Asked by: Robin Thomas, Newport Pagnell
Most icebergs have a bluish tinge because the ice absorbs longer wavelengths of visible light (reds) better than shorter ones (blues), reflecting more blue light back towards our eyes. However, some Antarctic icebergs are a striking emerald green, and have long puzzled scientists.
The latest theory is that these ‘jade bergs’ are caused by iron oxide minerals in the ocean. As glaciers move over the Antarctic mainland, they scrape its rocky surface, producing powdered rock rich in iron oxides that’s eventually carried into the sea. Scientists believe that pockets of the resulting iron-rich water then freeze onto the underside of icebergs, with the combination of orange-tinted iron oxide and blue ice producing a deep green hue.