A Mysterious Glow Appeared in Antarctic Waters — And Scientists Finally Explain What’s Happening

Imagine an alien scanning Earth with sci-fi binoculars. At one point in time, he would probably stop, dumbfounded by an enigmatic “turquoise glow” in the middle of a blue patch. In the early 2000s, some satellites installed in space captured exactly this scene, something that has been mystifying scientists for decades. The mysterious entity behind this surreal glow turned out to be this feral lady called the Southern Ocean, whose wild, untamed currents circle Antarctica like a rushing fortress.

Her frigid, dynamic waters dance in towering waves that rise and fall at the rhythms of intense storms, rough sea swells, and stirrings in icebergs. For years, scientists sat in their laboratories, staring at the satellite images, ruminating endlessly over what caused this patch to emit such a dazzling glow. At last, they revealed the cause in a study published in the journal Global Biogeochemical Cycles.

The cause, as it turned out, isn’t some magical party going on in the waters. It is, rather, a fancy concert organized by little swirling microbes that call these polar waters their home. Named “coccolithophores,” these microscopic algae are known for their shiny calcium carbonate shells. As they feed and drift inside the waters, they cast stunning optical effects that scientists studied and stored as unique optical signatures.

The team came to this conclusion from the previous observation of a reflective ring appearing on the rim of Antarctica, which was referred to as the "Great Calcite Belt." The turquoise patch lies just north of this glowing patch. Since the patch is often concealed by agitated seas and dusty clouds, satellite images did not offer adequate evidence of its existence. However, this glow has probably ever since the Southern Ocean started flowing, around 34 million years ago. Today, as the world’s five greatest rivers gather and meet at this ocean, the glowing patch is ever more fascinating to those who study these natural phenomena.

The Southern Ocean has remained a powerful ally in sustaining life on Earth. It soaks up nearly 40% of the planet’s carbon dioxide and is one of the largest carbon pumps in the world, all thanks to these phytoplanktons and biogeochemical creatures. While conducting this study, scientists revealed that the creatures nestling in the calcite belt play a crucial role in the global carbon cycle by concentrating an estimated 30 million tonnes of the organic element each year.

High concentrations of the coccoliths and their fellow microbes increase ocean reflectivity, which was already apparent in what the satellites recorded from up above. But the recorded images weren’t clear evidence that these creatures were the good gremlins behind this emanating glow. The waters here were known to be too cold for these creatures to survive. So oceanographer Barney Balch set forth on a cruise with his colleagues to find out what was going on. He described that there have been only a few sea-truth measurements in the region due to its remoteness, according to a press release.

He boarded a research vessel called Roger Revelle and travelled from Hawaii towards the South Pole, passing through the calcite belt. At this time, the belt’s population was in full bloom. They drilled down the patch with multiple measurements at multiple depths. When they reached the glowing patch, they discovered that it was fringed with billions of alien-looking creatures that eat sunlight to survive, along with their microscopic rivals called diatoms, which are made up of silica glass.

"High-reflectance waters further south of the GCB [great calcite belt] have been regularly observed, but questioned, due to the fact that coccolithophores are not typically found in such cold waters," he and his team wrote in the study, concluding, "Our results suggest that these highly reflective polar waters result from scattering by diatom frustules, not coccolithophores, and have been misidentified as PIC [particulate inorganic carbon] in satellite measurements."

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