The area 2,500 kilometres southwest of Perth, Australia, where satellites picked up images of two objects large enough to possibly be parts of a plane, is in a remote region that is on the boundary between the southern reaches of the Indian Ocean and the northern edge of the Southern Ocean, which encircles Antarctica and is also known as the Antarctic Ocean.
It is far from regular shipping routes and any land masses and is known for rough seas and strong winds.
It's fall in the region, which just adds to the headaches, says Capt. Chris Curl, who has taken the U.S. Navy-owned research vessel Melville through the southern Indian Ocean as part of scientific expeditions for the Scripps Institution of Oceanography at University of California, San Diego.
"It's notorious for being very, very rough, and it’s only going to get worse from this time on into the winter," he said by phone from San Diego. "It's just a very rough area to operate and cold and remote, so if anything does go wrong, help is a long way away."
Stormy seas complicate search
The area where the search for the potential debris is concentrated is in Australian waters in the 40º degree latitude region known as the "Roaring Forties" for its strong currents and stormy, windy weather, which is made worse by the absence of any nearby land mass.
"These low-pressure systems are basically unimpeded as they circle around the globe down at those latitudes," Curl said. "They just keep circling round and round the globe, and it creates mountainous seas and swells."
The satellite images, taken several days ago, were the first real clue in the confounding mystery of Flight MH370 that has gripped the world, and planes and ships of several nations were dispatched to the area to try and locate the objects. But even if the debris is found and confirmed to be from Flight MH370, the route back to where it came from will be long and no less confounding.
"It’s been  days that things have been drifting, so whatever is found now has moved a fair distance from where it originally struck, and that distance could be 500 to 1,000 kilometres," said Brad deYoung, professor of oceanography at Memorial University in St. John's on Thursday.
"But beyond that, the individual objects that fell would have moved apart, and so there could be pieces spread over a debris field now of tens or many tens of kilometres."
Search site could be huge
The predominant winds and ocean currents in this part of the Indian Ocean would generally move the debris in an easterly direction from the crash site. The speed at which the debris would move would depend on the strength of the winds and the speed of the various surface and subsurface currents active in that part of the ocean. Curl, assuming a speed of about two to three knots for 13 days, estimates that, as of Thursday, a good place to start looking for the crash site would be around 1,100 kilometres west of where the suspected debris was spotted.
But that kind of estimate would still leave searchers with a huge area to comb.
"The rough guess is you’d probably have an area of several hundred thousand or half a million square kilometres to search, assuming it's on the bottom [of the ocean] somewhere," said deYoung.
You can refine that guess by running mathematical models that wind back the clock and try to pinpoint where the debris was 13 days ago based on where it is now and using more precise information about currents, weather and ocean circulation.
"In general, the Southern Ocean, which would include the south Indian Ocean we're talking about, is the least-well studied and sampled of all the world’s oceans," said Stephanie Waterman, a physical oceanographer at the University of British Columbia.
"But that being said, especially in the last decade or so, with satellite information and autonomous instruments that we put in the ocean and that move around with the ocean currents, we do have quite a lot of coverage in that part of the world, so we have a pretty good understanding of the circulation there."
The more debris, the better
The more pieces of debris you find, the better the estimate of where the crash site might be, says deYoung, although different types of debris will have drifted differently, which complicates the calculation. Lighter objects like seat cushions which float on the surface will be more affected by winds and surface currents while heavier items that are partly submerged are more susceptible to deeper currents.
It's also important to find the debris quickly because the models get more imprecise with time.
"The circle of uncertainty grows the farther back we go," said deYoung. "If another week goes by, then the debris you find won't be very helpful. It's already a pretty long time to wind back."
Satellites do pass over this part of the Indian Ocean, but only periodically, so it's unlikely that one of them would have registered the moment Flight MH370 entered the ocean.
"The problem is satellites aren't there continuously," Waterman said. "They're only passing over a particular spot on the globe every once in while, so in order to make use of that information, you'd have to be extremely lucky that the satellite was at the right point when impact happened."
Binoculars the best tool for the job
For now, the search is being conducted from the air by planes equipped with surveillance equipment such as synthetic aperture radar that can scan the ocean surface for large objects and from the sea by a Norwegian merchant vessel that was diverted to the area while transporting cars from Cape Town to Melbourne, Australia. The Hoegh St. Petersburg was first asked to join the search on March 18, and it took the ship a day to reach the initial search area. It had been headed back to its regular route when it was sent to the new search zone on Thursday.
The crew on the 230-metre long vessel is relying mainly on binoculars to conduct the search, which Erik Gierchsky of the Norwegian Shipowners Association said is "the best equipment for this operation."
"It’s a big boat, and they have good views and good equipment to do the search," he said.
The vessel also has radar, but it wouldn't be as effective at spotting objects as small as plane debris — even if one of the objects on the satellite images is thought to be about 24 metres long.
"The chances of picking up pieces of an airplane on the surface are very small, especially when you get a larger sea, because then you have a lot of sea scatter on the radar scope," said Curl.
Spotting them by sight on the choppy seas won't be easy either, he said.
"It would be very hard to find something white or silver in those seas because of the whitecaps. they’re a lot of seas right now and waves, and the [objects] could be in the trough part of the time or down below where you couldn’t see them, so it would be very lucky if they did spot anything."
Search likely a 'multi-year project'
DeYoung estimates the hunt for the Malaysia Airlines plane will be a "multi-year project." The search for the main wreckage of the Air France 447, which crashed in 2009 in the mid-Atlantic, took two years and in that case the first debris was found within six days and searchers knew the precise point when the plane ran into trouble.
"That took years, and they had much more information, and they were working in an area of the ocean that's got more resources attached to it," he said.
One obstacle search teams won't face in the Indian Ocean is the mid-Atlantic ridge, a geological formation on the Atlantic Ocean floor whose trenches complicated the search for Air France. The southern Indian Ocean is between 3,500 to 5,000 metres deep but relatively flat.
"It's not complicated in that sense, but it's many kilometres deep, so it will be very difficult to find it and then very difficult to recover it," deYoung said.Suggest a correction