HR: 0800h
AN: B21A-0041    [Abstracts]
TI: Trends of Vegetation Greenness in the Arctic from 1982-2005
AU: * Jia, G J
EM: jiong@tea.ac.cn
AF: RCE-TEA, Institute of Atmospheric Physics, CAS, 40 Hua Yan Li, PO Box 9804, Beijing, 100029, China
AU: * Jia, G J
EM: jiong@tea.ac.cn
AF: University of Virginia, Environmental Sciences 291 McCormick Rd., Beijing, VA 22903, United States
AU: Epstein, H E
EM: hee2b@virginia.edu
AF: University of Virginia, Environmental Sciences 291 McCormick Rd., Beijing, VA 22903, United States
AU: Walker, D A
EM: ffdaw@uaf.edu
AF: University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775, United States
AB: The Arctic region has experienced a continuous trend of warming during the past 30 years. Meanwhile, many areas of the Arctic are undergoing large-scale industrial development, e.g. oil and gas exploration, at a rapid pace, indicating an increasing human pressure and land use changes even in this frontier wilderness. Major questions face arctic terrestrial ecologists are what will happen to the tundra ecosystems as the global climate warms and what will happen to the indigenous people way of life as land cover changes proceed? Here, we combine multi-scale sub-pixel analysis and remote sensing time-series analysis to investigate recent decadal changes in vegetation photosynthetic activity along spatial gradients of summer temperature and vegetation in the Arctic. The datasets used here are NASA Gimms data at 8 km pixel resolution and MODIS land cover data. Fractional vegetation cover was analyzed in order to select homogenously vegetated areas of tundra and autoregression analysis was performed on time series of those homogenous pixels. Only pixels below 70 degree north were included for 2004-2005 due to calibration errors occurred beyond 70 degree north for those years. Linear trends in Arctic tundra vegetation greenness over period 1982-2005 were positive. However, there were different magnitudes between Eurasia and North America. The rate of change was +0.64%/yr over North American Arctic compared to +0.44%/yr over Eurasian Arctic. Vegetation productivities increase from north to south along bioclimatic gradient, therefore, greenness is much higher in areas below 70 degree north compared to entire tundra biome. Higher rates of greening in High Arctic contributed to a stronger positive trend in the longer time series. The rate of greening detected here was higher than that reported in previous studies. This is likely due to two reasons: 1) we restricted our study area in tundra biome only with a phenological tundra-taiga boundary identification approach, therefore, have less chance to mix information of boreal forest in the south; 2) we applied homogenous vegetation approach to avoid noise from lakes and bare ground and more likely detect initial changes over tundra vegetation.
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
DE: 0718 Tundra (9315)
DE: 1621 Cryospheric change (0776)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1640 Remote sensing (1855)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting