For the first time in recorded history, rain fell on and off for 13 hours on the highest point of Greenland's ice sheet, 3,216 meters (10,551 feet) above sea level, on August 14. The rain lasted for several hours and air temperatures remained above freezing for about nine hours, as reported by the National Science Foundation’s Summit Station.
“Basically, the entire day of Saturday, it was raining every hour that [staff] was making weather observations,” Dr Zoe Courville, a research engineer at the Cold Regions Research and Engineering Laboratory, told The Washington Post. “And that’s the first time that’s been observed happening at the station.”
This is the third time in less than a decade, and the latest date in the year on record, where the temperature was above the freezing point of water and precipitation involved wet snow. Previous melting events took place in 2019 and 2012. Using ice core data, scientists have estimated the last melting event at the ice cap top took place in the late 1800s.
The exceptional temperatures were matched by the exceptional level of rainfall. Scientists estimate that 7 billion tons of water fell over the Arctic island. That’s about one-quarter of what it usually falls in a whole year. And it fell in just one day. It is unclear how much fell at the summit. Given that it has never happened before, the station was not equipped with a rain gauge.
Rain can have major effects on the ice sheet as it contributes to its thawing. And it was particularly strong in the August 14 to 16 period. The rainfall led to a vast melting episode throughout Greenland. The extent of the ice affected peaked at 872,000 square kilometers (337,000 square miles), one of the largest recorded.
“Over most of the ice sheet, meltwater (or rainfall in the upper reaches of the ice sheet) percolates into remaining snow and refreezes; however, in bare ice and water-saturated snow areas near the coast, meltwater (and rainfall) runoff occurs resulting in the ice sheet losing mass. On August 15 2021, the surface mass lost was seven times above the mid-August average,” the National Snow and Ice Data Center scientists wrote in “Greenland Ice Sheet Today.”
“At this point in the season, large areas of bare ice exist along much of the southwestern and northern coastal areas, with no ability to absorb the melt or rainfall. Therefore, the accumulated water on the surface flows downhill and eventually into the ocean.”
The climate crisis has made exceptional events such as this all too common. Just this summer alone there have been hundreds of such episodes across the world.
[H/T: The Washington Post]