Scientists May Soon Solve Century-Old Mystery of Green Icebergs

  • Scientists May Soon Solve Century-Old Mystery of Green Icebergs

Scientists May Soon Solve Century-Old Mystery of Green Icebergs

The stunning sight of emerald green-colored icebergs in Antarctica has been documented for more than a century - in literature and beyond. These colors make sense for glaciers as ice absorbs more red light than blue.

"The marine‐ice part of such icebergs is clear, dark, and often green in color, because red or yellow particles from the seawater, in combination with the blue of ice, can shift the color to green", the researchers further explained.

A new study suggests that the iron oxide in rock dust from the mainland is responsible for the unusual color. They formulated the brand new principle after Australian researchers found massive quantities of iron in East Antarctica's Amery Ice Shelf. Iron is a key nutrient for the microscopic plants upon which many other organisms rely.

Professor Warren said: "It is like taking a package to the post office".

Warren, the study's lead author, is a glaciologist at the University of Washington who has been studying green icebergs since 1988. "We at all times thought inexperienced icebergs had been simply an unique curiosity, however now we predict they could really be essential".

For decades, scientists have argued about the cause behind the freakish phenomenon and debated why the green-hued ice chunks aren't the typical blue or white color.

Interestingly, the green ice he saw was a deep emerald hue much darker and clearer than that of normal icebergs- a signal to scientists that green ice might be different from regular iceberg ice.

Researchers on top of a large composite iceberg in October 1996.

"What is most fantastic is not their color but rather their clarity, because they have no bubbles", said Warren to IFLScience. These bubbles cause the photons to change direction repeatedly by refraction and re-emerge to the surface, causing the effect of a whiter ice. This glacier ice is formed of layers of snow that builds up over time and solidifies, meaning it has air pockets that reflect light.

Seawater freezes to the base of some ice shelves, forming marine ice, which incorporates organic and inorganic particles from the water.

The presence in the ice of iron oxides from the continental shelf can be the origin of this unique colour.

Their first thought was that dissolved organic carbon, microscopic particles of long-dead marine plants and animals, was getting trapped in the ice as the water froze to the underside of the ice shelf. But a sample of the ice proved their theory wrong: green and blue marine ice have similar amounts of organic material.

The problem nagged at Warren until a few years ago, when an oceanographer at the University of Tasmania tested an ice core from the Amery Ice Shelf for its iron content. The researchers found marine ice near the bottom of the core had almost 500 times more iron than the glacial ice above.

A partly capsized iceberg embedded in sea ice.

Ted Scambos, a senior research scientist at the National Snow and Ice Data Center who did not contribute to the research, told Mashable the explanation makes "perfect sense". The boundary between the glacier ice and marine ice (originally horizontal) is now tilted about 60 degrees.

Significant quantities of iron were discovered buried in the Antarctic ice and theorised iron-oxide, can alter its colour. But where was the iron coming from? When the rock dust got trapped under the ice shelf, it mixed with ocean water and became marine ice. He explained that the minerals might have come from Antarctica's mainland when glaciers that flow over bedrock turned rocks into a fine powder and unloaded them into the ocean.