Coarse-Resolution Daily Inundation Dynamics over the Alaska-Yukon Region: Comparison with High-Resolution Inundation Products and Influences from Atmospheric Drivers

Natural wetland complexes are a major source of atmospheric methane which is an important greenhouse gas. Wetland surface water variations and associated methane production are tightly linked and highly dependent on both climate and available plant material. Hence, characterizing the extent and distribution of wetlands is crucial in understanding the effect of climate change on wetlands dynamics, carbon and hydrological cycles, weather and biodiversity. This study presents a remote sensing technique for determining daily surface water fractions based on multiple satellite remote sensing data sets. The focus is on the Alaska-Yukon region and daily inundation dynamics for the period from 2002 until 2008. Our inundation detection approach employs passive microwave data from AMSR-E on NASA’s Earth Observing System (EOS) Aqua satellite and Leaf Area Index (LAI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the EOS Terra satellite. Radar backscatter from SeaWinds-on-QuikSCAT (QSCAT) is used to maximize the sensitivity to the presence of vegetation biomass in inundated areas. A comparison with high-resolution maps of open water and wetlands vegetation, derived from JERS SAR, and open water area, derived from LANDSAT, suggests that this mapping approach shows great potential for accurate mapping of inundation dynamics across this region. Variations in open water area as seen by LANDSAT and SAR imagery are detected, as well as the sensitivity to variations in inundated vegetation. We note reasonable agreement between surface inundation fraction, river discharge, and simulated river runoff simulated by a hydrological model, with pronounced interannual variations that could be explained by year-to-year changes in large-scale atmospheric circulation over Alaska. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA).