A climate archive melts in Switzerland and scientists will lose very long records: palaeoarchives
In the frozen layers of glaciers there is evidence of changes in temperature and atmospheric composition of the Earth. But as the climate warms, some of the longest records of our changing planet are melting.
One such archive is the Corbassière glacier in Switzerland. The high-altitude glacier is located on the slopes of the Grand Combin, one of the highest peaks in the Western Alps.
Swiss glaciers melting
It has suffered the same fate as many of Switzerland's alpine glaciers, which together have lost more than half their volume since the 1930s. Some of the most recent changes to the Corbassière glacier are visible in these images below, captured in August 2001 and in August 2023.
The images were acquired by Landsat 5 and Landsat 8, respectively. In just over two decades, Corbassière has shrunk in area and surface mass. The glacier was darker in 2023 due to lack of snow and the glacier tongue had retreated.
A research team from Switzerland and Italy took ice cores from the Corbassière Glacier in 2018 and 2020 to reconstruct past concentrations of the region's aerosols, or small airborne particles that became suspended in the atmosphere and then deposited on the ice. This information from glaciers around the world can provide clues about past environmental conditions thousands of years ago.
Thaw and recent data problems
Ice cores contain ammonium, nitrate and sulfate ions, signatures of aerosols found in the snow deposited on glaciers year after year. Ion concentrations are lower in winter than in summer because less polluted air can rise from the valley when the air is cold. The team analysed a core drilled into the glacier in 2018 and found seasonal fluctuations in the amount of ion deposits throughout the ice core, as expected.
“But when we went to core the glacier in 2020, we immediately noticed that it was melting on the surface,” said Margit Schwikowski, an environmental chemist at the Paul Scherrer Institute in Switzerland.
Schwikowski led the team of researchers that analysed the ice cores with doctoral student Carla Huber. In the 2020 core, seasonal ion fluctuations were only present in the top three or four annual layers. Deeper in the ice (and further back in time), scientists noticed fewer ions overall and that their quantities fluctuated less than expected. As reported in
Nature Geoscience, the team found evidence that previous melting of the glacier surface between 2018 and 2020 likely penetrated the glacier layers beneath and carried away aerosol ions.
Schwikowski and other ice core experts around the world are part of an effort to preserve the cores of the last remaining glaciers. The initiative, led by the Ice Memory Foundation, aims to obtain ice cores from 20 endangered glaciers around the world within 20 years and compile them into a global climate archive. "Glaciers are receding around the world and we may encounter similar problems elsewhere," Schwikowski said. Even at the highest altitudes of the Alps, he added:
NASA Earth Observatory images taken by Wanmei Liang, using US Geological Survey Landsat data. Photo of Margit Schwikowski and Theo Jenk by Riccardo Selvatico. Story by Emily Cassidy.