Washington, May 19 (IANS) Try finding out the exact volume of water on the earth and chances are that you will get multiple results and end up confused about which one is correct and accurate.
Inspired by the need to do away with the confusion, scientists have come up with an exact figure, 1.332 billion cubic kilometres.
Matthew Charette, associate scientist in marine chemistry and geochemistry at the Woods Hole Oceanographic Institution (WHOI), is member of a research team that has audited all the water on the planet.
“A lot of water values are taken for granted. If you want to know the water volume on the planet, you Google it and you get five different numbers, most of them 30 or 40 year-old values,” says Charette.
Charette and co-investigator Walter H.F. Smith, geophysicist at the National Environmental Satellite, Data and Information Service of the National Oceanic and Atmospheric Administration, have come with up the new ocean volume figure.
“The satellite project has covered virtually all the world’s oceans, except for some areas of the Arctic that are covered with ice,” Charette says. The result is a “new world map” of the oceans, Smith adds.
The researchers report that the world’s total ocean volume is less than the most recent estimates by a volume equivalent to about five times the Gulf of Mexico, or 500 times the Great Lakes.
While that might seem a lot at first glance, it is only about 0.3 percent lower than the estimates of 30 years ago.
What may be more interesting, Matthew says, is how accurate scientists were in the past, using cruder techniques to measure ocean depth.
As long ago as 1888, for example, John Murray dangled lead weights from a rope off a ship to calculate an ocean volume – the product of ocean area and mean ocean depth – just 1.2 percent greater than the figure Charette and Smith now report.
Starting in the 1920s, researchers using echosounders improved depth estimates significantly, according to the researchers. Most recently, Smith and others have pioneered the use of satellites to calculate ocean volume.
The trend toward a progressive lowering of volume estimates is not because the world’s oceans are losing water. Rather, it reflects a greater ability to locate undersea mountain ranges and other formations, which take up space that would otherwise be occupied by water.
Satellite measurements reveal that ocean bottoms “are bumpier and more mountainous than had been imagined,” said Smith, according to a WHOI release.
It would take a single ship 200 years (or 10 ships 20 years) to measure all the ocean-floor depths with an echosounder, according to published U.S. Navy estimates. “That would come to about $2 billion,” Smith says. “NASA is spending more than that on a probe to [the Jupiter moon] Europa.”
The work is published in the current issue of Oceanography.
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