Arctic Ocean
At roughly 14,060,000 square kilometers, the Arctic Ocean is the smallest and shallowest of the world's five oceanic divisions, and it is also the coldest. Its average depth runs to only 1,038 meters. For most of the year, a skin of ice covers its surface, and in winter that ice covers it almost entirely.
The International Hydrographic Organization recognizes it as an ocean, yet not everyone agrees on what to call it. Some oceanographers prefer the Arctic Mediterranean Sea or the North Polar Sea. Others describe it as an estuary of the Atlantic Ocean, or simply the northernmost reach of one all-encompassing world ocean.
The ice is shrinking. The summer retreat has been quoted at 50 percent. In September 2012, the Arctic ice extent reached a new record minimum, diminished by 49 percent against the 1979 to 2000 average. What lies beneath that vanishing ice, who has lived along its shores, and why nations now circle its center are the questions that follow.
Human habitation in the North American polar region goes back at least 17,000 to 50,000 years, during the Wisconsin glaciation. Falling sea levels opened the Bering land bridge that joined Siberia to Alaska, and people crossed it in the settlement of the Americas.
The Pre-Dorset, dated to roughly 3200 to 850 BC, were among the early Paleo-Eskimo groups. Greenland held the Saqqaq culture from 2500 to 800 BC. Northeastern Canada and Greenland saw the Independence I and Independence II cultures, and Labrador and Nunavik held the Groswater. The Dorset culture then spread across Arctic North America between 500 BC and AD 1500.
The Dorset were the last major Paleo-Eskimo culture before the Thule people migrated east from present-day Alaska. The Thule Tradition lasted from about 200 BC to AD 1600, arising around the Bering Strait and eventually reaching almost the entire Arctic region of North America. They were ancestors of the modern Inuit, who now live in Alaska, the Northwest Territories, Nunavut, Nunavik, Labrador, and Greenland.
Pytheas of Massilia recorded a journey northward in 325 BC to a land he called Eschate Thule, where the Sun set for only three hours each day. There, he wrote, the water gave way to a congealed substance on which one can neither walk nor sail. He was likely describing loose sea ice, the growlers and bergy bits of today, and his Thule was probably Norway, though the Faroe Islands or Shetland have also been suggested.
Early cartographers could not agree on what filled the top of the map. Johannes Ruysch's map of 1507 and Gerardus Mercator's map of 1595 placed regions of land at the pole, while Martin Waldseemuller's world map of 1507 showed water. Expeditions added only small islands at first, such as Novaya Zemlya in the 11th century and Spitzbergen in 1596.
The myth of an Open Polar Sea proved stubborn. John Barrow, longtime Second Secretary of the British Admiralty, promoted exploration in search of it from 1818 to 1845. In the United States during the 1850s and 1860s, the explorers Elisha Kane and Isaac Israel Hayes both claimed to have glimpsed it.
Matthew Fontaine Maury still described the Open Polar Sea in his textbook The Physical Geography of the Sea in 1883. But every explorer who pushed nearer the pole reported a thick ice cap that persisted year-round, and the theory was widely considered disproven by the early 1900s. Fridtjof Nansen made the first nautical crossing of the Arctic Ocean during the Fram Expedition from 1893 to 1896.
Wally Herbert led the first surface crossing of the ocean in 1969, a dog sled expedition from Alaska to Svalbard, with air support. The first nautical transit of the North Pole came earlier, in 1958, by the submarine USS Nautilus. The first surface nautical transit followed in 1977, by the icebreaker NS Arktika.
Since 1937, Soviet and Russian manned drifting ice stations have monitored the ocean. Scientific settlements were built directly on the drift ice and carried thousands of kilometers by the floes. During World War II, the European region of the Arctic Ocean was heavily contested, as the Allied effort to resupply the Soviet Union through its northern ports met German naval and air forces.
In 1954, Scandinavian Airlines established the first commercial flights over the Arctic Ocean, between Los Angeles and Copenhagen. Decades later, the politics turned territorial. In August 2019, US President Donald Trump suggested buying Greenland, then raised the idea firmly in December 2024, calling ownership necessary for national security and economic interests, and saying the use of force was not ruled out.
In a the 10th of December 2024 social media post, Trump referred to the prime minister of Canada as the governor of a purported 51st state. He began a trade war on the 1st of February 2025. During a the 28th of March 2025 telephone call with Canadian Prime Minister Mark Carney, he again raised Canada becoming the 51st state, and he has expressed a desire to control the Canadian Internal Waters of the Arctic, commonly known as the Northwest Passage.
The Arctic Ocean fills a roughly circular basin almost the size of Antarctica, with a coastline 45,390 kilometers long. It is the only ocean smaller than Russia, whose land area is 17,098,246 square kilometers. Its largest marginal sea, the Barents Sea, spans about 1.4 million square kilometers, and the Bering Strait links it to the Pacific.
The Lomonosov Ridge runs underwater across the deep North Polar Basin, splitting it into two. The Eurasian Basin reaches 4,000 to 4,500 meters deep, and the Amerasian Basin, sometimes called the Hyperborean Basin, runs about 4,000 meters. Ridges subdivide these further into the Canada, Makarov, Amundsen, and Nansen Basins. The deepest point is Molloy Hole in the Fram Strait, at about 5,550 meters.
The crystalline basement rocks of the surrounding mountains formed during the Ellesmerian orogeny in the Paleozoic Era. Subsidence in the Jurassic and Triassic laid down sediments that became reservoirs for oil and gas. During the Cretaceous, the Canadian Basin opened, and tectonic activity tied to the assembly of Alaska pushed hydrocarbons toward what is now Prudhoe Bay.
The rifting apart of Pangea, beginning in the Triassic, opened the early Atlantic, then extended northward to open the Arctic Ocean. Because of sea ice and remoteness, the geology is still poorly explored. The Arctic Coring Expedition drilling suggested the Lomonosov Ridge is continental crust that may hold up to 10 billion barrels of oil.
In large parts of the ocean, the top layer of about 50 meters is colder and less salty than the water below, and stays stable because salinity governs density more than temperature does. Freshwater pours in from the great Siberian and Canadian rivers, the Ob, Yenisei, Lena, and Mackenzie, and quasi-floats on the denser, deeper water. This makes the Arctic Ocean's average salinity the lowest of the five major oceans.
The ocean holds a total volume of 18.07 million cubic kilometers, about 1.3 percent of the World Ocean. Inflow from the Pacific squeezes through the narrow Bering Strait at an average rate of 0.8 Sverdrups into the Chukchi Sea. Cold Alaskan winter winds freeze the surface there and push the new ice toward the Pacific, leaving dense, salty water that sinks and forms a halocline.
Atlantic Water enters through the Fram Strait in the depth range of 150 to 900 meters, the highest volumetric inflow to the ocean, about ten times the Pacific's. It is warmer than the surface water, up to 3 degrees Celsius, yet stays submerged because salinity makes it denser. Strong winds drive surface water into a circular current called the Beaufort Gyre, fed and freshened by the Canadian and Siberian rivers.
Arctic Bottom Water, beginning around 900 meters, is the densest in the World Ocean, and its outflow helps form Atlantic Deep Water that moderates global climate. Both Pacific and Atlantic waters exit through the Fram Strait, about 2,700 meters deep and 350 kilometers wide, where the Coriolis force concentrates outflow into the East Greenland Current. Over 2016 to 2018, oceanic heat flux to the surface overtook the atmospheric flux in the eastern Eurasian Basin.
Sea ice covers much of the surface and shifts with the seasons, with seasonal swings of about 7,000,000 square kilometers, a maximum in April and a minimum in September. Since 1980 the mean extent has fallen at a current rate of 12.85 percent per decade from a winter average of 15,600,000 square kilometers. Wind and currents drive the ice, piling it into pack ice where zones of compression arise.
Icebergs break away from northern Ellesmere Island and form from glaciers in western Greenland and extreme northeastern Canada. They are not sea ice but can become embedded in the pack, posing a hazard to ships, of which the Titanic is among the most famous. The ocean is virtually icelocked from October to June, yet the Baychimo once drifted through it untended for decades.
Polar night and midnight sun shape the biology, limiting the primary production of ice algae and phytoplankton to spring and summer, from March or April to September. Copepods such as Calanus finmarchicus, Calanus glacialis, and Calanus hyperboreus, along with euphausiids, link the producers to higher levels. In the Barents Sea, herring, young cod, and capelin feed, while polar cod hunts in the ice-covered central ocean.
The apex predators are marine mammals, seals, whales, and polar bears that prey on fish. Walruses and whales rank among the endangered species, and lion's mane jellyfish are abundant. The banded gunnel is the only species of gunnel that lives in the ocean.
The Arctic region is currently warming twice as fast as the rest of the planet, and the ice pack is thinning while a seasonal hole in the ozone layer frequently appears. Less sea ice lowers the planet's average albedo, which can drive global warming in a positive feedback loop. Research suggests the Arctic may become ice-free in summer for the first time in human history by 2040.
The Paleocene to Eocene Thermal Maximum 55 million years ago offers a warm precedent, when the region reached an average annual temperature of 10 to 20 degrees Celsius. Surface waters then warmed enough, seasonally at least, to support tropical lifeforms such as the dinoflagellates Apectodinium augustum, which require temperatures over 22 degrees Celsius. Estimates for the last ice-free Arctic range from 65 million years ago to as recently as 5,500 years ago.
Melting ice threatens to release methane from clathrate deposits near the shoreline, a powerful greenhouse gas that feeds further warming. Other concerns are radioactive, from Russian waste dump sites in the Kara Sea, Cold War test sites at Novaya Zemlya, Camp Century's contaminants in Greenland, and fallout from the Fukushima Daiichi disaster. Warming has also pushed polar bears toward people, and from December 2018 to February 2019 a mass invasion at Novaya Zemlya forced local authorities to declare a state of emergency.
The political dead zone near the center of the sea may hold 25 percent or more of the world's undiscovered oil and gas, drawing dispute among the United States, Russia, Canada, Norway, and Denmark. Yet on the 16th of July 2015 those same five nations signed a declaration to keep fishing vessels out of a 1.1 million square mile zone near the North Pole until better science and a regulatory system are in place.
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Common questions
How big is the Arctic Ocean and how does it rank among the world's oceans?
The Arctic Ocean spans approximately 14,060,000 square kilometers, making it the smallest and shallowest of the world's five oceanic divisions. It is also the coldest, with an average depth of 1,038 meters and a coastline 45,390 kilometers long.
Why does the Arctic Ocean have the lowest salinity of the major oceans?
The Arctic Ocean has the lowest average salinity of the five major oceans because of low evaporation, heavy freshwater inflow from rivers and streams, and limited connection and outflow to surrounding saltier waters. Great rivers including the Ob, Yenisei, Lena, and Mackenzie feed a low-salinity top layer that floats on denser deep water.
Who first crossed the Arctic Ocean by sea and by surface?
Fridtjof Nansen made the first nautical crossing of the Arctic Ocean during the Fram Expedition from 1893 to 1896. The first surface crossing was led by Wally Herbert in 1969 by dog sled from Alaska to Svalbard, and the submarine USS Nautilus made the first nautical transit of the North Pole in 1958.
How fast is Arctic sea ice declining?
Arctic sea ice mean extent has declined at a current rate of 12.85 percent per decade since 1980, from a winter average of 15,600,000 square kilometers. In September 2012 the ice extent reached a record minimum, diminished by 49 percent against the 1979 to 2000 average.
What oil and gas resources are in the Arctic Ocean?
The Arctic Ocean's political dead zone near its center may hold 25 percent or more of the world's undiscovered oil and gas resources. The Siberian Shelf is the largest continental shelf in the world and holds large oil and gas reserves, and the Lomonosov Ridge may contain up to 10 billion barrels of oil.
When could the Arctic Ocean become ice-free in summer?
Research suggests the Arctic may become ice-free in the summer for the first time in human history by 2040. The Arctic region is currently warming twice as fast as the rest of the planet, and reduced sea ice lowers the planet's average albedo in a positive feedback loop.
Which nations dispute control of the Arctic Ocean?
The United States, Russia, Canada, Norway, and Denmark are involved in a mounting dispute over the political dead zone near the center of the Arctic Ocean. On the 16th of July 2015 those same five nations signed a declaration to keep fishing vessels out of a 1.1 million square mile zone near the North Pole.