Exciting news! A piece of what could be erstwhile MH370 has turned up. Its location seems puzzling at first, mostly because oceanographic literacy is understandably rare in the reporting world.
The wing part washed up recently on the French island of Reunion, in the Indian Ocean east of Madagascar. On the surface this seems odd because many experts believe that MH370 crashed when it ran out of fuel in the south and west of Australia, also in the Indian Ocean but a long way from Reunion. Reaching that little island would be a long trip given that plane’s fuel reserves, and it might call for a significant detour around our powerful radars in Diego Gracia. But in fact some cocktail napkin calculations I think Reunion could be quite consistent with the original crash theories.
The first thing you need to know is the surface of the ocean is everywhere in motion, driven by the prevailing winds and bent by coastlines and the gentle tug of Earth’s rotation. You probably know about the Gulf Stream, part of the great gyre that circulates surface water clockwise around the northern Atlantic. All major oceans have gyres like this, and unlike your Australian friend’s toilet they do respect the Coriolis effect, so these gyres circulate clockwise in the Northern Hemisphere and counter-clockwise in the South.
If it followed expectations then debris from MH370 would have ended up in the southern Indian Ocean’s primary gyre, called the South Equatorial Current or SEC. It loops east through isolated Antarctic waters, heads north off of Western Australia and then takes a very long journey just south of the equator, arcing north and west from Perth and then back south again until a brushes past the island of Madagascar. Within the SEC you can find a number of tiny, isolated island chains, from the Cocos in the east to Diego Garcia with its strategic airfield over to the Reunion on the western edge of the Indian Ocean. If you stand on the southern shore of Reunion and toss a bottle in the water, there is a small but nonzero chance that a beachcomber in the Cocos islands 2,800 miles away will trip on it some time later.
So I asked whether MH370 would have enough time to tour two thirds of the SEC. That wing spar would have spent most of its trip in the northern SEC, where surface currents average a hair over one mile per hour. That adds up to just under nine thousand miles per year (one mile per hour sounds slow, but a year has a lot of hours in it). Floating the SEC in the outside lane, which includes Reunion and the estimated crash site, you have a full circle of ten to twelve thousand miles. That puts the debris in about the right place and time if it followed the canonical trajectory of the Indian Ocean’s southern gyre. I would say the odds of a piece of debris from MH370 finding a spit of land as small as Reunion is pretty tiny, but if it were to find a tiny island somewhere then Reunion seems like as good a place as any to look for debris.
Large parts of airplanes all have serial numbers like the VIN on an automobile, so we will know for sure pretty soon. Plus apparently Boeing is only missing one set of 777 wings.