Scientists at the University of Michigan (USA) and St. Andrews University (UK) have revealed the possible future of the Thwaites Glacier, also called the Doomsday Glacier because its destruction will provoke a significant rise in sea level, threatening the entire coastal part of humanity. The researchers published their findings in the journal Science.
The catastrophic destruction of the glacier can begin due to the collapse under its own weight of the ice located on the border between the glacier and the ocean. This mechanism, called marine ice-cliff instability (MICI), has been proposed by scientists more recently and arises from the fact that the height of ice rocks is determined by the strength of the ice. As the thickness of the glacier increases upstream, an even higher ice cliff occurs with each collapse (hotel). As a result, a chain reaction of collapse occurs, leading to a catastrophic retreat of the glacier within just one century.
Although MICI is not observed in modern ice sheets, there is evidence that it occurred in ancient times. In a new paper, scientists have demonstrated that, contrary to the instability hypothesis, ice rocks whose height exceeds the maximum allowable level will not always be subject to a chain reaction of collapse. A catastrophe occurs only when the gradient of the ice thickness, which increases as it approaches the shore, exceeds a certain critical limit.
In particular, scientists, taking into account the contribution of ice viscosity, created a computer model of a glacier with an ice cliff height of 800 meters with a ground line (the point of contact with the ocean floor) at a depth of 690 meters, which is comparable to the largest glaciers in Greenland and the Thwaites and Pine Island glaciers in Antarctica. Calving of the surface part of the glacier leads to the appearance of icebergs, but at the same time a huge underwater part of the glacier breaks off and floats up, starting to play the role of support that stabilizes the instability of the ice cliff and slows down the retreat of the glacier.
The situation changes with the change in the slope of the bottom and the speed of the glacier flow. When the critical limit is exceeded, a chain collapse can occur at a speed exceeding tens of kilometers per year. However, even when a catastrophic regime becomes unavoidable, a small amount of pressure exerted by icebergs, sea floating ice, or solder can suspend MICI.
Thwaites Glacier, located in the bay of the Amundsen Sea in West Antarctica, is considered one of those glaciers that are most vulnerable to the chain collapse of rocks. The destruction or weakening of the floating ice shelf due to climate change that currently supports Thwaites Glacier will expose an ice cliff large enough to initiate MICI. The authors of the study showed that, although in this case, a chain reaction of collapse will not occur at first (due to the peculiarities of the bottom topography), climate change will still lead to a gradual retreat of the glacier by several kilometers per year and, consequently, a slow rise in sea level.