The Atlantic, the Pacific… are sinks. Heat sinks. So says Scientific American, explaining that temperatures haven’t risen as sharply as they could have (YET) because the oceans are absorbing some of the excess heat:
The heat sink occurs when sun-warmed salty water from the tropics travels along ocean currents in the Atlantic to the coasts of Greenland and Iceland. When the saltier tropical water reaches the North Atlantic, its greater density causes it to sink, in a process called warm saltwater subduction.
“When [the water] sinks, it goes straight down, and the sinking carries heat along with it,” [University of Washington professor Ka-Kit] Tung said.
About 90 percent of the Earth’s heat is stored in the oceans due to the atmosphere’s limited storage capacity, according to the study.
The researchers said that about half of the warming in the last 30 years of the 20th century was due to global warming, while the other half was from the heat cycle in the Atlantic that kept heat near the ocean’s surface.
The last time the Atlantic current shifted was around 2000. Since then, the change in the global annual mean surface air temperature has held steady around .5 degree Celsius (.9 degree Fahrenheit) above the base period average set from 1951 to 1980, according to data from NASA’s Goddard Institute for Space Studies.
Based on previous trends, the current “cooling” cycle is likely about halfway over, he said. Rapid warming is expected to resume again in about a decade, though exact predictions are difficult to make.