CORVALLIS, Ore. At the end of the last Ice Age, atmospheric carbon dioxide levels rose rapidly as the planet warmed; scientists have long hypothesized that the source was CO2 released from the deep ocean.
But a new study using detailed radiocarbon dating of foraminifera found in a sediment core from the Gorda Ridge off Oregon reveals that the Northeast Pacific was not an important reservoir of carbon during glacial times. The finding may send scientists back to the proverbial drawing board looking for other potential sources of CO2 during glacial periods.
The study, which was supported by the National Science Foundation and the University of Michigan, was published online this week in Nature Geoscience.
"Frankly, we're kind of baffled by the whole thing," said Alan Mix, a professor of oceanography at Oregon State University and an author on the study. "The deep North Pacific was such an obvious source for the carbon, but it just doesn't match up. At least we've shown where the carbon wasn't; now we just have to find out where it was."
During times of glaciation, global climate was cooler and atmospheric CO2 was lower. Humans didn't cause that CO2 change, so it implies that the carbon was absorbed by another reservoir. One obvious place to look for the missing carbon is the ocean, where more than 90 percent of the Earth's readily exchangeable carbon is stored.
The Pacific Ocean is the largest ocean by volume. The deep water mass longest isolated from the atmosphere and most enriched in carbon is found today in the Northeast Pacific, so the researchers focused their efforts there. They hypothesized that the ventilation age in this basin or the amount of time since deep water was last in contact with the atmosphere would be older during glacial times, allowing CO2 to accumulate in the abyss.
"We were surprised to find that during the last ice age,
|Contact: Alan Mix|
Oregon State University