Deep-sea canyon discovered off WA

By Melissa Leong 10 May 2010
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An exciting new deep-sea discovery explains a mysterious surface anomaly.

A NEW DEEP-SEA canyon found near WA’s Montebello Islands may explain a mysterious anomaly in the temperature of surface waters.

The deep rift in the sea floor was accidentally discovered last month by a group of oceanography students with the Australian National Network in Marine Science. From three Australian universities, the students were on a training voyage aboard the government research vessel the RV Southern Surveyor.

“[It’s] astonishing that we can go off Western Australia and find something new every time, because our oceans are so unexplored,” says Professor Anya Waite, oceanographer and expedition leader, based at the University of WA.

Oceanic surprise

The Montebello Islands are situated 130 km off the Pilbara coast of northern WA. Submarine canyons are deep, steep-sided underwater valleys carved by erosion; they aid the transportation of land sediment into deep sea and boost ocean productivity through upwelling of cold water.

“The students found a deep cleft in the continental shelf,” says Anya. “Their measurements also suggested that the canyon might be associated with ‘upwelling’ to the continental shelf, a physical process known to make the surface ocean more productive.”

This new canyon in 900 m down and is about 40km in length. It could be a contributor to the diverse marine life in the area, she says, which includes over 150 species of coral, rare turtles, seabirds and ten species of whales.

“Submarine canyons modify currents and can cause upwelling on nutrient rich waters into the shallow [zone permeated by sunlight],” agrees Dr. Gary Kendrick, a marine ecologist also with the University of Western Australia. “That may lead to increased production of phytoplankton, zooplankton and increased fish productivity,” he says.

Unknown network of canyons

Anya’s team is now working with satellite imagery to map both current and temperature changes in the ocean surface of the region. There may be a previously undiscovered network of canyons, she says. “It is important to understand submarine canyon…because they can alter local currents and affect infrastructure like oil rigs and ships.”

The new canyon was named the Tryal Canyon after the British East India Company’s Tryal, one of the first European ships to be wrecked in Australia, which was lost near one of the Montebello Islands in 1622.

To date, Australia’s largest submarine canyon is the Perth Canyon which plunges down to 4000 m below sea level at its lowest point and is 15 km across. This makes it roughly equivalent to the USA’s Grand Canyon in size. It’s found about 40 km west of Fremantle in WA.