Most concerns about climate change stem from the amount of greenhouse gases in the atmosphere, but ocean circulation plays just as important a part as air, new research says.
Some three million years ago, carbon dioxide (CO2) levels in the atmosphere were comparable to what they are now, and temperatures were four degrees Fahrenheit higher. But it was shifts in ocean circulation that cooled the Earth and created the climate that we live in now.
Changes in the ocean conveyor system, Rutgers scientists believe, coincided with a major cooling of Earth and continental ice build-up in the Northern Hemisphere some 2.7 million years ago. The way the system works is it moves heat and water, as well as CO2, between the Earth's hemispheres along the ocean bottom. What happened, researchers argue, is that a shift in ocean circulation caused heat and CO2 in the Atlantic to move southward through the deep ocean, later to be released in the Pacific. This triggered the Northern Hemisphere's ice sheets to expand. So the ocean, not the presence of CO2, caused global climate change at that time.
The findings are described in the journal Science.
Researchers from Rutgers University based their suspicions on ocean sediment core samples dating back 2.5 to 3.3 million years ago. These findings could provide scientists with a deeper understanding of the mechanisms of climate change today.
"Our study suggests that changes in the storage of heat in the deep ocean could be as important to climate change as other hypotheses - tectonic activity or a drop in the carbon dioxide level - and likely led to one of the major climate transitions of the past 30 million years," Yair Rosenthal, co-author and professor of marine and coastal sciences at Rutgers, said in a statement.
Oceans, while they may be a major player in climate change, also hold the potential of alleviating the amount of greenhouse gases that enter the atmosphere, mainly methane. A recent study showed that certain microbes living in deep ocean rock consume methane and reduce their presence in the air.
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