British scientists have mapped cavities half the size of the Grand Canyon that are allowing warm ocean water to erode the vast Thwaites glacier in the Antarctic, accelerating the rise of sea levels across the world.

Like decay in a tooth, the channels of warm water are melting the ice from below, threatening the stability of a glacier that is larger than Great Britain.

Using an aircraft, ship and robot submarine, the British Antarctic Survey and a US team traced the seabed terrain and the bottom of the ice shelf to measure the gaps that have opened between previously grounded sections of the glacier.

They measured two old cavities that were roughly six miles (10km) across and 800 metres deep, which allow warm water to seep under the ice. These have formed over at least 10,000 years. In addition, they mapped several new, thinner fissures that have branched off from these main trunks amid the warmer temperatures of the past 30 […]