Tasman Sea

The Tasman Sea is a marginal sea within the South Pacific Ocean. It sits between the landmasses of Australia and New Zealand.

To its north lies the Coral Sea. The Pacific Ocean borders it to the northeast and east. The Cook Strait is to its east, while the Southern Ocean lies to the south and southeast. To the west, the sea is bounded by the Bass Strait. This large body of water is an essential part of the ocean system in the southwestern Pacific.

Geologically, the sea has a complex history. A midocean ridge exists roughly midway between the continental margins of Australia and Zealandia. This ridge developed between 85 and 55 million years ago. It formed during the breakup of the supercontinent Gondwana. During this time, Australia and Zealandia began to move apart. Because much of Zealandia is submerged, the ridge runs closer to the Australian coast than to New Zealand. This underwater mountain range is a key feature of the sea's floor.

The seafloor itself is composed of various types of sediment known as ooze. Much of the base consists of globigerina ooze. In certain areas, different types of sediment appear. A small zone of pteropod ooze is found south of New Caledonia. Additionally, siliceous ooze can be found to the southern extent of 30°S. These fine sediments settle over vast periods of time. They help scientists understand the history of the ocean floor.

Ocean currents drive much of the activity in the Tasman Sea. The East Australian Current is the most energetic circulation feature in the region. It begins its southward flow in the tropics of the Coral Sea near the eastern coast of Australia. This current is a return of the westward-flowing Pacific South Equatorial Current. It acts as a primary means of heat transport from the tropics to the middle latitudes. As it moves south, it can split into different branches. One branch, called the Tasman Front, flows toward the north of New Zealand. The presence of the New Zealand land mass helps define how far south this branch can split.

Other currents also shape the local waters. The East Auckland Current moves down the west coast of the North Island. Further south, the East Cape Current flows toward the South Island. This happens because of the shapes of the Lord Howe Rise and the southern east coast of the North Island. South of Tasmania, the East Australian Current is diverted west into the Subtropical Front. Here, it collides with the western-moving Subantarctic front of the Antarctic Circumpolar Current. The current also sheds eddies, which are swirling masses of water. Some of these, known as Tasman Leakage, move as far west as the Indian Ocean.

Weather patterns also influence the sea. In the south, depressions move from west to east. The northern limit for these westerly winds is near 40°S. During the southern winter, which lasts from April to October, these winds change direction. The northern branch of the westerly winds moves toward the north and meets trade winds. This results in frequent winds from the southwest. In the Australian summer, from November to March, the southern branch of the trade winds meets west winds. This interaction produces significant wind activity across the area.

Human history in the Tasman Sea is long and varied. The Māori people call the sea Te Moana-a-Rehua, meaning "the sea of Rehua." This name differs from the name used for Pacific waters at Cape Reinga, which is Te Tai-o-Whitirea. European exploration included Abel Janszoon Tasman, who was the first known European to cross it in 1642. Later, Lieutenant James Cook navigated the sea extensively during the 1770s. In 1876, the first telegraph cable was laid to connect Australia and New Zealand. This was later replaced by the Commonwealth Pacific Cable in 1963, which was a telephone cable.

Adventure and science have also defined the region. In 1928, Moncrieff and Hood attempted a trans-Tasman flight but were never seen again. Later that year, Charles Kingsford Smith and Charles Ulm completed the first successful flight. Solo rowing crossings were also achieved by Colin Quincey in 1977 and his son Shaun Quincey in 2010. Biological research has revealed a rich ecosystem. The research ship RV Tangaroa discovered 500 species of fish and 1,300 species of invertebrates. Researchers even found a tooth from the extinct megalodon shark. The sea contains several midsea island groups, including Lord Howe Island and Ball's Pyramid.