Why do some icebergs appear blue?

Icebergs appear blue primarily due to the unique way light interacts with their dense, crystalline structure. When light enters an iceberg, the ice absorbs longer wavelengths, such as red and yellow, while scattering and reflecting shorter blue wavelengths back to the observer.12

The intensity of this blue color is directly related to the presence of air bubbles within the ice. Typical icebergs or snow appear white because numerous air bubbles scatter all colors of light equally. In contrast, blue icebergs are composed of dense, glacial ice that has been subjected to high pressure, which squeezes out air bubbles. This lack of bubbles allows light to penetrate deeper into the ice before being reflected, making the blue hue more pronounced. While most icebergs are white or blue, some rare green icebergs exist in the Antarctic, which are believed to form when seawater rich in organic matter freezes onto the underside of ice shelves.13