The Secrets of the Ocean Floor

Echo-sounding illustration. image from wikipedia

Three billion dollars sounds a lot to spend on a map. But if it is a map of two-thirds of Earth’s surface, then the cost per square kilometre, about $8.30, is not, perhaps, too bad. And making such a map at such a cost is just what an organisation called the General Bathymetric Chart of the Oceans (GEBCO) is proposing to do. GEBCO, based in Monaco, has been around since 1903. Its remit, as its name suggests, is to chart the seabed completely. Until now, it has managed less than a fifth of that task in detail. But means of mapping the depths have improved by leaps and bounds over recent decades. So, with the aid of the Nippon Foundation, a large, Japanese philanthropic outfit, GEBCO now proposes to do the job properly. It plans to complete its mission by 2030….

Despite water’s apparent transparency, the sea absorbs light so well that anywhere below 200 metres is in pitch darkness. Radio waves (and thus radar) are similarly absorbed. Sound waves do not suffer from this problem, which is why sonar works for things like hunting submarines. But you cannot make sonic maps from a satellite. For that, you have to use the old-fashioned method of pinging sonar from a ship. Which is just what GEBCO plans to do.,,,

[The technique used to map the sea floor] is “echo sounding”, using sonar reflected from the seabed. Marie Tharp and Bruce Heezen of Columbia University, in New York, pioneered the technique in the 1950s and 1960s by using technology developed during the second world war. With it, they mapped part of the Mid Atlantic Ridge, an underwater mountain chain…

Cable-laying companies, oil firms, academic oceanography laboratories, national hydrographic surveys and the world’s navies all have oodles of sounding data. One of GEBCO’s jobs is to gather this existing information together and sew it into a new database, to create a coherent portrayal of the known ocean floor.  The organisation is also keen to include data collected by helpful volunteers. A new digital platform overseen by America’s National Oceanic and Atmospheric Administration encourages the crowdsourcing of bathymetric data, letting mariners upload their findings easily. Recent political initiatives, such as a deal made in Galway in 2013 between America, Canada and the European Union to support transatlantic floor-mapping, will also boost efforts. National icebreakers are gathering information in parts of the ocean too frozen for other vessels to reach. And GEBCO is trying to persuade governments and companies with proprietary data on the sea floor to share them. One such firm, a cable-laying outfit called Quintillion, has already agreed to do so…

[A] accurate map of the seabed may help open this unknown two-thirds of Earth’s surface to economic activity. ..[T]he world’s navies (or, at least, those among them with submarine capability) will also take an interest—for an accurate seabed map will both show good places for their boats to hide and suggest where their rivals’ vessels might be secreted. Whether they will welcome GEBCO making this information public is a different question

Excerpt from Bathymetry: In an octopus’s garden, Economist,  Oct. 29, 2016

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