Greenland's annual ice melt has started much earlier and faster than in previous years, with temperatures around 20C warmer than usual for mid-June.
Two billion tonnes of ice were lost in a single day, the Danish Meteorological Institute said, with melting taking place across almost half the world's biggest island.
Real-time data from the US National Snow and Ice Data Center shows the extent of the melting was relatively normal up until the start of June, but has quickly reached near-unprecedented levels.
The dark grey area shows the range half of all measurements over the past 40 years have fallen into, and the light grey, 90 percent.
Ice across the Arctic as a whole is also heading in the wrong direction, set for its lowest level since satellite monitoring began in 1979.
This graph shows the trend over the last four decades towards less and less ice in the polar region.
"It's pretty remarkable how much open water is in that area," Zachary Labe, a climate researcher at the University of California at Irvine, told the Washington Post.
"The melting is big and early," added Jason Box of the Geological Survey of Denmark and Greenland.
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The immediate cause is a large high that's positioned itself over the Danish-owned island. It's so warm, on June 12 the air temperature was above zero - meaning no new freezing could happen at all.
The warm air has pushed cold air to the south, resulting in lower-than-normal temperatures across eastern Canada and the US. When this happens, US President Donald Trump often reiterates his claims climate change is a hoax. He's yet to do that this time around, but in the past has called for global warming to "come back fast", despite scientific consensus it's one of, if not the biggest threat the globe will face in the coming century.
With less ice in the Arctic and Greenland's snow turning to liquid, the continent's ability to reflect heat back into space is weakened, University of Georgia climate researcher Thomas Mote told CNN. This means the rate of melting is likely to speed up as the northern hemisphere summer kicks in.
The biggest melt in recorded history happened in 2012, affecting 97 percent of the sheet.
"We've seen a sequence of these large melt seasons, starting in 2007, that would have been unprecedented earlier in the record," said Mote. "We didn't see anything like this prior to the late 1990s. If these extreme melt seasons are becoming the new normal, it could have significant ramifications around the globe, especially for sea level rise."
The hope is cloudier weather will roll in across Greenland soon.
"If cloudy weather occurs, it would slow down the rate [of melting]," Labe told the Post. "It's really hard to predict."
Greenland's ice sheet is the second-largest in the world, behind Antarctica. If it melted, the world's oceans would rise 7m.