The Arctic Ocean (also called Northern Icy Ocean or Northern Ocean), located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it a mediterranean sea or an estuary of the Atlantic Ocean. Alternatively, the Arctic Ocean can be seen as the northernmost part of the all-encompassing World Ocean.
Almost completely surrounded by Eurasia and North America, the Arctic Ocean is partly covered by sea ice throughout the year (and almost completely in winter). 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 oceans, 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 ice has been quoted at 50%. The US National Snow and Ice Data Center (NSIDC) uses satellite data to provide a daily record of Arctic sea ice cover and the rate of melting compared to an average period and specific past years.
Ice is water frozen into a solid state. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions. The addition of other materials such as soil may further alter its appearance.
Ice appears naturally in forms of snowflakes, hail, icicles, ice spikes and candles, glaciers, pack ice, frost, and polar ice caps. It is an important component of the global climate and plays an important role in the water cycle. Furthermore, ice has numerous cultural applications, from ice cooling of drinks to winter sports to the art of ice sculpting.
The molecules in solid ice may be arranged in numerous different ways, called phases, depending on the temperature and pressure. Typically, ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on Earth's surface The most common phase transition to ice Ih occurs when liquid water is cooled below 0°C (273.15K, 32°F) at standard atmospheric pressure. It can also deposit from vapour with no intervening liquid phase, such as in the formation of frost.