All the global warming hysteriacs will tell you that Antarctica is melting. Yes, that evil CO2 is doing the ice in down there. I have spent a fair amount of time researching this claim. As with the Arctic, nothing is simple and to understand what is happening, it takes some sleuthing. I will first post the data in favor of snow accumulation in Antarctica. At the end, I will put a discussion of the GRACE satellite data which is a widely cited work that purports to show that the ice is thinning. I put that discussion at the bottom because it will be a bit technical. I put the data for snow accumulation at the start because anything against global warming hysteria never gets into the press. Indeed, NASA has not commented on some of the work discussed below. It doesn't fit their story line.
I ran across the following picture in Science, a peer reviewed journal. Red/brown shows areas which are increasing in ice thickness. This is determined by measuring the altitude of the ice surface.
The continent is mostly reddish, meaning that the ice surface is rising and thus presumably the ice thickness is increasing, not melting. Only on a tiny part of the continent is the ice surface falling. You can see the blue on the west coast of the Antarctic Peninsula in the first picture. But that doesn't mean that the entire Antarctic continent is losing ice. But it is events here which the press and scientists constantly use to proclaim that Antarctica is melting.
Here is a look at the time series of the surface height of Antarctica. It is rising, not falling. It is collecting more ice.
Antarctica is gaining 1.8 cm per year of ice after the corrections are made. Yet, everyone says that Antarctica is melting. How can that be? It can be because evidence doesn't matter to many of the hysteriacs. They select the areas they want the average person to look at and then they loudly proclaim that Antarctica is melting. If one only looks at the Peninsula, then it is losing mass and the Peninsula is warming. But if you look elsewhere, you see the opposite.
Given all the above it is really interesting to find out that Antarctica didn't melt much this year, in 2009, while I was down there in January, and the trend has been towards less and less melting for the past 4 years. I ran into this information on another blog which had a picture of Antarctica's snowmelt anomaly plublished at this blog
Now, if snow is growing, as the first two pictures shows, and the melting is going down, as the picture above shows it has over the past 4 years, then the conclusion has to be that more snow is piling up on Antarctica, lowering the sea level. Halleluyah, we are not going to drown the Bangladeshi's.
But, I do want to use a tool that the hysteriacs always use to support their position--the trend line. I took the values off of Tedesco's and Monaghan's chart and calculated a slope. It works out to a melt anomaly trend line of -.32 per decade. In otherwords, the entire time of the record keeping, Antarctica has been melting less and less on average every year. Sauce for the goose is sauce for the gander.
I looked up the Tedesco and Monaghan Geophysical Research Letters article and found some very interesting information. The melting index is:
". . . Antarctic snowmelt index in 2009 (e.g., the number of melting days times the area subject to melting with the year referring to the January of a reported melt season, but including melt from November and December of the previous year) set a new historical minimum for the period 1980–2009 (Figure 1). . . .The snowmelt index in 2009 was about ~17.8 million km^2 × days, below the average (1980–2008) value of about 35 million km^2 × days. Snowmelt extent in 2009 was ~690,000 km^2, also significantly smaller than the average value of ~1,294,000 km^2, being the second lowest value in the 30-year record." Marco Tedesco and Andrew J. Monaghan, “An updated Antarctic melt record through 2009 and its linkages to high-latitude and tropical climate variability,” Geophysical Research Letters, 36(2009), p. L18502
I would like the readers to note that the warming isn't happening in the white area. A close look at the scale in the picture above, zero is white on that scale. Most of Antarctica isn't melting in those regions because the temperature is always below zero! How in the hell can Antarctica melt if it is constantly below zero C and has zero melting days???? Such are the mysteries of the minds of global warming hysteriacs that they can believe that a continent which is showing melting only around the tiny edges is about to cause a catastrophe.
Secondly, I can assure you there is lots of ice on the peninsula. Below is a photo, I took of a 500 ft high glacier edge taken in January 2009. There is an almost infinite supply of ice for my margharitas!
I was in a rubber Zodiac on the water a little over a mile from that ice cliff. The scenery is grand in Antactica.
Thirdly, as mentioned above, I would also point out to people that it is hard for Antarctica to melt if the temperature is below zero. Such niceties escape the notice of the global warming hysteriacs. Below is the graph of the yearly maximum and minimum temperature for Vostok station in Antarctica. Note that the station is always below freezing and thus can't be melting, no matter what the GRACE satellite says. One can have it flow away, as glacial ice does, but one can't have it melting, for the simple reason that the temperature is below freezing
Here are more stations from East Antarctica. I have over-represented the number of stations which go above zero during the year. Notice that Mawson and Novolazarevskaya have been cooling down for a few years. They are NOT currently warming.
Finally, not only the studies above show that Antarctica is GAINING mass and lowering the sea level, there are others.
"We find that data from climate model reanalyses are not able to characterise the contemporary snowfall fluctuation with useful accuracy and our best estimate of the overall mass trend—growth of 27+/-29 Gt yr^-1 —is based on an assessment of the expected snowfall variability. Mass gains from accumulating snow, particularly on the Antarctic Peninsula and within East Antarctica, exceed the ice dynamic mass loss from West Antarctica." D. J. WINGHAM, et al, "Mass balance of the Antarctic ice sheet," Phil. Trans. R. Soc. A (2006) 364, 1627–1635, p. 1627
"We show that 72% of the Antarctic ice sheet is gaining 27+/-29 Gt yr^-1, a sink of ocean mass sufficient to lower global sea levels by 0.08 mm yr^-1." D. J. WINGHAM, et al, "Mass balance of the Antarctic ice sheet," Phil. Trans. R. Soc. A (2006) 364, 1627–1635, p. 1634
"We have used ice-flow velocity measurements from synthetic aperture radar to reassess the mass balance of the Ross Ice Streams, West Antarctica. We find strong evidence for ice-sheet growth (26.8 gigatons per year), in contrast to earlier estimates indicating a mass deficit (20.9 gigatons per year). Average thickening is equal to ~25% of the accumulation rate, with most of this growth occurring on Ice Stream C. Whillans Ice Stream, which was thought to have a significantly negative mass balance, is close to balance, reflecting its continuing slowdown. The overall positive mass balance may signal an end to the Holocene retreat of these ice streams." Ian Joughin and Slawek Tulaczyk, "Positive Mass Balance of the Ross Ice Streams, West Antarctica" Science, 295(2002), p. 476
GRACE Satellite Data
The global warming crowd will point to the GRACE satellite which is supposed to show that the entire Antarctican ice cap is losing mass. They use a technique used by young-earthers. If they can find one article that supports their position, they act as if it is a trump card for any and all other data. That is why this GRACE satellite data is used so much and unfortunately most people don't understand gravity data.
What the hysteriacs don't tell you is that with gravitational data, you can't tell where the mass change is occurring. Just so people will know that I am familiar with gravitational data, two of my published geophysical papers are gravitational papers. here and here. I have used gravity with great regularity in the search for oil and gas, especially in areas covered by thick salt deposits. We need to know the salt thickness, and use gravity to estimate it, but it isn't very accurate, and it can't be more accurate when it comes to estimating thicknesses of ice. Tiny changes in the density of the sub-salt sediments will move the base of the salt by hundreds of feet up or down. This same thing would happen with densities beneath the ice.
But, the above being said, I will cite the GRACE authors themselves stating exactly what I said above.
"GRACE (5) provides monthly estimates of Earth's global gravity field at scales of a few hundred kilometers and larger. Time variations in the gravity field can be used to determine changes in Earth_s mass distribution. GRACE mass solutions have no vertical resolution, however, and do not reveal whether a gravity variation over Antarctica is caused by a change in snow and ice on the surface, a change in atmospheric mass above Antarctica, or postglacial rebound (PGR: the viscoelastic response of the solid Earth to glacial unloading over the past several thousand years)." Isabella Velicogna and John Wahr, "Measurements of Time-Variable Gravity Show Mass Loss in Antarctica, Science, 311(2006), p. 1754
Note the bolded part. As I said above, they admit that they can't tell at what level the mass change happens so they correct the data to make it appear as if the ice is melting. What hooey.
The GRACE satellite paper was published in 2006 and Figure 2 of that paper is shown below.
If you look at the blue dots, the raw data, it doesn't look like there is much change in mass. Only after the corrections which I will describe below does it look like there is a change in ice thickness. As with the US temperatures which don't get hotter unless one 'corrects' the raw data, the raw data here doesn't show melting unless a 'correction' is made.
The gravitational field consists of the summation of the gravitational constant times each mass element divided by the square of the distance to the point of observation. Nearby mass has greater effect than far away mass. But as with any sum, you can't tell what two numbers were summed to form the total. Example: What numbers did I sum to make the number 10,567? Not only do you not know what numbers, you don't know how many numbers went into the sum. GRACE satellite observes a sum, not the numbers going into the sum. The researcher must assume his way into knowing the distribution of mass, or he must have hard data for the densities of various layers. All that is lacking in Antarctica.
To come up with a chart of ice thickness, one has to assume a model of the mass changes at all levels. Below is a chart showing the atmosphere, ice layer, crustal layer and earth mantle. Listed are all the things one must know before one can determine the ice thickness. If you don't know any of these items, you can't determine the ice thickness from gravity.
Only after you know a whole lot about everything else can you successfully estimate the thickness of the ice. While the GRACE people come out with a chart that looks oh so convincing, I can tell you that minor changes to density in the mantle beneath Antarctica will change the estimate of ice thickness drastically. I have experienced this problem trying to determine salt thickness in the Gulf of Mexico and it is exactly the same problem, mathematically speaking. One wonders how much of the correction is mere bias.
As to a post-glacial rebound, we don't know what the past ice thickness on Antarctica was or precisely when it flowed off the continent (note that I didn't say it melted). We can't possibly know that because the ice flows(not melts) and we don't have a well enough defined velocity history over the past centuries to define the past unloading of ice.
Let's hear from the scientific literature on this point. GIA = glacial isostatic uplift=post-glacial rebound.
The predicted present-day GIA uplift rates peak at 14–18 mm yr^−1 and geoid rates peak at 4–5 mm yr^−1 for two contrasting viscosity models. If the asthenosphere underlying West Antarctica has a low viscosity then the predictions could change substantially due to the extreme sensitivity to recent (past two millennia) ice mass variability. Future observations of crustal motion and gravity change will substantially improve the understanding of sub-Antarctic lithospheric and mantle rheology. Irvins and James, "Antarctic glacial isostatic adjustment: a new assessment", Antarctic Science (2005), 17:4:541-553 http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=355409
Note that they don't know the viscosity--they haven't been observing it long enough.
There are so many unknowns that to claim that we know the ice thickness and timing of melting from gravity data is ridiculous. I also can't figure out how Antarctica is melting given that central Antarctica doesn't get above zero deg C-see below.
To conclude, it appears that Antarctica is gaining ice and thus the seas must be going down. I wish the story were simpler, but, as I said, nothing in nature is simple.