Greenland's melting ice sheet contributes the world's most to sea-level rise. In a new study, scientists used drones to show how water flows through cracks in the ice, creating dramatic waterfalls – and potentially becoming more unstable.
The report published in Proceedings of the The National Academy of Sciences first deployed drones on Monday to monitor the formation of cracks beneath meltwater lakes in the Greenland Ice Shelf.
"So far, most of the observations are from satellites," said lead researcher. Poul Christoffersen. "That way, we can see what's going on over the ice sheet. Drone observations, however, provide much more accurate information about these sea drainages. "
The team found that through the cracks created caverns or moulins, which are observed by the drones meltwater flows through. Since the ice cover is about one kilometer thick, the flow of water into the Moulins can create the largest waterfalls in the world.
In the summer of 2018, the British researchers took pictures of a meltwater lake on the ice cover. In just five hours, five million cubic meters of water can be dripped off the ice. That's enough water to fill 2,000 Olympic swimming pools.
The water flowed through a mill to the bottom of the ice cover, reducing the volume of the lake by two-thirds. The rapid flow of water from the lake also helped raise the surface of the ice by just over half a meter. This could mean that the water flows in hydrofractures or spaces between the ice sheet and its underground.
When water flows to the bottom of an ice sheet, "it increases the tensions near other lakes and causes more hydrofractures," the scientists wrote. In other words, it can trigger a chain reaction, causing more cracks, loosening the bottom of the sheet and making it even more unstable. This can cause the glaciers to break off the ice cover – especially if they drain quickly. And the researchers say that the type of rapid drainage they observe may be much more common than scientists previously thought.
"It is possible that we have underestimated the impact of these glaciers on the general instability of the Greenland ice sheet," said co-lead author and drone pilot of the study, Tom Chudley in a statement.
Earlier this year, scientists found that Greenland's ice sheet could have reached a turning point when the cool weather periods only melted the ice instead of freezing ice again. In 2012, the ice has lost more than 400 billion tons of ice – nearly four times more than in 2003. Other recent results show that ice melts six times faster  than 1980. And only last summer caused a widespread heatwave to melt the ice sheet with an unprecedented speed and dump one [19459004 12.5 billion tonnes ice ].
As the Earth continues to warm, it becomes increasingly important to see how the Greenland ice sheet will react. To understand their reaction, researchers are now using drilling rigs to investigate how climate change could affect the drainage systems of the ice cover. The vanished lake of last summer, however, is a warning.
"It's rare to actually observe these fast-draining lakes – we were lucky enough to be in the right place at the right time," Chudley said.