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. Even though the International Hydrographic Organization (IHO) recognizes it as an ocean, oceanographers may call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it as one of the seas of the Atlantic Ocean. Alternatively, the Arctic Ocean is 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, as well as limited outflow to surrounding waters with heavy freshwater inflow. The summer shrinking of the icepack has been quoted at 50%.