Ice loss has huge implications for regional water resources
FRISCO — Glaciers in the Tien Shan, Central Asia’s largest mountain range, have lost 27 percent of their mass and 18 percent of their area during the last 50 years, shedding an average of 5.4 gigatons of ice per year.
By 2050 about half of Tien Shan’s glacier volume could be depleted, a team of scientists estimated in a new paper published in the current online issue of Nature Geoscience.
The study was led by scientists with the GFZ German Research Centre for Geosciences and the institute of the French Centre National de la Recherche Scientifique at Rennes University.
Glaciers play an important role in the water cycle of Central Asia. Snow and glacier melt from the Tien Shan is essential for the water supply of Kazakhstan, Kyrgyzstan, Uzbekistan, and parts of China.
“Despite this importance, only little was known about how glaciers in this region changed over the last century,” said researcher Daniel Farinotti.
Most of the direct monitoring programs were shut down with the collapse of the Soviet Union and have only recently resumed, so Farinotti and his colleagues created a reconstruction of the glacier evolution in the Tien Shan.
“We combined various methods based on satellite gravimetry, laser altimetry and glaciological modelling” Farinotti said. “This way, we were able to reconstruct the evolution of every single glacier. Currently, the Tien Shan is losing ice at a pace that is roughly twice the annual water consumption of entire Germany.”
Glaciers can store water as glacier ice over decades, and transfer winter precipitation into the summer months by releasing it as melt water. This is particularly important in seasonally arid regions, i.e. regions that have months with virtually no precipitation, since local water supply is then closely linked to meltwater availability.
The scientists said Central Asia is the poster child for regional dependence on glacially fed water supplies. The fate of glaciers in the region is critical to water availability and food security.
The study found that glacier retreat in the Tien Shan accelerated between the 1970s and the 1980s.
“The long-term signal is clearly related to the overall rise in temperature,” Farinotti said.
In fact, the study shows that the rise in temperature, and summer temperature in particular, is a primary control for glacier evolution in the region.
“For Central Asia, this statement is less trivial than it might seem at first glance: Since the winter months in the region are very dry and the mountains are that high, glaciers receive most of their snowfalls during summer.” Farinotti explained. “This means that an increased temperature contributes to both, increased melt and reduced glacier nourishment – and obviously, both contributes to glacier wastage.”
Modeling future changes based on an increase of 2 degrees Celsius in summer temperatures between 2021 – 2050, the authors also provide a first outlook for the future evolution: Half of the total glacier ice volume present in the Tien Shan today could be lost by the 2050s.