Thermal characterization of the active layer at the Limnopolar Lake CALM-S site on Byers Peninsula (Livingston Island), Antarctica

Abstract

Abstract. The Limnopolar Lake site (A25), of the Circumpolar Active Layer Monitoring -South network (CALM-S), is located on Byers Peninsula, where the active layer thickness is monitored systematically (by mechanical probing during the thawing season and by temperature devices continuously since 2009). Air, surface, snow and ground temperature devices have been installed to monitor ground thermal behavior, which is presented and characterized here. We use the air and ground mean daily temperature values to define the following parameters: maximum, minimum and mean temperatures, the zero annual thermal amplitude, and the depth and position of the top of the permafrost table. The freezing and thawing seasons (defining their starting dates as well as their length) and the existence of zero curtain periods have also been established. We also derive apparent thermal diffusivity and plot thermograms to study the thermal behavior of the ground at different depths and seasons. After this complete thermal characterization of the active layer, we propose the potential existence of a permafrost table at approximately 130 cm in depth as well as a former transitional layer above it, and discuss the role of water in connection with the thermal behavior of the ground during the study period.

Effect of Snow Cover on the Active‐Layer Thermal Regime – A Case Study from James Ross Island, Antarctic Peninsula

“…The annual variability of air and ground temperatures at Mendel Station, compared to similar data from the South Shetland Islands and South Orkney Islands, suggests that considerably colder climatic conditions occur on JRI (see Table ). This is also indicated by the significantly lower FDD g values (‐2735.5 to –2748.5°C day) calculated for Mendel Station compared to those of –500 and –900 to –1200°C day reported from the South Shetland Islands and South Orkney Islands, respectively (Michel et al , ; Guglielmin et al , ; Almeida et al , ; De Pablo et al , ).…”

“…Although winters are generally much colder on JRI than in the northern AP, we detected that subsurface conditions can potentially be warmer during thawing seasons on JRI than on South Shetland or South Orkney. TDD g values calculated for JRI (496.1°C day in 2011–12 and 358.3°C day in 2012–13) are significantly higher than those for Livingston Island (98 to 257°C day; De Pablo et al ., ) and Signy Island (2 cm TDD g ranged between 260.5 and 378.0°C day for the period 2006–09; Guglielmin et al ., ). An even higher TDD g value of 618°C day has been recorded at Rothera Point, Adelaide Island (Guglielmin et al ., ).…”

“…The ground surface at the site on JRI investigated in the present study is free of vegetation, which is, by contrast, well developed on Signy Island, where a significant influence of vegetation cover on ground temperatures was found (Cannone et al ., ). We also observed greater variability in ground temperature at 5 cm depth during winters with thinner snow cover, in contrast to the South Shetland Islands where a snow depth greater than 40 cm had a significant effect on the active‐layer thermal regime (De Pablo et al ., ). The minor effect of a thin snow cover on the ground thermal regime during the freezing season at the study site is also indicated by the high freezing n ‐factor values (0.95 to 0.97).…”

“…The ground thermal regime for the period of 2011–13 was evaluated in accordance with recent studies investigating Maritime Antarctic (Guglielmin et al , ; Michel et al , ; De Pablo et al , ), using the following parameters: (1) mean annual and monthly ground temperatures; (2) the cumulative sum of mean daily ground temperatures above 0°C (the thawing‐degree days – TDD g ); (3) the cumulative sum of mean daily ground temperatures below 0°C (the freezing‐degree days – FDD g ); and (4) the ALT, interpolated as the 0°C isotherm depth and derived from contours of the daily mean ground temperature interpolated using kriging algorithms in the Surfer® software program (Golden Software, Golden, CO, USA).…”

“…The response of regional permafrost to this warming remains unknown and represents one of the most important topics in climate modelling, because numerical models suggest that permafrost may become the dominant contributor of CO 2 and CH 4 into the atmosphere in the 21 st century (Schaefer et al , ). Despite the increasing number of periglacial studies focusing on the AP in the last decade (Vieira et al , ; Guglielmin et al , ; Bockheim et al , ; De Pablo et al , ; Almeida et al , ; Goyanes et al , ), thermal conditions in the active layer and its interaction with meteorological factors are not well known. In particular, the influence of snow on active‐layer thickness (ALT) and the thermal regime is relatively poorly understood, despite being a major modulating factor to the atmosphere (Boike et al , ; Vieira et al , ).…”