Mon. Apr 15th, 2024

What air did Caesar and Christopher Columbus breathe?

De ancestral ice to better understand the climate

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Jørgen Peder Steffensen, professor of glaciology at the University of Copenhagen in Denmark

Agence France-Presse

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In the suburbs of Copenhagen, a giant fridge has been hiding, with its ice cores, the secrets of the atmosphere for millennia and allowing scientists to better understand the ups and downs of the climate.

What we have in these archives is climate change from prehistoric times, we have a record of human activities over the last 10,000 years, explains Jørgen Peder Steffensen to AFP. , professor of glaciology at the University of Copenhagen in Denmark.

Ice cores have been his passion for 43 years. It was while drilling the ice floe that he met his wife, Dorthe Dahl-Jensen, also a leading authority on paleoclimatology.

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Information about climate change is archived in the ice cap.

Often between Greenland and Copenhagen, Mr. Steffensen has administered the island-continent's ice library since 1991, which, with its cumulative 25 kilometers of samples, is among the most important in the world.

These frosty fragments are all the more exceptional because they are not frozen water, but compressed snow.

The air between the snowflakes is trapped as bubbles, and that air is the same age as ice, he says .

In the antechamber, or reading room, it is -18°C, a mild temperature compared to the -30°C in the main room, where some 40,000 blocks of ice are stored in boxes.

This is where the researchers study the specimens – never for long, to avoid cold snap – under the microscope.

From a box, Mr. Steffensen takes out a special carrot, whose air bubbles are visible to the naked eye: snow that fell in the year zero.

< p class="StyledBodyHtmlParagraph-sc-48221190-4 hnvfyV">So we have Christmas snow, real Christmas snow, said the lively sixty-year-old smiling under his thick hat.

In this unusual library, where the works are exclusively consulted on site, the oldest extracts were brought back in the 1960s from Camp Century, a then secret American military base in Greenland.

The most recent were this summer, when scientists reached the bedrock in the east of the island, more than 2.6 kilometers deep.

This latest arrival contains extracts from more than 120,000 years ago, during the last interglacial period, a time when the atmospheric temperature in Greenland was 5°C higher than today.

The planet has been much warmer than it is today; today. But that was before the arrival of man.

A quote from Jørgen Peder Steffensen, professor of glaciology at the University of Copenhagen in Denmark

The new ice blocks should provide a better understanding of rising sea levels, which can only partly be explained by the melting of the ice cap.

Another part of the explanation comes from ice streams, these glaciers which are shrinking like ice sorrow.

If we better understand ice streams, we will be able to have a better idea of ​​the future contribution of Greenland and Antarctica to rising sea levels, says Mr. Steffensen.

We hope to be able to help determine sea level in a hundred years with a margin of error of 15 centimeters, much smaller than the current margin (70 centimeters), says the scientist.

Ice cores are the only direct sources to know the state of the atmosphere in the past, before anthropogenic pollution.

Using ice cores, we were able to determine how greenhouse gases carbon dioxide and methane vary over time. We can also see the impact of fossil fuels in modern times, Steffensen points out.

This project is distinct from that of the Ice Memory foundation which aims to collect ice cores from twenty sites around the world in order to preserve them in the Franco-Italian Concordia station in Antarctica for researchers of the future, before that these resources do not disappear due to climate change.

Storing the glacial memory of Greenland is very good, welcomes the president of the foundation, Jérôme Chappellaz.

But, he worries, this storage in an industrial freezer may be subject to hazards likely to erase this memory: technical glitch , financing problems, attack, war…

In 2017, a freezer breakdown exposed 13% of the precious samples of millennia-old ice preserved by the #x27;Canadian University of Alberta to unwanted heat.

On the Concordia plateau, far from human chaos, the average annual temperature is -55°C, offering optimal preservation conditions for centuries to come.

They have a treasure, underlines Mr. Chappellaz in an appeal foot to the Danes. We must protect this treasure and, as far as possible, ensure that it joins the world heritage of humanity.

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