Traditional mapping and monitoring

Traditional mapping and monitoring techniques of permafrost are accurate but are presentlylabor-intensive and rely on interpolating small numbers of locally measured data across large areas in order to study regional-scale processes. Remote sensing addresses this difficulty by making spatially dense measurements over vast regions. Previous remote sensing studies have inferred permafrost extent from the instantaneous zero isotherm at the land surface or from changes in the dielectric marking the phase transition of liquid water to ice [8–10].We propose to use land-surface temperature (LST) measured from space-borne thermal-infrared(TIR) sensors to map patterns in the annual cycle of LST in order to ultimately detect freeze/thaw surface dynamics. Previous studies demonstrated that in autumn or spring, the LST of moist/frozen soils remains at ~0 ◦C while the phase transition between water and ice occurs. This period is a well-known phenomenon called the “zero curtain” in permafrost studies (e.g., [11]) and its presence can be used to distinguish seasonally freezing ground from freezing dry ground, in which there is no zero curtain. The premise of our approach is that if the zero curtain lasts for several days, its presence can potentially be recognized and mapped with time series of daily LST images