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Publications archive - Annual reports

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Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.

Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.

Department of the Environment and Heritage Annual Report 2002-03

Department of the Environment and Heritage, 2003
ISSN 1441 9335

Review of performance - Outcome three: Antarctica (continued)

Understanding Antarctica's Role in the Global Climate System (Departmental output 3.3)

Objective

The AAD seeks a better understanding of the role of Antarctica in the global climate system by contributing to knowledge of global climate through the study of ice, water and atmosphere, and contributing data to the world's climate research and meteorological communities.

Result

Glaciology

The mass balance (the difference between input from snowfall and ice outflow) of different sectors of East Antarctica was assessed using field and remote sensing measurements and models. These have considerably narrowed the uncertainty about the stability of the Antarctic ice sheet, in particular of East Antarctica and of the Lambert Glacier drainage basin.

Recent studies show much of the ice loss from Antarctica occurs as melt beneath the floating ice shelves. This process is very sensitive to change of ocean temperature, and the melt in turn modifies the structure and circulation of the ocean. Boreholes were drilled through the Amery Ice Shelf, the largest shelf in the Australian Antarctic Territory, to investigate interaction between ice and water in the ocean cavity below the ice shelf.

Seasonal and regional variability of sea ice thickness and distribution for the total Antarctic seasonal sea ice zone has been mapped at coarse resolution from ship-based observations. The extent and thickness of land-fast sea ice around the Australian Antarctic Territory has been determined from satellite synthetic aperture radar imagery.

High-resolution records of climate and environmental conditions covering the last 1000 years were produced from chemical and other analyses of ice cores from Law Dome. A lower resolution climate record, covering about 100 000 years, was derived from stable isotope data, trapped gas analysis and other measurements on the Law Dome ice core. This showed that a significant climate cooling event that occurred after the ice age was initiated in the Antarctic-Southern Ocean region rather than being driven by North Atlantic-Greenland processes.

Oceanography

Current meters installed at the summer front of the Amery Ice Shelf have yielded important information on oceanographic conditions that prevail below the winter ice. The movement of water conveys heat towards the Antarctic continent and away from it and this research is integral to understanding of Antarctica's role in the climate system.

A study in February 2003 of the rate of flow of the Antarctic Circumpolar Current at the western edge of the Kerguelen Plateau contributed to a major study of the westerly flow of waters between Antarctica and Australia.

Atmospheric sciences

Measurements by lidar, radar and optical spectrophotometers at Davis continued to provided new data for the development of temperature, wind and aerosol climatologies in the stratosphere (10 to 50 kilometre altitude) and mesosphere (50 to 100 kilometre altitude).

Conditions in the Antarctic stratosphere during the winter and spring of 2002 were unusual. Relatively warm temperatures resulted in the spring ozone hole being the smallest observed since 1988. During September there was an unprecedented and sudden warming of the stratosphere across Antarctica. This event is being investigated using lidar, radar and spectrophotometer data from Davis and other Antarctic sites.

The polar stratospheric clouds season as observed above Davis by lidar was shorter in 2002 (July to August) than in 2001 (July to September). These clouds, which form between altitudes of ten and 25 kilometres during the Antarctic winter, are an important link in the formation of the Antarctic ozone hole each spring. The relatively short polar stratospheric cloud season in 2002 was related to the unusual stratospheric conditions. Observations of structures in the stratospheric clouds using the Davis lidar are yielding new information on the role of atmospheric gravity waves in influencing cloud surface area, which is important for models of ozone depletion.

New understanding of tides in the middle atmosphere has been gained through a collaborative study employing data from Antarctic medium frequency atmospheric radars. These tides are a critical component of atmospheric structure impacting on all models of atmospheric change and the results will improve their representation in atmospheric models.

Analysis of seven years of hydroxyl airglow measurements (a natural atmospheric emission from a layer at 87 kilometres) above Davis has provided the best determination yet of high southern latitude winter temperatures from this region. The inter-year trend is best correlated with solar-cycle changes and within five years it should be possible to deduce if there is an underlying long-term atmospheric change at levels that have been suggested.

Lidar observations at Davis during the 2002-03 summer detected the presence of polar mesospheric clouds in the altitude range 82 to 95 kilometres. These clouds are sensitive indicators of conditions in the mesopause region which is expected to be influenced by anthropogenic climate change. The measurements follow on from similar observations during 2001-02, and Davis is only the second site in the Southern Hemisphere from which the altitude distribution of these clouds has been measured by lidar.

A very high frequency radar system capable of measuring winds and temperatures in the mesosphere and lower thermosphere was established at Davis during the 2002-03 summer. This is the first permanent installation of equipment of this type in Antarctica.

Biology

AAD research is showing the extent to which ultraviolet exposure affects different organisms, which drives changes to the microbial community composition. Ultraviolet altered communities represent a change in food available to grazers and also change the ability of the microbial community to draw down carbon dioxide, which will affect climate.

A new approach using chemical markers in sediments of Ace Lake in the Vestfold Hills suggests the lake was a freshwater-filled meltwater lake 10 450 to 8830 years ago, an open marine system 8830 to about 5000 years ago, and then developed into the present-day lake. The sediments contain high levels of unusual chemicals that are biomarkers for a group of algae common in oceans and estuaries. Their molecular remains could serve as palaeoindicators for marine or brackish water to study long-term climate change.

Geoscience

The Prince Charles Mountains Expedition of Germany and Australia project conducted field mapping and sampling in remote parts of the Prince Charles Mountains to investigate past behaviour of the Lambert Glacier-Amery Ice Shelf system during past climate cycles. Moraines were mapped and bedrock surfaces sampled in order to date the time the ice retreated from the various mountains in the area. This will allow the measurement of past ice heights along the Prince Charles Mountains. Other projects installed global positioning system units to measure post-glacial rebound of the area.

Analysis of a sediment core collected through one of the hot water drill holes in the Amery Ice Shelf suggests that the ice shelf edge retreated up to 80 kilometres during warmer climatic conditions 3000 to 5000 years ago.