Integrating ICESat-2 and Sentinel-1 measurements to quantify thaw subsidence in Alaska

Abstract:

As temperatures in the Arctic warm, permafrost across Alaska is thawing at an increased rate. Permafrost acts as a carbon reservoir and its degradation from thawing releases carbon dioxide and/or methane into the atmosphere which in turn leads to warmer global temperatures. Thawing of permafrost and thickening of the active layer may also lead to large-scale subsidence features that can affect land stability and infrastructure. Thus, understanding and mapping surface deformations related to these thawing processes is a critical component for integrating these processes into climate models and hazard assessments. Whereas estimates of subsidence from Global Navigation Satellite System (GNSS) stations and borehole extensometers provide precise point-wise estimates, they lack the spatial data coverage to adequately capture regional permafrost thaw patterns. Alternatively, interferometric synthetic aperture radar (InSAR) has been used to measure large-scale deformation due to active layer and permafrost changes across large regions. However, InSAR data is often limited by decorrelation due to changing surface conditions (e.g. vegetation and seasonal snowfall), spatial variations in atmospheric delay, and a need for a known or stable calibration point. In this study, we compare displacement measurements from the European Space Agency’s Sentinel-1 interferometric products, NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) crossovers, and in-situ data where applicable to assess ICESat-2’s ability to detect thaw subsidence and act as an additional calibration constraint on InSAR-derived displacement observations. We perform this analysis on test sites both on the North Slope, Alaska, and near the Alaska Mountain Range. In areas where both Sentinel-1 and ICESat-2 indicate subsidence, we investigate ICESat-2 along-track profiles to look at changes in elevation profiles.