According to a study published in the peer-reviewed Journal of Geophysical Research: Oceans, run by the American Geophysical Union, the icebergs may look green because of iron oxides in rock dust from mainland Antarctica.
Reports of green icebergs in the region date back to accounts from the early 1900s by explorers and sailors, say researchers.
The icebergs’ color was originally seen as an impurity, but researchers believe they have a greater role. If confirmed, the iron carried by these glaciers could help feed organisms in the ocean as they float outward, the study said.
“It’s like taking a package to the post office,” said Stephen Warren, a glaciologist at the University of Washington and lead author of the study, in a statement.
“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.”
Warren has been studying green icebergs since the 1980s. He analyzed samples from several green icebergs, including one from the Amery Ice Shelf in East Antarctica, and found they were made from marine ice, which is created when ocean water freezes underneath an ice shelf.
The study suggests iron oxides melded with marine ice through a “glacial flour,” a powder created when glaciers grind against bedrock. Researchers say if that flour is trapped under an ice shelf, it could mix with marine ice to create its green color.
Icebergs are usually blue in color, because the ice absorbs more red light than blue light, say researchers, who want to sample more green icebergs to study their iron content.