Global warming has slowed in recent years, and now scientist think the reason may be found in the Atlantic Ocean. A slowdown in global warming has been observed since the turn of the century, puzzling researchers studying the global environment.
Climatologists have proposed several hypotheses to explain this hiatus in increasing rates of warming. Sunspots were thought by some researchers to be responsible for the slowdown, while others stated their belief the cause was air pollution or volcanoes. However, none of these theories could adequately explain the great period of time heating has been reduced.
University of Washington (UW) researchers showed the Atlantic Ocean may be acting as a heat sink, absorbing much of the heat that would have otherwise been released into the atmosphere over the last decade-and-a-half.
"Every week there's a new explanation of the hiatus. Many of the earlier papers had necessarily focused on symptoms at the surface of the Earth, where we see many different and related phenomena. We looked at observations in the ocean to try to find the underlying cause," Ka-Kit Tung, professor of applied mathematics and atmospheric sciences, said.
At the turn of the 21st Century, a slow current in the Atlantic Ocean began to speed up, drawing heat from top waters down to greater depths, nearly a mile under the surface.
Argo floats, sampling water up to 6,500 feet beneath the surface of the ocean, showed the current started bringing greater-than-normal amounts of heat into the ocean at the same time heating on the surface slowed. Salt-rich water near Iceland sinks deep beneath the waves, traveling to the tropics. There, it warms up, traveling north once more to repeat the process.
"The finding is a surprise, since the current theories had pointed to the Pacific Ocean as the culprit for hiding heat. But the data are quite convincing and they show otherwise," Tung told the press.
This current, trapping heat a mile beneath the Atlantic, could quickly reverse, quickly releasing thermal energy back into the air. If researchers are correct, the 30-year cycle of the process could release large amounts of heat into the atmosphere sometime around the year 2030.
Rapid warming in the last three decades of the 20th Century could have been caused in part by this cycle in the Atlantic, Tung told the press. He believes up to one-half of all global warming seen during those years could have been due to the release of thermal energy from this process.
Study of how the Atlantic Ocean could be acting as a heat sink, leading to the recent slowdown of increasing global temperatures was profiled in the journal Science.
