March 13, 2017
Antarctic ice turns green as St. Patrick’s Day approaches
NASA's Earth Observatory has released an intriguing image of green-tinged ice in Antartica's Granite Harbor, a cove near the Ross Sea.
The image prompted NASA to clarify that this was not a huge St. Patrick's Day stunt to dye the water green, but rather the result of phytoplankton being attached to the ice.
These microscopic marine plants, also called microalgae, grow in Antarctica in summer, which, of course, is coming to an end in the Southern Hemisphere. However, Earth Observatory points out, algae blooms can occur in the fall too.
This is the same time of year in the Antarctic that ice is forming, and algae appears to have been trapped inside that ice or attached to its surface.
Phytoplankton - important and mysterious
Marine glaciologist Jan Lieser of Australia's Antarctic Climate and Ecosystems Cooperative Research Center, who NASA quoted as saying phytoplankton was the cause of the green-tainted ice, was part of a team that observed a similar occurrence in 2012.
That year, a gigantic bloom that happened in late February and early March was measured to be 124 miles (200 kilometers) long and 62 miles (100 km) wide. Close inspection revealed that rather than floating freely, it was attached to ice.
NASA says that sea ice, winds, sunlight, nutrient availability and predators can all be factors in whether plankton grows in large enough quantities to color Antarctic ice, which at this time of year is slushy, and make it appear green even from space.
Scientists know that phytoplankton is important in the ecology of the Southern Ocean and is an important part for the food web, with zooplankton, fish, and other marine species depending on the food source. However, there are still several unknowns when it comes to phytoplankton.
Lieser asked: “Do these kinds of late-season ‘blooms’ provide the seeding conditions for the next spring’s bloom? If the algae get incorporated into the sea ice and remain more or less dormant during the winter, where do they end up after the winter?”
Another expedition will visit the area in April and perhaps provide some answers.
Image credit: NASA Earth Observatory