Fiber Optics Can Map Ice Sheet Temperatures In Unprecedented Detail
Fiber-optic cable (red) installed in a 1-kilometer-deep borehole drilled on Greenland's Store Glacier. (bottom left image). A scientist is installing a fiber-optic cable in the Greenland Ice Sheet. (top left image). A researcher inspects a large fracture in the Greenland Ice Sheet. (image on the right) (Image credits: Poul Christoffersen and RESPONDER team. Photo collage by Andrea Steffen)
Environment Nature Science Technology

Fiber Optics Can Map Ice Sheet Temperatures In Unprecedented Detail

Monitoring changes in vast masses of ice is paramount to comprehend the effects of climate change on the planet. So, scientists developed a new tool that takes measurements to unprecedented levels of accuracy. They have obtained the most detailed measures of ice properties ever taken on the Greenland Ice Sheet using fiber-optic sensing.

The technology uses a mix of fiber-optic cables and laser pulses to gain exact temperature readings from the very top of the Greenland Ice Sheet to the very bottom, offering a clearer image of the changes occurring throughout Earth’s second-largest ice sheet.

The University of Cambridge led the research team that used the new technique for the first time. They gathered detailed temperature readings through the ice sheet’s surface most of the way to the bed base over 1,000 meters down.

Unlike previous studies that measured temperature from separate sensors located tens or hundreds of meters apart, the new approach takes measurements along the entire length of a fiber-optic cable installed in a deep borehole.

Robert Law, a Ph.D. candidate at the Scott Polar Research Institute and first author of the study, said:

With typical sensing methods, we can only attach about a dozen sensors onto the cable, so the measurements are very spaced out. But by using a fiber-optic cable instead, essentially the whole cable becomes a sensor so that we can get precise measurements from the surface all the way to the base.

Fiber Optics Can Map Ice Sheet Temperatures In Unprecedented Detail
A complete temperature profile of Greenland’s Store Glacier. (Credit: Robert Law and RESPONDER team)

The technology reveals temperature by analyzing the varying distortions into the scattered light as it encounters the surrounding ice. The result is a highly detailed profile of temperature.

This information is precious because temperature controls how fast ice deforms and how fast the ice sheet flows. Researchers can use the data to make more accurate models into the future motion of the world’s second-largest ice as the impacts of climate change continue to speed up.

Understanding how the ice is moving and the thermodynamic procedures beneath the area will enable researchers to model the melting process more accurately and better prepare for the future. As study co-author Dr. Poul Christoffersen stated:

The more precise data we can gather, the clearer we can make that picture, which in turn will help us make more accurate predictions for the future of the ice sheet.

This new tool is already reshaping what scientists know about heat distribution in ice sheets. Scientists thought the distribution resembled a smooth gradient, with the warmest points found at the top where sunlight strikes and at the underside because of geothermal energy and the subglacial landscape friction. Instead, the researchers found areas of highly localized hot spots at boundaries between ice of different types and ages, driven by deformations.

Christoffersen said:

Overall, our readings paint a picture that’s far more varied than what current theory and models predict. We found temperature to be strongly influenced by the deformation of ice in bands and at the boundaries between different types of ice. And this shows there are limitations in many models, including our own.

 

With these observations, we are starting to understand better why the Greenland Ice Sheet is losing mass so quickly and why discharge of ice is such a prominent mechanism of ice loss.

The reasons behind the deformations aren’t yet known. Still, the team suspects it could be due to dust trapped from ancient volcanic eruptions or large fractures that penetrate several hundred meters below the surface of the ice.

Fiber Optics Can Map Ice Sheet Temperatures In Unprecedented Detail
Science camp and drill site on Greenland’s Store Glacier. (Credit: Timo Lieber)

Since the 1980s, mass loss from the Greenland Ice Sheet has increased sevenfold, and it’s now the single most significant factor contributing to global sea-level rise. Approximately half of this mass loss is from surface meltwater runoff, while the rest is driven by the release of ice straight into the ocean by fast-flowing glaciers that reach the sea.

One of the limitations in our understanding of climate change is how little we know about the behavior of glaciers and ice sheets. But the new data from this team’s research will allow scientists to improve their models of how the Greenland Ice Sheet is moving now, how it may move in the future, and what effect will have on global sea-level rise.

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