Carbon released from oceans may have warmed the Earth, ending the last major ice age, new analysis reveals.

University of Southampton researchers studied fossilized plankton, revealing that oceans were more acidic between 16,000 and 7,500 years ago than they are today. This effect may have been driven by carbon rising from deep beneath the surface of the water, driven by currents. These releases may have taken place in both the eastern equatorial Pacific Ocean and the Southern Atlantic Ocean.

If this new theory is confirmed by other research, the process may have precipitated the end of the ice age, which led, in part, to human civilization. Geologists and climatologists are uncertain exactly what drove the Earth to begin warming from frigid conditions to the far-milder climate of the modern day.

Atmospheric carbon levels fluctuate between 185 and 280 parts per million, with the lowest figures during ice ages.

The global ocean is capable of storing up to 60 times as much carbon as can be held by the atmosphere of the Earth. However, carbon can quickly move from water to air, releasing a torrent of greenhouse gases to the atmosphere. Through this process, oceans could be a major factor in altering concentrations of carbon in the atmosphere.

"While a reduction in communication between the deep-sea and the atmosphere in this region potentially locks carbon away from the atmosphere into the abyss during ice ages, the opposite occurs during warm interglacial periods," Miguel Martínez-Botí of the University of Southampton said.

Calcium carbonate within the shell fossils was examined, in order to determine the amount of carbon present in the structures.

"We found that very high concentrations of dissolved CO2 in surface waters of the Southern Atlantic Ocean and the eastern equatorial Pacific coincided with the rises in atmospheric CO2 at the end of the last ice age, suggesting that these regions acted as sources of CO2 to the atmosphere," Gianluca Marino of the Australian National University, said.

Oceans may be absorbing up to 30 percent of the atmospheric carbon produced by human beings. However, researchers warn that these deposits could be suddenly released by the waters, into the atmosphere, potentially leading to a dramatic rise in global warming. The same process which ended the last ice age could also push our modern climate into dangerous conditions, and accelerate climate change.

Study of the effects of carbon release from the oceans and the end of the last ice age was profiled in the journal Nature.