Cores Reveal Climate History: 1,600 Years of Ice Melted in 25 Years in Andes

First Posted: Apr 05, 2013 10:54 AM EDT

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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