Monday, March 13, 2017

From flight 370 hunt, new insight into Indian Ocean’s unknown depths

A 3-D image of the Diamantina Escarpment on the seafloor of the Indian Ocean.The search for Malaysia Airlines Flight 370 has helped create maps revealing the ocean floor’s topological complexity. 
Credit Kim Picard and Jonah Sullivan

From NYTimes by Nicholas St Fleur

On March 8, 2014, Malaysia Airlines Flight 370 vanished with 239 passengers and crew aboard as it crossed the Indian Ocean, triggering a large-scale search for its remains that lasted nearly three years.

 South West of Australia with the GeoGarage (AHS chart)

 As a byproduct of the tragedy, scientists have gained access to more than 100,000 square miles of seafloor mapped at a level of detail that provides a rare look at the ocean’s geological processes.
“It’s an incredible trove of data,” said Millard F. Coffin, a marine geophysicist from the Institute for Marine and Antarctic Studies at the University of Tasmania in Australia. 
“I’ve been working in this part of the Indian Ocean for 30-plus years and over many voyages in the eastern Indian Ocean I’ve never seen this level of resolution.”
Dr. Coffin worked with a group of about 10 scientists from Geoscience Australia, the national geosciences agency in Australia, to analyze data from the search. 
They were given access to high-resolution sonar information collected on ships, and data obtained by remotely operated vehicles and autonomous underwater drones. 
The information was provided by the Australian Transport Safety Bureau, which led the search.
“When we look at these data, we’re constantly keeping in mind that we wouldn’t have this data if it weren’t for a terrible tragedy,” Dr. Coffin said.
 He and his colleagues published a summary of their findings on Wednesday in the journal EOS.

 A 3-D model of the Broken Ridge along the Diamantina Escarpment. 
Credit Geoscience Australia 

Previous satellite data provided scientists with information about the Indian Ocean at a resolution of about five square kilometers, or about two square miles. 
With the instruments from the search ships, they have collected information at a resolution of meters, and in some locations they have used remote operating vehicles and underwater autonomous vehicles to gain detail on the scale of centimeters.
The search has helped create three-dimensional maps of the ocean floor that reveal its topological complexity and will allow researchers to further investigate unique features like the oceanic plateau called Broken Ridge, and its southern-flank Diamantina Escarpment
The Flight 370 search also provided information about tectonic and volcanic activity, Dr. Coffin said.
The team plans to release more detailed looks into its findings later in the year, and the full data set from the search will be made available in the middle of the year.
Walter H.F. Smith, a geophysicist with the National Oceanic and Atmospheric Administration, said the hunt for the lost jetliner highlighted how little we know about the oceans. 
In a paper that was also published Wednesday in the journal EOS, he and his colleagues explained how common unmapped areas of ocean are.

 Satellite-derived gravity field (gray) [Sandwell et al., 2014] and multibeam echo sounder (color) data were used to produce these maps of the MH370 search area in the southeast Indian Ocean.
The relief models are shown in Sun-illuminated (shaded relief) mode.
The inset map shows the MH370 search area that was mapped with multibeam echo sounding (shown in red).
This map highlights the Southeast Indian Ridge (SEIR) and the Kerguelen Plateau, and it includes estimated spreading rates of the SEIR [Argus et al., 2011], lines delineating regions of approximately equal age (isochrons [Muller et al., 2008]), and interpretations of SEIR segments (I–VII [Small et al., 1999]).
Other abbreviations are AAD, Australian-Antarctic Discordance; CIR, Central Indian Ridge; RTJ, Rodriguez Triple Junction; SWIR, Southwest Indian Ridge; WA, Western Australia.
The larger map shows details of the ocean depth mapping effort using multibeam echo sounder bathymetry data. Locations of Deep Sea Drilling Project (Leg 26) and Ocean Drilling Program (Legs 121 and 183) Sites 255, 752 to 755, 1141, and 1142 are also indicated, as are the locations of Figures 2, 3, and 4.
 Multibeam echo sounder bathymetry map of two regions of the ocean floor around the Geelvinck Fracture Zone in the Australian-Antarctic Basin south of Broken Ridge (see above for locations).
The fracture zone offsets the SEIR by about 310 kilometers. 
The right-lateral transform fault motion (a person standing on one side of the fault would see the opposite side displaced to the right) that created this fracture zone was mostly horizontal.
Note the fracture zone fault valleys, mid-ocean ridge spreading fabric, and isolated volcanoes.

“There are all kinds of things you can’t do if you don’t know the shape of the ocean bottom, or don’t know it properly,” Dr. Smith said. 
The consequences of not knowing, he said, can hinder how experts predict tsunamis, understand ocean currents, make climate forecasts, study marine life and search for missing planes.
Previous studies have suggested that only 8 percent of the world’s oceans have been mapped, meaning that a ship measured an area’s depth and recorded it in a scientific database. 
Before Flight 370’s disappearance, only 5 percent of the southeast Indian Ocean had been mapped, Dr. Smith said.
The differences in resolution between multibeam and satellite-derived bathymetry data for the northern flank of Broken Ridge are apparent here.
Numerous mass wasting features are evident, including slides and debris flows (delineated by their head scarps) that crosscut and run out as debris fans into the large semicircular depression

To figure out how often people fly over unmapped parts of the world’s oceans, 
Dr. Smith and his colleagues compared data on mapped and unmapped segments of the world’s ocean segments with a database of commercial airline routes
They found that about 60 percent of all commercial flights that cross over the ocean travel over waters with unmeasured depths.
The longest contiguous route over unmapped ocean was from Kennedy International Airport in New York to Chongqing Jiangbei International Airport in China, a journey over more than 1,200 nautical miles of unmapped ocean.
“I wanted people to realize that it’s not just Malaysia Airlines straying into the southeast Indian Ocean where it shouldn’t have been,” he said. 
“Even when your aircraft is exactly where it’s supposed to be, it might be over unknown ocean.”

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