Towards radiocarbon dating of ice cores

Skip to search form Skip to main content. Synal and Claude F. Boutron and C. We discuss the potential of this method to achieve a reliable dating using examples from a midand a low-latitude ice core. Two series of samples from Colle Gnifetti ma.

Towards radiocarbon dating of ice cores

A team of scientists has successfully identified the age of ,year-old Antarctic ice using radiometric krypton dating — a new technique that may allow them to locate and date ice that is more than a million years old. The ability to discover ancient ice is critical, the researchers say, because it will allow them to reconstruct the climate much farther back into Earth's history and potentially understand the mechanisms that have triggered the planet to shift into and out of ice ages.

Results of the discovery are being published this week in the Proceedings of the National Academy of Sciences. Krypton dating is much like the more-heralded carbon dating technique that measures the decay of a radioactive isotope — which has constant and well-known decay rates — and compares it to a stable isotope. Unlike carbon, however, krypton is a noble gas that does not interact chemically and is much more stable with a half-life of around , years.

Carbon dating doesn't work well on ice because carbon is produced in the ice itself by cosmic rays and only goes back some 50, years. Krypton is produced by cosmic rays bombarding the Earth and then stored in air bubbles trapped within Antarctic ice. It has a radioactive isotope krypton that decays very slowly, and a stable isotope krypton that does not decay. Comparing the proportion of stable-to-radioactive isotopes provides the age of the ice.

Though scientists have been interested in radiokrypton dating for more than four decades, krypton atoms are so limited and difficult to count that it wasn't until a breakthrough in detector technology that krypton dating became feasible for this kind of research. In their experiment at Taylor Glacier in Antarctica, the researchers put several kilogram about pounds chunks of ice into a container and melted it to release the air from the bubbles, which was then stored in flasks.

The krypton was isolated from the air at the University of Bern, Switzerland, and sent to Argonne for krypton counting. That's why we need such large samples to melt down. The group at Argonne is continually improving the ATTA detector, researchers there say, and they aim to perform analysis on an ice sample as small as 20 kilograms in the near future. The researchers determined from the isotope ratio that the Taylor Glacier samples were , years old, and validated the estimate by comparing the results to well-dated ice core measurements of atmospheric methane and oxygen from that same period.

Now the challenge is to locate some of the oldest ice in Antarctica, which may not be as easy as it sounds. There also are special regions where old ice is exposed at the edges of an ice field, Brook pointed out. Scientists use a pulley system to load kilogram pound ice cores into the melter setup. They are wearing special suits to minimize contamination of the samples. Vasilii Petrenko "The international scientific community is really interested in exploring for old ice in both types of places and this new dating will really help," Brook said.

Some have been on Earth for a million years or more, so the ice in these spots may be that old as well. Buizert said reconstructing the Earth's climate back to 1. The Earth is thought to have shifted in and out of ice ages every , years or so during the past , years, but there is evidence that such a shift took place every 40, years prior to that time. That is one reason we are so anxious to find ice that will take us back further in time so we can further extend data on past carbon dioxide levels and test this hypothesis.

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Home Earth Earth Sciences. April 21, The field camp is visible in the background. Xavier Fain. Schematic layout of the ATTA apparatus used in the krypton analysis. The right side of the setup shows the magneto-optical trap where individual atoms are captured using laser beams and detected using a sensitive CCD camera. Argonne Laboratory. This is the sampling trench for dust studies on Taylor Glacier. Windblown dust from local sources contaminates the upper ice layers and uncontaminated samples are obtained from a meter below the glacier's surface.

Hinrich Schaefer. Vasilii Petrenko. Explore further. More information: Proceedings of the National Academy of Sciences. Provided by Oregon State University. Krypton used to accurately date ancient Antarctic ice , April 21 retrieved 5 May from https: This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission.

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PDF | A recently developed dating method for glacier ice, based on the analysis of radiocarbon in carbonaceous aerosol particles, is thoroughly. I know Carbon 14 is one method, but some ice cores go back hundreds of thousands of Uranium has been used to date the Dome C ice core from Antarctica.

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Record-shattering 2.7-million-year-old ice core reveals start of the ice ages

Author contributions: Ice outcrops provide accessible archives of old ice but are difficult to date reliably. Here we demonstrate 81 Kr radiometric dating of ice, allowing accurate dating of up to 1. The technique successfully identifies valuable ice from the previous interglacial period at Taylor Glacier, Antarctica. Our method will enhance the scientific value of outcropping sites as archives of old ice needed for paleoclimatic reconstructions and can aid efforts to extend the ice core record further back in time. We present successful 81 Kr-Kr radiometric dating of ancient polar ice.

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An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper, and an ice core contains ice formed over a range of years. Cores are drilled with hand augers for shallow holes or powered drills; they can reach depths of over two miles 3. The physical properties of the ice and of material trapped in it can be used to reconstruct the climate over the age range of the core. The proportions of different oxygen and hydrogen isotopes provide information about ancient temperatures , and the air trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such as carbon dioxide. Since heat flow in a large ice sheet is very slow, the borehole temperature is another indicator of temperature in the past. These data can be combined to find the climate model that best fits all the available data. Impurities in ice cores may depend on location.

I was wondering how ice cores are dated accurately.

Guest commentary from Jonny McAneney. You heard it here first ….

How are ice cores dated?

A team of scientists has successfully identified the age of ,year-old Antarctic ice using radiometric krypton dating — a new technique that may allow them to locate and date ice that is more than a million years old. The ability to discover ancient ice is critical, the researchers say, because it will allow them to reconstruct the climate much farther back into Earth's history and potentially understand the mechanisms that have triggered the planet to shift into and out of ice ages. Results of the discovery are being published this week in the Proceedings of the National Academy of Sciences. Krypton dating is much like the more-heralded carbon dating technique that measures the decay of a radioactive isotope — which has constant and well-known decay rates — and compares it to a stable isotope. Unlike carbon, however, krypton is a noble gas that does not interact chemically and is much more stable with a half-life of around , years. Carbon dating doesn't work well on ice because carbon is produced in the ice itself by cosmic rays and only goes back some 50, years. Krypton is produced by cosmic rays bombarding the Earth and then stored in air bubbles trapped within Antarctic ice. It has a radioactive isotope krypton that decays very slowly, and a stable isotope krypton that does not decay. Comparing the proportion of stable-to-radioactive isotopes provides the age of the ice. Though scientists have been interested in radiokrypton dating for more than four decades, krypton atoms are so limited and difficult to count that it wasn't until a breakthrough in detector technology that krypton dating became feasible for this kind of research. In their experiment at Taylor Glacier in Antarctica, the researchers put several kilogram about pounds chunks of ice into a container and melted it to release the air from the bubbles, which was then stored in flasks. The krypton was isolated from the air at the University of Bern, Switzerland, and sent to Argonne for krypton counting.

Towards radiocarbon dating of ice cores

Ice cores from Greenland contain information about climate changes in the past over the Greenland ice sheet and the surrounding areas. Likewise, cores drilled from the sea bed or from the sediments in a lake tell about past temperatures and other climate indicators in the oceans and over continents. The different cores all give their story of the climate of the past from their respective geographical locations, and they agree on one thing: Climate has always been changing. On millennial time scales, the climate oscillates between cold and warm periods. However, one question which is still under investigation is to what degree the climate oscillates in phase all over the Earth or whether there are regional differences during climate shifts. Solving this question is hampered by the uncertainty on the dating of the different records.

When archaeologists want to learn about the history of an ancient civilization, they dig deeply into the soil, searching for tools and artifacts to complete the story. The samples they collect from the ice, called ice cores, hold a record of what our planet was like hundreds of thousands of years ago. But where do ice cores come from, and what do they tell us about climate change? In some areas, these layers result in ice sheets that are several miles several kilometers thick. Researchers drill ice cores from deep sometimes more than a mile, or more than 1.

An analysis has been completed of the global carbon cycle and climate for a 70, year period in the most recent Ice Age, showing a remarkable correlation between carbon dioxide levels and surprisingly abrupt changes in climate. The findings, just published in the online edition of the journal Science, shed further light on the fluctuations in greenhouse gases and climate in Earth's past, and appear to confirm the validity of the types of computer models that are used to project a warmer climate in the future, researchers said. The analysis was made by studying the levels of carbon dioxide and other trace gases trapped as bubbles in ancient ice cores from Antarctica. In the last Ice Age, as during most of Earth's history, levels of carbon dioxide and climate change are intimately linked. Carbon dioxide tends to rise when climate warms, and the higher levels of carbon dioxide magnify the warming, Brook said. These natural cycles provide a "fingerprint" of how the carbon cycle responds to climate change. In contrast to the relatively low levels of carbon dioxide in the Ice Age, the burning of fossil fuels since the Industrial Revolution has led to levels of greenhouse gases that by comparison are off the charts. The level of atmospheric carbon dioxide today is about parts per million, or more than double that of some of the lower levels during the Ice Age.

Scientists endured bitter winds to retrieve ancient ice from a blue ice field in the Allan Hills of Antarctica. Scientists announced today that a core drilled in Antarctica has yielded 2. Some models of ancient climate predict that such relatively low levels would be needed to tip Earth into a series of ice ages. But some proxies gleaned from the fossils of animals that lived in shallow oceans had indicated higher CO 2 levels. Although blue ice areas offer only a fragmentary view of the past, they may turn into prime hunting grounds for ancient ice, says Ed Brook, a geochemist on the discovery team at Oregon State University in Corvallis. Ice cores from Greenland and Antarctica are mainstays of modern climate science.

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