A new study conducted by University of Cambridge researchers reconstructed the conditions that occurred at the end of the last ice age and concluded that massive amounts of carbon dioxide (CO2) were released into the atmosphere due to the melting of the Antarctic sea ice that harbored the molecules. The study marks the first in-depth reconstruction of the South Ocean density of the time period and identification of how it was altered by the warming of the Earth. Furthermore, the results suggest that the ocean's temperature and salinity underwent a massive reorganization, although this was not what stimulated the increased atmospheric CO2 levels.
Previously, scientists believed that the massive amounts of CO2 released into the atmosphere during the last ice age was the result of dense saltwater that harbored the compound decreasing in density, leading to its release. However, the new findings suggest that the decreased density of saltwater happened much later than the rising atmospheric CO2 levels.
"We set out to test the idea that a decrease in ocean density resulted in a rise in CO2 by reconstructing how it changed across time periods when the Earth was warming," Jenny Roberts, lead author of the study, said in a press release. "However what we found was not what we were expecting to see."
"Before this study there were these two observations, the first was that glacial deep water was really salty and dense, and the second that it also contained a lot of CO2, and the community put two and two together and said these two observations must be linked," Roberts explained. "But it was only through doing our study, and looking at the change in both density and CO2 across the deglaciation, that we found they actually weren't linked. This surprised us all."
The researchers examined the chemical composition of microscopic shelled animals that were buried deep into the ocean at the end of the ice age in order to uncover clues that would help them solve the mystery. The findings pointed to the melting of Antarctic sea ice, which normally prevented CO2-rich water from the Southern Ocean from releasing its CO2.
The findings were published in the Nov. 17 issue of the Proceedings of the National Academy of Sciences.
