The Largest Antarctic Ice Shelf is Acting Unusually
In Antarctica, massive glaciers are constantly shifting, with ice streams acting like conveyor belts that transport most of the ice and sediment debris from these glaciers to the ocean.
According to new research from Washington University in St. Louis, one such ice stream displaces the entire Ross Ice Shelf at least once daily. This is significant because the Ross Ice Shelf, the largest in Antarctica, is about the size of France.
Doug Wiens, the Robert S. Brookings Distinguished Professor of earth, environmental, and planetary sciences, explained that the whole shelf suddenly moves about 6 to 8 centimeters (3 inches) once or twice a day due to a slip on an ice stream feeding into the shelf. These movements might trigger icequakes and fractures in the shelf.
The Ross Ice Shelf is a floating expanse of ice extending over the ocean from inland glaciers.
Concerns About Ice Shelf Stability in a Warming World
Scientists are concerned about the stability of Antarctica’s ice shelves in a warming world because ice shelves act as brakes for glaciers and ice streams, slowing their flow to the sea. If an ice shelf collapses, glaciers can flow faster into the ocean, contributing to sea level rise.
The study, published in Geophysical Research Letters, focuses on the movement triggered by the Whillans Ice Stream, one of several large, fast-moving ice streams feeding into the Ross Ice Shelf.
Wiens noted that this movement, occurring over several minutes, is imperceptible without instruments, which is why it hadn’t been detected until now despite human presence on the shelf since the era of explorers Robert F. Scott and Roald Amundsen.
The movement of the Ross Ice Shelf is caused by a relatively sudden slip event in the ice stream, akin to the “stick-slip” phenomenon that happens along a fault before and during an earthquake.
Observations of the Whillans Ice Stream Dynamics
Wiens and his team observed that a large section of the Whillans Ice Stream, over 100 km by 100 km, remains stationary while the rest of the ice stream moves forward slowly. Then, once or twice daily, the large section suddenly lurches forward against the Ross Ice Shelf.
This section can move up to 40 cm (16 inches) in a few minutes, Wiens noted.
Studies of ice streams over the past 50 years show variable behavior, with some speeding up and others slowing down.
Scientists use seismographs to detect the sudden motion of the ice streams to understand what controls this movement. Wiens and his team traveled to Antarctica in 2014 to deploy the seismographs used in this study.
“I’ve published several papers about the Whillans Ice Stream slip events in the past but had not discovered that the whole Ross Ice Shelf also moves until now,” Wiens said.
Slip Events Unlikely Linked to Human-Caused Global Warming
The researchers do not believe these slip events are directly related to human-caused global warming. One theory suggests they result from the loss of water in the bed of the Whillans Ice Stream, making it more “sticky.”
The stress and strain associated with slip events are similar to those that trigger icequakes under different conditions.
“Icequakes and fractures are just part of the normal life of the ice shelf,” Wiens said. “There is a concern that the Ross Ice Shelf could disintegrate someday, as smaller and thinner ice shelves have done. We also know that the Ross Ice Shelf disintegrated during the last interglacial period about 120,000 years ago, causing rapid ice loss from the other glaciers and ice streams feeding into it.”
Read the original article on: Scitech Daily
Read more: CO2 Drop Tied to Earth’s Severe Ice Age
