Oldest Arctic Sea Ice: A Shelter and Seed Bank For Algae

Large parts of the Arctic sea ice form during the winter and melt during the summer. Multi-year ice (MYI) is different: it survives the summer and can last for years. The oldest ice gathers in the north of Greenland and Canada in a region known as the Last Ice Area. This MYI is home to tiny algae that live in salty liquid channels and pockets within the ice. As this ice remains year-round, it can shelter the algae and act as a “seed bank”, preserving them until spring. When the ice begins to melt, the algae are released and can spread to younger ice, where they grow and provide food for Arctic animals. The ice can also carry the algae southwards as it drifts. However, much of the MYI has disappeared due to global climate change. As the old ice shrinks and is replaced by younger ice, the algae may lose both a stable home and a way to reach new areas, threatening the diversity of life in the Arctic sea ice.