Recent shallowing of the thaw depth at Crater Lake, Deception Island, Antarctica (2006–2014)

Abstract

The Western Antarctic Peninsula region is one of the hot spots of climate change and one of the most ecologically sensitive regions of Antarctica, where permafrost is near its climatic limits. The research was conducted in Deception Island, an active stratovolcano in the South Shetlands archipelago off the northern tip of the Antarctic Peninsula. The climate is polar oceanic, with high precipitation and mean annual air temperatures (MAAT) close to − 3°C. The soils are composed by ashes and pyroclasts with high porosity and high water content, with icerich permafrost at −0.8°C at the depth of zero annual amplitude, with an active layer of about 30 cm. Results from thaw depth, ground temperature and snow cover monitoring at the Crater Lake CALM-S site over the period 2006 to 2014 are analyzed. Thaw depth (TD) was measured by mechanical probing once per year in the end of January or early February in a 100 × 100 m with a 10 m spacing grid. The results show a trend for decreasing thaw depth from ci. 36 cm in 2006 to 23 cm in 2014, while MAAT, as well as ground temperatures at the base of the active layer, remained stable. However, the duration of the snow cover at the CALM-S site, measured through the Snow Pack Factor (SF) showed an increase from 2006 to 2014, especially with longer lasting snow cover in the spring and early summer. The negative correlation between SF and the thaw depth supports the significance of the influence of the increasing snow cover in thaw depth, even with no trend in the MAAT. The lack of observed ground cooling in the base of the active layer is probably linked to the high ice/water content at the transient layer. The pyroclastic soils of Deception Island, with high porosity, are key to the shallow active layer depths, when compared to other sites in the Western Antarctic Peninsula (WAP). These findings support the lack of linearity between atmospheric warming and permafrost warming and induce an extra complexity to the understanding of the effects of climate change in the ice-free areas of the WAP, especially in scenarios with increased precipitation as snow fall.

Pan-Antarctic map of near-surface permafrost temperatures at 1 km2 scale

“…Recent shallowing of thaw depth and ground cooling were observed on Deception Island by Ramos et al (2017). However, similar cooling was recorded also on the eastern Antarctic Peninsula, but MAGT was overestimated by 1.4 • C at Marambio Island and by 0.8 • C at Abernethy Flats and by 0.6 • C at the Johann Gregor Mendel borehole sites.…”

“…The absence of vegetation in the Antarctic results in high snow redistribution by wind and highly spatially variable snow cover, which influences ground temperatures in many parts of the Antarctic Ramos et al, 2017;Ferreira et al, 2017). Neither snow redistribution nor sublimation are simulated by our snowfall model, and the average snow depths could not be estimated, so n f factors could not be derived for the Antarctic in the same manner as was done for the Northern Hemisphere by Obu et al (2019a).…”

“…Ferreira et al (2017) modelled freezing indices and the temperature at the top of the permafrost (TTOP) for eight monitored sites on the Hurd Peninsula and Livingston Island for the 2007 and 2009 seasons to study the controlling factors of ground temperatures. Rocha et al (2010) ran the H-TESSEL scheme forced by ERA-Interim reanalysis to simulate ground temperatures at Reina Sofía Peak on Livingston Island. Ground temperature measurements and permafrost modelling efforts have been limited to point sites, and little is known about spatial variability in ground temperatures at the regional and continent-wide scales.…”

Pan-Antarctic map of near-surface permafrost temperatures at 1 km2 scale

“…Recent shallowing of thaw depth and ground cooling were observed on Deception Island by Ramos et al (2017). However, similar cooling was recorded also in the Eastern Antarctic Peninsula, but MAGT was over-estimated by 1.4 °C at Marambio Island and by 0.8 °C at Abernethy Flats and 0.6 °C at the Johann Gregor Mendel borehole sites.…”

“…As the LST data are primarily derived from satellite data, their availability and accuracy depend on cloud cover. The absence of vegetation in the Antarctic results in high snow redistribution by wind and highly spatially variable snow cover, which influences ground temperatures in many parts of Antarctic (Guglielmin et al, 2014;Ramos et al, 2017;Ferreira et al 2017). Neither snow redistribution nor sublimation are simulated by our snowfall model and the average snow depths could not be estimated and nf-factors derived as for the Northern Hemisphere by Obu et al (2019).…”