Past global photosynthesis reacted quickly to

image: In collaboration with the Laboratoire des Sciences du Climat et de l’Environnement, France, the PICE team studied ancient air trapped in tiny air bubbles in an Antarctic ice core. The ice core represents the last 800,000 years of climate development.
to see Continued

Credit: Photo: S. Kipfstuhl, AWI

Ice cores allow climatologists to go back 800,000 years: atmospheric carbon acts as fertilizer, increasing biological production. The mechanism removes carbon from the air and thus mitigates the acceleration of global warming.

Even under Ice Age conditions, plants, plankton and other life will be able to increase their production whenever atmospheric carbon concentrations increase. The mechanism will not prevent a continued global warming trend, but at least dampen the acceleration. This conclusion stems from an international collaboration involving the Physics of Ice Climate Earth (PICE) center at the Niels Bohr Institute of the University of Copenhagen.

“The global biosphere production by photosynthesis is the strongest absorbing flux of atmospheric carbon dioxide. It is therefore essential to understand its natural variability for a better projection of the future carbon cycle,” says postdoctoral researcher Ji-Woong Yang, PICE, continuing:

“Today, as we have Earth observation satellites and other advanced equipment, the mechanism of carbon fertilization is well established. However, we weren’t sure that the same mechanism existed in past periods when the climate was very different and atmospheric carbon concentrations were much lower. The new results confirm the existence of the strong correlation and allow us to model future developments with more confidence.

Eight glacial cycles are covered

In collaboration with the Laboratoire des Sciences du Climat et de l’Environnement, France, the PICE team studied ancient air trapped in tiny air bubbles in an Antarctic ice core. The ice core represents the last 800,000 years of climate development.

Scientists take advantage of the fact that the oxygen atom does not exist only in the most common form 16O with 8 protons and 8 neutrons but also as isotopes 17O and 18O. The isotopic composition is a tracer of the productivity of the biosphere. Uniquely, the method will show the overall level of organic production unlike other methods which give more localized results.

By combining air bubble measurements with modeling of oxygen behavior in the biosphere and stratosphere, researchers were able to quantify changes in biosphere productivity under glacial periods (ice ages) and periods interglacial. A total of eight glacial cycles were covered.

“The results clearly demonstrate that productivity declines during glacial periods and increases during interglacial periods. In addition, a strong correlation exists with past concentrations of carbon dioxide in the atmosphere measured from several ice cores. Additionally, the effect is greatest during ice ages when the level of carbon dioxide and the overall productivity of the biosphere begin to increase several thousand years before the ice sheets begin to melt. This correlation is explained by the strong effect of fertilization by atmospheric carbon dioxide”, explains Ji-Woong Yang.

An article on the results of Antarctic ice core studies will be published in the prestigious scientific journal Science on March 11, 2022.

Contact

Ji Woong Yang

Post-doctoral researcher

Niels Bohr Institute

University of Copenhagen

[email protected]

+33 7 66 26 61 96


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