For well over a century, Antarctic explorers have been writing about stunningly beautiful green icebergs that they encountered in their travels. These formations, nicknamed “jade bergs”, are found nowhere else in the world. They are rare and overwhelmingly beautiful, but no one was sure how they came to be or why they retain their unique color. Until now.
New Theory May Explain Jade Icebergs
Stephen Warren, a glaciologist from the University of Washington, is captivated by the unusually colored icebergs and the mystery of how they were formed. He first encountered the ice during a 1988 Australian scientific expedition and has been working on understanding their origin ever since.
After more than 30 years of wrestling with the mystery, Warren published his theory in early 2019. He posturized that the icebergs are green because they are composed of marine ice, not standardly-found glacial ice, and have incorporated significantly higher levels of iron into their structure.
How Iron Entered The Iceberg
The first clues that Warren had about the connection between the icebergs and iron came from a study published by scientist Laura Herraiz-Borreguero of the University of Tasmania. She found that the Amery Ice Shelf core, an area of land that is near where the green icebergs are located, had as much as 500 times more iron than the glacial ice above it.
According to Warren, the movement of glaciers on the ice shelf grinds this iron into a powder. The finer, iron-rich grains enter water under the ice shelf near where marine ice is formed. Ultimately the material becomes incorporated into the iceberg.
Iceberg Coloring 101
Understanding the nature of color in any iceberg can help to explain exactly why jade bergs retain their special hue. Most icebergs, regardless of where they are found, are perceived by the human eye as being a quality of blue. This is because of the ice’s ability to absorb longer-length red light rays but reflect the shorter-length blue rays back to the viewer.
Iceberg hues range from near white to a darker turquoise. The older the ice is, the more it can absorb longer rays. That is because longer-term sustained pressure forces air bubbles, that can alter light ray absorption, out of an iceberg over time. Older ice has far fewer–if any — bubbles so it absorbs more red light rays and appears as a richer color blue.
Green Iceberg Coloring
With the rarer icebergs, experts have long commented on how few, if any, bubbles they observed in their structure. This clarity is one of the main contributors to the structure’s beauty. It was something that Stephen Warren noticed on his earliest expedition when he climbed on top of the iceberg to get a better look at it.
The lack of bubbles in the green ice contributes to their deeper, richer hue. However, the higher levels of iron also play a role in what observers see. The iron, which typically is seen in shades of reddish yellow combines with the blue coloring of the iceberg. Similarly to how yellow and blue paint make green paint, the color combinations of reflected light rays may be behind the icebergs’ appearance.
Benefit To The Marine Ecosystem
Warren believes that the iron-rich, green icebergs may play an important role in the polar marine ecosystem. They supply much-needed iron nutrients to the photo plankton and other base marine life that feed larger underwater species. These nutrients aren’t easily available oceanwide, but the ice can take them away from their source and redistribute them. In a statement accompanying his report, Stephen Warren compared this function to a postal delivery service, getting crucial items where they need to be.
While Warren remains excited by what he’s discovered, he realizes that more fieldwork needs to be completed to affirm his theory. He is continuing to conduct tests to ensure the theory holds. If it does, it can be considered an important improvement in the understanding of life in the most remote areas of the planet.