Susan Lozier head shot

Susan Lozier

Overturning Assumptions

For years, many scientists assumed that waters in the Labrador Sea off Canada were the primary drivers of Atlantic meridional overturning circulation (MOC), a deep-sea process in which warm, salty waters from the tropics mix with colder, fresher water and sink into the depths, carrying vast amounts of climate-warming anthropogenic carbon with them.

A landmark study in 2019 by former Nicholas School faculty member Susan Lozier sank that theory. Based on empirical data from a 21-month study of the North Atlantic basin, Lozier’s paper showed that waters in the eastern section of the basin, between Scotland and Greenland, were the MOC’s main drivers.

The paper also showed the rate of overturning taking place in those waters may be starting to change. “We found overturning variability in the eastern section of the North Atlantic was seven times greater than in the Labrador Sea over the study period,” says Lozier, a physical oceanographer who is now dean of the College of Sciences at Georgia Tech.

It’s too soon to know if this means the MOC is weakening, but informed by Lozier’s findings, scientists are now better positioned to predict future changes and project what their impacts could be.