Earth Planet. Sci. Lett. 227, 156–165 (2009)

Ancient ooze from the bottom of the Pacific provides evidence that the deep ocean sucked up vast amounts of carbon dioxide during the last ice age, thus cooling the planet.

In making this argument, Samuel Jaccard of the Swiss Federal Institute of Technology in Zurich and his colleagues resurrected a hypothesis first proposed 20 years ago. The idea had been discounted, but the team obtained new data from trace elements locked in ice-age ooze, collected from the ocean bottom by a drillship. That evidence, along with a revised understanding of nutrient dynamics in the ocean, suggests deep Pacific waters held less oxygen and stored much more carbon dioxide than previously thought, say the researchers.