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- What are you grinning at: The "UZI" of the Arctic ice ridges will make navigation safer
What are you grinning at: The "UZI" of the Arctic ice ridges will make navigation safer
Russian researchers have "taught" ultrasound to "see" through Arctic hummocks — large-scale ice ridges that threaten ships and oil platforms. A new computer method will make it possible to remotely determine the internal structure of such frozen ridges — to identify and classify hidden cavities. The development will increase the safety of navigation and construction in the Arctic. It will also be suitable for assessing environmental changes and long-term monitoring of Arctic ice conditions, experts told Izvestia. However, they note that the technology is more suitable for climate research than for navigation or ocean exploration.
A new method for studying ice ridges
Researchers from MIPT have developed a computer method that allows "probing" Arctic ice hummocks, that is, piles of ice fragments, with ultrasound. Numerical modeling has shown that by the nature of reflected acoustic waves, it is possible not only to detect hidden cavities inside these lumps, but also to determine what they are filled with: air or water.
Figure 1 Arctic ice hummock. The surface part ("sail") is only the visible tip, the bulk of the ice goes under water ("keel"). Inside, the hummock is riddled with cavities
The Arctic is changing faster than humanity has time to understand the processes taking place there, scientists told Izvestia. Over the past decades, the area of sea ice in the region has significantly decreased, and at the same time, the nature of ice formations has changed, primarily hummocks.
A hummock, or ice ridge, occurs where two ice fields collide: one sheet of ice creeps over the other, forming uneven piles that go both up, forming a surface "sail", and down, forming an underwater keel. The height of the surface part can reach several meters, and underwater — dozens. Such structures are becoming the main threat to ships, underwater pipelines and offshore platforms that develop Arctic hydrocarbon deposits.
In order to safely lay routes and build underwater infrastructure, engineers need to know not only the shape of the hummock from the outside, but also what is hidden inside. Ice is far from a monolithic material. Cavities filled with air or water can hide inside it. It is almost impossible to detect such hidden structures by looking only at the surface of the boulders. Ultrasound can help here, the scientists said.
The source sends an acoustic pulse, the wave propagates through the medium, reflects off the interface of materials with different physical properties, and returns to the receivers. By the nature of the reflected signal, it is possible to judge the internal structure of the object. An ultrasonic wave entering an icy environment behaves quite differently than in water: ice is an elastic body capable of transmitting not only longitudinal (compression), but also transverse (shear) waves. A correct description of such a system requires fundamentally different mathematical tools than those used in conventional acoustics.
Figure 2 The Arctic ice is changing. Modern satellite observations indicate that Arctic sea ice is becoming thinner and losing its long-term character. Nevertheless, hummocks remain the main danger to shipping and underwater structures, which is why their accurate ultrasound diagnostics are becoming increasingly valuable.
The scientists applied the grid-characteristic method. Its key advantage is that it is based on the physical properties of hyperbolic equations describing wave propagation in elastic bodies. The method "knows" how waves behave at the interface of media, and accurately reproduces these transitions.
— A hummock is a complex three—dimensional structure with an unpredictable internal structure: cavities, layers of different densities, cracks. Our method allows you to look inside without destroying the object or going out onto the ice with drilling equipment. We have shown that the ultrasonic signal carries the imprint of this structure, and we have learned to read it using numerical modeling," said Alyona Favorskaya, a leading researcher at the Laboratory of Applied Computational Geophysics at MIPT.
According to her, the next step is to create systems that will automatically build digital doubles of hummocks based on onboard sensors and warn the crew about dangerous objects on the route.
Where will UZI be used for hummocks?
Scientists have shown that their approach makes it possible to build digital doubles of hummocks and generate training samples for neural networks that solve the opposite problem: restoring the internal structure of an ice structure based on a set of seismograms. Using such data, it is possible to train a neural network to recognize a structure based on a signal, and then apply it to real field measurements, the MIPT noted.
The value of the proposed method lies in the ability to distinguish the nature of cavity filling by the wave response: gas, liquid, solid, said Sergey Mishurov, professor of the Department of Engineering Cybernetics at NUST MISIS. This opens up the possibility of its wider application for non-destructive testing tasks. For example, composite materials are used in aviation, in medical diagnostics, for modeling damage in bone structures, and in geotechnics to assess the condition of frozen soils.
— When creating real ice monitoring systems, such methods can be combined with remote sensing of ice fields to identify potentially dangerous areas. For example, using fractal analysis proposed at the NUST MISIS Department of Engineering Cybernetics in 2023," he explained in an interview with Izvestia.
The idea itself is physically sound: acoustics really allows you to "see" the internal structure of the ice and distinguish what the cavities are filled with, said Maxim Barkasov, an expert at MariNet NTI and a leading specialist at the Russian University of Transport.
— But in terms of its content, this is primarily an applied task for assessing environmental changes and long-term monitoring of the state of Arctic ice. From the point of view of practice, it falls more into scientific and climate research than into the tasks of navigation, ocean exploration or robotics," the expert noted.
In terms of physical feasibility, the proposals of MIPT specialists are of interest, Konstantin Abbakumov, professor of the Department of Electroacoustics and Ultrasound Technology at St. Petersburg State Technical University LETI, told Izvestia.
— However, for the practical implementation of the proposal, it will be necessary to resolve the issues of how to excite and receive ultrasound in an ice field. In addition, in addition to the Arctic ice, there are ice floes in Antarctica that have completely different geometric characteristics," the expert noted.
The work was published in the journal Mathematical Models and Computer Simulations and was supported by the Russian Science Foundation.
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