A team of scientists from the University of Pennsylvania has published a new report in the journal Scientific Reports, detailing the fact that the East Antarctic Ice Sheet (EAIS) has remained frozen for a little over 14 million years, and a thorough analysis of ancient lake deposits beneath the ice sheet give credence to this fact.
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The team was composed of Jane K. Willenbring, an assistant professor in the Department of Earth and Environmental Science in Penn's School of Arts and Sciences, lead author and Penn graduate student Rachel D. Valletta, Adam R. Lewis, and Allan C. Ashworth from the University of North Dakota, as well as Marc Caffee from Purdue University.
The team figured that Antarctica must have once hosted lakes and plants before it went barren in response to climate changes and peaked carbon-dioxide levels.
Since the timeless lake deposits below the East Antarctic Ice Sheet show the EAIS has been frozen for 14 million years, the researchers believe its surrounding region must have equally been frozen for the same period of time. But then, the study shows that the EAIS did not undergo considerable melting during the Pliocene period which existed 3-5 million years ago and when CO2 levels corresponded with what we have today.
"The Pliocene is sometimes thought to be an analog to what Earth will be like if global warming continues," said Jane K. Willenbring. "This gives us some hope that the East Antarctic Ice Sheet could be stable in today's and future climate conditions."
Willenbring and her team visited Antarctica’s Friis Hills in the central Dry Valleys of the eastern part of the continent, to test the actual age of volcanic ash deposits at the bottom of the ancient lake; and then analyzed radioactive isotopes of beryllium-10 which is created in the atmosphere when cosmic rays clash with oxygen and nitrogen atoms.
"Beryllium-10 sticks on to particles quite easily and is associated with lake deposits," Willenbring said. "We wanted to see if we could use this isotope to figure out how long the sediment was in place and isolated from liquid water."
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Since beryllium-10 possesses half-life of 1.4 million years, a measurement of the substance concentrations in lake samples revealed the sediments are between 14 to 17.5 million years old. "This means that the sediment is definitely older than the time when a lot of people think that Antarctica might have been quite deglaciated," Willenbring noted.