Extra Info The many aspects of ice. A brief history of the polar regions. The fascination of the high latitudes The 21st century is the century of the polar regions. There are hardly any other natural landscapes that fascinate mankind as much as the distant land and marine regions of the Arctic and Antarctic. Most of the practically inaccessible ice and snow regions today are as yet unexplored. There are still no answers to many fundamental scientific questions such as: What exactly is hidden beneath the kilometre-thick ice sheets of Greenland and Antarctica?
How did the Arctic Ocean originate? Small changes in their complex structures can have far-reaching consequences. Between them they contain 99 per cent of the ice on the Earth. If they melt, global sea level will rise. Today, the impacts of global climate change are more clearly observed in the polar regions than anywhere else, and this is particularly true for the Arctic.
Since the middle of the 20th century it has been warming more than twice as fast as the rest of the Earth, and is thus seen as an early warning sign for climate change.
That was 16 per cent more than the previous summer. Both in the Arctic and the Antarctic, animals and plants have developed sophisticated survival strategies and impres- sive species diversity that people want to see for themselves. The number of tourists in the two polar regions is therefore increasing, just as economic interest in the exploitation of polar resources is growing. South of the 60th parallel, the Antarctic Treaty establishes strict limits for the major economic players.
In the Arctic, on the other hand, the five bordering states alone will determine what happens. The competition for raw materials and shipping routes there has already been underway for some time. This delineation was originally established based on the orientation of the sun. The Arctic Circle is thus defined as the latitude at which the sun does not set for exactly 24 hours during the summer solstice on 21 June each year. Thus, the position of the Antarctic Circle is defined by the latitude at which the sun remains below the horizon for 24 hours.
Due to branches of the warm Gulf Stream, the air temperature in this part of the Arctic does not fall much below freezing.
The many parallels observed between the Arctic and Antarctic realms should not obscure the fact that the two polar regions are fundamentally very different from each other. In the far south, Antarctica is a vast landmass — a remote continent with an area of This allows an active exchange of water masses among the Atlantic, Pacific and Indian Oceans, and large areas of it freeze over in the winter seasonal sea-ice cover.
This ocean not only separates Antarctica physically from the rest of the world, its clockwise-flowing water masses also insulate the continent climatically, which is one of the reasons why large parts of Antarctica are much colder than the Arctic. Furthermore, the Antarctic is considered to be the windiest and driest region on the Earth. The extreme climate here, along with its remoteness, is also the reason why very few animal and plant species have been able to establish themselves on the frozen continent.
People come only to visit for a short time. Apart from research stations, there are no permanent human settlements on the Antarctic continent today. The Arctic, by contrast, is diametrically different in several respects. Here, land masses surround an ocean that is centred on the pole. In contrast to the Southern Ocean, the Arctic Ocean has a permanent sea-ice cover whose area varies with the seasons.
It achieves its greatest extent at the end of winter and its smallest size at the end of summer, whereby scientists are observing a steady decrease in the extent of summer ice. Since the beginning of satellite measurements in , the surface area of summer ice has shrunk by around three million square kilometres.
This is an area about eight times the size of Germany. Because the continents of Europe, Asia and North America extend far into the Arctic region, the Arctic has been more successfully settled by plants, animals and people than the Antarctic.
Historical evidence suggests that the first aboriginal people were hunting in the coastal regions of the Arctic Ocean 45, years ago. Today more than four million people live within the Arctic polar region. Where does the Arctic begin, where the Antarctic? Seamen at that time used the constellations of the northern sky, primarily Ursa Major and Ursa Minor, to aid them with orientation during their voyages of discovery.
The two circles mark the geographic latitudes at which the sun does not set on the dates of the respective summer solstices. In the northern hemisphere the summer solstice usually falls on the 21st of June and in the southern hemisphere it is usually the 21st or 22nd of December. They are currently moving toward the geographic poles by around The Arctic Circle has never become established, however, as the definitive southern boundary of the Arctic region.
North of this imaginary line the long-term average temperature for the month of July lies below ten degrees Celsius. By this criterion the Arctic Ocean, Greenland, Svalbard, large parts of Iceland, and the northern coasts and islands of Russia, Canada and Alaska all belong to the Arctic realm. In Siberia and North America, on the other hand, cold Arctic air pushes the temperature boundary further to the south, so that regions such as the northeastern part of Labrador, the Hudson Bay, and a large portion of the Bering Sea are included as part of the Arctic 1.
On the Arctic Circle it does not set for 24 hours, and on the Antarctic Circle it does not rise for 24 hours. Another natural southern boundary sometimes used for the northern polar region is the Arctic tree line. As the name suggests, the present-day climate conditions north of this line are so harsh that trees are no longer able to survive. In North America, for example, this transition zone is a relatively narrow strip.
In northern Europe and Asia, however, it can be up to kilometres wide. In some areas, however, it can be located as much as kilometres to the south of the temperature boundary. According to this definition, western Alaska and the Aleutians would also belong to the Arctic, and the Arctic region would have a total area of around 20 million square kilometres.
A third natural boundary can be delineated based on ocean currents. According to this definition, the Arctic waters begin at the point where cold, relatively low-saline surface-water masses from the Arctic Ocean meet warmer more saline waters from the Atlantic or Pacific Ocean at the sea surface.
In the area of the Canadian Arctic Archipelago, the island group between North America and Greenland, this convergence zone extends to 63 degrees north latitude. As it continues eastward, it turns to the north between Baffin Island and Greenland. In the Fram Strait, the marine area between East Greenland and Svalbard, it is located as far as 80 degrees north, i. On the other side of the Arctic Ocean, in the Bering Sea, the definition of a convergence zone is somewhat more difficult, because here the water masses from the Pacific and Arctic Oceans mix extensively with each other instead of one flowing over the other.
On maps, therefore, this vague boundary line runs straight across the narrow Bering Strait. Besides these three boundaries to the Arctic, which are all characterized by natural features, other boundaries have been defined according to different delineating criteria. On the North American continent they draw the line at 60 degrees latitude. The most generous definition of the Arctic is found in the Arctic Human Development Report AHDR , where political and statistical aspects were considered in defining the area, which is why the boundary, especially in Siberia, extends further to the south than any other.
If, in special cases, other definitions of the Arctic region are necessary, this will be specifically pointed out. In the southern hemisphere, the definition of the boundary is not as difficult. The fact that the continent of Antarctica is essentially an island and the presence of distinctive ocean currents allow a relatively clear delineation of the boundary of the southern polar region.
This is the encircling oceanic zone where cold, northward-flowing surface water from the Antarctic meets warmer southward-flowing water masses from the north.
The cold, saline water sinks as a result of the density differences, and is diverted beneath the warmer water masses. The precise position of the convergence zone, however, varies somewhat depending on longitude, the weather and time of year, and can therefore shift regionally by as much as kilometres to the north or south.
This World Ocean Review will conform to the delineation of the Antarctic polar region established in by the Antarctic Treaty unless otherwise noted. Even though the North Pole does not belong to any continent, it is not considered to be a continent on its own. The North Pole is a magnetic region where the magnetic fields of the world meet. The actual magnetic pole is not constant. All the directions at the North Pole point towards the South Pole and all the longitude lines converge here.
The nearest inhabited region is Alert, Canada which is miles from the North Pole. North America is 3, miles to the south of the North Pole. North America is in the Northern Hemisphere and about 3, miles from the Equator.
Denmark itself is 2, Kaffeklubben Island is on the northern tip of Greenland. As their name implies, drifting stations move with the drifting ice pack in the Arctic Ocean. They usually last two or three years before before the warmer climate of the Greenland Sea breaks up the ice floe.
North Pole drifting stations are responsible for many discoveries about the ecosystem at the North Pole. In , for example, bathymetry studies revealed the massive Lomonosov Ridge. Drifting stations have recorded the development of cyclone s in the Arctic, as well Arctic shrinkage. Arctic shrinkage is climate change in the Arctic, including warming temperatures, the melting of the Greenland ice sheet resulting in more freshwater in the marine environment , and a loss of sea ice.
Ecosystems at the North Pole Polar bears, Arctic foxes, and other terrestrial animals rarely migrate to the North Pole. The drifting ice is an unpredictable habitat, and does not allow for regular migration route s or the establishment of dens in which to raise young.
Still, polar bears sometimes wander into the area in search of food. The undersea ecosystem of the North Pole is more varied than the ice above it. Shrimp, sea anemones, and tiny crustacean s inhabit in the area. A few ringed seals have been spotted. Ringed seals are common prey of the polar bears that wander into the region.
Larger marine mammal s, such as narwhal whales, are much more rare. Several species of fish live at the North Pole. Arctic cod are the most abundant. Arctic cod are small fish usually found near the seafloor, close to their food sources—tiny shrimp and crustaceans.
Birds are frequent visitors to the North Pole. The Arctic tern, which has the longest annual migration of any species on the planet, spends its spring and summer in the Arctic, though rarely as far north as the North Pole. It then flies 30, kilometers 18, miles south, to the Antarctic Circle. The Arctic tern makes an Arctic-Antarctic round-trip migration every year. Like the Arctic tern, all other birds spotted near the North Pole are migratory.
They include the small snow bunting and gull-like fulmars and kittiwakes. Exploration Major polar exploration began in the 19th century.
Norwegian explorer s Fridtjof Nansen and Hjalmar Johansen attempted a land-based expedition in A Swedish expedition led by Salomon August Andree tried to fly over the North Pole in a hydrogen balloon two years later. Cook was unable to provide any navigational records of his achievement, however, and rest of his team later reported that they did not quite reach the pole. The claim remains controversial.
Peary was supported and funded by the National Geographic Society , which verified his claim. It has been in dispute ever since. Although Peary's North Pole team included four other people, none of them were trained in navigation. They were therefore unable to verify Peary's claims, and one of them, Matthew Henson, reported a conflicting route from Peary. Peary himself never made his navigational records available for review. Skeptics have noted the remarkable speed with which the expedition traveled once Capt.
Bob Bartlett, the only other navigator, left the crew. Peary reported more than doubling the amount of territory covered daily as soon as Bartlett left the expedition.
Nonetheless, many explorers support Peary's claims. National Geographic conducted extensive studies of the photographs Peary took, and concluded they were taken within 8 kilometers 5 miles of the pole.
The photographs themselves have never been made public. Depth soundings taken by Peary and Henson also seem to support their claim to have reached the pole. Perhaps the most important support for Peary's claim came from British explorer Tom Avery's polar expedition of Avery mimic ked Peary's supposed route, using sled dog teams.
The expedition successfully reached the North Pole. The first verified expedition to the North Pole was conducted by Norwegian explorer Roald Amundsen in Amundsen did not use a ship or dogsleds—he flew over the pole on the airship Norge. The Norge , lifted by hydrogen and powered by a diesel engine, flew over the North Pole on its route from the Norwegian Arctic to the U. The first people verified to have set foot at the North Pole were a research group of geologist s and oceanographer s from the Soviet Union in The scientists were flown in and out of the pole over a three-day period.
Another U. The first verified expeditions to reach the North Pole by foot didn't happen until the late s. A team led by American explorer Ralph Plaisted used snowmobiles to reach the pole in A year later, an expedition led by British explorer Wally Herbert reached the pole on foot, with the aid of dog sleds and airlifted flown-in supplies.
In , 77 years after Robert Peary made his claim, a team led by National Geographic Explorer Emeritus Will Steger became the first verified expedition to reach the North Pole by dogsled without resupply. Shipping through the North Pole Today, large, powerful ships called icebreaker s are often used to navigate the ocean around the North Pole.
0コメント