Global warming is constantly gnawing away at glaciers, ice shelves and ice caps and is causing large chunks of ice to break off more and more frequently. Not only in Antarctica but also in Greenland the temperature increase is much faster than the global average. The Geological Survey of Denmark and Greenland (GEUS) has now announced further proof of this: At the end of August, a 113 square kilometer section of the Nioghalvfjerdsfjorden ice shelf, also known as the 79N ice shelf, broke off in northeastern Greenland. Satellite images clearly show that the ice block broke into many small pieces.
The Nioghalvfjerdsfjord is about 80 km long and 20 km wide and on it drifts the largest remaining Arctic ice shelf towards the ocean. At its edge the glacier divides into two parts, with a small spur turning directly north. This tributary, called the Spalte Glacier, no longer exists.
Since the survey began in 1999, the ice shelf has lost 160 square kilometers of surface area. Professor Jason Box at GEUS says about the recent disintegration: “We should be very concerned about what appears to be progressive disintegration at the Arctic’s largest remaining ice shelf, because upstream it is the only major Greenland ice sheet ice stream, draining 16 % of the inland ice reservoir”. He further explains: “What makes 79N so important is the way it’s attached to the interior ice sheet, and that means that one day – if the climate warms as we expect – this region will probably become one of the major centres of action for the deglaciation of Greenland”.
The northeast Greenlandic ice flow extends 600 km into the interior of the ice sheet and drains mainly through the two outlet glaciers Nioghalvfjerdsfjorden Glacier and Zachariae Glacier, which has already lost its ice shelf. Now, in two consecutive years, the ice shelf of Nioghalvfjerdsfjorden glacier is decaying at a similar rate.
As currently observed with the Pine Island glacier in Antarctica, the weakening of the ice shelf also reduces the resistance of the ice flow to the ocean and glaciers can flow faster and lose mass, as Dr. Niels J. Korsgaard, researcher at GEUS, explains. “Temperatures in the Arctic are rising faster than the global average. More heat is available from air and ocean to melt away the bottom and surface of ice shelves, and the thinning ice shelves are more susceptible to breaking up. We saw this with Zachariae Glacier, this summer with Milne Ice Shelf in Canada, and now Nioghalvfjerdsfjorden Glacier is losing parts of its ice shelf as well,” says Korsgaard.
“The last few years have been incredibly warm in northeast Greenland. We had very early melt onset in 2019 linked to the heatwave across Europe and Greenland.”Dr. Jenny Turton, polar researcher at the Friedrich-Alexander-University Erlangen-Nuremberg
Acceleration at Nioghalvfjerdsfjorden Glacier
Dr. Anne Solgaard, also a researcher at GEUS, explains that the glacier velocities at the Nioghalvfjerdsfjord glacier derived from a series of satellites have shown significant acceleration over the last decade. “Using almost 30 years of satellite data, we see speed up in the glacier flow over the past decade. It is not only near the current disintegration, but we measure acceleration 80 km upstream where the ice begins to float, indicating a large-scale change to this huge glacier,” says Solgaard.
Professor Box suspects that the Nioghalvfjerdsfjorden glacier could resist longer because it is penned in at its front end by some islands, which gives it a certain stability. Nevertheless, the ice shelf is becoming thinner. He thinks it likely that the glacier will dissolve from the middle, which would be unique.
The connection with the climate
Dr. Jenny Turton, a polar researcher at the Friedrich-Alexander-University of Erlangen-Nuremberg, is studying the effects of a changing climate on the glacier and says: “The last few years have been incredibly warm in northeast Greenland. We had very early melt onset in 2019 linked to the heatwave across Europe and Greenland.”
Observations from local weather stations indicate that air temperatures have been consistently above average air temperatures over the last two years, resulting in extensive melting. “The atmosphere in this region has warmed by approximately 3°C since 1980 and record-breaking temperatures have been observed in 2019 and 2020,” Turton said. “Each summer, water drains from the Greenland ice sheet onto the tongue of the glacier, forming rivers and ponds on the surface. Refreezing of the water in winter creates additional pressure on the floating tongue, which can lead to calving events.” Warmer summers therefore mean an even stronger melting of the glaciers and the ice sheet.
At the same time, the relatively high temperatures also cause the sea ice along the east coast of Greenland to break up and melt more rapidly. In years with less sea ice, it loses its barrier function against the glacier ice, so that calving of the glacier front can occur more often.
Julia Hager, PolarJournal
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