“How can ice stay frozen over a period of multiple years?”
In most places in the world, ice will melt after the cold season is done. However, in arctic regions, the cold season is never completed. Instead, the ice will just stay together and become thick, hard-to-break Multiyear Ice. Multiyear ice’s tough properties makes it more difficult to break, meaning that arctic shipping can be very difficult. Multiyear ice also has different electromagnetic properties than sub-year ice, meaning that it can be detected by satellites and used as a proxy for global warming.