Brown Glacier: Difference between revisions
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Surveyed by ANARE ([[Australian National Antarctic Research Expeditions]]) in 1948. Named by [[Antarctic Names Committee of Australia]] (ANCA) for [[K.G. Brown]], ANARE biologist on Heard Island in 1951. |
Surveyed by ANARE ([[Australian National Antarctic Research Expeditions]]) in 1948. Named by [[Antarctic Names Committee of Australia]] (ANCA) for [[K.G. Brown]], ANARE biologist on Heard Island in 1951. |
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==Flora and fauna== |
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{{main|List of flora and fauna of Heard Island}} |
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The landscape of Heard Island and nearby McDonald Island is constantly changing due to [[volcanism]], strong winds and waves, and [[climate change]]. Volcanic activity has been observed in this area since 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.<ref name=aad2008>{{cite web |
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|author= |
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|date=08 October 2008 |
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|url=http://www.aad.gov.au/default.asp?casid=35356 |
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|title='Big brother' monitors glacial retreat in the sub-Antarctic |
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|publisher=[http://www.aad.gov.au/ Australian Antarctic Division] |
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|location=Kingston, Tasmania, Australia |
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|accessdate=07 June 2010}}</ref> |
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In addition to new land being produced by volcanism, warming of the climate is causing the [[Retreat of glaciers since 1850|retreat of glaciers]] (''see below section''). These combined processes produce new ice-free [[Ecoregion#Terrestrial|terrestrial]] and [[Ecoregion#Freshwater|freshwater]] ecoregions such as [[moraine]]s and [[lagoon]]s, which are now available for colonization by plants and animals.<ref name=aad2008/> Heard Island has vast colonies of [[penguin]]s and [[petrel]]s, and large harems of land-based marine predators such as [[elephant seal]]s and [[fur seal]]s. Due to the very high numbers of [[seabird]]s and [[marine mammal]]s on Heard Island, the area is considered a "biological hot spot".<ref name=aad2008/> The marine environment surrounding the islands features diverse and distinctive [[Benthic zone|benthic habitats]] that support a range of species including [[coral]]s, [[sponge]]s, [[barnacle]]s and [[echinoderm]]s. This marine environment also serves as a nursery area for a range of fishes, including some species of commercial interest.<ref name=aad2008/> |
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==Retreat of Heard Island glaciers== |
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{{See also|Retreat of glaciers since 1850|Glacier mass balance}} |
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Heard Island is a heavily glacierized, subantarctic [[High island|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]].<ref name=Allis1986/> Due to the steep [[topography]] of Heard Island, most of its glaciers are relatively thin (averaging only about 55 meters in depth).<ref name=Ruddell/> The presence of glaciers on Heard Island provides an excellent opportunity to measure the rate of glacial retreat as an indicator of climate change.<ref name=aad2008/> |
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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 the ice formations above 5000 feet on the southwestern slopes of Big Ben, possibly as a result of volcanic activity. By 1963, major recession was obvious below 2000 feet on almost all glaciers, and minor recession was evident as high as 5000 feet.<ref name=Budd1970>{{cite journal |
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|author=G.M. Budd, P.J. Stephenson |
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|title=Recent glacier retreat on Heard Island |
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|journal=International Association for Scientific Hydrology |
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|volume=86 |
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|issue= |
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|pages=449-458 |
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|date=1970 |
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|pmid= |
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|doi= |
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|url=http://iahs.info/redbooks/a086/086046.pdf |
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|accessdate=07 June 2010}}</ref> |
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The coastal ice cliffs of [[Brown Glacier|Brown]] and [[Stephenson Glacier|Stephenson]] Glaciers, which in 1954 were over 50 feet high, had disappeared by 1963 when the glaciers terminated as much as 100 yards inland.<ref name=Budd1970/> [[Baudissin Glacier]] on the north coast, and [[Vahsel Glacier]] on the west coast have lost at least 100 and 200 vertical feet of ice, respectively.<ref name=Budd1970/> [[Winston Glacier]], which retreated approximately one mile 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 of ice within a recent time period.<ref name=Budd1970/> [[Jacka Glacier]] on the east coast of [[Laurens Peninsula]] has also demonstrated marked recession since 1955.<ref name=Budd1970/> |
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Retreat of glacier fronts across Heard Island is evident when comparing [[Aerial photography|aerial photograph]]s taken in December 1947 with those taken on a return visit in early 1980.<ref name=Allis1986/><ref name=Thost2008/> Retreat of Heard Island glaciers is most dramatic on the eastern section of the island, where the [[Glacier terminus|termini]] of former [[tidewater glacier]]s are now located inland.<ref name=Allis1986/> Glaciers on the northern and western coasts have narrowed significantly, while the area of glaciers and [[ice cap]]s on Laurens Peninsula have shrunk by 30% - 65%.<ref name=Allis1986/><ref name=Ruddell/> |
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During the time period between 1947 and 1988, the total area of Heard Island's glaciers decreased by 11%, from 288 km² (roughly 79% of the total area of Heard Island) to only 257 km².<ref name=Ruddell/> A visit to the island in the spring of 2000 found that the Stephenson, Brown and Baudissin glaciers, among others, had retreated even further.<ref name=Ruddell/><ref name=Thost2008/> The terminus of Brown Glacier has retreated approximately 1.1 kilometres since 1950.<ref name=aad2008/> The total ice covered area of Brown Glacier is estimated to have decreased by roughly 29% between 1947 and 2004.<ref name=Thost2008/> This degree of loss of glacier mass is consistent with the measured increase in temperature of +0.9 °C over that time span.<ref name=Thost2008/> |
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Possible causes of glacier recession on Heard Island include: |
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#Volcanic activity |
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#Southward movement of the [[Antarctic Convergence]]: such a movement conceivably might cause glacier retreat through a rise in sea and air temperatures |
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#Climatic change |
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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 [[Bird|avian]] and terrestrial biology and glaciology. Glaciologists conducted further research on the Brown Glacier, in an effort to determine whether glacial retreat is rapid or punctuated. Using a portable [[Echo sounding|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 wind]]s on glacier mass balance.<ref name=heard>{{cite web |
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|author=[http://www.heardisland.aq/ Heard Island and McDonald Islands (HIMI)] |
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|date= |
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|url=http://www.heardisland.aq/history/research-expeditions/australian-research-expeditions |
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|title=Australian Research Expeditions |
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|publisher=[[Department of the Environment, Water, Heritage and the Arts]], [[Australian Antarctic Division]], Territories, Environment and Treaties Section |
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|location=Kingston, Tasmania, Australia |
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|accessdate=07 June 2010}}</ref> 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 [[Global Positioning System|GPS]] [[Surveying|surface surveys]] revealed that 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]].<ref name=Thost2008/> The retreat of Heard Island's glaciers is expected to continue for the forseeable future.<ref name=Allis1986/> |
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==References== |
==References== |
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Revision as of 04:40, 8 June 2010
Brown Glacier (53°4′S 73°39′E / 53.067°S 73.650°E) is a glacier just south of Round Hill on the east side of Heard Island. Its terminus is at Brown Lagoon. To the northwest of Brown Glacier is Compton Glacier, whose terminus is located at Compton Lagoon, between Gilchrist Beach and Fairchild Beach. To the southeast of Brown Glacier is Stephenson Glacier, whose terminus is located between Dovers Moraine and Stephenson Lagoon.
Surveyed by ANARE (Australian National Antarctic Research Expeditions) in 1948. Named by Antarctic Names Committee of Australia (ANCA) for K.G. Brown, ANARE biologist on Heard Island in 1951.
Flora and fauna
The landscape of Heard Island and nearby McDonald Island is constantly changing due to volcanism, strong winds and waves, and climate change. Volcanic activity has been observed in this area since 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.[1]
In addition to new land being produced by volcanism, warming of the climate is causing the retreat of glaciers (see below section). 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.[1] 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 the very high numbers of seabirds and marine mammals on Heard Island, the area is considered a "biological hot spot".[1] 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.[1]
Retreat of Heard Island glaciers
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.[2] Due to the steep topography of Heard Island, most of its glaciers are relatively thin (averaging only about 55 meters in depth).[3] The presence of glaciers on Heard Island provides an excellent opportunity to measure the rate of glacial retreat as an indicator of climate change.[1]
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 the ice formations above 5000 feet on the southwestern slopes of Big Ben, possibly as a result of volcanic activity. By 1963, major recession was obvious below 2000 feet on almost all glaciers, and minor recession was evident as high as 5000 feet.[4]
The coastal ice cliffs of Brown and Stephenson Glaciers, which in 1954 were over 50 feet high, had disappeared by 1963 when the glaciers terminated as much as 100 yards inland.[4] Baudissin Glacier on the north coast, and Vahsel Glacier on the west coast have lost at least 100 and 200 vertical feet of ice, respectively.[4] Winston Glacier, which retreated approximately one mile 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 of ice within a recent time period.[4] Jacka Glacier on the east coast of Laurens Peninsula has also demonstrated marked recession since 1955.[4]
Retreat of glacier fronts across Heard Island is evident when comparing aerial photographs taken in December 1947 with those taken on a return visit in early 1980.[2][5] 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.[2] 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%.[2][3]
During the time period between 1947 and 1988, the total area of Heard Island's glaciers decreased by 11%, from 288 km² (roughly 79% of the total area of Heard Island) to only 257 km².[3] A visit to the island in the spring of 2000 found that the Stephenson, Brown and Baudissin glaciers, among others, had retreated even further.[3][5] The terminus of Brown Glacier has retreated approximately 1.1 kilometres since 1950.[1] The total ice covered area of Brown Glacier is estimated to have decreased by roughly 29% between 1947 and 2004.[5] This degree of loss of glacier mass is consistent with the measured increase in temperature of +0.9 °C over that time span.[5]
Possible causes of glacier recession on Heard Island include:
- Volcanic activity
- Southward movement of the Antarctic Convergence: such a movement conceivably might cause glacier retreat through a rise in sea and air temperatures
- Climatic change
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 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.[6] 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 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.[5] The retreat of Heard Island's glaciers is expected to continue for the forseeable future.[2]
References
- ^ a b c d e f "'Big brother' monitors glacial retreat in the sub-Antarctic". Kingston, Tasmania, Australia: Australian Antarctic Division. 08 October 2008. Retrieved 07 June 2010.
{{cite web}}: Check date values in:|accessdate=and|date=(help); External link in|publisher= - ^ a b c d e Cite error: The named reference
Allis1986was invoked but never defined (see the help page). - ^ a b c d Cite error: The named reference
Ruddellwas invoked but never defined (see the help page). - ^ a b c d e G.M. Budd, P.J. Stephenson (1970). "Recent glacier retreat on Heard Island" (PDF). International Association for Scientific Hydrology. 86: 449–458. Retrieved 07 June 2010.
{{cite journal}}: Check date values in:|accessdate=(help) - ^ a b c d e Cite error: The named reference
Thost2008was invoked but never defined (see the help page). - ^ Heard Island and McDonald Islands (HIMI). "Australian Research Expeditions". Kingston, Tasmania, Australia: Department of the Environment, Water, Heritage and the Arts, Australian Antarctic Division, Territories, Environment and Treaties Section. Retrieved 07 June 2010.
{{cite web}}: Check date values in:|accessdate=(help); External link in|author=
"Brown Glacier". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. Retrieved 31 May 2010.
This article incorporates public domain material from "Brown Glacier". Geographic Names Information System. United States Geological Survey.
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