Ice of the Quelccaya ice cap with its typical stratification. Credit: Photo by Lonnie Thompson, Courtesy of Ohio State University.
Reading aloud Ice near the equator - that only exists in very few places. With over 40 square kilometers of extension, the Quelccaya ice cap is the largest tropical ice field in the world. It is located in the Peruvian Andes, about 5, 470 meters above sea level. In the ice, clearly defined layers have formed, which correspond to years like the rings of a tree. A team led by researcher couple Lonnie Thompson and Ellen Mosley-Thompson from Ohio State University, Columbus, has funded drilling cores from this ice archive that reflect unprecedented levels of tropical climate history over the past 1, 800 years. The cores had already been won by the team in 2003. Now, analyzes revealed exciting matches to the chemical composition of certain layers of ice cores that the team had won on expeditions in the Himalayas. Thus, the new analysis results could be used to "read" data from other tropical ice samples, the researchers say. The drilling cores of the Quelccaya ice cap could thus become a kind of "Rosetta Stone" in the history of climate - based on the Egyptian inscription stone, which presented a text in hieroglyphics and ancient Greek and demotic and thus significantly contributed to the translation of the Egyptian hieroglyphics.

1, 800 years are reflected in tree-ring-like structures

The characteristic layers in the ice of the quelccaya cap are defined by light and dark sections. The white part is formed in the annual rainy season, when there is a lot of snowfall, while the dark part is created in the dry season, when the dust that has accumulated on the ice surfaces accumulates. The ice samples are also so interesting because the Quelccaya cap is in the sphere of influence of two regions, the researchers say. Most precipitation comes from the east and comes from the humid air that rises from the Amazon basin. But also the influence of the western Pacific is clearly reflected in the ice. Above all, the well-known climate phenomenon "El Niño" is noticeable, which is characterized by changing currents and temperature conditions in the system of the equatorial Pacific.

In 1983, the research team had already sampled from the ice of the Quelccaya cap. But the remoteness of the place and the equipment at that time had not been possible to preserve the cores. The next road was a two-day hike from the ice cap, so the researchers were forced to melt the ice cores locally and take them as liquid samples. This made detailed investigations impossible. "We knew that the ice offered much more information, " says Mosley-Thompson. During the re-sampling in 2003, the conditions had changed significantly: Now the ice cap is only six hours away on foot from a new access road. Here was a truck with a freezer system, picking up the precious ice cores for later investigation. display

The rehearsals now give researchers the opportunity to decipher the history of the climate in the past, gaining a better understanding of the climatic changes that are shaping our planet in the context of climate change today. According to the researchers, the current warm season is also clearly reflected in the state of the Quelccaya ice cap: it has reached the lowest level of the last 6, 000 years.

Lonnie Thompson (Ohio State University, Columbus) et al .: Science, doi: 10.1111 / j.1600-0706.2012.00005.x © science.de - Martin Vieweg

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