Mysterious ‘sea swirls’ off Poland’s coast have a surprising explanation

A false-color satellite image shows red land next to the ocean, with green swirls stand out on dark blue ocean. — A false-color satellite tv for pc picture of mysterious slicks on the ocean floor within the Bay of Gdansk in Poland captured by the European Area Company’s Sentinel-2A satellite tv for pc on Could 16, 2018. (Picture credit score: ESA/NASA Earth Observatory)

Scientists have lastly recognized the shocking origin of weird ocean slicks that seem to swirl across the floor of the Baltic Sea — tree pollen.

The mysterious slicks are most prominently seen in a color-corrected satellite tv for pc picture (opens in new tab) captured off the coast of Gdansk in Poland on Could 16, 2018, however they’ve appeared a number of occasions in satellite tv for pc photos in recent times.

Researchers knew that the swirling patterns have been brought on by wind-driven currents and waves transferring the slicks round on the ocean’s floor, however have been not sure precisely what they have been made from. Specialists initially suspected they have been algal blooms or “sea snot” — a slimy substance produced by some plankton.

Nevertheless, in a examine revealed in January within the journal Distant Sensing of Surroundings (opens in new tab), researchers analyzed the reflective properties of the mysterious substance and located that it extra intently resembled pollen from pine timber (Pinus sylvestris). The looks of the slicks and direct observations from native scientists later confirmed that that is what the slicks have been constituted of, researchers wrote.

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Zoomed out satellite image of sea swirls. The land appears red.

The total satellite tv for pc picture captured by the European Area Company. (Picture credit score: ESA/NASA Earth Observatory)

Pine timber are the commonest tree in Poland, making up greater than 55% of the nation’s forests, which in flip cowl just below 30% of the nation’s landmass, in keeping with State Forests Poland (opens in new tab). Nevertheless, it was not beforehand identified that the timber’ pollen was blown to date offshore.

After figuring out the pollen, the researchers regarded again at historic satellite tv for pc photos and famous comparable slicks appeared 14 occasions between 2000 and 2021. The quantity of pollen within the slicks elevated yr on yr, and the slicks have additionally began to seem earlier within the yr, they discovered.

The adjustments in pollen ranges in the course of the examine interval replicate a worldwide development of accelerating pollen ranges introduced on by local weather change.

Swirly pollen slicks shaped by ocean currents.

A better have a look at the pollen swirls additional out to sea. (Picture credit score: ESA/NASA Earth Observatory)

In February 2021, a examine revealed within the journal Environmental Sciences (opens in new tab) revealed that in North America, pollen ranges elevated by 21% between 1990 and 2018, and that the pollen season lasted for round 20 days longer on common.

In accordance with NASA’s Earth Observatory (opens in new tab), these adjustments are the results of further carbon dioxide within the ambiance, which permits crops to supply extra pollen.

Because of pollen’s excessive natural carbon content material, the group believes follow-up research are wanted to completely assess the function it performs in oceanic ecosystems.

“If we will observe pollen aggregation in other places, this will present helpful knowledge for fisheries research,” lead examine writer Chuanmin Hu (opens in new tab), an optical oceanographer on the College of South Florida, informed the Earth Observatory. The info may additionally complement land based mostly pollen detectors in monitoring long run traits that would influence individuals with allergic reactions, he added.

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