Malaysia Airlines MH370: The challenges of a remote ocean search

The sighting of possibledebris from the missingMalaysiaAirlinesplane in the far southern reaches of the Indian Oceanmay be the best lead those searching for the Boeing 777 jet have had intwo weeks. But even if the find is confirmed, it couldtake years to locate the precise crash site and recover the plane.

The area 2,500 kilometres southwest of Perth, Australia, where satellites picked up images of twoobjects large enough to possibly be parts of aplane, 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's notorious for being very,very rough, and it's onlygoing to get worse from this time on into the winter.- Capt. Chris Curl,ScrippsInstitution ofOceanography

Itis far from regular shipping routes and any land masses andis known for rough seas andstrong winds.

It's fall in theregion, 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 theScripps Institution ofOceanography at University of California, San Diego.

"It's notorious for being very,very rough, and it's onlygoing 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 gowrong,helpis a long way away."

Stormy seas complicate search

The area where the search for the potential debris is concentratedis in Australian waters in a region between the southern latitudes of 40 and 50 degreesknown as the "Roaring Forties"for its strong currents andstormy, windyweather, 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 keepcirclinground 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 FlightMH370, the route back towhere it came from will be long and no less confounding.

"It's been [13] 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," saidBrad deYoung, professor of oceanography at Memorial University in St. John'son Thursday.

"But beyond that, theindividual objects that fell wouldhave 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 thispart 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 currentsactive in that part of the ocean. Curl, assuming a speed of about two to three knots for 13 days, estimatesthat, as of Thursday, a good placeto start looking for the crash site would be around 1,100 kilometres west ofwhere the suspected debris was spotted.

But that kind of estimatewould still leave searchers with a hugearea 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 runningmathematical models thatwind back the clockand try to pinpoint wherethe debris was 13 days ago based on where it is now and usingmore precise information about currents, weather and ocean circulation.

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"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 oceanographerat 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 aroundwith the ocean currents, wedo have quite a lot of coverage in that part of the world, so we have a pretty goodunderstanding of the circulation there."

The more debris, the better

The more pieces of debris you find, the better the estimate of where the crash sitemight be, says deYoung, althoughdifferent types of debris will have drifted differently, which complicates thecalculation. Lighter objects like seat cushions whichfloat on the surfacewill be more affected by winds and surface currents while heavier itemsthatare partly submergedare moresusceptibleto deeper currents.

The circle of uncertainty grows the farther back we go. If another week goes by, then the debris you find won't be very helpful.- Brad deYoung, oceanography professor, Memorial University

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 satellitesaren't therecontinuously," Waterman said. "They're onlypassing over a particular spot on the globe everyonce in while,so in order to make use of that information, you'd have to beextremelylucky that the satellite was at the right point when impact happened."

Satellites images are being analyzed as part of the wider search effort, including through a crowdsourcing platform called Tomnod run by DigitalGlobe, the U.S. company that provided Australian authorities with the recent Indian Ocean images of the two objects. But over the open ocean,such images are limited in the amount of detail they can provide, says Alexander Wong, a specialist in imaging systems at the University of Waterloo.

"In these types of cases, the contrast between the actual object and the ocean is actually pretty low, so it's very hard to identify,"he said. "All they can really say is there's some kind of interesting object there of a certain size."

Binoculars the best tool for the job

The more detailed search for the debris is beingconducted from the air by planes equipped with human spotters andsurveillance equipment such as synthetic aperture radar, which can scan the ocean surface for large objects, and sonar for underwater detection and from the sea by aNorwegian merchant vessel that was diverted to the area while transporting vehicles toAustralia.

TheHoeghSt.Petersburgwas on its way from Durban, South Africa, to Melbourne (by way of Madagascar, Reunion and Mauritius)when it was asked to join the search on March 18, and it took the cargo ship a day to reach the initial search area. It had been headed back to its regular route after not finding anything when it was sent to the new search zone on Thursday. A secondmerchant vessel arrived Friday.

The crew on the 230-metre long HoeghSt.Petersburgis relying mainly on binocularsto conduct thesearch, whichErik Giercksky of the Norwegian Shipowners Association said is "the best equipmentfor 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, butit wouldn't be as effective at spotting objects as small as plane debris even if one of the objects on the satellite imagesis thought to be about 24 metres long.

"Thechancesof picking uppiecesof an airplane onthesurface are very small,especially when youget alarger sea, becausethen you have a lotofsea scatter on theradarscope," 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 ofAir 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 andsearchers knewthe precise point wherethe 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 the Atlantic, which hasmore shipping, more peoplemoving throughit,more capacity for doing that kind of work," he said.

One obstacle search teamswon't face in the Indian Ocean is the mid-Atlantic ridge, a geological formation on theAtlantic Oceanfloor whose trenches complicated the search for the Air France jet. The southern Indian Ocean is between 3,500 to 5,000 metres deep butrelatively flat.

"It's not complicated in that sense,but it'smany kilometres deep,so it will be verydifficultto find it and then verydifficultto recover it," deYoung said.