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Friday, April 5, 2013

Peruvian Ice Cores Reveal Climate History: 1,600 Years Of Ice Melted In 25 Years

Ice Wall
(Photo : Flickr/Dominic Alves) Two ice cores from the Andes have revealed the climate history of our planet; the researchers have found that ice that took 1,600 years to form melted in a mere 25 years.

Apr 05, 2013

There's more evidence for global warming--and it's some of the most compelling yet. Two annually dated ice cores from the Peruvian Andes have revealed the climate history of our planet.
When researchers retrieved the cores from the Peruvian ice cap in 2003, they noticed quite a few similarities to other ice cores that they had retrieved from Tibet and the Himalayas. In particular, patterns in the chemical composition of certain layers matched up, even though the cores were taken from different sides of the planet. In fact, it turned out that the cores allowed the researchers to compare climate histories from Earth's tropical and subtropical regions over the last two millennia. They detailed their findings in a paper published in the journal Science Express.
"These ice cores provide the longest and highest-resolution tropical ice core to date," said Lonnie Thompson, lead author of the study, in a press release. "In fact, having drilled ice cores throughout the tropics for more than 30 years, we now know that this is the highest-resolution tropical ice core record that is likely to be retrieved."
The two ice cores come from Peru's Quelccaya Ice Cap and possess a 1,800 year history defined in light and dark layers which reveal years and seasons--think of the rings on a tree. The light layers represent periods where snow accumulated while the dark layers represent accumulated dust from the dry season. In addition, chemicals founds in the ice have allowed the researchers to even derive a proxy for sea surface temperatures long before scientists were able to make such measurements.
The ice cores could provide some of the best evidence of what Earth's climate was like centuries ago. That said, the ice cores aren't the only thing that the researchers focused on. Since the Quelccaya Ice Cap is the smallest it has been in 6,000 years, the scientists were able to collect plants that have been revealed as the ice retreats. They have already dated these plants using a radioactive form of carbon in the plant tissue that decays at a known rate. Surprisingly, they found that the glacial ice that took at least 1,600 years to form has melted in a mere 25 years.
In order to preserve the valuable ice cores, the researchers have now placed them in freezers so that they will be available for future use.

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Climate Science Discovers Its Own Rosetta Stone

The Rosetta Stone was one of the most important archaeological discoveries ever made, when in 1799 it was discovered by Pierre-François Bouchard, of the French expedition to Egypt. Inscribed on the stone was a decree written in three separate scripts – Ancient Egyptian hieroglyphs, Demotic script, and Ancient Greek – which allowed modern archaeologists the opportunity to finally decipher Ancient Egyptian hieroglyphs. Now, thanks to a 2003 discovery in the Peruvian Andes, climate scientists have for the first time a ‘Rosetta Stone’ of their own in the form of two dated ice cores that go back nearly 1,800 years which reveal Earth’s tropical climate history in unprecedented detail. Researchers from the Ohio State University retrieved the cores from a Peruvian ice cap in 2003, drilled from Peru’s Quelccaya Ice Cap. The cores reveal clearly defined layers of light and dark: the light layers depicting accumulated snow from the wet season and the dark layers representing accumulated dust from the dry seasons.
What is arguably most intriguing about this discovery is the similarity with ice cores taken across the globe from Tibet and the Himalayas which contain similar patterns in the chemical composition of certain layers.
“These ice cores provide the longest and highest-resolution tropical ice core record to date,” said Lonnie Thompson, distinguished university professor of earth sciences at Ohio State and lead author of the study. “In fact, having drilled ice cores throughout the tropics for more than 30 years, we now know that this is the highest-resolution tropical ice core record that is likely to be retrieved.”
climate rosetta stone Climate Science Discovers Its Own Rosetta Stone
These photos of Quelccaya Ice Cap in Peru, taken from the same spot in 1977 (left) and 2002 (right) show the retreat of the ice cap’s vertical margins. The 1977 image shows the annually deposited layers of ice and dust that make ice cores drilled from the site especially useful to scientists. Image Credit – Lonnie Thompson, courtesy of Ohio State University
Furthermore, the ice cores are doubly beneficial for climate scientists given the location from which they were extracted. Taken from the high Andean altiplano in southern Peru, which acquires most of its moisture from the east, in the form of snowstorms fuelled by moist air rising from the Amazon Basin, as well as being impacted by climate from the west, specifically by El Niño, a temporary change in climate, which is driven by sea surface temperatures in the tropical Pacific.
El Niño leaves its mark on ice cores taken from the Quelccaya ice cap as a chemical signature which indicates sea surface temperature in the equatorial Pacific Ocean.
“We have been able to derive a proxy for sea surface temperatures that reaches back long before humans were able to make such measurements, and long before humans began to affect Earth’s climate,” Thompson said.
The discovery is a result of 20 years of work by Lonnie Thompson and his wife Ellen Mosley-Thompson, distinguished university professor of geography at Ohio State and director of the Byrd Polar Research Center. They have drilled ice cores from glaciers atop the Chinese Himalayas, the Tibetan Plateau, Kilimanjaro in Africa, and Papua Indonesia among others, and received their first publication in the journal Science back in 1983 by visiting Quelccaya by means of a two-day walk to and from the core-site.


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