2.7-million-year-old ice core pulled from Antarctica

August 21, 2017 by Bob Yirka, Phys.org report
Credit: CC0 Public Domain

A team of researchers from Princeton University, the Scripps Institution of Oceanography, the University of Maine and Oregon State University has drilled and retrieved a 2.7-million-year-old ice core from a spot in Antarctica. The team presented their findings at this year's Goldschmidt Conference in Paris.

Until recently, scientists believed that ice core samples taken from either pole had an age limit of approximately 800,000 years—this was because ice at the bottom melted due to heat from inside the Earth. But a team at Princeton discovered a few year ago that another type of ice could hold much older ice known as . It forms on glaciers due to snowfall which, over time, becomes compressed, squeezing out , making the ice look blue. But it also has another characteristic—over time, the ice at the bottom is pushed upwards, protecting it from melting. In this new effort, the team drilled at a site called the Allan Hills, near McMurdo Station.

Ice cores taken from glaciers present problems because they are more difficult to date—cores from other places are dated by counting their layers. The older ice, it was found, could be dated by studying trace amounts of potassium and argon—though not as precise as layer counting, the researchers believe it is accurate to within 100,000 years. One of the first teams to take a core sample from the older ice drilled to a depth of 128 meters. In this latest effort, the team drilled to 205 meters and found ice that was nearly twice as old.

Ice cores are important because they contain very small air bubbles that are samples of atmospheric conditions. Air bubbles from 2.7 million years ago offer evidence of climactic conditions during the time before the ice ages began, perhaps offering clues as to why they occurred. Already, the team has found that levels were at approximately 300 ppm, which is considerably lower than today's 400 ppm. But the team notes that the core sample represents something perhaps even more exciting—the possibility of finding core samples that are much older, perhaps as old as 5 million years.

Explore further: Ice cores store atmospheric bubbles from a million years ago

More information: Paul Voosen. 2.7-million-year-old ice opens window on past, Science (2017). DOI: 10.1126/science.357.6352.630

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Turgent
1.8 / 5 (5) Aug 21, 2017
An 800,000 year graphic representation of CO2 and the temperature proxy, deuterium, was provided by Science and isn't in Physic.org article. Visually it can't be seen whether temperature is leading or following CO2. They are using potassium-40 decay half-life (1.248x10^9 years) for dating, Being the ice core is 2.7 x 10^6 years in depth it would seem Beryllium-10 could be better time determinant. Be-10 has a half-life of 1.39 × 10^6 years. I wonder why Be-10 wasn't used? It would seem possible that a CO2 lead or lag relative to temp could have been teased out of the data without an unreasonable error?
J Doug
1 / 5 (3) Aug 21, 2017
"Already, the team has found that atmospheric carbon dioxide levels were at approximately 300 ppm, which is considerably lower than today's 400 ppm." Is it too much to hope for the truth from Phys.org?
Trends Over the last 800,000 years atmospheric CO2 levels as indicated by the ice-core data have fluctuated between 170 and 300 parts per million by volume (ppmv), corresponding with conditions of glacial and interglacial periods. The Vostok core indicates very similar trends. Prior to about 450,000 years before present time (BP) atmospheric CO2 levels were always at or below 260 ppmv and reached lowest values, approaching 170 ppmv, between 660,000 and 670,000 years ago. The highest pre-industrial value recorded in 800,000 years of ice-core record was 298.6 ppmv, in the Vostok core, around 330,000 years ago.
http://cdiac.ornl...co2.html
J Doug
1 / 5 (3) Aug 21, 2017
We sure will not hear anything about ikaite on Phys.org because it states that the MWP was planet wide.
Abstract
Calcium carbonate can crystallize in a hydrated form as ikaite at low temperatures. The hydration water in ikaite grown in laboratory experiments records the δ18O of ambient water, a feature potentially useful for reconstructing δ18O of local seawater. We report the first downcore δ18O record of natural ikaite hydration waters and crystals collected from the Antarctic Peninsula (AP), a region sensitive to climate fluctuations. Having constrained the depth of ikaite formation and δ18O of ikaite crystals and hydration waters, we are able to infer local changes in fjord δ18O versus time during the late Holocene. This ikaite record qualitatively supports that both the Medieval Warm Period and Little Ice Age extended to the Antarctic Peninsula.
http://www.scienc...12000659

Ojorf
5 / 5 (4) Aug 21, 2017
So it's a conspiracy and Phys.org is in on it?

Ooohhh Kaaayy....
rrrander
not rated yet Aug 22, 2017
Why is there 2.7M year old ice at all? Shouldn't it all have melted?

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