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
//
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
Cool, so if the ocean was still enough it would have hills.
So much green and so little red – shouldn’t they use another colour code to remain consistent with climate science ?
kwik says:
June 28, 2010 at 9:41 pm
Could the gravity-variance come from CO2?
Oh man, now ya done gone and done it!
We’ll now be hearing all about ‘Anthropogenic Global Gravity Change’ … 😉
Cool, so if the ocean was still enough it would have hills. That would be great for waterskiing
Policyguy says:
June 28, 2010 at 11:14 pm
Policyguy,
The map is showing the changes in gravity (acceleration) across the surface of the Earth. Gravity is proportional to a body’s mass and distance between it and another mass (ht Sir Isaac Newton, Law of Universal Gravitation) F=G(mass1*mass2)squared.
Our planet does not have a regular surface from a rock density perspective, and the changes in the density of the rocks that make up the lithosphere (top crust, oceanic and continental crust) and lower sections of the earth’s crust (asthenosphere, upper mantle, lower mantle and outer/inner core) identify rock density and as per your second post correctly identifies, areas of tectonic activity.
Areas of the earth’s crust where seafloor is being actively created (seafloor rock generally has a higher density than continental rock) show as anomalous highs (over Iceland and tracking the Atlantic tectonic spreading ridge to the south) as well as over the area of Indonesia/Malaysia/heading towards New Zealand which is also tectonically active with creation of new seafloor.
Density lows can bee seen to correlate with sedimentary basins (sedimentary rocks have lower densities than seafloor rock), the very large one south of India being a classic case. The one under the Great Lakes/Souther Canada is also a sedimentary basin.
This is a gross description of the general process but it gives a rough idea of what it’s all about.
I must be thick because it is not obvious to me what is being shown either. The Himalayan plateau is several thousand metres high but does not show up. The Pacific trench is thousands of metres deep and does not show up. Is this map perhaps showing the difference between the measured heights from sea level and those calculated using gravity measurements? I can see how this would be more valuable than the actual variance in gravity measurement. However if this is the case it would be interesting to see the raw data as well.
In time it will help to see how the map changes, for a variety of reasons. So far I have not read up on the surface resolution – it looks coarse when contoured this way – but I doubt if it reveals much not known already to geophysicists already working with gravity.
In mineral exploration work, the emphasis is often on resolution of gravity differences between points less than a km apart. This airborne instrument is of little help there, but it’s a neat piece of engineering.
It’s a pity that few geologists can agree about the composition of sub-crustal Earth, because that affects the gravity interpretation. Currently, there is no way to measure the sub-crust directly, so in a way the philosophy of this gravity science resembles the selection of CO2 as a warming cause partly because it explains a gap in model predictions. Different investigators will have their beliefs about the sub-crust and their models will reflect this, but it’s not evidence-based.
Richard Hill says: June 28, 2010 at 8:25 pm
It would be good to see the same map in some sort of an “equal area” projection.
You can see global view on my website I recorded some time ago.
http://www.vukcevic.talktalk.net/NFC.htm
tallbloke says: June 28, 2010 at 11:20 pm
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)
That is indeed case in some locations. In my article dealing with the North Atlantic temp anomaly I have maps directly relating to the effect.
http://www.vukcevic.talktalk.net/NATA.htm
tallbloke says: June 28, 2010 at 11:20 pm
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)
That is indeed case in some locations. In my article dealing with the North Atlantic temp anomaly I have maps directly relating to the effect.
http://www.vukcevic.talktalk.net/NATA.htm
pages 3 and 4 then 8 and 9
“5. It is the shape the oceans would take without winds and currents”
and the moon?
tallbloke says: June 28, 2010 at 11:20 pm
It will be interesting to see if any of the motions in the changing geoid correlate with geomagnetic meanderings.
Indian Ocean gravity anomaly does not appear to show magnetic anomaly. Hudson Bay area is only one where two are coincidental.
http://www.ngdc.noaa.gov/geomag/data/mag_maps/browse/Z_map_mf_2005_large.jpeg
Ocean currents do not appear to be greatly affected by gravity anomaly.
http://upload.wikimedia.org/wikipedia/commons/6/67/Ocean_currents_1943_(borderless)3.png
It should be remembered that these anomalies are not particularly large. They are measured in miligals, units of acceleration commonly used in geodetic measurements, equal to 10E-3 Galileo, or 10E-5 meter per second square (10E-5 m/sec2).
Most readers seem to think that this is something static, whereas most of the earth is not solid but molten, and so these gravitational anomalies might change with time. If one compares this map with that of sea level rise, for example http://buythetruth.files.wordpress.com/2008/11/altimetry.jpg?w=375&h=236 there is an interesting correlation. In the northern Indian ocean, sea level rise is zero or negative. Around Indonesia it is very high positive. Off the west coast of USA (California) it is stable or declining slightly. North Atlantic has increasing sea level.
This gravitational map is merely a snapshot. Variations in the gravitational anomalies over time cause variations in sea level. So, as we can see here, it is possible for parts of the Indian ocean to be decreasing in sea level (e.g. around the Maldives), but for rising sea level a thousand miles to the east in Indonesia. The fact that sea level can be rising in one place and decreasing a thousand miles away at the very least (now that we have this gravitational map with reasonable correlation to sea level trends) makes it worth considering whether variations in the gravitational anomalies are a significant factor in sea level trends.
One can imagine that if the gravitational anomalies change significantly over time, then the effects on sea level could in any location outweigh the effects of melting ice etc. Notwithstanding the appalling grandstanding by the Maldives’ president, there is no sea level rise around the Maldives – it has declined since the 1970s, whereas there is noticeable sea level rise around some islands in the southwest Pacific. I can’t help wondering whether that deep blue around the Maldives and the deep orange in the south Pacific are telling us something about the causes of that.
I must admit I don’t quite understand what this is all about.
I make one thing of it so far. If all the fat people migrate to the dark blue areas, they can feel good about themselves. Oh, yes, also, anorexics should stay away from the red bits.
Graham Dick”
““5. It is the shape the oceans would take without winds and currents”
and the moon?”
Good point Graham. Not sure if the Moon’s gravity was removed from the data.
I’m still experimenting with HTML tags..</quote Please bear with me as they seem to have different effects from site to site.. 😉
BuggerDamn!I’m an assembler programmer. Moderators, please remove the above if not funny enough..
@Policyguy: The map is showing the change in height needed to maintain the same potential energy. So comparing two people of the same mass, one goes to Sri Lanka and another to Iceland. Because the gravity is stronger over Sri Lanka (denser/thicker rock) that person would have to move closer to the centre of the earth relative to the person in Iceland (less dense/thinner rock) to have the same potential energy.
So any water at Sri Lanka with higher potential energy than the surrounding water would move away, like a ball rolling, or rivers flowing, downhill, so we would expect deeper water at Iceland (ie water further from the centre of the Earth) than at Sri Lanka.
Excuse my rusty Physics
all Im am worred about is where is my next grant comming from
I don’t understand how balls won’t roll on it’s surface slopes. If the gravity pull on one edge of a ball is higher than on the other edge, the ball will roll.
What about fulcrum balances? Equal weights at each end. Will such balances on a slope be unbalanced? I would think so.
My Gosh! Sir Isaac Newton was WRONG! /sarc
ScientistForTruth says:
June 29, 2010 at 2:03 am
…The fact that sea level can be rising in one place and decreasing a thousand miles away at the very least (now that we have this gravitational map with reasonable correlation to sea level trends) makes it worth considering whether variations in the gravitational anomalies are a significant factor in sea level trends.
Indeed. What would be the effect on sea level if the density of the matter below the crust varies across the oceans? I tend to think it will be fairly negligible. Several milimeters, rather than several Cms.
Baa Humbug says:
June 29, 2010 at 2:11 am
I make one thing of it so far. If all the fat people migrate to the dark blue areas, they can feel good about themselves. Oh, yes, also, anorexics should stay away from the red bits.
Ha ha! I remember throwing away Hal Clement’s ‘Mission of Gravity’ after only ten pages or so. Not because I wasn’t curious about what came next but because it made me feel so, so heavy. The book is set on a planet called Mesklin where the gravity ranges from 3g on the equator to 700g at the poles.
Maybe someone can help me with this. In projecting sea level changes due to the myriad processes that worry the warmists, is it possible that there are too many variables whose coarseness or unknowableness would exceed the likely change values.
(maybe too much in sentence above)
If sea level changes are in mm increments, wouldn’t they be lost in terms of reliable measureability in the local conditions and “oscillations” discussed above including some very informative comments?
Further to the above. This business with picking signals (sea level changes for example) out of the noise using statistical legerdemain seems to rely on agility in identifying what is and what isn’t signal – not that there may be no signal.
Likely I’m all wet here and this has been sloshed about at great length by the people who understand it better than me.
What’s that land mass peeking out from the left margine, Southwest of Hawaii?
Lost continent of Pacificus?
Steve (Paris) says:
June 28, 2010 at 11:02 pm
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?
Gravimetry can indeed show mass being gained as well as lost by ice sheets. Glaciology is not “designed” to show things in a certain way. If it were so, then why would radar altimetry have been used for so long despite bias’ towards ice sheet gain? Glaciologists have their work shown to the world every day, when a glacier advances we can’t just lie about it. And for the record, it would be presumptious to assume that there will be mass gains by any of the ice sheets considering how much mass is currently being lost by all three ice sheets according to laser altimetry, radar interferometry, Gravimetry and melt modeling. And yes that includes EAIS.
J Fergusson I think you’re on to something. The climate changer’s sea level rise might be a case of cherrys picked from natural low grav fields. This map’s high and low gravity points seem to correspond with Roy Spenser’s temp anomaly map pretty well
My how we have progressed, most land masses were very accurately surveyed for gravity and magnetic anomalies in the nineteen sixties. In australia we used Lockheed Hudson WW2 aircraft with huge sensors hanging off them. The data gathered for specific gravity and magnet anomalies was used to locate our mineral wealth. Now a spy in the sky, the mining companies will be wetting themselves. AGW has no dibs on this satellite, this is a money maker.
Blue means weaker gravitation, red stronger?
If the ball (4), lay on the elipsoid surface (1) it would roll from Sri Lanka to Papua given friction = 0?
I had thought the true shape of the Geoid was classified because that’s the data that cruise missiles use to “know” their altitude above the surface.
Climate ain’t heavy. He’s my brother.
@Philip T. Downman: Blue=stronger, Red=weaker.
See my previous comment (http://wattsupwiththat.com/2010/06/28/21178/#comment-419323).
The map is clearly calibrated in metres, not gravity strength. You can see that from the colour-code strip at the bottom.
Hey, we in the UK and Iceland don’t need to worry about global warming !!
@Philip T. Downman: “If the ball (4), lay on the elipsoid surface (1) it would roll from Sri Lanka to Papua given friction = 0?” Yes.
@kzb: “Hey, we in the UK and Iceland don’t need to worry about global warming !!”. Quite the opposite as we are effectively downhill (potentially speaking) relative to the Indian Ocean!
Is it just me or have others noted that the degree of AGW moonbattery is correlated with a high level of gravity?
Ric Werme says:
June 28, 2010 at 9:45 pm
‘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.’
So that’s what happen to the Rocky Mountain Chain.
Olaf Koenders
June 28, 2010 at 11:13 pm
The earth is an oblate spheroid so the surface at the poles is closer to the center of mass then at the equator. The closer to the mass, the greater the gravitational acceleration.
kzb says:
June 29, 2010 at 6:14 am
The map is clearly calibrated in metres, not gravity strength. You can see that from the colour-code strip at the bottom.
Hey, we in the UK and Iceland don’t need to worry about global warming !!
That bit is obvious but does the geoid run several metres above the Himalayan plateau or several thousand metres below it?
From the article- 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.
Interesting statement that as indirectly noted by: Graham Dick who said at 1:41 am
“5. It is the shape the oceans would take without winds and currents” and the moon? To which I will add; the Sun, Jupiter, Venus and Mars.
Picture the satellite in polar orbit as it traverses the earth from pole to pole and round again. As the satellite comes AND goes in ever varying momentary direct line between the center of these “other” gravitational bodies and the earths, certainly the variance in gravitational accelerations is greater than 1 part in 10,000,000,000,000. Would not the satellite need to be shielded from those very dynamic (due to it’s speed) variances? OR it would need to “sense” them somehow separately to compensate (add or subtract the influence) to derive at a true “Earth only” acceleration measurement?
And:
6. So, comparing sea level and geoid data reveals ocean behaviour
(WHAT? Without centrical force, temp. and salinity variances taken into account?)
7. Gravity changes can betray magma movements under volcanoes
(ONLY volcanoes? and NOT the Earth’s molten iron core?)
8. A precise geoid underpins a universal height system for the world
(“height system” that would tell us what? The distance from the exact center of the Earth to ??? And so?)
Not only am I concerned with the veracity of the data being “generated” by this multi-million euro project but also knowing what the look of a “virtual level Earth” is at a given point in time/space. What use is knowing the “difference” between the real Earth and this computer generated level Earth? Hey, don’t get me wrong. I am all for knowing EVERYTHING! You never know when some abstract piece of data is going to fit into or complete the puzzle. But this “sounds like” a boondoggle OR a tool to prove – – well, almost anything you want. June 29, 2016. NASA “We have determined the oceans are rising globally by 20.39674482901 meters per year by comparing globally averaged ocean hight measurements to our Virtual Flat Earth Model.”
j ferguson says: June 29, 2010 at 4:12 am “If sea level changes are in mm increments, wouldn’t they be lost in terms of reliable measureability in the local conditions and “oscillations” discussed above including some very informative comments?”
sHx says: June 29, 2010 at 3:41 am “What would be the effect on sea level if the density of the matter below the crust varies across the oceans? I tend to think it will be fairly negligible. Several milimeters, rather than several Cms.”
Well, the scale is on the chart, and it goes from -120metres to +100 metres. There are about 200 metres in ‘height’ potential therefore between the Maldives and Indonesia. It’s no wonder therefore that the fastest sea level drop in the world is in the Indian ocean (around 90E 15S, -20mm per year measured by satellite altimetry) and the fastest sea level rise is near Indonesia and the Philippines (around 130E 10N, +20 mm per year). These points may be a couple of thousand miles apart, but there is an effective potential gradient of 200 metres over that distance. So, all other things being equal, water should be slowly emptying out of the Indian ocean through Indonesia into the Pacific. And that’s going to keep on going, I suggest, for a long time – until equilibrium is attained or the gravitational anomaly varies.
To my mind, this gravitational anomaly chart answers one of the mysteries as to why the sea levels in the northern Indian ocean have been declining at the same rate as the western Pacific are rising. It also makes the issue of possible sea level rise around the Maldives look more like a joke (they have been in decline for decades), and the actual sea level rise in the Pacific islands look to be a natural phenomenon that we can do nothing about.
The experiment is quoted as precise to to 0.00000000000098 m/s/s. If that is the case, how are external gravity sources controlled out? Curious Buffoon is Curious.
Nice art. I personally like the large fish off the coast of southern Africa.
So we have two competing explanations of what the colors mean:
AleaJactaEst says:
June 29, 2010 at 12:27 am
“Areas of the earth’s crust where seafloor is being actively created (seafloor rock generally has a higher density than continental rock) show as anomalous highs (over Iceland and tracking the Atlantic tectonic spreading ridge to the south) as well as over the area of Indonesia/Malaysia/heading towards New Zealand which is also tectonically active with creation of new seafloor.
Density lows can bee seen to correlate with sedimentary basins (sedimentary rocks have lower densities than seafloor rock), the very large one south of India being a classic case. The one under the Great Lakes/Souther Canada is also a sedimentary basin.”
vs.
Colin W says:
June 29, 2010 at 2:39 am
“@Policyguy: The map is showing the change in height needed to maintain the same potential energy. So comparing two people of the same mass, one goes to Sri Lanka and another to Iceland. Because the gravity is stronger over Sri Lanka (denser/thicker rock) that person would have to move closer to the centre of the earth relative to the person in Iceland (less dense/thinner rock) to have the same potential energy.
So any water at Sri Lanka with higher potential energy than the surrounding water would move away, like a ball rolling, or rivers flowing, downhill, so we would expect deeper water at Iceland (ie water further from the centre of the Earth) than at Sri Lanka.
Excuse my rusty Physics”
So then the question is; does that mean that warm ocean water roll downhill to the polar regions; or is it more complex than that as the sea surfgace has alrady “levelled out geoidally, exccept for wind tide and current.
And so what is it with all those dark olive areas; that aren’t any of the colors on the scale; what the heck are those ?
Can Michael Mann, now use this geoidometer as a proxy for Temperature anomalies; it would seem to be as well connected as tree rings ?
Interesting, but not new. I have a photograph of the Goddard Space Flight Center Detailed Gravimetric Geoid on display in the Smithsonian in 2003. Less detailed,
and much less colorful, but roughly the same information.
Kieth Minto:
Keith Minto:
There is no such thing as centrifugal force, there is a force called cetripetal force caused by rotation at least according to my physics IV professor who threatened me with an F if I used that term again. Gravity, itself, is not a force, per se, but a curvature of space caused by the presence of mass. Where gravity is “stronger” there is more mass and vice versa. The map shows where mass is concentrated and the gravitational differences are apparently miniscule.
Buffoon says: June 29, 2010 at 9:13 am “The experiment is quoted as precise to to 0.00000000000098 m/s/s. If that is the case, how are external gravity sources controlled out?”
The BBC report says:
“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.”
That’s highly misleading as it’s a measure of resolution of the sensors individually and not related to the accuracy of the overall instrument. It’s not ‘precise’ or ‘accurate’ to anything like that. Typical ‘gee-whizz’ journalism to use a big number that is meaningless in the context of mission accuracy. By the time the measurements are combined on 3 axes and compensations made for perturbations the mission objective attained is a more believable accuracy of one part per million, i.e. 1 x 10^-5 m/s^2.
Check out ESA’s own useful brochure on the satellite, instruments, and mission objectives:
http://esamultimedia.esa.int/docs/BR209web.pdf
The geoid seems to be a fairly difficult concept for people to grasp, which is understandable because it is a bit counterintuitive. To simplify somewhat, it is an idealized and imaginary approximation of what the surface of the liquid water on the planet would display if all influences other than gravitational anomalies were removed and all land masses were 100% permeable to the water. The blue areas are high gravity and the red are low gravity.
It highlights what a meaningless concept Global Mean Sea Level really is. If you wanted to build a vehicle capable of traversing the world’s oceans exactly at GMSL it would have to be a “Thunderbirds” special which could morph from a submarine able to handle depths greater than a hundred meters to an airplane able to fly at over a hundred meters altitude.
There is a pretty good discussion of the geoid and the reference ellipsoid in the data products handbook for JASON 2
http://www.osdpd.noaa.gov/ml/ocean/J2_handbook_v1-3_no_rev.pdf
And though I usually avoid referencing Wikipedia, their article on the geoid isn’t terrible
http://en.wikipedia.org/wiki/Geoid
Oops, I got the color relationships to gravity backwards in my comment above, here is a depiction scaled to gravity strength not elevation
http://en.wikipedia.org/wiki/File:Geoids_sm.jpg
Has there been any peer reviewed papers come out yet that say CO2 is causing heavier than normal gravity?
Any bets on how soon there will be a paper coming out that says short obese people aren’t caused by overeating but because heavy doses of CO2 are causing heavier than normal gravity and it’s pushing people down to the ground?
wink wink
I think it would be at high noon with a solar eclipse…?
—
I’m not certain I understand their description of what I’m looking at. The darkest blue areas are called the lowest because that’s where gravity is the weakest?
That’s more understandable than saying this is how the terrain would have to be in order for you to feel as though you were walking along level ground. BBC’s Bergen concocted an artificial representation of an effect that would be a attributable to the anomaly whereas I think most people would rather just see the representation of the anomaly data directly per your wiki link.
Jim G says: “There is no such thing as centrifugal force.”
Would you accept “Centrifugal Inertial Reaction Force”?
To understand that figure, you need to understand what an ellipsoid and a geoid are.
An ellipsoid is a simple surface that approximates where sea level is (or would be if the continents were completely permeable). It is essentially a squashed sphere- the pole to pole diameter is slightly shorter than the diameter at the equator.
Ellipsoids are very important in mapmaking- every map uses some reference ellipsoid.
A geoid, on the other hand, is a much more complex and accurate representation of where sea level is (or would be). The geoid represents a surface where the gravitational acceleration is everywhere equal; that’s where sea level would be if there were no other effects but gravity. (Geoids aren’t generally used in mapmaking because the math gets too complicated).
What the figure shows is the difference between the simple ellipsoid and the more accurate (and complex) geoid. For example, where the map is colored dark blue, the surface of the geoid is 100 or so meters lower (ie, closer to the center of the earth) than the surface of the ellipsoid. Where the map is colored orange, the surface of the geoid is 100 or so meters higher (ie, further from the center of the earth) than the surface of the ellipsoid.
The difference between the two “oids” is a FUNCTION of the difference in the “strength of gravity” at different places on the earth, but it’s not really a gravity map- because of the shape of the ellipsoid, a spot near the pole and a spot near the equator might have the same strength of gravity, but have different deviations from the ellipsoid.
Forgive me if I have this messed up, but my take is that the levels -100/+80 meters describe corrections needed to an earthlike spheroidal shape to provide equal gravitational acceleration at a particular location and have nothing to do directly with where the surface of the earth/ocean might be.
My earlier concern over the local differences was directed to the use of satellite telemetry for sensing surface elevations/sea levels. The accuracy of this process would depend mightily on correcting for geometry and strengths of the anomalies indicated on this wonderful map – this geometry and these strengths affecting orbit geometry.
It also appears that the center of mass of the earth oscillates with respect to surface “fixes.”
Which of course makes me wonder when the “sea levels are rising” gurus submit for publication and include their telemetry based appraisals, do the publications run their stuff past someone who really understands the issues we’ve been tossing around here? Or maybe just another climate guy who works with same stuff?
It seems this was one of the weightiest of the McKittrick McIintyre discoveries – noone on the “team” was really sharp on statistics. It’s clear that divining relative surface elevations is not simple.
Not too long ago, the Smithsonian service which provides center of mass data to the world was working on resolutions to 3mm. Maybe they’ve got it down to .3mm now.
Help anyone?
Thanks Chris V. Much better than my shot at it.
Mike M:
I looked it up on wikipedia, and we all know how accurate that is, and it referred to centrifugal force as a “ficticious” force which is pretty much what my old physics prof alluded to. Yes, your definition fits the theory of it being an “assumed” force in the opposite direction of the centripetal force, if I understand this correctly.
7. Gravity changes can betray magma movements under volcanoes
This technique would be useful around very active and explosive eruption type of volcanoes like at Kamchatka Peninsula which has a history of sudden undetected eruptions with little warning . I notice this area is shown in orange and yellow colour on the map.
It so happens that there are currently 5 volcanoes in avaiation code yellow or orange . Last year in April /May there were 7 in this danger zone at the same time .
Jim G says:
June 29, 2010 at 10:47 am
Kieth Minto:
Keith Minto:
There is no such thing as centrifugal force, there is a force called cetripetal force caused by rotation at least according to my physics IV professor who threatened me with an F if I used that term again. Gravity, itself, is not a force, per se, but a curvature of space caused by the presence of mass. Where gravity is “stronger” there is more mass and vice versa. The map shows where mass is concentrated and the gravitational differences are apparently miniscule.
So then, is that why my centripetal dollars keep getting drawn towards D.C.?
😉
Cryosat-2 focuses on ice target
The first data from the European spacecraft has been presented at an Earth observation meeting in Norway.
The information clearly shows Cryosat has the required sensitivity to assess the state of Antarctic and Arctic ice, according to its lead scientist.
http://news.bbc.co.uk/1/hi/science_and_environment/10450425.stm
Esa expects to get at least five years of mission life out of the satellite. The spacecraft is mid-way through a six-month commissioning phase. Once this is complete, calibrated and validated data will be delivered to the scientific community.
899 says:
“So then, is that why my centripetal dollars keep getting drawn towards D.C.?”
No, that is a true force! Unlike the oft quoted “gravity is because the earth sucks” Washington DC really does! And it sucks in money from anywhere and anyone it can. When it can’t get anymore it simply has the “privately owned” federal reserve create more out of thin air, an amazing violation of the rule of conservation of matter/energy!
Always thought there was something more Grounded aboot the South Island of new Zealand….now we have the mappy thingo to prove it….
Yes, the blue area around Sri Lanka indicates less gravity than other areas, especially orange/red areas. Another way to think of it is that the greater mass concentration of an area pulls the ocean water towards it, building it up, producing higher altitudes in the geoid. Low gravity areas (Sri Lanka) have water pulled away from it, producing low altitudes.
Dave Wendt said at 10:54 am
It highlights what a meaningless concept Global Mean Sea Level really is.
That summed it up very nicely and points to another fact that some people, including some scientists, do not seam to realize or grasp (at least not openly) and that is – with current technology (or anything in the foreseeable future) we can not calculate the average height of the planets oceans, nor the density, nor the temperature. The same thing holds true for the plants atmosphere, including but not limited to CO2 density. Why? Because we can not measure any of it – accurately. To have any degree of “accuracy” we would have to take our measurement of ALL factors, everywhere – almost simultaneously. And THAT reading on to its own would be meaningless as we have no historical data of comparable accuracy and due to the ever intersecting short, medium, long and extra long weather cycles we would need a couple hundred years history of such data to make any reasonable forecast of….. hmm, sounds like we a multi-million dollar grant.
If gravity has effects on the actual surfaces of the oceans (higher/ lower) as they move around, would it also effect the atmosphere itself, as it moves around? I’m probably not expressing this very well, but I am thinking that the atmosphere’s shape would be more amoeba-like, rather than the ball (ellipsoid) shape we generally assume.
>j ferguson says:
>June 29, 2010 at 4:12 am
>If sea level changes are in mm increments, wouldn’t they be lost in terms of reliable >measureability in the local conditions and “oscillations” discussed above including some >very informative comments?
Scotland is rising at a rate of 3mm per year and England is sinking at a rate of 2mm per year. Whether or not the ocean is falling or rising depends upon where on the island you live.
Agile Aspect says:
June 29, 2010 at 4:32 pm
>j ferguson says:
>June 29, 2010 at 4:12 am
>If sea level changes are in mm increments, wouldn’t they be lost in terms of reliable >measureability in the local conditions and “oscillations” discussed above including some >very informative comments?
Scotland is rising at a rate of 3mm per year and England is sinking at a rate of 2mm per year. Whether or not the ocean is falling or rising depends upon where on the island you live.
All those fat Sassenachs, then?
😉
Jim Barker says:
June 29, 2010 at 4:23 pm
If gravity has effects on the actual surfaces of the oceans (higher/ lower) as they move around, would it also effect the atmosphere itself, as it moves around? I’m probably not expressing this very well, but I am thinking that the atmosphere’s shape would be more amoeba-like, rather than the ball (ellipsoid) shape we generally assume.
Wow! Now there’s a thought: The Earth as ‘amoeba.’
No wonder those space aliens look at us all kinda weird like: “Yo! Dudes! How the heck can you stand to live like that?
“Don’t you get all ‘weirded-out’ sliming from place-to-place?”
🙂
Milwaukee Bob says:
June 29, 2010 at 4:00 pm
Dave Wendt said at 10:54 am
It highlights what a meaningless concept Global Mean Sea Level really is.
That summed it up very nicely and points to another fact that some people, including some scientists, do not seam to realize or grasp (at least not openly) and that is – with current technology (or anything in the foreseeable future) we can not calculate the average height of the planets oceans, nor the density, nor the temperature. The same thing holds true for the plants atmosphere, including but not limited to CO2 density. Why? Because we can not measure any of it – accurately. To have any degree of “accuracy” we would have to take our measurement of ALL factors, everywhere – almost simultaneously. And THAT reading on to its own would be meaningless as we have no historical data of comparable accuracy and due to the ever intersecting short, medium, long and extra long weather cycles we would need a couple hundred years history of such data to make any reasonable forecast of….. hmm, sounds like we a multi-million dollar grant.
Well, you know? Your thoughts just ain’t gonna cut it for the ones who’ve invested BILLIONS OF MOOLAH to get the rest of us to buy into their ‘carbon-come’ scheme.
You see? They’ve got it down flat and simple-like so that the hoi polloi (the commoners) understand the ‘simplicity’ of having to work their miserable lives to the bone and die soon enough so that the new-born get inculcated into the scheme seamlessly.
If you don’t watch out, they’ll send in the carbon-come Stasi to snuff your miserable existence so that you don’t get the chance to poison the well with Real Knowledge®.
The Goce satellite at an altitude of 255k is lower than the Grace satellite pair discussed in Willis’ article http://wattsupwiththat.com/2010/05/23/on-being-the-wrong-size/ . They are at 450-500km and spaced 220km apart and presumably do a similar job to Goce.
My concern with both of these systems, but especially Goce is that they are catching variable amounts of atmosphere on their journey and both rely on an accelerometer to measure gravity. I imagine the atmosphere at that altitude would be variable in density and introduce a spurious signal.
Jim G says:
June 29, 2010 at 3:09 pm
‘899 says:
“So then, is that why my centripetal dollars keep getting drawn towards D.C.?”
No, that is a true force! Unlike the oft quoted “gravity is because the earth sucks” Washington DC really does! And it sucks in money from anywhere and anyone it can. When it can’t get anymore it simply has the “privately owned” federal reserve create more out of thin air, an amazing violation of the rule of conservation of matter/energy!’
I was once told there was only one printed dollar, the rest is done with smoke and mirrors.
Does this explain levitating Bhuddas in India? 🙂
Interesting. The Andes mountains seem to have the opposite effect of the Himalayas. The Himalayas have the same effect as some of the deep ocean trenches. The mid-Atlantic ridge has almost no impact at all. Sri Lanka is the center of a huge anomoly despite being geologically rather dull.
Or maybe that instrument isn’t nearly as astonishingly sensitive as it would need to be to produce such a map reliably.
No one has actually explained the map in a clear way (shame on the confused BBC article).
There are those who have said that blue=lower density, red higher, but I find the opposite. Please correct me where I am going wrong!
To explain (for my own sanity, if not for others):
The Earth is an ellipsoid (a sphere squashed at the top and bottom, which is squashed again at on either side of the equator), so standing on the equator I will experience a greater gravitational force than at the poles.
At the poles I am closer to the centre of the Earth than at the equator, so some of the mass of the earth is ‘above’ me at my distance from the centre, hence a lower gravitational force.
To find the points of equal gravitational force, I would have to move into the earth at the equator (more blue), so more of the Earth’s mass is ‘above’ me, and rise above the earth at the poles (more red), so more of the Earth’s mass is below me, until I experienced the same gravitational force.
Now, since we know the Earth is an ellipsoid, it would not be useful to show the poles as red and equator blue, so this difference is removed from the map, so that the map is just showing mass differences over the planet. A uniform density would show the whole Earth as green.
At Sri Lanka the gravitational force is higher still (greater mass), so I would have to move further into the earth to compensate (more blue). At Iceland the gravitational force is lower (less mass), so I would have to move higher to compensate (more red).
This is the shape that water would settle at if it could move freely through ‘ghost’ rock and into a ‘ghost’ Earth.
Phew.
Ok, I have thought about it a bit more and now agree that blue=lower density, red=higher.
My corrected explanation is:
The Earth is an ellipsoid (a sphere squashed at the top and bottom, which is squashed again at on either side of the equator), so standing on the equator I will experience a lower gravitational force than at the poles because I am further away from the Earth’s mass. At the poles I am closer to the Earth’s mass, hence a higher gravitational force.
To find the points of equal gravitational force, at the equator I would have to move into the Earth so I am closer to the centre of the Earth (blue), but balanced with a reduced Earth’s mass as some of it is now above me. At the poles I would have to move away from the Earth to reduce the gravitational force (red).
Now, since we know the Earth is an ellipsoid, it would not be useful to show the poles as red and equator blue, so this difference is removed from the map, so that the map is just showing mass differences over the planet. A uniform density would show the whole Earth as green.
At Sri Lanka the lower density means that I would have to move into the earth to compensate (blue). At Iceland the higher density means I would have to move higher to compensate (red).
Colin W says:
June 30, 2010 at 6:17 am
[–snip for brevity–] At Sri Lanka the lower density means that I would have to move into the earth to compensate (blue). At Iceland the higher density means I would have to move higher to compensate (red).
Gee, Colin, I consider that you’ve figured out why the inhabitants of Sri Lanka always seem to be high, and the Icelanders always seem to be so ‘down to Earth’ …
😉
Yes; and considering how they believe that the whole world revolves around them, it also might explain why we appear to be going in circles? Maybe it has something to do with a political frame of inertial reference?
Just wait for successive versions of the maps and the explanations for change. Apart from the abovementioned guidance of Cruise missiles which used to rely on a selected geiod, the best we can expect from these satellites is pretty images at quite coarse resolution. I suspect that the limiting factor, also noted above, will be confusion of velocity change caused by tiny changes in atmospheric composition. There’s also a problem that Earth is plastic and its shape is changed by tides. Might impact on the necessary measurement of satellite altitudes.
It has always been difficult to measure differences in gravity. The instruments of old were hand made, fragile, horribly expensive, needed to be upright at all times, needed quite a time to stabilise at each new station and were usually transported like passengers strapped into vacant airline seats, sometimes under the name “G. Meter”. The sensitivity was often limiting and it was a good deal better than these satellites give.
BTW, I have to disagree with wayne Job
June 29, 2010 at 4:51 am when he says that gravity measurements were made from sensors under aircraft in the 1960s. Magnetism was measured, plus a variety of electrical methods where signals of various frequencies were sent to earth and responses picked up by drogues on cables – several variations, but that’s what he might have seen.
That’s geoid.