Why sea level rise will be a good thing.

Surface Detail wrote:

Tim the plumber wrote:

Surface Detail wrote:

Tim the plumber wrote:

Surface Detail wrote:

Tim the plumber wrote:

Surface Detail wrote:

Yes, melting ice from the poles would indeed slow the Earth's rotation by a tiny amount. But given the lack of any references or calculations, I'm going to assume that the tenths of a mm accuracy is just your usual bullshitting.

http://www.iflscience.com/environment/rising-sea-levels-shown-actually-slow-down-earths-rotation-0/

I would have to go and buy a scientific calculator to do it myself.

The most accurate clock ever built only loses one second every 15 billion years. Scientists have a set a new record in accurate timekeeping, creating an atomic clock that won't lose or gain a second in 15 billion years — a time span greater than the estimated age of the Universe.22 Apr 2015

Given that the precision would be better than a trillionth of the rate of rotation and th eeffect of an aditional mm is in the order of a billionth of the radius of the world it should be far more accurate than 0.01mm.

You are, of course, ignoring that fact that the speed of the Earth's rotation is affected by other factors in addition to the melting of the ice caps. This is why you cannot use changes in the Earth's rotation speed to accurately measure sea level changes.

What other factors?

Which of these factors cannot be easily modeled?

Tidal effects, continental drift, earthquakes, magma movements, for example.

Of these, I'd guess that tidal effects and, perhaps, continental drift may be modellable. Earthquakes and magma movements less so. If you're that interested, why not do a literature search and so what you can find?

Given that I am expected to believe that the best way to measure the ice mass changes of Greenland is by the deviation of satellites going over there the laval flows which do not significantly effect the mass distribution of the earth over decades would be very easy to measure with surface gravitometers.

Tidal effects would of course be inconsequential. What happened last year happened this so no change there.

Nope, you have yet to point out why there is any trouble with day length as a measure of distribution of mass between poles and general sea level.

You're the one who is proposing the technique, so you tell me.

How much would you expect a rising sea level of about 3.4 mm (some from polar ice melting and some from thermal expansion of seawater) to slow the Earth's rotation? Over what duration would this be measurable? How would it compare to the continual slowing of the Earth's rotation by tidal effects? What about continents drifting towards or away from the poles? What would their effect be?

Tim the plumber wrote:
OK,

I = (mr^2)/2

m = 5.97 x 10^24 Kg

r = 6371 Km.

For a hollow sphere of negligabe guage;

I = (2mr^2) / 3

m = 1mm of sea water over the whole earth (I'm ignoring the distribution of the land for now but using the area of the oceans. If you want to do a better job feel free.)

So that's 360 billion tonnes per mm. So 360 x 10^12kg

so; I shell / I whole earth = (4/3) x Mass (shell) / Mass (earth)

360/5.97 x 10^-12 x 4/3 -----> 80.4 x 10 *-12

x 3600 x 24 x 365 ( seconds in a year) = 32 x10^6

So about 2 millionths of a second per year per mm rise in sea level. Well within the precision of those fancy atomic clocks.

Hang on, my maths is very rusty for this sort of thing, it's 30 years since I did any of this....

It should be initial moment over initial moment plus the new shell. My calculator is not up to that but I think the result will come out to be very similar...

I expect the diffeerence of a couple of cm in the location of continents to be utterly trivial and the changes in altitude in mountain ranges small as well but either would be simple to work out.

Surface Detail wrote:
Hmm, after doing a bit more research, it seems we are both barking up the wrong tree, and our model was far too simple. It appears that melting ice from the poles doesn't lengthen the day, instead it tends to shorten the day! Why? As far as I can tell, it's because the Earth "rebounds" where the weight of ice is taken off it at the poles and sinks a tiny bit around the equator under the additional weight of water. The net effect is that the Earth remains the same shape, but the heavy rock is shifted down at the equator and up at the poles, giving an Earth with a lower, rather than higher, moment of inertia.

It all looks fiendishly complicated, but here is as good a place to start as any, if you're still interested: Earth May Spin Faster as Glaciers Melt

Jerry X. Mitrovica seems to be the guy who's most knowledgeable on the topic. You might give him a google!

Surface Detail wrote:
Hmm, after doing a bit more research, it seems we are both barking up the wrong tree, and our model was far too simple. It appears that melting ice from the poles doesn't lengthen the day, instead it tends to shorten the day! Why? As far as I can tell, it's because the Earth "rebounds" where the weight of ice is taken off it at the poles and sinks a tiny bit around the equator under the additional weight of water. The net effect is that the Earth remains the same shape, but the heavy rock is shifted down at the equator and up at the poles, giving an Earth with a lower, rather than higher, moment of inertia.

It all looks fiendishly complicated, but here is as good a place to start as any, if you're still interested: Earth May Spin Faster as Glaciers Melt

Jerry X. Mitrovica seems to be the guy who's most knowledgeable on the topic. You might give him a google!

Previous research has found that melting glaciers triggered by global warming helped cause a significant amount of global sea-level rise in the 20th century. In theory, rising sea levels — once estimated to be climbing at a rate of about 0.06 to 0.08 inches (1.5 to 2 millimeters) per year — should also have slightly shifted Earth's axis and increased the rate at which the planet spins.

When polar ice caps melt, they remove weight off underlying rock, which then rebounds upward. This makes the poles less flat and the planet more round overall. This should in turn cause Earth to tilt a bit and spin more quickly.

Tim the plumber wrote:

Surface Detail wrote:
Hmm, after doing a bit more research, it seems we are both barking up the wrong tree, and our model was far too simple. It appears that melting ice from the poles doesn't lengthen the day, instead it tends to shorten the day! Why? As far as I can tell, it's because the Earth "rebounds" where the weight of ice is taken off it at the poles and sinks a tiny bit around the equator under the additional weight of water. The net effect is that the Earth remains the same shape, but the heavy rock is shifted down at the equator and up at the poles, giving an Earth with a lower, rather than higher, moment of inertia.

It all looks fiendishly complicated, but here is as good a place to start as any, if you're still interested: Earth May Spin Faster as Glaciers Melt

Jerry X. Mitrovica seems to be the guy who's most knowledgeable on the topic. You might give him a google!

Previous research has found that melting glaciers triggered by global warming helped cause a significant amount of global sea-level rise in the 20th century. In theory, rising sea levels — once estimated to be climbing at a rate of about 0.06 to 0.08 inches (1.5 to 2 millimeters) per year — should also have slightly shifted Earth's axis and increased the rate at which the planet spins.

When polar ice caps melt, they remove weight off underlying rock, which then rebounds upward. This makes the poles less flat and the planet more round overall. This should in turn cause Earth to tilt a bit and spin more quickly.

This is a lie. Plain and simple.

The distance away from the axis of ratation of mass at the equator will rise by the introduction of more water which is less dense than rock. The rise at the equator will be greater than the slight, and long time in happening, rise at the poles of rock which will have zero impact on the speed of rotation of the earth as it will not change the distance from the axis of rotation.

Again I point out how far some people will go to try to cover up the facts.

Surface Detail wrote:

Tim the plumber wrote:

Surface Detail wrote:
Hmm, after doing a bit more research, it seems we are both barking up the wrong tree, and our model was far too simple. It appears that melting ice from the poles doesn't lengthen the day, instead it tends to shorten the day! Why? As far as I can tell, it's because the Earth "rebounds" where the weight of ice is taken off it at the poles and sinks a tiny bit around the equator under the additional weight of water. The net effect is that the Earth remains the same shape, but the heavy rock is shifted down at the equator and up at the poles, giving an Earth with a lower, rather than higher, moment of inertia.

It all looks fiendishly complicated, but here is as good a place to start as any, if you're still interested: Earth May Spin Faster as Glaciers Melt

Jerry X. Mitrovica seems to be the guy who's most knowledgeable on the topic. You might give him a google!

Previous research has found that melting glaciers triggered by global warming helped cause a significant amount of global sea-level rise in the 20th century. In theory, rising sea levels — once estimated to be climbing at a rate of about 0.06 to 0.08 inches (1.5 to 2 millimeters) per year — should also have slightly shifted Earth's axis and increased the rate at which the planet spins.

When polar ice caps melt, they remove weight off underlying rock, which then rebounds upward. This makes the poles less flat and the planet more round overall. This should in turn cause Earth to tilt a bit and spin more quickly.

This is a lie. Plain and simple.

The distance away from the axis of ratation of mass at the equator will rise by the introduction of more water which is less dense than rock. The rise at the equator will be greater than the slight, and long time in happening, rise at the poles of rock which will have zero impact on the speed of rotation of the earth as it will not change the distance from the axis of rotation.

Again I point out how far some people will go to try to cover up the facts.

I'm not lying or trying to cover up facts. I'm simply trying to get a handle on what is a much more complex issue than you seem to realise (or I did).

It is undisputed that, in the long term, the Earth's rotation is gradually slowing as its angular momentum is transferred to the moon. However, there are all sorts of shorter term effects that sometimes slow the earth even more and sometimes actually make it spin faster. Changing ocean currents, expanding and contracting upper atmosphere, interactions between core and mantle, and the like.

Over the past couple of decades the Earth's day has actually been getting a little shorter, as evidenced by the lower number of leap seconds needed to keep things in synch. I don't know why this is the case; as I say, it's a complex issue.