How loss of trillion tonnes of ice every year is transforming planet Earth

The death of an American tourist when a wall of ice collapsed during a trip to Iceland’s Breidamerkurjökull glacier is a reminder of the dangers posed by these vast, moving conveyor belts. One senior police officer said he trusted the experienced mountain guides to know “when it’s safe or not safe to go” but added that it was “always possible to be unlucky” and “this is a living land, so anything can happen”.

However, the guides’ experience is based on the past and, when things are changing rapidly, that may not be as reliable as expected. In 2021, a Dundee University study documented how quickly the Breidamerkurjökull glacier was retreating – by up to 250 metres a year – with the annual summer melting outstripping the accumulation of ice in the winter.

And it is far from alone. Last year was the 36th in a row that a group of ‘reference glaciers’, which are regularly measured by the World Glacier Monitoring Service, lost ice rather than gaining it. The rate at which ice is being lost is accelerating, from 17.1cm a year in the 1980s to 88.9cm a year in the 2010s.

The total amount of ice loss from Earth in the last few decades is astonishing. A 2021 study used satellites to survey 215,000 mountain glaciers, the Greenland and Antarctic ice sheets, and floating sea ice. It found that between 1994 and 2017, some 28 trillion tonnes of ice was lost. To give an idea of the scale, this would cover the whole of the UK to a depth of 100 metres (328ft).

Air bubbles rise in surface meltwater on the ice sheet that covers most of Greenland (Picture: Joe Raedle/Getty Images) | Getty Images

Vast mountains of ice

The researchers also found the rate of loss is increasing dramatically, rising from 0.8 trillion tonnes a year in the 1990s to 1.3 trillion tonnes per year by 2017. An article on the European Space Agency’s website helpfully explained: “One trillion tonnes of ice can be thought of as a cube of ice measuring 10x10x10 km, which would be taller than Mount Everest.”

The Charctic sea ice graph, produced with Nasa’s help by the US National Snow and Ice Data Centre, provides a daily running commentary on the scale of the melting. On Sunday, there were 4.769 million km2 of sea ice in the Arctic, which does sound like a lot. However, this was nearly a third less than the average for the same date between 1981 and 2010.

The world is heading towards a historic moment. A paper published in March in the journal Nature Reviews Earth and Environment found the Arctic could be essentially free of ice during the annual September low point in this decade or the next.

Snowball Earth

The world’s glaciers and ice sheets are the remnants of the last Ice Age, which ended some 10,000 years ago. They have persisted ever since, but have been dramatically reduced in just a few short decades by the rise in global temperatures caused largely by the burning of fossil fuels. It’s worth noting that without some greenhouse gases, the Earth would basically be a giant snowball. But it is possible to have too much of a good thing.

All this melting has a number of effects, perhaps the simplest of which is that when land ice turns into water, sea levels will rise. This is being made worse by the expansion of water as the sea, like the atmosphere, gets warmer. The inhabitants of low-lying Pacific islands are among the first to feel the effects.

A United Nations’ report published on Monday, called Surging Seas in a Warming World, found that sea levels in the tropical Pacific have risen by as much as 15cm in the last 30 years, creating a real problem for islands with an average elevation of just one or two metres and where 90 per cent of the population live within 5km of the coast.

‘No lifeboat’

In a speech on the island of Tonga today, UN Secretary-General Antonio Guterres said: “The ocean is overflowing. This is a crazy situation. Rising seas are a crisis entirely of humanity’s making. A crisis that will soon swell to an almost unimaginable scale, with no lifeboat to take us back to safety.”

Tonga is half a world away and Scotland is still rising after being pressed down by the sheer weight of the ice that covered it during the last Ice Age so, to some, these threats may seem remote and Guterres’ remarks overblown. However, there is another effect of ‘global melting’ that just might have terrifying consequences for this country before the century is out.

Fresh water flowing off the Greenland ice sheet is disrupting a key mechanism that drives the ‘Atlantic Meridional Overturning Circulation’, a vast ocean current that brings warm weather to the UK from the Caribbean.

Natural thermometers

A report last year by the Intergovernmental Panel on Climate Change, the world’s main scientific body on the issue, concluded this current is “very likely to weaken over the 21st century” but expressed “medium confidence” that “an abrupt collapse” would not happen before 2100. “If such a low probability event were to occur, it would very likely cause abrupt shifts in regional weather patterns and... large impacts on ecosystems and human activities,” it added.

Under such a scenario, Scotland would likely become dramatically colder – one reason why ‘climate change’ is more commonly used these days than ‘global warming’ – with profound consequences for farming and life in general, amid global chaos. But don’t worry, scientists have “medium confidence” this won’t happen – at least until sometime after 2100.

Meteorologists use an array of instruments, including thermometers, to warn us of impending storms. Shrinking glaciers can be looked at as giant ‘natural thermometers’, with the ice shrinking in response to higher temperatures, rather than expanding like mercury. In doing so, they are providing hard evidence, for anyone still in doubt, that climate change is real, but also a warning that this is a serious threat we must confront before it’s too late.