Change in position and altitude of a small outlet glacier during the period 1943–92: Leverett Glacier, West Greenland

Abstract

Fluctuations in the position and surface altitude of Leverett Glacier, a small outlet glacier at the western margin of the Greenland ice sheet, are determined from a photogrammetric analysis. During the Greenland Ice-Margin Experiment (GIMEX) 1992 expedition, six control points were measured on the exposed rock surrounding Leverett Glacier, using a distancemeter (AGA 220 Geodimeter) and theodolite (Wild T2). Photogrammetric measurements were carried out on an analytical plotter (Zeiss Planicomp C100). The altitude of points could be photogrammetrically measured with a maximum error of 0.86 m. The data on the altitude changes of Leverett Glacier presented here are the first in West Greenland that span a time period of nearly 50 years. During the period 1943–68 the rate of altitude change was –0.6 m w.e.a−1. The thickening rate during the period 1968–85 was + 1.2 m w.e.a−1. Thickening continued dining the period 1985–92 at a rate of + 0.4 m w.e.a−1. This recent thickening is significant when compared to year-to-year variation in ablation. Trends in air temperature from the nearby climate station at Kangerlussuaq are consistent with the possibility that observed changes in the altitude of the glacier surface are the result of local changes in meteorological conditions determining ablation rates.