Mostly, icebergs are white or blue. However, occasionally, icebergs are identified that are green in appearance. Why is that so?
Over the years, the sighting of green icebergs occurred often enough that researchers started looking into the phenomena. Initially, they hypothesized that the green hue was caused by organic matter trapped inside the iceberg. The theory was that because dissolved carbon appears as a yellow shade, with it being shown through the blue of an iceberg, it would result in the green coloration.
However, according to a new study published in the Journal of Geophysical Research: Ocean, this is not the case.
After more than 30 years of research, Stephen Warren, a glaciologist at the University of Washington, and the study leader, has discovered that the greenish hue is likely caused by iron trapped within the icebergs.
Samples were taken from the Amery Ice Shelf of East Antarctica, according to Live Science. These samples were shown to have 500 times more iron than those icebergs that appeared blue in coloration.
It is believed that this iron comes from rocks underneath the Antarctic Ice Sheet. over time, these rocks are ground to a fine powder by the glaciers themselves. They then mix inside the icebergs and cause the discoloration. Over time, some of these green icebergs break away from the mainland and drift out on the ocean.
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Warren believes that these green icebergs also serve a purpose.
According to a statement issued by Warren, he believes that these green icebergs help to deliver iron to the ocean which, in turn, provides nutrients for sea life.
“It’s like taking a package to the post office. The iceberg can deliver this iron out into the ocean far away, and then melt and deliver it to the phytoplankton that can use it as a nutrient.”
In addition to discovering the iron content of green icebergs, Warren also noted the clarity.
Normally, icebergs have bubbles which can create a cloudy appearance. Blue icebergs usually contain many fewer bubbles than white ones. With the green icebergs, the bubble content was considered minimal.
“When we climbed up on that iceberg, the most amazing thing was actually not the color but rather the clarity. This ice had no bubbles. It was obvious that it was not ordinary glacier ice.”
Over time, the compression of icebergs pushes bubbles out of the ice which then creates the darker coloring seen in blue icebergs.
In order to prove their theory, research still needs to be done on the appearance of green icebergs in order to confirm the iron content levels in others.