Impurities in ice cores may depend on location; for example, coastal areas are more likely to include material of marine origin, such as sea salt ions.
Keep up with this story and more Scientists have tried to develop the krypton dating technique for more than four decades.In 2011, a team of nuclear physicists at the Argonne National Laboratory in Lemont, Ill., near Chicago developed a new atom counter, the Atom Trap Trace Analysis, which finally made the technique possible.The ratio of oxygen and hydrogen isotopes in the ice provides information about ancient temperatures; and the air trapped in tiny bubbles in the ice can be analyzed 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, and these sources of information can be combined to find the climate model that best fits all the available data."The oldest ice found in drilled cores is around 800,000 years old and with this new technique we think we can look in other regions and successfully date polar ice back as far as 1.5 million years," said Christo Buizert, a postdoctoral researcher at Oregon State University and lead author on the PNAS article. Through Polar Programs, NSF manages the United States Antarctic Program, which coordinates all U. research on the southernmost continent and the logistical support for the science.
"That is very exciting because a lot of interesting things happened with the Earth's climate prior to 800,000 years ago that we currently cannot study in the ice-core record."The work was supported by two collaborative awards 08389031 made by the Division of Polar Programs in NSF's Geosciences Directorate and by the U. Buizert, whose work also was supported in part by the National Oceanic and Atmospheric Administration, said reconstructing the Earth's climate back to 1.5 million years is important because a shift in the frequency of ice ages took place in what is known as the Middle Pleistocene transition.
Cores are recovered by drilling with hand augers (for shallow holes) or powered drills; the deepest cores recovered reach depths of over two miles, and can contain ice up to 800,000 years old.
Both the physical properties of the ice itself and material trapped in the ice can be used to reconstruct information about climate over the age range of the core.
An ice core is a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica or Greenland or from high mountain glaciers elsewhere.
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.
By studying the past climate, scientists can better understand the effects that greenhouse gas concentrations in the atmosphere have on temperatures — and can then make more accurate predictions about how the climate will change in the future. Krypton dating is much like the carbon-14 dating technique that measures the decay of a radioactive isotope.