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In 2011, the @NSF-funded WAIS Divide ice core reached a depth of 3400 meters beneath the West Antarctic ice sheet and recovered a 68,000-year archive of earth’s atmosphere and climate. This is the now complete record of atmospheric CO₂ from the core.
w/ @osu_ice @ShaunMarcott
w/ @osu_ice @ShaunMarcott
Here is a free link to the paper in @NatureGeosci :
https://rdcu.be/ceLUC
And the data:
https://www.ncdc.noaa.gov/paleo-search/study/31772
https://rdcu.be/ceLUC
And the data:
https://www.ncdc.noaa.gov/paleo-search/study/31772
Previously, we had seen that gradual changes in CO₂ can occasional be punctuated by rapid, yet modest (<15 ppm) jumps within a few centuries or less. Our evidence was mostly limited to the last deglaciation and short sections in the last glacial period.
Were these changes rarities or regular features of the carbon cycle?
By extending the record into the last glacial period, we can now see that the rapid changes are pervasive with a consistent pattern.
By extending the record into the last glacial period, we can now see that the rapid changes are pervasive with a consistent pattern.
Whenever Greenland warms and CH₄ rapidly rises (the onset of an interstadial), CO₂ rises. Whenever CH₄ rises without a clear change in Greenland (within a Heinrich stadial), CO₂ also rises, very quickly.
How do these “abrupt” changes compare to the anthropogenic rise in CO₂?
They are fast for natural changes, but stand in stark contrast to today. Even the fastest change (~15 ppm over century) would be overshadowed within 6 years at present rates (2.5 ppm per year).
They are fast for natural changes, but stand in stark contrast to today. Even the fastest change (~15 ppm over century) would be overshadowed within 6 years at present rates (2.5 ppm per year).
So why do we care?
Even though the changes might be small compared current rates, they are telling us that natural sources of CO₂ to the atmosphere can turn on suddenly within a few centuries.
Even though the changes might be small compared current rates, they are telling us that natural sources of CO₂ to the atmosphere can turn on suddenly within a few centuries.
What are these sources?
We can’t be sure, but we point to a warmer, better-ventilated, Atlantic basin as a likely source of CO₂ at onset of interstadials. But terrestrial sources may also play a roll through feedbacks in the parts of the Northern Hemisphere that warm.
We can’t be sure, but we point to a warmer, better-ventilated, Atlantic basin as a likely source of CO₂ at onset of interstadials. But terrestrial sources may also play a roll through feedbacks in the parts of the Northern Hemisphere that warm.
For the sources of CO₂ during Heinrich stadials, my money is still on terrestrial sources but hopefully this new dataset will provide better fodder for the models.
What are the implications for the future?
They’re not exactly clear. One could be cautiously optimistic and say that fast changes we see are very small compared to today and therefore we are unlikely to see any major “surprises”.
They’re not exactly clear. One could be cautiously optimistic and say that fast changes we see are very small compared to today and therefore we are unlikely to see any major “surprises”.
Yet we know that carbon cycle models struggle to capture all the modes of natural carbon cycle variability and need improvement. We also know the earth’s climate and carbon cycle during the last glacial period was in a fundamentally different than today.
There was more carbon stored in the deep ocean and (probably) less carbon stored on land in the boreal regions having been replaced or over-ridden by ice sheets, so some of the feedbacks we may see in the future wouldn’t have been as active in the past.
Thank you @NSF OPP for funding this and all the great WAIS Divide projects. Thanks also to the @royalsociety for funding my fellowship to work on this topic.
