Nature & Environment
World's Oldest Ice : Radioactive Krypton Accurately Dates Ancient Antarctic Ice Cores
Benita Matilda
First Posted: Apr 22, 2014 04:41 AM EDT
Scientists have accurately dated ancient Antarctic ice cores that are 120,000 years old.
Researchers at the Oregon State University used a new technology called 'radiometric krypton dating' to identify the age of the world's oldest ice cores. Using the novel technique the researchers found that the ancient Antarctic ice cores are 120,000 years-old.
It is extremely critical to discover ancient ice cores as they help recreate the climate that existed in ancient times. Apart from this, the ice also helps trace the mechanism responsible for the planet's shift into and out of the ice ages.
'Krypton dating' measures the decay of radioactive isotope and compares it to other stable isotope. Being a Nobel gas in nature, Krypton does not mix chemically and is comparatively more stable. For ice, krypton dating is preferred over carbon dating as carbon-14 is a by-product of ice itself formed when cosmic rays bombar the Earth and dates back some 50,000 years whereas krypton is stable with a life of 230,000 years.
Krypton is stored in the form of air bubbles that is trapped in the ice cores. It consists of radioactive isotope (krypton 81) and a stable isotope (krypton 83).
For the past four decades, radiokrypton dating has attracted widespread interest. Krypton-81 is very limited and difficult to count. In order to overcome this barrier, the researchers worked along with scientists at the Argonne National Laboratory (ANL) near Chicago and constructed an instrument that is capable of measuring krypton 81.
Collecting Krypton:
To segregate krypton from the ice chunks, Zheng-Tian Lu at ANL, melted the ice chunks in a container allowing the air from the bubbles to be released, which was later collected in a flasks.
"The atom trap is so sensitive that it can capture and count individual atoms," said Christo Buizert, a postdoctoral researcher at Oregon State University and lead author "The only problem is that there isn't a lot of krypton in the air, and thus there isn't much in the ice, either. That's why we need such large samples to melt down."
Analysis of the samples confirmed that the glacier samples were 120,000 years old by comparing the results with well-dated ice core measurements of methane and oxygen that were found during the same time.
Locating the Oldest Ice:
"Most people assume that it's a question of just drilling deeper for ice cores, but it's not that simple," said Edward Brook, an Oregon State University geologist and co-author on the study. "Very old ice probably exists in small isolated patches at the base of the ice sheet that have not yet been identified, but in many places it has probably melted and flowed out into the ocean."
There are certain areas where the old ice is left open at the edges of ice field. The scientific community is keen to trace the old ice at both the locations using the novel dating technique.
"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 Buizert. "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 finding will be published in the Proceedings of the National Academy of Sciences.
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First Posted: Apr 22, 2014 04:41 AM EDT
Scientists have accurately dated ancient Antarctic ice cores that are 120,000 years old.
Researchers at the Oregon State University used a new technology called 'radiometric krypton dating' to identify the age of the world's oldest ice cores. Using the novel technique the researchers found that the ancient Antarctic ice cores are 120,000 years-old.
It is extremely critical to discover ancient ice cores as they help recreate the climate that existed in ancient times. Apart from this, the ice also helps trace the mechanism responsible for the planet's shift into and out of the ice ages.
'Krypton dating' measures the decay of radioactive isotope and compares it to other stable isotope. Being a Nobel gas in nature, Krypton does not mix chemically and is comparatively more stable. For ice, krypton dating is preferred over carbon dating as carbon-14 is a by-product of ice itself formed when cosmic rays bombar the Earth and dates back some 50,000 years whereas krypton is stable with a life of 230,000 years.
Krypton is stored in the form of air bubbles that is trapped in the ice cores. It consists of radioactive isotope (krypton 81) and a stable isotope (krypton 83).
For the past four decades, radiokrypton dating has attracted widespread interest. Krypton-81 is very limited and difficult to count. In order to overcome this barrier, the researchers worked along with scientists at the Argonne National Laboratory (ANL) near Chicago and constructed an instrument that is capable of measuring krypton 81.
Collecting Krypton:
To segregate krypton from the ice chunks, Zheng-Tian Lu at ANL, melted the ice chunks in a container allowing the air from the bubbles to be released, which was later collected in a flasks.
"The atom trap is so sensitive that it can capture and count individual atoms," said Christo Buizert, a postdoctoral researcher at Oregon State University and lead author "The only problem is that there isn't a lot of krypton in the air, and thus there isn't much in the ice, either. That's why we need such large samples to melt down."
Analysis of the samples confirmed that the glacier samples were 120,000 years old by comparing the results with well-dated ice core measurements of methane and oxygen that were found during the same time.
Locating the Oldest Ice:
"Most people assume that it's a question of just drilling deeper for ice cores, but it's not that simple," said Edward Brook, an Oregon State University geologist and co-author on the study. "Very old ice probably exists in small isolated patches at the base of the ice sheet that have not yet been identified, but in many places it has probably melted and flowed out into the ocean."
There are certain areas where the old ice is left open at the edges of ice field. The scientific community is keen to trace the old ice at both the locations using the novel dating technique.
"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 Buizert. "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 finding will be published in the Proceedings of the National Academy of Sciences.
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone