The results of their paper were widely reported on at the time, but their victory lap was short-lived. This time, they could properly sample the dissolved organic carbon, and found that the amounts in the blue and green marine ice were not only similar, but also too small to have any effect on the apparent color. Then, in , a study led by physical oceanographer Laura Herraiz-Borreguero —then at the University of Tasmania and now at the University of Southampton—serendipitously found the missing piece of the puzzle.
Within several Amery Ice Shelf cores, the marine ice contained up to times more iron compounds than the glacial ice sitting above it. The resulting powdery sediment, so-called glacial flour, eventually made its way into the sea, where the rusty substance occasionally froze to the base of ice shelves and found itself locked into marine ice that ultimately broke off and formed icebergs. As it happens, iron oxides tend to be yellowy-red. In his recent study, published in the Journal of Geophysical Research: Oceans , his team calculated how much iron you would need to shift the color of ice from blue to green, and they found that the amount in the Amery marine ice was sufficient.
This conveyor belt of green icebergs has some important consequences for the environment down there, Lea adds. Glacial grounding lines, where glaciers go from sitting on bedrock to floating on the sea, have been retreating all around Antarctica in recent times.
This migration can cause the ice shelves in front of them to destabilize and fragment, potentially unleashing armadas of jade bergs. In other words, algae hanging out near the Amery Ice Shelf might be getting the best takeaway food service in the entire Southern Ocean.
All rights reserved. A weathered "jade berg" sails like an alien ship through the waters of Antarctica. Editor's note: This article has been updated to reflect the full name of poet Samuel Taylor Coleridge.
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Go Further. Animals Wild Cities This wild African cat has adapted to life in a big city. If the ice shelf remains intact, water could still potentially freeze to its underside because the huge, downward pressure of the shelf can alter the freezing temperature of water immediately under it. If that surface was later exposed to a warmer ocean as it rolled over so it could be seen, it might melt quickly. Ultimately, would colored icebergs disappear as the planet warms?
Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Slideshow 8 images. WHITE Most icebergs look white instead of the natural blue because dense snow is tightly packed on them.
Snowflakes reflect all wavelengths of light equally, creating the sparkling white color Lurens Pixabay. MB Photography Getty Images. JADE Colors other than blue and white can form when cold seawater freezes onto the underside of an ice shelf that extends from land over the ocean. Auscape Getty Images. Echo Images Alamy. Franz Lanting Getty Images. BLACK BERG Shiny black icebergs are large hunks of flawless frozen seawater; lack of internal cracks means the ice absorbs all wavelengths of light without scattering any back out.
Small ice cubes made in a freezer have no hue because they are just too small. In the Southern Hemisphere, almost all icebergs calve from the continent of Antarctica. Some icebergs are small. Bergy bit s are floating sea ice that stretch no more than 5 meters Growler s are even smaller. Icebergs can also be huge. Some icebergs near Antarctica can be as big as Sicily, the largest island in the Mediterranean Sea. As little as one-eighth of an iceberg is visible above the water.
Most of the mass of an iceberg lies below the surface of the water. This is where the phrase "tip of the iceberg" came from, meaning only part of an idea or problem is known.
There are many different kinds of icebergs. Brash ice , for instance, is a collection of floating ice and icebergs no more than 2 meters 6. A tabular berg is a flat-topped iceberg that usually forms as ice breaks directly off an ice sheet or ice shelf.
The ice below the water is dangerous to ships. The sharp, hidden ice can easily tear a hole in the bottom of a ship. A particularly treacherous part of the North Atlantic has come to be known as Iceberg Alley because of the high number of icebergs that find their way there.
Iceberg Alley is located miles east and southeast of Newfoundland, Canada. In , the Titanic , a large British ocean liner on its way to New York, struck an iceberg and sank in Iceberg Alley. More than 1, people drowned. Soon after the Titanic sank, an International Ice Patrol was established to track icebergs and warn ships. That patrol continues today. Iceberg patrols now use global positioning system GPS technology to help locate icebergs and prevent more tragedies like the Titanic.
It was found drifting toward the Drake Passage, an important shipping route south of Argentina. David Long of NASA's SeaWinds science team used satellite data to track the iceberg, the first time satellite technology was used for that purpose. Since that time, the SeaWinds team has used satellites to track the world's ice.
Icebergs that drift into warmer waters eventually melt. Scientists estimate the lifespan of an iceberg, from first snowfall on a glacier to final melting in the ocean, to be as long as 3, years. Photograph by Dennis Lowe , My Shot. Why So Blue?
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