Across the Northern Hemisphere, more than 1,700 glaciers touch the ocean. Many of these glacier fronts are floating, with some spreading out into wide, flat ice sheets. Others are grounded, connected to the seafloor. Most of them are retreating.
This is the conclusion of recent research by Luke Copland and William Kochtizky, glaciologists at the University of Ottawa. Using Landsat and Terra satellite images, the researchers outlined the position of each glacier front in 2000, 2010 and 2020. They found that 85 percent of the glaciers had retreated during these two decades, resulting in a total loss of about 7,500 square kilometers of ice.
Most of the losses (62 percent) come from outlet glaciers along the periphery of Greenlands massive ice sheet. The greatest loss was in northeast Greenland which lost 1,453 square kilometers of ice between 2000 and 2020.
“The changes at Zachariae Isstrøm in Greenland are incredible,” said Kochtitzky. “It lost 73 square kilometers per year. That is nearly six times more than the glacier with the second-most area loss.”
“Marine-terminating glaciers and ice shelves outside of Greenland are also losing ice. For example, the collapse of the Matusevich Ice Shelf in the Russian Arctic was the largest contributor to losses in the Northern Hemisphere outside of Greenland.
A collapse can be triggered by ocean temperatures and warm air, which melt a shelf from above and below, causing it to thin and weaken. During periods when there is less sea ice adjacent to the shelf, the glacial ice becomes exposed and vulnerable to sea waves.
Each marine-terminating glacier in the world advances and retreats under unique conditions, depending on factors like contact with the seafloor or the shape of the fjord. Still, the study indicates a clear pattern across the Northern Hemisphere. “In all, 123 glaciers that ended in the ocean in 2000 now end on land,” said Kochtitzky.
https://earthobservatory.nasa.gov/images/149670/northern-glaciers-are-retreating-from-the-water