Ice cliff retreat and sea-ice formation observed around King Sejong Station in King George Island, west Antarctica

Abstract

Ice cliff retreat and sea-ice formation around King Sejong Station in King George Island were analysed and compared with air temperature change. Analysis of 33-year (1969-2001) air temperature records at Bellingshausen Station has revealed regional atmospheric warming, and the increasing rate of air temperature is equivalent to a warming of 1°C for 27-year period. Here we present time-series of observations for the areal extent of the ice cliff and ice sheet, showing that they have retreated dramatically in the past 45 years (1956-2001). Retreat of 1,050 m in length of the ice cliff has changed the Marian Cove into a low rectangular form of 4 km in length and 1 to 1.3 km in width. The retreat rates have since increased from 6 m/yr of the primary investigated period to 54 and 81 m/yr in the recent years. Exceptionally, the ice cliff had been advanced of 21 m in length for a year between 1987 and 1988 of cold winters. Ice sheet in King George Island also shows a similar decrease, and the decreasing extent is much larger at the southern part of the Marian Cove, relatively more exposed to the sun, than at the northern part. Comparing sea-ice formation in winter with air temperature data shows a pattern starting to freeze below -5°C and to thaw over -3°C. It is conclusively estimated that the patterns and magnitudes of ice cliff retreat and sea-ice formation are consistent with fluctuations of the air temperature, and that the recent rapid retreat of ice cliff and less formation of sea-ice are caused especially by the warming trends in autumn accompanied with expansion of summer thawing period.