Active layer thermal dynamics at two lithologically different sites on James Ross Island, Eastern Antarctic Peninsula

- Active layer thermal regime at two sites on James Ross Island was studied.
- Three years of air and ground temperature measurements were analysed.
- Lithology significantly affects active layer thermal regime and thickness.
- Active layer thickness ranged from 52 to 90 cm in period 2012 to 2014.
- Effect of air temperature on ground temperature was similar at both sites.

The active layer thermal regime was studied at two sites with different lithological properties located on James Ross Island, eastern Antarctic Peninsula, to assess the main driving factors. The Abernethy Flats site (41 m a.s.l.) is located in Cretaceous calcareous sandstones and siltstones of the Santa Marta Formation. In contrast, the Berry Hill slopes site (56 m) is composed of muddy to intermediate diamictites, tuffaceous siltstones to fine-grained sandstones of the Mendel Formation. The data of air temperature at 2 m and ground temperature at two 75-cm-deep profiles were analysed for the period 1 January 2012, to 31 December 2014. Small differences were found when comparing mean air temperatures and ground temperatures at 5, 50 and 75 cm depths, in the period 2012-2014. While the mean air temperatures varied between − 7.7 °C and − 7.0 °C, the average ground temperatures oscillated between − 6.6 °C and − 6.1 °C at 5 cm; − 6.7 °C and − 6.0 °C at 50 cm; and − 6.9 °C and − 6.0 °C at 75 cm at Abernethy Flats and Berry Hill slopes, respectively. The increasing difference of ground temperature with depth, and a significant difference in active layer thickness - 52 to 64 cm at Abernethy Flats and 85 to 90 cm at Berry Hill slopes, respectively - suggests the significant effect of lithology. The higher proportion of fine particles and more thermally conductive minerals, together with higher water saturation, has been found to be fundamental for higher active layer thickness documented at Berry Hill slopes.