Why are Tidewater Glaciers recovering at an unprecedented rate? Scientists discover a new way

New research shows that the bursting of tiny, pressurized bubbles in underwater ice may explain why water ice is retreating at such an incredible rate. The study found that this fractured ice is melting twice as fast as non-fractured ice, indicating the need to adjust current climate models that do not account for these rates.

Research from Oregon State University has found a possible reason for the rapid retreat of sea ice: the bursting of tiny, pressurized bubbles in the underwater ice.

The results, published recently in the journal Natural Sciencesshows that frozen ice, which is filled with pockets of compressed air, melts faster than bubble-free sea ice or artificial ice that is commonly used to study the rate of melting of sea ice in sea ice.

Tidewater ice is retreating rapidly, the authors say, leading to ice loss in Greenland, the Antarctic Peninsula, and other ice-covered areas around the world.

“We’ve known for a long time that glacier ice is full of bubbles,” said Meagan Wengrove, an assistant professor of coastal engineering in the OSU College of Engineering and the study’s leader. “It was when we first talked about the physics of the process that we discovered that these bubbles can do more than make noise underwater as the ice melts.”

Freezing ice results in dense snow. The air pockets between the snowflakes are trapped in the cavities between the ice crystals as the ice makes its way from the top layer of ice to deep within it. There are about 200 bubbles in every cubic centimeter, which means that ice is about 10% air.

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

Glacier in LeConte Bay near Petersberg, Alaska. Credit: Oregon State University

When the broken ice reaches the surface of the sea, the bubbles burst and make loud pops, he added.

“The presence of pressure bubbles in frozen ice has been known for a long time but no studies have looked at their effect on melting where the ice meets the sea, even though bubbles are known to affect fluid mixing in many processes from industrial to medical,” said Wengrove.

Lab-scale experiments conducted in this study suggest that bubbles may explain part of the difference between the predicted melting rate of sea ice, he said.

“The bursting of those bubbles, along with their buoyancy, powers the ocean boundary during melting,” Wengrove said.

This greatly affects the way ice melt is modeled in climate models, especially those looking north of 40 to 60 meters above sea level—researchers have learned that glacial ice melts twice as fast as ice without bubbles.

“Although we can’t measure the amount of global ice loss from Greenland over the past decade and can see the retreat of individual ice sheets from satellite images, we rely on models to predict the rates of ice melt,” Pettit said. “The models that are currently used to predict ice melt in sea ice and sea ice do not account for bubbles in sea ice.”

Currently, data from NASA About 60% of sea level rise is attributed to meltwater from glaciers and ice sheets, the authors note. A more accurate description of how the ice is melting will lead to better predictions of how quickly the ice retreats, which is important because “it’s much harder for society to plan for a 10-foot rise in water level than it is for a 1-foot rise. increase,” said Wengrove.

“These small bubbles can play a further role in understanding future climate conditions,” he added.

Citation: “Melting of an ice sheet overflowing with air bubbles” by Meagan E. Wengrove, Erin C. Pettit, Jonathan D. Nash, Rebecca H. Jackson and Eric D. Skyllingstad, 7 September 2023, Natural 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 Skyllingstad of the OSU College of Earth, Ocean, and Atmospheric Sciences and Rebecca Jackson of Rutgers University.