It has been called the oceanic equivalent of the Butterfly Effect.
So chaotic are the currents in the southern Indian Ocean that two identical objects, dropped into the water just metres apart, can end up floating hundreds of kilometres away from each other in a matter of days.
It’s a phenomenon Dr Erik van Sebille, an oceanographer at the University of NSW, knows all too well.
His research this past summer involved dropping buoys with global-positioning systems into a patch of the southern Indian Ocean just east of where the hunt for missing Malaysia Airlines Flight 370 is now centred.
The rate at which those buoys drifted apart, after starting from virtually the same location, was extraordinary. Three months on, and Dr van Sebille said they were now more than 1000 kilometres apart.
He estimated that a piece of debris in this part of the ocean could drift 100 kilometres in a day.
‘‘The idea of the Butterfly Effect is that, if a butterfly flaps its wings, then something really big happens somewhere else. This is kind of the oceanic equivalent of that,’’ Dr van Sebille said, underlining the difficulties surrounding the search for MH370.
‘‘Two pieces of debris that landed in the ocean 10 centimetres apart might now be hundreds of kilometres apart already.’’
An interactive model of the Indian Ocean currents is available at adrift.org.au. To see the currents, click the cursor on a spot in the Indian Ocean.
France has become the latest nation to identify new satellite images which show "potential objects" in the Indian Ocean, after Australia and China had already released images that show possible debris from the Boeing 777.
All of the sightings are in an area south-west of Perth. The debris in the earlier Australian image was about 2500 kilometres south-west of Perth, and the Chinese sighting, captured two days later, was about 120 kilometres "south by west" of that. The French sighting is believed to be about 850 kilometres north of the current search area.
Dr van Sebille said that any potential sighting of debris in the southern Indian Ocean was significant because it was one of the most pristine environments, largely devoid of plastic and debris.
He said there was a known ‘‘garbage patch’’ in the Indian Ocean where debris tended to gather, similar to one also located in the Pacific Ocean. However the Indian Ocean patch was further north of the current search area, at about the latitude of Perth.
Over an extended period, debris in the Indian Ocean generally tended to move slowly north and east, he said.
‘‘That’s an advantage here [in the search for MH370] because it means that it is quite unlikely for debris that came from land, for instance from Australia, South Africa or from South America, to move southward towards Antarctica. The general tendency of it is to go northward,’’ he said.
‘‘Also, because there is hardly any shipping here, there’s not much debris.’’
Dr van Sebille said the Southern Ocean was really ‘‘quite a special place’’ because it was possible to keep moving east without hitting land.
‘‘There is an opening between South America and Antarctica, the great passage, it just flows on and on and on, so it’s this giant current that’s actually the biggest current in the world,’’ he said.
‘‘It’s swept by the winds and as it becomes strong it starts to break up in all kinds of vortices.
‘‘It’s just like if you walk here in the CBD and there’s a strong wind, and then behind the big buildings you start seeing vortices. The same happens in the Southern Ocean. It’s full of these vortices, we call them eddies. Their physics is essentially the same as hurricanes, they’re kind of the ocean equivalent of hurricanes. They move around, they’re ubiquitous, and they pose a real problem in this case because they make the flow highly unpredictable.’’
Dr van Sebille said the unpredictability of ocean eddies was demonstrated in 1992, when a shipping container holding nearly 29,000 plastic bath toys, including rubber ducks, spilled from a cargo ship during a storm in the north Pacific Ocean.
Oceanographers began tracking the movements of the toys, which included red beavers, green frogs, blue turtles and yellow ducks.
Ten months after the incident, the first toys began to wash up along the Alaskan coast, and in the years since then they have been found washed up on the shores of Hawaii, America, South America, and Australia, while others have been found frozen in Arctic ice.