A significant part of the Greenland ice sheet is on the brink of a tipping point, after which accelerated melting would become inevitable even if global heating was halted, according to new research.
Rising temperatures caused by the climate crisis have already seen trillions of tonnes of Greenland’s ice pour into the ocean. Melting its ice sheet completely would eventually raise global sea level by 7 metres.
The new analysis detected the warning signals of a tipping point in a 140-year record of ice-sheet height and melting rates in the Jakobshavn basin, one of the five biggest basins in Greenland and the fastest-melting. The prime suspect for a surge in melting is a vicious circle in which melting reduces the height of the ice sheet, exposing it to the warmer air found at lower altitudes, which causes further melting.
The study shows destabilisation of this ice sheet is under way. Uncertainties in the research meant it might already be at the point of no return, or be about to cross it in the coming decades, the scientists said. However, even if the tipping point was crossed, it did not mean that the entire ice sheet was doomed, they said, because there might be a stable state for a smaller ice sheet.
“We’re at the brink, and every year with CO2 emissions continuing as usual exponentially increases the probability of crossing the tipping point,” said Niklas Boers at the Potsdam Institute for Climate Impact Research, Germany, who conducted the research with Martin Rypdal from the Arctic University of Norway. “It might have passed [the tipping point], but it’s not clear. However, our results suggest there will be substantially enhanced melting in the near future, which is worrying.”
Boers said ice equivalent to 1-2 metres of sea level rise was probably already doomed to melt, though this would take centuries and melting the whole ice sheet would take a millennium. “We would probably have to drive temperatures back below pre-industrial levels to get back to the original height of the Greenland ice sheet,” he said.
“The current and near-future ice loss will be largely irreversible,” he said. “That’s why it is high time we rapidly and substantially reduce emissions from burning fossil fuels and restabilise the ice sheet and our climate.”
The new research examined just one part of Greenland, but Boers said there was no reason in principle that it should be different from other parts of the giant ice sheet: “We might be seeing something that is happening in many parts of Greenland, but we just don’t know for sure, because we don’t have the high-quality data for other parts.”