The presence of glaciers on Heard Island provides an excellent opportunity to measure the rate of glacial retreat, as an indicator of climate change.
Records of the glaciers on Heard Island have many gaps, relative to those of more accessible glaciers located closer to populated areas.
Glaciology research undertaken on the island in the summers of 2000/01 and 2003/04 is attempting to fill some of these gaps. The research is concentrated on the Brown Glacier, on the north-eastern coast of the island.
The aim is to study Brown Glacier’s ‘mass balance’ – the difference, if any, between the input of snow, and output of melt water. If the input equals the output over a number of years, the glacier will not shrink or grow. If the input of snow is less than the output of meltwater during summer, the glacier will shrink or ‘retreat’.
Field work involved measuring such things as accumulation and melt rates of ice, altitudinal variations in precipitation and temperature, and dynamic properties of the glacier such as ice thickness and velocity, all in an attempt to determine the mass of ice that flows through the system.
Results so far have shown that the glacier had retreated 50 metres since the 2000/01, contributing to a retreat of approximately 1.1 kilometres since 1950 (a decrease in total volume of about 38%). The glacier was also found to have decreased in thickness by up to 11 metres on its lower slopes and 4 metres on its upper slopes – this translates to a loss of about 8 million cubic metres of ice each year over the three years.
These changes in the glacier, which appear to be accelerating, suggest that the climate is continuing to warm. The researchers have installed markers and automatic weather stations, and taken ice samples to allow further evaluation of changes to the glacier in coming years.
It is hoped that this research will provide insights into the variability and broader effects of climate change in the Southern Ocean, and further south towards Antarctica.