Professor Ed Brook of Oregon State University holding 2 million-year-old ice. Credit: University of Oregon State
Recently discovered by a team of researchers, two million-year-old Antarctic ice gives a clearer picture of the interactions between greenhouse gasses and climate in ancient times and will help scientists recognize future climate change.
A paper published today in Nature, used air trapped in ice bubbles as old as 2 million years to measure carbon dioxide and methane levels of greenhouse gases.
That group was led by Princeton University’s John Higgins and Yuzhen Yan and University of Maine’s Andrei Kurbatov, including Ed Brook at Oregon State University and Jeff Severinghaus at San Diego University.
This is the first time that scientists have been able to study that old ice ice core. Previously, data were provided back to 800,000 years by the oldest total ice core.
Past studies using that core and others have shown that the levels of atmospheric carbon dioxide over the past 800,000 years have been directly related to the Antarctic and global temperature. Before that, it was not as well known the relation between climate and carbon dioxide levels.
The cycle of ice ages followed by warm periods has occurred every 100,000 years over the past one million years. But these cycles were shorter, about 40,000 years, between 2.8 million years ago and 1.2 million years ago, and ice ages were less extreme.

Professor Ed Brook of Oregon State University holds 2 million-year-old ice.
The group that included Brook wanted to find out how the rates of carbon dioxide differed during that older period of time, which until now had only been understood indirectly from the ocean and land sediment chemistry.
They found that the highest carbon dioxide levels matched the levels of more recent times in warm periods. Moreover, the lowest concentrations identified in the ice ages of the last 800,000 years did not reach the very low concentrations.
“One of the important results of this study is to show that carbon dioxide is linked to temperature in this earlier time period,” said Brook.
This conclusion is based on ice chemistry experiments that provide an indication of temperature change in Antarctica at the same time as the changes in carbon dioxide. “That’s an important baseline for understanding climate science and calibrating models that predict future change,” Brook said.
The 2 million-year-old ice core comes from an area known as Allan Hills, some 130 miles from the U.S. Research station in the Antarctic, known as McMurdo Station. In this region, ancient meteorites were found on the surface, leading scientists to conclude that the ice sheet may contain ancient ice. During the 2015-16 field season, the center with the 2 million-year-old ice was drilled at a depth of 200 meters. Drilling and retrieving such a core takes one to two weeks, and several cores have been collected in the region.
For two months of additional work, the research team is on its way back to Allan Hills in the days ahead. We will obtain larger quantities of the ice that is 2 million years old and search for even older specimens. “We don’t know the age limit in this area,” Brook added, “It could be much older in some places. That’s why we’re going back. Pushing beyond two million years would be pretty amazing”.


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