Washington, Mar 30 : Processes in the ocean are responsible for the scarcity of carbon dioxide in the atmosphere during the last Ice Age 20,000 years ago and making it rise when the Earth's climate became warmer, a new study has claimed.
Around 20,000 years ago, the atmospheric CO2 concentration during the last Ice Age was distinctly lower than in the following warm period.
Measurements from Antarctic ice cores showed this already two decades ago. An international team of glaciologists thereafter looked even further back in time.
The climate researchers from the Universities of Bern and Grenoble and the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association found that this close connection between carbon dioxide and temperature has existed over the past 800,000 years - with low CO2 concentrations during the Ice Ages and higher CO2 values during warm periods.
Now they tried to answer also the question as to where the carbon dioxide was hidden during the Ice Ages and how it got back into the atmosphere at their ends.
"We have now been able to identify processes in the ocean which are connected to the observed rise in CO2," Jochen Schmitt, lead author of the study, said.
According to Schmitt, during the Ice Age more and more carbon dioxide accumulated in the deep ocean, causing the concentration of atmospheric CO2 to drop. Only at the end of the Ice Age was this stored CO2 transported back to the sea surface through changing ocean circulation and thus emitted back into the atmosphere.
A new method for isotope measurements has now made it possible for the first time "to reliably decode the fingerprint of the CO2 preserved in the ice".
Schmitt and his colleague Hubertus Fischer initially developed these new isotope measurement methods for ice cores at the Alfred Wegener Institute for Polar and Marine Research and further refined them in many years of research work after moving to Bern.
Using the new method the glaciologists extract the air trapped in the ice core completely and the CO2 contained in the air is thoroughly cleaned. The different isotopes of the CO2 are analysed in a mass spectrometer and from this data the origin of the carbon dioxide can be derived.
Researchers suggested back in the eighties that this puzzle could be solved using an isotopic "CO2 fingerprint". However, it had so far not been possible to make a precise analysis of the carbon dioxide trapped in the Antarctic ice due to the technical hurdles.
The glaciologists and the climate researchers at the Universities of Bern and Grenoble and of the Alfred Wegener Institute for Polar and Marine Research have now managed a breakthrough with their study.
"The new data have already enabled us to revise and improve a few theories about the possible reasons for CO2 fluctuations. Measurement data from the past enable us to gain a clearer idea about how the climate must have looked at the end of the Ice Age," Schmitt said.
Now, the data must be compared with the results from climate models to verify and further develop the models.
"In addition to the scientific curiosity about how our Earth functioned in the past, the main question to be asked is how the Earth will develop under the influence of man," Schmitt added.
The climate researcher concluded that these are important scenarios for the future because the CO2 content in the atmosphere has never been anywhere near as high over the past 800,000 years as today.
The study has been published in the scientific journal Science. (ANI)
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