Climate scientists are well aware of glacier ice that melts away in the blazing sun, but a lot of ice also appears to disappear under the water surface. And the extent to which this has happened in recent decades has been considerably underestimated.
In January of this year, scientists already sounded the alarm: even in the most favorable climate scenario, in which the earth warms up only 1.5 degrees, half of all glaciers and a quarter of all glacier ice worldwide will disappear. It now appears that in these calculations an important melting process, namely that of glacial ice under water, has not been sufficiently taken into account. This means that the situation looks even sadder than expected.
On an expedition
An international team of climate scientists, consisting of Chinese, Austrians, British and Americans, went on an expedition to the Himalayas to explore several glacial lakes. Between 2000 and 2020, there appear to be 47 percent more lakes in the region. The overall dimensions grew by 33 percent and the amount of water increased by 42 percent. Satellite images already showed that a considerable number of glacial lakes have been added and that the lakes have grown in circumference, but the large difference in water volume surprised the scientists. It turned out that 2.7 gigatons (2,700,000,000,000 kilograms) more glacial ice melted in the Himalayas than previously estimated. For comparison, this is the equivalent of 570 million elephants or more than 1,000 times the number of elephants in the world.
Secrets under the surface of the water
In the Great Himalayas (the highest part), 6.5 percent more ice has melted than previous calculations suggest. A difference of 10 percent has been found in the Central Himalayas, with a peak of 65 percent for the Galong Co glacier, where the melting process has been underestimated until now. Satellites were unable to pick up on these changes because the data can only measure the surface of the water and cannot say anything about glacial ice turning into meltwater deep below the glacial lake.
“Our findings help local water management better deal with meltwater runoff from glacial lakes,” explains lead researcher Zhang Guoqing. Thanks to the improved estimate of the amount of meltwater, the content of the glacial lakes and the percentage of glacial ice loss per year, scientists can now also more accurately compare glaciers that end in a lake with glaciers that end on land (in the form of a river or waterfall) .
211,500,000,000,000 extra pounds of ice melted
In the study, the researchers emphasize how important it is to understand the mechanisms behind the loss of glacial ice. Only then can you really calculate how much ice has been lost and find out that this loss has been underestimated for years. According to the researchers, an estimated 211.5 gigatons, or about 12 percent, more ice melted worldwide than previously thought in the period 2000–2020. “This conclusion shows how important it is to include the amount of melt ice below the water surface of the glacial lakes in future estimates anywhere in the world,” says Tobias Bolch of the Graz University of Technology.
Too positive image
If you don’t, you will simply get a too positive picture of reality, because as it stands now, glaciers will shrink even faster and even disappear completely than predictions from previous studies already indicated. David Rounce of the UK Carnegie Mellon University says that the melting process examined in the study will leave its mark on the evolution of glaciers worldwide for a long time to come.
Fortunately, it is now easier to predict in vulnerable mountain areas where more ice will melt and how much that will be. In this way, local authorities can respond to drought and possible flooding.
