Glaciological research in the Antarctic Peninsula

Abstract

The Antarctic Peninsula is a good place for studies that take advantage of its wide range of latitude. Other worthwhile investigations are those that set in context the glacier/climate relationships and provide a framework of basic glaciological data. In order to speed reconnaissance mapping a series of seven 1:250 000 map sheets was published which used satellite imagery as the only source for planimetric detail. In preparation for intermediate depth ice core drilling for glaciological and palaeoclimatic investigations a wide-ranging programme of radio echo sounding has been pursued since 1963; flight tracks now total 80000 km. Experimental results are presented for an area at the base of the peninsula between latitudes 73° S and 80° S. Track plotting was controlled by relating observed subglacial topographic features with the surface expression of the same features revealed in a Landsat image mosaic. Thus navigation was not subject to the cumulative position errors generally encountered on long flights far from fixed points (nunataks). Redefinition of the earlier speculative boundary of the inland ice sheet added 38000 km2 to the land area of Antarctica while reducing the area of Ronne Ice Shelf by 11%. An unmapped nunatak was found 187 km from the nearest known outcrop. Three major inlets contained the thickest floating ice ever measured. Floating ice 1860 m thick was identified at a point only 17 km from the Ellsworth Mountains; thus within 60 km of the highest mountain in Antarctica (5140 m) there is a trench reaching 1600 m below sea level. Subglacially, there is potentially a channel well below sea level that connects the Bellingshausen Sea with the Weddell Sea. A radio echo sounder was adapted to measure the surface velocity of glaciers by reference to the spatial fading pattern of the bottom echo. Checks on Fleming Glacier with optical survey instruments showed that the true rate of movement was 44% faster than indicated by the fading pattern. It was concluded that the sounder had measured surface velocity with reference to a reflecting horizon which itself was deforming or sliding over the glacier bed. Experiments on ice shelves have been used to extend the flow law of ice to stresses lower than can be studied in the laboratory. At least down to the lowest stress considered (0.04 MN m-2) the results supported a power law with a stress exponent of 3 as found in the laboratory for higher stresses. Ultra-clean sampling techniques were developed for detecting extremely low levels of impurities in snow (3 x 10 -14 g g -1 ). Thus DDT concentrations were found to be 40-100 times smaller than earlier reported for snow from central Antarctica. An extensive reconnaissance programme of 10 m ice core drilling has been pursued with the object of studying relationships between oxygen isotope fractionation and ice and air temperatures. The ice, water, and energy balances of two representative local glaciers have been studied as a contribution to the International Hydrological Decade.