The frost environment of Western Dronning Maud Land, sub-Antarctic Marion Island and the High Drakensberg of South Africa: A preliminary evaluation
Hansen CD1, Meiklejohn Kl1 and Nel, W2
1 Department of Geography, Rhodes University, Grahamstown, South Africa
2 Department of Geography and Environmental Science, East London, South Africa.
Permafrost and active-layer conditions are being monitored in the vicinity of the South African research station of SANAE IV, Antarctica at eight sites. Ground thermal environments have been measured at Flarjuven Bluff 1, Vesleskarvet (SANAE Base), and Troll Station 1, for eight, seven and nine years respectively. During the Austral summer of 2012, seven new shallow boreholes were drilled at five new sites {Grunehogna Peaks, Robertskollen, Slettfjell, Schumacherfjellet, and Valterkulten), as well as two new shallow boreholes at two existing sites {Flarjuven Bluff 2 and Troll Station 2). At these sites sensors log thermal data at hourly intervals at various depths in the ground (near surface, 15 cm, 30 cm, 45 cm, 60 cm), as well as ambient air temperature. For Marion Island two temporary logging stations were set up during 2014 at Katedraalkrans and Tafelberg and logged until April 2016. Similarly, logging sites were erected for Ben MacDhui and the Elandsberg in the Eastern Cape of South Africa in 2014 and loggers retrieved in 2015.
This paper presents an overview of the thermal regime from the Antarctic boreholes, and the temporary logger stations of Marion Island and the Eastern Cape. A focus is made on annual and seasonal cycles, although diurnal environments are also discussed. For the Antarctic sites no thaw events are present during the Austral winter. In comparison, at the lower sites (Elandsberg) in the Eastern Cape of South Africa no freezing events are recorded at 5cm in the ground. Vegetation is seen as a limiting factor and frost-related landforms are only present for South Africa where frost processes exceed the threshold to disturb vegetation cover. Similarly, snow cover has a dampening effect on ground thermal regimes, decreasing the number and intensity of frost cycles observed.
While an increase in altitude translates into a higher frequency of frost cycles, the underlying geology and sediment/soil textural distribution becomes another limiting factor. In particular, this is observed for the thermal regime of Troll Station (Antarctica), where the sediment textural distribution yields low moisture holding capacity. The results presented provide insight on the frost environment of a number of settings at different altitudes and latitudes.
