Greenland summit, for the first time on record, saw rainfall on Friday instead of snow roughly two miles above sea level.
Also, temperatures at the Greenland summit over the weekend rose above freezing for the third time in less than a decade, reports CNN.
The warm air fueled an extreme rain event that dumped 7 billion tons of water on the ice sheet.
It was the heaviest rainfall on the ice sheet since record keeping began in 1950, according to the National Snow and Ice Data Center, and the amount of ice mass lost on Sunday was seven times higher than the daily average for this time of year.
According to Colorado University NSIDC Research Scientist Ted Scambos, this is evidence Greenland is warming rapidly.
National Science Foundation Summit Station, located at the highest point on the Greenland ice sheet, observed the rainfall.
The majority of the weekend's rain fell from the southeast coast of Greenland up to the Summit Station.
Jennifer Mercer, program officer for the Office of Polar Programs at the National Science Foundation, said because of the significant rain event, operations at the Summit Station would need to change.
"Increasing weather events including melting, high winds, and now rain, over the last 10 years have occurred outside the range of what is considered normal," Mercer said.
A recent study published in the journal Cryosphere found Earth has lost a staggering 28 trillion tonnes of ice since the mid-1990s, a large portion of which was from the Arctic, including the Greenland ice sheet.
In July, the Greenland ice sheet experienced one of the most significant melting events in the past decade, losing more than 8.5 billion tons of surface mass in a single day.
According to Mercer, the rain will have a lasting effect on the properties of the snow, leaving a crust of ice behind that will absorb more energy from the sun until it gets buried by snow. Scambos said this crusty layer will also be a barrier that prevents the downward draining of melt water, which will then flood the surface of the ice sheet and initiate run off at higher elevations.
Because of the layer of ice it created, the weekend's rainfall event "will be visible in ice core records in the future," Mercer said.