Climate Wire | Rising new research reveals that melting glaciers may shrink much faster than scientists previously thought.
Research published in Naturefound that thousands of years ago, European glaciers retreated up to 2,000 feet (over a quarter of a mile) a day in short periods of time. This is the fastest speed ever recorded and much faster than previous studies suggested it was possible.
The discovery may provide new insight into the fate of today’s ice sheets and may suggest that modern-day Greenland and Antarctic glaciers may melt sooner than expected. .
This includes the world’s largest and most ominous glaciers, such as Thwaites, which contains enough ice to raise the world’s sea levels by two feet.
Thwaites shares some characteristics with the rapidly retreating glaciers of old Europe. Part of the glacier rests on smooth, flat bedrock, according to the new stud.
“One of the main pitfalls of our paper is that for a fixed melt rate, different bed geometries have significantly different retreat rates,” said an ice sheet expert at the University of Newcastle, UK. said Christine Batchelor, And she is the lead author of a new study.
The rapid retreat of glaciers occurred thousands of years ago, when the last Ice Age was coming to an end and much of the northern hemisphere was covered in ice.
The study examined the seafloor off the coast of Norway. Towards the end of the last Ice Age, about 15,000 to 19,000 years ago, there was a huge mass of ice. Today, the ice is gone, but evidence remains, such as ridges on the rocky seafloor that mark where ice moved and settled when the glacier melted and shrunk.
By analyzing the amount of space between the ridges, scientists measured how quickly the ice melted and retreated over time.
They found that the fastest retreat rates were in areas where the bedrock was flattest. Researchers suggest it’s simple physics. Ice is less dense than water and is particularly buoyant in these flat areas where sloping bedrock is not pressed against the bottom of the glacier. It floats almost above the ground.
This may have made it easier for the glacier to slide backwards over the bedrock as it melted and collapsed into the sea.
The study also found that the fastest pulses of retreat were short-lived, lasting only days or at most months. losses, contributing significantly to global sea level rise.
The findings add a new layer to scientists’ understanding of the factors that influence glacier retreat. Previously, researchers generally assumed that the highest rates of retreat occurred at locations with steep topography, where the bedrock sloped inland away from the sea, becoming slippery backwards as the ice melted. .
Bachelor says both theories are probably correct, albeit in different ways. Over time, sloping bedrock tends to increase ice loss rates. However, for short periods of time, flat bedrock allows small pulses of very rapid retreat.
Both scenarios can result in significant ice loss. And both become more violent and dangerous the faster the ice melts.
A new study points out that the Norwegian ice likely experienced very high melting rates during bursts of rapid retreat. The faster the melt, the easier it is for the ice to separate from the bedrock, making it easier for the glacier to collapse and retreat.
Melting rates may have been higher than those observed for most glaciers in present-day Antarctica. Still, Batchelor said even Antarctica’s current melting rates, combined with the flattest areas of bedrock, “could result in retreat rates of hundreds of meters per day.”
That’s why they focused on places like Thwaites.
Until recently, Thwaites was retreating at a pace of about a kilometer each year. It is now stable on a bedrock ridge and it is unknown when it will start moving inland again. However, as the glacier moves, it is only 4 km away from areas with relatively smooth, flat bedrock.
Scientists aren’t sure if rapid retreat would occur if a glacier hit the spot. there is a possibility.
Bachelor added that the new findings could help update the computer models scientists use to predict the future of the world’s ice sheets. Improved modeling will help scientists better understand how rapid, short-lived retreat pulses affect glaciers around the world.
Scientists are still unsure about the “broader effects of what happens to the ice sheet after experiencing one of these pulses.” We don’t know if it will stabilize again, or if it could initiate a series of ice dynamic responses that could lead to further losses.”
Reprinted from E&E News with permission of POLITICO, LLC. Copyright 2023. E&E News provides essential news for energy and environmental professionals.
