Shrinking Arctic glaciers were replaced by 35 “new” islands and 2,500km of coastline in the first two decades of this century, new research has found. Researchers studied satellite images of over 1,700 glaciers in Greenland, Alaska, the Canadian Arctic, Russian Arctic, Iceland and Svalbard.

They found that accelerated climate warming had caused the majority of marine-terminating glaciers, those that flow into the ocean, in the northern hemisphere to retreat substantially in the 21st century. Of the glaciers studied, 85% had retreated, and an average of 123km of new coastline was revealed each year between 2000 and 2020.

Around two-thirds of the new coastline was uncovered in Greenland, where the shrinking Zachariae Isstrom glacier revealed 81km of new coastline. This was more than twice as much as any other glacier in the hemisphere.

In fact, just 101 glaciers, less than 6% of the total, were responsible for more than half the new coastline.

Scientists warned that fresh coastlines are more prone to landslides which could have the knock-on effect of causing tsunamis. The study, published on Nature.com, used the example of a 2017 landslide in Greenland, which caused a tsunami with an initial height of 90 to 100m, which lessened to around 9m when it reached the settlement.

Four people were killed and nine injured, while 11 buildings were destroyed by the waters. As a result, 170 residents were evacuated in case of further danger, and the settlement affected was abandoned altogether after the event.

A glacier is a large mass of ice and snow formed in areas where low temperatures do not allow snow to melt in summer. Glaciers move slowly, flowing downwards like water in a river but typically at a rate of just 50m (160ft) each year.

They are also the world’s largest supply of freshwater, but rising global temperatures mean that many are retreating.

Researchers on this project found that the Arctic has warmed up to four times faster than the rest of the world in the last 40 years.

This threatens the existence of glaciers and may mean they melt at a faster rate, potentially worsening existing global challenges as sea levels rise and water resources decline.

Last month, a UNESCO report warned that glaciers are disappearing at a faster rate than ever before, with the last three years seeing the largest loss of glacial mass since records began.

Michael Zemp, director of the World Glacier Monitoring Service, said the 9,000 gigatons of ice lost from glaciers since 1975 are equivalent to “an ice block the size of Germany with the thickness of 25 metres”.

The UN has also warned that retreating glaciers threaten supplies of food and water for 2 billion people around the world.

It is expected that two thirds of all irrigated agriculture in the world is likely to be affected in some way by the dwindling ice mass.

This is particularly relevant in mountainous regions, where over 1 billion people live globally and where over half are already suffering from food insecurity.

Food production in these areas is strongly dependent on mountain waters, melting snow and glaciers.