By Jonathan Amos
Science correspondent, BBC News, Bergen
It is one of the most exquisite views we have ever had of the Earth.
This colourful new map traces the subtle but all pervasive influence the pull of gravity has across the globe.
Known as a geoid, it essentially defines where the level surface is on our planet; it tells us which way is “up” and which way is “down”. It is drawn from delicate measurements made by Europe’s Goce satellite, which flies so low it comes perilously close to falling out of the sky.
Scientists say the data gathered by the spacecraft will have numerous applications. One key beneficiary will be climate studies because the geoid can help researchers understand better how the great mass of ocean water is moving heat around the world.
The new map was presented here in Norway’s second city at a special Earth observation (EO) symposium dedicated to the data being acquired by Goce and other European Space Agency (Esa) missions.
… Imaginary ball
Launched in 2009, the sleek satellite flies pole to pole at an altitude of just 254.9km – the lowest orbit of any research satellite in operation today.
The spacecraft carries three pairs of precision-built platinum blocks inside its gradiometer instrument that sense accelerations which are as small as 1 part in 10,000,000,000,000 of the gravity experienced on Earth.
This has allowed it to map the almost imperceptible differences in the pull exerted by the mass of the planet from one place to the next – from the great mountain ranges to the deepest ocean trenches.
Two months of observations have now been fashioned into what scientists call the geoid.
…Put a ball on this hypothetical surface and it will not roll – even though it appears to have “slopes”. These slopes can be seen in the colours which mark how the global level diverges from the generalised (an ellipsoid) shape of the Earth.
In the North Atlantic, around Iceland, the level sits about 80m above the surface of the ellipsoid; in the Indian Ocean it sits about 100m below.
The geoid is of paramount interest to oceanographers because it is the shape the world’s seas would adopt if there were no tides, no winds and no currents.
If researchers then subtract the geoid from the actual observed behaviour of the oceans, the scale of these other influences becomes apparent.
This is information critical to climate modellers who try to represent the way the oceans manage the transfer of energy around the planet.
…
http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/8767763.stm
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It would be good to see the same map in some sort of an “equal area” projection.
In that case its possible that the Indian to Indonesian difference would show up as quite a lot bigger than the anomaly near Iceland.
Then the climatic/seismic relationship that some meteorologists have alluded to might be interesting. Referring to the flow of warm water from the Indian Ocean into the “pacific warm pool” through the seismically active Indonesian island arc.
Mapping gravity: really really cool.
Finding a way to make it about “climate change”: really really lame.
Potentially a great scientific achievement. Hopefully GOCE can also measure how much mass is gained by the ice sheets (ref. dot point 9.)
i dont understand how the area where Mt Everest is approx -60 m And the trench in the alantic ocean is + 6o ish meters . Im confused
“…This is information critical to climate modellers who try to represent the way the oceans manage the transfer of energy around the planet.”
I thought those models were already so perfect, we could bet the economic future of the entire planet on their output. The science was settled.
Could the gravity-variance come from CO2?
d
June 28, 2010 at 9:02 pm
The surface represents the pull of gravity. If you take a point on the surfaces, the normal will be in the direction of that pull. A normal is the line that is perpendicular to the tangent plane at that point. A tangent plane is the plane that just touches the point. So it is the gradient of the surface that is really important.
d says:
June 28, 2010 at 9:02 pm
> i dont understand how the area where Mt Everest is approx -60 m And the trench in the alantic ocean is + 6o ish meters . Im confused
60ish, not 6oish. Etc. You aren’t paying attention!
The satellite measured a stronger gravitational field over the Himalayas thanks to the extra mass in that area. Over things like trenches, there’s less mass. Even though there’s water there, it’s specific gravity is only about 1 gm /cm^3 whereas rocks are about 5 gm /cm^3. some other differences may be due to rock composition.
BTW, a standard oil (and other mineral) exploration technique entails detailed surface level gravitometer measurements. Oil is low density, so where the gravitational field is weak there’s a better chance that oil is under foot than in areas with a higher field.
It seems to be a gravity anomaly detector. The ball at 4. won’t roll on the slope as the gravity pull on both sides of the hill will ‘point’ towards an area of high gravitational attraction, probably basaltic, that is not aligned with earth’s centre. So a gravity anomaly height contour is produced and compared with an expected ellipsoidal shape. I expect dense basalt would produce height ‘bubbles’ and less dense granite (Himalayas) would produce dips. My guess anyway. Interesting fact mentioned that acceleration due to gravity at the poles is 9.83m/sec and at the equator is 9.78m/sec. Closer to the iron core at the poles?
Not sure what this has to do with measuring ocean current flow.
I should add that continents are made of “light” rock floating on top of denser rock. Dense rock of course has more gravitational pull.
“It is one of the most exquisite views we have ever had of the Earth.”
It is not really a “view” of the earth, it is a geoid with a lot of physics and averaging hidden in it, so that it is horozontal at every point, but it does have slopes you can see. So I would say it is neither “exquisite” nor a “view,” but it is a static baseline of sorts.
Geoid…it means earth shaped!
New Scientist ran an article recently on a possible meteor impact causing the Deccan Traps https://www.newscientist.com/article/mg20627631.300-deeper-impact-did-megameteors-rattle-our-planet.html (just a summary, too new for the full article).
Wonder if the blue area on the southern tip of India is the signature of an impact crater?
Oh great, someone let the plug out of the Indian Ocean.
“Unusually quiet solar activity has produced very calm atmospheric conditions, meaning Goce has used far less xenon “fuel” in its ion engine to maintain its orbit. ”
Yep, the sun has NO effect on climate…
The science correspondent managed to really confuse and badly explain what it is and what it means… really bad journalistic job.
Hansen The Weather Clown: “Can’t we color high gravitational fields bright red and tie them in with civilization? That way people will think that gravity is being affected.”
BTW, this was done to the moon over 20 years ago. We are dealing with rocket science.
9. Gravity data can also reveal how much mass is lost by ice sheets
Would it be presumptious to assume it could also reveal how much mass is gained by ice sheets? Or maybe the ‘science’ is designed not to show that?
sorry about the typo
Keith Minto:
“Interesting fact mentioned that acceleration due to gravity at the poles is 9.83m/sec and at the equator is 9.78m/sec. Closer to the iron core at the poles?”
Interesting take, as I might have thought as well. It’s likely also due to centrifugal force of the planet’s rotation. If the latter is the case, the lightest you could be on the planet is flying at 33,000 ft at midnight with a lunar eclipse.. 😉
This is new to me. Conceptually I’m having trouble understanding what is being shown. Can someone take a few minutes and walk us through an understandable explanation of the implications of this map? Thanks so much.
“If researchers then subtract the geoid from the actual observed behaviour of the oceans, the scale of these other influences becomes apparent.
This is information critical to climate modellers who try to represent the way the oceans manage the transfer of energy around the planet.”
It will be interesting to see if any of the motions in the changing geoid correlate with geomagnetic meanderings. That would be indicative that the satellite was capturing the movement of iron rich molten material under the Earth’s crust responsible for most of the changes in the Earth’s Length Of Day (LOD) as well as the movement of less dense, warm ocean water. How will they seperate the two? They mention magma under volcanos, so presumably they have a handle on this.
Here’s another uninformed comment. The red seems to be the location of recent volcanic, earthquake/tectonic movement. Any correlation or causation suggested?
Bob of Castlemaine says:
June 28, 2010 at 8:52 pm
Agree with you Bob, interesting that the BBC chose to describe Point 9 as a “loss” rather than a balance change, either positive or negative.
God Bless the Beeb. Where would we all be without our taxpayer funded Newspeak organisation? /sarc