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Past Winner
2002 E.W.R. Steacie Memorial Fellowship

Jerry Mitrovica

Geophysics

University of Toronto


Jerry Mitrovica
Jerry Mitrovica

For the past 15 years, Jerry Mitrovica has been shaking up how we see the Earth. The University of Toronto geophysicist has been at the forefront of global research seeking to better understand our planet not as a static ball, but as a dynamic interplay between atmosphere, water, continents and the deep Earth.

It's world-leading research for which Dr. Mitrovica is being awarded a 2002 Natural Sciences and Engineering Research Council (NSERC) E.W.R. Steacie Memorial Fellowship - one of Canada's premier science and engineering prizes.

In the late 1980s, when Mitrovica began his research career, geophysicists were increasingly adapting an Earth systems approach to their subject as a result of one of the last century's greatest scientific insights: plate tectonics. The understanding that the Earth's crust is a series of slowly moving rigid segments, or plates, on a viscous middle layer, was synthesized by University of Toronto geophysicist Tuzo Wilson in the 1960s.

"While in the 1970s we knew some of the geological implications of plate tectonics, we didn't know how it connected to long-term climate or sea-level changes," says Dr. Mitrovica, now the J. Tuzo Wilson professor of geophysics at U of T.

In 1989, Mitrovica, then a doctoral student, rocked the plate tectonics community by demonstrating - with colleagues Dr. Chris Beaumont of Dalhousie University and Gary Jarvis of York University - that the same process moving continents sideways, was also moving them up and down.

Vertical plate tectonics, as its been dubbed, is crucial to understanding ancient sea level changes.

In their seminal journal article, the researchers showed that the great interior seaway that covered the North American interior from 80 to 50 million years ago was the result of the continent being pulled down by an oceanic plate subduction zone at the continent's western edge. Like two rafts attached side by side, when one is pulled down, the other also tilts down, he notes.

In a highly-publicized article in Nature last year, Dr. Mitrovica extended this research into plate tectonics as well as his work into ice age sea level changes to redefine how current sea level changes are interpreted. Prior to this article, the common belief was that sea level changes due to the melting of polar ice sheets follow a "global bathtub" model - rising and falling uniformly around the globe, says Mitrovica.

Re-applying a 19th century idea, Dr. Mitrovica and his colleagues showed that each ice sheet has a distinct 'sea level fingerprint.' In general sea levels rise in the opposite hemisphere to the melting ice due to the reduction in the gravitational pull of the ice mass.

"The very idea that sea levels should rise uniformly if the ice sheets are melting is wrong. It's dramatically non-uniform," he says. "If the Greenland ice sheet melted tomorrow there'd be flooding in the southern hemisphere but a sea-level fall in Scotland and Newfoundland."

Mitrovica is continuing his research into the Earth's subtle interconnections and, with California Institute of Technology's Dr. Jeroen Tromp, U of T post-doctoral fellow Dr. Konstantin Latychev and others, he is developing a computerized 3-D numerical model of an ice age Earth. This finite element model - in which the Earth is subdivided into a grid with distinct geophysical data for each 50 kilometre surface section - will enable unprecedented analysis of past and future Earth changes.

"We need models that take into account a more complex, realistic Earth," Dr. Mitrovica says.

In search of great ideas, Jerry Mitrovica scours the Earth for useful data. The University of Toronto geophysicist credits the Canadian Institute for Advanced Research's (CIAR) Earth Systems Evolution group for helping foster numerous of his insights since he was elected a member in 1997. Through this scientific think tank program, Dr. Mitrovica meets twice a year for a free-wheeling brainstorm of earth evolution ideas with an international group of colleagues, half of whom are Canadian. "There's nothing like the CIAR anywhere else in the world. Canada has benefited incredibly from it," says the 2002 NSERC Steacie Fellow.