Below is a GRACE satellite map. The Earth looks like a warty ball, with red bumps and blue pits that represent measured fluctuations in the planet’s gravity. Note Greenland in the red. We’ve covered GRACE before, suggesting it may not be a good tool to measure ice loss in Greenland. See this WUWT story.
The red spots represent measurements where Earth’s gravity is stronger. The blue ones are where it is measured to be weaker. The universal force of gravity itself does not vary, but the pits and bumps are a local indication that Earth’s mass distribution isn’t smooth and uniform. As seen on the image above, tectonic mountain building in South America produces red zones; elsewhere, tectonic movements produce thin, blue, ones.
Even more interesting is the fact that the map changes over time, Earth as we know is not static.
CO2 science reviews this new paper, which suggests that for sea level rise and ocean mass, the signal to noise ratio is high low and adjustments further complicate the issue. It also suggests some studies aren’t appropriately correcting for these issues. For example, GRACE measurements related to Greenland and West Antarctica (which we also criticized in WUWT here and here):
“…non-ocean signals, such as in the Indian Ocean due to the 2004 Sumatran-Andean earthquake, and near Greenland and West Antarctica due to land signal leakage, can also corrupt the ocean trend estimates.”
Ocean Mass Trends (and Sea Level Estimates) from GRACE Reference
Quinn, K.J. and Ponte, R.M. 2010. Uncertainty in ocean mass trends from GRACE. Geophysical Journal International 181: 762-768.
Background
The authors write that “ocean mass, together with steric sea level, are the key components of total observed sea level change,” and that “monthly observations from the Gravity Recovery and Climate Experiment (GRACE) can provide estimates of the ocean mass component of the sea level budget, but full use of the data requires a detailed understanding of its errors and biases.”
What was done
In an effort designed to provide some of that “detailed understanding” of GRACE’s “errors and biases,” Quinn and Ponte conducted what they describe as “a detailed analysis of processing and post-processing factors affecting GRACE estimates of ocean mass trends,” by “comparing results from different data centers and exploring a range of post-processing filtering and modeling parameters, including the effects of geocenter motion, PGR [postglacial rebound], and atmospheric pressure.”
What was learned
The two researchers report that the mean ocean mass trends they calculated “vary quite dramatically depending on which GRACE product is used, which adjustments are applied, and how the data are processed.” More specifically, they state that “the PGR adjustment ranges from 1 to 2 mm/year, the geocenter adjustment may have biases on the order of 0.2 mm/year, and the atmospheric mass correction may have errors of up to 0.1 mm/year,” while “differences between GRACE data centers are quite large, up to 1 mm/year, and differences due to variations in the processing may be up to 0.5 mm/year.”
What it means
In light of the fact that Quinn and Ponte indicate that “over the last century, the rate of sea level rise has been only 1.7 ± 0.5 mm/year, based on tide gauge reconstructions (Church and White, 2006),” it seems a bit strange that one would ever question that result on the basis of a GRACE-derived assessment, with its many and potentially very large “errors and biases.” In addition, as Ramillien et al. (2006) have noted, “the GRACE data time series is still very short,” and results obtained from it “must be considered as preliminary since we cannot exclude that apparent trends [derived from it] only reflect inter-annual fluctuations.” And as Quinn and Ponte also add, “non-ocean signals, such as in the Indian Ocean due to the 2004 Sumatran-Andean earthquake, and near Greenland and West Antarctica due to land signal leakage, can also corrupt the ocean trend estimates.”
Clearly, the GRACE approach to evaluating ocean mass and sea level trends still has a long way to go — and must develop a long history of data acquisition — before it can ever be considered a reliable means of providing assessments of ocean mass and sea level change that are accurate enough to detect an anthropogenic signal that could be confidently distinguished from natural variability.
References
Church, J.A. and White, N.J. 2006. A 20th-century acceleration in global sea-level rise. Geophysical Research Letters 33: 10.1029/2005GL024826.
Ramillien, G., Lombard, A., Cazenave, A., Ivins, E.R., Llubes, M., Remy, F. and Biancale, R. 2006. Interannual variations of the mass balance of the Antarctica and Greenland ice sheets from GRACE. Global and Planetary Change 53: 198-208.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
The idea of curved space time acting like a force is difficult to intuit. According to theory, all bodies will move in a straight line through space-time unless acted on by a force. So from this I conclude that when a body curves and accelerates towards a massive object, it is actually moving in a straight line at a constant speed through space-time, so the latter must be curved in some way. Moreover, since acceleration is a function of time, then the rate of time must also be changed by the massive object.
Massive objects do indeed slow time by a small degree. Another prediction of general relativity is that a clock will move from A to B in such a trajectory that the clock will show the smallest elapsed time. This is why a body must fall to earth. If it followed any other trajectory over a given distance, the clock would not show the smallest possible elapsed time.
All these effects of clock changes are built into the GPS system, which compensates for the effects of general relativity. I’m just wondering if this is allowed for in the GRACE system?
George E. Smith says:
July 20, 2010 at 3:16 pm
“”” Enneagram says:
July 20, 2010 at 2:27 pm
The force of gravity itself does not vary
It does!, as the image itself shows it. It can be, say, 9.79, 9.81, (acceleration in m/sec.sq.) “””
Not according to my Physical Chemistry Book.
It says that ( g ) is 9.80665 and THAT IS AN EXACT VALUE ! ( ms^-2 )
Reading this imediately had me reaching for my year 1 physics text book. College Physics by Weber manning & White pp 56 (yes I still have it, and it dates me). It shows g in St Michael, Alaska as 9.822 m/s^2, and Key West Fla as 9.79 m/s^2. Both of these at 1 m elevation. So it appears that back in 1965 g was accepted as not being an exact value.
[Reply: You are putting up other blogs to do your arguing for you. -1 for laziness. Make your own arguments here. ~dbs, Mod.]
Actually, I wrote the articles. -1 for being presumptuous.
UPDATE: I now see the comment above, snipped by another moderator. Not sure why. But links have been provided by John Cook below. -Anthony
followed by:
John Cook
[snip. repeatedly flogging your blog is at least immodest. ~dbs, mod.]
Umm So Anthony approved of the links being shown as provided by me and John Cook and yet they’ve been refuted by the moderator twice now?
Certainly when there has been a response to an article to do with this subject then there is a right to have it posted. Anthony seems to allow individuals to do so but why doesn’t the moderator?
The links are as follows:
http://www.skepticalscience.com/Part-One-Why-do-glaciers-lose-ice.html
http://www.skepticalscience.com/Part-2-How-do-we-measure-Antarctic-ice-changes.html
http://www.skepticalscience.com/Part-2-How-do-we-measure-Antarctic-ice-changes.html
REPLY: Robert I’m approving these, but you both really do need to dial it back a bit -1 for being snarky to both 😉 – Anthony
Anthony Watts says:
July 20, 2010 at 7:08 pm
BTW the link in your post above is broken, becuase you added a space between www and the period. Would you like me to fix it for you?
Yeah I figured if I broke the link it might get through the moderation. I know it isn’t your intention to have this whole moderation mess occur with this stuff but unfortunately it has. I tend to like this site for some of the analysis but I have been having a big beef with Goddard’s analysis of Greenland and Antarctica that’s why I posted links to the posts over there which tried to address Goddard’s criticism for Antarctica.
Zeke the Sneak says:
July 20, 2010 at 4:01 pm
…so, ” get me a ground line and I will discharge down that sneaky gravity”
tty says: stuff about uplift.
Wouldn’t uplift result in underestimations of ice losses then with altimetry which measures elevation changes?
George E. Smith says:
July 20, 2010 at 4:20 pm
I think IT IS electrostatic, so you can rub a comb on your sweater and attract small pieces of paper against gravity. To cancel gravity you should find a way to discharge that electrostatic charge to ground, but where is it that ground connection?
@Jantar
So it appears that back in 1965 g was accepted as not being an exact value.
Nope, I studied back in 1958 and my first lab practice on gravity was to measure it letting a ball drop on a inclined plane.
Robert
If Greenland and Antarctica are melting down as GRACE misinterpreters claim, why hasn’t the rate of sea level rise increased? Where is the melt going? Have they defied the laws of conservation of mass?
The fact that we do not understand gravity in this space age should cause alarm. Our cosmology — our view of our situation in the universe — is based on a mystery! The ‘big bang’ is a monumentally expensive work of fiction.
http://www.holoscience.com/news.php?article=89xdcmfs&pf=YES
Anna, Vince, Zeke,
Thank you, all, for the contributions on relativistic gravity. My original point was that I do not believe that all of the various space-time curvature, relativistic mass changes and time dilations involved in general relativity have been accounted for when thinking of gravity as a “force”. Sorry but I cannot yet buy “electric gravity”. Yes, there may be some missing understanding of gravity given the inability of present physics to combine quantum physics and general relativity or really explain the theorized dark matter or the theorized accelerated expansion of the universe. At the same time Einstein’s theory is at the present time, like Newton’s theory was at his time, the closest experimentally proven theory compared to scientific observations. And I do not believe, correct me if I am wrong, the GRACE information above is taking this all into account. Of course, all of these effects may be so miniscule as to be irrelavent but thinking of gravity as a force leads to missing the point about mass distributions.
PS: Anthony, no offense intended regarding the “gravity lesson”.
stevengoddard says:
July 21, 2010 at 7:57 am
Robert
If Greenland and Antarctica are melting down as GRACE misinterpreters claim, why hasn’t the rate of sea level rise increased? Where is the melt going? Have they defied the laws of conservation of mass?
GeoFlynx – The yearly contributions of melting ice in Greenland and Antarctica, some ~300 gigatonnes, would add .8 mm to sea level rise (my own calculation – maybe not so precise). The error bar for yearly sea level change ranges from .4 mm to .7 mm over a total rise of 2.8 mm/year to 3.1 mm/year (wiki). Perhaps this signal is not so obvious.
GeoFlynx
You seem to be suggesting that the GRACE measurements are in the noise.
REPLY: Robert I’m approving these, but you both really do need to dial it back a bit -1 for being snarky to both 😉 – Anthony
I’ll tone down the snarkiness, people get frustrated from time to time i guess.
stevengoddard says:
July 21, 2010 at 7:57 am
>>If Greenland and Antarctica are melting down as GRACE misinterpreters claim, why hasn’t the rate of sea level rise increased? Where is the melt going? Have they defied the laws of conservation of mass?<<
Cazenave et al. (2009) "We note that land ice plus land waters has
contributed for 75%–85% to recent sea level rise, i.e., significantly
more than during the decade 1993–2003 (Bindoff et al., 2007)."
"Between 1990 and 2003, the IPCC 4th Assessment Report
determined a Glacier and Ice Cap (GIC) contribution to sea level rise
of 0.77+/−0.22 mm/yr (Lemke et al., 2007)."
"Summing the ice sheet and glacier contributions as discussed
above, leads to a total land ice component of 2.1+/−0.25 mm/yr ESL
over 2003–2008."
"we show that recent years sea level rise can be mostly explained by an increase of the mass of the
oceans. Estimating GRACE-based ice sheet mass balance and using published estimates for glaciers melting, we further show that ocean mass increase since 2003 results by about half from an enhanced contribution of the polar ice sheets – compared to the previous decade"
Cazenave et al. 2009 "Sea level budget over 2003–2008: A reevaluation from GRACE space gravimetry, satellite altimetry and Argo"
“”” Enneagram says:
July 21, 2010 at 7:27 am
George E. Smith says:
July 20, 2010 at 4:20 pm
I think IT IS electrostatic, so you can rub a comb on your sweater and attract small pieces of paper against gravity. To cancel gravity you should find a way to discharge that electrostatic charge to ground, but where is it that ground connection? “””
To whom it may concern; please be advised that I SAID NO SUCH THING !!
Please don’t cite something as being something I said; unless you can cut and paste it from something I actually did say.
stevengoddard says:
July 21, 2010 at 7:57 am
>>If Greenland and Antarctica are melting down as GRACE misinterpreters claim, why hasn’t the rate of sea level rise increased? Where is the melt going? Have they defied the laws of conservation of mass?<<
First little note, don't call GRACE scientists misinterpreters, you are the one who FALSELY claimed that east antarctica couldn't be losing ice because it is too cold. You were called out and shown to be wrong but have yet to admit it.
Onto the study,
To clarify, the authors indicate that thermal expansion is contributing far less as ocean heat content has not risen as much as over the previous decade BUT ice sheets have begun to lose mass extensively which has kept the Sea level rise going significantly.
Also before anyone trashes on any of the authors note that people were certainly ready to support berthier’s work (one of the co-authors and a leader in glaciology) when he published a study reducing alaskan glacier losses.
http://wattsupwiththat.com/2010/02/07/new-study-using-satellite-data-alaskan-glacier-melt-overestimated/
So are we going to be as unbiased as we were then and give the cazenave paper a chance?
I have difficulty grasping the concept that there is a gauge theory for gravity like for the other 3 forces yet gravity is said to create a curvature of spacetime.
Why don’t the other 3 forces bend spacetime – or is the curvature of spacetime an obsolete concept when we talk about gravity as quantum gravity?
IOW, what’s special about gravity when it’s a force transmitted by some bosons just like the others?
“”” Jantar says:
July 21, 2010 at 5:37 am
George E. Smith says:
July 20, 2010 at 3:16 pm
“”” Enneagram says:
July 20, 2010 at 2:27 pm
The force of gravity itself does not vary
It does!, as the image itself shows it. It can be, say, 9.79, 9.81, (acceleration in m/sec.sq.) “””
Not according to my Physical Chemistry Book.
It says that ( g ) is 9.80665 and THAT IS AN EXACT VALUE ! ( ms^-2 )
Reading this imediately had me reaching for my year 1 physics text book. College Physics by Weber manning & White pp 56 (yes I still have it, and it dates me). It shows g in St Michael, Alaska as 9.822 m/s^2, and Key West Fla as 9.79 m/s^2. Both of these at 1 m elevation. So it appears that back in 1965 g was accepted as not being an exact value. “””
Perhaps one of us, may be having some problems with the English Language.
“””””” Not according to my Physical Chemistry Book.
It says that ( g ) is 9.80665 and THAT IS AN EXACT VALUE ! ( ms^-2 ) “”””””
That is an exact cut and paste from my post; so it IS what I wrote; and it IS what you extracted; so what part of it do you have a problem with ??
The “Physical Chemistry Book” to which I referred is:- “Physical Chemistry” ninth edition authored by Peter Atkins and Julio De Paula ISBN-13:978-1-492-1812-2 published in 2010 with earlier versions published back to 1998. And the value I cited is directly from an opening page Table of General Data and Fundamental Constants.
That table also cites that ( c ) = 2.99792558 E8 ms^-1 is also an exact value.
My Physics Handbook also cites exact values for the two variables known as epsilon naught, and mu naught, the permittivity, and permeability of free space. The latter of course is also 4 pi .E-7 and both parameters must be exact since ( c ) is the inverse of the square root of their product.
My Physical Chemistry Book is also the Official Text for the current year at Stanford University, in presumably Physical Chemistry.
So I simply stated what the book said ( g ) has the exact value 9.80665 ms^-2
The discerning reader would also note that the book gives 9.80665 ms^-2 as the exact value of the constant ( g ).
It says nothing about what the acceleration is under local gravity in Alaska or Florida or any place else.
The Warty GRACE globe presumably IS a map of the local acceleration; it is NOT measuring the constant ( g ).
Oh, i see. It’s only a figure of speech.
George E. Smith’s g seems to be called the standard gravity according to the wikipedia and is well-defined:
http://en.wikipedia.org/wiki/Standard_gravity
Robert
Please describe your theory of how ice 700 km inland in Antarctica is responding to minor changes along the coast over the last decade.
Lots of people who have no idea what they are talking about say all kinds of things. I choose to ignore them.
stevengoddard says:
July 21, 2010 at 10:03 am
GeoFlynx
You seem to be suggesting that the GRACE measurements are in the noise
GeoFlynx – This would be a consideration when the ice loss volume is divided over the Earth’s oceans and is being measured in terms of sea level rise. The loss of ~200 gigatonnes yearly, in a more confined area such as Greenland, produces a more negative gravity response that has been measured by the GRACE instrument.
Goddard,
see http://www.skepticalscience.com/Part-Three-Response-to-Goddard.html
It has many maps showing how the regions you are questioning as being too far inland are in fact losing ice and responds to some other allegations you make. If you have no intention of reading it then that is your choice but don’t sit back and argue it can’t happen when there’s a link right there which addresses this issue.