Ocean Secrets

Louisa Bradtmiller

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CATEGORY: Academics
TYPE: Articles
RELATED PROGRAMS: Environmental Studies

 

The question is this: Will temperature and CO2 continue to share the same pattern in the future that they have shared for the last 600,000 years? If so, it's going to warm up very quickly, given how much higher the atmospheric CO2 concentration is now.

Paleoclimatologists have long wondered why atmospheric CO2 was so much lower during the last glacial period. Where did the carbon go? Macalester environmental studies professor Louisa Bradtmiller demonstrates in a new paper that the deep Pacific Ocean (below 2000 meters) likely stored more carbon during the last glacial period than during the Holocene (the last 10,000 years of the Earth's history -- the time since the end of the last major glacial epoch, or "ice age").

The red line shows concentrations of carbon dioxide in the atmosphere over the last 600,000 years (**the scale on the bottom is in thousands of years). The black line shows an indicator of temperature over the same time period. Notice that the red line and black line seem to change in the same direction at very similar times.

It is well known that atmospheric CO2 was approximately 80 ppm lower during the last glacial period than during pre-industrial times, but where the carbon was stored during the ice age has been difficult to identify. Bradtmiller is the lead author of a paper that presents evidence from 10 equatorial Pacific Ocean sediment cores showing that the glacial equatorial Pacific Ocean likely stored more carbon during the last glacial period than during the Holocene.

“This is a significant discovery because it confirms the ocean’s importance as a part of natural climate variability,” said Bradtmiller. “It also tells us what we long thought, [which is] that atmospheric CO2 went into the ocean.”

Bradtmiller was able to document that bottom water in the equatorial Pacific during the glacial period had significantly lower oxygen concentration than during the Holocene, and therefore likely had a correspondingly greater level of respired CO2.

“Our results are consistent with recently published data from the North Pacific Ocean, suggesting that increased carbon storage in the glacial deep Pacific Ocean was a basin-wide phenomenon, consistent with a large-scale transfer of carbon to the deep ocean during glacial periods,” said Bradtmiller.

The other three co-authors were from Columbia University, New York, and the University of Washington, Seattle. Bradtmiller's research was first published in Earth And Planetary Science Letters and was featured in the December 2010 issue of the journal Nature Geoscience.

PUBLISHED: 01/06/2011