A season of notable successes despite obstacles

The 36-day besetment of Polar Bird had minimal effect on Australia’s 2001–02 Antarctic field season, involving successful projects in oceanography, glaciology, marine biology, penguin studies and atmospheric science.

An early highlight was the successful completion of a complex marine science voyage involving 70 scientists from 11 nations. Aurora Australis travelled due south from Hobart to the ice edge to monitor changes in oceanic circulation patterns and the consequences of these changes on marine life. Upper ocean temperature data gathered by the French resupply vessel l'Astrolabe in recent years combined with 5-yearly repeats of Aurora’s transect and some satellite observations to effectively monitor the Antarctic Circumpolar Current. This work has produced evidence of a slowing of the so-called ‘overturning circulation’ — the movement of water that brings nutrient-rich deep ocean water into surface layers, where phytoplankton converts it into the raw material to fuel the marine food web.

Research into the effects of substances leaching from Casey’s Thala Valley tip site was hindered by poor diving conditions early in the season, but very hard work during a few brief windows of good weather brought satisfactory progress. The project produced valuable information on environmental variation in the under-ice marine areas offshore from Thala Valley.

A comparison of reproductive success of Adélie penguins on Shirley Island, a site regularly visited by humans, and the no-go Witney Point area found that human visitation was not the cause of the lower reproductive rates on the island.

Geoscience work in the Beaver-Radok Lake areas extracted a core of glacial and lake floor sediments. The 5m core from Lake Terrasovoje represents the fullest record since deglaciation, and should show how climate has varied over that time. The GPS units in the Prince Charles Mountains have been visited and serviced, and a Chinese team has successfully deployed an Australian automatic weather station, producing data for both countries.

The LIDAR equipment installed at Davis last year has been used for extensive observations of stratospheric temperatures and other properties of the climate of this region high above the earth. The VHF radar array at Davis can be installed next season after a good start was made on footings. When fully functional the array will allow observations of atmospheric winds up to 90km high, concentrating on winds above 10km. Data on these phenomena have not been available before to climate modellers.

Out on the Amery Ice Shelf a team of glaciologists successfully drilled — and instrumented — a 30cm diameter hole 479m to the open water underneath. The work is designed to provide an understanding of how the ice melts and water refreezes to the underside of the shelf, central processes in the transference of energy from ice to atmosphere. In a surprising discovery they encountered a thick slurry of ice chips beneath the ice, forcing some new thoughts about these complex processes. Nine submerged moorings, which held a year’s worth of hydrological data concerning the ocean’s flow across the face of the ice shelf, were successfully retrieved by Voyage 7 under very tricky ice conditions.

Mawson programs felt the effects of Polar Bird’s besetment near Samson Island. The besetment prevented a full survey of the extent of a mass mortality event of Adélies, although a number of specimens were returned to Australia for autopsies (see ‘Penguin deaths under investigation', p 39). One penguin researcher had overwintered at Mawson and was able to do much of the early season work while her colleagues were enjoying an enforced rest aboard the ship.

Professor Michael Stoddart, Chief Scientist, AAD