Changing a planets rotation speed

[hidlAP2010]

Is it possible to speed up or slow down the speed of a planets rotation by attaching jet engines (or some other device) along the equator of the planet?

 

[dacruick]

yes but infinitesimally so.

 

[jambaugh]

Is it possible to speed up or slow down the speed of a planets rotation by attaching jet engines (or some other device) along the equator of the planet?

If you look at the length of a solar day, it is not a constant but varies somewhat randomly due to the change in winds throughout the seasons. Now considering the atmosphere, your scheme of attaching jets will in effect change the winds but friction will eventually overcome the effect.

To permanently change the rotation speed your jets need to exhaust reaction mass (e.g. gas) into space. This way you affect the solid/liquid Earth plus its gaseous atmosphere together in the same direction.

 

[K^2]

If you look at the length of a solar day, it is not a constant but varies somewhat randomly due to the change in winds throughout the seasons.

What? First of all, the mass of the atmosphere is a little less than 10^-6 of the Earth's mass. Secondly, the highest winds don't reach a 3rd of the Earth's rotation speed at the equator. And finally, and most importantly, the winds always blow perpendicular to pressure gradient, and that means that the average wind velocity in any cyclone, storm, or tornado is zero.

There are additional prevalent winds due to Coriolis effect, but these also net zero if you take the entire atmosphere.

There is absolutely nothing happening in the atmosphere that can possibly change the length of solar day by any measurable amount. Tectonic drift makes a bigger difference.

 

[gneill]

Sure, by imparting an overall angular velocity to the atmosphere you could change
the angular velocity of the Earth. This works by conservation of angular momentum;
the total angular momentum of the Earth-Atmosphere system is constant. Beware of
high winds, though!

Eventually, friction between the atmosphere and Earth's surface would restore the original
state once the engines stopped driving energy into the atmosphere.

To get an idea of the magnitude of the problem, a little mathematics:

The moment of inertia of a homogeneous sphere divided by its mass and the square
of its radius is 2/5. That of a hollow spherical shell is 2/3. So, representing the Earth
as a homogeneous sphere of mass Me and radius R, the atmosphere as a hollow
spherical shell of mass Ma and radius R (it's a very thin skin on the surface of the Earth),
and the initial rotational velocity of both as W0, we have:

I = ((2/5)*Me*R^2 + (2/3)*Ma*R^2)*Wo

This will be a constant.

Now, if we allow the components (Earth and Atmosphere) to have different angular
velocities (We and Wa), the sum of their contributions of angular momentum must still
add up to I. Thus,

I = (2/5)*Me*R^2*We + (2/3)*Ma*R^2*Wa

Rearranging to solve for we,

We = (I - (2/3)*Ma*R^2*Wa)/(*2/5)*Me*R^2)

In order to see how We varies with Wa, we can differentiate the above expression for We
with respect to the variable Wa:

dWe/dWa = -(5/3)*Ma/Me

and given known values for the masses of the Earth and Atmosphere:

Me = 5.97 x 10^24 kg
Ma = 5.27 x 10^18 kg

dWe/dWa = -1.47 x 10^-6

That's a very small effect.

 

[gneill]

What? First of all, the mass of the atmosphere is a little less than 10^-6 of the Earth's mass. Secondly, the highest winds don't reach a 3rd of the Earth's rotation speed at the equator. And finally, and most importantly, the winds always blow perpendicular to pressure gradient, and that means that the average wind velocity in any cyclone, storm, or tornado is zero.

There are additional prevalent winds due to Coriolis effect, but these also net zero if you take the entire atmosphere.

There is absolutely nothing happening in the atmosphere that can possibly change the length of solar day by any measurable amount. Tectonic drift makes a bigger difference.

The state of the atmosphere does have an effect on the rotation rate of the Earth.
The main seasonal effect is due to the overall expansion and contraction of the
atmosphere with differing heat content, which shifts its moment of inertia and hence
its angular momentum.

The different heat content is due to the asymmetry of the land mass and water
distribution between the Northern and Southern hemispheres, which influences the
overall albedo.

See, for example, the graph "Atmospheric excitation over the current year" at the
site:

http://hpiers.obspm.fr/eop-pc/"

 

[K^2]

The expansion/contraction is balanced by the two hemispheres. Same with water content.

 

[gneill]

The expansion/contraction is balanced by the two hemispheres. Same with water content.

The overall atmosphere height varies, changing the its moment of inertia. Furthermore,
the jet streams, which moves a significant amount of air mass around, shifts significantly
over the course of a year.

Also, because of the different overall atmospheric heat content in different seasons
(again due to different land mass and water distributions in the hemispheres), the
atmosphere will contain more water moisture when it is hotter, and thus be more
massive and have larger angular momentum.

 

[K^2]

If there is sufficient temperature change, the thermal expansion of the continents themselves is going to make a bigger difference.

The oceanic mass is also significantly greater than atmospheric. You'd have to talk about shifting currents before you talk about the atmosphere.

I see absolutely nothing in your argument to point to atmosphere being the cause of the seasonal changes in day cycle. The graph on the site you posted suggests that the error in measurement is on the order of 0.5ms with oscillations on order of 2ms. If the atmospheric mass is less than 100th of oceanic, how are you planning to distinguish effects?

 

[RocketSci5KN]

Unless you physically threw mass out at escape velocity, you wouldn't change the rotation rate of the earth. What you could do is transport mega amounts of rock from the equator to the poles, or visa versa, to allow for extremely small changes. Note that major earthquakes can slightly affect the length of a 'day'. Of course, no one will help you pay for this ;->

 

[gneill]

If there is sufficient temperature change, the thermal expansion of the continents themselves is going to make a bigger difference.

The oceanic mass is also significantly greater than atmospheric. You'd have to talk about shifting currents before you talk about the atmosphere.

I see absolutely nothing in your argument to point to atmosphere being the cause of the seasonal changes in day cycle. The graph on the site you posted suggests that the error in measurement is on the order of 0.5ms with oscillations on order of 2ms. If the atmospheric mass is less than 100th of oceanic, how are you planning to distinguish effects?

The thermal expansion rate for the crust and water is far smaller than that of a gas
(the atmosphere). Further, the average temperature of the crust below a few centimeters
and the oceans below a few meters depth does not vary significantly (except perhaps where ocean currents carry water between depth levels, the so-called "elevators").

Further, any expansion of the Earth's surface is going to exacerbate the atmospheric change, pushing the whole atmosphere further from the Earth's center.

I do not see where you obtained the information regarding the measurement error for
the graph presented at

http://hpiers.obspm.fr/eop-pc/"

One would need to find the author's data reduction method to determine that. Simply
eyeballing the graph, which is not raw data and does not contain error bars, will not
tell you.

I should also point out that nowhere did I affirm that changes in the atmosphere is the
only thing affecting the rotation rate of the planet. Anything that can affect the overall
moment of inertia of the system or its components can have an effect. This includes
seasonal variations in ice packs, snow cover, etc.

 

[K^2]

See these high frequency oscillations? That's your measurement error. Whether these are real oscillations or problems with measurement method is irrelevant. They prevent you from determining the seasonal dependence more accurately.

The seasonal dependence is just barely greater than these oscillations. So if you want to prove that atmosphere provides a measurable change of solar day, you need to prove that atmospheric effect is one of the major effects.

Go.

 

[Borek]

http://www.jstor.org/pss/74779

Seasonal changes in the length of day are primarily of meteorological origin.

Higher-frequency variations in length of day are also primarily of meteorological origin and will mask or interfere with other geophysical factors affecting the Earth's rotation, such as tides or earthquake caused changes in the inertia tensor.

http://www.nasa.gov/centers/goddard/news/topstory/2003/0210rotation.html

Changes in the atmosphere, specifically atmospheric pressure around the world, and the motions of the winds that may be related to such climate signals as El Niño are strong enough that their effect is observed in the Earth’s rotation signal

and so on.

 

[gneill]

See these high frequency oscillations? That's your measurement error. Whether these are real oscillations or problems with measurement method is irrelevant. They prevent you from determining the seasonal dependence more accurately.

The seasonal dependence is just barely greater than these oscillations. So if you want to prove that atmosphere provides a measurable change of solar day, you need to prove that atmospheric effect is one of the major effects.

Go.

I disagree. If the graph depicts the rotational effects due to atmospheric effects alone,
then the seasonal variation stands out clearly.

You can look at longer time intervals for this sort of data, too, and the same seasonal
variations stand out on the background "noise". This site allows you to produce graphs
for various periods:

http://hpiers.obspm.fr/eop-pc/index.php?index=excitactive&lang=en"

Here's such a graph for the years 2000 - 2010

http://hpiers.obspm.fr/eop-pc/analysis/excitactive1.php?IB=1&term=1&AAM=1&option=1&dimx=600&dimy=450&langue=1&sel_option1=1&choix=3&trend=1&filter=Select+band+above&P0=1&tr=95&spec=0&freqmin=-10&freqmax=10&choixspec=4&chi_g=1&chi_f=1&TC=433&QC=100&SUBMIT=Submit+request&an1=2000&mois1=1&jour1=1&an2=2010&mois2=12&jour2=31

and one for just 2009:

http://hpiers.obspm.fr/eop-pc/analysis/excitactive1.php?IB=1&term=1&AAM=1&OAM=1&option=1&dimx=600&dimy=450&langue=1&sel_option1=1&choix=3&trend=1&filter=Select+band+above&P0=1&tr=95&spec=0&freqmin=-10&freqmax=10&choixspec=4&chi_g=1&chi_f=1&TC=433&QC=100&SUBMIT=Submit+request&an1=2009&mois1=1&jour1=1&an2=2009&mois2=12&jour2=31

Pick any year for (for which data is recorded) and you'll see the same clear variations.

Here's a graph for 2009 that shows just the effects due to "Oceanic excitation"

http://hpiers.obspm.fr/eop-pc/analysis/excitactive1.php?IB=1&term=1&OAM=1&option=1&dimx=600&dimy=450&langue=1&sel_option1=1&choix=3&trend=1&filter=Select+band+above&P0=1&tr=95&spec=0&freqmin=-10&freqmax=10&choixspec=4&chi_g=1&chi_f=1&TC=433&QC=100&SUBMIT=Submit+request&an1=2009&mois1=1&jour1=1&an2=2009&mois2=12&jour2=31

 

[D H]

There is absolutely nothing happening in the atmosphere that can possibly change the length of solar day by any measurable amount. Tectonic drift makes a bigger difference.

Late in the game, but this is wrong. Borek and gneill are correct in this regard, K^2. There has been *no* observable effect from the Chilean earthquake. The seasonal signature in length of day is quite obvious. Things like large El Nino events stick out like sore thumbs.

 

[K^2]

Absolutely none of that tells me that it's atmospheric. Yes, there is a correlation with weather. Good support there, especially with the El Nino confirming it. But the mass of the air is still tiny compared to the mass of the water and land masses that are being affected.

Alright, let's say that we can throw land out of equation. Top 15m of world's oceans alone has greater mass than all of Earth's atmosphere. And you are telling me that winds are responsible for observed effects, and not oceanic currents? I need to see some good models backed by hard evidence to believe that.

Edit: And I'm going to see how much one would need to warm up the entire planet by to get the solar day changed by 1ms due to thermal expansion of the atmosphere. I suspect the number to be fairly large.

 

[dacruick]

I agree with K^2. I also heard ( I can't remember where) that when they opened up a huge dam in China that it slowed the rotation of the Earth by a very small number.

Edit: Found it - http://www.businessinsider.com/chinas-three-gorges-dam-really-will-slow-the-Earth's-rotation-2010-6

 

[gneill]

Absolutely none of that tells me that it's atmospheric.

You mean besides the fact that the scientists who produced the graphs
state that it is?

Alright, let's say that we can throw land out of equation. Top 15m of world's oceans alone has greater mass than all of Earth's atmosphere. And you are telling me that winds are responsible for observed effects, and not oceanic currents? I need to see some good models backed by hard evidence to believe that.

As was already pointed out, the coefficient of expansion of water is far smaller than
that of air. The oceans also have a significant thermal mass which tends to greatly
smooth out short cycles. The atmosphere is much more sensitive to heat content
variations. I would imagine that land effects, such as snow and ice coverage, would
exceed those of water expansion.

Edit: And I'm going to see how much one would need to warm up the entire planet by to get the solar day changed by 1ms due to thermal expansion of the atmosphere. I suspect the number to be fairly large.

That should be an interesting calculation. It would be nice if you would post the details.

 

[K^2]

You mean besides the fact that the scientists who produced the graphs
state that it is?

I'm also a scientist, and I also can make graphs. I see a correlation between condition of atmosphere and planet rotation. So yes, I agree, there has to be a weather-relation. Interesting. Didn't know that. Good. What I don't see is any evidence that air currents have any direct effect on Earth's rotation.

As was already pointed out, the coefficient of expansion of water is far smaller than
that of air. The oceans also have a significant thermal mass which tends to greatly
smooth out short cycles. The atmosphere is much more sensitive to heat content
variations. I would imagine that land effects, such as snow and ice coverage, would
exceed those of water expansion.

You tell me severe storms don't affect oceanic currents? Didn't El Nino screw up Gulf Stream? Now consider how much water is flowing through Gulf Stream and what that's going to do to Earth's rotation. Now THAT is a significant change.

Show me some evidence that suggests that air currents can have direct effect.

That should be an interesting calculation. It would be nice if you would post the details.

Of course.

 

[D H]

Edit: And I'm going to see how much one would need to warm up the entire planet by to get the solar day changed by 1ms due to thermal expansion of the atmosphere. I suspect the number to be fairly large.

Wrong calculation. The right calculation is to see how much you would need to cool the atmosphere of the northern hemisphere, but maintaining the same pressure, to change length of day by 1 ms.

Simplifying things somewhat, the northern hemisphere is largely land while the southern hemisphere is largely water. While Antarctica does get considerably colder than the Arctic, Antarctica is very high (mean elevation = 2500 meters). Putting these two items together means that atmospheric mass moves from equatorial regions toward the north pole in northern hemisphere winter and back toward the equator in northern hemisphere summer.

 

[K^2]

Aha. Ok, that makes more sense, in that it at least sounds like it might work. I'll give it a shot. Thanks.

 

[gneill]

I'm also a scientist, and I also can make graphs. I see a correlation between condition of atmosphere and planet rotation. So yes, I agree, there has to be a weather-relation. Interesting. Didn't know that. Good. What I don't see is any evidence that air currents have any direct effect on Earth's rotation.


You tell me severe storms don't affect oceanic currents? Didn't El Nino screw up Gulf Stream? Now consider how much water is flowing through Gulf Stream and what that's going to do to Earth's rotation. Now THAT is a significant change.

Show me some evidence that suggests that air currents can have direct effect.


Of course.

The El Nino affects are mainly in the Pacific basin. The Gulf Stream is Atlantic.

The main driving force for the majority of the ocean currents are winds.

"The major ocean currents are wind-driven currents, though some ocean currents result from density and salinity variations of water."​

http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/circulation/ocean_circulation.html"

The water currents may transport a lot of water over time, but it's not as
though they leave holes in the ocean in one place and create mountains of
water elsewhere -- the currents are essentially closed circuits. Also, consider
that the 'relaxation time' for the tidal bulges is certainly less than a day.

 

[K^2]

I must have been thinking of some other major cyclone.

All of the points you make for water currents can be made for air currents as well. In order to change Earth's rotation, you have to move a very large mass. That's going to be equally difficult regardless of the source of mass.

All currents are ultimately air-driven. It might be wind moving water surface, or it could be wind carrying moisture up the mountains. Still atmosphere-dependent. That's sort of my whole point. Showing there is correlation doesn't tell you that it's the wind that's changing the Earth's rotation. Could be changing something that changes rotation.

So far, the model DH suggests is the only one I see that can work, but that would only explain seasonal changes, not high frequency ones. I would still look at oceanic currents for these. And I still need to run the numbers to see how much temperature change we'd be talking about.

 

[gneill]

I must have been thinking of some other major cyclone.

All of the points you make for water currents can be made for air currents as well. In order to change Earth's rotation, you have to move a very large mass. That's going to be equally difficult regardless of the source of mass.

All currents are ultimately air-driven. It might be wind moving water surface, or it could be wind carrying moisture up the mountains. Still atmosphere-dependent. That's sort of my whole point. Showing there is correlation doesn't tell you that it's the wind that's changing the Earth's rotation. Could be changing something that changes rotation.

So far, the model DH suggests is the only one I see that can work, but that would only explain seasonal changes, not high frequency ones. I would still look at oceanic currents for these. And I still need to run the numbers to see how much temperature change we'd be talking about.

Water currents have far too much momentum, and water has far too much thermal mass,
to admit oscillations on with a period as short as a day.

The atmosphere is far more mobile, and is subject to large scale density variations
with temperature. Motion in the atmosphere is driven by pressure differences. Large scale
(not individual weather system) pressure differences are sorted out on short time scales,
but that still leaves density and temperature to play with. PV = nRT. For a given air
pressure, there can be more air mass at lower temperatures.

Temperature variations due to insolation shifts large amounts of air mass between the
poles and the tropics (the North pole in particular) with seasonal changes. Shorter
term changes (on a the order of a single day) are allowed too, since the thermal
mass of the atmosphere is relatively low and it can heat or cool regionally on short
timescales; look at the day/night temperature variations of the air at ground level,
which is actually moderated by proximity to the thermal mass of the Earth and oceans.

About 80% of the atmosphere's mass is in the troposphere, which "hugs" the Earth.
It's depth varies from about 8km to 16km with temperature variations.

 

[jambaugh]

What? First of all, the mass of the atmosphere is a little less than 10^-6 of the Earth's mass. Secondly, the highest winds don't reach a 3rd of the Earth's rotation speed at the equator. And finally, and most importantly, the winds always blow perpendicular to pressure gradient, and that means that the average wind velocity in any cyclone, storm, or tornado is zero.

There are additional prevalent winds due to Coriolis effect, but these also net zero if you take the entire atmosphere.

There is absolutely nothing happening in the atmosphere that can possibly change the length of solar day by any measurable amount. Tectonic drift makes a bigger difference.

You mention 10^-6 mass ratio. Just a bar napkin calculation I know but 10^-6 days = 0.0864 seconds. That's clearly a measurable order of magnitude. There is also the fact that the atmosphere is for the most part farther from the axis of rotation than the ground and sea, especially in the tropics where you have seasonally varying prevailing winds.
So I'm not yet willing to concede your point. You do the calculation, assume say a 20kph difference in the atmosphere between the tropic lines, figure the mass and moment of Inertia of this ring of atmosphere relative to the moment of inertia of the whole Earth and work out the change in the solar day to see if indeed it is measurable.

That having been said, I may have spoken hastily. I recall from my childhood that the solar day varies measurably from day to day and throughout the season and I may have merely assumed it was due to atmospheric motion especially seasonal wind variations rather than having read it. It is something I always thought to be true but I can cite no source so withdraw the specific statement.

None-the-less in the OP conversation w.r.t. attaching jets to the Earth, the point is still that as a matter of principle one would only affect the Earth relative to the atmosphere, temporarily pumping angular momentum between solid/liquid Earth and the air. This effect will dissipate as the wind blows through the trees, over rocks and waves, and through a pretty girl's hair.

 

[K^2]

Oy. You guys have no sense of scale. Again, except for DH who suggested something at least seemingly reasonable. I still have to check it.

Water currents have far too much momentum, and water has far too much thermal mass,
to admit oscillations on with a period as short as a day.

You can't dig yourself out of this hole by claiming air has lower mass. If it has lower mass, you have to move more of it to effect the same change in Earth's rotation. The momentum change has to be the same. You can move a cubic foot of water or a thousand cubic feet of air. Mass you are shifting is the same.

And what does heat capacity of water have to do with anything? We already agreed that water currents are going to be affected by changes in atmosphere, didn't we? So it's still atmosphere's thermal properties we are talking about.

The atmosphere is far more mobile, and is subject to large scale density variations
with temperature. Motion in the atmosphere is driven by pressure differences. Large scale
(not individual weather system) pressure differences are sorted out on short time scales,
but that still leaves density and temperature to play with. PV = nRT. For a given air
pressure, there can be more air mass at lower temperatures.

Yeah, except air moves almost perpendicular to pressure gradient due to Coriolis Effect, so nearly all movements are cyclic. The net shifts, like DH suggests, take quite a while in part because of that. Air can't just rush straight towards lower pressure.

Temperature variations due to insolation shifts large amounts of air mass between the
poles and the tropics (the North pole in particular) with seasonal changes. Shorter
term changes (on a the order of a single day) are allowed too, since the thermal
mass of the atmosphere is relatively low and it can heat or cool regionally on short
timescales; look at the day/night temperature variations of the air at ground level,
which is actually moderated by proximity to the thermal mass of the Earth and oceans.

And you imagine that a significant portion of air mass can move from tropics to poles in a day? I'd be really worried if it was true. And local changes a) Going to result in cyclones as outlined above, and b) Won't be enough even if they allowed all of the air to shift at once.

About 80% of the atmosphere's mass is in the troposphere, which "hugs" the Earth.
It's depth varies from about 8km to 16km with temperature variations.

Yeah. And the change in depth happens because the tropopause shifts, not because you get that much more/less air. Again, if you had an actual reduction in amount of air above your had sufficient to half the troposphere, you'd be having a very, very bad day. A barometer dropping to 380mm is NOT a good sign.

You mention 10^-6 mass ratio. Just a bar napkin calculation I know but 10^-6 days = 0.0864 seconds. That's clearly a measurable order of magnitude.

Oh, yes. Certainly. So how do you propose getting 100% of Earth's atmosphere up to 240m/s at equator that would be necessary for this? Next question, how do you propose surviving said disaster?

Again, SCALE.

If the ENTIRE atmosphere was rotating as a shell with equatorial speed of 2.4m/s, we'd be talking about a 0.8ms time difference. That's ALL of the air moving in the SAME direction at a descent wind speed.

And here you are trying to tell me that the 2ms time differences recorded are taken care of by winds, which are mostly random flows in mostly randomly distributed atmosphere? Hogwash.

 

[D H]

gneill:
A word of advice on posting: Don't insert hard carriage returns to end your lines within a paragraph. Just keep on typing your words and sentences. Those hard carriage returns that you use force a browser to start a new line. Depending on a user's browser and the width of a user's screen, those hard returns can look quite ugly and can make for hard-to-read posts. Do use two hard returns to end a paragraph (and you do do that).K^2:
Measurements of the Earth's orientation parameters are incredibly precise nowadays thanks to satellite, VLBI, and GPS measurements. The errors (one sigma) in excess length of day are on the order of 2 microseconds. You can find the most recent set of data in IERS Bulletin B, http://maia.usno.navy.mil/ser7/bulb.dat. Scroll down to section 3, "Earth angular velocity: Daily final values of LOD, omega at 0hUTC". For long-term archives, see the http://www.iers.org/IERS/EN/DataProducts/EarthOrientationData/eop.html?__nnn=true section at IERS. The http://www.iers.org/IERS/EN/DataProducts/GeophysicalFluidsData/fluids.html at IERS may also be of interest to you.

Here is a series of plots that depict variations in length of day from 1964 to 2002:

[PLAIN]http://www.iers.org/SharedDocs/Bilder/EN/Variations__in__the__duration__of__the__day,property=default.png

The fourth plot in the series depicts the contributions of the zonal tides to LOD. The tides are the greatest contributors to the short term variations in LOD. Tidal theory has been well understood for over a century. Any analysis of LOD variability is going to start with removing that high-frequency signal from the data. Note that there is a large pulse smack dab in the middle (1982-1983) of the residual plot. That is the 1982-1983 El Nino.

Some articles:

BF Chao, "Space Geodesy Monitors Mass Transports in Global Geophysical Fluids", Eos, Transactions American Geophysical Union, 81:22 (2000)
http://www.iers.org/nn_11262/SharedDocs/Publikationen/EN/IERS/Products/ggf/EOS__article,templateId=raw,property=publicationFile.pdf/EOS_article.pdf
This article does a nice job of summarizing the contributions to variations in the Earth's angular velocity vector.

JB Merriam, "Atmospheric excitation of the Earth's rotation rate", in "Variations in Earth rotation", American Geophysical Union A92-31576 (1990)
http://books.google.com/books?id=_6My7JR6dRgC&pg=PA119&lpg=PA119#v=onepage&q&f=false.

Gross et al., "Atmospheric and oceanic excitation of length-of-day variations during 1980 – 2000", Journal of Geophysical Researh 109:B1 (2004)
http://ecco2.jpl.nasa.gov/menemenlis/articles/2003JB002432.pdf

Kolaczek et al. (eds), "High frequency to subseasonal variations in Earth Rotation", IERS Technical Note #28
http://www.iers.org/nn_11216/IERS/EN/Publications/TechnicalNotes/tn28.html
Note that this final reference contains many sub-articles that describe tidal effects, non-tidal oceanic contributions, tectonic contributions as well as atmospheric contributions to variations in LOD.

 

[K^2]

There is certainly something there to think about. I'm going to take a more careful look at the articles, maybe follow up some references, and see how it fits with what I know.

My knee-jerk response is to point out that they seem to check correlations only, but I really should read a bit into the articles themselves, rather than basing this on abstracts alone. I'll get back to you all on that.

 

[D H]

Another source of info, K^2: Google the phrase "atmospheric angular momentum".