A mean net accumulation pattern derived from radioactive layers and radar soundings on Austfonna, Nordaustlandet, Svalbard

Abstract

We present the snow-accumulation distribution over Austfonna, Nordaustlandet, Svalbard, based on 29 shallow ice cores that were retrieved from this ice cap during 1998 and 1999. Mean annual net accumulation is deduced from radioactive layers resulting from the 1954–74 atmospheric nuclear tests (maximum in 1963) and the Chernobyl accident (1986). The Chernobyl layer was located in 19 ice cores in the accumulation area, and the nuclear test layer was located in two deeper ice cores. In addition, the spatial variation of the depth of winter 1998/99 snowpack was mapped using snow probing, ground-penetrating radar methods and pit studies. The altitudinal gradient of the mean annual net mass balance and the altitude of the mean equilibrium line are determined along five transects ending at the top of the ice cap. The mean annual net mass balance and the equilibrium-line altitudes show a high degree of asymmetry between the western and eastern parts of Austfonna, in accordance with the distribution of winter accumulation. Large interannual variations of the accumulation exist. However, the study of the mean annual net mass balance shows no trend for two different time periods, 1963–86 and 1986 to the date of the drillings (1998/99).

Geometric changes and mass balance of the Austfonna ice cap, Svalbard

“…1a) collecting data on Austfonna since 2004 show that the mean daily winter temperatures range from about −30 • C to 0 • C. The meteorological conditions during the summer season are less variable; daily temperatures usually range from 0 • C to 5 • C during the 1-2 months long ablation period. Most of the winter precipitation over the ice cap is originating from the Barents Sea in the southeast, resulting in a pronounced accumulation gradient with most snow in the southeast and least snow in the northwest (Schytt, 1964;Pinglot et al, 2001;Taurisano et al, 2007). This pattern is also recognized in the equilibrium line altitude (ELA) which is significantly lower in southeast than in northwest (Pinglot et al, 2001;Schuler et al, 2007).…”

“…This pattern is also recognized in the equilibrium line altitude (ELA) which is significantly lower in southeast than in northwest (Pinglot et al, 2001;Schuler et al, 2007). Pinglot et al (2001) estimated an average net mass balance of 0.5 m w.e. y −1 in the summit area for the period 1986-1998/99 by detecting the depth of the radioactive 1986 Chernobyl layer in 19 shallow ice cores (Fig.…”

“…Most of the winter precipitation over the ice cap is originating from the Barents Sea in the southeast, resulting in a pronounced accumulation gradient with most snow in the southeast and least snow in the northwest (Schytt, 1964;Pinglot et al, 2001;Taurisano et al, 2007). This pattern is also recognized in the equilibrium line altitude (ELA) which is significantly lower in southeast than in northwest (Pinglot et al, 2001;Schuler et al, 2007). Pinglot et al (2001) estimated an average net mass balance of 0.5 m w.e.…”

“…Moholdt et al: Geometric changes and mass balance of the Austfonna ice cap Drewry, 1989;Pinglot et al, 2001), but no continuous records of mass balance exist until 2004 when an annual mass balance program was initiated. Photogrammetric records are also sparse over Austfonna due to the large extent and featureless topography which make image analysis extremely difficult.…”

Observations: Cryosphere

“…The authors discovered the central and highestaltitude area of the icecap, 15 percent of its total area, "increased in elevation by an average of 50 cm per year between 1996 and 2002," while "to the northeast of this region, thickening of about 10 cm per year was also observed." The highest of these growth rates represents as much as a 40 percent increase in accumulation rate (Pinglot et al, 2001).…”