Arctic Ocean

The Arctic Ocean is the smallest and shallowest of the world's five oceanic divisions. It covers about 14,060,000 km² and is the coldest ocean on Earth. Even though the International Hydrographic Organization calls it an ocean, some oceanographers refer to it as the Arctic Mediterranean Sea or North Polar Sea. It is sometimes described as an estuary of the Atlantic Ocean and is the northernmost part of the entire world ocean.

The Arctic Ocean surrounds the North Pole and reaches down to around 60°N. It is bordered by Eurasia and North America, with its edges defined by natural features like the Bering Strait on the Pacific side and the Greenland Scotland Ridge on the Atlantic side. Most of the time, it is covered by thick sea ice, especially in winter.

The Arctic Ocean's surface temperature and salinity change with the seasons as the ice cover melts and freezes. It has the lowest average salinity of all the major oceans because of low evaporation, lots of fresh water from rivers, and limited water exchange with saltier oceans. In recent years, the summer ice has been shrinking dramatically. According to the US National Snow and Ice Data Center, the amount of sea ice has been steadily decline in sea ice over time. In September 2012, the Arctic recorded its smallest ice extent ever, much smaller than the average from earlier decades.

History

Human habitation in the North American polar region goes back thousands of years, during a time when sea levels were lower. People crossed a land bridge connecting Siberia to North America, leading to the settlement of the Americas.

Early groups in the Arctic included the Pre-Dorset, Saqqaq culture, and Dorset culture. The Thule people, ancestors of the modern Inuit, later spread across the Arctic region of North America.

For much of European history, the Arctic remained largely unknown. Early explorers and mapmakers were unsure how to depict the regions around the North Pole. Over time, more expeditions explored the Arctic, gradually improving geographical knowledge.

In the 19th century, many believed in the existence of an Open Polar Sea. Explorers searched for this mythical body of water, but they found thick, year-round ice instead.

In the 20th century, important milestones included the first nautical crossing of the Arctic Ocean by Fridtjof Nansen and the first surface crossing by Wally Herbert. Submarines and icebreakers also made historic transits of the North Pole.

During World War II, the Arctic Ocean was a contested area, with Allied forces resupplying the Soviet Union through its northern ports. In 1954, Scandinavian Airlines began the first commercial flights over the Arctic Ocean.

Geography

The Arctic Ocean is the smallest and shallowest of the world's oceans. It covers an area of about 14,056,000 km² (5,427,000 sq mi), almost the size of Antarctica. It is the only ocean smaller than Russia.

The Arctic Ocean is surrounded by the land masses of Eurasia (Russia and Norway), North America (Canada and the U.S. state of Alaska), Greenland, and Iceland. It connects to the Pacific Ocean through the Bering Strait and to the Atlantic Ocean through the Greenland Sea and Labrador Sea. Some of the largest seas in the Arctic Ocean include the Barents Sea, Hudson Bay, and Greenland Sea.

Main article: Borders of the oceans § Arctic Ocean Main article: List of islands in the Arctic Ocean

Geology

The rocks around the Arctic Ocean were formed or changed long ago during a time called the Ellesmerian orogeny. Later, during the Jurassic and Triassic periods, lots of sediment settled, creating places where oil and gas can be found today. As continents moved, the Arctic Ocean opened up.

The Arctic Ocean formed when the supercontinent Pangea split apart. The seafloor spread from ridges like the Gakkel Ridge, moving the Lomonosov Ridge away from land. Because of ice and harsh conditions, scientists still don’t know everything about the Arctic Ocean’s geology. Some areas, like the Lomonosov Ridge, might hold a lot of oil.

Oceanography

The Arctic Ocean has a special way of moving water. Near the surface, there is a layer of colder, less salty water from big rivers like the Ob, Yenisei, Lena, and Mackenzie. This layer stays on top because it is lighter than the saltier water below. Between these layers is something called a halocline, where the water gets saltier and warmer as you go deeper.

The Arctic Ocean has a unique way of moving water, similar to the Mediterranean Sea. It has a total volume of about 18.07 × 10⁶ km³, which is just a small part of all the world's oceans. Water comes in from both the Pacific and Atlantic Oceans and forms three different kinds of water masses. The deepest water, called Arctic Bottom Water, starts around 900 meters deep and is very dense. It helps form water in the Atlantic and plays a big role in Earth's climate.

The Arctic Ocean is mostly covered by sea ice, which changes a lot during the year. The amount of ice has been getting smaller over the past few decades. This ice can move around a lot because of wind and ocean currents. Sometimes big chunks of ice, called icebergs, break off from islands and glaciers, and they can be dangerous for ships.

Climate

The Arctic Ocean has a polar climate, which means it is very cold most of the time. Winters are long and dark, with very cold temperatures. Summers are short and can have continuous daylight, also known as the midnight sun. During summer, temperatures can sometimes rise above freezing, and cyclones can bring rain or snow.

The surface water of the Arctic Ocean stays around −1.8 °C (28.8 °F), which is very close to the freezing point of seawater. This cold water is denser than warmer water, so it sinks and helps form sea ice. The amount of ice covering the Arctic Ocean changes with the seasons, and snow often covers the ice for about ten months of the year.

Currently, the Arctic is warming up faster than the rest of the world.

See also: Climate change in the Arctic

Biology

The Arctic Ocean has special plants and animals that can survive in its cold waters. During the spring and summer, tiny plants called phytoplankton and algae that live under the ice grow quickly. These plants are eaten by small animals like copepods and euphausiids, which are then eaten by bigger animals such as herring, polar cod, and even larger animals like seals, whales, and polar bears.

The Arctic Ocean is home to some endangered animals, like walruses and certain kinds of whales. This area is very sensitive to changes in temperature, warming up faster than other parts of the world. Some interesting sea creatures found here include the Lion's mane jellyfish and the banded gunnel, which is the only gunnel species that lives in this ocean.

Natural resources

See also: Natural resources of the Arctic, Territorial claims in the Arctic, and Marine mammal

The Arctic Ocean holds many valuable resources, including petroleum, natural gas, placer deposits, polymetallic nodules, sand, gravel, fish, seals, and whales. These resources are important for many countries around the world.

There is a special area in the middle of the Arctic Ocean where several countries, such as the United States, Russia, Canada, Norway, and Denmark, have disagreements over who owns the resources there. This area might contain a large amount of oil and gas, which could be very important for the world's energy needs.

Environmental concerns

Main articles: Climate change in the Arctic, Ozone depletion, and Pollution in the Arctic Ocean

The Arctic ice is thinning, and this reduction in sea ice can affect the Earth's climate. Scientists believe the Arctic might be ice-free in the summer by the year 2040 for the first time in human history. This change can impact ocean currents and weather patterns around the world.

Melting ice can also release methane, a powerful greenhouse gas, into the atmosphere, which can lead to more warming. There are also concerns about radioactive contamination from past activities, such as nuclear tests and waste disposal. In 2015, several countries agreed to protect a large area of the central Arctic Ocean from fishing until more is known about its marine life.