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Researchers can finally know why some icebergs are light green

A green iceberg discovered in the Antarctic Weddel Sea in 1985. Photo: AGU / Journal of Geophysical Research In the 19th century English ballad The Ancient Mariner a storm drives a sailing ship against the South Pole , where he meets all the amazing sights, including floating icebergs "as green as emerald". It may sound like author Samuel Coleridge took a certain poetic license, but emerald-colored icebergs are a real thing – and more than 200 years after the ballad was blotted out, researchers can know what causes them. A recent study published in the Journal of Geophysical Research: Oceans reflects the long-standing mystery of green icebergs, which sea captains have reported for nearly a century if not longer. While early work by the same author suggested green icebergs got their color from coal, new data made them change their minds. Now they suspect that iron oxide minerals are responsible for dying "the rocks" to look like they're ready for a St Patrick's Day party. If true, these harsh mountains can represent an important source of a crucial nutrient for the great southern ocean that surrounds Antarctica. "There is a great interest in where the iron comes from," Earther, senior study author Steve Warren, a geophysicist and emeritus professor at the University of Washington told. "If it can get into the marinis, these" mountain voyages can travel hundreds of miles. "Warren's experience of green icebergs dates back to 1988 when he joined an Australian expedition to Antarctica as part of…

A green iceberg discovered in the Antarctic Weddel Sea in 1985. Photo: AGU / Journal of Geophysical Research

In the 19th century English ballad The Ancient Mariner a storm drives a sailing ship against the South Pole , where he meets all the amazing sights, including floating icebergs “as green as emerald”. It may sound like author Samuel Coleridge took a certain poetic license, but emerald-colored icebergs are a real thing – and more than 200 years after the ballad was blotted out, researchers can know what causes them.

A recent study published in the Journal of Geophysical Research: Oceans reflects the long-standing mystery of green icebergs, which sea captains have reported for nearly a century if not longer. While early work by the same author suggested green icebergs got their color from coal, new data made them change their minds. Now they suspect that iron oxide minerals are responsible for dying “the rocks” to look like they’re ready for a St Patrick’s Day party.

If true, these harsh mountains can represent an important source of a crucial nutrient for the great southern ocean that surrounds Antarctica.

“There is a great interest in where the iron comes from,” Earther, senior study author Steve Warren, a geophysicist and emeritus professor at the University of Washington told. “If it can get into the marinis, these” mountain voyages can travel hundreds of miles. “Warren’s experience of green icebergs dates back to 1988 when he joined an Australian expedition to Antarctica as part of his first Sabbath day. happiness “when the crew reached the Mawson research station on the west side of East Antarctica’s Amery Ice Shelf, they ended up near a rather striking iceberg that had become trapped in the sea.

A partially nested iceberg including deep blue marinis and white ice. Photo : Collin Roesler

The iceberg, Warren explained, was jade green and remarkably clear, its clarity telling the researchers that they were dealing with marinis or ice forming from sea water that freezes at the bottom of a floating ice shelf. over land by stumbling is opaque thanks to the presence of countless air pockets, marinis do not contain light-reflecting air bubbles that make it

Usually, the ice absorbs a deep blue color that reflects the distance photons of light must travel before they are absorbed. It was obvious that something else was present in this jade-colored mountain. The samples of the iceberg were collected, analyzed in the lab and found to contain dissolved organic matter (DOM), which can produce green and yellow colors along the coasts as rivers dump small pieces of organic matter into the sea. And so the researchers predict that the DOM was responsible.

But in 1996 a new wrinkle came on that story, when Warren returned to another part of Amery Ice Shelf for his second Sabbath day and again faced a glacier of unusual shade. This was a chimera of blue, green and yellow-green marinis forgotten on white ice. When “the mountain was analyzed for the DOM, both the green and blue ice were found to contain similar levels, indicating that something else was responsible for the color difference.”

“It was a worrying concern we didn’t know what to do about it until two years ago, a paper came out of Tasmania showing huge amounts of iron” in marinis collected from the bottom of a borehole, Warren explains.

Warren and his colleagues now predict that iron oxide minerals are the culprit behind the green icebergs they have encountered. If it is true, the iron-bearing minerals are probably the result of “ice-cream”, basically dust formed by the erosion of the bedrock.

Scripps Department of Oceanography Glaciologist Helen Amanda Fricker, who studied Amery Ice Shelf’s marine ice as part of her doctoral work and has encountered Emerald Mountain itself, said the new paper offered a “possible, credible mechanism” for their staining.

“The ice hillock [that forms marine ice] has come from the ground line,” Fricker said, referring to the point where a glacier appears in the bedrock that is bound to and becomes a floating ice shelf. “Many of it probably has sediment in it.”

Still more research is needed to be sure that these giant popsicles are iron-flavored. Warren said he and his colleagues submitted a proposal to return to Amery Ice Shelf in search of more Jadebergs next spring. He is hopeful of his potential value – as a kind of dietary supplement that supports the Southern Ocean food chain. Helps the group secure a grant.

After all, it is a climate change impact on the number of green icebergs out there can have far-reaching consequences.

“The reason why we can get funding [is] they can actually be important,” Warren said.

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