From the Himalayas to Switzerland, the world’s glaciers are melting – threatening vital water supplies and increasing the risk of sea level rise.
In the next 25 years, more than half of all of Switzerland’s small glaciers will disappear − and Canada could lose 70% of the volume of its frozen rivers by 2100.
Some of the 37 glaciers in Glacier National Park, Montana, have been reduced by 85%, and of the 37, only 26 remain large enough to warrant the classification of glacier − that is, they have enough mass to flow.
And in high Asia, where 800 million people are at least partly dependent on summer meltwater, there are worries.
Hamish Pritchard, a glaciologist at the British Antarctic Survey, reports in Nature journal that the summer meltwater from the glaciers in the Himalayas, the Hindu Kush, Karakoram, Pamir and other mountain ranges altogether delivers enough for the basic needs of 136 million people.
During droughts, meltwater is the principal source for the upper Indus and Aral river basins, and any glacial water loss would increase the risk of social instability, conflict, and sudden, uncontrolled migrations of population.
According to Dr Pritchard, in total, the glaciers of high-mountain Asia send 23 cubic kilometres of water downstream each summer. Without these glaciers, summer monthly water inputs in an average year would be down by 38% in the upper Indus basin, and by up to 58% in drought conditions.
In the upper Aral basin, lost summer water inputs would frequently reach 100%. Glacial loss would be bad news for the people of Pakistan, Tajikistan, Turkmenistan, Uzbekistan and Kyrgyzstan.
All the more reason, says Twila Moon, postdoctoral research associate at the US National Snow and Ice Data Centre in Boulder, Colorado, to systematically monitor the condition of the world’s glaciers and to maintain data.
“The evidence is overwhelming − Earth is losing
its ice. Much of this loss is irreversible and
the result of human-caused climate change”
She argues in Science journal that although glacier melt contributes to sea level rise, it may be even more important to work out when society will start to experience the coastal flooding that could displace millions.
That the glaciers are going is a given. Careful studies over many years suggest that some of Greenland’s glaciers are accelerating on their way to the sea. There have also been alarming losses reported from Bolivia, and even in Canada.
Reports from the high mountains of Asia have been incomplete, but there is enough evidence to suggest that perhaps half of all the ice could be gone in the next 30 years.
Dr Moon says: “The evidence is overwhelming − Earth is losing its ice. Much of this loss is irreversible and the result of human-caused climate change.
“Unless substantial climate response action is taken, and the trend of global temperature rise is reversed, we will continue to see Miami streets swallowed by sea, and glacier freshwater reservoirs melt into mud.
“And we can expect this pattern to continue for decades, centuries, and indeed millennia. As scientists, we must make this reality clear and help to ensure that action is taken to minimise impacts globally.”
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