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Science

Ice Age Melting Caused by CO2 Release

A recent study has shown that a large release of CO2 could in fact speed up the melting following an ice age.

Authored by Tom Guilderson from the Lawrence Livermore National Laboratory Center for Accelerator Mass Spectrometry, the study used radiocarbon dating to trace the pathway of carbon dioxide released from the deep ocean into the atmosphere at the end of the last ice age, and found that a rapid increase in atmospheric CO2 concentrations coincided with a reduced radiocarbon in the atmosphere (carbon-14 and carbon-12).

“This suggests that there was a release of very ‘old’ or low 14/12CO₂ from the deep ocean to the atmosphere during the end of the last ice age,” said Guilderson.

According to the LLNL, Radiocarbon in the atmosphere is regulated largely by ocean circulation, which controls the sequestration of CO₂ in the deep sea through atmosphere-ocean carbon exchange. During the last ice age (approximately 110,000 to 10,000 years ago), lower atmospheric CO₂ levels were accompanied by increased atmospheric radiocarbon concentrations that have been credited to greater storage of CO₂ in a poorly ventilated abyssal ocean.

“The ocean circulation was significantly different than it is today and carbon was being stored in the deep ocean in a manner that we don’t completely understand,” Guilderson said.

Guilderson and colleagues used two sediment cores from near New Zealand and dated them to be between 13,000 and 19,000 years old. They were able to determine not only when the large CO2 release occurred but the ocean pathway by which it escaped.

“In this case, the absence of a signal is telling us something important,” Guilderson said. “Deeper waters substantially depleted in carbon-14 were drawn to the upper layers and this is the main source of the CO₂ during deglaciation. Data suggests that the upwelling of this water occurred in the Southern Ocean, near Antarctica. In our cores off New Zealand, which lie in the path of waters which ‘turn over’ in the Southern Ocean, we don’t find anomalously low carbon-14/12 ratios.

“This implies that either water which upwelled in the Southern Ocean, after 16,500 years ago,” Guilderson continued, “had a vigorous exchange with the atmosphere, allowing its 14C-clock to be reset, or the circulation was significantly different than what the current paradigm is. If the paradigm is wrong, then during the glacial and deglaciation, the North Pacific is much more important than we give it credit for.”

Source: Lawrence Livermore National Laboratory




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