The Australian continent moves with the weather
THE CONTINENT OF Australia has been found to tilt and gyrate in response to global weather changes.
New research from the University of Newcastle, New South Wales, has shown that when summer hits the Southern Hemisphere, Australia literally tilts towards Europe. The researchers found the continent sinks and rises by a few millimetres as the distribution of the Earth’s water mass shifts with the seasons.
“The Australian continent is chasing the point where the Earth is heaviest,” explained lead researcher Professor Shin-Chan Han, a geodesist who specialises in measuring and modelling the geophysical processes of the Earth.
During winter in the Northern Hemisphere, Europe becomes heavier due to an increase in ice, snow and rainfall at this time of year. This shift in mass causes the Australian continent to tilt towards Europe, where the Earth is heavier. The north-western corner of Australia sinks, while the south-eastern corner rises.
As the seasons change and winter moves to the Southern Hemisphere, Australia tilts in the opposite direction, causing a yearly clockwise rotation that Han has coined “seasonal gyration”.
Professor Shin-Chan Han, University of Newcastle. (Image: UON)
The findings are a world-first discovery, made using data collected from the Gravity Recovery and Climate Experiment (GRACE) satellites. GRACE satellites measure ground deformation in relation to the Earth’s centre of mass. This, along with GPS data, has allowed Han to track the movement of the Australian continent.
The discovery came as a surprise to researchers. While it’s known that all continents shift and move, no one expected Australia to express such a large elliptical movement. Han also didn’t expect that changing global climate could elicit this kind of response.
The study has helped to identify how the Earth’s centre of mass (CM) moves. It has been common knowledge for several years now that the Earth’s CM isn’t a fixed or stable point, but there has been huge uncertainty around its actual motion. Cross-referencing the GRACE data with GPS data has revealed how the Earth’s CM moves with the changing seasons, and how the Australian continent seems to move with it.
“It’s an exciting development,” Han said. “We now know we can use these forms of surveillance to track the slightest of movements.”
Matt King, a professor of polar geodesy at the University of Tasmania who wasn’t involved in the research, recognised the significance of the new findings. “This study provides a new way to monitor Earth’s centre of mass,” he said.
“There’s a need to be able to monitor it so that surveyors and scientists know what their satellite and GPS measurements are relative to and how their ‘reference point’ is moving.”
Han has said that the next step for this research will be to look at how both the pre-2010 drought and the 2010-2012 La Niña event have affected continental movement.
