The next few decades do not bode well for the world’s smallest glaciers. These tiny glaciers, less than half a square kilometer, dot mountains all over the world and account for 80%–90% of the globe’s mountain glacier population. But as temperatures rise, scientists worry that these glaciers will all but disappear.
Even if they seem insignificant because of their size, these glaciers “respond very quickly and therefore they can contribute significantly, even on the global level, in terms of sea level rise for the next decade,” said Matthias Huss, senior lecturer at the University of Fribourg in Switzerland and lead scientist in the research.
Dynamics of Very Small Glaciers
Larger glaciers of the world stretch and grow under the weight of accumulating snowfall, but small glaciers depend more on snow blown in from a storm or avalanche and generally stick to one place. In essence, they are like large “ice patches,” Huss said.
During hot summers, these very small glaciers lose mass in the form of meltwater, which feeds streams and irrigation systems in the valleys below. On average, the glaciers grow about 1.5–2 meters every winter and shrink about 2.5–3 meters every summer. In a particularly hot summer, a very small glacier can lose up to 20% of its mass, Huss said.
In the past few decades, scientists have noted that these glaciers are trending towards losing more mass than they gain. Twice a year for the past several years, Huss and his team visited 10 glaciers around Switzerland to monitor their mass gain and loss. They applied their measurements to a mathematical model that also incorporated data from the 1970s. The model showed that Switzerland’s 1133 glaciers are in great peril and most of them risk completely vanishing by 2025.
The models produced similar results when they were applied globally—in the next couple of decades, very small glaciers are at a great risk of disappearing completely, Huss reported last week at the Fall Meeting of the American Geophysical Union in San Francisco, Calif.
The acceleration of glacier mass loss isn’t exclusive to very small glaciers—even the world’s larger mountain glaciers have been shrinking, according to a 2014 state of the climate report in the Bulletin of the American Meteorological Society. Since the 1980s, the report said, mountain glaciers worldwide have lost a meltwater equivalent of 16.8 meters—which is like slicing 18.5 meters off the top of any given glacier—and this rate of melt is accelerating.
However, “in terms of the global retreat of glaciers, the small glaciers are responding the fastest to the recent climate change,” said Valentina Radic, an assistant professor at the University of British Columbia. She studies how climate change affects glaciers but wasn’t involved in this study.
Very small glaciers “are good indicators of what’s actually happening because they respond fast to the recent changes, giving us a good overview of what is happening to the present climate,” Radic said. Large glaciers may take hundreds of years to respond to shifts in the climate, while small glaciers may only take a decade or two.
Furthermore, Huss said, as larger glaciers melt because of rising temperatures, they still supply water to streams and irrigation systems. But these small, extrasensitive glaciers can disappear in a geologic flash, suddenly cutting off the water supply and exposing bare, mountain rock, which crumbles and can become a natural hazard.
They may not be mighty in size or even influential in the grand scheme of global climate change, but humans and animals alike depend on these small glaciers’ annual melt for water, and their disappearance could put a small but significant dent in sea level rise. The researchers estimate that if all the very small glaciers disappeared, they could contribute about 7% to the total impact that glacier melt has on sea level rise.
“Glaciologists would probably laugh about us because we are interested in these ‘ice patches,’” Huss said. But even if these very small glaciers are not relevant for the changes expected by the end of the 21st century, “they are relevant for the next few decades.”
—JoAnna Wendel, Staff Writer
Citation: Wendel, J. (2015), World’s smallest glaciers risk vanishing in warm climate, Eos, 96, doi:10.1029/2015EO042411. Published on 24 December 2015.