# data[].attributes.attachment_link.readable_text
Credit:

Dr. Mike Goebel, NOAA NMFS SWFSC

Travel to the ends of the earth-literally-and discover the polar ocean basins. Both the Arctic Ocean and the Southern Ocean are defined by ice and dramatic shifts between endless day and endless night. The environments at the poles are some of the harshest on Earth-yet animals have found ways to survive there against the odds.

Although both are icy and frigid, the poles are actually more different than you might expect. In the northern polar region, the water and ice of the Arctic Ocean are surrounded by land. Depending on the season, much or all of the Arctic Ocean is covered by a layer of sea ice, ranging in thickness from a few inches to over six feet, which is always shifting as it floats on the ocean's surface. On the adjacent land, communities of native peoples have thrived for thousands of years by adapting to life along the edge of the ice.

Meanwhile, the southern polar region has the opposite geography, with the huge landmass of Antarctica surrounded by the turbulent Southern Ocean. All but one or two percent of Antarctic land is covered by glaciers, some of which are more than 15,000 feet (4,700 meters) thick. In the Antarctic, the only human residents are scientists and technicians at isolated research stations whose food must be shipped in by boat.

Arctic Ocean

The symbol of the Arctic is often the polar bear, the pole's cute yet fearsome top predator. These large marine mammals, who move easily between ice, water and land, are part of the diverse fauna of the Arctic Ocean.

What keeps this marine ecosystem going are organisms you can't see with the naked eye: microscopic phytoplankton and ice algae. Come March, the sun rises low in the Arctic horizon, and it won't set until six months later in September. During this bright period, Arctic algae and phytoplankton kick into overdrive, using photosynthesis to use the 24-hour sunlight to make food.

This explosion of life supports the entire food web for the whole year-from soft corals on the seafloor to the arctic foxes on the ice. The blooms of algae and phytoplankton feed zooplankton and larger predators, which are themselves in turn eaten, and so on up the food chain. When uneaten organisms die, they sink to the seafloor, feeding fish, seastars, soft corals, and other organisms in deeper water.

The sun-fed plankton are also important for the indigenous peoples of the Arctic who get food and clothing both from the sea (walrus, narwhals, beluga, other whales, polar bear, and fish) and the land (caribou, reindeer and musk-ox). Without phytoplankton and algae, the large marine animals would not have food to eat.

Southern Ocean

Credit:

© John Weller

Antarctica is the coldest, driest, and windiest of Earth's seven continents, and 98 percent of the continent is covered by ice with no tundra, trees or bushes. Even in the southern summer, the average temperature is -17.5°F (-27.5°C), although along the coast it is warmer.

Antarctica is isolated from the rest of the continents by the Circumpolar Current, which swirls clockwise around the landmass. This current pulls up cold, nutrient-rich waters from the deep sea to the surface, a process known as upwelling. The nutrients cultivate blooms of phytoplankton and ice-algae, which feed a super-abundant supply of Antarctic krill, small shrimp-like crustaceans. Large animals, like penguins, whales, and seals all feast on the krill.

Unlike the Arctic, there are no indigenous communities based in Antarctica. The people that live here are mostly scientists and technicians engaged in research.

Polar Ice

Many different types of ice can be found in the Arctic and Antarctic. Ice can be classified by age, whether it is made from fresh or salt water, or by its ever-changing forms. From giant glaciers to thin pack ice, each has distinctive characteristics, and those who have spent time in the Poles, from native people to sailors, have hundreds of names for the different kinds of ice.

Sea ice is by definition made from frozen seawater, which gives it different properties than ice made of freshwater. Its formation begins in very cold water surrounded by thicker sea ice or land with a slushy mix of water and ice crystals on the sea surface, called frazil ice. Then a film of ice forms, called grease ice, named for its close resemblance to the look of an oil slick on water. From this thin layer, the ice becomes thicker and stronger, forming pack ice. Pack ice is also referred to as drift ice because it is not attached to a shoreline and can be moved by the wind and ocean currents. The sea-ice closer to land and attached to the shoreline is called fast ice (short for fastened).

When salt water becomes ice, some of the salt is left behind in the water, making the water directly below sea ice saltier and denser than most seawater. This dense, salty water sinks and travels towards warmer tropical waters along the seafloor, forming part of the ocean's great circulating "conveyer belt". In 2011 a BBC crew filmed a never-before-seen phenomenon of the salt water sinking below newly formed ice and the water around it slowly freezing. This "brinicle," as it is called, eventually reaches the sea floor where it covers the animals living there (like sea stars and urchins) in a layer of deadly ice.

Sea ice forms during the winter, more than doubling the size of the Antarctic continent, and then melts in the spring and summer. In the Arctic, some of the sea ice stays throughout the year, called multi-year ice.

To study ice, sometimes you have to break it. The U.S. Coast Guard Cutter Healy is a ship with a primary mission to serve as a research platform in the Arctic. Even in the twenty-four-hour light of summer, the multi-year sea ice can be nearly 2 meters thick and the ship's job is to cut right through the ice, no matter its thickness. Scientists also use ice cores to gain insight into the Earth's ancient atmosphere. The ice has trapped bubbles, salts, and sediments that can help tell the story of how the climate has changed. This is especially important now that humans are emitting carbon dioxide at an unprecedented rate (see Threats to the Poles section).

Arctic Ocean

Imagine it being 40 degrees below zero (Fahrenheit and Celsius are equal at this temperature!) and not shivering. You could do that if you were a polar bear. Polar bears have two layers of fur, plus a layer of blubber to keep them warm in the coldest weather, and black skin to absorb the heat. They have hollow guard hairs that keep fur from matting when it gets wet. In fact, polar bears are more concerned about overheating than about getting cold. Because they are such strong swimmers, polar bears earned the species name of Ursus maritimus -bears of the sea. They can swim for miles and stay submerged for two minutes at a time.

A thick layer of blubber keeps walruses warm in the Arctic. Both male and female walruses have strong long tusks that they use to help pull themselves out of the water. They can also use their tusks to break through the ice to create breathing holes. Walruses forage on the seafloor, diving to depths up to 180 meters (590 feet) for clams, cockles, and mussels. They use highly sensitive whiskers on their snouts to locate food. Then they dig out their prey using the tough edges of their noses, similar to how pigs root around in dirt and grass.

Unicorns may be creatures of the imagination, but narwhals are the real deal. There are roughly 172,000 of them swimming in the Arctic today. A large portion of narwhals lives in Baffin Bay, which is the body of water between the northeastern coast of Canada and Greenland. Smaller populations live off the eastern coast of Greenland as well. In the winter narwhals live offshore among the ice floes, but in the summer, when the ice melts, they migrate towards the shore and congregate in summering grounds. They live and travel in pods that range in size from a few narwhals to several hundred individuals, but in the summertime, the congregations can be in the thousands. Females, young, and immature males live together and adult males live in their own pods.

A narwhal is a toothed whale and is closely related to dolphins, porpoises, and orcas. The famous tusk is actually a specialized tooth that protrudes out of the left lip, and in rare cases, a narwhal can have two. The longest tusks can reach over eight feet long (2.4 meters). While all males have a tusk, only 15 percent of females have a tusk, leading scientists to believe it has a role in sexual selection. Understanding the function of the tusk is an ongoing area of investigation.

Diving is one of the narwhal's special talents. They are some of the deepest diving whales with a record dive around 5,900 feet (1,800 meters)-over a mile deep! Traveling at such depths where there is intense pressure requires a few special adaptations, including a compressible rib cage and streamlined body. They are also excellent at conserving oxygen-their muscles are built to minimize oxygen use and simultaneously can carry large amounts of oxygen. During the deepest dives, a narwhal can shut off oxygen flow to unessential organs and instead divert it to where it is needed most.

Credit:

E. Siddon, UAF, Hidden Ocean 2005, NOAA.

Arctic Cod can live in water that is cooler than the freezing point of blood. Like the Antarctic ice fish, they have an antifreeze protein that keeps their blood flowing. Arctic Cod are critical players in the Arctic food web. They eat small crustaceans, such as amphipods and copepods. And in turn, Arctic Cod are food for seabirds and many marine mammals.

Southern Ocean

Weddell Seals live year round in the frigid waters of the Southern Ocean. They inhabit the "fast ice"-sea ice that is attached to the shore. These seals do not migrate and are commonly found within a few miles of their birthplace. When sleeping and resting, Weddell seals may remain in the same spot for hours, melting a hollow in the ice underneath them with their own body heat. Swimming under the ice they can dive as deep as 700 meters (2296 feet) and attack prey, such as small fish, from below. The fish above are backlit by the ice above and easily spotted in silhouette. Weddell seals are very vocal and have a large repertoire of sounds. Recent studies in the Ross Sea suggest the loud vocalizations may be used to stun prey.

Pole to Pole: Shared Species?

More than 11,000 kilometers (6835 miles) separate the Arctic from the Southern Ocean. So scientists thought only a few species would live in both places until researchers taking part in the Census of Marine Life found over 200 species that appeared to live in both polar seas, including cold-water worms, crustaceans, sea cucumbers and pteropod snails. But, further genetic testing proved that they were in fact, not the same species and that the miles between do make a difference. Some animals make fantastically long migrations, moving from the Arctic to the Antarctic and back again every year, living an endless polar summer.

Orcas, also known as killer whales, can be found in both the Arctic and the Southern Oceans. Orcas stay put in their distinctive ecosystems, and there are different characteristics of the groups (or pods) in various locations. All orcas are currently considered to be the same species, although there is some thought that they might be different species among the pods in Antarctica, or at least subspecies (pdf). They are the largest of the dolphins, and powerful predators. Orcas travel in pods of up to 40 related individuals. These pods act like wolf packs - working together to take down prey, including seals and larger whales. Orcas communicate through a wide range of sounds, and each pod has an audio signature that members can recognize from far away.

Credit:
R. Hopcroft, UAF, Hidden Ocean 2005 NOAA.

At both poles, tiny animals, called zooplankton, are near the base of the food chain. They eat the photosynthesizing phytoplankton and in turn are food for fish, seabirds and marine mammals. In the Southern Ocean, Antarctic krill swim in dense schools of 20,000 animals per cubic yard (540,000 cubic feet). In an amazing feat of synchronized swimming, they use a staggered formation so that no krill swims directly in another's wake. That way they avoid turbulence. In the Arctic Ocean, different species of copepods have different life cycles and eating patterns and they are important sources of food for larger organisms. Scientists are just beginning to understand who eats whom in the polar oceans.

Climate Change

Among the biggest threats to the poles is rapid climate change. Atmospheric carbon dioxide has been rising for more than a century, with large contributions from the fossil fuels used to power our homes, businesses, and cars. These increasing concentrations of greenhouse gases are trapping heat and taking a toll on the planet, especially at the poles where the largest increases in temperature will occur. Global temperatures have increased since the 1800s, and sea ice has been decreasing in extent and thickness.

While details concerning the extent of future impacts of climate change are the subject of debate, the Arctic is experiencing those changes today. It's warming at twice the rate of the rest of the planet. From 1979 to 2005, sea ice cover declined by about 20 percent. Scientists have discovered that the ratio of thick to thin sea ice is changing. In years past, thicker ice was about 40 percent of total ice cover. Now it's down to just 10 percent and the Arctic may have ice-free summers by the end of the 21st century. The amount of multi-year ice that remains from year to year has been declining since the 1980s due to warming temperatures, leaving mostly newer, thinner ice on the surface.

With these massive changes, the whole Arctic Ocean ecosystem will see impacts, from microscopic algae to massive polar bears to the people who call the Arctic home. Exactly how climate change will effect the Arctic is hard to predict. Polar bears, who rely on sea ice to reach seals for their winter meals, will have less time to reach their food source as the ice declines and breaks up earlier in the season. For people who live in the Arctic, weather and hunting grounds are becoming more unpredictable. Knowledge of the environment that has served generations is being defied by a changing climate. Many northern communities have also observed coastal erosion and watched the permafrost-ground that used to be frozen all year-melting and buckling under their homes and roads.

Overfishing

Arctic

One of the biggest differences between the poles has to do with people that reside there. Antarctica is a continent devoid of human settlement, except for the over 50 research stations built there by 27 different countries. But the Arctic region is home to more than 4 million people, many of which are indigenous people, native to the area. The indigenous people of the region encircling the North Pole are known by many names-Inuit, Eskimo, Kalaadit. Today their lands are part of four different nations-the United States, Canada, Denmark (Greenland) and Russia. For thousands of years, the people in the Arctic have adapted to living in an ice-bound environment. Key to survival is the skill with which they hunt arctic marine animals like seals and whales.

Antarctic

Polar Science at the Smithsonian

The Smithsonian's Arctic Studies Center, established in 1988, is the only U.S. government program with a special focus on northern cultural research and education. In keeping with this mandate, the Arctic Studies Center specifically studies northern peoples, exploring history, archaeology, social change and human lifestyles across the circumpolar world. The Smithsonian possesses one of the world's finest anthropological collections from arctic and sub-arctic regions. The Arctic Studies Center seeks to bring its researchers together with community scholars in the collaborative exploration of the cultural heritage represented in these impressive collections.

Arctic Ocean

The symbol of the Arctic is often the polar bear, the pole's cute yet fearsome top predator. These large marine mammals, who move easily between ice, water and land, are part of the diverse fauna of the Arctic Ocean.

What keeps this marine ecosystem going are organisms you can't see with the naked eye: microscopic phytoplankton and ice algae. Come March, the sun rises low in the Arctic horizon, and it won't set until six months later in September. During this bright period, Arctic algae and phytoplankton kick into overdrive, using photosynthesis to use the 24-hour sunlight to make food.

This explosion of life supports the entire food web for the whole year-from soft corals on the seafloor to the arctic foxes on the ice. The blooms of algae and phytoplankton feed zooplankton and larger predators, which are themselves in turn eaten, and so on up the food chain. When uneaten organisms die, they sink to the seafloor, feeding fish, seastars, soft corals, and other organisms in deeper water.

The sun-fed plankton are also important for the indigenous peoples of the Arctic who get food and clothing both from the sea (walrus, narwhals, beluga, other whales, polar bear, and fish) and the land (caribou, reindeer and musk-ox). Without phytoplankton and algae, the large marine animals would not have food to eat.

Southern Ocean

Credit:

© John Weller

Antarctica is the coldest, driest, and windiest of Earth's seven continents, and 98 percent of the continent is covered by ice with no tundra, trees or bushes. Even in the southern summer, the average temperature is -17.5°F (-27.5°C), although along the coast it is warmer.

Antarctica is isolated from the rest of the continents by the Circumpolar Current, which swirls clockwise around the landmass. This current pulls up cold, nutrient-rich waters from the deep sea to the surface, a process known as upwelling. The nutrients cultivate blooms of phytoplankton and ice-algae, which feed a super-abundant supply of Antarctic krill, small shrimp-like crustaceans. Large animals, like penguins, whales, and seals all feast on the krill.

Unlike the Arctic, there are no indigenous communities based in Antarctica. The people that live here are mostly scientists and technicians engaged in research.

Polar Ice

Many different types of ice can be found in the Arctic and Antarctic. Ice can be classified by age, whether it is made from fresh or salt water, or by its ever-changing forms. From giant glaciers to thin pack ice, each has distinctive characteristics, and those who have spent time in the Poles, from native people to sailors, have hundreds of names for the different kinds of ice.

Sea ice is by definition made from frozen seawater, which gives it different properties than ice made of freshwater. Its formation begins in very cold water surrounded by thicker sea ice or land with a slushy mix of water and ice crystals on the sea surface, called frazil ice. Then a film of ice forms, called grease ice, named for its close resemblance to the look of an oil slick on water. From this thin layer, the ice becomes thicker and stronger, forming pack ice. Pack ice is also referred to as drift ice because it is not attached to a shoreline and can be moved by the wind and ocean currents. The sea-ice closer to land and attached to the shoreline is called fast ice (short for fastened).

When salt water becomes ice, some of the salt is left behind in the water, making the water directly below sea ice saltier and denser than most seawater. This dense, salty water sinks and travels towards warmer tropical waters along the seafloor, forming part of the ocean's great circulating "conveyer belt". In 2011 a BBC crew filmed a never-before-seen phenomenon of the salt water sinking below newly formed ice and the water around it slowly freezing. This "brinicle," as it is called, eventually reaches the sea floor where it covers the animals living there (like sea stars and urchins) in a layer of deadly ice.

Sea ice forms during the winter, more than doubling the size of the Antarctic continent, and then melts in the spring and summer. In the Arctic, some of the sea ice stays throughout the year, called multi-year ice.

To study ice, sometimes you have to break it. The U.S. Coast Guard Cutter Healy is a ship with a primary mission to serve as a research platform in the Arctic. Even in the twenty-four-hour light of summer, the multi-year sea ice can be nearly 2 meters thick and the ship's job is to cut right through the ice, no matter its thickness. Scientists also use ice cores to gain insight into the Earth's ancient atmosphere. The ice has trapped bubbles, salts, and sediments that can help tell the story of how the climate has changed. This is especially important now that humans are emitting carbon dioxide at an unprecedented rate (see Threats to the Poles section).

Arctic Ocean

Imagine it being 40 degrees below zero (Fahrenheit and Celsius are equal at this temperature!) and not shivering. You could do that if you were a polar bear. Polar bears have two layers of fur, plus a layer of blubber to keep them warm in the coldest weather, and black skin to absorb the heat. They have hollow guard hairs that keep fur from matting when it gets wet. In fact, polar bears are more concerned about overheating than about getting cold. Because they are such strong swimmers, polar bears earned the species name of Ursus maritimus -bears of the sea. They can swim for miles and stay submerged for two minutes at a time.

A thick layer of blubber keeps walruses warm in the Arctic. Both male and female walruses have strong long tusks that they use to help pull themselves out of the water. They can also use their tusks to break through the ice to create breathing holes. Walruses forage on the seafloor, diving to depths up to 180 meters (590 feet) for clams, cockles, and mussels. They use highly sensitive whiskers on their snouts to locate food. Then they dig out their prey using the tough edges of their noses, similar to how pigs root around in dirt and grass.

Unicorns may be creatures of the imagination, but narwhals are the real deal. There are roughly 172,000 of them swimming in the Arctic today. A large portion of narwhals lives in Baffin Bay, which is the body of water between the northeastern coast of Canada and Greenland. Smaller populations live off the eastern coast of Greenland as well. In the winter narwhals live offshore among the ice floes, but in the summer, when the ice melts, they migrate towards the shore and congregate in summering grounds. They live and travel in pods that range in size from a few narwhals to several hundred individuals, but in the summertime, the congregations can be in the thousands. Females, young, and immature males live together and adult males live in their own pods.

A narwhal is a toothed whale and is closely related to dolphins, porpoises, and orcas. The famous tusk is actually a specialized tooth that protrudes out of the left lip, and in rare cases, a narwhal can have two. The longest tusks can reach over eight feet long (2.4 meters). While all males have a tusk, only 15 percent of females have a tusk, leading scientists to believe it has a role in sexual selection. Understanding the function of the tusk is an ongoing area of investigation.

Diving is one of the narwhal's special talents. They are some of the deepest diving whales with a record dive around 5,900 feet (1,800 meters)-over a mile deep! Traveling at such depths where there is intense pressure requires a few special adaptations, including a compressible rib cage and streamlined body. They are also excellent at conserving oxygen-their muscles are built to minimize oxygen use and simultaneously can carry large amounts of oxygen. During the deepest dives, a narwhal can shut off oxygen flow to unessential organs and instead divert it to where it is needed most.

Credit:

E. Siddon, UAF, Hidden Ocean 2005, NOAA.

Arctic Cod can live in water that is cooler than the freezing point of blood. Like the Antarctic ice fish, they have an antifreeze protein that keeps their blood flowing. Arctic Cod are critical players in the Arctic food web. They eat small crustaceans, such as amphipods and copepods. And in turn, Arctic Cod are food for seabirds and many marine mammals.

Southern Ocean

Weddell Seals live year round in the frigid waters of the Southern Ocean. They inhabit the "fast ice"-sea ice that is attached to the shore. These seals do not migrate and are commonly found within a few miles of their birthplace. When sleeping and resting, Weddell seals may remain in the same spot for hours, melting a hollow in the ice underneath them with their own body heat. Swimming under the ice they can dive as deep as 700 meters (2296 feet) and attack prey, such as small fish, from below. The fish above are backlit by the ice above and easily spotted in silhouette. Weddell seals are very vocal and have a large repertoire of sounds. Recent studies in the Ross Sea suggest the loud vocalizations may be used to stun prey.

Pole to Pole: Shared Species?

More than 11,000 kilometers (6835 miles) separate the Arctic from the Southern Ocean. So scientists thought only a few species would live in both places until researchers taking part in the Census of Marine Life found over 200 species that appeared to live in both polar seas, including cold-water worms, crustaceans, sea cucumbers and pteropod snails. But, further genetic testing proved that they were in fact, not the same species and that the miles between do make a difference. Some animals make fantastically long migrations, moving from the Arctic to the Antarctic and back again every year, living an endless polar summer.

Orcas, also known as killer whales, can be found in both the Arctic and the Southern Oceans. Orcas stay put in their distinctive ecosystems, and there are different characteristics of the groups (or pods) in various locations. All orcas are currently considered to be the same species, although there is some thought that they might be different species among the pods in Antarctica, or at least subspecies (pdf). They are the largest of the dolphins, and powerful predators. Orcas travel in pods of up to 40 related individuals. These pods act like wolf packs - working together to take down prey, including seals and larger whales. Orcas communicate through a wide range of sounds, and each pod has an audio signature that members can recognize from far away.

Credit:
R. Hopcroft, UAF, Hidden Ocean 2005 NOAA.

At both poles, tiny animals, called zooplankton, are near the base of the food chain. They eat the photosynthesizing phytoplankton and in turn are food for fish, seabirds and marine mammals. In the Southern Ocean, Antarctic krill swim in dense schools of 20,000 animals per cubic yard (540,000 cubic feet). In an amazing feat of synchronized swimming, they use a staggered formation so that no krill swims directly in another's wake. That way they avoid turbulence. In the Arctic Ocean, different species of copepods have different life cycles and eating patterns and they are important sources of food for larger organisms. Scientists are just beginning to understand who eats whom in the polar oceans.

Climate Change

Among the biggest threats to the poles is rapid climate change. Atmospheric carbon dioxide has been rising for more than a century, with large contributions from the fossil fuels used to power our homes, businesses, and cars. These increasing concentrations of greenhouse gases are trapping heat and taking a toll on the planet, especially at the poles where the largest increases in temperature will occur. Global temperatures have increased since the 1800s, and sea ice has been decreasing in extent and thickness.

While details concerning the extent of future impacts of climate change are the subject of debate, the Arctic is experiencing those changes today. It's warming at twice the rate of the rest of the planet. From 1979 to 2005, sea ice cover declined by about 20 percent. Scientists have discovered that the ratio of thick to thin sea ice is changing. In years past, thicker ice was about 40 percent of total ice cover. Now it's down to just 10 percent and the Arctic may have ice-free summers by the end of the 21st century. The amount of multi-year ice that remains from year to year has been declining since the 1980s due to warming temperatures, leaving mostly newer, thinner ice on the surface.

With these massive changes, the whole Arctic Ocean ecosystem will see impacts, from microscopic algae to massive polar bears to the people who call the Arctic home. Exactly how climate change will effect the Arctic is hard to predict. Polar bears, who rely on sea ice to reach seals for their winter meals, will have less time to reach their food source as the ice declines and breaks up earlier in the season. For people who live in the Arctic, weather and hunting grounds are becoming more unpredictable. Knowledge of the environment that has served generations is being defied by a changing climate. Many northern communities have also observed coastal erosion and watched the permafrost-ground that used to be frozen all year-melting and buckling under their homes and roads.

Overfishing

Arctic

One of the biggest differences between the poles has to do with people that reside there. Antarctica is a continent devoid of human settlement, except for the over 50 research stations built there by 27 different countries. But the Arctic region is home to more than 4 million people, many of which are indigenous people, native to the area. The indigenous people of the region encircling the North Pole are known by many names-Inuit, Eskimo, Kalaadit. Today their lands are part of four different nations-the United States, Canada, Denmark (Greenland) and Russia. For thousands of years, the people in the Arctic have adapted to living in an ice-bound environment. Key to survival is the skill with which they hunt arctic marine animals like seals and whales.

Antarctic

Polar Science at the Smithsonian

The Smithsonian's Arctic Studies Center, established in 1988, is the only U.S. government program with a special focus on northern cultural research and education. In keeping with this mandate, the Arctic Studies Center specifically studies northern peoples, exploring history, archaeology, social change and human lifestyles across the circumpolar world. The Smithsonian possesses one of the world's finest anthropological collections from arctic and sub-arctic regions. The Arctic Studies Center seeks to bring its researchers together with community scholars in the collaborative exploration of the cultural heritage represented in these impressive collections.

# data[].attributes.attachment_link.description
Travel to the ends of the earth-literally-and discover the polar ocean basins. Both the Arctic Ocean and the Southern Ocean are defined by ice and dramatic shifts between endless day and endless night. The environments at the poles are some of the harshest on Earth-yet animals have found ways to survive there against the odds.

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With its naturally extreme temperatures, the arctic truly is the last great escape for many wonderful species.

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The polar climate regions are characterized by a lack of warm summers but with varying winters. Every month a polar climate has an average temperature of less than 10 °C (50 °F). Regions with a polar climate cover more than 20% of the Earth's area. Most of these regions are far from the equator and near the poles, and in this case, winter days are extremely short and summer days are extremely long (could last for the entirety of each season or longer). A polar climate consists of cool summers and very cold winters, which results in treeless tundra, glaciers, or a permanent or semi-permanent layer of ice. It is identified with the letter E in the Köppen climate classification.

There are two types of polar climate: ET, or tundra climate; and EF, or ice cap climate. A tundra climate is characterized by having at least one month whose average temperature is above 0 °C (32 °F), while an ice cap climate has no months averaging above 0 °C (32 °F). In a tundra climate, even coniferous trees cannot grow, but other specialized plants can grow. In an ice cap climate, no plants can grow, and ice gradually accumulates until it flows or slides elsewhere. Many high altitude locations on Earth have a climate where no month has an average temperature of 10 °C (50 °F) or higher, but as this is due to elevation, this climate is referred to as Alpine climate. Alpine climate can mimic either tundra or ice cap climate.

On Earth, the only continent where the ice cap polar climate is predominant is Antarctica. All but a few isolated coastal areas on the island of Greenland also have the ice cap climate. Summits of many high mountains also have ice cap climate due to their high elevation. Coastal regions of Greenland that do not have permanent ice sheets have the less extreme tundra climates. The northernmost part of the Eurasian land mass, from the extreme northeastern coast of Scandinavia and eastwards to the Bering Strait, large areas of northern Siberia and northern Iceland have tundra climate as well. Large areas in northern Canada and northern Alaska have tundra climate, changing to ice cap climate in the most northern parts of Canada. Southernmost Argentina ( Tierra del Fuego where it abuts the Drake Passage) and such subantarctic islands such as the South Shetland Islands and the Falkland Islands have tundra climates of slight temperature range in which no month is as warm as 10 °C (50 °F). These subantarctic lowlands are found closer to the equator than the coastal tundras of the Arctic basin. Summits of many mountains of Earth also have polar climates, due to their higher elevations.

Some parts of the Arctic are covered by ice ( sea ice, glacial ice, or snow) year-round, especially at the most poleward parts; and nearly all parts of the Arctic experience long periods with some form of ice or snow on the surface. Average January temperatures range from about −40 to 0 °C (−40 to 32 °F), and winter temperatures can drop below −50 °C (−58 °F) over large parts of the Arctic. Average July temperatures range from about −10 to 10 °C (14 to 50 °F), with some land areas occasionally exceeding 30 °C (86 °F) in summer.

The Arctic consists of ocean that is almost surrounded by landmasses like Russia and Canada. As such, the climate of much of the Arctic is moderated by the ocean water, which can never have a temperature below −2 °C (28 °F). In winter, this relatively warm water, even though covered by the polar ice pack, keeps the North Pole from being the coldest place in the Northern Hemisphere, and it is also part of the reason that Antarctica is so much colder than the Arctic. In summer, the presence of the nearby water keeps coastal areas from warming as much as they might otherwise, just as it does in temperate regions with maritime climates.

Antarctica

The climate of Antarctica is the coldest on Earth. Antarctica has the lowest naturally occurring temperature ever recorded: −89.2 °C (−128.6 °F) at Vostok Station. It is also extremely dry (technically a desert, or so called polar desert), averaging 166 millimetres (6.5 in) of precipitation per year, as weather fronts rarely penetrate far into the continent.

Summits of most mountains also have polar climates, despite being in lower latitudes, due to their high elevations. All mountains of the Rocky Mountains, Alps, and the Caucasus have tundra climate. Some mountains of the Andes, the Saint Elias Mountains, and most mountains of the Himalayas, the Karakoram, the Hindu Kush Range, Pamir Mountains, the Tian Shan Mountains, and the Alaska Range, have ice cap climate. Only the summit of Mount Rainier has an ice cap climate in the Cascade Range.

There have been several attempts at quantifying what constitutes a polar climate.

Climatologist Wladimir Köppen demonstrated a relationship between the Arctic and Antarctic tree lines and the 10 °C (50 °F) summer isotherm; i.e., places where the average temperature in the warmest calendar month of the year is below the fixed threshold of 10 °C (50 °F) cannot support forests. See Köppen climate classification for more information.

Otto Nordenskjöld theorized that winter conditions also play a role: His formula is , where W is the average temperature in the warmest month and C the average of the coldest month, both in degrees Celsius. For example, if a particular location had an average temperature of −20 °C (−4 °F) in its coldest month, the warmest month would need to average 11 °C (52 °F) or higher for trees to be able to survive there as 9 − 0.1(−20) = 11. Nordenskiöld's line tends to run to the north of Köppen's near the west coasts of the Northern Hemisphere continents, south of it in the interior sections, and at about the same latitude along the east coasts of both Asia and North America. In the Southern Hemisphere, all of Tierra del Fuego lies outside the polar region in Nordenskiöld's system, but part of the island (including Ushuaia, Argentina) is reckoned as being within the Antarctic under Köppen's.

In 1947, Holdridge improved on these schemes, by defining biotemperature: the mean annual temperature, where all temperatures below 0 °C or 32 °F (and above 30 °C or 86 °F) are treated as 0 °C (because it makes no difference to plant life, being dormant). If the mean biotemperature is between 1.5 and 3 °C (34.7 and 37.4 °F), Holdridge quantifies the climate as subpolar (or alpine, if the low temperature is caused by elevation).

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The polar climate regions are characterized by a lack of warm summers but with varying winters. Every month a polar climate has an average temperature of less than 10 °C (50 °F). Regions with a polar climate cover more than 20% of the Earth's area.

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The cold polar climates can experience very low temperature indeed. This is because for half the year, the Sun does not rise above the horizon. A temperature of -88°C was once reported in Antarctica. Since the air in polar regions is so cold, it contains very little moisture.

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