Tidewater glaciers study

As the world's temperatures rise, tidewater glaciers are receding and melting, releasing air trapped in the ice. Scientists can listen to the release of the air and potentially use the sounds to help them gauge the impact of climate change on the ice floes.

SAN DIEGO — Bubbles trapped in ice for thousands of years could be sounding the rise of climate change on Earth, according to new research. Scientists are listening to the ancient air to estimate how quickly glaciers are melting, and the impact on rising seas.

Previous studies show that warming oceans could spell catastrophe for the planet. That’s especially the case should global temperatures rise just 2 degrees Celsius, scientists say. This latest research could provide more insight into such predictions.

“Recording the underwater sounds will open the door to long-term acoustical monitoring of ice loss, and how it is linked to water temperature,” explains study co-author Dr. Grant Deane, from the Scripps Institute of Oceanography, in a statement.

Today, about 10 percent of land area on Earth is covered with glacial ice. Almost 90 percent is in Antarctica, and the rest in the Greenland ice cap. If emissions continue to rise, the current rate of melting is expected to double by the end of the century.

Alarmingly, if all the ice on Greenland melted, it would raise global sea levels by 20 feet. Ice acts like a protective cover over the Earth and our oceans. The bright white spots keep the planet cooler.

The Arctic remains colder than the equator because more of the heat from the sun is reflected off the ice, back into space. As temperatures rise, tidewater glaciers are receding, releasing pressurized bubbles.

The study identifies the “acoustically distinct” underwater noises of air trapped with ice below the glacier surface. It becomes a compressed bubble-ice mixture that builds pressure during the long passage to the end, or terminus, of a glacier. The ice holds bubbles of air that have been frozen in time since before before the pyramids were built. They can be up to 20 atmospheres of pressure –  and generate detectable sounds when they are released as the ice melts.

“We observed the intensity of the sound generated by a melting terminus tends to increase as the water temperature increases,” reports Deane. “This makes sense, because we expect the terminus to melt faster in warmer water, releasing bubbles more rapidly into the ocean and generating more sound.”

The international team discovered as the recording array was moved further from the glacier, the variation in the acoustic melting did not follow a uniform trend. Moreover, the acoustic intensities at different glaciers clustered in different levels.

It indicates the geometry of the glacier-ocean interface, temperature, salt and floating ice affected the measurements. The experiments will permit monitoring of climate change’s impact on glaciers.

“The endgame is to establish long-term recording stations for underwater sound around glaciers such as those in Greenland and Svalbard, to monitor their stability over time,” says Deane.

Svalbard, a land of ice and polar bears between Norway and the North Pole, is home to some of the Earth’s northernmost glaciers. They bury most of the archipelago’s surface under 200 meters of thick ice.

Glaciers can range from ice that is several hundred to several thousand years old. They provide a scientific record of how climate has changed over time, and shed light on how the planet is rapidly warming. When glaciers melt, because that water is stored on land, the runoff significantly increases the amount in the ocean, contributing to global sea level rise.

Since the early 1900s, many glaciers around the world have been rapidly melting due to human activities, calving off into the sea. Even if we significantly curb emissions in the coming decades, more than a third of the world’s remaining glaciers will melt by the end of the century.

The study was presented at a meeting in San Diego of the Acoustical Society of America.

South West News Service Mark Waghorn contributed to this report.

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