Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

WHOI Study Calculates Volume and Depth of the World’s Oceans

19.05.2010
How high is the sky? Scientists have a pretty good handle on that one, what with their knowledge of the troposphere, stratosphere an the other “o-spheres.” Now, thanks to new work headed by the Woods Hole Oceanographic Institution (WHOI), they are closing in on the other half of that age-old query: How deep is the ocean?

They’re also tackling an even more intriguing—if less romantic—question: What is the volume of the Earth’s oceans? It’s hard to imagine Irving Berlin putting those words into the mouth of a serenading lover—as he did in his classic song, “How Deep is the Ocean?”—let alone the answer: 1.332 billion cubic kilometers.

But that figure is pure music to the ears of Matthew Charette, an associate scientist in WHOI’s Department of Marine Chemistry and Geochemistry who is part of a research effort to audit all the water on the planet. “A lot of water values are taken for granted,” he says. “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.”

Until now.

Using satellite measurements, Charette and co-investigator Walter H.F. Smith, a 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. Their work, funded in part by the EarthWater Institute, is published in the current issue of the journal Oceanography.

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% lower than the estimates of 30 years ago.

What may be more interesting, he 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% 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. As measurements improve, ocean-volume values are lowering, he notes, emphasizing that this does not reflect an actual lessening of water but a more accurate accounting of undersea formations.

Satellite-based radar cannot “see” the ocean bottom, he explains. Rather, it measures the ocean surface, which reflects what lies beneath. For instance, if a mountain range lurks under a certain part of the ocean, the surface above it will bulge outward. “I take the data set and estimate the location and height of the mountains,” Smith says.

The satellite project has covered virtually all the world’s oceans, except for some areas of the Arctic that are covered with ice, he says. The result is a “new world map” of the oceans, Smith adds. “Matt and I are seeing a better picture of the shape and volume of oceans.”

But satellite measurements have their shortcomings. “There is a problem of spatial resolution, like an out-of-focus camera,” says Smith. “We’re measuring the sea surface that is affected by mountains,” he says, “but we’re seeing only really big mountains, and in a blurry way. The resolution is 15 times worse than our maps of Mars and the moon.”

Consequently, the researchers say, more ship-based measurements are needed to augment and “fine tune” the satellite data. And so far, ship-based sonar and other instrumentation have mapped only 10% of the Earth’s seafloor. “We have gaps in echosounding measurements as wide as New Jersey,” says Smith.

It would take a single ship 200 years (or 10 ships 20 years) to measure all the ocean-floor depths with an echsounder, 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.”

Charette and Smith are not sure why so little ship-based ocean mapping has been done throughout history. It may be because ocean depth and volume seem to have few direct, practical implications.

However, Charette notes, accurate estimates of ocean depth and volume could tie in with the growing field of ocean observation and exploration as well as, perhaps, climate change models and estimates of salt in the oceans.

And for those of you wondering—as Berlin put it so eloquently in his music—if you ever lost your love, how much would you cry? Apparently not as much as you might have 30 years ago. The study’s calculation of the ocean’s mean depth is 3,682.2 meters—that’s 21-to-51 meters less than previous estimates.

The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans' role in the changing global environment.

WHOI Media Relations | EurekAlert!
Further information:
http://www.whoi.edu

More articles from Earth Sciences:

nachricht Stagnation in the South Pacific Explains Natural CO2 Fluctuations
23.02.2018 | Carl von Ossietzky-Universität Oldenburg

nachricht First evidence of surprising ocean warming around Galápagos corals
22.02.2018 | University of Arizona

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>