PARENT SESSION
Oral Session #33: Climate Change. Presiding: A. Peterson.
Tuesday, August 7, 2001. 1:00 PM to 5:00 PM. Hall of Ideas E.
Temporal Characteristics of AVHRR-NDVI for the Arctic Tundra in Northern Alaska, 1990-1999.
Jia, Gensuo1, Epstein, Howard1, Walker, Donald2, 1 2
ABSTRACT- In this study, we examined the 1990-1999 annual changes of peaks of AVHRR-derived normalized difference vegetation index (NDVI) for arctic tundra, as well as the onset time changes based on NDVI values. A 10-year biweekly AVHRR images time series was used to calculate and analyze the annual temporal patterns of NDVI for the tundra landscapes in northern Alaska. There are two major approaches in the study: 1) Difference of peak NDVI and onset time between periods of 1990-91, 1994-95, and 1998-99 were examined for the whole study area, using spatial analyses; 2) some areas of moist acidic tundra (MAT) and moist nonacidic tundra (MNT) were analyzed in detail for the entire 1990-1999 NDVI time series. In general, these analyses indicate that there was a trend towards earlier onset of greenness from 1990 to 1999 and higher peak greenness from 1992 to 1999. However, there is an initial drop in peak greenness values after 1991, which may have been due to atmospheric perturbations caused by the 1991 Mt Pinatubo eruption. By removing the year of 1992, a gradual increase of peak NDVI can be observed through this time series. Major NDVI changes (10%) occur in the Brooks Mountain Range in the south, while some changes also occur in the coastal region, especially around Prudhoe Bay, but there is almost no change of over 10% in the Foothills region. Both MAT and MNT sites show the similar trend of peak NDVI increasing, though the increasing NDVI in MAT is more significant than MNT. Climate data show some relations with NDVI changes, but they do not always correlate with these findings, therefore more detailed NDVI-climate analyses will be done.
KEY WORDS: NDVI, Arctic tundra, Alaska, Temporal change