Warmest autumn measured on the Greenland Ice Sheet | Polarjournal
A white, endless expanse of ice where it is freezing cold is how most people imagine the Greenland Ice Sheet. But it is not like that everywhere. This year, temperatures were well above average even in the middle of Greenland through December. Image: Dr Michael Wenger

In Central Europe, most people are happy when autumn turns golden. One enjoys once again the warming rays of the sun and the warm temperatures (even if they keep rising in the meantime) before the onset of winter. But things are different in Greenland and a golden autumn is now a warning signal here, especially when the difference from normality is as high as it was this year.

The Danish Meteorological Institute DMI reported 9.4, 7.2 and 5.5 degrees Celsius above the 30-year temperature average at the highest point of the Greenland Ice Sheet for past three months. This meant that temperatures were higher than ever before, the institute said in a press release. Experts also reported higher temperatures for September, October, and November at most other measuring locations. “It could well be a new record for the highest average temperatures in autumn, but the data need to be analyzed in depth before any conclusions can be drawn,” explains DMI’s Caroline Drost Jensen.

In September, all measuring stations reported temperature differences above average. Even in the far north, at Cape Jessup, the temperature was almost 2°C above. But nowhere was the difference from normal temperature as high as in the middle of the Greenland Ice Sheet, as the DMI data show. This continued into October and November. Interestingly, by October, the south and northwestern areas had slipped back below average temperature, a trend that was still evident in the southwest in November. DMI meteorologists also found the reason for the unusual behavior of temperatures: a large area of high pressure over Greenland, which normally forms and leads to temperature inversion, was absent in the fall. This normally leaves cold air near the surface trapped by warmer high-altitude air drifting toward Greenland from the south, making it colder below than above. However, due to the lack of a high pressure system, warm air, reinforced by massive low pressure systems over Canada that pulled warm air from the central Atlantic to Greenland, circulated over the island several times, warming the entire region. which is now only slowly approaching normal temperatures again.

The higher temperatures lead to melting processes at the surface of the ice sheet, which very slightly transport warmer water via glacial moulins into the depths of the sheet, thus slowly transporting the heat to the deeper areas as well. Thus, the ice sheet melts from two sides. Image: Dr Michael Wenger

The temperature changes over Greenland are generally considered to be indicative of the continuous warming of the climate. But DMI experts warn against jumping to conclusions about higher temperatures this fall. “Weather is dynamic and fluctuates from year to year – or season to season,” says Rasmus Anker Pedersen, head of the Commonwealth Climate Division at DMI’s National Center for Climate Research. “So you can’t say that the heat at Summit Station this fall is solely due to climate change. But as average temperatures rise, the likelihood that we’ll see more heat extremes and heat records increases, such as when weather patterns like this year occur.” Another extreme event, just a year ago, was the first rain ever recorded at the highest point of the Greenland Ice Sheet. This had not been just a small shower, but substantial amounts of rain, which, however, could not be quantified due to the lack of measuring equipment. Also at that time, unusually high temperatures prevailed at the site.

Dr Michael Wenger, PolarJournal

Originally planned as an ice core camp, the station on the highest point of the Greenland ice sheet is now an important climate-meteorology research station, where up to 45 people work in summer and five in winter. Video: Inspiraziun Alpina Youtube

Link to the measuring station Summit Station

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