Detection of Decadal Change in Alaskan Wetlands Using ALOS/PALSAR and JERS SAR Data
Mahta Moghaddam(1), Jane Whitcomb(1), Kyle McDonald(2) and Erika Podest(3)
(1) The University of Michigan, 1301 Beal Avenue, Ann Arbor, MI 48109, United States
(2) Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
(3) Jet Propulsion Laboratory, 4800 Oak Grove Drive, pasadena, CA 91109, United States
While northern wetlands are believed to have hitherto served as important carbon sinks, sequestering about one third of the total global pool of soil carbon, the warmer, drier conditions expected throughout the Arctic as a consequence of global warming may induce aerobic decomposition of northern wetland soils. The northern wetlands will, in that event, become major sources rather than sinks of carbon dioxide. It is, therefore, critical to develop an ability to monitor long-term changes occurring in the condition of northern wetlands. Since L-Band SAR is sensitive to vegetation structure, biomass, and moisture content, it is an excellent choice for detecting changes in the characteristics of vegetated wetlands. We have, therefore, used multi-temporal L-band SAR imagery from two different spaceborne L-band synthetic aperture radar (SAR) sensors, JERS and ALOS/PALSAR, to produce a thematic map of change in the type and extent in representative regions of wetlands in Alaska, such as tundra, scrub/shrub, and forested wetlands. The JERS imagery is used to represent the wetlands status for the 1997 time frame, while dual-polarized ALOS/PALSAR imagery captures the wetlands status for the 2007 time frame. The SAR imagery is supplemented with associated imagery collection dates, as well as a digital elevation model (DEM), a slope model, an open water mask, proximity to water, and geographic latitude. The change detection classification is based upon a decision tree algorithm. The accuracy of the resulting thematic change map will be verified using ground reference data. The results will demonstrate the capability of multi-platform satellite SAR observations for characterizing the transitions across multiple years in extent and type of vegetated wetlands as a result of global climate change.