The Arctic Ocean, located in the northern hemisphere and mostly in the Arctic north polar region, is the smallest of the world's five major oceanic divisions and the shallowest. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers may call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it as one of the mediterranean seas of the Atlantic Ocean . Alternatively, the Arctic Ocean can be seen as the northernmost lobe of the all-encompassing World Ocean.

Almost completely surrounded by Eurasia and North America, the Arctic Ocean is largely covered by sea ice throughout the year. The Arctic Ocean's temperature and salinity vary seasonally as the ice cover melts and freezes ; its salinity is the lowest on average of the five major seas, due to low evaporation, heavy freshwater inflow from rivers and streams, and limited connection and outflow to surrounding oceanic waters with higher salinities. The summer shrinking of the icepack has been quoted at 50%.