Earth’s glaciers on the verge of disappearing

An overwhelming majority of the world’s glaciers are shrinking and many of them could disappear in the not-too-distant future, according to a series of new studies. This means that we could soon be experiencing the same conditions as during the post-glacial warm period 8 000-4 000 years ago.

During that period, the average temperature was two to three degrees higher than today, and the vast ice sheet on Greenland was significantly reduced.

– Then all the glaciers in Sweden and the Alps disappeared. They melted away, just like many other glaciers around the world,” says Nina Kirchner, a glaciologist at Stockholm University.

– Then they came back. The Little Ice Age between the 14th and 19th centuries was the peak, and in Sweden they actually peaked around 1910, in the Alps slightly earlier, around 1860.

The Earth’s glaciers number around 200 000, with some of the largest found in Alaska, Arctic Canada and the Himalayas (not counting the ice sheets of Greenland and Antarctica). They cover an area of about 726 000 square kilometres, about 1.6 times the area of Sweden, and their combined ice volume has been estimated at 158 000 cubic kilometres.

Unseen ecosystems

This may sound impressive, but it represents only a fraction, half a percent, of the total volume of ice on Earth. Most of the world’s ice, 99.5%, is found in Greenland and Antarctica. This means that the melting of ordinary glaciers has only a marginal impact on sea level rise. But the situation is still considered serious by most scientists.

– Of course it is serious, not for sea level, but for the ecosystems of many areas. They will be damaged when the water supply is reduced or affected in time by melting. Plants will be out of sync with the water supply at an important time of year. We don’t know how it will turn out,” says Nina Kirchner.

– It’s also never been as fast as it is now. Melting at the beginning of the post-glacial warm period was more gradual.

Melting accelerates

Other scientists have pointed out that there could be a shortage of drinking water in some parts of the world, particularly in southern Asia, which relies on meltwater from glaciers in the Himalayas and on the Tibetan plateau.

One of the new studies, published in the scientific journal Nature, suggests that almost all glaciers have been shrinking, and that melting has accelerated. The glaciers together lost 227 gigatonnes of ice per year from 2000 to 2004, but 298 gigatonnes per year from 2015 to 2019.

Interestingly, until recently, glaciers have lost more ice than both Greenland and Antarctica, even though the latter holds much larger ice masses. However, according to the UN IPCC, Greenland seems to have pulled back a bit lately.

Glaciers disappear completely

In another study, published in Geophysical Research Letters, the researchers analysed all the glaciers that flow into the sea in the Northern Hemisphere. The analysis shows that 85.3% of the glaciers have retreated since 2000. In total, their extent decreased by 7,527 square kilometres and more than seven percent of the glaciers lost their contact with the sea during the period.

A third study, in Nature Geoscience, found that the amount of water in the world’s mountain glaciers appears to have been overestimated. The amount is about 20% less than previously thought, which does not bode well for the future.

So what can we expect? According to the IPCC, by 2100, 80% of the world’s high alpine glaciers will have disappeared completely or declined significantly. In Sweden, 24 glaciers have shrunk by an average of 50-60 metres between 2010 and 2018. The largest reduction is around Kebnekaise, where four glaciers have shrunk even more, by a maximum of 120 metres.