Examining Tundra Greening from Ground-based to Satellite Observations

Ongoing ground data collections of tundra spectral reflectance begun in 2010 near Utqiaġvik (Barrow) and Atqasuk, on the Alaskan North Slope provide a unique opportunity to link ground measurements to moderate-resolution satellite observations, illuminating how surface characteristics relate to arctic greening inferred from satellite data. Visible-Near Infrared spectral reflectance measurements are collected at 30 points arranged in a 5x6 grid pattern separated by 100 m within the Circumpolar Active Layer Monitoring (CALM) grid providing a repeatable set of measurements that sample areas the size of a MODIS pixel. Ground measurements are collected multiple times during the growing seasons to temporally sample seasonal growth. From training data collected nearby, relationships were developed relating spectral reflectance and ecological variables including: coverage of different vegetation types, ecosystem gross primary productivity, and chlorophyll content. We apply these algorithms produce descriptions of surface characteristics at the MODIS pixel scale. These data are examined to evaluate trends in biophysical variables and Normalized Difference Vegetation Index (NDVI) at local to MODIS pixel scales to evaluate year to year change along with decade-long trends.