Scientists are trying to understand why the amount of CO2 in the atmosphere changed by about 90 parts per million (ppmv) between icy (glacial) and warmer (interglacial) periods in Earth’s history. This is a big question in climate research. Even though these cycles between cold and warm periods seem to follow a pattern, scientists believe many different natural processes are involved in causing the CO2 changes.
AW Omta, visiting assistant professor in the Department of Earth, Environmental and Planetary Sciences at the College of Arts and Sciences, led a study looking at how much carbon is stored in the ocean, especially the carbon trapped by living things like plankton. The research team’s findings were published recently in Nature Communications.
They found that this stored carbon can explain a change in atmospheric CO2 levels of about 75 ppmv, give or take 40 ppmv. They used data from studies that measured carbon isotopes (different forms of carbon atoms) to calculate this.
When they analyzed different parts of the ocean, they saw that the amount of regenerated carbon (carbon that has been used and then released back) was about the same during the Last Glacial Maximum (the coldest part of the last ice age) and during the Holocene (the warm period we are in now). This means that the change in CO2 likely came from something else, like how much carbon the ocean and atmosphere exchanged (disequilibrium), rather than just from how much carbon was stored.
The scientists think this disequilibrium might have been caused by either the expansion of sea ice or changes in how ocean water moves (circulation patterns).
In short, being able to explain climates of the past will put our future projections on a stronger footing.