Southern Ocean
Ocean around Antarctica
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the world ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is the second-smallest of the five principal oceanic divisions, smaller than the Pacific, Atlantic and Indian oceans, and larger than the Arctic Ocean.
The maximum depth of the Southern Ocean, using the definition that it lies south of 60th parallel, was surveyed by the Five Deeps Expedition in early February 2019. The expedition's multibeam sonar team identified the deepest point at 60° 28' 46"S, 025° 32' 32"W, with a depth of . The expedition leader and chief submersible pilot Victor Vescovo, has proposed naming this deepest point the "Factorian Deep", based on the name of the crewed submersible "DSV Limiting Factor", in which he successfully visited the bottom for the first time on February 3, 2019.
By way of his voyages in the 1770s, James Cook proved that waters encompassed the southern latitudes of the globe. Yet, geographers have often disagreed on whether the Southern Ocean should be defined as a body of water bound by the seasonally fluctuating Antarctic Convergence — an oceanic zone where cold, northward flowing waters from the Antarctic mix with warmer Subantarctic waters — or not defined at all, with its waters instead treated as the southern limits of the Pacific, Atlantic, and Indian oceans. The International Hydrographic Organization (IHO) finally settled the debate after the full importance of Southern Ocean overturning circulation had been ascertained, and the term "Southern Ocean" now defines the body of water which lies south of the northern limit of that circulation.
The Southern Ocean overturning circulation is important because it makes up the second half of the global thermohaline circulation, after the better known Atlantic meridional overturning circulation (AMOC). Much like AMOC, it has also been substantially affected by climate change, in ways that have increased ocean stratification, and which may also result in the circulation substantially slowing or even passing a tipping point and collapsing outright. The latter would have adverse impacts on global weather and the function of marine ecosystems here, unfolding over centuries. The ongoing warming is already changing marine ecosystems here.
Definition and term use.
Borders and names for oceans and seas were internationally agreed when the International Hydrographic Bureau, the precursor to the IHO, convened the First International Conference on 24 July 1919. The IHO then published these in its "Limits of Oceans and Seas", the first edition being 1928. Since the first edition, the limits of the Southern Ocean have moved progressively southward; since 1953, it has been omitted from the official publication and left to local hydrographic offices to determine their own limits.
The IHO included the ocean and its definition as the waters south of the 60th parallel south in its 2000 revisions, but this has not been formally adopted, due to continuing impasses about some of the content, such as the naming dispute over the Sea of Japan. The 2000 IHO definition was circulated as a draft edition in 2002, and is used by some within the IHO and other organizations, such as the "CIA World Factbook" and Merriam-Webster.
The Australian Government regards the Southern Ocean as lying immediately south of Australia (see <templatestyles src="Crossreference/styles.css" />).
The National Geographic Society recognized the ocean officially in June 2021. Prior to this, it depicted it in a typeface different from the other world oceans; instead, it showed the Pacific, Atlantic, and Indian Oceans extending to Antarctica on both its print and online maps. Map publishers using the term Southern Ocean on their maps include Hema Maps and GeoNova.
Pre-20th century.
"Southern Ocean" is an obsolete name for the Pacific Ocean or South Pacific, coined by the Spanish explorer Vasco Núñez de Balboa, the first European to discover the Pacific, who approached it from the north in Panama. The "South Seas" is a less archaic synonym. A 1745 British Act of Parliament established a prize for discovering a Northwest Passage to "the Western and Southern Ocean of "America"".
Authors using "Southern Ocean" to name the waters encircling the unknown southern polar regions used varying limits. James Cook's account of his second voyage implies New Caledonia borders it. Peacock's 1795 "Geographical Dictionary" said it lay "to the southward of America and Africa"; John Payne in 1796 used 40 degrees as the northern limit; the 1827 "Edinburgh Gazetteer" used 50 degrees. The "Family Magazine" in 1835 divided the "Great Southern Ocean" into the "Southern Ocean" and the "Antarctick ["sic"] Ocean" along the Antarctic Circle, with the northern limit of the Southern Ocean being lines joining Cape Horn, the Cape of Good Hope, Van Diemen's Land and the south of New Zealand.
The United Kingdom's "South Australia Act 1834" described the waters forming the southern limit of the new province of South Australia as "the Southern Ocean". The Colony of Victoria's "Legislative Council Act 1881" delimited part of the division of Bairnsdale as "along the New South Wales boundary to the Southern ocean".
1928 delineation.
In the 1928 first edition of "Limits of Oceans and Seas", the Southern Ocean was delineated by land-based limits: Antarctica to the south, and South America, Africa, Australia, and Broughton Island, New Zealand to the north.
The detailed land-limits used were from Cape Horn in Chile eastward to Cape Agulhas in Africa, then further eastward to the southern coast of mainland Australia to Cape Leeuwin, Western Australia. From Cape Leeuwin, the limit then followed eastward along the coast of mainland Australia to Cape Otway, Victoria, then southward across Bass Strait to Cape Wickham, King Island, along the west coast of King Island, then the remainder of the way south across Bass Strait to Cape Grim, Tasmania.
The limit then followed the west coast of Tasmania southward to the South East Cape and then went eastward to Broughton Island, New Zealand, before returning to Cape Horn.
1937 delineation.
The northern limits of the Southern Ocean were moved southward in the IHO's 1937 second edition of the "Limits of Oceans and Seas". From this edition, much of the ocean's northern limit ceased to abut land masses.
In the second edition, the Southern Ocean then extended from Antarctica northward to latitude 40°S between Cape Agulhas in Africa (long. 20°E) and Cape Leeuwin in Western Australia (long. 115°E), and extended to latitude 55°S between Auckland Island of New Zealand (165 or 166°E east) and Cape Horn in South America (67°W).
As is discussed in more detail below, prior to the 2002 edition the limits of oceans explicitly excluded the seas lying within each of them. The Great Australian Bight was unnamed in the 1928 edition, and delineated as shown in the figure above in the 1937 edition. It therefore encompassed former Southern Ocean waters—as designated in 1928—but was technically not inside any of the three adjacent oceans by 1937.
In the 2002 draft edition, the IHO have designated "seas" as subdivisions within "oceans", so the Bight would have still been within the Southern Ocean in 1937 if the 2002 convention were in place then. To perform direct comparisons of current and former limits of oceans it is necessary to consider, or at least be aware of, how the 2002 change in IHO terminology for "seas" can affect the comparison.
1953 delineation.
The Southern Ocean did not appear in the 1953 third edition of "Limits of Oceans and Seas", a note in the publication read:
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Instead, in the IHO 1953 publication, the Atlantic, Indian and Pacific Oceans were extended southward, the Indian and Pacific Oceans (which had not previously touched pre 1953, as per the first and second editions) now abutted at the meridian of South East Cape, and the southern limits of the Great Australian Bight and the Tasman Sea were moved northward.
2002 draft delineation.
The IHO readdressed the question of the Southern Ocean in a survey in 2000. Of its 68 member nations, 28 responded, and all responding members except Argentina agreed to redefine the ocean, reflecting the importance placed by oceanographers on ocean currents. The proposal for the name "Southern Ocean" won 18 votes, beating the alternative "Antarctic Ocean". Half of the votes supported a definition of the ocean's northern limit at the 60th parallel south—with no land interruptions at this latitude—with the other 14 votes cast for other definitions, mostly the 50th parallel south, but a few for as far north as the 35th parallel south. Notably, the Southern Ocean Observing System collates data from latitudes higher than 40 degrees south.
A draft fourth edition of "Limits of Oceans and Seas" was circulated to IHO member states in August 2002 (sometimes referred to as the "2000 edition" as it summarized the progress to 2000). It has yet to be published due to 'areas of concern' by several countries relating to various naming issues around the world – primarily the Sea of Japan naming dispute – and there have been various changes: 60 seas were given new names, and even the name of the publication was changed. A reservation had also been lodged by Australia regarding the Southern Ocean limits. Effectively, the third edition—which did not delineate the Southern Ocean leaving delineation to local hydrographic offices—has yet to be superseded.
Despite this, the fourth edition definition has partial "de facto" usage by many nations, scientists, and organisations such as the U.S. (the "CIA World Factbook" uses "Southern Ocean", but none of the other new sea names within the "Southern Ocean", such as the "Cosmonauts Sea") and Merriam-Webster, scientists and nations – and even by some within the IHO. Some nations' hydrographic offices have defined their own boundaries; the United Kingdom used the 55th parallel south for example. Other organisations favour more northerly limits for the Southern Ocean. For example, "Encyclopædia Britannica" describes the Southern Ocean as extending as far north as South America, and confers great significance on the Antarctic Convergence, yet its description of the Indian Ocean contradicts this, describing the Indian Ocean as extending south to Antarctica.
Other sources, such as the National Geographic Society, show the Atlantic, Pacific, and Indian oceans as extending to Antarctica on its maps, although articles on the National Geographic web site have begun to reference the Southern Ocean.
A radical shift from past IHO practices (1928–1953) was also seen in the 2002 draft edition when the IHO delineated "seas" as subdivisions within the boundaries of "oceans". While the IHO are often considered the authority for such conventions, the shift brought them into line with the practices of other publications (e.g. the CIA "World Fact Book") which already adopted the principle that seas are contained within oceans. This difference in practice is markedly seen for the Pacific Ocean in the adjacent figure. Thus, for example, previously the Tasman Sea between Australia and New Zealand was not regarded by the IHO as part of the Pacific, but as of the 2002 draft edition it is.
The new delineation of seas as subdivisions of oceans has avoided the need to interrupt the northern boundary of the Southern Ocean where intersected by Drake Passage which includes all of the waters from South America to the Antarctic coast, nor interrupt it for the Scotia Sea, which also extends below the 60th parallel south. The new delineation of seas has also meant that the long-time named seas around Antarctica, excluded from the 1953 edition (the 1953 map did not even extend that far south), are automatically part of the Southern Ocean.
Australian standpoint.
In Australia, cartographical authorities define the Southern Ocean as including the entire body of water between Antarctica and the south coasts of Australia and New Zealand, and up to 60°S elsewhere. Coastal maps of Tasmania and South Australia label the sea areas as "Southern Ocean" and Cape Leeuwin in Western Australia is described as the point where the Indian and Southern Oceans meet.
History of exploration.
Unknown southern land.
Exploration of the Southern Ocean was inspired by a belief in the existence of a "Terra Australis" – a vast continent in the far south of the globe to "balance" the northern lands of Eurasia and North Africa – which had existed since the times of Ptolemy. The rounding of the Cape of Good Hope in 1487 by Bartolomeu Dias first brought explorers within touch of the Antarctic cold, and proved that there was an ocean separating Africa from any Antarctic land that might exist. Ferdinand Magellan, who passed through the Strait of Magellan in 1520, assumed that the islands of Tierra del Fuego to the south were an extension of this unknown southern land. In 1564, Abraham Ortelius published his first map, "Typus Orbis Terrarum", an eight-leaved wall map of the world, on which he identified the "Regio Patalis" with "Locach" as a northward extension of the "Terra Australis", reaching as far as New Guinea.
European geographers continued to connect the coast of Tierra del Fuego with the coast of New Guinea on their globes, and allowing their imaginations to run riot in the vast unknown spaces of the south Atlantic, south Indian and Pacific oceans they sketched the outlines of the "Terra Australis Incognita" ("Unknown Southern Land"), a vast continent stretching in parts into the tropics. The search for this great south land was a leading motive of explorers in the 16th and the early part of the 17th centuries.
The Spaniard Gabriel de Castilla, who claimed having sighted "snow-covered mountains" beyond the 64° S in 1603, is recognized as the first explorer that discovered the continent of Antarctica, although he was ignored in his time.
In 1606, Pedro Fernández de Quirós took possession for the king of Spain all of the lands he had discovered in Australia del Espiritu Santo (the New Hebrides) and those he would discover "even to the Pole".
Francis Drake, like Spanish explorers before him, had speculated that there might be an open channel south of Tierra del Fuego. When Willem Schouten and Jacob Le Maire discovered the southern extremity of Tierra del Fuego and named it Cape Horn in 1615, they proved that the Tierra del Fuego archipelago was of small extent and not connected to the southern land, as previously thought. Subsequently, in 1642, Abel Tasman showed that even New Holland (Australia) was separated by sea from any continuous southern continent.
South of the Antarctic Convergence.
The visit to South Georgia by Anthony de la Roché in 1675 was the first-ever discovery of land south of the Antarctic Convergence, i.e. in the Southern Ocean/Antarctic. Soon after the voyage cartographers started to depict "Roché Island", honouring the discoverer. James Cook was aware of la Roché's discovery when surveying and mapping the island in 1775.
Edmond Halley's voyage in for magnetic investigations in the South Atlantic met the pack ice in 52° S in January 1700, but that latitude (he reached off the north coast of South Georgia) was his farthest south. A determined effort on the part of the French naval officer Jean-Baptiste Charles Bouvet de Lozier to discover the "South Land" – described by a half legendary "sieur de Gonneyville" – resulted in the discovery of Bouvet Island in 54°10′ S, and in the navigation of 48° of longitude of ice-cumbered sea nearly in 55° S in 1730.
In 1771, Yves Joseph Kerguelen sailed from France with instructions to proceed south from Mauritius in search of "a very large continent". He lighted upon a land in 50° S which he called South France, and believed to be the central mass of the southern continent. He was sent out again to complete the exploration of the new land, and found it to be only an inhospitable island which he renamed the Isle of Desolation, but which was ultimately named after him.
South of the Antarctic Circle.
The obsession of the undiscovered continent culminated in the brain of Alexander Dalrymple, the brilliant and erratic hydrographer who was nominated by the Royal Society to command the Transit of Venus expedition to Tahiti in 1769. The command of the expedition was given by the admiralty to Captain James Cook. Sailing in 1772 with "Resolution", a vessel of 462 tons under his own command and "Adventure" of 336 tons under Captain Tobias Furneaux, Cook first searched in vain for Bouvet Island, then sailed for 20 degrees of longitude to the westward in latitude 58° S, and then 30° eastward for the most part south of 60° S, a lower southern latitude than had ever been voluntarily entered before by any vessel. On 17 January 1773 the Antarctic Circle was crossed for the first time in history and the two ships reached 67° 15' S by 39° 35' E, where their course was stopped by ice.
Cook then turned northward to look for French Southern and Antarctic Lands, of the discovery of which he had received news at Cape Town, but from the rough determination of his longitude by Kerguelen, Cook reached the assigned latitude 10° too far east and did not see it. He turned south again and was stopped by ice in 61° 52′ S by 95° E and continued eastward nearly on the parallel of 60° S to 147° E. On 16 March, the approaching winter drove him northward for rest to New Zealand and the tropical islands of the Pacific. In November 1773, Cook left New Zealand, having parted company with the "Adventure", and reached 60° S by 177° W, whence he sailed eastward keeping as far south as the floating ice allowed. The Antarctic Circle was crossed on 20 December and Cook remained south of it for three days, compelled after reaching 67° 31′ S to stand north again in 135° W.
A long detour to 47° 50′ S served to show that there was no land connection between New Zealand and Tierra del Fuego. Turning south again, Cook crossed the Antarctic Circle for the third time at 109° 30′ W before his progress was once again blocked by ice four days later at 71° 10′ S by 106° 54′ W. This point, reached on 30 January 1774, was the farthest south attained in the 18th century. With a great detour to the east, almost to the coast of South America, the expedition regained Tahiti for refreshment. In November 1774, Cook started from New Zealand and crossed the South Pacific without sighting land between 53° and 57° S to Tierra del Fuego; then, passing Cape Horn on 29 December, he rediscovered Roché Island renaming it Isle of Georgia, and discovered the South Sandwich Islands (named "Sandwich Land" by him), the only ice-clad land he had seen, before crossing the South Atlantic to the Cape of Good Hope between 55° and 60°. He thereby laid open the way for future Antarctic exploration by exploding the myth of a habitable southern continent. Cook's most southerly discovery of land lay on the temperate side of the 60th parallel, and he convinced himself that if land lay farther south it was practically inaccessible and without economic value.
Voyagers rounding Cape Horn frequently met with contrary winds and were driven southward into snowy skies and ice-encumbered seas; but so far as can be ascertained none of them before 1770 reached the Antarctic Circle, or knew it, if they did.
In a voyage from 1822 to 1824, James Weddell commanded the 160-ton brig "Jane", accompanied by his second ship "Beaufoy" captained by Matthew Brisbane. Together they sailed to the South Orkneys where sealing proved disappointing. They turned south in the hope of finding a better sealing ground. The season was unusually mild and tranquil, and on 20 February 1823 the two ships reached latitude 74°15' S and longitude 34°16'45″ W the southernmost position any ship had ever reached up to that time. A few icebergs were sighted but there was still no sight of land, leading Weddell to theorize that the sea continued as far as the South Pole. Another two days' sailing would have brought him to Coat's Land (to the east of the Weddell Sea) but Weddell decided to turn back.
First sighting of land.
The first land south of the parallel 60° south latitude was discovered by the Englishman William Smith, who sighted Livingston Island on 19 February 1819. A few months later Smith returned to explore the other islands of the South Shetlands archipelago, landed on King George Island, and claimed the new territories for Britain.
In the meantime, the Spanish Navy ship "San Telmo" sank in September 1819 when trying to cross Cape Horn. Parts of her wreckage were found months later by sealers on the north coast of Livingston Island (South Shetlands). It is unknown if some survivor managed to be the first to set foot on these Antarctic islands.
The first confirmed sighting of mainland Antarctica cannot be accurately attributed to one single person. It can be narrowed down to three individuals. According to various sources, three men all sighted the ice shelf or the continent within days or months of each other: Fabian Gottlieb von Bellingshausen, a captain in the Russian Imperial Navy; Edward Bransfield, a captain in the Royal Navy; and Nathaniel Palmer, an American sailor out of Stonington, Connecticut. It is certain that the expedition, led by von Bellingshausen and Lazarev on the ships "Vostok" and "Mirny", reached a point within from Princess Martha Coast and recorded the sight of an ice shelf at that became known as the Fimbul Ice Shelf. On 30 January 1820, Bransfield sighted Trinity Peninsula, the northernmost point of the Antarctic mainland, while Palmer sighted the mainland in the area south of Trinity Peninsula in November 1820. Von Bellingshausen's expedition also discovered Peter I Island and Alexander I Island, the first islands to be discovered south of the circle.
Antarctic expeditions.
In December 1839, as part of the United States Exploring Expedition of 1838–42 conducted by the United States Navy (sometimes called "the Wilkes Expedition"), an expedition sailed from Sydney, Australia, on the sloops-of-war and , the brig , the full-rigged ship , and two schooners and . They sailed into the Antarctic Ocean, as it was then known, and reported the discovery "of an Antarctic continent west of the Balleny Islands" on 25 January 1840. That part of Antarctica was later named "Wilkes Land", a name it maintains to this day.
Explorer James Clark Ross passed through what is now known as the Ross Sea and discovered Ross Island (both of which were named for him) in 1841. He sailed along a huge wall of ice that was later named the Ross Ice Shelf. Mount Erebus and Mount Terror are named after two ships from his expedition: and .
The Imperial Trans-Antarctic Expedition of 1914, led by Ernest Shackleton, set out to cross the continent via the pole, but their ship, , was trapped and crushed by pack ice before they even landed. The expedition members survived after an epic journey on sledges over pack ice to Elephant Island. Then Shackleton and five others crossed the Southern Ocean, in an open boat called "James Caird", and then trekked over South Georgia to raise the alarm at the whaling station Grytviken.
In 1946, US Navy Rear Admiral Richard E. Byrd and more than 4,700 military personnel visited the Antarctic in an expedition called Operation Highjump. Reported to the public as a scientific mission, the details were kept secret and it may have actually been a training or testing mission for the military. The expedition was, in both military or scientific planning terms, put together very quickly. The group contained an unusually high amount of military equipment, including an aircraft carrier, submarines, military support ships, assault troops and military vehicles. The expedition was planned to last for eight months but was unexpectedly terminated after only two months. With the exception of some eccentric entries in Admiral Byrd's diaries, no real explanation for the early termination has ever been officially given.
Captain Finn Ronne, Byrd's executive officer, returned to Antarctica with his own expedition in 1947–1948, with Navy support, three planes, and dogs. He disproved the notion that the continent was divided in two and established that East and West Antarctica was one single continent, i.e. that the Weddell Sea and the Ross Sea are not connected. The expedition explored and mapped large parts of Palmer Land and the Weddell Sea coastline, and identified the Ronne Ice Shelf, named by him for his wife Jackie Ronne. He covered by ski and dog sled – more than any other explorer in history. The Ronne Antarctic Research Expedition discovered and mapped the last unknown coastline in the world and was the first Antarctic expedition to ever include women.
Post-Atlantic Treaty.
The Antarctic Treaty was signed on 1 December 1959 and came into force on 23 June 1961. Among other provisions, this treaty limits military activity in the Antarctic to the support of scientific research.
The first person to sail single-handed to Antarctica was the New Zealander David Henry Lewis, in 1972, in a steel sloop "Ice Bird".
A baby, named Emilio Marcos de Palma, was born near Hope Bay on 7 January 1978, becoming the first baby born on the continent. He also was born further south than anyone in history.
The was a cruise ship operated by the Swedish explorer Lars-Eric Lindblad. Observers point to "Explorer"'s 1969 expeditionary cruise to Antarctica as the frontrunner for today's sea-based tourism in that region. "Explorer" was the first cruise ship used specifically to sail the icy waters of the Antarctic Ocean and the first to sink there when she struck an unidentified submerged object on 23 November 2007, reported to be ice, which caused a gash in the hull. "Explorer" was abandoned in the early hours of 23 November 2007 after taking on water near the South Shetland Islands in the Southern Ocean, an area which is usually stormy but was calm at the time. "Explorer" was confirmed by the Chilean Navy to have sunk at approximately position: 62° 24′ South, 57° 16′ West, in roughly 600 m of water.
British engineer Richard Jenkins designed an unmanned saildrone that completed the first autonomous circumnavigation of the Southern Ocean on 3 August 2019 after 196 days at sea.
The first completely human-powered expedition on the Southern Ocean was accomplished on 25 December 2019 by a team of rowers comprising captain Fiann Paul (Iceland), first mate Colin O'Brady (US), Andrew Towne (US), Cameron Bellamy (South Africa), Jamie Douglas-Hamilton (UK) and John Petersen (US).
Geography.
The Southern Ocean, geologically the youngest of the oceans, was formed when Antarctica and South America moved apart, opening the Drake Passage, roughly 30 million years ago. The separation of the continents allowed the formation of the Antarctic Circumpolar Current.
With a northern limit at 60°S, the Southern Ocean differs from the other oceans in that its largest boundary, the northern boundary, does not abut a landmass (as it did with the first edition of "Limits of Oceans and Seas"). Instead, the northern limit is with the Atlantic, Indian and Pacific Oceans.
One reason for considering it as a separate ocean stems from the fact that much of the water of the Southern Ocean differs from the water in the other oceans. Water gets transported around the Southern Ocean fairly rapidly because of the Antarctic Circumpolar Current which circulates around Antarctica. Water in the Southern Ocean south of, for example, New Zealand, resembles the water in the Southern Ocean south of South America more closely than it resembles the water in the Pacific Ocean.
The Southern Ocean has typical depths of between over most of its extent with only limited areas of shallow water. The Southern Ocean's greatest depth of occurs at the southern end of the South Sandwich Trench, at 60°00'S, 024°W. The Antarctic continental shelf appears generally narrow and unusually deep, its edge lying at depths up to , compared to a global mean of .
Equinox to equinox in line with the sun's seasonal influence, the Antarctic ice pack fluctuates from an average minimum of in March to about in September, more than a sevenfold increase in area.
Subdivisions.
Subdivisions of oceans are geographical features such as "seas", "straits", "bays", "channels", and "gulfs". There are many sudivisions of the Southern Ocean defined in the never-approved 2002 draft fourth edition of the IHO publication "Limits of Oceans and Seas". In clockwise order these include (with sector):
A number of these such as the 2002 Russian-proposed "Cosmonauts Sea", "Cooperation Sea", and "Somov (mid-1950s Russian polar explorer) Sea" are not included in the 1953 IHO document which remains currently in force, because they received their names largely originated from 1962 onward. Leading geographic authorities and atlases do not use these latter three names, including the 2014 10th edition World Atlas from the United States' National Geographic Society and the 2014 12th edition of the British Times Atlas of the World, but Soviet and Russian-issued maps do.
Biggest seas.
Top large seas:
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Natural resources.
The Southern Ocean probably contains large, and possibly giant, oil and gas fields on the continental margin. Placer deposits, accumulation of valuable minerals such as gold, formed by gravity separation during sedimentary processes are also expected to exist in the Southern Ocean.
Manganese nodules are expected to exist in the Southern Ocean. Manganese nodules are rock concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. The core may be microscopically small and is sometimes completely transformed into manganese minerals by crystallization. Interest in the potential exploitation of polymetallic nodules generated a great deal of activity among prospective mining consortia in the 1960s and 1970s.
The icebergs that form each year around in the Southern Ocean hold enough fresh water to meet the needs of every person on Earth for several months. For several decades there have been proposals, none yet to be feasible or successful, to tow Southern Ocean icebergs to more arid northern regions (such as Australia) where they can be harvested.
Natural hazards.
Icebergs can occur at any time of year throughout the ocean. Some may have drafts up to several hundred meters; smaller icebergs, iceberg fragments and sea-ice (generally 0.5 to 1 m thick) also pose problems for ships. The deep continental shelf has a floor of glacial deposits varying widely over short distances.
Sailors know latitudes from 40 to 70 degrees south as the "Roaring Forties", "Furious Fifties" and "Shrieking Sixties" due to high winds and large waves that form as winds blow around the entire globe unimpeded by any land-mass. Icebergs, especially in May to October, make the area even more dangerous. The remoteness of the region makes sources of search and rescue scarce.
Physical oceanography.
Antarctic Circumpolar Current and Antarctic Convergence.
While the Southern is the second smallest ocean it contains the unique and highly energetic Antarctic Circumpolar Current which moves perpetually eastward – chasing and joining itself, and at in length – it comprises the world's longest ocean current, transporting of water – 100 times the flow of all the world's rivers.
Several processes operate along the coast of Antarctica to produce, in the Southern Ocean, types of water masses not produced elsewhere in the oceans of the Southern Hemisphere. One of these is the Antarctic Bottom Water, a very cold, highly saline, dense water that forms under sea ice. Another is Circumpolar Deep Water, a mixture of Antarctic Bottom Water and North Atlantic Deep Water.
Associated with the Circumpolar Current is the Antarctic Convergence 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 very high in nutrients. These nurture high levels of phytoplankton with associated copepods and Antarctic krill, and resultant foodchains supporting fish, whales, seals, penguins, albatrosses and a wealth of other species.
The Antarctic Convergence is considered to be the best natural definition of the northern extent of the Southern Ocean.
Upwelling.
Large-scale upwelling is found in the Southern Ocean. Strong westerly (eastward) winds blow around Antarctica, driving a significant flow of water northward. This is actually a type of coastal upwelling. Since there are no continents in a band of open latitudes between South America and the tip of the Antarctic Peninsula, some of this water is drawn up from great depths. In many numerical models and observational syntheses, the Southern Ocean upwelling represents the primary means by which deep dense water is brought to the surface. Shallower, wind-driven upwelling is also found off the west coasts of North and South America, northwest and southwest Africa, and southwest and southeast Australia, all associated with oceanic subtropical high pressure circulations.
Ross and Weddell gyres.
The Ross Gyre and Weddell Gyre are two gyres that exist within the Southern Ocean. The gyres are located in the Ross Sea and Weddell Sea respectively, and both rotate clockwise. The gyres are formed by interactions between the Antarctic Circumpolar Current and the Antarctic Continental Shelf.
Sea ice has been noted to persist in the central area of the Ross Gyre. There is some evidence that global warming has resulted in some decrease of the salinity of the waters of the Ross Gyre since the 1950s.
Due to the Coriolis effect acting to the left in the Southern Hemisphere and the resulting Ekman transport away from the centres of the Weddell Gyre, these regions are very productive due to upwelling of cold, nutrient rich water.
Observation.
Observation of the Southern Ocean is coordinated through the Southern Ocean Observing System (SOOS). This provides access to meta data for a significant proportion of the data collected in the regions over the past decades including hydrographic measurements and ocean currents. The data provision is set up to emphasize records that are related to Essential Ocean Variables (EOVs) for the ocean region south of 40°S.
Climate.
Sea temperatures vary from about −2 to 10 °C (28 to 50 °F). Cyclonic storms travel eastward around the continent and frequently become intense because of the temperature contrast between ice and open ocean. The ocean from about latitude 40 south to the Antarctic Circle has the strongest average winds found anywhere on Earth. In winter the ocean freezes outward to 65 degrees south latitude in the Pacific sector and 55 degrees south latitude in the Atlantic sector, lowering surface temperatures well below 0 degrees Celsius. At some coastal points, persistent intense drainage winds from the interior keep the shoreline ice-free throughout the winter.
Biodiversity.
Animals.
A variety of marine animals exist and rely, directly or indirectly, on the phytoplankton in the Southern Ocean. Antarctic sea life includes penguins, blue whales, orcas, colossal squids and fur seals. The emperor penguin is the only penguin that breeds during the winter in Antarctica, while the Adélie penguin breeds farther south than any other penguin. The rockhopper penguin has distinctive feathers around the eyes, giving the appearance of elaborate eyelashes. King penguins, chinstrap penguins, and gentoo penguins also breed in the Antarctic.
The Antarctic fur seal was very heavily hunted in the 18th and 19th centuries for its pelt by sealers from the United States and the United Kingdom. The Weddell seal, a "true seal", is named after Sir James Weddell, commander of British sealing expeditions in the Weddell Sea. Antarctic krill, which congregates in large schools, is the keystone species of the ecosystem of the Southern Ocean, and is an important food organism for whales, seals, leopard seals, fur seals, squid, icefish, penguins, albatrosses and many other birds.
The benthic communities of the seafloor are diverse and dense, with up to 155,000 animals found in . As the seafloor environment is very similar all around the Antarctic, hundreds of species can be found all the way around the mainland, which is a uniquely wide distribution for such a large community. Deep-sea gigantism is common among these animals.
A census of sea life carried out during the International Polar Year and which involved some 500 researchers was released in 2010. The research is part of the global Census of Marine Life (CoML) and has disclosed some remarkable findings. More than 235 marine organisms live in both polar regions, having bridged the gap of . Large animals such as some cetaceans and birds make the round trip annually. More surprising are small forms of life such as mudworms, sea cucumbers and free-swimming snails found in both polar oceans. Various factors may aid in their distribution – fairly uniform temperatures of the deep ocean at the poles and the equator which differ by no more than , and the major current systems or marine conveyor belt which transport egg and larva stages. Among smaller marine animals generally assumed to be the same in the Antarctica and the Arctic, more detailed studies of each population have often—but not always—revealed differences, showing that they are closely related cryptic species rather than a single bipolar species.
Birds.
The rocky shores of mainland Antarctica and its offshore islands provide nesting space for over 100 million birds every spring. These nesters include species of albatrosses, petrels, skuas, gulls and terns. The insectivorous South Georgia pipit is endemic to South Georgia and some smaller surrounding islands. Freshwater ducks inhabit South Georgia and the Kerguelen Islands.
The flightless penguins are all located in the Southern Hemisphere, with the greatest concentration located on and around Antarctica. Four of the 18 penguin species live and breed on the mainland and its close offshore islands. Another four species live on the subantarctic islands. Emperor penguins have four overlapping layers of feathers, keeping them warm. They are the only Antarctic animal to breed during the winter.
Fish.
There are relatively few fish species in few families in the Southern Ocean. The most species-rich family are the snailfish (Liparidae), followed by the cod icefish (Nototheniidae) and eelpout (Zoarcidae). Together the snailfish, eelpouts and notothenioids (which includes cod icefish and several other families) account for almost <templatestyles src="Fraction/styles.css" />9⁄10 of the more than 320 described fish species of the Southern Ocean (tens of undescribed species also occur in the region, especially among the snailfish). Southern Ocean snailfish are generally found in deep waters, while the icefish also occur in shallower waters.
Icefish.
Cod icefish (Nototheniidae), as well as several other families, are part of the Notothenioidei suborder, collectively sometimes referred to as icefish. The suborder contains many species with antifreeze proteins in their blood and tissue, allowing them to live in water that is around or slightly below . Antifreeze proteins are also known from Southern Ocean snailfish.
The crocodile icefish (family Channichthyidae), also known as white-blooded fish, are only found in the Southern Ocean. They lack hemoglobin in their blood, resulting in their blood being colourless. One Channichthyidae species, the mackerel icefish ("Champsocephalus gunnari"), was once the most common fish in coastal waters less than deep, but was overfished in the 1970s and 1980s. Schools of icefish spend the day at the seafloor and the night higher in the water column eating plankton and smaller fish.
There are two species from the genus "Dissostichus", the Antarctic toothfish ("Dissostichus mawsoni") and the Patagonian toothfish ("Dissostichus eleginoides"). These two species live on the seafloor deep, and can grow to around long weighing up to , living up to 45 years. The Antarctic toothfish lives close to the Antarctic mainland, whereas the Patagonian toothfish lives in the relatively warmer subantarctic waters. Toothfish are commercially fished, and overfishing has reduced toothfish populations.
Another abundant fish group is the genus "Notothenia", which like the Antarctic toothfish have antifreeze in their bodies.
An unusual species of icefish is the Antarctic silverfish ("Pleuragramma antarcticum"), which is the only truly pelagic fish in the waters near Antarctica.
Mammals.
Seven pinniped species inhabit Antarctica. The largest, the elephant seal ("Mirounga leonina"), can reach up to , while females of the smallest, the Antarctic fur seal ("Arctophoca gazella"), reach only . These two species live north of the sea ice, and breed in harems on beaches. The other four species can live on the sea ice. Crabeater seals ("Lobodon carcinophagus") and Weddell seals ("Leptonychotes weddellii") form breeding colonies, whereas leopard seals ("Hydrurga leptonyx") and Ross seals ("Ommatophoca rossii") live solitary lives. Although these species hunt underwater, they breed on land or ice and spend a great deal of time there, as they have no terrestrial predators.
The four species that inhabit sea ice are thought to make up 50% of the total biomass of the world's seals. Crabeater seals have a population of around 15 million, making them one of the most numerous large animals on the planet. The New Zealand sea lion ("Phocarctos hookeri"), one of the rarest and most localised pinnipeds, breeds almost exclusively on the subantarctic Auckland Islands, although historically it had a wider range. Out of all permanent mammalian residents, the Weddell seals live the furthest south.
There are 10 cetacean species found in the Southern Ocean: six baleen whales, and four toothed whales. The largest of these, the blue whale ("Balaenoptera musculus"), grows to long weighing 84 tonnes. Many of these species are migratory, and travel to tropical waters during the Antarctic winter.
Invertebrates.
Arthropods.
Five species of krill, small free-swimming crustaceans, have been found in the Southern Ocean. The Antarctic krill ("Euphausia superba") is one of the most abundant animal species on earth, with a biomass of around 500 million tonnes. Each individual is long and weighs over . The swarms that form can stretch for kilometres, with up to 30,000 individuals per , turning the water red. Swarms usually remain in deep water during the day, ascending during the night to feed on plankton. Many larger animals depend on krill for their own survival. During the winter when food is scarce, adult Antarctic krill can revert to a smaller juvenile stage, using their own body as nutrition.
Many benthic crustaceans have a non-seasonal breeding cycle, and some raise their young in a brood pouch. "Glyptonotus antarcticus" is an unusually large benthic isopod, reaching in length weighing . Amphipods are abundant in soft sediments, eating a range of items, from algae to other animals. The amphipods are highly diverse with more than 600 recognized species found south of the Antarctic Convergence and there are indications that many undescribed species remain. Among these are several "giants", such as the iconic epimeriids that are up to long.
Slow moving sea spiders are common, sometimes growing as large as a human hand. They feed on the corals, sponges, and bryozoans that litter the seabed.
Molluscs, urchins, squid and sponges.
Many aquatic molluscs are present in Antarctica. Bivalves such as "Adamussium colbecki" move around on the seafloor, while others such as "Laternula elliptica" live in burrows filtering the water above.
There are around 70 cephalopod species in the Southern Ocean, the largest of which is the colossal squid ("Mesonychoteuthis hamiltoni"), which at up to is among the largest invertebrate in the world. Squid makes up most of the diet of some animals, such as grey-headed albatrosses and sperm whales, and the warty squid ("Moroteuthis ingens") is one of the subantarctic's most preyed upon species by vertebrates.
The sea urchin genus "Abatus" burrow through the sediment eating the nutrients they find in it. Two species of salps are common in Antarctic waters: "Salpa thompsoni" and "Ihlea racovitzai". "Salpa thompsoni" is found in ice-free areas, whereas "Ihlea racovitzai" is found in the high-latitude areas near ice. Due to their low nutritional value, they are normally only eaten by fish, with larger animals such as birds and marine mammals only eating them when other food is scarce.
Antarctic sponges are long-lived and sensitive to environmental changes due to the specificity of the symbiotic microbial communities within them. As a result, they function as indicators of environmental health.
Environment.
Increased solar ultraviolet radiation resulting from the Antarctic ozone hole has reduced marine primary productivity (phytoplankton) by as much as 15% and has started damaging the DNA of some fish. Illegal, unreported and unregulated fishing, especially the landing of an estimated five to six times more Patagonian toothfish than the regulated fishery, likely affects the sustainability of the stock. Long-line fishing for toothfish causes a high incidence of seabird mortality.
International agreements.
All international agreements regarding the world's oceans apply to the Southern Ocean. It is also subject to several regional agreements:
The Southern Ocean Whale Sanctuary of the International Whaling Commission (IWC) prohibits commercial whaling south of 40 degrees south (south of 60 degrees south between 50 degrees and 130 degrees west). Japan regularly does not recognize this provision, because the sanctuary violates IWC charter. Since the scope of the sanctuary is limited to commercial whaling, in regard to its whaling permit and whaling for scientific research, a Japanese fleet carried out an annual whale-hunt in the region. On 31 March 2014, the International Court of Justice ruled that Japan's whaling program, which Japan has long claimed is for scientific purposes, was a cloak for commercial whaling, and no further permits would be granted.
The "Convention for the Conservation of Antarctic Seals" is part of the "Antarctic Treaty System". It was signed at the conclusion of a multilateral conference in London on 11 February 1972.
The "Convention for the Conservation of Antarctic Marine Living Resources" is part of the "Antarctic Treaty System". It entered into force on 7 April 1982 with a goal to preserve marine life and environmental integrity in and near Antarctica. It was established largely due to concerns that an increase in krill catches in the Southern Ocean could seriously impact populations of other marine life which are dependent upon krill for food.
Many nations prohibit the exploration for and the exploitation of mineral resources south of the fluctuating Antarctic Convergence, which lies in the middle of the Antarctic Circumpolar Current and serves as the dividing line between the very cold polar surface waters to the south and the warmer waters to the north. The Antarctic Treaty covers the portion of the globe south of 60 degrees south; it prohibits new claims to Antarctica.
The "Convention for the Conservation of Antarctic Marine Living Resources" applies to the area south of 60° South latitude as well as the areas further north up to the limit of the Antarctic Convergence.
Economy.
Between 1 July 1998 and 30 June 1999, fisheries landed , of which 85% consisted of krill and 14% of Patagonian toothfish. International agreements came into force in late 1999 to reduce illegal, unreported, and unregulated fishing, which in the 1998–99 season landed five to six times more Patagonian toothfish than the regulated fishery.
Ports and harbors.
Major operational ports include: Rothera Station, Palmer Station, Villa Las Estrellas, Esperanza Base, Mawson Station, McMurdo Station, and offshore anchorages in Antarctica.
Few ports or harbors exist on the southern (Antarctic) coast of the Southern Ocean, since ice conditions limit use of most shores to short periods in midsummer; even then some require icebreaker escort for access. Most Antarctic ports are operated by government research stations and, except in an emergency, remain closed to commercial or private vessels; vessels in any port south of 60 degrees south are subject to inspection by Antarctic Treaty observers.
The Southern Ocean's southernmost port operates at McMurdo Station at . Winter Quarters Bay forms a small harbor, on the southern tip of Ross Island where a floating ice pier makes port operations possible in summer. Operation Deep Freeze personnel constructed the first ice pier at McMurdo in 1973.
Based on the original 1928 IHO delineation of the Southern Ocean (and the 1937 delineation if the Great Australian Bight is considered integral), Australian ports and harbors between Cape Leeuwin and Cape Otway on the Australian mainland and along the west coast of Tasmania would also be identified as ports and harbors existing in the Southern Ocean. These would include the larger ports and harbors of Albany, Thevenard, Port Lincoln, Whyalla, Port Augusta, Port Adelaide, Portland, Warrnambool, and Macquarie Harbour.
Even though organizers of several yacht races define their routes as involving the Southern Ocean, the actual routes don't enter the actual geographical boundaries of the Southern Ocean. The routes involve instead South Atlantic, South Pacific and Indian Ocean.
Notes.
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References.
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Murray Mouth
Murray Mouth is the point at which the River Murray meets the Southern Ocean. The Murray Mouth's location is changeable. Historical records show that the channel out to sea moves along the sand dunes over time. At times of greater river flow and rough seas, the two bodies of water would erode the sand dunes to create a new channel leaving the old one to silt and disappear.
Description.
The mouth of the Murray River is about south east of Goolwa and about south-south-east of the Adelaide city centre in the gazetted localities of Coorong and Goolwa South. The mouth is an opening in the coastal dune system which separates the river system from the ocean and which extends from near Goolwa in a south-easterly direction along the continental coastline for about . The mouth divides the dune system into two peninsulas. The peninsula on the west side is Sir Richard Peninsula which terminates at the mouth with a point named Pullen Spit. The peninsula on the east side is Younghusband Peninsula which terminates at the mouth with a point known in some sources as Sleepy Hollow.
Water flows throughout the mouth from two directions. Firstly, the flow from the west passes along a passage known as the Goolwa Channel which is bounded by Hindmarsh Island to its north side. Secondly, the flow from the east passes along a passage known as the Coorong Channel. The Coorong Channel itself is fed by the Mundoo Channel which passes between Hindmarsh Island and Mundoo Island to the north, and by the Tauwitchere Channel to the east.
Natural history.
From the Pleistocene about 2.5 million years ago, the Murray River terminated in a freshwater lake called Lake Bungunnia which included the area now occupied by the South Australia/New South Wales border. The lake drained less than a million years ago, creating the current course. It was suggested that the Murray may have taken a different course to the ocean, via Burra, South Australia and emptied into the Spencer Gulf, before being 'defeated' by the rise of the Mt Lofty Ranges. This has been studied by analysing the uplift date of the Mt Lofty Ranges and other geological data and found that this was not likely to be the case.
History.
European discovery and use.
During expeditions in 1829–30, Charles Sturt explored the Murray and its westward-flowing tributaries, finding that the mouth of the Murray was barely navigable to shipping. During the later 19th century with the discovery of gold, and the development of sheep and wheat farming along the Murray and its tributaries, the river became a major thoroughfare for the carriage of goods and produce. During the peak period of Murray River commerce (roughly 1855 to 1920) and before the development of rail and road transport, the Murray Mouth with its complex and unpredictable interaction between shallow, shifting and variable currents and the open sea, presented a major impediment to traffic between Adelaide and the Murray settlements, and many vessels foundered or were wrecked there.
Water flow.
River Murray water is used by farmers for irrigation in four of Australia's states, as well as supplying water to most towns along the river, and many further away through various pipelines. It has been widely accepted that too much water is being extracted; however business and political concerns make it difficult to remedy the problem. A visible symptom of the over-extraction of river water is the closing of the Murray Mouth.
From October 2002 until 2010 dredging machines operated at the Murray Mouth.
Between 2002 and 2006, two machines operated moving sand from the channel to maintain a minimal flow from the sea and into the Coorong's lagoon system. Without the 24-hour dredging, the mouth was at risk of becoming silted and closing, cutting the supply of fresh seawater into the Coorong, which would then warm up, stagnate and die.
In mid-2006 the dredging was scaled back as a result of the improved conditions at the mouth. Now only one dredging machine operates, and permission was granted to one commercial operator to navigate the channel between Goolwa and the Coorong, passing the mouth. This operation finished in 2010.
Dredging was scheduled to resume in January 2015.
Dredging continues at a cost between $3m to $6m annually.
Protected area status and other arrangements.
Australian government.
The Murray Mouth is immediately adjoined on its northern and eastern sides by the boundary of the Coorong and Lakes Alexandrina and Albert Wetland Ramsar site.
South Australian government.
The Murray Mouth is located within a special purpose area within the Encounter Marine Park and is immediately adjoined on its northern and eastern sides by the boundary of the Coorong National Park.
Non-statutory arrangements.
The Murray Mouth is adjoined on its northern and eastern sides by the boundary of the Coorong Important Bird Area which is an area considered by Birdlife International to be a place of ‘international significance for the conservation of birds and other biodiversity.’
Citations and references.
Notes.
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Murray River
Longest river in Australia
The Murray River (in South Australia: River Murray) (Ngarrindjeri: "Millewa", Yorta Yorta: "Dhungala" ("Tongala")) is a river in Southeastern Australia. It is Australia's longest river at extent. Its tributaries include five of the next six longest rivers of Australia (the Murrumbidgee, Darling, Lachlan, Warrego and Paroo Rivers). Together with that of the Murray, the catchments of these rivers form the Murray–Darling basin, which covers about one-seventh the area of Australia. It is widely considered Australia's most important irrigated region.
The Murray rises in the Australian Alps, draining the western side of Australia's highest mountains, then meanders northwest across Australia's inland plains, forming the border between the states of New South Wales and Victoria as it flows into South Australia. From an east–west direction it turns south at Morgan for its final , reaching the eastern edge of Lake Alexandrina, which fluctuates in salinity. The water then flows through several channels around Hindmarsh Island and Mundoo Island. There it is joined by lagoon water from The Coorong to the south-east before emptying into Encounter Bay (a bay of the Southern Ocean) through the Murray Mouth, east of Goolwa South. Despite discharging considerable volumes of water at times, particularly before the advent of large-scale river regulation, the waters at the Murray Mouth are almost invariably slow and shallow.
As of 2010[ [update]], the Murray River system received 58 per cent of its natural flow; the figure varies considerably.
The border between Victoria and New South Wales (NSW) lies along the top of the southern or left bank of
the Murray River.
Geography.
The Murray forms part of the long combined Murray–Darling river system that drains most of the inland of Victoria, New South Wales and the southern part of Queensland. The Murray carries only a small fraction of the water of comparably sized rivers in other parts of the world, and with great annual variability of its flow. It has dried up completely during extreme droughts on three occasions since official record-keeping began. More often, a sandbar formed at the mouth and stopped the flow.
The Murray is the border between New South Wales and Victoria – specifically at the top of the left bank (i.e. the Victorian side of the river). In a 1980 judgement, the High Court of Australia ruled on the question as to which state had jurisdiction in the unlawful death of a man who was fishing by the river's edge on the Victorian side of the river. This boundary definition can be ambiguous, since the river changes its course over time, and some of the river banks have been modified.
For west of the line of longitude 141°E, the border is between Victoria and South Australia, in the middle of the river. The discrepancy was caused during the 1840s, when the border was originally surveyed, by an east–west miscalculation of 3.72 kilometres (2.31 miles), and led to a long-running boundary dispute. West of this sector, the Murray is entirely within the state of South Australia.
Major settlements.
Major settlements along the course of the river, from its source to the Southern Ocean, and their populations from the 2016 Australian census are as follows.
River life.
The Murray and its tributaries support a variety of river life adapted to its vagaries. This includes native fish such as the famous Murray cod, trout cod, golden perch, Macquarie perch, silver perch, eel-tailed catfish, Australian smelt and western carp gudgeon, as well as other aquatic species such as the Murray short-necked turtle, broad-clawed yabbies and the large-clawed "Macrobrachium" shrimp, in addition to aquatic species more widely distributed through Southeastern Australia such as common long-necked turtles, common yabbies, the small claw-less "paratya" shrimp, water rats and platypus. The Murray crayfish, an endangered species, was able to increase its numbers thanks to scientists. The Murray also supports fringeing corridors and forests of the river red gum.
The health of the Murray has declined significantly since European settlement, particularly through regulation of its flows. Extreme droughts between 2000 and 2007 put significant stress on river red gum forests, leading to mounting concern over their long-term survival. The Murray has also flooded on occasion. The most significant was the flood of 1956: lasting for up to six months, it inundated many towns on its lower reaches in South Australia.
Ancient history.
Lake Bungunnia.
Between 2.5 and 0.5 million years ago, the Murray terminated in a vast freshwater lake – Lake Bungunnia – formed by earth movements that blocked the river near Swan Reach. At its maximum extent, Lake Bungunnia covered , extending to near the Menindee Lakes in the north and to near Boundary Bend in the south. The draining of Lake Bungunnia occurred approximately 600,000 years ago.
Deep clays deposited by the lake are evident in cliffs around Chowilla in South Australia. Considerably higher rainfall would have been required to keep such a lake full; the draining of Lake Bungunnia appears to have marked the end of a wet phase in the history of the Murray–Darling Basin and the onset of widespread arid conditions similar to today. A species of "Neoceratodus" lungfish existed in Lake Bungunnia; today "Neoceratodus" lungfish are only found in several Queensland rivers.
Cadell Fault and formation of the Barmah red gum forests.
The noted Barmah River red gum forests owe their existence to the Cadell Fault. About 25,000 years ago, displacement occurred along this fault, raising its eastern edge, which runs north–south, above the floodplain. This created a complex series of events. A section of the original Murray River channel immediately behind the fault was rendered abandoned (it exists today as an empty channel known as Green Gully). The Goulburn River was dammed by the southern end of the fault to create a natural lake.
The Murray River flowed to the north around the Cadell Fault, creating the channel of the Edward River which exists today and through which much of the Murray's waters still flow. Then the natural dam on the Goulburn River failed, the lake drained, and the Murray changed its course to the south and started to flow through the smaller Goulburn River channel, creating "The Barmah Choke" and "The Narrows" (where the river channel is unusually narrow), before entering into the proper Murray River channel again.
The primary result of the Cadell Fault – that the west-flowing water of the Murray River strikes the north–south fault and diverts both north and south around the fault in the two main channels (Edward and ancestral Goulburn) in addition to a fan of small streams, and regularly floods a large amount of low-lying country in the area. These conditions are perfect for River Red Gums, which rapidly formed forests in the area. Thus the displacement of the Cadell Fault 25,000 BP led directly to the formation of the famous Barmah River Red Gum Forests.
The Barmah Choke and The Narrows restrict the amount of water that can travel down this part of the Murray. In times of flood and high irrigation flows the majority of the water, in addition to flooding the Red Gum forests, actually travels through the Edward River channel. The Murray has not had enough flow power to naturally enlarge The Barmah Choke and The Narrows to increase the amount of water they can carry.
The Cadell Fault is quite noticeable as a continuous, low, earthen embankment as one drives into Barmah from the west, although to the untrained eye it may appear man-made.
Murray mouth.
The Murray Mouth is the point at which the Murray River empties into the sea, and the interaction between its shallow, shifting and variable currents and the open sea can be complex and unpredictable. During the peak period of Murray River commerce (roughly 1855 to 1920), it presented a major impediment to the passage of goods and produce between Adelaide and the Murray settlements, and many vessels foundered or were wrecked there.
Since the early 2000s, dredging machines have operated at the Murray Mouth for 24 hours a day, moving sand from the channel to maintain a minimal flow from the sea and into the Coorong's lagoon system. Without the dredging, the mouth would silt up and close, cutting the supply of fresh sea-water into the Coorong National Park, which would then warm up, stagnate and die.
Mythology.
Being one of the major river systems on one of the driest continents on Earth, the Murray has significant cultural relevance to Aboriginal Australians. According to the people of Lake Alexandrina, the Murray was created by the tracks of the Great Ancestor, Ngurunderi, as he pursued Pondi, the Murray Cod. The chase originated in the interior of New South Wales. Ngurunderi pursued the fish (who, like many totem animals in Aboriginal myths, is often portrayed as a man) on rafts (or "lala") made from red gums and continually launched spears at his target. But Pondi was a wily prey and carved a weaving path, carving out the river's various tributaries. Ngurunderi was forced to beach his rafts, and often create new ones as he changed from reach to reach of the river.
At Kobathatang, Ngurunderi finally got lucky and struck Pondi in the tail with a spear. However, the shock to the fish was so great it launched him forward in a straight line to a place called Peindjalang, near Tailem Bend. Eager to rectify his failure to catch his prey, the hunter and his two wives (sometimes the escaped sibling wives of Waku and Kanu) hurried on, and took positions high on the cliff on which Tailem Bend now stands. They sprung an ambush on Pondi only to fail again. Ngurunderi set off in pursuit again but lost his prey as Pondi dived into Lake Alexandrina. Ngurunderi and the women settled on the shore, only to suffer bad luck with fishing, being plagued by a water fiend known as Muldjewangk. They later moved to a more suitable spot at the site of present-day Ashville. The twin summits of Mount Misery are said to be the remnants of his rafts; they are known as "Lalangengall" or "the two watercraft".
This story of a hunter pursuing a Murray cod that carved out the Murray persists in numerous forms in various language groups that inhabit the enormous area spanned by the Murray system. The Wotojobaluk people of Victoria tell of Totyerguil from the area now known as Swan Hill, who ran out of spears while chasing Otchtout the cod.
History.
Roonka Flat, near Blanchetown, was a site of occupation since at least 7000BC.
European exploration.
The first Europeans to encounter the river were Hamilton Hume and William Hovell, who crossed the river where Albury now stands in 1824: Hume named it the "Hume River" after his father. In 1830, Captain Charles Sturt reached the river after travelling down its tributary the Murrumbidgee River and named it the "Murray River" in honour of the then British Secretary of State for War and the Colonies, Sir George Murray, not realising it was the same river that Hume and Hovell had encountered further upstream.
Sturt continued down the remaining length of the Murray to finally reach Lake Alexandrina and the river's mouth. The vicinity of the Murray Mouth was explored more thoroughly by Captain Collet Barker in 1831.
The first three settlers on the Murray River are known to have been James Collins Hawker (explorer and surveyor) along with Edward John Eyre (explorer and later Governor of Jamaica) plus E.B. Scott (onetime superintendent of Yatala Labour Prison). Hawker is known to have sold his share in the Bungaree Station, which he founded with his brothers, and relocated alongside the Murray at a site near Moorundie.
In 1852, Francis Cadell, in preparation for the launch of his steamer service, explored the river in a canvas boat, travelling downstream from Swan Hill.
In 1858, while acting as Minister of Land and Works for New South Wales, Irish nationalist and founder of Young Ireland, Charles Gavan Duffy, founded Carlyle Township on the Murray River, after his close friend, Scottish historian and essayist Thomas Carlyle. Included in the township were "Jane Street", named in honour of Carlyle's wife Jane Carlyle and "Stuart-Mill Street" in honour of political philosopher John Stuart Mill
In 1858, the Government Zoologist, William Blandowski, together with Gerard Krefft, explored the lower reaches of the Murray and Darling rivers, compiling a list of birds and mammals.
George "Chinese" Morrison, then aged 18, navigated the river by canoe from Wodonga to its mouth, in 65 days, completing the 1,555-mile (2,503 km) journey in January 1881.
River transport.
Shipping cannot enter the Murray from the sea because it does not have an estuary. However, in the 19th century the river supported a substantial commercial trade using shallow-draft paddle steamers, the first trips being made by two boats from South Australia on the spring flood of 1853. The "Lady Augusta", captained by Francis Cadell, reached Swan Hill while another, "Mary Ann", captained by William Randell, reached Moama (near Echuca). In 1855 a steamer carrying gold-mining supplies reached Albury but Echuca was the usual turn-around point, though small boats continued to link with up-river ports such as Tocumwal, Wahgunyah and Albury.
The arrival of steamboat transport was welcomed by pastoralists who had been suffering from a shortage of transport due to the demands of the gold fields. By 1860 a dozen steamers were operating in the high water season along the Murray and its tributaries. Once the railway reached Echuca in 1864, the bulk of the woolclip from the Riverina was transported via river to Echuca and then south to Melbourne.
The steam paddleship "Etona" was launched as a mission steamer, replacing an earlier steam launch, also named "Etona", which had been operating on the Murray since 1891. The vessel was based at Murray Bridge, and operated between Goolwa and the Victorian border, stopping at towns such as Mannum, Morgan and Renmark as well as isolated settlements and workcamps. The forepart of the vessel was used a chapel fitted with an altar and organ, with a capacity of 20 people. There was also a cabin. The minister on board, Rev. William Bussell, doubled as captain. On 16 August 1898, "Etona" arrived at Renmark, where the Bishop of Adelaide, Rev. Dr. John Harmer, held services the following Sunday with the assistance of Rev H M Wylie. In September of the same year, the service due in Holder on the 18th was suspended due to the vessel grounding on a sandbank. During its year of launch, the boiler of "Etona" gave way, being replaced at a cost of £87.
The Murray was plagued by "snags", fallen trees submerged in the water, and considerable efforts were made to clear the river of these threats to shipping by using barges equipped with steam-driven winches. In recent times, efforts have been made to restore many of these snags by placing dead gum trees back into the river. The primary purpose of this is to provide habitat for fish species whose breeding grounds and shelter were eradicated by the removal of the snags.
Author E.J. Brady chronicled an eventful journey downriver in a small motor boat from Albury to the coast in 1911 in "River Rovers."
The volume and value of river trade made Echuca Victoria's second port and in the decade from 1874 it underwent considerable expansion. By this time up to thirty steamers and a similar number of barges were working the river in season. River transport began to decline once the railways touched the Murray