Misplaced Pages

#440559

55-773: The subantarctic zone is a region in the Southern Hemisphere , located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° and 60° south of the Equator . The subantarctic region includes many islands in the southern parts of the Atlantic , Indian , and Pacific oceans, especially those situated north of the Antarctic Convergence . Subantarctic glaciers are, by definition, located on islands within

110-463: A carbon sink , absorbing atmospheric carbon dioxide and storing it in solution. If the SAMW temperature increases as a result of climate change , the SAMW will have less capacity to store dissolved carbon dioxide. Research using a computerized climate system model suggests that if atmospheric carbon dioxide concentration were to increase to 860 ppm by the year 2100 (roughly double today's concentration),

165-411: A concept of physiographic regions while a conflicting trend among geographers was to equate physiography with "pure morphology," separated from its geological heritage. In the period following World War II, the emergence of process, climatic, and quantitative studies led to a preference by many Earth scientists for the term "geomorphology" in order to suggest an analytical approach to landscapes rather than

220-437: A descriptive one. In current usage, physiography still lends itself to confusion as to which meaning is meant, the more specialized "geomorphological" definition or the more encompassing "physical geography" definition. For the purposes of physiographic mapping, landforms are classified according to both their geologic structures and histories. Distinctions based on geologic age also correspond to physiographic distinctions where

275-414: A recent time period. The glaciers of Laurens Peninsula, whose maximum elevation is only 500 m above sea level, are smaller and shorter than most of the other Heard Island glaciers, and therefore much more sensitive to temperature effects. Accordingly, their total area has decreased by over 30 percent. Jacka Glacier on the east coast of Laurens Peninsula has also demonstrated marked recession since 1955. In

330-404: A return visit in early 1980. Retreat of Heard Island glaciers is most dramatic on the eastern section of the island, where the termini of former tidewater glaciers are now located inland. Glaciers on the northern and western coasts have narrowed significantly, while the area of glaciers and ice caps on Laurens Peninsula have shrunk by 30% – 65%. During the time period between 1947 and 1988,

385-601: A unique environment, noted for its very high marine productivity , especially for antarctic krill . Because of this, all lands and waters situated south of the Antarctic Convergence are considered to belong to the Antarctic from a climatological , biological and hydrological standpoint. However, the text of the Antarctic Treaty , article VI ("Area covered by Treaty") states: "The provisions of

440-763: Is a geographic zone, the Subantarctic Zone (SAZ). South of the SAZ is the Subantarctic Front (SAF). South of the SAF is another marine zone, called the Polar Frontal Zone (PFZ). The SAZ and the PFZ together form the subantarctic region. The southernmost boundary of the PFZ (and hence, the southern border of the subantarctic region) is the Antarctic Convergence, located approximately 200 kilometers south of

495-520: Is also well documented. Many subantarctic glaciers are also in retreat. Mass balance is significantly negative on many glaciers on Kergeulen Island, Heard Island, South Georgia and Bouvet Island. Heard Island is a heavily glacierized, subantarctic volcanic island located in the Southern Ocean , roughly 4000 kilometers southwest of Australia . 80% of the island is covered in ice, with glaciers descending from 2400 meters to sea level . Due to

550-496: Is characterized by tundra, permafrost , and volcanoes . These islands are situated close to or south of the Antarctic Convergence, but north of 60° S latitude (the continental limit according to the Antarctic Treaty). Therefore, although some are located south of the Antarctic Convergence, they should still be considered as subantarctic islands by virtue of their location north of 60° S. At between 60° – 69° south of

605-772: Is debatable whether these islands should be considered as such because their climate and geography differs significantly from other subantarctic islands. At between 52° – 57° south of the Equator, the Campbell Island Group , Heard Island and McDonald Islands , Bouvet Island , the South Georgia Group , Macquarie Island , and the South Sandwich Islands are also located in the Furious Fifties. The geography of these islands

SECTION 10

#1732772548441

660-483: Is estimated to have decreased by roughly 29% between 1947 and 2004. This degree of loss of glacier mass is consistent with the measured increase in temperature of +0.9 °C over that time span. The coastal ice cliffs of Brown Glacier and Stephenson Glacier, which in 1954 were over 50 feet (15 m) high, had disappeared by 1963 when the glaciers terminated as much as 100 yards (91 m) inland. Baudissin Glacier on

715-469: Is intimately associated with certain branches of geology, as sedimentation , while geomorphology connects physiography with geography. The dynamic interlude representing the active phase of physiography weaves the basic threads of geologic history." The U.S. Geological Survey defines physiography as a study of "Features and attributes of earth's land surface", while geomorphology is defined separately as "Branch of geology dealing with surface land features and

770-474: Is sometimes as the science which describes and explains the physical features of the earth's surface". By 1911, the definition of physiography in Encyclopædia Britannica had evolved to be "In popular usage the words 'physical geography' have come to mean geography viewed from a particular standpoint rather than any special department of the subject. The popular meaning is better conveyed by

825-626: Is that portion of the global ocean circulation that is driven by global density gradients created by surface heat and evaporation . Several distinct water masses converge in the immediate vicinity of the APF or Antarctic Convergence (in particular the Subantarctic Surface Water (Subantarctic Mode Water or SAMW), Antarctic Surface Water , and the Antarctic Intermediate Water ). This convergence creates

880-735: The Antarctic Polar Front (APF). The subantarctic Front, found between 48°S and 58°S in the Indian and Pacific Ocean and between 42°S and 48°S in the Atlantic Ocean, defines the northern boundary of the Antarctic Circumpolar Current (or ACC). The ACC is the most important ocean current in the Southern Ocean , and the only current that flows completely around the Earth. Flowing eastward through

935-864: The Kerguelen Islands , the Antipodes Islands , and the Auckland Islands . The geography of these islands is characterized by tundra, with some trees on the Snares Islands and the Auckland Islands. These islands are all located near the Antarctic Convergence (with the Kerguelen Islands south of the Convergence) and are properly considered to be subantarctic islands. At between 51° – 56° south of

990-577: The South Orkney Islands , which are about 54 km south of the parallel, and Thule Island and Cook Island of the South Sandwich Islands , which both are about 57 km north of the parallel (with Cook Island slightly closer). The parallel marks the northern limit of the Southern Ocean (though some organisations and countries, notably Australia , have other definitions) and of the Antarctic Treaty System . It also marks

1045-400: The 21st century, some confusion remains as to exactly what "physiography" is. One source states "Geomorphology includes quaternary geology, physiography and most of physical geography", treating physiography as a separate field, but subservient to geomorphology. Another source states "Geomorphology (or physiography) refers to the study of the surface features of the earth. It involves looking at

1100-549: The Brown Glacier, in an effort to determine whether glacial retreat is rapid or punctuated. Using a portable echo sounder , the team took measurements of the volume of the glacier. Monitoring of climatic conditions continued, with an emphasis on the impact of Foehn winds on glacier mass balance. Based on the findings of that expedition, the rate of loss of glacier ice on Heard Island appears to be accelerating. Between 2000 and 2003, repeat GPS surface surveys revealed that

1155-475: The Equator, in the region often referred to as the Shrieking Sixties , the South Orkney Islands , South Shetland Islands , Balleny Islands , Scott Island , and Peter I Island are all properly considered to be Antarctic islands for the following three reasons: In light of the above considerations, the following should be considered to be subantarctic islands : This is a list of glaciers in

SECTION 20

#1732772548441

1210-663: The Equator, the Falkland Islands , Isla de los Estados , Ildefonso Islands , Diego Ramírez Islands , and other islands associated with Tierra del Fuego and Cape Horn , lie north of the Antarctic Convergence in the region often referred to as the Furious Fifties . Unlike other subantarctic islands, these islands have trees , temperate grasslands (mostly tussac grass ), and even arable land . They also lack tundra and permanent snow and ice at their lowest elevations. Despite their more southerly location, it

1265-708: The SAMW will decrease in density and salinity. The resulting reductions in the subduction and transport capacity of SAMW and AAIW water masses could potentially decrease the absorption and storage of CO 2 in the Southern Ocean. The Antarctic realm and Antarctic Floristic Kingdom include most of the subantarctic islands native biota , with many endemic genera and species of flora and fauna . The physical landscape and biota communities of Heard Island and McDonald Islands are constantly changing due to volcanism , strong winds and waves, and climate change . Volcanic activity has been observed in this area since

1320-634: The Screaming 60s due to the prevailing high-speed, westerly winds which can generate large waves in excess of 15 m (50 ft) and peak wind speeds over 145 km/h (90 mph). The maximum altitude of the Sun is > 15.00º in April and > 8.00º in May. The lowest latitude where white nights can be observed is approximately on this parallel. During the summer solstice, nighttime does not get beyond nautical twilight ,

1375-403: The case. A maturely dissected plateau may grade without a break from rugged mountains on the one hand to mildly rolling farm lands on the other. So also, forms which are not classified together may be superficially similar; for example, a young coastal plain and a peneplain . In a large number of cases, the boundary lines are also geologic lines, due to differences in the nature or structure of

1430-422: The definition of the term physiography. "In England, physiography is regarded as the introduction to physical science in general. It is made to include the elements of physics , chemistry , astronomy , physical geography, and geology , and sometimes even certain phases of botany and zoology . In America, the term has a somewhat different meaning. It is sometimes used as a synonym for physical geography, and

1485-401: The distribution of land, water, soil and rock material that forms the land surface. Land is closely linked to the geomorphology of a particular landscape", regarding physiography as synonymous with geomorphology. Yet another source states "Physiography may be viewed from two distinct angles, the one dynamic, the other passive". The same source continues by stating "In a large fashion geodynamics

1540-418: The early 1900s, the study of regional-scale geomorphology was termed "physiography". Physiography later was considered to be a portmanteau of " physi cal" and "ge ography ", and therefore synonymous with physical geography , and the concept became embroiled in controversy surrounding the appropriate concerns of that discipline. Some geomorphologists held to a geological basis for physiography and emphasized

1595-512: The early 1950s, Jacka Glacier had receded only slightly from its position in the late 1920s, but by 1997 it had receded about 700 m back from the coastline. Possible causes of glacier recession on Heard Island include: The Australian Antarctic Division conducted an expedition to Heard Island during the austral summer of 2003–04. A small team of scientists spent two months on the island, conducting studies on avian and terrestrial biology and glaciology. Glaciologists conducted further research on

1650-418: The facts of mathematical geography, and the three are so closely inter-related that they cannot be rigidly separated in any discussion". The 1919 edition of The Encyclopedia Americana: A Library of Universal Knowledge further adjusted the definition to be "Physiography (geomorphology), now generally recognized as a science distinct from geology, deals with the origins and development of land forms, traces out

1705-488: The field. In Germany, Oscar Peschel in 1870, proposed that geographers should study the morphology of the Earth's surface, having an interest in the study of landforms for the development of human beings. As the chair of geography (and a geologist by training) in Bonn, Germany, Ferdinand von Richthofen made the study of landforms the main research field for himself and his students. Elsewhere, Thomas Henry Huxley 's Physiography

Subantarctic - Misplaced Pages Continue

1760-400: The forms are so recent as to be in their first erosion cycle , as is generally the case with sheets of glacial drift . Generally, forms which result from similar histories are characterized by certain similar features, and differences in history result in corresponding differences of form, usually resulting in distinctive features which are obvious to the casual observer, but this is not always

1815-432: The history of geologic changes" to descriptions that also include vegetation and/or land use. 60th parallel south Download coordinates as: The 60th parallel south is a circle of latitude that is 60 degrees south of Earth 's equatorial plane . No land lies on the parallel—it crosses nothing but ocean. The closest land is a group of rocks north of Coronation Island (Melson Rocks or Governor Islands) of

1870-491: The ice formations above 5,000 feet (1,500 m) on the southwestern slopes of Big Ben , possibly as a result of volcanic activity . By 1963, major recession was obvious below 2,000 feet (610 m) on almost all glaciers, and minor recession was evident as high as 5,000 feet (1,500 m). Retreat of glacier fronts across Heard Island is evident when comparing aerial photographs taken in December 1947 with those taken on

1925-750: The mid-1980s, with fresh lava flows on the southwest flanks of Heard Island. Satellite imagery shows that McDonald Island increased in size from about 1 to 2.5 square kilometers between 1994 and 2004, as a result of volcanic activity. In addition to new land being produced by volcanism, global warming of the climate is causing the retreat of glaciers on the islands ( see section below ). These combined processes produce new ice-free terrestrial and freshwater ecoregions , such as moraines and lagoons , which are now available for colonization by plants and animals. Heard Island has vast colonies of penguins and petrels , and large harems of land-based marine predators such as elephant seals and fur seals . Due to

1980-466: The north coast has lost at least 100 vertical feet (30 vertical m), and Vahsel Glacier on the west coast has lost at least 200 vertical feet (61 vertical m). Winston Glacier , which retreated approximately one mile (1.6 km) between 1947 and 1963, appears to be a very sensitive indicator of glacier change on the island. The young moraines flanking Winston Lagoon show that Winston Glacier has lost at least 300 vertical feet (91 vertical m) of ice within

2035-743: The present Treaty shall apply to the area south of 60° South latitude ". Therefore, Antarctica is defined from a political standpoint as all land and ice shelves south of 60°S latitude. At between about 46° – 50° south of the Equator, in the region often referred to as the Roaring Forties , are the Crozet Islands , the Prince Edward Islands , Wager Island , the Bounty Islands , the Snares Islands ,

2090-447: The processes of contemporary change in the crust and the circulation of the fluid envelopes. It thus draws upon physics for the explanation of the phenomena with the space-relations of which it is specially concerned. Physical geography naturally falls into three divisions, dealing respectively with the surface of the lithosphere – geomorphology; the hydrosphere – oceanography ; and the atmosphere – climatology . All these rest upon

2145-501: The processes that create and change them". Partly due to this confusion over what "physiography" actually means, some scientists have refrained from using the term physiography (and instead use the similar term geomorphology) because the definitions vary from the American Geological Institute's "the study and classification of the surface features of Earth on the basis of similarities in geologic structure and

2200-480: The rate of loss of ice in both the ablation zone and the accumulation zone of Brown Glacier was more than double average rate measured from 1947 to 2003. The increase in the rate of ice loss suggests that the glaciers of Heard Island are reacting to ongoing climate change, rather than approaching dynamic equilibrium . The retreat of Heard Island's glaciers is expected to continue for the foreseeable future. Download coordinates as: Physiographic regions of

2255-716: The southern boundary of the South Pacific Nuclear-Weapon-Free Zone and the Latin American Nuclear-Weapon-Free Zone . At this latitude the sun is visible for 18 hours, 52 minutes during the December solstice and 5 hours, 52 minutes during the June solstice. On December 21, the sun is at 53.44 degrees up in the sky and 6.56 degrees on June 21. The sun's altitude is exactly 30 degrees at either equinox. The latitudes south of this parallel are often referred to as

Subantarctic - Misplaced Pages Continue

2310-961: The southern hemisphere. With respect to glaciers of the Andes mountains in South America , abundant evidence has been collected from ongoing research at Nevado del Ruiz in Colombia , Quelccaya Ice Cap and Qori Kalis Glacier in Peru , Zongo , Chacaltaya and Charquini glaciers in Bolivia , the Aconcagua River Basin in the central Chilean Andes , and the Northern Patagonian and Southern Patagonian ice fields . Retreat of glaciers in New Zealand and Antarctica

2365-506: The southern portions of the Atlantic, Indian, and Pacific Oceans, the ACC links these three otherwise separate oceanic basins . Extending from the sea surface to depths of 2000–4000 meters, and with a width of as great as 2000 kilometers, the ACC transports more water than any other ocean current. The ACC carries up to 150 Sverdrups (150 million cubic meters per second), equivalent to 150 times

2420-437: The steep topography of Heard Island, most of its glaciers are relatively thin (averaging only about 55 meters in depth). The presence of glaciers on Heard Island provides an excellent opportunity to measure the rate of glacial retreat as an indicator of climate change. Available records show no apparent change in glacier mass balance between 1874 and 1929. Between 1949 and 1954, marked changes were observed to have occurred in

2475-536: The subantarctic . This list includes one snow field ( Murray Snowfield ). Snow fields are not glaciers in the strict sense of the word, but they are commonly found at the accumulation zone or head of a glacier. For the purposes of this list, Antarctica is defined as any latitude further south than 60° (the continental limit according to the Antarctic Treaty). Together, the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) act as

2530-529: The subantarctic region. All glaciers located on the continent of Antarctica are by definition considered to be Antarctic glaciers . The subantarctic region comprises two geographic zones and three distinct fronts . The northernmost boundary of the subantarctic region is the rather ill-defined Subtropical Front (STF), also referred to as the Subtropical Convergence. To the south of the STF

2585-434: The topographic expression of structure, and embodies a logical history of oceanic basins, and continental elevations; of mountains , plateaus and plains ; of hills and valleys. Physical geography is used loosely as a synonym, but the term is more properly applied to the borderland between geography and physiography; dealing, as it does, largely with the human element as influenced by its physiographic surroundings". Even in

2640-481: The total area of Heard Island's glaciers decreased by 11%, from 288 km (roughly 79% of the total area of Heard Island) to only 257 km. A visit to the island in the spring of 2000 found that the Stephenson , Brown and Baudissin glaciers, among others, had retreated even further. The terminus of Brown Glacier has retreated approximately 1.1 kilometres since 1950. The total ice-covered area of Brown Glacier

2695-484: The underlying rocks. The history of "physiography" itself is at best a complicated effort. Much of the complications arise from how the term has evolved over time, both as its own 'science' and as a synonym for other branches of science. In 1848, Mary Somerville published her book Physical Geography which gave detailed descriptions of the topography of each continent, along with the distribution of plant, animals and humans. This work gave impetus to further works along

2750-508: The very high numbers of seabirds and marine mammals on Heard Island, the area is considered a "biological hot spot". The marine environment surrounding the islands features diverse and distinctive benthic habitats that support a range of species including corals , sponges , barnacles and echinoderms . This marine environment also serves as a nursery area for a range of fishes, including some species of commercial interest. Glaciers are currently retreating at significant rates throughout

2805-440: The volume of water flowing in all the world's rivers. The ACC and the global thermohaline circulation strongly influence regional and global climate as well as underwater biodiversity . Another factor that contributes to the climate of the subantarctic region, though to a much lesser extent than the thermohaline circulation, is the formation of Antarctic Bottom Water (ABW) by halothermal dynamics . The halothermal circulation

SECTION 50

#1732772548441

2860-476: The word physiography, a term which appears to have been introduced by Linnaeus , and was reinvented as a substitute for the cosmography of the Middle Ages by Professor Huxley. Although the term has since been limited by some writers to one particular part of the subject, it seems best to maintain the original and literal meaning. In the stricter sense, physical geography is that part of geography which involves

2915-638: The world The classification mechanism has become a popular geographical tool in the United States, indicated by the publication of a USGS shapefile that maps the regions of the original work and the National Park Services's use of the terminology to describe the regions in which its parks are located. Originally used in North America , the model became the basis for similar classifications of other continents. During

2970-604: Was published in 1877 in Britain . Shortly after, the field of "physical geography" itself was renamed as "physiography". Afterwards, physiography became a very popular school subject in Britain, accounting for roughly 10% of all examination papers in both English and Welsh schools, and physiography was now regarded as an integral, if not the most important aspect of geography. In conjunction with these 'advances' in physiography, physically and visually mapping these descriptive areas

3025-645: Was underway as well. The early photographers and balloonists, Nadar and Triboulet, experimented with aerial photography and the view it provided of the landscape. In 1899, Albert Heim published his photographs and observations made during a balloon flight over the Alps; he is probably the first person to use aerial photography in geomorphological or physiographical research. The block diagrams of Fenneman, Raisz, Lobeck and many others were based in part upon both aerial photography and topographic maps, giving an oblique "birds-eye" view. By 1901, there were clear differences in

#440559