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Definition: Tasman Sea from The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide

Part of the Pacific Ocean between southeast Australia and northwest New Zealand. It is named after the Dutch explorer Abel Tasman.


Summary Article: Tasman Sea
from Earth's Landscape: An Encyclopedia of the World's Geographic Features
Pacific Ocean
Geographic Overview.

The Tasman Sea lies between Australia and New Zealand at the southwestern edge of the Pacific Ocean. Locally referred to as “The Ditch,” it is influenced in the north by tropical waters flowing in from the Coral Sea and in the south the subpolar waters of the Southern Ocean. Currently, the Tasman Sea is warming at a rate three times greater than the world ocean average. The sea is named for the Dutch explorer Abel Tasman, who discovered the sea in 1642. Sydney, Australia, is the largest city on the Tasman Sea.

Geographic Coordinates.

Approximately 32°S–45°S, 150°E–175°E

Description.

The Tasman Sea is a marginal sea in the southwestern part of the Pacific Ocean. Covering an area of 890,000 mi2 (2,300,000 km2), it extends south from the tropical Coral Sea some 1,700 mi (2,800 km) to the Antarctic Circumpolar Current at the northern edge of the Southern Ocean. Warm waters from the Coral Sea flow into the Tasman Sea and produce a subtropical climate in the north. Norfolk Island, at the boundary between the Coral and Tasman seas, is encircled by the planet's southernmost coral reef. Cold water enters the sea through the windy Bass Strait between Australia and Tasmania and produces a temperate climate over the southern Tasman Sea. The subantarctic water is cooler and saltier and sinks to depths of 1,300–2,260 ft (400–800 m) in what is known as the Bass Strait Cascade. This water can remain undiluted in eddies for months. In 2011, one such eddy was 650 ft (200 m) thick and 25 mi (40 km) in diameter.

The western portion of the seafloor is an abyssal plain reaching depths of 19,500 ft (5,945 m) bsl. To its east is a broad submarine plateau almost 1,240 mi (2,000 km) long, the Lord Howe Rise. The rise, some 250–370 mi (400–600 km) wide, extends northward into the Coral Sea and ends in the south at the Challenger Plateau, another large submerged piece of continental crust just west of New Zealand. Both Lord Howe Rise and Challenger Plateau are fragments of the Australian continent called Zealandia that broke away during the breakup of Gondwana (see later discussion). The Lord Howe Rise is about 3,330 ft (1,000 m) bsl. Lord Howe Island and Ball's Pyramid on the western edge of the rise are extinct, eroded shield volcanoes and the youngest members of the Lord Howe seamount chain, which continues along the northern section of the underwater plateau as a series of coral-capped guyots.

Geologic History.

The Tasman Sea opened 85–52 mya when rifting of Gondwana detached a large piece of continental crust from eastern Australia and created a now largely submerged microcontinent now called Zealandia. The northern seamount chain probably resulted from the passage of Zealandia over the Lord Howe hotspot.

Circulation and Major Currents.

The generally counterclockwise circulation in the Tasman Sea is marked by the inflow of warm water from the South Equatorial Current, which enters the Coral Sea and then exits it as the southward-moving warm East Australian Current. This, the western boundary current, turns east off Tasmania and then north-northeast off the west coast of New Zealand. Between New Zealand and Norfolk Island, warm waters return to the Pacific Ocean. Cold subpolar water enters the loose gyre through Bass Strait and as a cold, northward-flowing coastal current along South Island, New Zealand.

Biota.

The cold waters of the southern Tasman Sea support marine mammals and seabirds. Doubtful Sound, a large fjord in southwestern New Zealand, is home to whales and dolphins, the New Zealand fur seal, and the threatened Fiordland Crested Penguin (Eudyptes pachyrhynchus). In the shallow waters of the sound are also black corals, more commonly found in deep-sea environments.

Protected Areas.

Elizabeth and Middleton Reefs Marine National Nature Reserve (Australia) in the northern Tasman Sea protect two isolated coral platform reefs on the Lord Howe Rise as well as the rare and endangered Black Cod (Epinephelus daemelli).

Environmental Issues.

Rapid warming of the Tasman Sea has resulted in more than a 3.6°F (2°C) increase in sea surface temperatures in the past 60 years, three times the average warming of Earth's oceans. The rise appears to be related to strengthening wind systems pushing the East Australian Current farther to the south. On land, exotic mammals such as cats and rats are a threat to breeding Fiordland Crested Penguins.

See also New Zealand

Further Reading
  • CSIRO Australia. 2012. “Warming in the Tasman Sea, Near Australia, a Global Warming Hot Spot.” ScienceDaily. http://www.sciencedaily.com/releases/2012/01/120130102538.htm.
  • Copyright © 2015 Joyce A. Quinn and Susan L. Woodward

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