The Gulf of Carpentaria is a large, shallow sea enclosed on three sides by northern Australia and bounded on the north by the eastern Arafura Sea. The northern boundary is generally defined as a line from Slade Point, Queensland in the northeast, to Cape Arnhem, Northern Territory in the west. At its mouth, the Gulf is 590 km wide, and further south, 675 km. The north-south length exceeds 700 km. It covers a water area of about 300,000 km². The general depth is between 55 and 66 metres and does not exceed 82 metres. The tidal range in the Gulf of Carpentaria is between two and three metres. The Gulf and adjacent Sahul Shelf were dry land at the peak of the last ice age 18,000 years ago when global sea level was around 120 m below its present position. At that time a large, shallow lake occupied the centre of what is now the Gulf. The Gulf hosts a submerged coral reef province that was only recognised in 2004.
The land bordering the Gulf is generally flat and low-lying. To the west is Arnhem Land, the Top End of the Northern Territory, and Groote Eylandt, the largest island in the Gulf. To the east is the Cape York Peninsula and Torres Strait which joins the Gulf to the Coral Sea. The area to the south is known as the Gulf Country. The Gulf Country supports the world's largest intact savanna woodlands as well as native grasslands, known as the Carpentaria tropical savanna. The woodlands also extend up the west and east coast of the Gulf. They are dominated by Eucalyptus and Melaleuca species from the family Myrtaceae. The climate is hot and humid with two seasons per year. The dry season lasts from about April until November and is characterized by very dry southeast to east winds, generated by migratory winter high pressure systems to the south. The wet season lasts from December to March. Most of the year's rainfall is compressed into these months, and during this period, many low-lying areas are flooded. The Gulf is prone to tropical cyclones during the period between November and April. The gulf experiences an average of three cyclones each year that are thought to transport sediments in a clockwise direction along the Gulf's coast. In many other parts of Australia, there are dramatic climatic transitions over fairly short distances. The Great Dividing Range, which parallels the entire east and south-east coast, is responsible for the typical pattern of a well-watered coastal strip, a fairly narrow band of mountains, and then a vast, inward-draining plain that receives little rainfall. In the Gulf Country, however, there are no mountains to restrict rainfall to the coastal band and the transition from the profuse tropical growth of the seaside areas to the arid scrubs of central Australia is gradual. In September and October the Morning Glory cloud appears in the Southern Gulf. The best vantage point to see this phenomenon is in the Burketown area shortly after dawn. It has been hypothesized that the Gulf experienced a major asteroid impact event in 536 A.D.
Coral reefs
The Gulf of Carpentaria is known to contain fringing reefs and isolated coral colonies, but no near-surface patch or barrier reefs exist in the Gulf at the present time. However, this has not always been the case. carried out by Geoscience Australia in 2003 and in 2005 aboard the RV Southern Surveyor revealed the presence of a submerged coral reef province covering at least 300 km in the southern Gulf. The patch reefs have their upper surfaces at a mean water depth of 28.6 ± 0.5 m, were undetected by satellites or aerial photographs, and were only recognised using multibeam swath sonar surveys supplemented with seabed sampling and video. Their existence points to an earlier, late Quaternary phase of framework reef growth under cooler-climate and lower sea level conditions than today.
Extensive areas of seagrass beds have allowed commercial shrimp operations in the Gulf. Zinc, lead and silver is mined from the McArthur River zinc mine and exported via the Gulf. Another zinc mine, Century Zinc is in the gulf on the Queensland side of the border. It exports its product through the port facility at Karumba. The cattle industry is also a very important part of the regional economy in the gulf. According to the then Chairman of the Gulf of Carpentaria's Commercial Fisherman's Organisation, Gary Ward, the number of sightings of Indonesian vessels fishing illegally in the gulf's waters increased in early 2005. By 2011 the numbers of illegal fishing boat interceptions had declined significantly with the cause attributed to enforcement efforts and education programs in Indonesia.
Major port plan
In 2012, a major new port located to the west of Karumba and rail connection to the North West Minerals Province was proposed by Carpentaria Rail. The advantages of a port at Karumba compared to Townsville was that it was three or four days closer to Asia via shipping routes. Additionally, expansion is taking place of the Bing Bong Port which services the McArthur River zinc mine, awarded the Northern Territory Earth award.
Physiography
The Gulf is one of the distinct physiographic sections of the larger Carpentaria Basin province, which in turn is part of the larger East Australian Basins physiographic division.
