More often than not, we hear stories about glaciers retreating or even disappearing in the face of climate change. Countries like Venezuela and Spain are currently losing the last of their glaciers. While most of the world’s glaciers are shrinking, there are a few glaciers west of the Himalayas in eastern Karakoram and West Kunlun that are stable or actually experiencing slight mass gains. What accounts for the difference? A recent study by Akiko Sakai and Koji Fujita explores this question.
The “Karakoram Anomaly”
With almost all of the glaciers in the world declining as a result of warming climate, it is strange to find growing glaciers, particularly in the cold, rugged terrain of the Karakoram. “This anomalous behavior is called the Karakoram anomaly,” lead researcher Akiko Sakai explained to GlacierHub.
Specialists in the region have proposed two possible explanations for this difference in glacier behavior: spatial heterogeneity in climate change (climatic forcing) or differing glacier responses to climate change. But according to Sakai and Fujita, neither explanation has demonstrated strong supporting evidence. In their study, they examined the glacial response by correlating the sensitivities to mass change with temperature change and found that “over 60 percent of the spatial variance in glacier mass balance is due to the spatially differentiated glacier response to temperature change.”
Christopher Nuth from the University of Oslo explained to GlacierHub what this correlation means. “Basically, their number of 60 percent correlation reflects that the pattern of glacier mass changes seen across the Himalayas can be largely explained by the individual glaciers characteristics,” he said. “This would suggest that the so-called Karakorum Anomaly would not per chance be an effect of variable climate change patterns, but rather an effect of varying glacier characteristics across the region to a change in climate.” Nuth also added, “This study is pretty amazing to have resulted in a high correlation of 0.6 between these large scale datasets.”
“Glaciers can undergo different mass changes even under uniform climate change,” Sakai said. Andreas Kääb also from the University of Oslo, told GlacierHub, “The pattern of elevation changes (with strong losses to the very east, and almost stable glaciers to the west) can be well expected just from the different mass balance types of the glaciers.”
Etienne Berthier, a glaciologist at the National Center for Scientific Research in Toulouse (France) who has also studied the phenomenon, further explained to GlacierHub, “Depending on their climate setting, glaciers have a strongly differing sensitivity to temperature. Under a similar 1 degree Celsius step increase in temperature, glaciers would lose much more ice in maritime/humid climate (the southeast Tibetan Plateau or northwest India) than in continental regions (western Tibetan Plateau).”
According to the study, the sensitivity of a glacier to changing climate depends on the glacier’s present environment. More specifically, this means the environmental control on the heat and mass balances of glaciers. “For instance, glaciers in an arid environment require relatively colder conditions and tend to be less sensitive to temperature change than those in a warm and humid climate,” the authors note.
But to say these glaciers are growing is a bit misleading. Although it may be true to say they are accumulating more mass and spreading farther down, this phenomenon is a product of the warming of very cold, dry regions and increasing snow precipitation. In very cold regions, the rising temperature still remains below freezing. Although glaciers won’t melt under these conditions, the ice will lose its stiffness, become softer, and eventually spread out beyond previous boundaries. Thus, the glacier accumulates land area.
The environment surrounding the Karakoram glaciers is one of the few in the world to exemplify this notion, which explains the name. However, the results of this study found that the Karakoram glaciers are not behaving anomalously. Rather, “they are insensitive to temperature change, and thus change their mass slightly due to local climatic forcing,” the authors explain.
Measuring changes in glacier size
How do scientists track the differences in these changes? According to Kenneth Hewitt of Wilfrid Laurier University, it is quite difficult and costly to collect observations in these remote, treacherous landscapes. “This is all a bit new and yet to be fully critiqued by the glaciology community,” Hewitt told GlacierHub.
One of the primary methods used to evaluate glacier response in this study was calculating the mass-balance sensitivity to air temperature (MBS). “MBS indicates mass balance sensitivity to temperature, which means glacier mass response to 1 degree increase in air temperature,” explained Sakai.
“Thanks to remote sensing observations, we now have a good understanding of the contrasted pattern of glacier change in high Mountain Asia… But the drivers of this contrasted pattern are still debated,” Berthier told GlacierHub. “The study by Sakai & Fujita nicely shows that we do not necessarily need to detect a contrasted pattern of climate change to explain the strongly different glacier responses.”
One of the major factors scientists will be trying to predict is how the changing climate will impact monsoonal patterns and in turn how glacier mass changes will respond to altered distribution patterns of temperature and precipitation.
Hot topic, but does this change anything?
Beyond this study, the “Karakoram anomaly” and surge dynamics is a hot topic for scientists of the region. One recently published study, with Berthier part of the team, analyzed mass changes in the region from 2000 to 2016. Another study by Silvan Leinss delved into the recent collapse of two surging glaciers in Tibet that had been growing due to increased precipitation and warming before their dramatic collapse last year.
Although the thought of stable glaciers can make people hopeful, the fate facing glaciers across the world has unfortunately not changed.