New ETH Zurich article published in scientific journa...( The air contains greenhouse gases su...)

The air contains greenhouse gases such as CO₂, which are now known to be responsible for global warming because their concentration has risen continu-ously for a number of years. In contrast to the atmosphere, the concentration of CO₂ in the oceans is sixty times higher. In the global carbon cycle the sea ab-sorbs a proportion of the atmospheric CO₂ but also releases CO₂ into the at-mosphere again. About half of the anthropogenic emission of CO₂ is absorbed naturally by the oceans. Thus it is all the more important to understand how the exchange of CO₂ between the ocean and the atmosphere functions with regard to a world that is warming up. The newly available study shows that the ocean was able to store more CO₂ during the ice age than it can today.

Practically static bodies of water

Together with North American colleagues, an ETH Zurich research team made measurements on sea bed sediments. These sediments originate from moun-tains lying at a depth of about three kilometres below the water surface of the sub-Arctic Pacific Ocean. At that point the water temperatures are close to freezing and the conditions are very stable, because there is practically no mix-ing between the deep bodies of water and the surface water. The circulation of the water is measured using the radio-carbon method, which is based on the radioactive decay of the carbon isotope 14C. Measurements showed that the deep Pacific water has not been at the surface for more than 2,000 years.

Tiny single-celled organisms betray the CO₂ level

To find out how the situation has changed compared to the last ice age, the re-searchers studied mud from the sub-Arctic Pacific Ocean lying approximately one metre below the present sea bed and about 20,000 years old. Tiny single-celled organisms with limestone shells known as foraminifera were selected from this mud under a
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