification differences between AM and PM overpass data average approximately 5 days for the region, though both appear to be effective surrogates for monitoring annual growing seasons at high latitudes. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, and at the University of Montana, Missoula, under contract to the National Aeronautics and Space Administration.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0428 Carbon cycling (4806)
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
DE: 0702 Permafrost (0475)
DE: 0704 Seasonally frozen ground
SC: Cryosphere [C]
MN: Fall Meeting 2005