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

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Air pollution leads to cardiovascular diseases

21.08.2018 | Ecology, The Environment and Conservation

Researchers target protein that protects bacteria's DNA 'recipes'

21.08.2018 | Life Sciences

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>