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Precipitation as a potential climate driver of NDVI trends in Southwest Alaska
Amy
Hendricks, University of Alaska Fairbanks, ashendricks@alaska.edu
Uma
Bhatt, University of Alaska, Fairbanks, usbhatt@alaska.edu
Gerald
Verner
Frost, Alaska Biological Research, Inc.--Environmental Research & Services, jfrost@abrinc.com
(Presenter)
Matthew
Macander, Alaska Biological Research, Inc.--Environmental Research & Services, mmacander@abrinc.com
Peter
Bieniek, University of Alaska, Fairbanks, pbieniek@alaska.edu
Mark
Torre
Jorgenson, Alaska Ecoscience, ecoscience@alaska.net
Changes to climatic properties such as precipitation are likely to modulate the effects of climate warming on Arctic vegetation. Satellite imagery has indicated a recent decline in vegetation productivity in southwest Alaska, in contrast to the rest of circumpolar Arctic where vegetation has mainly shown increasing productivity. The AVHRR-derived Normalized Difference Vegetation Index (NDVI), a measure of vegetation productivity, has indicated a recent significant negative trend in southwest Alaska’s Yukon-Kuskokwim Delta (YKD), since 1999. Across much of the Arctic, higher NDVI values have been linked to sea ice decline as diminishing sea-ice permits increased land surface warming near coastal regions. While the southwest Alaska (East Bering Sea) region has experienced a comparatively large increase in the summer warmth index, >10°C month, the region’s tundra vegetation has become less productive. Here evaluate whether changes in precipitation and total rainfall have been an important covariate with temperature increase in driving changes to Arctic vegetation productivity.
Six standard readily available, gridded, monthly datasets were chosen to examine trends in precipitation: CPC Merged Analysis of Precipitation, Global Precipitation Climatology Centre, Global Precipitation Climatology Project, National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis, NOAA’s Precipitation Reconstruction over Land, and University of Delaware Precipitation. Downscaled ERA-Interim data were used as a 30-year comparison climatology for the growing season, defined here as June–August. There is significant variability among the data sets, both in the spatial patterns of total precipitation and trends. The large variability between the data suggests high uncertainty in precipitation climatology across the state of Alaska.
We are investigating a 34-year period (1982-2015) of summer precipitation and NDVI to understand if the two trends are correlated. ERA-Interim shows a negative trend of approximately 30 mm over the 34-year period, while the ensemble average shows a very small positive trend of approximately 1 mm over the same period. NDVI trends have shown stronger negative values in the YKD for the later half of the period, 1999-2015, compared to the early half, 1982-1998. Preliminary results show stronger negative precipitation trends in the later period for the majority of datasets compared to the earlier period, however, ERA-Interim shows a slightly positive precipitation trend in the later period. Currently we are dissecting the precipitation trend variability and discrepancies before correlating the spatial and temporal correlation calculations to NDVI.
Presentation:
ASTM4_Poster_Hendricks_1_113.pdf (52649k)
Associated Project(s):
Poster Location ID: 1
Session Assigned: Wildlife and Ecosystem Services
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