Nearly a quarter of Earth's seafloor now mapped

Nearly a quarter of Earth's seafloor now mapped
The oceans cover 70% of the Earth's surface. Of that area, 23.4% is now mapped to modern standards. Slowly but surely the proportion of the global ocean floor that's been properly mapped is rising. It's now up to just shy of a quarter of the total area under water - at 23.4%.

Better seafloor maps help us with navigation and conservation, among many other uses. Some 10 million sq km (3.8 million sq miles) of new bathymetric (depth) data was added in the past year. This is an area broadly equivalent to the land surface of Europe.

Much of this additional data comes not from recent mapping efforts, however, but simply as a result of governments, institutions and companies agreeing to open up their archives. It's thought a further 10-15% is still squirrelled away on servers, in part because the owners worry they might be giving away commercial or defence secrets if they release the information.

"But they really needn't worry," said Jamie McMichael-Phillips, director of Seabed 2030, the organisation that is trying to corral world efforts to obtain a complete picture of Earth's ocean bottom.

"One of the messages we're trying to get across is that we don't require high-resolution data. Hi-res is nice; we can work with it. But lower resolution is perfectly acceptable.

"One depth value in an area the size of a European football pitch, 100m by 100m or thereabouts, isn't going to give away national or commercial secrets."

This knowledge is needed for a host of reasons. Sea maps are essential for safe navigation, obviously, but also for fisheries management and conservation. Marine wildlife tends to congregate around the underwater mountains. Each seamount is a biodiversity hotspot.

In addition, the rugged seafloor influences the behaviour of ocean currents and the vertical mixing of water. This is information required to improve the models that forecast future climate change - because it is the oceans that play a pivotal role in moving heat around the planet. At the moment, our knowledge of just over three-quarters of the planet's underwater terrain comes only from low-resolution satellite measurements that have inferred the presence of tall seamounts and deep valleys from the gravitational influence these features have on the sea surface.

Water piles up over the mass of a large submarine mountain and dips slightly where there is a trench. It's super smart but an underwater mountain that's hundreds of metres tall can still fail to show up in such observations.

Seabed 2030, which is funded by Japan's Nippon Foundation, is encouraging anyone who ventures away from the land to switch on their sonar equipment and take depth soundings. And this isn't just about measurements from big ships; small ocean-going yachts fitted with data loggers can also make a contribution. Continue...

James Koroma