A new look at the Leeuwin Current

New research has revealed further insights into the formation of the globally unusual poleward-flowing Leeuwin Current and the role it plays in sustaining the marine ecosystems of the Ningaloo Reef.

In a recently published study researchers from The University of Western Australia and the Australian Institute of Marine Science investigated three-dimensional ocean circulation on the continental shelf as part of WAMSI’s Ningaloo Research Program.

The team made a variety of detailed field measurements that extended along a large portion of the Ningaloo coast (~70 km), enabling a whole-of-reef scale synoptic view of variability over several spring and summer months.

“This was the first time anyone had attempted field oceanographic observations on such a broad scale at Ningaloo,” team member UWA Professor Greg Ivey said. “It was exciting to be able to use the data to start looking into how seasonal transitions affect local ocean dynamics, upwelling and downwelling and how this could then be affecting oceanographic features of statewide importance, such as the Leeuwin Current.”

Detailed analysis of the comprehensive dataset has now shown that variability in the currents offshore from Ningaloo were important in controlling the variability in the strength of Leeuwin Current as it progresses down the southern WA coast. It was also found to be important in the localised transport of nutrient rich water from deep below the ocean surface to Ningaloo Reef, a vital process that supports the coral reefs and fisheries of the region. 

“The interesting thing is that the Leeuwin Current is very weak on the North West Shelf, just north of Ningaloo,” Professor Ivey said, “yet to the south, it is the dominant current feature of southwestern Australia.”

“Our results confirm that the Ningaloo Peninsula and Shelf region can be considered one of the important formation regions for the Leeuwin Current, and therefore understanding the dynamics of the current at Ningaloo increases not only our local knowledge but also the variability of the Leeuwin current and hence the ecosystems that it supports further south,” AIMS Co-author Dr Richard Brinkman said.

The study: Observations of the shelf circulation dynamics along Ningaloo Reef, Western Australia during the austral spring and summer, published in the international peer-reviewed journal Continental Shelf Research, was also supported by the Australian Research Council.