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By Tom Parry, Junior Researcher on Seven Worlds, One Planet

Ice defines the white continent and its surrounding ocean – only 2% of Antarctica is free of it, with ninety percent of the world’s entire stock of ice locked up on the frozen continent. What does the future hold for Antarctica in our warming world?

Antarctica’s ice sheet is now being lost five times faster than in the 1990s, when detailed satellite records began. But Antarctica holds its ice in three different forms, each of which will be affected differently – so here’s your guide to the frozen continent and how it’s being affected by climate change.

Ice sheets

Ice sheets are huge plates of ice that sit on continental land or on the seabed, rather than floating in the ocean. The Antarctic Ice Sheet is the largest single mass of ice on the planet. It covers an area of almost 12 million km² and contains 30 million km³ of ice, 60% of the world’s freshwater. Five kilometres thick in places, it is so heavy that it has pushed down parts of the land it rests on to below sea level.

But even this mighty structure is vulnerable to climate change. The Antarctic Ice Sheet is thinning, and rapidly. In some places, ice has thinned by more than 120 metres. West Antarctica has been by far the most affected – a recent study by 80 polar scientists found that between 2012 and 2017 the region was losing 159 billion tonnes of ice each year, more than twice the rate of the early 2000s and triple that of the mid 1990s.

This is the ice that affects sea level, because it sits above the ocean’s surface. Scientists have calculated that if just the West Antarctic Ice Sheet were to collapse and melt, it would cause a global sea level rise of 3.3 metres.

Ice shelves

Unlike ice sheets, ice shelves float on the ocean surface – but they originate from the land. Ice shelves are fed by vast glaciers of compacted snow which flow out onto the sea and eventually break into icebergs that drift away into the ocean. Ice shelves surround most of Antarctica and the largest, the Ronne-Filchner Ice Shelf, is the size of Spain.

The ice shelves that encircle Antarctica serve a very important role in holding back the continent’s vast ice sheet from falling into the sea. This safeguard is now at risk. Ice shelves are being exposed to both rising sea and air temperatures. Since the 1950s, nearly 35,000 km² of ice shelf has been lost from the Antarctic Peninsula alone. As the ice shelves crumble away, they expose the ice sheets behind them.

Sea Ice

While ice sheets and shelves are long-lived bodies formed from snowfall, sea ice is frozen seawater and fluctuates with the seasons. The Southern Ocean surrounds Antarctica, and in winter as much as 90% of it freezes over. In the following summer months almost all of it melts and the continent’s frozen surface shrinks to half the size.

Southern Ocean temperatures have been increasing year on year, and in 2018 we saw the lowest extent of Antarctic sea ice on record. This is a recent trend, but a worrying one. As the sea ice is lost it exposes the ice shelves, and in turn the ice sheet behind them.

The future of the frozen continent, and the vast stock of ice it holds, is uncertain.