Indicator: AAT-15 Glacier movement

Data

In 1947, Heard Island's glaciers covered 288 km² or 79 percent of the island. By 2000 this had decreased by 12 percent to 253 km². 35 km² of new terrain, including several large lagoons, have been exposed by ice retreat, representing nearly 10% of the total area of the island.

At the end of the 1980s, a total of 29 glacier basins and 41 termini with a total estimated ice volume of about 14 km³ covered 70 percent of the island. Smaller glaciers such as Nares, Mary Powell, Brown, Deacock and those on the Laurens Peninsula have significantly receded, but the larger glaciers such as Gotley, Abbotsmith, Downes and Ealey show little or no change since 1947.

Source: Department of the Environment and Heritage 2006, Our subantarctic glaciers: why are they retreating?, viewed 5 Jul 2006, http://www.aad.gov.au/default.asp?casid=2100

What the data mean

A glacier can be viewed as a 'balance sheet'. If the water equivalent of what goes in (snow accumulation) is less than what goes out (melt loss or calving), then the glacier will recede to a cooler, higher elevation where both components are 'balanced'.

The fluctuation pattern evident in the diversity of glaciers on Heard Island indicates a climatic cause rather than a change in volcanic activity. About half of the change that occurred between 1947 and 2000 occurred during the 1980s, when summer temperatures were about 1.7°C higher than the 1946-54 average. The change in area has significant implications for plants and animals on the island and also for the conservation of cultural heritage items.

The smaller, shorter glaciers are much more sensitive to temperature effects. Since 1947, the total area of Laurens Peninsula glaciers has decreased by over 30 percent.

Data Limitations

Nil known

Issues for which this is an indicator and why

Australian Antarctic Territory — Environment - The ice and land

Any changes in glacial area on Heard Island are bound to have significant local implications in terms of plants and animals on the island and also for the conservation of cultural heritage items.

Heard Island glaciers have a relatively small ice volume, so the contribution to sea-level rise through glacial melt is not a concern. However, the unique climate signal that is coming from this predominantly oceanic region is of vital importance. It indicates that the change observed elsewhere in Southern Hemisphere mid-latitudes - in New Zealand, Patagonia, Kergeulen Island, South Georgia and Bouvet Island - is widespread.