Understanding the evolution of permafrost extent and active layer thickness (ALT) in the Antarctic continent is critical to global climate change and ecosystem transformations in the polar regions. However, due to the remoteness and harsh environment of the Antarctica, most studies lack long-term and a regional perspective on the variations of ALT in Antarctica, resulting in hindering accurate assessment of ALT dynamics. In this study, based on MODIS land surface temperature (LST) and soil climate station data, we used the Stefan model to reconstruct ALT in the ice-free area of the McMurdo Dry Valley (MDV) in the East Antarctic from 2003 to 2022. The modelled ALT was verified against ground observations showing a good correlation of 0.69, with RMSE of 14.19 cm. The results indicate that the ALT exhibits a decreasing trend from coastal to inland, ranging from a maximum of 80 cm near the coastal area to zero in the polar plateau. Furthermore, within the inland valleys, deeper ALT values are mainly distributed in the lower elevation areas, reaching up to 60 cm at the lowest altitudes. During the period from 2003 to 2022, there was no significant trends of increase or decrease in the ALT of the entire MDV. But the interannual variability in the ALT along coastal regions and inland valleys was typically more pronounced than that within the polar plateau, with a maximum amplitude of 30 cm. Our study proved that the Stefan model with parameters estimated by MODIS LST and soil climate station data, has good potential to reconstruct ALT in the entire Antarctica under climate warming.

McMurdo Dry Valleys, Antarctica, permafrost, active layer thickness, climate change