Long term active layer monitoring at a warm-based glacier front from maritime Antarctica

Abstract

Knowledge on active-layer dynamics and permafrost distribution is of especial importance in Maritime Antarctica, where dramatic climate warming occurred in the last decades. Few long-term studies of active-layer temperatures in this region, and no one focus on recently deglaciated areas under paraglacial conditions. This paper analyses the long-term soil thermal regime of a warm-based glacial front site located at Low Head, King George Island. The monitoring system consists of soil temperature probes connected to a datalogger that recorded data at hourly intervals. We calculated the thawing days (TD), freezing days (FD), number of isothermal days (ID), number of freeze-thaw days (FTD), thawing degree days (TDD), freezing degree days (FDD), and the apparent thermal diffusivity (ATD). The results indicate that active layer thermal regime at Low Head is similar to other periglacial environments from Maritime Antarctica, with differences associated with the influence from the nearby warm-based glacier. Surface temperatures show greater variations during the summer resulting in frequent freeze and thaw cycles, mainly (1 cm and 10 cm). The temperature profile during the studied period indicates that the active layer thickness reached a maximum of 106 cm on February 7th 2015. Soil temperature buffering was limited by the low snow cover, low soil moisture, and absence of vegetation. Based on the high interannual variability detected during the five years monitoring run, we stress that longer monitoring periods are necessary for a more detailed knowledge on how permafrost respond to climate changes in this rapidly warming zone.