Deep Oceans Have Seen Decade of 'Unprecedented' Warming

Measurements from a new reanalysis of global ocean heat content indicate that the past decade has seen an unprecedented period of deep ocean warming, according to research published in the journal Geophysical Research Letters.

Climate scientists puzzling over "missing heat"-- the unaccounted for energy as a result of an imbalance in solar heat penetrating the atmosphere versus the amount of heat leaving the atmosphere -- in the Earth's energy budget make the case that despite ocean surface warming seeming to stall since 2004, the heat is still warming the oceans, albeit at lower depths.

Researcher Magdalena A. Balmased and colleagues accounted for the missing heat in a massive actuarial undertaking that sought to measure the oceans' thermal energy over the last half century.

The researchers found that although the upper ocean waters, from the surface to 700 meters (2,300 feet) depth, showed no warming from 2004 to 2008, the waters from 700 to 2000 meters (2,300 to 6,500 feet) were warming at an unprecedented rate.

They found that during the last decade, 30 percent the excess energy trapped by the anthropogenic greenhouse effect that has gone into warming the deep ocean.

The above image outlines where the heat is going. The deep oceans, represented by the purple line, have risen in heat content much greater than the oceans at 300 meters and less. A sharp upward climb seems to occur at the beginning of this century.

To put the amount of heat the deep ocean is absorbing into perspective, the science blog Deep Sea News compared the 2008 energy intake to annual amount of energy produced by people:

"The average person in the U.S. uses about 301 Gigajoules of energy. So in 2008, the deep oceans took in the equivalent energy of that produced by 6,644,518,300,000 people (>6.6 trillion people)."

The Earth has about 7 billion people, which means in the same year, we produced about 943 times less equivalent energy than the deep oceans absorbed.

In addition to making note of unprecedented ocean warming, the researchers also noted periods of ocean cooling following major volcanic eruptions.