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
|Contact: Samuel Jaccard|
ETH Zurich/Swiss Federal Institute of Technology