Changeability of maximal thickness of active permafrost layer in the Bellsund region (W Spitsbergen) in the period 1986-2009

Abstract

W pracy przebadano wpływ temperatury powietrza, cyrkulacji atmosferycznej i temperatury powierzchni morza na Prądzie Zachodniospitsbergeńskim na zmiany maksymalnej miąższości czynnej warstwy zmarzliny na Calypsostrandzie (Bellsund) w latach 1986-2009. Stwierdzono, że podstawowym czynnikiem klimatycznym, regulującym tą zmienność jest temperatura powietrza w Svalbard-Lufthavn, co pozwala na rekonstrukcję przebiegu zmian miąższości czynnej warstwy zmarzliny na Calypsostrandzie w okresie 1911-2009. W badanym okresie nie zachodzą istotne związki między miąższości czynnej warstwy zmarzliny a zmiennością wskaźników cyrkulacji hemisferycznej (AO) i regionalnej (NAO). Bardzo silny wpływ na miąższość czynnej warstwy zmarzliny na Calypsostrandzie wywierają zmiany temperatury powierzchni Morza Grenlandzkiego w rejonie przepływu ciepłego Prądu Zachodniosptsbergeńskiego.The measurements of thickness of the sling part of permafrost thawing in summer i.e. permafrost active layer were made on Spitsbergen in the Bellsund region in 1986-2009 within the polar expedition programs accomplished by Maria Curie Skłodowska University, Lublin. The investigations included the seaside plain Calypsostranda situated on the western side of Recherche Fiord in the forefield of the glaciers Scott and Renard (Fig. 1) constituting a complex of raised marine terraces formed during the glacioisostatic movements. Maximal thickness of active permafrost (CWCmax) was determined using the sounding method in 10 chosen points localized within the geocomplexes typical of tundra (Fig. 2). The average many years' maximal values of active layer thickness are presented in Table 1. The paper presents the results of studies on the effect of air temperature, atmospheric circulation and sea surface temperature on Western Spitsbergen Current on the variation of maximal thickness of active permafrost layer. As follows from the studies the interyear changes of maximal thickness of the active layer on Calypsostranda are relatively susceptible to the changes of air temperature which indicates prompt susceptibility to changes. The tendency towards the increase of ground thawing depth on Calypsostranda in 23 years under consideration is not stable and can change significantly depending on temperature. Though there is no doubt that during the last 4-5 years there have appeared signs of quickened increase of active layer thickness on Calypsostranda (Fig. 4), the conclusion about permanent degradation of permafrost seems to be risky at present. Of the climatic factors the essential one affecting the interannual changeability of maximal thickness of the active layer on Calypsostranda is air temperature in Svalbard-Lufthaven. The regression analysis showed (Equation 1) that the variance CWmax is explained best by the merged May and June temperatures (SVsumT_V-VI) and the average March temperature (SVT_III) (Fig. 5). Changeability of these both variables accounts for 83% variance CWCmax. Equation [1] allows to reconstruct the course of changes of maximal thickness of the active layer on Calypsostranda in 1911-2009 (Fig. 6). In the studied period distinct and essential connections between CWCmax on Calypsostranda and changeability of hemispheric circulation indices (AO) or regional (NAO) were not found. However, temperature changes of Greenlandic Sea surface in the region of warm Western Spitsbergen Current flow (Table 3) affect significantly on air temperature on Spitsbergen and as a result on active layer thickness on Calypsostranda. As the hitherto course of maritime processes indicates a gradual decrease in heat resources carried by Western Spitsbergen Current, one can deduce that air temperature in the region of Spitsbergen will drop in near future. That will probably lead to a decrease in thawing depth on Calypsostranda. Differentiation in active layer thickness is dependent on local factors such as configuration, aspect of slopes, vegetation cover as well as kind and extent of water mobility in covers as it was reported earlier