A polynya is an area of open water surrounded by sea ice. It is now used as geographical term for an area of unfrozen sea within the ice pack. It is a loanword from (polynya) , which refers to a natural ice hole, and was adopted in the 19th century by polar explorers to describe navigable portions of the sea. In past decades, for example, some polynyas, such as the Weddell Polynya, have lasted over multiple winters (1974–1976).