Chapter 5 Climate Research

WCRP Activities > Climate and Cryosphere (CliC)

The Climate and Cryosphere (CliC) program is an expansion of the former Arctic Climate System Study (ACSYS) to include investigations of the role of the entire cryosphere in the global climate system. Australian scientists are actively involved with the development of CliC, and much of the ice sheet and sea ice research undertaken within the Australian Antarctic program contributes directly to CliC. A goal of the Government's Antarctic Science Program is to enhance our understanding of the role of Antarctica in the global climate system, and the Australian Antarctic Division (AAD) provides logistic support for climate-related activities in the Antarctic and Southern Ocean.

The field phase of the Amery Ice Shelf - Ocean Response (AMISOR) experiment was completed in 2002 by the Antarctic CRC and AAD. This joint oceanographyglaciology experiment was targeted at ocean-ice interactions beneath the Amery Ice Shelf. The field work included oceanographic instruments deployed through boreholes drilled in the ice shelf, oceanographic sections along the front of the ice shelf, and two-year mooring deployments to measure the major inflow and outflow of water from the cavity beneath the ice shelf. One surprising discovery at one of the borehole sites was that the bottom 100m of the nearly 200m thick refrozen marine ice layer on the bottom of the shelf was unconsolidated, and porous to the ocean. This knowledge provides insight into the timescale and processes of basal freezing, and on the subsequent stability of icebergs that calve from the shelf.

The thickness of sea ice and its regional and seasonal variability is one of the most important, but least known, Antarctic climate variables. A compilation of shipboard sea ice observations, collected during many Australian and other national voyages, has provided the first distribution of sea ice thickness and its variability for the entire Antarctic sea ice zone. Measurements from two Ice Profiling Sonar instruments moored beneath the ocean surface near the Mertz Glacier polynya in 1998 and 1999 have been analysed to produce detailed ice thickness records for that region.

A variety of different techniques has been used to determine the surface movement of the Antarctic ice sheet and ice streams from satellite data. This work is assessing whether the mass of ice in Antarctica is stable, increasing or declining. The techniques include tracking recognisable features in visible-light imagery (e.g. using Landsat data for the Denman Glacier) and interferometric analysis of daily synthetic aperture radar data in areas where surface features are not easily recognisable (e.g. Law Dome, Amery Ice Shelf). Data from the satellites are providing information on ice outflow from vast areas of the ice sheet, and supplementing ground based measurements of ice velocity and strain.

The high resolution and accurately dated record from the Law Dome ice core provides new insight into abrupt changes in climate 14,500 years ago, at the end of the last Ice Age. The Law Dome results show that East Antarctic changes led, rather than followed, the large changes seen in the northern Polar region. This challenges the traditional view that variations in the North Atlantic, typically from freshwater input from decaying glaciers, drives changes in both hemispheres via ocean circulation.

The national Antarctic science program has recently had a focus on Heard Island, and Macquarie University carried out field work on the Island in 2000-01 and 2002-03 related to climate change impacts on vegetation and invertebrates. During these studies, it was found that Karman vortices occur in the surface winds on the leeward side of the Island.