Hydrology
Major Coral Sea currents form a counter-clockwise gyro which includes the East Australian Current. It brings warm nutrient-poor waters from the Coral Sea down the east coast of Australia to the cool waters of the Tasman Sea. This current is the strongest along the Australian coasts and transforms 30 million m3/s of water within a flow band of about 100 kilometres wide and 500 metres deep. The current is strongest around February and weakest around August.
The major river flowing into the sea is the Burdekin River, which has its delta southeast of Townsville. Owing to the seasonal and annual variations in occurrence of cyclones and in precipitation (typically between 200 and 1600 mm/year), its annual discharge can vary more than 10 times between the two succeeding years. In particular, in the period 1920–1999, the average flow rate near the delta was below 1000 m3/s in 1923, 1931, 1939, 1969, 1982, 1985, 1987, 1993 and 1995; it was above 25,000 m3/s in 1927, 1940, 1946, 1950, 1951, 1959, 1968, 1972, 1974 and 1991, and reached about 40,000 m3/s in 1946. This irregularity results in concomitant fluctuations of the sea water composition near the river delta.
The surface water temperature varies on the south of the sea from 19 °C in August to 24 °C in February. It is rather warm and stable at 27–28 °С in the north all through the year. Water salinity is 34.5–35.5‰ (parts per thousand). The water is mostly very clear, with the visibility of about 30 metres (100 ft) near the reefs.
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