After a miserable summer in Britain, signs of a warming climate are currently in short supply. But thousands of miles away, the Arctic is melting quickly. Ice shelves hanging into the sea off Ellesmere Island, Canada, collapsed this year and almost a quarter of the ice cover floated away in huge slabs, carrying ancient ice up to 4,500 years old. The ice shelves will not reform.

The vast icecap floating over the Arctic Ocean also shrank with alarming speed. This icecap naturally comes and goes with the seasons, though. It freezes in winter, reaches its greatest area in March and shrinks during the summer. But this summer’s melt left Ellesmere Island exposed, and the sea-ice that would normally keep the ice shelves hemmed in melted away. The famed Northwest Passage around Canada also opened up, and the Northeast Passage around Russia nearly did the same. With another 2 to 3 weeks of melting left to go, the icecap may shrink even more than last year’s record-breaking ice melt.

There are fears that the Arctic may have reached a point of no return. The brilliant whiteness of the Arctic ice cap is like a giant cooler that bounces sunlight back into space and cools the Arctic Ocean and the surrounding frozen lands. But once that ice has gone, the sea and land warm up. By 2030 the entire Arctic sea ice is expected to disappear for several weeks at a time during the summer. That may be good news for shipping companies eyeing shortcuts between the Atlantic and Pacific oceans. But it is a potential disaster for the climate of the Arctic, and quite possibly could have knock-on effects for the rest of the world.