The Leeuwin Current is a warm

ocean current An ocean current is a continuous, directed movement of seawater generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours, sh ...

which flows southwards near the western coast of

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. It rounds

Cape Leeuwin Cape Leeuwin is the most south-westerly (but not most southerly) mainland point of the Australian continent, in the state of Western Australia. Description A few small islands and rocks, the St Alouarn Islands, extend further in Flinders ...

to enter the waters south of Australia where its influence extends as far as

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

Discovery

The existence of the current was first suggested by William Saville-Kent in 1897. Saville-Kent noted the presence of warm tropical water offshore in the Houtman Abrolhos, making the water there in winter much warmer than inshore at the adjacent coast. The existence of the current was confirmed over the years, but not characterised and named until Cresswell and Golding did so in the 1980s.

Track

The West Australian Current and Southern Australian Countercurrent, which are produced by the West Wind Drift on the southern Indian Ocean and at Tasmania, respectively, flow in the opposite direction, producing one of the most interesting oceanic current systems in the world. The ‘core’ of the Leeuwin Current can generally be detected as a peak in the surface temperature with a strong temperature decrease further offshore. The surface temperature difference across the Current is about 1 °C at North West Cape, 2° to 3° at Fremantle and can be over 4° off Albany in the

Great Australian Bight The Great Australian Bight is a large oceanic bight (geography), bight, or open bay, off the central and western portions of the southern Coast, coastline of mainland Australia. There are two definitions for its extent—one by the Internation ...

. The current frequently breaks out to sea, forming both clockwise and anti-clockwise eddies.

Physical properties

Its strength varies through the year; it is weakest during the summer months (winter in the northern hemisphere) from November to March when the winds tend to blow strongly from the south west northwards. The greatest flow is in the autumn and winter (March to November) when the opposing winds are weakest.

Evaporation Evaporation is a type of vaporization that occurs on the Interface (chemistry), surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evapora ...

from the Leeuwin current during this period contributes greatly to the rainfall in the southwest region of

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

. Typically the Leeuwin Current's speed and its eddies are about 1

knot A knot is an intentional complication in Rope, cordage which may be practical or decorative, or both. Practical knots are classified by function, including List of hitch knots, hitches, List of bend knots, bends, List of loop knots, loop knots, ...

(50 cm/s), although speeds of 2 knots (1 m/s) are common, and the highest speed ever recorded by a drifting satellite-tracked buoy was . The Leeuwin Current is shallow for a major current system, by global standards, being about 300 m deep, and lies on top of a northwards countercurrent called the Leeuwin Undercurrent. Because of the Leeuwin Current, the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

waters of Western Australia are warmer in winter and cooler in summer than the corresponding regions off the other continents. The Leeuwin Current is also responsible for the presence of the most southerly true corals at the Abrolhos Islands and the transport of tropical marine species down the west coast and across into the Great Australian Bight. The Leeuwin Current is influenced by

El Niño EL, El or el may refer to: Arts and entertainment Fictional entities * El, a character from the manga series ''Shugo Chara!'' by Peach-Pit * Eleven (''Stranger Things'') (El), a fictional character in the TV series ''Stranger Things'' * El, fami ...

conditions, characterised by slightly lower sea temperatures along the Western Australian coast and a weaker Leeuwin Current, with corresponding effects upon rainfall patterns.

Comparisons

The Leeuwin Current is very different from the cooler, equatorward flowing currents found along coasts at equivalent latitudes such as the southwest African Coast (the Benguela Current); the long Chile-Peru Coast (the Humboldt Current), where upwelling of cool nutrient-rich waters from below the surface results in some of the most productive fisheries; the California Current, which brings foggy conditions to San Francisco; or the cool Canary current of North Africa.

References

External links

*
CSIRO Marine Research

{{Ocean Coastline of Western Australia Currents of the Indian Ocean