The carbon in the ground led to warming during the final days of the last ice age.
As the last ice age came to an end, the carbon dioxide in the air caused a general rise in temperature levels. Researchers have tried to prove that the source of this carbon dioxide was the carbon in the deep ocean around Antarctica.
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This has been a point that is difficult to prove without an iota of doubt. A new study was published in the journal Proceedings of the National Academy of Sciences recently. It showed that while atmospheric carbon dioxide did play a role in the global warming, carbon found in land also played a pivotal role.
These land-based carbon stores were to be found in the Antarctic ice sheets. When they got thawed from their frozen state, they released the carbon dioxide into the atmosphere.
"There wasn't a steady rate of rising carbon dioxide during the last deglaciation," said Edward Brook, an Oregon State University paleoclimatologist and co-author on the PNAS study.
"It happened in fits and starts. With the new precise techniques we developed to fingerprint the sources, it is apparent that the early carbon largely came from the ocean, but we think the system got a jolt from an influx of land-based carbon a few times as the climate warmed."
Basically, the last deglaciation period was all about the release of carbon dioxide into the surrounding climate. The carbon dioxide was released in abrupt spurts. It did not take place in a fixed or steady state manner.
While the latest techniques of analysis show that ocean-based carbon was responsible for this state of affairs in the past, land-based carbon too played a significant role.
Carbon isotope ratios were measured in the pure samples of ice from the Taylor Glacier in Antarctica. Even though such techniques have been applied in the past, this time around further fine tuning in the lab led to results that were detailed and extraordinarily accurate.
During the early rise in carbon dioxide levels from 17,600 to 15,500 years ago, the relatively light isotope 12-C increased at a faster rate than heavier isotopes.
Then in between that time, the carbon ratio abruptly began to double and triple. This rapid rise was a surprising find. It showed that carbon was being released from the soil and plant life.
Although the exact area from which the carbon dioxide was being released could not be pinpointed, the tropics were suspected. That is because the methane from tropical swamps may have played a big role in the carbon release.
Also a deluge of icebergs from the northern Arctic region could have been responsible for this phenomenon. Among the places that had swamps were such regions as Brazil and China.
"One theory," Brooks said, "is that an influx of icebergs in the Northern Hemisphere at about 16,300 years ago -- from retreating ice sheets -- cooled the North Atlantic Ocean and pushed the tropical rain belt southward over Brazil, expanding the wetlands. Swamps in the Southern Hemisphere, in places like Brazil, may have become wetter and produced methane, while plants and soils in the Northern Hemisphere, in places like China, may have been hit by drought and produced CO2."
During the next 4000 years, the continual rise in CO2 levels probably led to changes in the C-13 and C-12 ratio. There were thus more sources of carbon than was previously thought. The isotope ratio technique is ideal for such cases. It lends us a glimpse into the past.
"The rise of CO2 is a complicated beast, with different behaviors triggered at different times," Mix said.
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"Although the natural changes at the end of the ice age are not a direct analogy for the future, the rapid changes do provide a cautionary tale. Manmade warming from CO2 pollution may trigger further release from 'natural sources,' and this could exacerbate greenhouse gases and warming."