Glaciers are natural archives of past climates. The frozen layers of glaciers are evidence of changes in Earth's temperature and atmospheric composition. But as the climate warms, some of the longest records of Earth's change are disappearing. Switzerland's Corbassière glacier is one such archive. This high-altitude glacier is located on the mountainside of the Grand Conbin, one of the highest peaks in the western Alps. It shares the fate of many of Switzerland's alpine glaciers, which have lost more than half their combined volume since the 1930s.
These images, taken in August 2001 (left) and August 2023 (right), show some of the recent changes in the Kobachiel Glacier. They were acquired by Land Remote Sensing Satellite 5 and Land Remote Sensing Satellite 8 respectively. In just over two decades, the Cobachiel Glacier has shrunk in size and surface area. Due to a lack of snow cover, the glacier in 2023 is darker and the glacier tongue has retreated.
A team of researchers from Switzerland and Italy collected ice cores from the Cobachiel Glacier in 2018 and 2020 to reconstruct the region's past concentrations of aerosols, tiny airborne particles suspended in the atmosphere and then deposited on the ice. Such information from glaciers around the world can provide clues about environmental conditions thousands of years ago.
The ice cores contain ammonium, nitrate, and sulfate ions that are characteristic of aerosols in the snow that is deposited on glaciers year after year. Ion concentrations are lower in winter than in summer because less polluted air rises from valleys when the air is cold. The team analyzed ice cores drilled from the glacier in 2018 and found that seasonal fluctuations in the amount of ion deposition throughout the core were as expected.
"But when we cored the glacier in 2020, we immediately saw that the glacier's surface was melting," said Margit Schweikowsky, an environmental chemist at the Paul Scheele Institute in Switzerland.
Schweikowsky led a research team that analyzed the ice core together with doctoral student Carla Huber. In the 2020 ice core, seasonal fluctuations in ions appeared only in the top three to four growth ring layers. Deeper in the ice (and farther back in time), the scientists noticed that there were generally fewer ions than expected, and that the ion numbers fluctuated less than expected.
According to the journal Nature Geoscience, the team found evidence that previous melt on the glacier's surface between 2018 and 2020 likely penetrated the underlying glacier layer, carrying away aerosol ions. This melting makes the ice cores unusable for the team's studies, and other attempts to core the glacier have yielded the same results. Valuable information stored in the ice was destroyed.
Schweikowsky and other ice core experts from around the world are involved in an effort to preserve ice cores from the last surviving glaciers. The initiative, led by the IceMemory Foundation, aims to obtain ice cores from 20 endangered glaciers around the world over 20 years and collect them into a global climate archive.
"Glaciers are retreating globally, and we may find similar problems in other locations," Schweikowsky said. "Even at the highest altitudes in the Alps, glaciers are becoming unsuitable as natural paleontological archives," she added.
Compiled from:ScitechDaily