In a forthcoming study in the journal Geophysical Research Letters, researchers report Pacific island soft corals reveal the “thermocline”, the point where cold, deep water meets warm surface water has gotten shallower, an indication of decreased ocean circulation predicted by global warming models.

“Climate modelers looking at how the Pacific might respond to global warming have predicted that the atmospheric patterns in the tropical Pacific would weaken, and if that happened, you would expect the thermocline to get shallower in the western tropical Pacific,” says study co-author Branwen Williams of the University of Toronto, in a statement. “Our data are some of the first proxy data to support what the modelers have been predicting.”

In the study, the researchers looked at corals at depths of 16, 280 and 345 feet depth, looking at how they grew in tree-ring-like patterns over time that are revealed in nitrogen and carbon measurements. Cold water brings more nutrients to the corals, leading to more growth, and serving as an indicator of circulation strength in the Pacific Ocean.

“Over several decades, specifically since the mid- to late-1970s, the records show that the mean depth o

f the thermocline has been getting shallower,” Williams says.

By Dan Vergano

See photos of: Pacific Ocean