Spatial and temporal variability of ground surface temperature and active layer thickness at the margin of maritime Antarctica, Signy Island

• Published in: Geomorphology
• Main Authors: GUGLIELMIN, MAURO, CANNONE, NICOLETTA, Worland M.R.
• Other Authors: Guglielmin, Mauro, Worland, M. R., Cannone, Nicoletta
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2012
• Subjects: Ground surface temperature; Active layer; Vegetation cover; Arctic; Antarctic; Signy Island; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/11383/1782917; https://doi.org/10.1016/j.geomorph.2011.12.016

A CALM grid with a data logger system to monitor the active layer thermal regime was established on Signy Island (60 degrees 43'S, 45 degrees 38'W at 80 m a.s.l.) in December 2005. The active layer at each of the 36 nodes of the grid was monitored measuring the ground temperature at least at 4 different depths between 0.02 and 0.4 m at the end of the summer season. In addition, within the grid, we selected four sites closely spaced (in a ray of 25 m) three of which with the same topographical characteristics (north facing aspect) but different vegetation coverage (one bare ground, BG1 and two sites with different vegetation: Andreaea sp. and Sanionia uncinata) and the fourth (BG2) it is as BG1 a bare ground but with south facing aspect. In particular, 4 thermistors were located at depths of 0.02, 0.3, 0.6, and 0.9 m at BG2 and at the Andreaea sp site, 9 thermistors at 0.02, 0.3, 0.6, 1, 1.2, 1.4, 1.6, 2, and 2.5 m at BG1 and at 0.02 and 0.6 m of depth at Sanionia site. Generally, with the same aspect, a thick vegetation cover (as in Sanionia site) provides a greater insulative effect than a thinner vegetation cover (as in Andreaea site) or bare ground (BG1) because vegetation both shades and insulates the ground resulting in a reduction in summer heat flux. Ground Surface Temperature (GST) was colder and more buffered in spring and summer under the vegetated ground than in BG1, although the coldest GST and lowest Thawing Degree Days (TDD) were recorded at BG2 and related to its southern aspect. Our data confirm that air temperature is the main driver of GST, as already reported both in the Arctic and Antarctic. We also found that the effect of air temperature changes seasonally, being drastically reduced in winter and, to a lesser extent, in fall and spring, when there is generally thin snow cover (<30 cm). During the summer, when snow cover is usually absent, the air temperature is the dominant driver, although incoming radiation also had an effect on the northern exposed bare ground and to a lesser extent ...