A large lake suddenly disappeared in the ice of Antarctica
Australian scientist Roland C. Warner from the University of Tasmania and American researchers from Columbia and California Universities have recorded the rapid formation of a large ice caldera in the place of the Antarctic ice shelf where the lake used to be. The disappearance of a large freshwater reservoir is associated with the formation of cracks, due to which the water flows into the ocean. This is reported in an article published in Geophysical Research Letters.
Researchers analyzed satellite data from NASA’s ICESat-2 observations of the Amery Ice Shelf in eastern Antarctica in June 2019 (midwinter in the southern hemisphere). Tracking the height of the ice allows you to understand how the melt water that forms on the surface of the ice contributes to the formation of cracks and the collapse of glaciers. This process is projected to intensify significantly in the coming decades, with rapid changes in glacier surfaces due to melting not limited to the summer months.
It turned out that in the winter months of 2019, the glacier suddenly formed an uneven, crater-like depression (valley) with an area of 11 square kilometers and a depth of 80 meters in the place where an ice-covered lake with an area of 60 square kilometers used to be. The melt water stored in the natural reservoir dripped through fractured fractures into the ocean beneath the glacier, while the reduced load on the floating ice caused it to rise 36 meters into a bend.
Simulations have shown that changes in altitude correspond to a loss of 0.75 cubic kilometers of water. The following summer, scientists observed a short-term filling of the valley with melt water, which formed a narrow channel 20 meters wide and six meters deep in it.
Hydraulic fractures occur on the small ice shelves of the Antarctic Peninsula, where water melts in summer, seeps into microcracks, and freezes in winter, leading to ice cracking. However, this is rarely seen in glaciers, the thickness of which reaches 1400 meters, like Ameri. The explanation is that in recent decades, the melting of water has been more intense, which leads to the emergence of large and deep lakes. This increases the risk of large-scale fracturing, accelerating ice loss and sea level rise. At the same time, scientists are in no hurry to link the appearance and disappearance of the lake with climate change around Antarctica.
Ice shelves are formed by floating ice or are partially supported by ice. It is believed that the melting of such glaciers cannot lead to a rise in sea level, but this is not entirely true: seawater is 2.6 percent denser than the fresh water that makes up glaciers. Thus, the volume of seawater required to displace the floating ice shelf is slightly less than the volume of fresh water contained in the floating ice. The melting of all the world’s ice shelves will only raise sea levels by four centimeters, but the main threat from melting ice shelves is that it destabilizes the land-based Antarctic ice sheet.