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

• Autor(a) principal: Ramos, M.
• Data de Publicação: 2017
• Outros Autores: Vieira, Goncalo, de Pablo, M.A., Molina, A., Abramov, A., Goyanes, G.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10451/36181
• topic: Permafrost; Decreasing thaw depth; Active layer; Snow insulation; Antarctic peninsula

The Western Antarctic Peninsula region is one of the hot spots of climate change and one of the most ecologicallysensitive regions of Antarctica,where permafrostis near its climatic limits. The research was conducted in Decep-tion Island, an active stratovolcano in the South Shetlands archipelago off the northern tip of the Antarctic Pen-insula. 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 ice-rich permafrost at−0.8 °C at the depth of zero annual amplitude, with an active layer of about 30 cm. Resultsfrom thaw depth, ground temperature and snow cover monitoring at the Crater Lake CALM-S site over the period2006 to 2014 are analyzed. Thaw depth (TD) was measured by mechanical probing once per year in the end ofJanuary or early February in a 100 × 100 m with a 10 m spacing grid. The results show a trend for decreasingthaw depth from ci. 36 cm in 2006 to 23 cm in 2014, while MAAT, as well as ground temperatures at the baseof the active layer, remained stable. However, the duration of the snow cover at the CALM-S site, measuredthrough the Snow Pack Factor (SF) showed an increase from 2006 to 2014, especially with longer lasting snowcover in the spring and early summer. The negative correlation between SF and the thaw depth supports the sig-nificance of the influence of the increasing snow cover inthaw depth,evenwith notrendin the MAAT.The lack ofobserved ground cooling in the base of the active layer is probably linked to the high ice/water content at thetransient layer. The pyroclastic soils of Deception Island, with high porosity, are key to the shallow active layerdepths, when compared to other sites in the Western Antarctic Peninsula (WAP). Thesefindings support thelack of linearity between atmospheric warming and permafrost warming and induce an extra complexity tothe understanding of the effects of climate change in the ice-free areas of the WAP, especially in scenarios withincreased precipitation as snow fall.