New map of landscape beneath the ice reveals Antarctica is more vulnerable than we thought

Antarctica is more vulnerable than previously thought it has emerged, after the most detailed map yet of the landscape beneath its ice sheet was put together by a team of international scientists led by the British Antarctic Survey (BAS).

Bedmap3 was created using more than six decades of survey data gathered by planes, satellites, ships and even dog-drawn sleds.

It provides a view of the continent as if its 27 million cubic kilometres of ice had been removed, showing the hidden locations of its mountains and canyons, and will help us understand how Antarctica will respond to climate change.

Dr Hamish Pritchard, a glaciologist at Madingley-based BAS and lead author on the study, says: "This is the fundamental information that underpins the computer models we use to investigate how the ice will flow across the continent as temperatures rise. Imagine pouring syrup over a rock cake – all the lumps, all the bumps, will determine where the syrup goes and how fast. And so it is with Antarctica: some ridges will hold up the flowing ice; the hollows and smooth bits are where that ice could accelerate."

The place thought to have had the thickest overlying ice was Astrolabe Basin, in Adélie Land, but a reinterpretation of data reveals it is in fact an unnamed canyon - at 76.052°S, 118.378°E in Wilkes Land, where the ice here is 4,757m thick, which is more than 15 times the height of the UK's tallest skyscraper, the Shard in London.

Attempts to map Antarctica's rock bed date back to 2001. This third effort features more than double the number of previous data points - 82 million - rendered on a 500m grid spacing, with major gaps in our knowledge filled in by recent surveys in East Antarctica, including around the South Pole, along the Antarctic Peninsula and West Antarctic coastlines, and in the Transantarctic Mountains.

A variety of techniques were used, including radar, seismic reflection - sound waves - and gravity measurements.

The outline of deep valleys is better represented, as are places where rocky mountains poke up through the ice and the latest satellite data more accurately records the height and shape of the ice sheet and the thickness of the floating ice shelves that push out over the ocean at the margins of the continent.

A new, continent wide view of grounding lines – places where ice at the edge of the continent meets the ocean and and begins to float - is also provided.

By subtracting the topography from the shape and elevation of the ice above, we learn:

The total volume of Antarctic ice, including ice shelves is 27.17 million cu km
The total area of Antarctic ice, including ice shelves is 13.63 million sq km
The mean thickness of Antarctic ice, including ice shelves is 1,948 m and excluding ice shelves is 2,148 m.

If all Antarctica's ice melted, global sea levels could rise 58m.

Peter Fretwell, mapping specialist and co-author at BAS, says: "In general, it's become clear the Antarctic Ice Sheet is thicker than we originally realised and has a larger volume of ice that is grounded on a rock bed sitting below sea-level. This puts the ice at greater risk of melting due to the incursion of warm ocean water that's occurring at the fringes of the continent. What Bedmap3 is showing us is that we have got a slightly more vulnerable Antarctica than we previously thought."

The results were published on 12 March in the journal Scientific Data.