Patagonia was completely covered in ice for much of the last 140 thousand years

Patagonia was completely covered in ice for much of the last 140 thousand years
Patagonia was completely covered in ice for much of the last 140 thousand years

Recently, the journal Proceedings of the National Academy of Sciences, edited by the National Academy of Sciences of the United States, published the article “A marine record of Patagonian ice sheet changes over the past 140,000 years” or “A marine record of the changes in the Patagonian cap during the last 140,000 years” in Spanish, in which Dr. Carina Lange, researcher at the COPAS Coastal center, participates along with researchers from Germany, Japan, the United States and the United Kingdom.

The study is based on the analysis of biomarkers preserved in sediments to reconstruct the climatic variations that the west coast of central Patagonia experienced during that period.

Until now, this record was incomplete and based on comparisons with similar studies carried out in other parts of the planet. Its relevance consists precisely in that it allows us to maintain that climatic variations in the southern hemisphere have occurred almost simultaneously, at least for the indicated time, which includes since the penultimate ice age.

Carina Lange pointed out in this regard that “marine sediments offer a continuity in the record that one often does not find on the continent.”

“In this research, what we wanted to see was how the terrigenous contribution (sediments of continental origin and meltwater) transported by the great ice cap that covered all of Patagonia had varied. For its eastern side, in Argentina, there are very good models that allow it to be delimited, but in the west it is not clear how far it extended,” he says.

The cap that Carina Lange refers to, called the Patagonian Ice Sheet, during the last glacial maximum, about 20 thousand years ago, reached an extension where it covered the entire Patagonian Andes and reached further south of the Drake Passage. Today, of that mantle, only three remnants remain: the North Ice Field, the South Ice Field and the Darwin Mountain Range.

Of course, even though they amaze visitors with their extension, they represent only 4% of the total extension of the Patagonian Ice Sheet at its maximum extent.

“What was seen is that there were moments within these 140 thousand years when this great cap advanced towards the Pacific releasing terrigenous material in a much greater proportion than what was observed during the last 11,000 years,” adds Carina Lange. These times of greatest contribution coincide with cold, rainy seasons and intense winds.

work process

The data were obtained in a campaign carried out aboard the scientific vessel RV Mirai, run by the Japanese Agency for Maritime-Earth Science and Technology, JAMSTEC, developed in January 2019 in the south of the country.

The ship, whose name means future in Japanese, is 129 meters long, a size that allows it to transport cutting-edge equipment and a large capacity of scientific and technical personnel.

For sediment analysis, the seabed is penetrated with a piston corer; which is a hollow metal tube several meters long, inside which is a PVC tube that will house the extracted sediment. Said tube with the sediment is cut lengthwise into two halves, opened and the sedimentary layers that compose it are described and sub-sampled.

Lange explains that “this vessel made available resources that Chile does not have, and that allow drilling to the depth required.”

The analysis complements the climatic records obtained from terrestrial and other marine sources, and provides evidence on the sensitivity of the Patagonian ice fields to climatic variations, including those currently underway.

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