February 6, 2023

La Ronge Northerner

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Mysterious white clouds keep appearing near the Bahamas, and no one knows why: ScienceAlert

The piece of ocean wedged between Florida and the Bahamas is one of the most well-studied marine environments in the world, yet it’s also the center of an enduring geological puzzle.

Since at least the 1930s, scientists in the area have noticed strange white clouds rising up in the calm surface of the turquoise water.

This strange phenomenon is called the “albedo event,” and scientists still don’t understand why it happened in the Bahamas.

It has become a kind of “white whale” for researchers at the nearby University of South Florida (USF).

Satellite images from 2015 of spawning events in the Bahamas. (NASA Earth Observatory/Joshua Stevens, using USGS data)

Mysterious patches of light-colored ocean are sometimes seen in other oceans and lakes around the world, but in the Bahamas, they appear more often than usual.

Direct sampling of cloudy water indicates that it contains high concentrations of carbonate-rich particles.

Much of the Bahamas archipelago lies on a submerged carbonate platform known as the Bahamas Banks. Does this mean that sediment is rising to the surface? Or could it be that phytoplankton blooms actually produce the suspended matter?

No one knows the answer to these questions, but scientists at the University of South Florida are determined to find out. They used satellite imagery from NASA to show how albedo events ebb and flow in the Bahamas.

The team doesn’t know if the trends they identified are natural or man-made, but what they do know is that from 2003 to 2020, the magnitude of these albedo events seemed to be related to the seasons.

The largest spots occurred from March to May and from October to December. On average, the white spots were about 2.4 square kilometers per piece. On a clear-sky day, satellite images typically capture about 24 images, covering a total area of ​​32 square kilometers (12 square miles).

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However, between 2011 and 2015, the patches suddenly swelled in size, covering more than 200 square kilometers (77 square miles) of ocean at their peak. However, by 2019, the spots had shrunk again, though never quite as small as they once were.

The results suggest that a 10-year cycle may play a role. But a cycle of what exactly?

“I wish I could tell you why we’ve seen the peak of activity, but we’re not there yet,” Says USF oceanographer Chuanmin Hu.

“We’re already seeing some interesting relationships between environmental conditions, such as pH and salinity and the behavior of winds and currents, but we can’t yet pinpoint the exact mechanical, biological or chemical processes responsible for those peaks in activity.”

More direct field trials are needed, and not just in the Bahamas. Comparing spawning events in other regions can help scientists see what common features they share.

The University of South Florida researchers tested their model on spawning events in Great lakes With initial success, but now those patterns need to be supported on land, or rather, in water.

Some studiesfor example, showed that albedo events occur more in places with muddy sediments.

In addition, it could be that some ocean conditions favor the suspension of sediment and calcium carbonate in the water column. As mentioned earlier, recent satellite data indicates that white spots in the Bahamas are most common in the spring and winter, which is when the Florida currents that run from north to south shift.

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Without further evidence, all of these theories will remain that way.

The study has been published in Remote environment sensing.