Remote sensing measurements of thermokarst subsidence using InSAR

Abstract Thawing of ice‐rich permafrost followed by surface subsidence results in irregular, depressed landforms known as thermokarst. Many remote sensing studies have identified thermokarst landforms and mapped their changes. However, the intrinsic dynamic thermokarst process of surface subsidence remains a challenge to quantify and is seldom examined using remote sensing methods. In this study we used spaceborne interferometric synthetic aperture radar (InSAR) data to map surface subsidence trends at a thermokarst landform located near Deadhorse on the North Slope of Alaska. A pipeline access road constructed in the 1970s triggered the thawing of the permafrost, causing subsequent expansion of the thermokarst landform. Using Phased Array type L band Synthetic Aperture Radar images acquired by the Advanced Land Observing Satellite‐1, our InSAR analysis reveals localized thermokarst subsidence of 2–8 cm/yr between 2006 and 2010, equivalent to an ice volume loss of about 1.2 × 10 7 m 3 /yr. Comparisons between InSAR subsidence trends and lidar microtopography suggest a characteristic time of 8 years of thermokarst development. We also quantitatively explain the difficulty, uncertainties, and possible biases in separating thermokarst‐induced, irreversible subsidence from cyclic seasonal deformation. Our study illustrates that InSAR is an effective tool for mapping and studying active thermokarst processes and quantifying ice loss.