New paper: A high-resolution surface mass balance map of Antarctica shows "no significant trend in the 1979–2010 ice sheet"

Note that the final number given is for an increase, though it is not statistically significant.

You left the minus sign off of the 3 in your last sentence. It should read:
“The estimated SMB trend, integrated over the ice sheet, equals -3 +/- 2 Gt y^(-2).”
I’ll assume it was a cut and paste error because of the fonts used. It happened to me just now when I pasted it in.

“based on output of a regional atmospheric climate model”? I thought models were GIGO? And how about GRACE?

Surface Mass Balance (SMB) is not the same thing as mass balance.
Mr. Watts, I believe that you are misinterpreting what this paper says.
For reference, the lead author is also a co-author on the 2011 GRL paper, “Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise”. Monaghan is also a c-author on this paper. If you read this paper ( http://ess.uci.edu/researchgrp/velicogna/files/rignot_etal_grl2011.pdf ) you may better understand the difference between mass balance and surface mass balance (SMB), which is clearly discussed on the first page.

You might want to check the sign of your ‘money quote’ against the paper.
You might want also to refresh your memories of the definition of mass balance (hint – check the units).
You might want also to compare this result with the IPCC projection.

In case my above comment was not clear enough:
Mass balance of Antarctica = SMB (water in) less perimeter loss (water out)
So the observation that SMB is more or less constant over the past 30 years says nothing about the perimeter loss, or about the mass balance of Antartica.
For a more complete discussion, including a comparison of two methods of measuring mass balance, I refer you to:
“Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise”
E. Rignot, I. Velicogna, M. R. van den Broeke, A. Monaghan, and J. Lenaerts
http://ess.uci.edu/researchgrp/velicogna/files/rignot_etal_grl2011.pdf

@Brian H
The final number in the paper is negative. The negative symbol is missing in the quote here.

@ Louis Hooffstetter:
Agree strongly with:
” I still felt a slight shudder when I read “the map is based on output of a regional atmospheric climate model”
If a reasonable scepticism is warranted for our current modelling of other complex climate phenomena, it should be here as well. We don’t want to cherrypick our models and undermine the value of broad-based scientific scepticism.

Okay, the modeled SMB is in good agreement with ±750 in-situ SMB measurements, so that’s some validation. But If it’s a model, how can it “confirm” anything? Shouldn’t this just be a “yay, we’ve got a more realistic model!” sort of hype?

William M. Connolley says:
February 20, 2012 at 3:12 pm
“I wonder how many commenters here ever read the IPCC analysis:”
Most likely no one. We have read the emails.

“”William M. Connolley says:
February 20, 2012 at 3:12 pm (of course, that is complicated by this model being *surface* mass balance, but that distinction is going to go right over your heads).””
The fact that the IPCC is unable to confirm or deny growth or shrinkage, that distinction between this empirical data of this paper and the IPCC uncertainty is probably going to go right over your head.
Of course people like J. T. M. Lenaerts, M. R. van den Broeke, W. J. van de Berg, E. van Meijgaard,and P. Kuipers Munneke wouldn’t come anywhere near your intellectual prowess.
William you are a legend in your own mind.

That explains why WMC has more time for WUWT comments I guess.

I guess this paper’s publication during Gore’s attempted Antarctic publicity stunt is just another version of the “Gore Effect”.

I’m confused. Does this mean we trust science?

As much as it sorely grieves me to have to admit it, in this case Connelly and others are correct. This paper doesn’t say what you think it does people. That said, it’s yet another paper based almost purely on modelling, so make of that what you will 😉

@LC
Ok, so we did trust science for a few minutes, but then it turns out the science we just agreed with disagrees with our opinion, so therefore we stopped trusting science again, and vehemently disagree with the paper?
Did I get that right?
(Censorship rocks!)
[Reply: Read the site Policy. You are threadbombing under numerous articles. This site does not censor different scientific points of view. We snip or delete posts that violate our written Policy. If that bothers you, please move on. And the next time you post “censorship rocks” or anything similar, I’ll give you what you’re wishing for. ~dbs, mod.]

The SMB map confirms high accumulation zones in the western Antarctic Peninsula (>1500 mm y^-1) and coastal West Antarctica (>1000 mm y^-1), and shows low SMB values in large parts of the interior ice sheet (<25 mm y^-1).
There isn’t much dispute that the western Antarctic Peninsula has warmed over this period with substantial peripheral ice melt. This study shows it snowed a lot more when the western Antarctic Peninsula warmed. Unsurprising as the warming results from increased oceanic influence. The increased snowfall will doubtless result in future glacial advances.
All in all, it points to a decadal oceanic cycle mainly determining western Antarctic Peninsula ice mass.

> 3+/-2 Gt/y^-2
That is an odd way to write the units. Did you mean Gty^-2 or the equivalent Gt/y^2?

@Smokey
Urban Dictionary: “”Threadbombing” is posting an image (or images) with superimposed text in a forum thread; usually to illustrate a point. Often, the “threadbomb” conveys a humorous message of disdain towards the original poster or the entire thread.”
WTF?

So, in Jones speak, the overall ice mass levels are flatlined, but just barely.

boston12gs says:
February 20, 2012 at 4:33 pm
Hey, poster identifying as “William Connelley”, is this you?
=============================================
..one and the same
Wikipedia Topic-Bans Global Warming Activist William Connolley, aka ‘Stoat’
By: Bradley Fikes — October 16th, 2010
Wikipedia is supposed to be a source of information, not propaganda. But William M. Connolley, who blogs under the name Stoat, has repeatedly abused his administrator position at Wikipedia to bias climate change-related articles to reflect his global warming activism.
But no more. After extensive run-ins with Connolley, Wikipedia has banned him from participating in climate change articles.
Since CAGW (Catastrophic Anthropogenic Global Warming) supposedly has so much evidence on its side, it’s remarkable how vehemently Connolley fought against letting Wikipedia readers read neutral articles that include the views of skeptics. His deceptive conduct was deeply unethical.
Watts Up With that points that that in addition to Connolley, other administrators on both sides of the global warming issue have been sanctioned. At least one CAGW-skeptical administrator says he was sanctioned for kicking up a fuss about the pro-CAGW bias.
At least the net result is a gain for fair editing, since Connolley was by far the most active in shamelessly inserting his bias into Wikipedia’s global warming articles.
Connolley’s pro CAGW campaign extended over years. I hope that Wikipedia speeds up its cumbersome bureaucratic process so that future offenders can be dealt with more swiftly.
http://www.nctimes.com/app/blogs/wp/?p=11266

Mike Smith says:
February 20, 2012 at 5:10 pm
Damn. The ice won’t melt. The sea level won’t rise. The temps have stopped increasing. The ozone hole has vanished. Hurricanes aren’t forming more frequently. The animals, plants, and humans won’t die. Carbon offsets won’t sell. The sheeple won’t buy our propaganda. The whole thing is crumbling before our eyes.
It’s a catastrophe, I tell you. Something needs to be done about it…
=======================================
It’s all hiding in the deep ocean Mike………………….

With all the attacks accumulating on William Connoley, few people have yet realized the substantial error in the post by Anthony Watts (or at the very least, that it gives a misleading impression of what is happening to Antarctica to people who don’t understand the terminology). It only takes a slight amount of courage or honesty for everyone to admit this, and does not depend on how much you like the IPCC, Connoley, Michael Mann, the climategate e-mails, or whatever else.
The total mass budget involves estimating the difference between surface mass balance (input) and perimeter fluxes (output). That said, Antarctica is almost certainly losing ice (contributing to sea level) in its net effect. The IPCC 2007 report is rather outdated on this subject and observational ability has improved tremendously since that time. See for example Rignot et al (2011, GRL); Velicogna, I., (2009, GRL), and there are large regional changes, especially in the Antarctic Peninsula & West Antarctica that are changing rapidly (e.g., Cook and Vaughan, 2010; Ivins et al., 2011). It would be nice to see some WUWT summaries of these papers…

A few observations on the various papers cited here:
“We found no significant trend in the 1979–2010 ice sheet integrated SMB components, which confirms the results from Monaghan et al. [2006].”
The following is not a surprise and consistent with “Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise” – http://ess.uci.edu/researchgrp/velicogna/files/rignot_etal_grl2011.pdf
The conclusion of this paper s that “The magnitude of the acceleration suggests that ice sheets will be the dominant contributors to sea level rise in forthcoming decades, and will likely exceed the IPCC projections for the contribution of ice sheets to sea level rise in the 21st century [Meehl et al., 2007].”
The implication being that even if SMB is relatively stable, MB is decreasing. This presumably implies that there is some empirical support for an increase in ice calving. What else could it be?
The conclusion reached by Rigno et. al, needless to say, is the opposite of the expectation of IPCC AR4, where GCM modelling is expecting to see an increasing SMB trend.
The main game in town is SMB, not MB. If MB is accelerating but SMB has no trend, then it seems difficult to reconcile this with GCM atmospheric modelling. Now if someone disagrees, I’d be interested in a different point of view. However, I would seek clarification on how MB acceleration can be explained in terms of AGW theory when there is no observable SMB trend.
In summary:
Rigno et al agrees with Lenaerts et al, on no trend in SMB but reaches the opposite conclusion of the IPCC AR4 report. On the other hand IPCC AR4 expected to see an increasing SMB trend, according to GCM’s, which is not observed by Lenaerts el al, either. So if the GCM’s are correct, it just hasn’t happened (yet) as predicted.
So you have a bunch of authorities who all basically disagree with each other in one way or another where it matters, which is sea level rise attributable to GW. Such is climate science.

Surface Mass Balance is different from total Mass Balance.
Dynamic loss is glaciers accelerating which is where most ice sheets lose their ice. This paper does not look at that. Noobs…

This thread and the comments with the abstract are not correct. This was not an assessment of mass balance of the ice sheet. It was modelling the surface mass balance. These are two different things.
It is idiotic to jump on a high horse and confound the two when they’re very different. Shame on everyone here for not reading the article or taking the time to learn anything at all on the subject before commenting.

Also for the record, this is creating a dataset that goes into complete mass balance surveys such as Rignot et al 2011. It is one component of Mass Balance for the whole ice sheet.
Antarctic Mass Balance = Ice Input – Ice Output
Ice Input comes through the SMB and the SMB is nearly 0 so the Antarctic Mass Balance then equals 0 minus ice outputs through calving and accelerating glaciers (Pine Island Glacier for Example).
Rignot et al. 2008 and Rignot et al. 2011 use INSAR Flux budget method to calculate the Mass Balance of the ice sheet by measuring the Output and comparing it to the SMB. They find losses are huge because of dynamic ice loss from accelerating glaciers.

OFF TOPIC-
Pter Gliek admits it. Go to Dot Earth.

Yawn: We don’t distrust science at all. We distrust studies if and when there is reason to do so. That Yawn is what science should do. If it can’t hold up to scrutiny then it isn’t science. If you have some meaningful reason to doubt this study, then your comments will be appreciated here.

There tends to be an awful lot of confirmation bias in reports like this, with people leaping onto anything that may confirm their views.
I suggest something simple – posts like this should always contact one of the paper’s authors to ask what it really means before doing a write-up. This would eliminate a great deal of baseless speculation. I do not know the difference between MB and SMB, so I will not comment, but it is clear that a lot of other people also do not know, but are willing to comment anyway.

Will Nitschke says:
February 20, 2012 at 6:00 pm
“In relation to AGW, the main game in town is, obviously, SMB and not MB.”
Not true. Dynamic ice losses are due to warming oceans causing grounding line retreat subsequently accelerating glaciers and carrying more ice to the sea. Warming oceans is definitely related to AGW. Noob.

Robert says:
Not true. Dynamic ice losses are due to warming oceans causing grounding line retreat subsequently accelerating glaciers and carrying more ice to the sea. Warming oceans is definitely related to AGW. Noob.
================================
Did you make that up or can you cite a paper for that claim? Just curious. I don’t have a problem if you write, “I speculate that it might be caused by…” but Warmists always post messages as if their proclamations were authoritative…
Also, since a number of Warmists here are arguing that SMB is irrelevant (when exactly the opposite is in fact true), and the basis of this claim is the paper by Rignot et al, and their analysis is based on data from 1992-2010, are they aware that if you remove the 1992 year there is probably no trend for the rest of the data? In fact, there is possibly mass balance gain as well? Would you consider an analysis robust if you toss 1 year out of 12 from the data set and this reverses the conclusion?
(With Warmists, you have to be very careful about not what they argue, but what information they leave out of the discussion…)

Will Nitschke says:
February 20, 2012 at 7:12 pm
“When a glacier is in balance or flowing at its balance velocity, net mass will remain balanced. However, when a glacier accelerates while near or at its balance velocity, the outputs resultantly increase but the inputs do not, thereby shifting the glacier regime to one of negative mass balance or net ice loss. This situation is particularly important because accelerated ice flow is the key method through which the Antarctic ice sheets incur a net ice loss. Accelerations such as these occur through two primary mechanisms. The first of which is caused by surface melt water reaching the glacial bed causing basal lubrication therefore reducing the frictional forces at the bed and thus increasing ice flow (Bell 2008).
The second mechanism refers to when the forces at the downstream terminus of a glacier or ice stream are disturbed or altered. This can occur through removing buttressing ice shelves or by shifting the glacier’s grounding line (point where glacier ice reaches floatation). The presence of an ice shelf provides a longitudinal compressive force which slows the flow of ice streams. If removal of this compressive force occurs, velocity of ice streams increase. This has been observed directly by Scambos et al (2004) and Rignot et al (2004) through both visual observations (Scambos) and radar interferometry (Rignot).
In terms of a grounding line retreat, an inland shift of the grounding line causes less backpressure through increased calving and basal melting. This process results in increased glacier velocities and subsequent inland thinning as more ice is being pulled from the accumulation zone (Bell 2008). In a warmer climate, one would expect that surface melting would increase, making the first mechanism more likely, however because of Antarctica’s climate and the omnipresence of ice shelves and calving glaciers there, the second mechanism actually dictates the ice losses from Antarctica. Evidence has already been presented which supports the theory that it is warm ocean water in West Antarctica which is in actuality enabling this second mechanism (Shepherd, Wingham and Rignot, 2002).”
Shepherd, Wingham and Rignot’s article is called “Warm ocean is eroding West Antarctic Ice Sheet” GRL 2004

@BCC:
In conclusion: This isn’t about cherry picking, this is about either misunderstanding, or choosing to misrepresent, the findings of this paper.
======================
What if the heading of the post was changed to:
“New paper: A high-resolution surface mass balance map of Antarctica suggests “no significant trend in the 1979–2010 ice sheet. Inconsistent (to date) with IPCC global climate modelling.”
Would you be happier?
Also Mr Watts could add this disclaimer:
“While most studies relating to Mass Balance of the Antarctic continent remain uncertain and it is not possible to draw significant conclusions due to a high degree of inter annual variability, it should be noted that Rignot et al (2011) suggests otherwise; however, the linear trend in that paper is sensitive to the start date of the analysis, and therefore may not be robust.”
I would argue that if the heading was changed and the disclaimer was added, it would make the post more balanced. I think it’s always a good idea to qualify claims as much as possible.

Will Nitschke:
“What if the heading of the post was changed to:
“New paper: A high-resolution surface mass balance map of Antarctica suggests “no significant trend in the 1979–2010 ice sheet. Inconsistent (to date) with IPCC global climate modelling.”
Would you be happier?”
No, because that title would be wrong. Trend in SMB is ***NOT*** the same thing as “trend in the … ice sheet.”
Ice sheets have mass. That mass, M, changes due to inputs (snow less ablation, etc., i.e. SMB), and outputs (flow of mass across the grounding line). dM/dT = SMB (expressed as GT/yr) – D (ice discharge, also GT/yr).
Direct measurements, via the GRACE satellites, show that DM/dt is negative and accelerating (see e.g. Rignot 2011). But these measurements tell you about dM/dt; they don’t (themselves) tell you about SMB and D.
Lenaerts et al measures SMB, based on regional modeling matched against empirical data. They find that d SMB / dT appears to be about zero (Rignot 2011 found a small insignificant negative trend; Lenaerts et al, 2012 shows an insignificant increase).
Meanwhile, D D/dt seems to be increasing (e.g. the discharge *rate* is increasing, so discharge is accelerating) D is “calculated from a time series of glacier velocity and ice thickness” (Rignot, 2011).
And here’s what the AR4 says on the matter (http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-6-4-1.html):
===
All studies for the 21st century project that Antarctic SMB changes will contribute negatively to sea level, owing to increasing accumulation exceeding any ablation increase (see Table 10.6). ***This tendency has not been observed*** in the average over Antarctica in reanalysis products for the last two decades (see Section 4.6.3.1)
===
*** emphasis mine
In sum: The Lenaerts paper does not contradict the findings that Antarctic ice sheets are losing mass (as indicated by the GRACE satellite DATA). Further, the Lenaerts paper does not contradict the AR4 report, which states that, while SMB is expected to increase, it hasn’t been observed to, yet.

@BBC:
You’ve basically repeated most of the points I already made, so I will focus on a couple of small things we disagree on. The problem with wanting to talk about MB instead of SMB is that AGW models make certain claims about SMB. It can’t say much about MB because the processes are not well understood in terms of measurement, modelling, etc. (Except in relation to SMB.) The change in MB is highly variable and uncertain. The paper you originally cited, covers only 12 years of data, and 11 of those 12 years don’t show much of a trend. To make matters worse, the high level of annual variability and the short time frame combined, makes any sort of linear trend extrapolation highly uncertain at best. This is why other papers that have looked at the same issue have been hesitant to draw conclusions. Plus your whole argument rests on citing this particular paper. Now, even if the paper was correct, what does it tell us about AGW? Very hard to say…
But the IPCC does reach some conclusions about SMB. It argues that there should be a positive SMB trend and that this will contribute overall, negatively, to sea level rise. The GCM’s have expectations about SMB. Which is why this matter is being discussed in this thread.
Now, the paper under discussion is interesting in the sense that it has the worst possible outcome for Warmists…
IF there was a positive SMB trend then Warmists could say, “See, this is completely consistent with the climate models. This reaffirms the IPCC’s position.”
IF there was a negative trend, you could even spin this and say, “Yeah OK the IPCC climate models got it wrong, but just that mean’s *it’s worse than we thought.*”
Instead there is no SMB trend… So Warmists don’t want to talk about this. There is nothing they can say, it’s the worst of all possible outcomes.
So let’s come back to MB. What can we say? Not much. Most papers are hesitant to draw any conclusions on trends because there is not much data there and it’s highly variable. Rignot et al. (2011) did draw a conclusion, but it looks like a fairly shaky one, since most of the MB loss looks like it happened in ’92-93 and not much has really happened since. But because the paper conflates Greenland MB with Antarctic MB, Warmists aren’t looking at the paper carefully or sceptically.

Sorry I should have wrote 18 years of data, not 12 years. Although that makes my argument stronger…

>> I wonder how many commenters here ever read the IPCC analysis:”
> Most likely no one.
It seems rather likely that most of you haven’t. Which means you don’t know what you’re arguing against, and explains why you’re fighting strawmen. You appear to be proud of your ignorance.
> The fact that the IPCC is unable to confirm or deny growth or shrinkage
Yes, but try actually *thinking* about that, instead of just writing. You’ve got into your head, somehow, the idea that the IPCC is predicting rapid surface ice loss in Antarctica. And now you realise that you’re wrong.
> http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-7-4-4.html
> Connolley appears to cite the parts of the IPCC that are convenient to his argument but doesn’t cite the parts that are inconvenient.
I was trying to cite the bits that are relevant. You’ve cited a bit about reactions of the SMB to changes in temperature, in the future. That isn’t relevant to the current observations. The hint is that chapter 10 is called “Chapter 10: Global Climate Projections”.
LC> This paper doesn’t say what you think it does people.
Nice to see that someone is awake. For the rest: SMB != MB. The hint is in the letter “S” which stands for “Surface”.
[snip]

sunsettommy says:
February 20, 2012 at 3:34 pm
//////////////////////////////////////////////
As you point out, warmer air is unlikely to cause much ice loss. Due to the high latitute the sun will always be weak. Liekwise summer will always be short. For the vast majority of the year, conditions will always remain well below freezing.
Significant ice loss could only be brought about by a warmer ocean and of course, most of Antartica is not ocean ice, but land ice.
It is therefore extremely difficult to see what mechanism could bring about large scale ice loss in Antartica.
Accordingly, it is difficult to see how there could be large sea level rise associated ith ice loss from Antartica. Predictions are wholly unrealistic.

There actually is a trend in one of the factors – melts have become less pronounced over the years. Uh oh!

Ignoring Connolley’s usual ad hominem attacks, it’s not clear to me either that he has much of a grasp of what the IPCC says on the topic of Antarctica until I pointed it out to him. Of course, it’s his right to effectively say the equivalent of, “Yeah the IPCC is not getting this right but their claims are about the future and the future is not now.” OK, yes, true. But would still be nice to have *some* empirical support detectable over the last 30 years of data even if small…?
And I’m still fascinated by the paper cited by BCC which is the basis of the claim for a massive decline in MB in Antarctica. There is only 4 years of ‘reconciled’ GRACE data there and the inter annual variability is as high as 500 Gt. By that I mean one year shows a net loss of 350 Gt. The following year shows a net gain of 150 Gt. A red line is drawn through this short time period pointing downwards (although no obvious trend appears in the actual graphed data), and the authors of the paper conclude there is a massive accelerating ice loss. After drawing this conclusion they introduce a safety net:
“For the same time period, the acceleration in mass loss from the MBM data is 15.1 ± 12 Gt/yr
2. Both estimates have a large uncertainty because of the short period of observation and the large temporal variability in SMB.”
No kidding.
In fields outside climate science – and in fact in most climate science papers I’ve read – when there is an uncertainty as large as that, you say so, and don’t draw a scary conclusion. It would be very interesting to see what one extra year of data does to their results. My suspicion would be that it would significantly change their calculated trend.

Unfortunately, in your quote from the study above, someone left out a minus sign from the actual study. How did this happen? Your quote above:
“The estimated SMB
trend, integrated over the ice sheet, equals 3+/-2 Gt/y^-2”
The actual quote from the study:
“The estimated SMB
trend, integrated over the ice sheet, equals – 3 +/-2 Gt/y^-2”
___
That little minus sign before the 3 means something, and its a shame it was lost when posted here on WUWT. It means, even within the range of error, Antarctic ice mass was declining somewhere between -5 and -1 GT/yr^2, (just as Grace satellite data showed as well).

Meanwhile Chinese researchers have concluded no unprecedented warming in China during the last 100 years when the last 2000 years were analyzed. http://earth.scichina.com:8080/sciDe/EN/abstract/abstract505198.shtml