Antarctica has lost 8x the size of London in ice over last 30 years

Antarctica has lost an area of ice more than eight times larger than Greater London over the last 30 years, a study has revealed.

Using satellite data collected over the last three decades, scientists have painstakingly mapped the frozen continent’s shrinking borders.

The researchers measured the ‘grounding line migration’ – the change in location at which the continental ice shelf meets the open ocean.

This revealed that the continent’s ice loss is far more concentrated than scientists had previously thought.

Surprisingly, much of Antarctica’s ice sheet has actually remained fairly stable over the last three decades, with 77 per cent showing no grounding line migration since 1996.

However, extremely rapid loss was concentrated in Western Antarctica, the Arctic Peninsula, and some parts of East Antarctica.

This has resulted in a loss of nearly 5,000 square miles (12,820 square km) of grounded ice – a loss of 170 square miles (442 square km) every year on average.

Lead author Professor Eric Rignot, of the University of California, Irvine, says: ‘It’s like the balloon that’s not punctured everywhere, but where it is punctured, it’s punctured deep.’

Professor Rignot and his co–authors compiled data from satellites operated by space agencies all around the world, including NASA and the European Space Agency.

For the first time, this reveals exactly how Antarctica’s grounding line has responded to warming ocean temperatures.

‘We’ve known it’s critically important for 30 years, but this is the first time we’ve mapped it comprehensively across all of Antarctica over such a long time span,’ says Professor Rignot.

The most dramatic changes have been seen in West Antarctica’s Amundsen Sea and Getz regions, where glaciers have retreated by six to 25 miles (10–40 km).

Since 1996, the Pine Island Glacier retreated by 20.5 miles (33 km) and the Smith Glacier by a staggering 26 miles (42 km).

Meanwhile, the Thwaites Glacier, also known as the ‘Doomsday Glacier’, has moved back 16 miles (26 km).

This is problematic because the melting of glaciers adds fresh water to the oceans that would have otherwise been trapped on land, contributing to sea level increases.

A recent paper estimated that the loss of ice on the Antarctic Peninsula could contribute up to 22 millimetres to sea level increases by 2100 and up to 172 millimetres by 2300

Previous studies have estimated that the collapse of the Thwaites Glacier could cause global sea levels to rise by a whopping 2.1ft (65cm).

Likewise, the Pine Island Glacier, which currently makes up 25 per cent of ice loss from Antarctica, could cause global sea levels to rise by 1.6 feet (0.5 metres).

The researchers believe that these areas are seeing more dramatic changes because they are the most exposed to the impacts of global warming.

Professor Rignot says: ‘Where warm ocean water is pushed by winds to reach glaciers, that’s where we see the big wounds in Antarctica.’

What is harder to explain is why the satellite data also shows significant ice loss at multiple points in the Northeast of the Antarctic Peninsula.

‘A lot of these places have warm ocean water in proximity, but on the east coast of the peninsula, there’s substantial retreat, and we don’t have evidence for warm water,’ says Professor Rignot.

‘Something else is acting – it’s still a question mark.’

In this area, several major ice shelves had already collapsed prior to 1996, while many glaciers have shown rapid retreats in the last 30 years.

These include the Hektoria glacier that lost 13 miles (21 km), the Green Glacier losing 10 miles (16 km), and the Evans Glacier, which lost 5.6 miles (9 km).

However, despite these alarming changes, the researchers caution that the situation could be much worse.

Professor Rignot concludes: ‘The flip side is that we should perhaps feel fortunate that all of Antarctica isn’t reacting right now, because we would be in far more trouble.

‘But that could be the next step.’