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1 Problemy Klimatologii Polarnej

1 2001

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Procesy deglacjacji na obszarze SSSI No. 8 i ich uwarunkowania klimatyczne oraz hydrologiczne (Zatoka Admiracji, Wyspa Króla Jerzego, Szetlandy Południowe)

Battke Z., Marsz A. A., Pudełko R.

Problemy Klimatologii Polarnej

2001

nr 11

121-135

This work deals with the processes of deglaciation occurring in the region of SSSI No 8 (Site of Special Scientific Interests No 8) located on the western coast of the in the vicinity of Polish H. Arctowski Station over the period 1979-1999. The location of the SSSI is shown in Fig. 1. The basis of this work is comparison between the category of the surface of the area on the charts from 1979 (Furmańczyk & Marsz, 1980) and on the chart from 1986 (Battke, 1990) and the ground measurements carried out in that area in 1999 (Battke & Pudełko, unpubl.). The categories of area were computed on maps with the help of a planimeter: - glaciated areas, - non-glaciated areas (formed by mineral grounds), - sea areas. The accuracy of total measurements of the area is not lower than about 0.2 km2. The results of cartometric measurements are given in Table 1. Over the period 1979-1999 the area of SSSI decreased by 0.86 km2 as an effect of regression of icy cliffs both of Ecology and Baranowski Glaciers and due to accompanied abrasion process. At the same time the glaciated area within the borders of SSSI decreased by 6.93 km2 and the ice free area increased by 6.08 km2. In this way the mean rate of deglaciation of the 21-year period reaches about 0.33 km2 per year. Over the 21-year period the ice free area within the borders of SSSI incresed three times (from 2.98 km2 to 9.06 km2) which results in various consequences on the physico-geographical and biological prosesses in the region of the Admiralty Bay. In the period 1978-1986 the processes of deglaciation observed north of SSSI in the region of Ecology Glacier were faster than in other regions. Over the period 1986-1999 much faster decrease in the glaciated area was noted in the south of the area, in the region of Baranowski Glacier and Tower Glacier spatial changes are presented in Fig. 2. The analysis of reasons having influence on so advance processes of deglaciation indicated to two factors i.e. climatic and hydrological that are both responsible for the process. Over the period 1978-1998 in region of the Admiralty Bay the increase in air temperature during the Antarctic summer (period December - February; trend +0.022°C/year, statistically not significant) was noted. At the same time the period in which ablation was observed (warmer November and March) was longer. The annual sums of precipitation in the same period indicate to the presence of statistically significant negative trend (-5.7 mm/year, p < 0.005). This resulted in the change in the glacier mass balance at the level 2 m. above sea level: from -115 g/cm2/year in 1979 to -146 g/cm2/year in 1998 (Fig. 3). The evaluated trend of change in mass balance is -1.56 g/cm2/year and is not statistically significant. The period during which sea ice cover is not observed also lasts longer and the ice conditions there became visibly milder. This enables the thermal abrasion to last longer and causes more active regression of ice cliffs. On the shore of the Bransfield Strait, between the Admiralty Bay and the Maxwell Bay entrance a deep cove was formed in the ice coast over the period 1985-1988. This resulted in the increase in inclination of the southern slopes of ice forming the Warszawa Ice cap and forced the volume of ice flowing towards the Bransfield Strait to increase. In this way the volume of ice flowing down the Warszawa Ice Cap eastward, to SSSI No. 8 area, decreased. The explanation of reasons responsible for the ice conditions becoming milder can be found in large scale changes in sea surface temperature of the Southern Ocean of the sea area located West of the Antarctic Peninsula (a strong positive trend SST is marked in the period from October to January; in December +0.058°C/year) and in changes in atmospheric circulation. Both these factors, i.e. the increase in the negative values of the ice masses balance and the decrease in the volume of ice flowing down on the SSSI No. 8 area act in the same direction, causing that the deglaciation process in that region occurs in an exceptionally intensive way. Due to such great intensity of the deglaciation processes occurring on the surface of SSSI in that area, this area can be regarded as a unique object of ecological and environmental research.