04/12/2023
An international research team led by the Institute of Polar Sciences and the Water Research Institute of the Cnr has discovered a surprising phenomenon: the increase in global temperatures has led the Himalayan glaciers to increasingly cool the air in contact with the frozen surface, mitigating temperatures locally. The study, carried out in collaboration with the Institute of Science and Technology Austria, has just been published in Nature Geoscience and explains how this cooling, found throughout the Himalayan chain, could preserve permafrost and high-altitude ecosystems
It is known that the world's glaciers risk completely melting and disappearing over time due to global warming. It is therefore surprising to learn that the glaciers of the Himalayan chain are going against the trend: the measured air temperature averages, instead of increasing, as expected, have remained suspiciously stable and the summer ones are decreasing. This was revealed by a study coordinated by the Institute of Polar Sciences (Cnr-Isp) and the Water Research Institute (Cnr-Irsa) of the National Reseach Council of Italy (Cnr), carried out in collaboration with the Institute of Science and Technology Austria (Ista). The results have just been published in the journal Nature Geoscience.
“We know that the effects of warming depend on altitude: the mountain tops are more affected by the effect of global warming and warm up more quickly”, explains Franco Salerno, co-author of the study and Cnr-Isp researcher. “However, we found that a high-altitude climate station at the base of Mount Everest, Nepal, showed an unexpected phenomenon: measured air temperature averages remained suspiciously stable, rather than increasing.”
To explain the phenomenon observed, the research team had to carefully examine the meteorological data that the climatic station of the International Pyramid Laboratory-Observatory Ev-K2-Minoprio, located at 5050 m above sea level on the southern slopes of Mount Everest, recorded for three decades, the longest existing high altitude-climate series in the world. A series that represents the only existing evidence to understand how the climate has changed in the mountains of the Third Pole. “Glaciers are reacting to climate warming by increasing temperature exchange with the surface. Global warming causes, in fact, an increase in the temperature difference between the warmer ambient air above the glacier and the air mass in direct contact with the glacier surface,” continues Francesca Pellicciotti, Ista researcher and co-author of the paper. “This leads to an increase in heat exchange on the surface of the glacier and a greater cooling of the surface air mass. The cool, dry air masses at the surface become denser and flow down the slopes into the valleys, cooling the lower parts of the glaciers and surrounding ecosystems, which are thus dependent on the health of the glacier itself.”
“Essentially we believe that climate warming is triggering an increase in these cold air masses – known as katabatic winds – which descend from the slopes of glaciers and that this phenomenon can contribute to preserving the permafrost and surrounding vegetation,” explains Nicolas Guyennon, co-author of the study and researcher at Cnr-Irsa.
To delve deeper, the team drew on the latest scientific advances in climate models: the global climate reanalysis called “ERA5-Land” which combines model data with observations from around the world. The interpretation of this data allowed the researchers to demonstrate that the observed phenomenon occurred not only on Mount Everest, but in the entire Himalayan chain. “The next step will be to find out which key characteristics of glaciers favour this reaction,” adds Salerno. We will have to understand which glaciers can react in this way to global warming and for how long.”
“While other glaciers, for example our Alpine ones, are experiencing dramatic changes, the high mountain glaciers of the Third Pole in Asia are much larger, contain more ice and therefore have longer reaction times,” continues Guyennon “This phenomenon must not lower our guard against climate change. The perceived cool temperatures coming down from glaciers are an emergency reaction to global warming, rather than an indicator of the long-term stability of glaciers.”
Future study prospects are interesting: the team will investigate whether the Pamir and Karakoram glaciers, which unlike what happens in the rest of the world are “stable” or “growing”, are actually reacting to global warming by blowing more and more cold winds along their slopes. “The slopes of the Pamir and Karakoram glaciers are generally flatter than those of the Himalayas. Therefore, we hypothesize that cold winds may cool the glaciers themselves more rather than reaching the surrounding environments further down. We will know in the next two years,” concludes Salerno.
Per informazioni:
Franco Salerno
Cnr - Isp
franco.salerno@cnr.it
Nicolas Guyennon, Cnr-Irsa, e-mail: nicolas.guyennon@irsa.cnr.it
Jessica Marzaro, Cnr-Isp, email: jessica.marzaro@isp.cnr.it
Ufficio stampa:
Cecilia Migali
Cnr Press Office
cecilia.migali@cnr.it
Responsabile Unità Ufficio stampa:
Emanuele Guerrini
emanuele.guerrini@cnr.it
ufficiostampa@cnr.it
06 4993 3383
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