Changing Polar Geography
PHYSICAL GEOGRAPHY OF THE POLAR REGIONS
Landforms
The north polar seas have three types of sea ice.The fast ice grows outward from the shoreline and in the winter joins the pack ice, the drifting layer of ice that is constantly on the move. It tends to circle the North Pole, which occupies the central part of the Arctic Ocean, is stationary and about 10 feet thick, It does not freeze and deeper into the water, because its own thickness insulates the water from the cold air temperatures. However, rafting of broken pieces one upon another causes thick ice ridges that are common in both the pack ice and the polar ice and make travel over the surface very difficult.Along the margins of the Arctic Ocean, the landforms are extensions of the physiographic provinces farther south- the mountains of Alaska, the Canadian Shield, most of Greenland, the mountains of Scandinavia, and the mountains and plains of the Soviet Union. The Arctic portion of Alaska can be divided into two main regions: the North (or Arctic) Slope and the Brooks mountain range. The North Slope is a great syncline that slopes down northward from the Brooks Range to Point Barrow. The underlying rocks are 20,000 feet (6,096 m) thick and made up of sandstones, shales, coal, and oil shale. This is the region overlying the huge Alaskan oil reserves. About half the under the waters of the Arctic Ocean. structure is The North Slope is a barren tundra, with permanently frozen ground (permafrost) and patterned land from the work of solifluction. The Brooks Range is a rugged mountain region that rises up to heights of 9,000 feet (2,743 m). The mountains are jumbled masses of barren rock covered extensively by snow and glaciers. The Brooks Range drops abruptly to the north to a 2,500-feet-high (762 m) plateau that is about 80 miles (129 km) wide. The plateau is eroded into rolling foothills, which in turn drop to the North Slope.The Canadian Arctic is the largest bloc of territory belonging to one country located north of the tree line. It consists of two main areas: the mainland portion and the island portion. The surface configuration varies from low alluvial flats to rugged mountains 8,000 feet (2,438 m) high. Across the Canadian Arctic as a whole, however, the landscape is dominated by relatively flat ground covered with tundra vegetation. The mountains occur in the eastern part of the region, on Baffin and Ellesmere islands. Most of the region was heavily glaciated, to eskers and drumlins are common.Greenland is the world’s largest island and has some other unique features. Most of the island (85 percent) is covered with an immense ice sheet. The ice does not extend out onto the sea, coastal areas have bare rocks showing but the land is deeply dissected by long fjords. Greenland is somewhat saucer-shaped. The mass of ice fills a central depression that is surrounded by a coastal mountain fringe. Near the center of the island, the ice is about 10,000 feet (3,048 m) thick, but it decreases in thickness toward the coasts. The ice sheet holds a tremendous amount of water.Soviet Arctic territory is nearly as large as that of Canada. It consists of a tundra strip that extends along the entire northern coast and is crossed by many rivers flowing from south to north. A tip of the Ural Mountains extends into the Soviet Arctic, and the Putorana and Byrranga ranges interrupt the otherwise low-lying tundra. Soviet territory also consists of numerous islands located offshore to the north of the tundraNorway’s Arctic islands go by the general name of Svalbard, a medieval name dating back to the year 1194, when the islands were discovered. The islands consist of two separate groups with two main islands and numerous smaller islands. About half the area of Svalbard is ice-covered, and the islands are mountainous and have deeply indented coastlines caused by fjords. Svalbard has been important to Norway for its mineral industry, and especially coal. Coal seams several yards thick have been found, and mining has been carried on since 1904.The Antarctic continent has been isolated at the bottom of the earth for the last 25 million years. It covers about 10 percent of the world’s land surface, but the surface area changes with the seasonal expansion and retreat of the ice shelves. The continent once was adjacent to the landmasses of South America, Africa, and Australia, and exposed coal seams match those found on the other continents. The coal indicates that Antarctica once shared the warm and equable climates found on the other continents. Today, however, the coastal landscape is spiny and mountainous, with no coastal plains and steep ice-cliff shores. Most of the inland area is a vast white wasteland interrupted occasionally by mountain peaks.The land in the Antarctic is dominated by the huge ice sheet that covers about 98 percent of the continent. The ice sheet was formed from the compacted accumulation of about 100,000 years of snow. The average thickness of the ice is 5,250 feet (1,600 m), and it contains 70 percent of the world’s fresh-water reserves. The sheer weight of the ice has warped the continent downward so that much of the land of Antarctica lies below sea level. If the ice melted, the world’s oceans would rise by as much as 295 feet (90 m) and the water would inundate the homes of half the world’s people. With the removal of the weight of the ice, Antarctica would rise in a process called isostasy, so that much of the land would be above sea level again.The Antarctic ice sheet forms a high dome over the center of the continent that is 13,000 feet (3,962 m) in elevation. The top of the dome is called the pole of inaccessibility. The ice is constantly moving outward from the center of the dome, seeking lower levels toward the coastlines, and as it reaches the coasts it pushes right out into the open sea, still maintaining glacial form. The front face of the ice forms a barrier cliff 150 feet (46 m) high and goes down to 850 feet (259 m) below the surface of the water. In the Ross Sea region, the barrier extends for 500 miles (805 km) off the coast, and the front is 400 miles (644 km) wide. Eventually, parts of the ice break off becoming flat- topped icebergs. These huge chunks of ice float out into the oceans for many miles before finally melting. The largest iceberg ever recorded measured 208 miles (335 km) by 60 miles (97 km), but most are less than 25 miles (40 km) in diameter.Exposed rock of the Antarctic region is found mostly where mountain peaks jut up through the ice sheet. Many isolated peaks, called Nunataks, loom above the ice cover along western Antarctica, but some dry valleys are found in southern Victoria Land. They are called “dry” because they lack snow and ice. A region adjacent to the Ross Sea from Victoria Land to the Queen Maud Mountains contains the most mountain tops not covered by the ice sheet. Numerous peaks of this region exceed 10,000 feet (3,048 m) in elevation, and Mount Markham is the tallest at 14,272 feet (4,350 m). Other areas not covered by the ice sheet are parts of the Palmer Peninsula that point toward the Shetland Islands and the tip of South America. This peninsula is the only part of the Antarctic continent that extends north of the Antarctic continent that extends north of the Antarctic Circle. Other coastal mountains also lie exposed, but no rock landforms can be seen for hundreds of miles from the center of the pole of inaccessibility. The Antarctic’s tallest peak is Vinson Massif in the Ellsworth Mountains, located near the Ronne Ice Shelf. The top of the mountain is16,800 feet (5,121 m) above sea level. The 12,280-foot-high (3,743 m) Mount Erebus, in Victoria Land near McMurdo Sound, is the continent’s only live volcano.Climate
The polar air is not only dry, cold, and stable, it is also relatively free from impurities. No desert dust, forest-fire smoke, or industrial wastes pollute the air. Visibility extends for many miles, and it is difficult for people accustomed to the haze of temperate-latitude air to judge distances in the polar regions. Stable air means lack of turbidity that causes storms, not lack of wind. Surface winds, unrelated to storms, blow stronger in the polar region than anywhere else on earth. Gusts of more than 200 miles an hour are common. The stable air is sluggish, however, which means that air masses move much slower than the warmer air masses of the lower latitudes. The polar winds are deflected by the earth’s turning movement so that they blow from the east. They are called “polar easterlies.” They meet the prevailing westerly winds in the areas adjacent to the polar regions. The cold, polar air meets the warm, temperate air in frontal conditions that create storms. These storms usually stay within the zone of the prevailing westerly winds and greatly affect the weather of mid-latitude locations, but sometimes they sweep over the Polar Regions, causing blizzards. The generalized wind patterns for both Polar Regions, then, are:
1. calm air over the poles themselves,
2. constantly roaring surface winds outward from the calm centers, and
3. windy storms along the fringes of the polar regions.The temperature of the polar air is colder than those who have not experienced it can imagine. In such very cold conditions, steel shatters and oil turns to the consistency of rubber. The coldest temperature ever recorded on earth was at a Soviet weather station in the Antarctic. The temperature for August 24, 1960 was 126.9° F (-88.3° C). The Vostok station is 2,300 feet (901 m) higher than the South Pole, so it usually records lower temperatures. At The U.S. South Pole station, however, the temperature often drops to 100° F below zero (-55.6°C).The north polar region is much milder than the south polar region because the Arctic Ocean is a moderating influence on the temperature. Thus, the coldest place in the northern hemisphere is 1,500 miles (2,414 km) south of the North Pole, just north of the Arctic Circle, at the Siberian town of Verkhoyansk. Winter temperatures at Verkhoyansk have reached 90°F below zero, but the summer temperatures average above 60°F (15.5°C).The brief, warm summer seasons along the edges of the Arctic are never experienced in the Antarctic. Temperatures near the North Pole itself get down to 60° F below, but rarely colder. Summer temperatures at the pole are never above freezing.The annual average precipitation in the polar regions is less than 5 inches, which makes the polar regions as dry as the Sahara Desert. The great blizzards are mainly loose snow being blown by the polar winds from one place to another. The Antarctic coasts and the land fringes of the north polar region are much more humid than the poles themselves. Measurable amounts of rain are recorded during the summers, but only snow in the winters. The reason for the sparse precipitation is the inability of moisture-laden storms to penetrate the high-pressure domes that build up over the poles. Upper air descends over the poles and spreads outward as surface air movement. The descending air and cold temperatures create the high pressure. High pressure in any part of the world will create dry conditions, but such conditions are usually temporary. In the Polar Regions, however, the constant high pressure keeps the precipitation amounts low all year long.ICE SHEET
An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km2 (19,000 sq mi),thus also known as continental glacier. The only current ice sheets are in Antarctica and Greenland; during the last glacial period at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much of North America, the Weichsel an ice sheet covered northern Europe and the Patagonian Ice Sheet covered southern South America.Ice sheets are bigger than ice shelves or alpine glaciers. Masses of ice covering less than 50,000 km2 are termed an ice cap. An ice cap will typically feed a series of glaciers around its periphery.
Although the surface is cold, the base of an ice sheet is generally warmer due to geothermal heat. In places, melting occurs and the melt-water lubricates the ice sheet so that it flows more rapidly. This process produces fast-flowing channels in the ice sheet — these are ice streams.
The present-day polar ice sheets are relatively young in geological terms. The Antarctic Ice Sheet first formed as a small ice cap (maybe several) in the early Oligocene, but retreating and advancing many times until the Pliocene, when it came to occupy almost all of Antarctica. The Greenland ice sheet did not develop at all until the late Pliocene, but apparently developedvery rapidly with the first continental glaciation. This had the unusual effect of allowing fossils of plants that once grew on present-day Greenland to be much better preserved than with the slowly forming Antarctic ice sheet.
Antarctic ice sheet
The Antarctic ice sheet is the largest single mass of ice on Earth. It covers an area of almost 14 million km2 and contains 30 million km3 of ice. Around 90% of the fresh water on the Earth’s surface is held in the ice sheet, and, if melted, would cause sea levels to rise by 58 meter. The continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05°C/decade since 1957.
The Antarctic ice sheet is divided by the Trans Antarctic Mountains into two unequal sections called the East Antarctic ice sheet (EAIS) and the smaller West Antarctic Ice Sheet (WAIS). The EAIS rests on a major land mass but the bed of the WAIS is, in places, more than 2,500 meter below sea level. It would be seabed if the ice sheet were not there. The WAIS is classified as a marine-based ice sheet, meaning that its bed lies below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea.
Greenland ice sheet
The Greenland ice sheet occupies about 82% of the surface of Greenland, and if melted would cause sea levels to rise by 7.2 meters. Estimated changes in the mass of Greenland’s ice sheet suggest it is melting at a rate of about 239 cubic kilometers (57.3 cubic miles) per year. These measurements came from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite, launched in 2002, as reported by BBC News in August 2006.
Ice sheet dynamics
Ice movement is dominated by the motion of glaciers, whose activity is determined by a number of processes. Their motion is the result of cyclic surges interspersed with longer periods of inactivity, on both hourly and centennial time scales.
Predicted effects of global warming
The Greenland, and probably the Antarctic, ice sheets have been losing mass recently, because losses by melting and outlet glaciers exceed accumulation of snowfall. According to the Intergovernmental Panel on Climate Change (IPCC), loss of Antarctic and Greenland ice sheet mass contributed, respectively, about 0.21 ± 0.35 and 0.21 ± 0.07 mm/year to sea level rise between 1993 and 2003.
The IPCC projects that ice mass loss from melting of the Greenland ice sheet will continue to outpace accumulation of snowfall. Accumulation of snowfall on the Antarctic ice sheet is projected to outpace losses from melting. However, loss of mass on the Antarctic sheet may continue, if there is sufficient loss to outlet glaciers. In the words of the IPCC, “Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude. “More research work is, therefore, required in order to improve the reliability of predictions of ice-sheet response on global warming.
The effects on ice formations of an increasing in temperature will accelerate. When ice is melted away less light from the sun will be reflected back into space and more will be absorbed by the ocean water causing further rises in temperature. This positive ice-albedo feedback system will become independent of climate change past a certain point which will cause huge losses of ice to the icecaps.
An ice cap climate is a polar climate where the temperature never or almost never exceeds 0 °C (32 °F). The climate covers the areas around the poles, such as Antarctica and Greenland, as well as the highest mountain tops. Such areas are covered by a permanent layer of ice and have no vegetation, but they may have animal life, that usually feeds from the oceans. Due to their high latitudes, icecap climates experience 24 hours of sunlight in the summer and no sunshine in winter, the midnight sun and polar night.
Ice caps are defined as a climate with no months above 0 °C (32 °F).[2]. Such areas are found around the north and south pole, and on the top of the highest mountains. Since the temperature never exceeds the melting point of water, any snow or ice that accumulates remains there permanently, over time forming a large ice sheet.
The ice cap climate is distinct from the tundra climate. A tundra climate has a summer season with temperatures consistently above freezing for several months. This summer is enough to melt the winter ice cover, which prevents the formation of ice sheets. Because of this, tundra’s have vegetation, while ice caps do not.
Ice cap climate is the world’s coldest climate, and includes the coldest places on Earth. Vostok, Antarctica is the coldest place in the world, having recorded a temperature of −89.2 °C (−128.6 °F).
The constant freezing temperatures cause the formation of large ice sheets in ice cap climates. These ice sheets, however, are not static, but slowly move off the continents into the surrounding waters. New snow and ice accumulation then replaces the ice that is lost. Precipitation is nearly non-existent in ice cap climates. It is never warm enough for rain, and usually too cold to generate snow. However, wind can blow snow on to the ice sheets from nearby tundra.
The ice sheets are often miles thick. Much of the land located under the ice sheets is actually below sea level, and would be under the ocean if the ice is removed. However, it is the weight of the ice itself that forces this land below sea level. If the ice were removed, the land would rise back up in an effect called post-glacial rebound. This effect is creating new land in formerly ice cap areas such as Sweden.
The extreme pressure exerted by the ice allows for the formation of liquid water at low temperatures that would otherwise result in ice, while the ice sheet itself insulates liquid water from the cold above. The causes the formation of sub-glacial lakes, the largest being Lake Vostok in Antarctica.
Geologic history
Icecap climates have only existed in ice ages. There have been at least five such ice ages in the Earth’s past. Outside these ages, the Earth seems to have been ice-free even in high latitudes. By the geologic definition, Earth is currently in an ice age, in that the planet has permanent ice caps. Factors that cause ice ages include changes to the atmosphere, the arrangement of continents, the energy received from the sun, volcanos, and meteor impacts.
The current era is believed to be the only time in Earth’s history with ice caps at both poles. The Antarctic ice cap was formed after Antarctica split from South America, allowing the formation of the Antarctic Circumpolar Current. The Arctic ice cap was partially caused by the Azolla event, where a large number of ferns in the ocean died, sank, and never decayed, which trapped carbon dioxide beneath the ocean.
There is a hypothesis that around 650 million years ago, the entire planet was frozen, called Snowball Earth. Essentially the entire planet had an ice cap climate. However, this theory is disputed, and even proponents suggest there was an area of periodic melting near the equator.
Ice Cap Climate Locations
The two major areas with ice cap climates are Antarctica and Greenland. Some of the most northern extremes of Canada also have ice cap climates. In addition, a large portion of the Arctic Ocean near the North Pole remains frozen year round, effectively making it an icecap climate.
North Pole
The Arctic Ocean is located over the North Pole. As a result, the northern polar ice cap is the frozen ocean. The only large landmass to have an icecap climate is Greenland, but several smaller islands near the Arctic Ocean also have permanent ice caps.
Ice cap climates aren’t nearly as common on land at the North Pole as in Antarctica. This is because the Arctic Ocean moderates the temperatures of the surrounding land, making the extreme cold seen in Antarctica impossible. In fact, the coldest places in the northern hemisphere are in subarctic climates in Siberia, such as Verkhoyansk, which are much farther inland and lack the ocean’s moderating effect.
South Pole
The continent of Antarctica is centered around the South Pole. Antarctica is surrounded on all sides by the Southern Ocean. The Southern Ocean circles the entire planet at its latitude. As a result, high-speed winds circle around Antarctica, preventing warmer air from temperate zones from reaching the continent.
While Antarctica does have some small areas of Tundra on the northern fringes, the vast majority of the continent is extremely cold and permanently frozen. Because it is climactically isolated from the rest of the Earth, the continent has extreme cold not seen anywhere else, and weather systems rarely penetrate into the continent.
PHYSICAL GEOGRAPHY OF ANTARCTICA
Physical Features
The Antarctic also includes island territories within the Antarctic Convergence. The islands of the Antarctic region are: South Orkney Islands, South Shetland Islands, South Georgia, and the South Sandwich Islands, all claimed by the United Kingdom; Peter I Island and Bouvet Island, claimed by Norway; Heard and McDonald islands, claimed by Australia; and Scott Island and the Balleny Islands, claimed by New Zealand.
The Antarctic Ice Sheet dominates the region. It is the largest single piece of ice on Earth. This ice sheet even extends beyond the continent when snow and ice are at their most extreme.
The ice surface dramatically grows in size from about 3 million square kilometers (1.2 million square miles) at the end of summer to about 19 million square kilometers (7.3 million square miles) by winter. Ice sheet growth mainly occurs at the coastal ice shelves, primarily the Ross Ice Shelf and the Ronne Ice Shelf. Ice shelves are floating sheets of ice that are connected to the continent. Glacial ice moves from the continent’s interior to these lower-elevation ice shelves at rates of 10 to 1,000 meters (33-32,808 feet) per year.
Antarctica has a number of mountain summits, including the Trans-Antarctic Mountains, which divide the continent into eastern and western regions. A few of these summits reach altitudes of more than 4,500 meters (14,764 feet). The elevation of the Antarctic Ice Sheet itself is about 2,000 meters (6,562 feet) and reaches 4,000 meters (13,123 feet) above sea level near the center of the continent.
Without any ice, Antarctica would emerge as an archipelago of mountainous islands, known as Lesser Antarctica, and a single large landmass about the size of Australia, known as Greater Antarctica. These regions have different geologies.
Greater Antarctica, or East Antarctica, is composed of older, igneous and metamorphic rocks. Lesser Antarctica, or West Antarctica, is made up of younger, volcanic and sedimentary rock. Lesser Antarctica, in fact, is part of the “Ring of Fire,” a tectonically active area around the Pacific Ocean. Tectonic activity is the interaction of plates on Earth’s crust, often resulting in earthquakes and volcanoes. Mount Erebus, located on Antarctica’s Ross Island, is the southernmost active volcano on Earth.
The majority of the islands and archipelagos of Lesser Antarctica are volcanic and heavily glaciated. They are also home to a number of high mountains.
The oceans surrounding Antarctica provide an important physical component of the Antarctic region. The waters surrounding Antarctica are relatively deep, reaching 4,000 to 5,000 meters (13,123 to 16,404 feet) in depth.
Climate
Antarctica has an extremely cold, dry climate. Winter temperatures along Antarctica’s coast generally range from -10° Celsius to -30° Celsius (14° Fahrenheit to -22° Fahrenheit). During the summer, coastal areas hover around 0°C (32°F) but can reach temperatures as high as 9°C (48°F).
In the mountainous, interior regions, temperatures are much colder, dropping below -60°C (-76°F) in winter and – 20°C (-4°F) in summer. In 1983, Russia’s Vostok Research Station measured the coldest temperature ever recorded on Earth: -89.2°C (-128.6°F).
Precipitation in the Antarctic is hard to measure. It always falls as snow. Antarctica’s interior is believed to receive only 50 to 100 millimeters (2-4 inches) of water (in the form of snow) every year. The Antarctic deserts one of the driest deserts in the world.
The Antarctic region has an important role in global climate processes. It is an integral part of the Earth’s heat balance. The heat balance, also called the energy balance, is the relationship between the amount of solar heat absorbed by Earth’s atmosphere and the amount of heat reflected back into space. Antarctica has a larger role than most continents in maintaining Earth’s heat balance. Ice is more reflective than land or water surfaces. The massive Antarctic Ice Sheet reflects a large amount of solar radiation away from Earth’s surface. As global ice cover (ice sheets and glaciers) decreases, the reflectivity of Earth’s surface also decreases.
This allows more incoming solar radiation to be absorbed by the Earth’s surface, causing an unequal heat balance linked to global warming, the current period of climate change.
Interestingly, NASA scientists have found that climate change has actually caused more ice to form in some parts of Antarctica. They say this is happening because of new climate patterns caused by climate change. These patterns create a strong wind pattern called the “polar vortex.” Polar vortex winds lower temperatures in the Antarctic and have been building in strength in recent decades—as much as 15 percent since 1980. This effect is not seen throughout the Antarctic, however, and some parts are experiencing ice melt.
The waters surrounding Antarctica are a key part of the “ocean conveyor belt,” a global system in which water circulates around the globe based on density and on currents. The cold waters surrounding Antarctica, known as the Antarctic Bottom Water, are so dense that they push against the ocean floor. The Antarctic Bottom Water causes warmer waters to rise, or upwell.
Antarctic upwelling is so strong that it helps move water around the entire planet. This movement is aided by strong winds that circumnavigate Antarctica. Without the aid of the oceans around Antarctica, the Earth’s waters would not circulate in a balanced and efficient manner.
Flora and Fauna Lichens, mosses, and terrestrial algae are among the few species of vegetation that grow in Antarctica. More of this vegetation grows in the northern and coastal regions of Antarctica, while the interior has little if any vegetation.
The ocean, however, teems with fish and other marine life. In fact, the waters surrounding Antarctica are among the most diverse on the planet. Upwelling allows phytoplankton and algae to flourish. Thousands of species, such as krill, feed on the plankton. Fish and a large variety of marine mammals thrive in the cold Antarctic waters. Blue, fin, humpback, right, minke, sei, and sperm whales have healthy populations in Antarctica.
One of the apex, or top, predators in Antarctica is the leopard seal. The leopard seal is one of the most aggressive of all marine predators. This 3-meter (9-foot), 400-kilogram (882-pound) animal has unusually long, sharp teeth, which it uses to tear into prey such as penguins and fish.
The most familiar animal of Antarctica is probably the penguin. They have adapted to the cold, coastal waters. Their wings serve as flippers as they “fly” through the water in search of prey such as squid and fish. Their feathers retain a layer of air, helping them keep warm in the freezing water.
Contemporary Issues
The second half of the 20th century was a time of drastic change in the Antarctic. This change was initially fueled by the Cold War, a period of time defined by the division between the United States and the Soviet Union, and the threat of nuclear war.
The International Geophysical Year (IGY) of 1957-58 aimed to end Cold War divisions among the scientific community by promoting global scientific exchange. The IGY prompted an intense period of scientific research in the Antarctic. Many countries conducted their first Antarctic explorations and constructed the first research stations on Antarctica. More than 50 Antarctic stations were established for the IGY by just 12 countries: Argentina, Australia, Belgium, Chile, France, Japan, New Zealand, Norway, South Africa, the Soviet Union, the United Kingdom, and the United States.
In 1961, these countries signed the Antarctic Treaty, which established that: the region south of 60°S latitude remain politically neutral; no nation or group of people can claim any part of the Antarctic as territory; countries cannot use the region for military purposes or to dispose of radioactive waste; and research can only be done for peaceful purposes.
The Antarctic Treaty does support territorial claims made before 1961, by New Zealand, Australia, France, Norway, the United Kingdom, Chile, and Argentina. Under the treaty, the size of these claims cannot be changed and new claims cannot be made. Most importantly, the treaty establishes that any treaty-state has free access to the whole region.
As such, research stations supported by a variety of treaty-states have been constructed within each of these territorial claims. Today, 47 states have signed the Antarctic Treaty.
The Antarctic Treaty was an important geopolitical milestone because it was the first arms control agreement established during the Cold War. Along with the IGY, the Antarctic Treaty symbolized global understanding and exchange during a period of intense division and secrecy.
Many important documents have been added to the Antarctic Treaty. Collectively known as the Antarctic Treaty System, they cover such topics as pollution, conservation of animals and other marine life, and protection of natural resources.
The yearly Antarctic Treaty Consultative Meeting (ATCM) is a forum for the Antarctic Treaty System and its administration. Only 28 of the 47 treaty-states have decision-making powers during these meetings. These include the 12 original signatories of the Antarctic Treaty, along with 16 other countries that have conducted substantial and consistent scientific research there.
Future Issues
Two important and related issues that concern the Antarctic region are climate change and tourism. The ATCM continues to address both issues.
Antarctic tourism has grown substantially in the last decade, with roughly 40,000 visitors coming to the region in 2010. In 2009, the ATCM held meetings in New Zealand to discuss the impact of tourism on the Antarctic environment. Officials worked closely with the International Association of Antarctica Tour Operators (IAATO) to establish better practices that would reduce the carbon footprint and environmental impact of tour ships. These include regulations and restrictions on numbers of people ashore; planned activities; wildlife watching; pre- and post- visit activity reporting; passenger, crew, and staff briefings; and emergency medical-evacuation plans. The ACTM and IAATO hope more sustainable tourism will reduce the environmental impacts of the sensitive Antarctic ecosystem. Tourism is one facet of the ACTM’s climate change outline, discussed during meetings in Norway in 2010. Climate change disproportionately affects the Antarctic region, as evidenced by reductions in the size of the Antarctic Ice Sheet and the warming waters off the coast. The ACTM recommended that treaty-states develop energy-efficient practices that reduce the carbon footprint of activities in Antarctica and cut fossil fuel use from research stations, vessels, ground transportation, and aircraft.
The Antarctic has become a symbol of climate change. Scientists and policymakers are focusing on changes in this environmentally sensitive region to push for its protection and the sustainable use of its scientific resources.
ARCTIC GEOGRAPHY
The Arctic is a single, highly integrated system comprised of a deep, ice covered, and nearly isolated ocean surrounded by the land masses of Eurasia and North America, except for breaches at the Bering Strait and in the North Atlantic. It encompasses a range of land- and seascapes, from mountains and glaciers to flat plains, from coastal shallows to deep ocean basins, from polar deserts to sodden wetlands, from large rivers to isolated ponds. They, and the life they support, are all shaped to some degree by cold and by the processes of freezing and thawing. Sea ice, permafrost, glaciers, ice sheets, and river and lake ice are all characteristic parts of the Arctic’s physical geography.
The Arctic Ocean covers about 14 million square kilometers. Continental shelves around the deep central basin occupy slightly more than half of the ocean’s area – a significantly larger proportion than in any other ocean. The landforms surrounding the Arctic Ocean are of three major types:
1. rugged uplands, many of which were overrun by continental ice sheets that left scoured rock surfaces and spectacular fjords;
2. flat-bedded plains and plateaus, largely covered by deep glacial, alluvial, and marine deposits; and
3. folded mountains, ranging from the high peaks of the Canadian Rockies to the older, rounded slopes of the Ural Mountains. The climate of the Arctic, rather than its geological history, is the principal factor that gives the arctic terrain its distinctive nature.
Climate
The Arctic encompasses extreme climatic differences, which vary greatly by location and season. Mean annual surface temperatures range from 4 ºC at Reykjavik, Iceland (64º N) and 0 ºC at Murmansk, Russia (69º N) through -12.2 ºC at Point Barrow, Alaska (71.3º N), -16.2 ºC at Resolute, Canada (74.7º N), -18 ºC over the central Arctic Ocean, to -28.1 ºC at the crest of the Greenland Ice Sheet (about 71º N and over 3000 m elevation). Parts of the Arctic are comparable in precipitation to arid regions elsewhere, with average annual precipitation of 100 mm or less. The North Atlantic area, by contrast, has much greater average precipitation than elsewhere in the Arctic.
Arctic weather and climate can vary greatly from year to year and place to place. Some of these differences are due to the poleward intrusion of warm ocean currents such as the Gulf Stream and the southward extension of cold air masses. “Arctic” temperature conditions can occur at relatively low latitudes (52º N in eastern Canada), whereas forestry and agriculture can be practiced well north of the Arctic Circle at 69º N in Fennoscandia. Cyclic patterns also shape climate patterns, such as the North Atlantic Oscillation, which strongly influences winter weather patterns across a vast region from Greenland to Central Asia, and the Pacific Decadal Oscillation, which has a similar influence in the North Pacific and Bering Sea. Both may be related to the Arctic Oscillation.
Ecosystems and ecology
Although the Arctic is considered a single system, it is often convenient to identify specific ecosystems within that system. Such classifications are not meant to imply clear separations between these ecosystems. In fact, the transition zones between terrestrial, freshwater, and marine areas are often dynamic, sensitive, and biologically productive. Nonetheless, much scientific research, and indeed subsequent chapters in this assessment, uses these three basic categories.
Terrestrial ecosystems
Species diversity appears to be low in the Arctic, and on land decreases markedly from the boreal forests to the polar deserts of the extreme north. Only about 3% (5,900 species) of the world’s plant species occur in the Arctic north of the tree line. However, primitive plant species of mosses and lichens are relatively abundant. Arctic plant diversity appears to be sensitive to climate. The temperature gradient that has such a strong influence on species diversity occurs over much shorter distances in the Arctic than in other biomes. North of the tree line in Siberia, for example, mean July temperature decreases from 12 to 2 ºC over 900 km. In the boreal zone, a similar change in temperature occurs over 2000 km. From the southern boreal zone to the equator, the entire change is less than 10 ºC.
The diversity of arctic animals north of the treeline (about 6000 species) is similar to that of plants. As with plants, the arctic fauna account for about 3% of the global total, and evolutionarily primitive species are better represented than advanced species. In general, the decline in animal species with increasing latitude is more pronounced than that of plants. An important consequence of this is an increase in dominance. “Super-dominant” species, such as lemmings, occupy a wide range of habitats and generally have large effects on ecosystem processes.
Many of the adaptations of arctic species to their current environments limit their responses to climate warming and other environmental changes. Many adaptations have evolved to cope with the harsh climate, and these make arctic species more susceptible to biological invasions at their southern ranges while species at their northern range limit are particularly sensitive to warming. During environmental changes in the past, arctic species have changed their distributions rather than evolving significantly. In the future, changes in the conditions in arctic ecosystems may affect the release of greenhouse gases to the atmosphere, providing a possibly significant feedback to climate warming although both the direction and magnitude of the feedback are currently very uncertain. Furthermore, vegetation type profoundly influences the water and energy exchange of arctic ecosystems, and so future changes in vegetation driven by climate change could profoundly alter regional climates.
Arctic Freshwater ecosystems
Arctic freshwater ecosystems are extremely numerous, occupying a substantial area of the arctic landmass. Even in areas of the Arctic that have low precipitation, freshwater ecosystems are common and the term “polar deserts” refers more to the impoverishment of vegetation cover than to a lack of groundwater. Arctic freshwater ecosystems include three main types: flowing water (rivers and streams), permanent standing water (lakes and ponds), and wetlands such as peatlands and bogs. All provide a multitude of goods and services to humans and the biota that use them.
Flowing water systems range from the large, north-flowing rivers that connect the interiors of continents with the Arctic Ocean, through steep mountain rivers, to slow-flowing tundra streams that may contain water during spring snow melt. The large rivers transport heat, water, nutrients, contaminants, sediment, and biota into the Arctic and together have a major effect on regional environments. The larger rivers flow throughout the year, but small rivers and streams freeze in winter. The biota of flowing waters is extremely variable: rivers fed mainly by glaciers are particularly low in nutrients and have low productivity. Spring-fed streams can provide stable, year-round habitats with a greater diversity of primary producers and insects.
Permanent standing waters vary from very large water bodies to small and shallow tundra ponds that freeze to the bottom in winter. By the time the ice melts in summer, the incoming solar radiation is already past its peak, so that the warming of lakes is limited. Primary production, by algae and aquatic mosses, decreases from the subarctic to the high Arctic. Zooplankton species are limited or even absent in arctic lakes because of low temperatures and low nutrient availability. Species abundance and diversity increase with the trophic status of the lake. Fish species are generally not diverse, ranging from 3 to 20 species, although species such as Arctic char (Salvelinusalpinus) and salmon (Salmosalar) are an important resource.
Wetlands are among the most abundant and productive aquatic ecosystems in the Arctic. They are ubiquitous and characteristic features throughout the Arctic and almost all are created by the retention of water above the permafrost. They are more extensive in the southern Arctic than the high Arctic, but overall, cover vast areas – up to
3.5 million km2 or 11% of the land surface. Several types of wetlands are found in the Arctic, with specific characteristics related to productivity and climate. Bogs, for example, are nutrient poor and have low productivity but high carbon storage, whereas fens are nutrient rich and have high productivity. Arctic wetlands have greater biological diversity than other arctic freshwater ecosystems, primarily in the form of mosses and sedges. Together with lakes and ponds, arctic wetlands are summer home to hundreds of millions of migratory birds. Arctic freshwater ecosystems are particularly sensitive to climate change because the very nature of their habitats results from interactions between temperature, precipitation, and permafrost. Also, species limited by temperature and nutrient availability are likely to respond to temperature changes and effects of UV radiation on dead organic material in the water column.
Arctic Marine ecosystems
Approximately two-thirds of the Arctic as defined by the ACIA comprises ocean, including the Arctic Ocean and its shelf seas plus the Nordic, Labrador, and Bering Seas. These areas are important components of the global climate system, primarily because of their contributions to deep water formation that influences global ocean circulation. Arctic marine ecosystems are unique in having a very high proportion of shallow water and coastal shelves. In common with terrestrial and freshwater ecosystems in the Arctic, they experience strong seasonality in sunlight and low temperatures. They are also influenced by freshwaters delivered mainly by the large rivers of the Arctic. Ice cover is a particularly important physical characteristic, affecting heat exchange between water and atmosphere, light penetration to organisms in the water below, and providing a biological habitat above (for example, for seals and polar bears (Ursusmaritimus)), within, and beneath the ice. The marginal ice zone, at the edge of the pack ice, is particularly important for plankton production and plankton-feeding fish.
Some of these factors are highly variable from year to year and, together with the relatively young age of arctic marine ecosystems, have imposed constraints on the development of ecosystems that parallel those of arctic lands and freshwaters. Thus, in general, arctic marine ecosystems are relatively simple, productivity and biodiversity are low, and species are long-lived and slow-growing. Some arctic marine areas, however, have very high seasonal productivity and the sub-polar seas have the highest marine productivity in the world. The Bering and Chukchi Seas, for example, include nutrient-rich upwelling areas that support large concentrations of migratory seabirds as well as diverse communities of marine mammals. The Bering and Barents Seas support some of the world’s richest fisheries.
The marine ecosystems of the Arctic provide a range of ecosystem services that are of fundamental importance for the sustenance of inhabitants of arctic coastal areas. Over 150 species of fish occur in arctic and subarctic waters, and nine of these are common, almost all of which are important fishery species such as cod. Arctic marine mammals escaped the mass extinctions of the ice ages that dramatically reduced the numbers of arctic terrestrial mammal species, but many are harvested. They include predators such as the toothed whales, seals, walrus, sea otters, and the Arctic’s top predator, the polar bear. Over 60 species of migratory and resident seabirds occur in the Arctic and form some of the largest seabird populations in the world. At least one species, the great auk (Pinguinusimpennis), is now extinct because of overexploitation.
The simplicity of arctic marine ecosystems, together with the specialization of many of its species, make them potentially sensitive to environmental changes such as climatic change, exposure to higher levels of UV radiation, and increased levels of contaminants. Concomitant with these pressures is potential over-exploitation of some marine resources.
Predicted effects of global warming
The Greenland, and probably the Antarctic, ice sheets have been losing mass recently, because losses by melting and outlet glaciers exceed accumulation of snowfall. According to the Intergovernmental Panel on Climate Change (IPCC), loss of Antarctic and Greenland ice sheet mass contributed, respectively, about 0.21 ± 0.35 and 0.21 ± 0.07 mm/year to sea level rise between 1993 and 2003.
The IPCC projects that ice mass loss from melting of the Greenland ice sheet will continue to outpace accumulation of snowfall. Accumulation of snowfall on the Antarctic ice sheet is projected to outpace losses from melting. However, loss of mass on the Antarctic sheet may continue, if there is sufficient loss to outlet glaciers.
The effects on ice formations of an increasing in temperature will accelerate. When ice is melted away less light from the sun will be reflected back into space and more will be absorbed by the ocean water causing further rises in temperature. This positive ice-albedo feedback system will could become independent of climate change past a certain point which will cause huge losses of ice to the icecaps.
An ice cap climate is a polar climate where the temperature never or almost never exceeds 0 °C (32 °F). The climate covers the areas around the poles, such as Antarctica and Greenland, as well as the highest mountaintops. Such areas are covered by a permanent layer of ice and have no vegetation, but they may have animal life, that usually feeds on the oceans. Due to their high latitudes, icecap climates experience 24 hours of sunlight in the summer and no sunshine in winter, the midnight sun and polar night.
A tundra climate has a summer season with temperatures consistently above freezing for several months. This summer is enough to melt the winter ice cover, which prevents the formation of ice sheets. Because of this, tundras have vegetation, while ice caps do not.
Ice cap climate is the world’s coldest climate, and includes the coldest places on Earth. Vostok, Antarctica is the
coldest place in the world, having recorded a temperature of −89.2 °C (−128.6 °F).[3]
The constant freezing temperatures cause the formation of large ice sheets in ice cap climates. These ice sheets, however, are not static, but slowly move off the continents into the surrounding waters. New snow and ice accumulation then replaces the ice that is lost. Precipitation is nearly non-existent in ice cap climates. It is never warm enough for rain, and usually too cold to generate snow. However, wind can blow snow on to the ice sheets from nearby tundras.
The ice sheets are often miles thick. Much of the land located under the ice sheets is actually below sea level, and would be under the ocean if the ice is removed. However, it is the weight of the ice itself that forces this land below sea level. If the ice was removed, the land would rise back up in an effect called post-glacial rebound. This effect is creating new land in formerly ice cap areas such as Sweden.
The extreme pressure exerted by the ice allows for the formation of liquid water at low temperatures that would otherwise result in ice, while the ice sheet itself insulates liquid water from the cold above. The causes the formation of sub-glacial lakes, the largest being Lake Vostok in Antarctica.
