An unusual phenomenon was discovered by scientists who have been studying the behavior of the Ross Glacier in Antarctica for many years. The winds blowing constantly in this area of the mainland cause the snow and ice to vibrate and generate almost constant "sounds" that geophysicists can use to remotely monitor the state of the glacier.
The Ross Ice Shelf is the largest ice shelf in Antarctica, it is located in the Ross Territory and juts out into the Ross Sea of the same name. It was discovered by the expedition of James Clark Ross in January 1841. This glacier is fueled by ice coming from the Transantarctic Mountains, propping up the surrounding continental ice and preventing them from sliding into the ocean, acting like a cork in a bottle.
Against the backdrop of global warming, scientists are constantly monitoring various Antarctic glaciers, tracking their movement, thickness and behavior. As part of the study of the properties of the Ross glacier, American scientists installed 34 ultrasensitive seismic sensors under the surface of the snow, they allowed polar explorers to track the vibrations of the glacier, study its structure and movements for more than two years - from late 2014 to early 2017.
Ice shelves are covered with a thick layer of snow, the thickness of which sometimes reaches several meters. Its surface is often covered with massive dunes like those found in sandy deserts. The top layer of snow serves as a kind of fur blanket for the underlying ice, protecting it from heat and preventing it from melting in especially warm seasons.
When it came time to analyze the collected data, scientists discovered a strange effect - the surface of the snow constantly creates vibrations. They found that close to the most massive dunes, the snow cover creates something that resembles a crash, or the impact of a huge drum. By accelerating the recorded vibration, the scientists synthesized a sound that might remind someone of the voice acting for horror films.
It has been observed that the nature of the vibrations is subject to change when the conditions in which the snow surface is found change. The vibration frequency changes if snow dunes are rearranged during strong storms, and if the surface temperature changes, which affects the change in the transmission rate of seismic waves.
“It's like playing the flute all the time,” explained Julienne Chapieu, a geophysicist at the University of Colorado and author of the study published in Geophysical Research Letters, which is published by the American Geophysical Union. Just as musicians can change the tone and timbre of a flute by forcing air to pass through different openings, natural conditions can change the vibration frequency, depending on the different topography of the dunes, Chapieu explained.
Promotional video:
Scientists were surprised that in January 2016, warming led to a decrease in vibration tone, indicating partial thawing of snow and ice below the surface, slowing the speed of seismic waves propagating through the firn fields.
Even more interesting, the vibration frequency did not increase after the temperature went down again - this indicates the presence of both reversible and irreversible factors in this “game”. “The melting of firn is often seen as one of the most important factors in the destabilization of the ice shelf, which leads to an acceleration of the flow of ice into the ocean from the surrounding areas,” the researcher explained.
According to scientists, the Ross Glacier is located in the western part of Antarctica, which is subject to accelerated melting processes due to the characteristics of the underlying rocks, which allow warm ocean currents to "cut" floating ice. Glaciologists call this part of Antarctica very unstable.
Scientists estimate that if all the ice and snow contained inside the so-called West Antarctic ice sheet melts, it could lead to a rise in the world ocean level by three meters in the future. This makes it particularly important to be able to remotely monitor the Ross Glacier and track how the firn snow is resisting the rise in temperature, Schapue said. “The response from the ice shelf showed that we can track extremely fine details,” Shapue said.
“We got a tool to monitor the environment and impact on the ice shelf,” she said.