Why are tidal glaciers retreating at unprecedented rates? Scientists discover a new idea

New research reveals that the bursting of tiny bubbles compressed in underwater glacial ice may explain why tidewater glaciers are retreating at remarkable rates. The study found that this bubbling ice melts more than twice as fast as non-bubble ice, suggesting a need to modify current climate models that do not take these bubbles into account.

Research by Oregon State University has discovered a possible reason for the rapid retreat of glaciers that end in the sea: the bursting of tiny bubbles compressed in underwater ice.

The results were recently published in the journal Natural earth sciencesIt suggests that glacial ice, filled with pockets of compressed air, is melting much faster than sea ice without bubbles or the artificial ice typically used to study melt rates at the ocean-ice interface in tidal-water glaciers.

Researchers say tidal water glaciers are retreating rapidly, leading to ice mass loss in Greenland, the Antarctic Peninsula, and other glacial regions around the world.

“We’ve known for a while that glacial ice is full of bubbles,” said Megan Wingrove, assistant professor of coastal engineering in Ohio State University’s College of Engineering and leader of the study. “It was only when we started talking about the physics of the process that we realized that these bubbles might be doing much more than just making noise underwater as the ice melts.”

Glacial ice is caused by snow pressure. Air pockets between snowflakes are trapped in the pores between ice crystals as ice makes its way from the upper layer of the glacier to its depths. There are about 200 bubbles in every cubic centimeter, which means the glacier ice is made up of about 10% air.

“These are the same bubbles that preserve the ancient air that has been studied in ice cores,” said co-author Erin Pettit, a glaciologist and professor in Ohio State University’s College of Earth, Ocean and Atmospheric Sciences. “The tiny bubbles can have very high pressures – sometimes up to 20 atmospheres, or 20 times normal atmospheric pressure at sea level.”

Glacial ice in LeConte Bay

Glacial ice in LeConte Bay near Petersburg, Alaska. Credit: Oregon State University

She added that when the bubbling ice reaches the interface with the ocean, the bubbles burst and create an audible pop.

“The presence of compressed bubbles in glacial ice has long been known but no studies have investigated their effect on melting where the glacier meets the ocean, although bubbles are known to affect fluid mixing in multiple processes ranging from industrial to medical.” said Wingrove.

She said laboratory experiments conducted in this study suggest that bubbles may explain part of the difference between observed and expected glacier melt rates.

“The explosive bursting of those bubbles, their buoyancy, activates the ocean boundary layer during melting,” Wingrove said.

This has huge implications for the way ice melt is incorporated into climate models, especially those dealing with the upper 40 to 60 meters of the ocean, as researchers have learned that glacial ice melts more than twice as fast as ice without bubbles.

“While we can measure the total amount of ice loss from Greenland over the past decade and can see the retreat of each glacier in satellite images, we rely on models to predict ice melt rates,” Pettit said. “Models currently used to predict ice melt at the ice-ocean interface of tidal-water glaciers do not take into account bubbles in the glacial ice.”

Currently, the data is from NASA Researchers point out that about 60% of sea level rise is due to meltwater from glaciers and ice sheets. A more accurate characterization of how ice melts will lead to better predictions about how quickly glaciers will retreat, which is important because “it is much more difficult for a society to plan for a 10-foot increase in water levels than a 1-foot rise.” “Increase,” Wingrove said.

“These tiny bubbles may play a big role in understanding critical future climate scenarios,” she added.

Reference: “Glacier Ice Melting Powered by Burst Air Bubbles” by Megan E. Wingrove, and Erin C. Pettit, and Jonathan D. Nash, and Rebecca H. Jackson, and Eric D. Skellingstad, September 7, 2023, Natural earth sciences.
doi: 10.1038/s41561-023-01262-8

The Keck Foundation, the National Science Foundation and the National Geographic Society funded the research, which also included Jonathan Nash and Eric Skillingstad of The Ohio State University College of Earth, Ocean and Atmospheric Sciences and Rebecca Jackson of Rutgers University.

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