A shift in perspective: Australia found to tilt and gyrate with the weather
A world-first discovery from the University of Newcastle (UON) has shown the continent of Australia tilts and shifts in a coherent gyrating motion as a result of seasonal weather patterns across the globe.
Professor Shin-Chan Han, a geodesist with NASA and academic in UON’s School of Engineering, has utilised a combination of GPS data along with data from the Gravity Recovery and Climate Experiment (GRACE) satellites, both of which measure ground deformation, to discover a ‘seasonal gyration’.
“The new research shows Australia sinks and rises between 3mm – 5mm in response to the mass change across the globe, as well as shifting northwest 1mm during the southern hemisphere’s summer and moving back during the winter,” Professor Han said.
Although small, the movement symbolises a significant discovery.
“The whole continent is basically leaning toward where the earth is heavier.
“Australia experiences a larger mass shift than other continents due to its unique location in relation to global weather patterns, so understanding the impact these factors have is vital in understanding the reasoning behind the movement,” he said.
Seasonal mass change is effected by multiple factors, including atmospheric pressure, ocean mass, ground water storage and the ice/snow cycle.
“When the southern hemisphere is experiencing summer, there is more mass in Europe due increased rainfall, snow and water distribution. With a change in season and shift in mass as a result of evaporation, Australia responds by tilting toward the heavier area.
“The combination of this tilt with the natural continental drift the country experiences throughout the year results in an elliptical movement or ‘gyration’,” he said.
Professor Han said that, whilst we anticipate every continent is in motion, he didn’t expect to discover such a large elliptical motion in response to the weather.
“It’s an exciting development in that we now know we can use these forms of surveillance to track the slightest of movements, which are vital in the long-term planning for our response to climate change,” Professor Han said.
A recently re-appointed geodesy professor with NASA, Professor Han has worked extensively on GRACE, the data of which has influenced his current research. The GRACE satellites measure ground deformation, relying on the Earth’s centre of mass (CM) to inform its findings.
As the CM is known to be shifting, the combination of GRACE data along with GPS data from the earth’s surface has allowed Professor Han to more accurately track the surface deformation across Australia and the world.
“It was important to cross reference the data to ensure we have the most accurate reading possible, as this will influence our knowledge in the long term,” he said.
Dr Han’s discovery is detailed in Seasonal clockwise gyration and tilt of the Australian continent chasing the center of mass of the Earth's system from GPS and GRACE: Seasonal continental deformation, published in the Journal of Geophysical Research: Solid Earth.