Researchers from the Paul Scherrer Institute (PSI), in collaboration with colleagues from the University of Fribourg, Ca’ Foscari University of Venice, and the Institute of Polar Sciences of the Italian National Research Council (CNR), undertook an analysis of ice cores extracted in 2018 and 2020 from the Corbassière glacier located at Grand Combin in the canton of Valais. Their findings, published in Nature Geoscience, reveal a troubling reality: global warming has rendered this glacier unsuitable as a climate archive.
The comparison of the two sets of ice cores illustrates the accelerated melting of alpine glaciers, surpassing previous estimates. Margit Schwikowski, who heads the Laboratory for Environmental Chemistry at PSI, along with Carla Huber, Ph.D. student and primary author of the study, led the research. They examined the signatures of particulate matter embedded within the annual layers of the ice to draw their conclusions.
Glaciers, known as invaluable resources for climate research, encapsulate the climatic conditions and atmospheric compositions of past epochs within their ice. Comparable to tree rings and ocean sediments, glaciers serve as vital climate archives for scientific inquiry.
Under normal circumstances, the concentration of particle-bound trace substances in ice experiences seasonal fluctuations. Elements such as ammonium, nitrate, and sulfate originate from the atmosphere and settle on the glacier through snowfall. Their concentrations peak during summer and decline during winter, corresponding to decreased levels of polluted air rising from the valleys during colder temperatures.
The 2018 ice core, drilled to depths of up to 14 meters during preliminary investigations and encompassing deposits dating back to 2011, reflects these anticipated fluctuations. However, the 2020 core, extracted from depths of up to 18 meters under the guidance of PSI researcher Theo Jenk, displays expected fluctuations only within the upper three or four annual layers. Further down the ice, representing earlier periods, the curve depicting trace substance concentrations flattens noticeably, with a reduction in the total amount. Schwikowski’s team detailed these findings in their study.
Washed away by meltwater
The discrepancy observed between 2018 and 2020 led researchers to propose a compelling explanation: the glacier’s melting during this period was exceptionally intense, allowing a significant volume of surface water, laden with trace substances, to infiltrate deep into the glacier.
“However, it appears that the water didn’t refreeze, concentrating the trace substances,” concludes the environmental chemist. “Instead, it drained away, effectively washing them out.” This process distorted the signatures of the layered inclusions, rendering the climate archive unusable. It’s akin to a scenario where someone vandalizes a library, not only disarranging shelves and books but also pilfering volumes and jumbling the words in those left behind, rendering the original texts irretrievable.
The researchers meticulously examined meteorological data spanning 2018 to 2020. Lacking a weather station atop the Grand Combin, they amalgamated data from neighboring stations and extrapolated it for the study area on the mountain. Their analysis revealed warm conditions on the glacier, aligning with broader climatic trends, without these years being extraordinary outliers.
“We infer from this that there wasn’t a singular trigger for such pronounced melting but rather the culmination of many warm years in recent history,” Schwikowski remarks. “It seems a critical threshold has been surpassed, precipitating a notably potent effect.”
Source: Paul Scherrer Institute