York professor studies gravity to understand global warming

York University Professor Spiros Pagiatakis (left) is helping to piece together a picture of global warming using surveyors’ gravity observations and notes from the 1940s and satellite observations from today.

The professor of geomatics engineering has analyzed five decades of measurements of gravity to determine how the earth’s crust is springing back from the last Ice Age – a process known as post-glacial rebound. His next move is to sketch in the details with data collected by satellites, and particularly by Global Positioning System technology.

Pagiatakis’ research is part of a broad effort to understand global warming. “Torontonians may blame the summer’s heat waves on their neighbours’ sport utility vehicles,” he says, “but the earth has been experiencing a warming trend since the glaciers began to melt – probably about 21,000 years ago.

“I’m not saying that cars, industries and in general human activity are not causing the earth to warm,” says Pagiatakis. “But we have to put it into perspective and ask, ‘Is there any general trend that the earth has been experiencing since thousands of years ago when we didn’t have these gas emissions from vehicles?’ “

Pagiatakis is helping to answer this question with scientists from many disciplines and countries. His expertise is in analyzing data. As the ice melts, the earth’s crust is lifting, which creates a reduction in gravity intensity. Pagiatakis has analyzed gravity measurements and field notes taken by government surveyors since the 1940s to track this uplift in the earth’s crust, which occurs at a rate of only one centimetre per year in the area of Hudson’s Bay. He is adding new types of measurements to these earlier findings and developing a more sophisticated model for the mathematical processing of the observations.

“What we are doing now is measuring the water levels using satellites,” he explains. “We can really see that the Great Lakes are tilting. The centre of the ice was in Hudson’s Bay, so as the area north of that moves up, there is a tilt toward the south.”

The goal is to compile even more reliable data for geophysicists and other scientists who are studying the dynamics of our planet and climate change, Pagiatakis says.

“We can use this information to reconstruct the ice history, going back many tens of thousands of years or even more, so that we can really study the climate of the earth and see how the planet changed over thousands of years,” he says.