The Arctic is the northernmost region of Earth. Most scientists define the Arctic as the area within the Arctic Circle, a line of latitude about 66.5° north of the Equator. Within this circle are the Arctic ocean basin and the northern parts of Scandinavia, Russia, Canada, Greenland, and the U.S. state of Alaska. The Arctic is almost entirely covered by water, much of it frozen. Some frozen features, such as glaciers and icebergs, are frozen freshwater. In fact, the glaciers and icebergs in the Arctic make up about 20% of Earth’s supply of freshwater. Most of the Arctic, however, is the liquid saltwater of the Arctic ocean basin. Some parts of the ocean’s surface remain frozen all or most of the year. This frozen seawater is called sea ice. Often, sea ice is covered with a thick blanket of snow. Sea ice helps determine Earth’s climate. Sea ice has a very bright surface, or albedo. This albedo means about 80% of sunlight that strikes sea ice is reflected back to space. The dark surface of the liquid ocean, however, absorbs about 90% of solar radiation. Due to thermohaline circulation, the Arctic’s thick, reflective sea ice moderates ocean temperatures around the world. The Arctic experiences the extremes of solar radiation. During the Northern Hemisphere’s winter months, the Arctic is one of the coldest and darkest places on Earth. Following sunset on the September equinox, the Earth’s tilted axis and its revolution around the sun reduce the light and heat reaching the Arctic until no sunlight penetrates the darkness at all. The sun rises again during the March equinox, and increases the light and heat reaching the Arctic. By the June solstice, the Arctic experiences 24-hour sunshine. Life in the Arctic Marine EcosystemThe Arctic ocean basin is the shallowest of the five ocean basins on Earth. It is also the least salty, due to low evaporation and huge influxes of freshwater from rivers and glaciers. River mouths, calving glaciers, and constantly moving ocean currents contribute to a vibrant marine ecosystem in the Arctic. The cold, circulating water is rich in nutrients, as well as the microscopic organisms (such as phytoplankton and algae) that need them to grow. Marine animals thrive in the Arctic. Primary consumers such as jellies and shrimp consume plankton, the basis of the Arctic marine food web. Secondary consumers include fish, seabirds (such as gulls and puffins), and a wide variety of baleen whales, including giant blue whales and bowhead whales. Tertiary consumers, animals that prey mostly on other carnivores, include toothed whales and dolphins (such as orcas and narwhals) and pinnipeds such as seals, sea lions, and walruses. Scavengers (including some sharks and crabs) and decomposers such as marine worms and algae break down dead and decaying materials. Organic nutrients are thus recycled into the marine ecosystem of the Arctic. Terrestrial EcosystemsThe varied landscapes of the Arctic provide for a variety of ecosystems. The Arctic includes the peaks of the Brooks mountain range in western North America, the enormous Greenland ice sheet, the isolated islands of the Svalbard archipelago, the fjords of northern Scandinavia, and the grassland plateaus and rich river valleys of northern Siberia. Although some forests lie near the Arctic Circle, plant life is mostly limited to grasses, sedges, and tundra vegetation such as mosses and lichens. These autotrophs have the ability to survive despite being covered in snow and ice for much of the year. Insects such as mosquitoes and moths are common, especially as icemelt creates ponds during spring and summer. Insects and insect larvae provide a crucial diet for birds, such as wrens and sandpipers, and freshwater fish. Primary consumers across the region range from tiny lemmings to enormous muskoxen. One of the most familiar Arctic herbivores is the caribou, often known as the reindeer in Europe and Asia. Secondary consumers include Arctic foxes, and raptors such as owls and eagles. The polar bear, the iconic apex predator of the Arctic, is equally able to hunt on land and around ice floes. Like the polar bear, many other animals of the Arctic are white: beluga whales, snowy owls, juvenile harp seals. This coloring helps camouflage them in heavy snow and ice. Many Arctic animals even change their coloration seasonally. Species of Arctic fox and Arctic hare, for example, are snowy white in winter but molt and grow a brownish or greyish fur coat during the summer months. Even fluffy white baby seals will ultimately grow up to a dark brown—better to blend in with the dark Arctic ocean waters instead of blinding white ice floes. People in the Arctic Indigenous CulturesPeople established communities and cultures in the Arctic thousands of years ago, and continue to thrive today. They have all developed smart, innovative ways to adapt to the unique challenges posed by the region’s severe climate. Housing or other shelter, for example, poses unusual challenges for Arctic peoples. Thick blankets of seasonal snow and lack of abundant trees for lumber historically limited the development of wood or stone structures common in subarctic climates. Inuit bands in Canada and Greenland, for example, engineered “snow houses”—more commonly known as igloos. Igloos were circular structures made of stacked ice (often sea ice), insulated with snow. The rectangular blocks were stacked in tight spiral pattern, giving the igloo a domed shape. Igloos could hold as few as two and as many as 20 people. Igloos were just one type of Inuit dwelling. Inuit communities also built tents with poles crafted from driftwood and whale bones or baleen. Animal hides covered these poles, and snow provided excellent insulation. The historically nomadic Sami (an indigenous people of Scandinavia and northwestern Russia) also built temporary tent-like structures, called lavvu. Instead of relying on driftwood, however, Sami communities had access to the rich taiga, or boreal forests, of the European subarctic. More permanent Sami structures included storehouses, where foods, textiles, and other valuables could be stored for later use or trade. These storehouses, which resemble log cabins, are notable for being elevated on stilts, centimeters or even meters from the ground. Elevation protected the valuables from excess rot due to snow or water seeping into the storehouse, as well as vermin such as mice or rats. Today, Arctic cultures such as the Inuit and Sami have access to high-quality building materials and sophisticated structural engineering plans. Still, buildings throughout the Arctic are reliant on efficient insulation and weatherization. (Weatherization is the process of protecting a dwelling from extreme temperature changes, precipitation, and wind.) Challenges of Indigenous CulturesRights to land and natural resources are an important part of contemporary culture and survival of indigenous peoples in the Arctic. Indigenous Arctic communities face tremendous challenges, often the result of colonization and exploitation of land and energy resources. For hundreds of years, for instance, European and Asian explorers interacted with Inuit communities in the Canadian Arctic, searching for the North Pole and the elusive “Northwest Passage.” (The Northwest Passage is a sea route connecting the North Pacific and North Atlantic ocean basins.) Increased contact with Europeans and European Americans often came with conflict. Inuit social structure, schools, and language were replaced with Western traditions. Starting in the late 20th century, regional, national, and international organizations increasingly recognized the political and cultural sovereignty of Arctic peoples. Rights to land and natural resources are an important part of this sovereignty. An agreement between the government of Canada and Inuit bands, for instance, ultimately resulted in the creation of the territory of Nunavut in 1999. Nunavut, Canada’s largest territory, stretches far into the central Canadian Arctic. More than half the population of Nunavut identifies as Inuit, and Inuktitut is the most-spoken language. ExplorationEuropean and Asian exploration of the Arctic began with Viking settlement of northern Scandinavia and Iceland in the 900s. Russian explorers navigated the “Northern Sea Route” of the Northeast Passage and the Siberian Arctic, eventually crossing the Bering Strait in the 1600s. The pursuit of the Northwest Passage, which would save untold time and money in trade between Europe and Asia, drove Arctic exploration during the Age of Discovery. Explorers such as John Cabot, Martin Frobisher, and Henry Hudson all failed to find an open-water route. The Northwest Passage was not completely navigated until 1906, when legendary Norwegian explorer Roald Amundsen and his crew made the voyage from Greenland to Alaska. Shifting sea ice made the trip hazardous; it took about three years, and required a relatively small ship (a converted fishing vessel). Resources in the Arctic The Arctic has enormous deposits of oil and natural gas. In Alaska, many oil companies work with indigenous groups known as “native corporations” to drill and export millions of barrels of oil every year. Alaska’s North Slope contains 6% of the largest oil fields in the United States and one of the 100 largest natural gas fields. Engineers and geographers estimate that oil and gas deposits in the Arctic make up 13% of the world’s undiscovered petroleum resources, and 30% of undiscovered natural gas resources. The Arctic is also rich in minerals, such as nickel and copper ore. Mineral resources also include gemstones and rare earth elements, which are used in batteries, magnets, and scanners. Some of these mineral deposits are underground, while others are buried beneath the Arctic Ocean. Mines and drilling operations are often dependent on the weather. In the winter, machinery can freeze, and the frozen ground becomes too hard to drill. In warmer weather, the Arctic permafrost can thaw and machinery can become unstable and damage the environment. Race for the ArcticAlmost all Arctic nations are scrambling to assert authority over the rich resources of the Arctic. This diplomatic conflict has been nicknamed the “New Cold War” or simply the “Race for the Arctic.” The exclusive economic zones of Russia, Norway, Denmark, Iceland, Greenland, Canada, and the United States extend to 200 nautical miles off their coasts. A country can explore and exploit all resources within its exclusive economic zone (EEZ). However, some Arctic nations are claiming territory on their continental shelves, not just their coastlines. Russia, Greenland, Denmark, and Canada, for instance, all claim the Lomonosov Ridge. The Lomonosov Ridge is an undersea mountain chain that stretches from the Canadian Arctic, through the North Pole, all the way to the waters off Siberia. Changing Climate in the Arctic Climate change is radically redefining the geography, biodiversity, and political units of the Arctic. The extent of sea ice in the Arctic is shrinking. The 21st century has marked record lows in both the winter maximum and summer minimum extent of sea ice. Most climatologists estimate that by the year 2100, most Arctic sea ice will melt every summer. The “twilight of the Arctic ice” would devastate many habitats. The plight of polar bears, for example, has become a symbol of global warming in the Arctic due to the cascading impacts of sea ice loss. Without sea ice, polar bears cannot catch enough seals to survive their annual winter fast. Polar bears that do survive are less likely to produce healthy offspring, reducing the population over generations. Scarcer food sources also drive polar bears into more contact with human populations, often relying on trash heaps for nutrition. This food sources impacts the health of polar bears and increases the incidents of conflict with human communities in the Arctic. The species range of the polar bear is also altered by climate change. Logic might indicate that polar bears would migrate further north as their traditional range heats up. Currents carry sea ice south, however, as it breaks up. Polar bears follow the sea ice habitat, and so their range has actually drifted south. This has brought polar bears into even closer contact with human populations, as well as prey species that have not adapted to the bears’ predatory behavior. The increasingly shrinking Arctic sea ice provides clear shipping routes for trade and travel. The Northwest Passage is still the most lucrative shipping lane in the Arctic. Experts estimate that shipping time may be cut by 40% if the Northwest and Northeast passages were ice-free all year. These deep-water shipping lanes also allow for larger, heavier ships than the Panama Canal, which would increase trade and profit even further. The tourism industry could also benefit from shrinking sea ice. In 2016, a luxury cruise ship traveled through the Northwest Passage for the first time. The ship, filled with more than 1,500 tourists, made the journey in three weeks.