[insert your own caption here]
Vancouver Sun/Reuters
ANTARCTICA — Sea levels will rise at varying rates around the world because of a quirk of the earth’s gravity linked to global warming, a leading glaciologist said.
“Everyone thinks sea level rises the same around the world,” David Vaughan, of the British Antarctic Survey, said on Tuesday at the Rothera Base on the Antarctic Peninsula. “But it doesn’t”.
Rises could vary by tens of centimetres from region to region if seas gained by an average of one metre by 2100 as temperatures rise, he said. Worst-affected nations would have to budget billions of dollars more than others on coastal defences.
Vaughan said big ice sheets on Antarctica and on Greenland have a gravitational pull that lifts the seas around them — water levels around Antarctica, for instance, are higher than if the frozen continent were an open ocean.
As ice thaws, Antarctica would get smaller and its gravitational tug would diminish.
UPDATE: With the humorous photo I chose, I may have unintentionally implied that the gravitational effect described is not true. It is and the simplest physics. The likely magnitude and the suggestion of Antarctica melting are the main issues. Here is a paper from MIT that describes Earth’s gravity anomaly and sea level differences. – Anthony
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Furthermore, if the world slows down due to the increased diameter from water volume increase, the days would get hotter and the nights colder…. OMG, we have a new catastrophic positive feedback loop!!!!
[insert your own caption here]
Han, my boy, you disappoint me . . .
MartinGAtkins (07:51:43) :
Gravitational force is weaker at the equator due to equatorial bulge, (with is caused by centrifugal force), which causes objects at the equator to be farther from the planet’s center than objects at the poles.
force due to gravitational attraction between two bodies varies inversely with the square of the distance between them.
Ric Werme (04:09:10) :
“Hmm. One of our icy issues of our time is water lubricating glaciers causing them to surge forward and do bad things. So, as ice in Antarctica gets more massive, it will attract water to the coastline and lift the glacier there. I never realized ice could lift itself by its bootstraps. Or that it has bootstraps!
In the extreme, this could be another tipping point – ice attracts more water, the additional mass attracts still more water, and before you know it all the water on the planet will be on Antarctica.”
Great stuff. Have we found another form of positive feedback; this time it’s gravity? “We’re all doomed!” Negative feedback has been made illegal, because our glorious leaders think it reflects badly on them.
If only Max Escher could have been around to do the artwork for the AGW crowd.
Richard111 (05:16:03) :
No, your spelling is bad. It is a “Cat Ass Trophy”
Ferdinand (00:44:55) :
Not just 50 years ago!
In 1867 Victorian scientists discussed the likely effect that unloading of ice from Antarctica would have on the surface of the global ocean. In this paper by James Croll, published in the Transactions of the Geological Society of Glasgow, (see page 194 inside pdf) he estimates that the centre of gravity of the whole planet would be altered by loss of ice from the Antarctica.
He suggests that this change would alter the geoid, in particular the height of the water surface of the northern hemisphere Arctic Ocean above the ocean floor, and lead to a rise in the sea level distributed across the whole of the northern hemisphere. This rise is in addition to the change in volume due to the extra water derived from the melting of the Antarctic ice.
From Croll J. 1867 – On the Change in Obliquity of the Ecliptic; its Influence on the Climate of the Polar Regions, and the Level of the Sea. Trans Geol Soc Glasgow Session 1866-67 p194:-
If 470 feet were melted off-and this is by no means an extravagant supposition, when we reflect that for every 18 pounds of ice presently melted an additional pound or two pounds, or perhaps more, would then be melted, and that for many ages in succession-the water thus produced from the melted ice would raise the level of the sea 18 feet 5 inches. The removal of the 470 feet of solid ice-which must be but a very small fraction of the total quantity of ice lying upon the antarctic continent would shift the earth’s centre of gravity about 7 feet to the north of its present position. The shifting of the centre of gravity would cause the sea to sink on the southern hemisphere and rise on the northern.* And the quantity of water thus transferred from the southern hemisphere to the northern, would carry the centre of gravity about 1 foot further, and thus give a total displacement of the centre to the extent of about 8 feet. The sea would therefore rise about 8 feet at the North Pole, and in the latitude of Glasgow about 6 feet 7 inches. This, added to the rise of 18 feet 5 inches, occasioned by the melting of the ice, would give 25 feet as the total rise in the latitude of Scotland 11,700 years ago.
pdf file
Wondering Aloud (09:42:30) :
MartinGAtkins
“BTW, isn’t there more gravitational pull at the poles because the Earth bulges at the equator, therefore you are further from the center of the Earth.”
In your reply you said
“No because maximum gravitational force is at the surface and not the center. This is because the maximum mass is between you and the other side of the planet.”
I’m pretty sure this is incorrect the controlling factor is that at the pole you are closer to the center of mass therefore the force of gravity is greater. The amount of mass involved and it’s position relative to you is not different. Additionally the rotation of the earth gives you some momentum that tends to reduce the net force of gravity, this reduction is greatest at the equator. In short you weigh more at the poles.
The last is correct, the recommended expression is as follows:
gt = 978.0327(1.0+0.0053024 sin²(θ) – 0.0000058 sin²(2θ))
so at the poles it’s 983.2186
Philip Mulholland (14:35:04) :
We can suppose that if the Antactic ice melts, the Artic ice, Greenland’s ice and as well as all the mountain ice must also melt. The release of pressure on the crust from the redistribution of the mass and the slowing down of the rotational speed of the earth will surely make that distribution more uniform.
I don’t think in 1867 they had a whole and precise picture of the planet… we still don’t!!
Anthony – Many thanks for that update. Most enlightening.
The problem I see isn’t with the science per se, but with the way it seems so many scientists try to link everything to AGW. Once AGW is debunked, all science will likely suffer from a backlash.
An interesting twist from a science view is that Swedish scientist Celsius actually is more renowned for his participation in a French led expedition in northern Sweden to prove Newtons theory about the equatorial bulge, rather than his thermometer. Here’s a link about him:
http://www.astro.uu.se/history/Celsius_eng.html
Oh and my team won again!
Time for the chubby feline to cut back on the Meow Mix.
I would recommend a 42D. The rib cage measurement seems slightly larger than the typical proportion so I recommend the larger band size but stick to a D cup with side gathering capability. I would also choose a padded shoulder strap. The larger measurement bra can dig into your shoulders without that extra wide protection. Three hooks would be a must.
My former life. Department Head in the Lingerie Department for The Broadway Clothing Store Chain. It was my job to solve the brazier problems of all the older ladies who came in to be measured.
Are You Being Served?
Pamela G
Let’s not start the personals thing again mmmkay?
Caption for cat pic…
“Get ready, kitty… when I pull this plug anything could happen…”
Jeez, jeez, lost your funny bone? It was a parody of the CAT! You know. The cat in the photo. See photo in this post. Prepared and presented to us by the blog owner. To give us a smile. A bit of levity. To turn us from a sour puss into a happy cat. God knows the amount of testosterone, chest thumping, tree branch rattling, and head butting here can be overdone on a regular basis. Granted in a cerebral way, but nonetheless…
No Pamela, apparently you have lost yours. We are sooo done.
And I had such high hopes…wimper.
Phil. (14:42:41) :
If you were at the center of the mass then you would be weightless (and dead). This is because the mass of the planet is surrounding you and attracting you more or less equally in all direction. It’s true that the core is denser but the earth is not a perfect sphere. It’s wider at the equator and so has more mass in that plane. It’s the rotation of the earth that makes you less heavy not the distance from the center of the mass. Remember the question was.
“BTW, isn’t there more gravitational pull at the poles because the Earth bulges at the equator, therefore you are further from the center of the Earth.”
I maintain that the answer is no because there is less mass between you and the other side of the earth at the poles than there is at the equator.
Down with gravity, up with levity.
Philip Mulholland (14:35:04) :
Thanks for the update! Didn’t know it was that long ago that the scientists came to the same conclusion… Anyway an interesting extra…
MartinGAtkins (18:09:51)
Sorry Martin the mass between you and the other side of the earth is the same in either case, and it is distance between your center of mass and that of the earth that rules here. Phil posted just after me above with the actual accepted values for the equator and poles.
However, as I mentioned the rotation of the earth not only creates the bulge it is part of the difference in the net force.
Wondering Aloud (05:15:02) :
Sorry Wondering, but you are in error. It’s true that that the center of gravity is at the center of the earth but that is only because it is the center of the mass of your body and all the mass between you and the other side of the earth. Now let me remind you of the original question.
“BTW, isn’t there more gravitational pull at the poles because the Earth bulges at the equator, therefore you are further from the center of the Earth.”
He is not asking if you would weigh less at the equator because of the rotation of the earth. If he had so, my answer would be yes because the rotation of the earth has the in effect of moving us in a straight line through space but on a curved body. The curvature would appear to fall away from us because we are traveling in a straight line through space. The gravity of the planet counteracts this tendency but the two forces compete, with the net effect being you would weigh less.
Now we have that out of the way we can get back to the original question which deals only with the effects of gravity and the shape of the planet.
Gravity is the product of the two bodies masses. If you were in space then it would be the entire mass of the earth that would be the attractor. You would be attracted to the center of earth because that is the maximum point of it’s diameter in relation to you and so it has the maximum mass and gravitational pull.
It’s maximum mass is not a straight line from you to the center of earth. It is a straight line from you to the opposite side of the earth.
It’s the same at the surface. You must take into account the gravitational attraction of the mass beyond the gravitational center.
Due to the rotation of the earth it is slightly oblate and so is wider at the equator than it is at the poles. It therefore has more mass between the surfaces of equator than it does between the surfaces of the poles.
If you could take a core drilling through the entire planet, then the equatorial core would be longer than the polar core. So which one would have the most mass?
Even if you only took a core drilling to the center, the equatorial core would be longer than the polar core and so would have more mass.
Thanks Anthony. Is it Al’s preincarnation?
Tom Bakewell (09:14:23) :
Ice sheets and gravity are discussed in “Polar Wander, Sea-Level Variations and Ice Age Cycles”
http://www.gps.caltech.edu/~jkirschvink/pdfs/SeaLeveliitpw.pdf (6 pages + refs)
What are the conclusions? Heavier or lighter at the poles ignoring centrifugal force and not ignoring?
Is the planet cooling? I believe it is with little to zero ocean stored heat. That would negate any relevance melting has to present times wouldn’t it?
The following may be of interest but don’t answer my question(s)-
http://www.gps.caltech.edu/~jkirschvink/pdfs/SeaLeveliitpw.pdf
A sea level test for inertial interchange true polar wander events
http://www.ias.ac.in/currsci/oct/articles7.htm
True polar wander and marine transgressions
http://books.google.com/books?id=ez5LlQZ3MfAC&printsec=frontcover#PPR9,M1
Global Dynamics of the Earth