Arctic Ocean

The Arctic Ocean which is located in the Northern Hemisphere and mostly in the Arctic north polar region, is the shallowest and smallest of the world’s five major oceanic divisions. The International Hydrographic Organization recognizes it as an ocean, although, some oceanographers consider it as 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 considered as the northernmost part of the all-encompassing World Ocean.

As it is almost totally surrounded by Eurasia and North America, the Arctic Ocean is partially covered by sea ice throughout the year, and almost completely during the winter. The temperature and salinity of the water vary seasonally as the ice cover melts and freezes; its salinity is the lowest on average of the five major oceans, because of low evaporation, heavy freshwater inflow from rivers and streams, and limited connected and outflow to surrounding oceanic waters with higher levels of salinity. The shrinking of the ice during the summer has been quoted at fifty percent. The US National Snow and Ice Data Center uses satellite data to produce a daily record of Arctic sea ice cover and the rate of the melting compared to an average period and specific past years.

The ocean occupies a roughly circular basin and covers an area of about 5,427,000 square miles, nearly the size of Russia. The coastline is 28,200 miles in length. It’s bordered by the land masses of North America, Greenland, Eurasia, and by several islands.

It’s normally considered to include Baffin Bay, Beaufort Sea, Barents Sea, East Siberian Sea, Greenland Sea, Chukchi Sea, Hudson Strait, Hudson Bay, Kara Sea, White Sea, Laptev Sea and other tributary bodies of water. It’s connected to the Pacific Ocean via the Bering Strait and to the Atlantic Ocean via the Greenland Sea and Labrador Sea.

Under the influence of the present ice age, the Arctic Ocean is controlled by a polar climate characterized by persistent cold and comparatively narrow annual temperature ranges. The winters are distinguished by continuous darkness referred to as polar night, cold and stable weather conditions, and clear skies; the summers are distinguished by continuous daylight referred to as midnight sun, damp and foggy weather, and weak cyclones with snow or rain.

The surface temperature of the Arctic Ocean is quite constant, almost the freezing point of seawater. Due to the Arctic Ocean consisting of saltwater, the temperature must reach -1.8 degrees Celsius before freezing actually happens. The sea water density, compared to fresh water, increases as it comes close to the freezing point and therefore tends to sink. It’s usually necessary that the upper 100-150 meters of ocean water cools to the freezing point to create sea ice. During the winter, the moderately warm ocean water wields a moderating influence, even when it is covered by ice. This is one of the reasons why the Arctic doesn’t experience extreme temperatures that are seen on the Antarctic continent.

There is some substantial seasonal variation in how much pack ice of the Arctic ice pack covers the Arctic Ocean. The majority of the Arctic ice pack is also covered in snow for about 10 months out of the year. The maximum snow cover is during April or March – about 7.9 to 20 inches over the frozen ocean.

The climate of the region has varied considerably in the past. As recently as 55 million years ago, in the Paleocene-Eocene Thermal Maximum, the region reached an average annual temperature of 50 to 68 degrees Fahrenheit. The waters of the surface of the northernmost Arctic Ocean warmed, at least seasonally, enough to hold up tropical life forms that require surface temperatures of over 72 degrees Fahrenheit.

Some endangered marine species residing in the Arctic Ocean include whales and walruses. The area has a delicate ecosystem which is slow to change and slow on recovery from damage or disruptions. Lion’s mane jellyfish are quite plentiful within the waters of the Arctic, and the banded gunnel is the only species of gunnel that resides in the ocean.

The ocean has comparatively little plant life except for phytoplankton. Phytoplankton are a vital part of the ocean and there are very large amounts of them in the Arctic, where they feed on nutrients from rivers and the currents of the Pacific and Atlantic oceans. During the summer, the sun is out during the day and the night, therefore making the phytoplankton able to photosynthesize for long periods of time and to reproduce rapidly. However, the reverse is true during the winter where they struggle to get enough light to stay alive.

Image Caption: Bathymetric map of the Arctic Ocean. Credit: Mikkalai/Wikipedia