How ocean arteries carry life across the Indian Ocean

June 30, 2011, Science in Public
How ocean arteries carry life across the Indian Ocean
Ocean arteries at mid-depth (250 - 1000 m) in the southeast Indian Ocean. Credit: Prasanth Divakaran

Research at the University of Melbourne and the Bureau of Meteorology has overturned conventional ideas of ocean circulation.

Rather than moving simply in large clockwise () and anti-clockwise () gyres, the of the southeast Indian are flowing east-west in bands, Prasanth Divakaran, a PhD candidate in the University’s School of Earth Sciences, and his colleagues have shown.

The findings have important implications for our understanding of all sorts of ocean events from the movements of fish and marine life to the prediction of weather and climate.

“For instance,” he says, “We found that ocean eddies—the marine analogues of atmospheric weather systems like tropical cyclones—form off Australia and begin a three-year journey across the Indian Ocean along what we call ‘ocean arteries’, transporting sea-water and biology with them.”

Prasanth’s work is being released for the first time in public through Fresh Science, a communication boot camp for early career scientists held at the Melbourne Museum. He was one of 16 winners from across Australia.

Prasanth is also presenting his research at the XXV International Union of Geophysics and Geodesy General Assembly in Melbourne this week.

Single day snapshot of sea surface temperature from Bureau of Meteorology ocean forecasting system. Credit: Dr Justin Freeman

On the basis of initial studies of water movement, Prasanth analysed a model of the circulation of the southeast using advanced computing and new software for visualising the results. He and his colleagues then checked their findings against satellite observations.

“New international satellites and modern technologies developed in Australia helped to reveal the previously unknown patterns.”

The results are also in keeping with some of the latest research from overseas, he says.

The basin-wide ocean currents the researchers revealed are organised into alternating bands, which connect the north-south currents on the east and west side of the Ocean.

“They look  a bit like the patterns seen on the surface of Jupiter.”

Recent work on the lobster life cycle around Western Australia has shown that the probability of growing into an adult depends on which deep artery of ocean circulation the larvae are swept into.

“Nature has known about these ocean arteries for centuries, but we humans have only just discovered them.”

Understanding the impact of the arteries on ocean heat transport and climate is critical, Prasanth says.

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1 / 5 (2) Jul 08, 2011
Fascinating article, and great work for someone new to the field. I wonder if similar patterns exist in the Atlantic?

A curious observation here: Notice the color scaling on the graphic of ocean surface temperature? It looks like they could use a lot more color variation above 25 and below 20. It looks like more than half the image is maxed out on the red end, and another quarter is maxed out on the blue end.

On a side note, this reminds me of a piece I heard about shipping containers falling off of ships. Apparently something like 10,000 per year are lost at sea. The expert was wondering if the containers might form a bridge for sea floor creatures along shipping lanes. Animals like starfish or lobster tend to move from one bottom feature to another when they move, so he was suggesting that it might make it easier for those animals to cross long stretches of ocean bottom over time, maybe leading to species invasions.
1 / 5 (2) Jul 08, 2011
@GSwift7, interesting premise in your side note. I wish you had the URL, but alas - I know how hard it can be to hang on to links to random articles.

10,000 shipping containers per year certainly sounds like a lot, but compared to how much ocean bottom there is out there - even roughly confined to the sea floor beneath shipping lanes - I doubt it adds up to much coverage.

I realize that this is probably an unfair, somewhat "apples and oranges" comparison, but if I knew that "they" had randomly scattered 10,000 working water fountains throughout the Sahara, and then I had to suddenly parachute into some unknown location anywhere between central Mauritania and central Sudan, I'd still be very worried about my chances of getting out of the desert without dying of thirst.

Again, not quite a 1-to-1 situation, and I'm not denying the danger of species invasions, but I'd be more worried about the economic costs of the lost cargo (or of building that many water fountains).
1 / 5 (2) Jul 08, 2011
@GSwift7, interesting premise in your side note. I wish you had the URL, but alas - I know how hard it can be to hang on to links to random articles

It was a story on NPR radio, so I never had a link to it. That's also 10,000 per year for about 50 years so far. So, 500,000 maybe? They would also be concentrated around ports, where shipping tends to accumulate when there are storms because they cannot put in to port in a storm. So in busy shipping areas, like indonesia, where the shipping lanes are confined to narrow channels and ports are not spaced out too much, there could be a large concentration of shipping in a relatively small area.

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