Glaciers as a climate archive – glacier melt destroys climate data – knowledge


The Corbassière should be one of glaciers collected into a global climate archive. But now the analyzes of the ice core at Grand Combin in Valais show: the climate archive is already lost. Why the loss is bearable while time is running out elsewhere.

Collect ice cores from 20 glaciers worldwide in 20 years – according to the initiative Ice Memory Foundation. To build a global climate archive from the glacier samples. Climatic conditions and atmospheric compositions from past eras are preserved in their ice: from greenhouse gases to air pollutants and plant pollen.

The ice core from Grand Combin in Valais should be one of these 20 samples. But now an im shows “Nature Geoscience” published report: Global warming has made the glacier largely unusable as a climate archive.

How will the glacier archive survive global warming?

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So that the 20 ice cores collected around the globe can continue to be used for studies in the future, they will be permanently stored in an ice cave in central Antarctica. The average temperature of minus 50 degrees Celsius near the South Pole ensures that the cores are preserved – even if global warming causes all the Alpine glaciers to melt at some point. This means that future generations could extract completely different information from the ice than we do today. Because analysis methods are constantly evolving.

Only 25 instead of 80 meters drilling depth

A research team from the Paul Scherrer Institute (PSI) led by Margit Schwikowski drilled at the Grand Combin in 2018 and 2020. While the 2018 race went as expected, the team encountered difficulties on the mountain two years later.

When water melts and freezes again, solid layers of ice form. During the 2020 drilling, the researchers encountered a particularly thick layer of ice. And just above it: a very water-containing, soft layer. This transition has caused technical problems. “The drill is not suitable for these conditions,” explains Schwikowski. “We tried three times in total, but didn’t get further than 25 meters.”

They actually wanted to drill down to the bedrock at a depth of 80 meters. To capture the entire archive of the glacier, which spans thousands of years.

The climate data flows away with the meltwater

Normally, the amount of fine dust particles trapped in the ice fluctuates with the seasons. Particle-bound substances such as ammonium, nitrate and sulfate come from the air and are deposited on the glacier through snowfall. Concentrations are high in summer and low in winter. Because when it’s cold, less polluted air rises from the valley. This creates a so-called signature in the ice.

Analysis of the ice core from 2020 now shows that the signature has been lost. The meltwater has seeped down from the surface to a depth of 20 meters. The water-soluble air pollutants have dissolved. “On the one hand, we lose information about stratification,” regrets Schwikowski. “On the other hand, the meltwater simply flows off the glacier.” The information not only loses its chronological order, but is lost.

Race against time

The PSI team has already been able to obtain ice cores in the Alps: at Mont Blanc and Monte Rosa. “We could probably cope with not storing an additional ice core from the Alps,” says Schwikowski. She is more concerned about glaciers from regions for which no information is yet available. For example the Kilimanjaro glacier. The drilling there failed last year due to a lack of approval from the Tanzanian government.

The ice core experts sample around two glaciers per year as part of the project Ice Memory Foundation. “But now we see that it would be much more urgent,” says Schwikowski. The Corbassière Glacier shows how climate data is lost in just two years.

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