Dating ice cores
To support our nonprofit science journalism, please make a tax-deductible gift today. 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.
SEE VIDEO BY TOPIC: Studying Ice Cores to Understand the Earth's ClimateContent:
- How are ice cores dated?
- Australian Antarctic Division: Leading Australia’s Antarctic Program
- Ice Cores and the Age of the Earth
- Using krypton gas to date the age of ancient ice cores
- Record-shattering 2.7-million-year-old ice core reveals start of the ice ages
- Core questions: An introduction to ice cores
How are ice cores dated?
Krypton is a noble gas that is present in the atmosphere at extremely low levels, or about one part per million. In the upper atmosphere, exposure to cosmic rays can transform a stable krypton isotope into a slow-decaying radioactive isotope. Scientists say that air bubbles in polar ice will contain some of these radioisotopes. Also, you need a device that can count, or trap, individual atoms. Fortunately, such a device was developed in by a team of nuclear physicists at Argonne National Laboratory in Illinois.
To test the atom trap on ancient ice, study authors obtained more than pounds of ice chunks from Taylor Glacier, Antarctica, melted them down, trapped the escaped air in flasks and had it analyzed. Scientists say they hope that as the dating method is refined, they can work with smaller amounts of ice. Sign up for the latest news, best stories and what they mean for you, plus answers to your questions. Hot Property. About Us. Brand Publishing. Times News Platforms. Times Store.
Facebook Twitter Show more sharing options Share Close extra sharing options. In this time-lapse video, scientists in Antarctica melt ice core samples from the Taylor Glacier. April 21, Sign Me Up. You may occasionally receive promotional content from the Los Angeles Times.
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Australian Antarctic Division: Leading Australia’s Antarctic Program
I was wondering how ice cores are dated accurately. I know Carbon 14 is one method, but some ice cores go back hundreds of thousands of years. Would other isotopes with longer half-lives be more accurate? Also, how much does it cost to date the core?
The researchers often rely on events like volcanic eruptions to determine how old the ice is. And a very good thing is volcanic eruptions. When you have a volcano erupting you have ash for example in the atmosphere. And this ash layer can travel around the globe, and then also is deposited in Antarctic ice cores. So you might be able to see a kind of darkish layer in an ice core and then you know exactly when this volcanic eruption was, and that is how you date your ice.
Ice Cores and the Age of the Earth
Ice consists of water molecules made of atoms that come in versions with slightly different mass, so-called isotopes. Variations in the abundance of the heavy isotopes relative to the most common isotopes can be measured and are found to reflect the temperature variations through the year. The graph below shows how the isotopes correlate with the local temperature over a few years in the early s at the GRIP drill site:. The dashed lines indicate the winter layers and define the annual layers. How far back in time the annual layers can be identified depends on the thickness of the layers, which again depends on the amount of annual snowfall, the accumulation, and how deep the layers have moved into the ice sheet. As the ice layers get older, the isotopes slowly move around and gradually weaken the annual signal. Read more about - diffusion of stable isotopes - how the DYE-3 ice core has been dated using stable isotope data - how stable isotope measurements are performed - stable isotopes as indicators of past temperatures - how annual layers are identified using impurity data. Move the mouse over individual words to see a short explanation of the word or click on the word to go to the relevant page. For more information on the topic please contact Bo Vinther.
Using krypton gas to date the age of ancient ice cores
It is not uncommon to read that ice cores from the polar regions contain records of climatic change from the distant past. Research teams from the United States, the Soviet Union, Denmark, and France have bored holes over a mile deep into the ice near the poles and removed samples for analysis in their laboratories. Based on flow models, the variation of oxygen isotopes, the concentration of carbon dioxide in trapped air bubbles, the presence of oxygen isotopes, acid concentrations, and particulates, they believe the lowest layers of the ice sheets were laid down over , years ago. Annual oscillations of such quantities are often evident in the record.
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.
Record-shattering 2.7-million-year-old ice core reveals start of the ice ages
Based on an early Greenland ice core record produced back in , versions of the graph have, variously, mislabeled the x-axis, excluded the modern observational temperature record and conflated a single location in Greenland with the whole world. More recently, researchers have drilled numerous additional ice cores throughout Greenland and produced an updated estimate past Greenland temperatures. This modern temperature reconstruction, combined with observational records over the past century, shows that current temperatures in Greenland are warmer than any period in the past 2, years. However, warming is expected to continue in the future as human actions continue to emit greenhouse gases, primarily from the combustion of fossil fuels.
A variety of methods are used to date an ice core. The most direct method is to count annual layers in much the same way that tree-rings can be counted to determine the age of the tree. However, the layers in ice cores are not generally visible in the ice. They only become apparent when the core is analysed for a chemical signal that varies with the seasons, which most signals do, to some extent. In fact the clearest dating is obtained when several seasonal signals are examined and compared.
Core questions: An introduction to ice cores
The measurements on the ice from the ice core have little or no scientific value if they cannot be related to a specific time or time period. It is therefore one of the most important tasks before and after an ice core has been drilled to establish a time scale for the ice core. Dating of ice cores is done using a combination of annual layer counting and computer modelling. Ice core time scales can be applied to other ice cores or even to other archives of past climate using common horizons in the archives. Annual layers in the ice can be counted like annual rings in a tree.
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