Global warming is starting to penetrate even the deepest parts of our oceans.
While the surfaces of those vast bodies of water have absorbed the overwhelming majority of human-induced warming, as seawater circulates, the worrisome changes are slowly making their way downward.
Scientists at the US National Oceanic and Atmospheric Administration (NOAA) have now detected a warming trend in a number of the deepest parts of the southern Atlantic.
Analysing ten years of temperature recordings within the Argentine Basin from 2009 to 2019, researchers found all four sites warmed somewhere between 0.02 to 0.04 degrees Celsius, betting on the depth.
One of the recording devices was located 4,757 metres (15,600 feet) below the waves, and it experienced a surprising amount of variability over the course of a year.
"In years past, everybody wont to assume the deep ocean was quiescent. There was no motion. there have been no changes," explains oceanographer Chris Meinen, who works for NOAA.
"But when we go look we discover that the ocean is more complex than we thought."
Part of that mystery needs to do with location. The deep ocean is, well, deep - which implies obtaining world data is sort of the challenge, especially long-term data.
However, recent estimates supported some measurements and climate models have predicted that some parts of the deep ocean are growing warmer because the ocean circulates and turns over the water.
The Southern Ocean, which is comparatively well-ventilated, was found to experience these changes even more quickly than the Northern Ocean. Now, data from South American nation Basin located off the coast of Uruguay suggest things are certainly moving quickly down south.
Four devices, moored to the underside of the basin, have revealed hour-by-hour, year-by-year data on what's actually occurring one metre off the seafloor.
At the shallower depths of 1,360 and 3,535 metres (4,460 feet and 11,600 feet), temperatures fluctuated way more than scientists were expecting, and while these changes were somewhat smaller at even deeper levels, their overall pattern matches what's occurring at the surface.
How that may ultimately impact ecosystems or weather above the waves remains unknown, but given how important ocean circulation and temperature is for our global climate system, it isn't exactly excellent news.
Still, there are some positives to the present study. Submerged devices, moored on the deep ocean bottom, are usually accustomed collect data on deep ocean currents, but Meinen and his colleagues recently realised they were also equipped with temperature sensors.
The sensors had been recording the temperature this whole time, and it's allowed the team to achieve unprecedented insight into the super-deep, whether or not just for a decade of warming.
"There are a variety of studies round the globe where this type of knowledge has been collected, but it's never been checked out," says Meinen.
"I'm hoping that this is often visiting cause a reanalysis of variety of those historical datasets to undertake and see what we are able to say about deep ocean temperature variability."
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