Who doesn’t love a mysterious signal? Triggered by planet-wide thunderstorms, dark matter machinations, atmospheric wobblings, and who knows what when it comes to the “alien megastructure” star, scientists are overjoyed whenever they stumble across one. Thankfully, then, a brand new enigma has appeared in the skies over Antarctica.
This low-frequency signal, picked up back in 2011 by researchers at McMurdo Station, was causing ripples in the air just above the icy Southern Continent. Occurring at an altitude of between 30 to 155 kilometers (20 to 70 miles), the waves cycle for hours at a time, and are notable for their persistence.
Atmospheric waves can be found all over the world, but most disappear after a while. These waves lingered, and a source could not be initially pinpointed. Writing in the Journal of Geophysical Research: Space Physics, a team from the Naval Postgraduate School (NPS) in Monterey, California think they’ve found an answer.
No, it’s not an alien spaceship buried beneath the ice, but the Ross Ice Shelf. With an area roughly equal to the size of Spain, it’s the largest ice shelf in the world by a considerable margin, and almost imperceptible vibrations caused by ice cracking and ocean wave impacts are making their way up into the atmosphere.
These vibrations could not be directly traced from the ice shelf to the skies, however, so the team used two mathematical models to test out ways in which such icy shakes could permeate all the way up into the atmosphere. Whether the ice is modeled as a smooth slab of solid ice, or as a layered fluid, the researchers successfully replicated the shelf’s ability to create the observed atmospheric phenomenon.
“Even in this simplified description [of the ice], it readily explains the most prominent features of the observations,” lead author Oleg Godin, a professor at NPS, said in a statement. “That's why it goes beyond hypothesis. I would say it's now a theory.”
Despite the fact that these vibrations are quite small, the low air pressure above the Antarctic allows them to become amplified, making them powerful enough to be detected by radar systems. This amplification means that, should climate change continue its inexorable march of doom, we can use these very sensitive signals to determine whether or not the shelf is breaking up or remaining stable.
Although not directly contributing to sea level rise, ice shelves keep glaciers pinned back, and those chunks of ice falling into the oceans definitely push the coastlines around the world back. If the vibrations ramp up to something more akin to a death scream, then, we’ll know that the world’s largest ice shelf is about to literally open the floodgates.
Image in text: The location of the Ross Ice Shelf in Antarctica. Jeandre/AGU