Effects of the Last Glacial Maximum in the northern Prince Charles Mountains
Recent mapping of lateral moraines located alongside the major glaciers in the northern Prince Charles Mountains has been aimed at identifying those associated with the Last Glacial Maximum (LGM), ~20,000 years ago. The altitude of these moraines, relative to present glacier surfaces, provides an indication of how large the glaciers were at that time. Contrary to previously held beliefs that substantial glacier expansion, up to hundreds of metres, occurred during the Last Glacial Maximum, these lateral moraines are located only tens of metres above the present glacier surfaces, indicating that there were, in fact, only modest increases in ice volume. This work, which includes an on-going cosmogenic isotope exposure age dating study of boulders from the lateral moraines, has important ramifications for understanding the way in which the Antarctic Ice Sheet and outlet glaciers respond to climate change.
When looking towards the east across a vast ice-covered moraine field on the northern side of Crohn Massif, Porthos Range, northern Prince Charles Mountains a type of lateral moraine feature, deposited by the Scylla Glacier is visible. It consists of a thin (<1m) layer of boulders deposited over very slow moving or stagnant ice. The arcuate ridges next to the snowbank at the left are from a small rock glacier that is flowing into the moraine field from the slopes of Crohn Massif.
On the eastern Loewe Massif, northern Prince Charles Mountains a moraine ridge has been deposited by the Nemesis/Charybdis Glaciers during the Last Glacial Maximum. Ice flowed from right to left. The area is about 3 km from and 150m above the present glacier. Highly apparent is the contrast between the dark brown, very bouldery surface of the Last Glacial Maximum moraine area, and the subdued, red-brown boulder-free surface to the upper left. This suggests a considerable age difference between the two land surfaces.
The Battye Glacier ice tongue floats on the lake surface which is located 7m above sea level. The ice on the lake is ~2 m thick, and is semi-permanent. Areas around the edge and near the ice tongue melt each summer, and occasionally the whole surface becomes ice free. Radok Lake is the deepest lake in Antarctica. A sounding by Jon Luly and Mark Mabin in 1996 near the tip of the ice tongue reached 335m depth. Previously, Russian scientists had reported a depth of 346m but it is not known where this was taken. The floating part of the Battye Glacier ice tongue is about 2 km long and flows at about 80 m per year. Since January 1990 several hundred metres of the tip have broken off and floated away to the north.
Slopes at the northern end of the Radok Lake basin are cut in the sandstones of the Amery Group rocks and rise about 150m above the lake. A horizontal line running across the slope about two-thirds of the way up is believed to be a lake shoreline formed when Radok Lake was considerably deeper than at present, but it is not known when this occurred.
Mabin, M.C.G. (1992) Late Quaternary ice surface fluctuations of the Lambert Glacier. In: Yoshida, Y., Kaminuma, K. and Shiraishi, K. (editors) Recent Progress in Antarctic Earth Science, p. 683-687. Terra Scientific Publishing Company, Tokyo.
Mabin, M.C.G. (personal communication, 1997)