Downes Glacier
Encyclopedia
Downes Glacier is a broad tidewater glacier on the north side of Heard Island
in the southern Indian Ocean
. It flows north on both sides of Cape Bidlingmaier
to the north coast of Heard Island. To the east of Downes Glacier is Ealey Glacier
, whose terminus
is located close southeast of Cape Bidlingmaier. To the west of Downes Glacier is Challenger Glacier
, whose terminus is located at the eastern side of Corinthian Bay
, close west to Saddle Point
. Saddle Point separates Downes Glacier from Challenger Glacier.
) in 1948. Named by Antarctic Names Committee of Australia
(ANCA) for M.C. Downes, ANARE biologist at Heard Island in 1951 and 1963.
, 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.
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 moraine
s and lagoon
s, which are now available for colonization by plants and animals. 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". The marine environment surrounding the islands features diverse and distinctive benthic habitats
that support a range of species including coral
s, sponges, 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.
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 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 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.
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. 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. 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. Jacka Glacier
on the east coast of Laurens Peninsula
has also demonstrated marked recession since 1955.
Retreat of glacier fronts across Heard Island is evident when comparing aerial photograph
s taken in December 1947 with those taken on 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 cap
s on Laurens Peninsula have shrunk by 30% - 65%.
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. 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 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.
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 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 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.
Heard Island and McDonald Islands
The Heard Island and McDonald Islands are an Australian external territory and volcanic group of barren Antarctic islands, about two-thirds of the way from Madagascar to Antarctica. The group's overall size is in area and it has of coastline...
in the southern Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
. It flows north on both sides of Cape Bidlingmaier
Cape Bidlingmaier
Cape Bidlingmaier is a rocky cape at the east side of the entrance to Mechanics Bay, on the north side of Heard Island in the southern Indian Ocean. The feature appears to have been known to American sealers as Morgan's Point, as shown by Captain H.C. Chester's 1860 sketch map of the island. The...
to the north coast of Heard Island. To the east of Downes Glacier is Ealey Glacier
Ealey Glacier
Ealey Glacier is a glacier, flowing northeast from the lower slopes of the Big Ben massif to the northeast side of Heard Island in the southern Indian Ocean. Its terminus is located close southeast of Cape Bidlingmaier, between Melbourne Bluff and North Barrier. The glacier terminates in ice cliffs...
, whose terminus
Glacier terminus
A glacier terminus, or snout, is the end of a glacier at any given point in time. Although glaciers seem motionless to the observer, in reality glaciers are in endless motion and the glacier terminus is always either advancing or retreating...
is located close southeast of Cape Bidlingmaier. To the west of Downes Glacier is Challenger Glacier
Challenger Glacier
Challenger Glacier is a tidewater glacier on the north side of Heard Island in the southern Indian Ocean. Located east of Baudissin Glacier, Challenger Glacier is wide and flows into the eastern side of Corinthian Bay, close west to Saddle Point. To the east of Challenger Glacier is Downes...
, whose terminus is located at the eastern side of Corinthian Bay
Corinthian Bay
Corinthian Bay is a bay, which is wide and recedes , entered between Rogers Head and Saddle Point on the north coast of Heard Island in the southern Indian Ocean. The name appears on an early chart compiled by American sealers...
, close west to Saddle Point
Saddle Point
Saddle Point is a rocky point separating Corinthian Bay and Mechanics Bay on the north coast of Heard Island.The terminus of Challenger Glacier is located at the eastern side of Corinthian Bay, close west to Saddle Point...
. Saddle Point separates Downes Glacier from Challenger Glacier.
Discovery and naming
Surveyed by ANARE (Australian National Antarctic Research ExpeditionsAustralian National Antarctic Research Expeditions
The Australian National Antarctic Research Expeditions is the historical name for the Australian Antarctic Program administered for Australia by the Australian Antarctic Division .-The ANARE Name:...
) in 1948. Named by Antarctic Names Committee of Australia
Australian Antarctic Names and Medals Committee
The Australian Antarctic Names and Medals Committee, abbreviated AANMC, was established to advise the Government on names for features in the Australian Antarctic Territory and the sub-Antarctic territory of Heard Island and the McDonald Islands...
(ANCA) for M.C. Downes, ANARE biologist at Heard Island in 1951 and 1963.
Flora and fauna
The landscape of Heard Island and nearby McDonald Island is constantly changing due to volcanismVolcanism
Volcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....
, strong winds and waves, and climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
. Volcanic activity has been observed in this area since the mid 1980s, with fresh lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
flows on the southwest flanks of Heard Island. Satellite imagery
Satellite imagery
Satellite imagery consists of photographs of Earth or other planets made by means of artificial satellites.- History :The first images from space were taken on sub-orbital flights. The U.S-launched V-2 flight on October 24, 1946 took one image every 1.5 seconds...
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, warming of the climate is causing the retreat of glaciers
Retreat of glaciers since 1850
The retreat of glaciers since 1850 affects the availability of fresh water for irrigation and domestic use, mountain recreation, animals and plants that depend on glacier-melt, and in the longer term, the level of the oceans...
(see below section). These combined processes produce new ice-free terrestrial and freshwater ecoregions such as moraine
Moraine
A moraine is any glacially formed accumulation of unconsolidated glacial debris which can occur in currently glaciated and formerly glaciated regions, such as those areas acted upon by a past glacial maximum. This debris may have been plucked off a valley floor as a glacier advanced or it may have...
s and lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
s, which are now available for colonization by plants and animals. Heard Island has vast colonies of penguin
Penguin
Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...
s and petrel
Petrel
Petrels are tube-nosed seabirds in the bird order Procellariiformes. The common name does not indicate relationship beyond that point, as "petrels" occur in three of the four families within that group...
s, and large harems of land-based marine predators such as elephant seal
Elephant seal
Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the northern elephant seal and the southern elephant seal . Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered...
s and fur seal
Fur seal
Fur seals are any of nine species of pinnipeds in the Otariidae family. One species, the northern fur seal inhabits the North Pacific, while seven species in the Arctocephalus genus are found primarily in the Southern hemisphere...
s. Due to the very high numbers of seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s and marine mammal
Marine mammal
Marine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...
s on Heard Island, the area is considered a "biological hot spot". The marine environment surrounding the islands features diverse and distinctive benthic habitats
Benthic zone
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos. They generally live in close relationship with the substrate bottom; many such...
that support a range of species including coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
s, sponges, barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s and echinoderm
Echinoderm
Echinoderms are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone....
s. This marine environment also serves as a nursery area for a range of fishes, including some species of commercial interest.
Retreat of Heard Island glaciers
Heard Island is a heavily glacierized, subantarctic volcanic islandHigh island
In geology , a high island is an island of volcanic origin. The term can be used to distinguish such islands from low islands, whose origin is due to sedimentation or uplifting of coral reefs.-Definition and origin:...
located in the Southern Ocean
Southern Ocean
The Southern Ocean comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions...
, roughly 4000 kilometers southwest of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. 80% of the island is covered in ice, with glaciers descending from 2400 meters to sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
. Due to the steep topography
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
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
Glacier mass balance
Crucial to the survival of a glacier is its mass balance, the difference between accumulation and ablation . Climate change may cause variations in both temperature and snowfall, causing changes in mass balance. Changes in mass balance control a glacier's long term behavior and is the most...
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.
The coastal ice cliffs of Brown
Brown Glacier
Brown Glacier is a glacier just south of Round Hill on the east side of Heard Island in the southern Indian Ocean. 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...
and Stephenson
Stephenson Glacier
Stephenson Glacier is a glacier close west of Dovers Moraine on the east side of Heard Island in the southern Indian Ocean. Its terminus is between Dovers Moraine and Stephenson Lagoon, with part of the glacier flowing to Doppler Hill and Sealers Beach. To the north of Stephenson Glacier is Brown...
Glaciers, which in 1954 were over 50 feet high, had disappeared by 1963 when the glaciers terminated as much as 100 yards inland. Baudissin Glacier
Baudissin Glacier
Baudissin Glacier is a tidewater glacier on the north side of Heard Island. in the southern Indian Ocean. Located 1 nautical mile west of Challenger Glacier, Baudissin Glacier is 1.5 nautical miles wide and flows into the western part of Corinthian Bay. The terminus of Baudissin Glacier is...
on the north coast, and Vahsel Glacier
Vahsel Glacier
Vahsel Glacier is a glacier on the northwestern side of Heard Island in the southern Indian Ocean. It flows west into South West Bay, between Erratic Point and Cape Gazert. Immediately to the north of Vahsel Glacier is Schmidt Glacier, whose terminus is located between Mount Drygalski and North...
on the west coast have lost at least 100 and 200 vertical feet of ice, respectively. Winston Glacier
Winston Glacier
Winston Glacier is a glacier flowing to Winston Lagoon on the southeast side of Heard Island in the southern Indian Ocean. Its terminus is at Winston Lagoon, between Cape Lockyer and Oatt Rocks. To the northeast of Winston Glacier is Stephenson Glacier, whose terminus is located between Dovers...
, 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
Winston Lagoon
Winston Lagoon is a lagoon indenting the southeast coast of Heard Island in the southern Indian Ocean, about 1 nautical mile northeast of Cape Lockyer. The feature is roughly portrayed on an American sealer chart of the 1860 period...
show that Winston Glacier has lost at least 300 vertical feet of ice within a recent time period. Jacka Glacier
Jacka Glacier
Jacka Glacier is a long glacier which flows northeast from Hayter Peak and terminates in icefalls opposite Vanhoffen Bluff on the north side of Heard Island in the southern Indian Ocean. The glacier appears to be roughly charted on an 1860 sketch map compiled by Captain H.C. Chester, an American...
on the east coast of Laurens Peninsula
Laurens Peninsula
Laurens Peninsula is a rugged peninsula surmounted by several ice-covered peaks. It forms the northwestern part of Heard Island in the southern Indian Ocean. The name was applied by the ANARE following their survey in 1948...
has also demonstrated marked recession since 1955.
Retreat of glacier fronts across Heard Island is evident when comparing aerial photograph
Aerial photography
Aerial photography is the taking of photographs of the ground from an elevated position. The term usually refers to images in which the camera is not supported by a ground-based structure. Cameras may be hand held or mounted, and photographs may be taken by a photographer, triggered remotely or...
s taken in December 1947 with those taken on a return visit in early 1980. Retreat of Heard Island glaciers is most dramatic on the eastern section of the island, where the termini
Glacier terminus
A glacier terminus, or snout, is the end of a glacier at any given point in time. Although glaciers seem motionless to the observer, in reality glaciers are in endless motion and the glacier terminus is always either advancing or retreating...
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 cap
Ice cap
An ice cap is an ice mass that covers less than 50 000 km² of land area . Masses of ice covering more than 50 000 km² are termed an ice sheet....
s on Laurens Peninsula have shrunk by 30% - 65%.
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. 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 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.
Possible causes of glacier recession on Heard Island include:
- Volcanic activity
- Southward movement of the Antarctic ConvergenceAntarctic ConvergenceThe Antarctic Convergence is a curve continuously encircling Antarctica where cold, northward-flowing Antarctic waters meet the relatively warmer waters of the subantarctic. Antarctic waters predominantly sink beneath subantarctic waters, while associated zones of mixing and upwelling create a zone...
: such a movement conceivably might cause glacier retreat through a rise in sea and air temperatures - Climatic change
The Australian Antarctic Division
Australian Antarctic Division
The Australian Antarctic Division is an agency of the Department of Sustainability, Environment, Water, Population and Communities . The division undertakes science programs and research projects to contribute to an understanding of Antarctica and the Southern Ocean...
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
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
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
Echo sounding
Echo sounding is the technique of using sound pulses directed from the surface or from a submarine vertically down to measure the distance to the bottom by means of sound waves. This information is then typically used for navigation purposes or in order to obtain depths for charting purposes...
, 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
Global Positioning System
The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...
surface surveys
Surveying
See Also: Public Land Survey SystemSurveying or land surveying is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them...
revealed that the rate of loss of ice in both the ablation zone
Ablation zone
Ablation zone refers to the low altitude area of a glacier or ice sheet where there is a net loss in ice mass due to melting, sublimation, evaporation, or calving. The ablation zone is delineated by the equilibrium line altitude , or snow line, which separates the ablation zone and the high...
and the accumulation zone
Accumulation zone
On a glacier, the accumulation zone is the area above the firn line, where snowfall accumulates and exceeds the losses from ablation, . The annual Glacier equilibrium line separates the accumulation and ablation zone annually...
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
Dynamic equilibrium
A dynamic equilibrium exists once a reversible reaction ceases to change its ratio of reactants/products, but substances move between the chemicals at an equal rate, meaning there is no net change. It is a particular example of a system in a steady state...
. The retreat of Heard Island's glaciers is expected to continue for the foreseeable future.
External links
- Click here to see a map of Heard Island and McDonald Islands, including all major topographical features
- Australian Antarctic Division
- Australian Antarctic Gazetteer
- Composite Gazetteer of Antarctica
- Australian Antarctic Names and Medals Committee (AANMC)
- United States Geological Survey, Geographic Names Information System (GNIS)
- Scientific Committee on Antarctic Research (SCAR)