HR: 08:30h
AN: C31A-03    [Abstracts]
TI: Remote sensing of changes in near surface freeze and thaw timing from 1988 to 2006
AU: * Smith-Downey, N V
EM: nsdowney@fas.harvard.edu
AF: Harvard University, 29 Oxford St., Cambridge, MA 02138, United States
AU: Saatchi, S S
EM: saatchi@congo.jpl.nasa.gov
AF: NASA Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Randerson, J T
EM: jranders@uci.edu
AF: University of California, Irvine, 3212 Croul Hall, Irvine, CA 92697, United States
AB: We developed a technique to detect the date of near surface soil freeze and thaw using passive microwave satellite data from the SSM/I instrument. The difference between the 37 and 19 GHz channels is used as an indicator of soil freeze state. We generated a continuous record of freeze and thaw dates from 1988 to 2006 for all land areas north of 45 degrees north. Our analysis shows that the onset of fall freeze has moved progressively later (4 days/decade) in Boreal forests across the globe. Spring thaw is occurring earlier in tundra ecosystems (3 days/decade) and there has been a net increase in the growing season length in both Boreal (5 days/decade) and Tundra (4 days/decade) ecosystems globally. These results are compared to trends in surface air temperature and NDVI over the same period. Significant correlations between the annual anomalies in surface air temperature, average NDVI, and the freeze-thaw records exists for all biomes analyzed. This record is a new long-term metric of global climate change over the past 19 years.
DE: 0704 Seasonally frozen ground
DE: 0758 Remote sensing
DE: 1621 Cryospheric change (0776)
SC: Cryosphere [C]
MN: 2007 Fall Meeting