Pan-Antarctic map of near-surface permafrost temperatures at 1 km2 scale

Permafrost is present within almost all of the Antarctic's ice-free areas, but little is known about spatial variations in permafrost temperatures except for a few areas with established ground temperature measurements. We modelled a temperature at the top of the permafrost (TTOP) for all the ice-free areas of the Antarctic mainland and Antarctic islands at 1 km(2) resolution during 2000-2017. The model was driven by remotely sensed land surface temperatures and downscaled ERA-Interim climate reanalysis data, and subgrid permafrost variability was simulated by variable snow cover. The results were validated against in situ-measured ground temperatures from 40 permafrost boreholes, and the resulting root-mean-square error was 1.9 degrees C. The lowest near-surface permafrost temperature of -36 degrees C was modelled at Mount Markham in the Queen Elizabeth Range in the Transantarctic Mountains. This is the lowest permafrost temperature on Earth, according to global-scale modelling results. The temperatures were most commonly modelled between -23 and -18 degrees C for mountainous areas rising above the Antarctic Ice Sheet and between -14 and -8 degrees C for coastal areas. The model performance was good where snow conditions were modelled realistically, but errors of up to 4 degrees C occurred at sites with strong wind-driven redistribution of snow.