Hurd Peninsula glaciers, Livingston Island, Antarctica, as indicators of regional warming:: ice-volume changes during the period 1956-2000

Johnsons and Hurd Glaciers are the two main glacier units of Hurd Peninsula ice cap, Livingston Island, South Shetland Islands, Antarctica. They presently cover an area of about 10kM2. Johnsons is a tidewater glacier, while Hurd Glacier ends on emerged land. In this paper, we estimate the changes in ice volume during the period 1956-2000, and compare them with the regional meteorological records. The volume-change estimates are based on the comparison of digital terrain models for the glacier surface, constructed from aerial photographs taken by the British Antarctic Survey in 1956 and from our geodetic measurements in 1999/2000. The total volume estimates are based on an ice-thickness map constructed from radio-echo sounding profiles (18-25MHz) done in 1999-2001, showing maximum ice thickness of about 200m. We estimate the changes in ice volume during the period 1956-2000 to be -0.108 +/- 0.048 km(3), which represents a 10.0 +/- 4.5% decrease from the 1956 total volume of 1.076 +/- 0.055 km(3) and is equivalent to an average annual mass balance of -0.23 +/- 0.10 m w.e. during 1956-2000. Ice-thickness changes range from -40 to +20 m, averaging -5.5 +/- 4.4 m. Most areas show ice thinning; the thickening is limited to a small area within Johnsons Glacier. All glacier fronts, except Johnsons' calving front, show retreat. These changes are consistent with the regional meteorological records for mean summer temperature, which show a trend of +0.023 +/- 0.005 degrees C a(-1) during the period 1956-2000.