Cracking the Surface: Examining the Sudden Movement of Antarctica's Ross Ice Shelf

Sunday - May 26 2024, 13:34 UTC - 5 months ago

New research has found that the Ross Ice Shelf in Antarctica experiences sudden movements of several centimeters, triggered by a slip on an ice stream. This movement, which occurs daily, could play a role in triggering icequakes and fractures. This finding is significant due to the size of the Ross Ice Shelf and its potential impact on sea level rise.

In Antarctica, massive glaciers are constantly shifting. Ice streams, which act like conveyor belts, are the pathways of accelerated movement that transport the majority of the ice and sediment debris from these extensive glaciers towards the ocean. One such ice stream jostles the entire Ross Ice Shelf out of place at least once daily, according to new research from Washington University in St. Louis.

This finding is significant because of the scale of the Ross Ice Shelf: It is the largest ice shelf in Antarctica, about the same size as the country of France. As the Robert S. Brookings Distinguished Professor of earth, environmental and planetary sciences in Arts & Sciences, Doug Wiens explains, "We found that the whole shelf suddenly moves about 6 to 8 centimeters (or 3 inches) once or twice a day, triggered by a slip on an ice stream that flows into the ice shelf. These sudden movements could potentially play a role in triggering icequakes and fractures in the ice shelf." .

The Ross Ice Shelf is a floating lip of ice that extends out over the ocean from inland glaciers. Scientists are concerned about the stability of Antarctica's ice shelves in a warming world, as these shelves act as brakes for glaciers and ice streams, slowing their journey to the sea and allowing more ice to accumulate on the continent. However, if an ice shelf collapses, this support disappears and the glaciers are free to flow faster, contributing to sea level rise.

The new study, published in the journal Geophysical Research Letters, focuses on movement triggered by the Whillans Ice Stream, one of about a half-dozen of the large, fast-moving rivers of ice pouring into the Ross Ice Shelf. "One would not detect the movement just by feeling it," Wiens said. "The movement occurs over a time period of several minutes, so it is not perceptible without instrumentation. That's why the movement has not been detected until now, even though people have been walking and camping on the Ross Ice Shelf since the time of the great explorers Robert F. Scott and Roald Amundsen." .

The movement of the Ross Ice Shelf is triggered by a relatively sudden - in glacial terms - movement of the ice stream called a slip event. This movement is similar to the "stick-slip" process that occurs along a fault before and during an earthquake. In this scenario, a large section of the Whillans Ice Stream, measuring more than 100 km by 100 km, remains stationary while the rest of the ice stream creeps forward. Then, once or twice per day, the large section lurches forward against the Ross Ice Shelf, moving up to 40 cm in a matter of minutes.

Studies of ice streams over the past 50 years show some ice streams speeding up, while others are slowing down. By using seismographs to detect sudden motions of ice streams, scientists are able to gain a better understanding of what controls this movement. Wiens and his team traveled to Antarctica in 2024 to study the sudden movements of the Ross Ice Shelf, providing valuable insights into the dynamics of Antarctica's massive ice shelves and how they may response to future warming.