Satellite observations of Pan-Arctic Terrestrial Net Primary Productivity from 1982-2005
Ke
Zhang, University of Montana, richard_k_zhang@hotmail.com
John
S
Kimball, University of Montana, johnk@ntsg.umt.edu
(Presenting)
Ted
Hogg, Canadian Forest Service, Natural Resources Canada, Northern Forestry Centre, thogg@nrcan.gc.ca
Maosheng
Zhao, University of Montana, zhao@ntsg.umt.edu
Walt
Oechel, San Diego State University, oechel@sunstroke.sdsu.edu
Steve
W
Running, University of Montana, swr@ntsg.umt.edu
We applied the MOD17A2 production efficiency model (PEM) using AVHRR PAL and MODIS LAI/FPAR time series with NCEP reanalysis daily surface meteorology to assess terrestrial NPP for the pan-Arctic basin and Alaska from 1982 to 2005. We integrated the AVHRR and MODIS time series on a pixel by pixel basis by empirical adjustment of the AVHRR record using land cover specific regressions of overlapping NPP results for 2000. We then analyzed spatial patterns, temporal anomalies and trends in NPP over the 24 year record. Sensitivity analysis of the production efficiency model to uncertainties in surface meteorological inputs indicates that NCEP surface temperatures and solar radiation are the primary sources of PEM based NPP uncertainty for the region. Despite these uncertainties the reanalysis product captured the major annual anomalies and trends in surface meteorology for the domain. NPP for the domain showed generally widespread positive productivity trends from 1982 to 1997 followed by a significant productivity decline after 1997. The spatial pattern of 24-yr trends showed significant increases across southern Alaska and south-central Eurasia (P<0.01), and significant NPP declines across central Canada (P<0.05) and southeast Eurasia (P<0.01). Major NPP positive and negative annual anomalies are attributed to relatively warm and cool years, respectively, while NPP anomalies are also examined relative to regional droughts.