By Pete Bursztyn — For the first time ever, rain has been recorded at the summit of the Greenland ice cap.
The rainfall was extensive and seen on both Aug. 14 and 15.
Previous episodes of melting had been noted at the site in 1995, 2012 and 2019, but never before accompanied by rain. (Please note that all were in the last 26 years!)
Ice cores taken near the site showed that there had been a solitary thaw event in the 1800s, but not before that. It is worth keeping in mind that the Greenland Ice Sheet is at the very least 100,000 years old, but likely four to five times older; and this is the first time rain has ever fallen there!
This is “incredible,” largely because the locale is 3216 metres (10,551 feet) above sea level. Even near the equator (Mt. Kenya, Mt. Kilimanjaro), at that altitude snow often falls instead of rain! On those two mountains (I climbed Mt. Kenya five times between 1968-1972), “permanent” snow is found at around 4500 metres (15,000 ft.).
The Greenland rain event was associated with a strong south wind. When such a wind — moisture laden after blowing across ocean water, part of which is the warm Gulf Stream — hits Greenland, it is forced upward by geography. As the warm air rises, its pressure decreases. (At 3000 metres, atmospheric pressure is just 70-percent of the sea level value.) As pressure decreases, the air expands and cools. The wind is also cooled by blowing over Greenland’s immense glacier. Since cool air holds less moisture than warm air, such winds usually cause precipitation.
On icy, high-altitude Greenland, this “always” falls as snow, which eventually compacts into ice, to form its glacier. (There is only a single ice mass, covering virtually all Greenland.) The Aug. 14 –15 event is the first time rain has fallen on Greenland at this altitude! And it appears to be only the fourth time above-freezing temperatures have been recorded in the region. Three of these thaw events happened in the 21st century, and one in the late 20th century.
Ice cores revealed another thaw in the late 19th century, almost a century before temperature was measured near that site.
Is that a sign of climate change? You decide.