Minds in Ablation Part Four: Minds in Ablation


Copyright © 1998, 1999 by Sean Mewhinney (df736@freenet.carleton.ca).


Minds in Ablation

Charles Ginenthal managed to convince himself that the Greenland ice sheet is melting away rapidly today. Explaining how he managed to do this is a matter for abnormal psychology. All I can do is point out the information available to him which he ignored or repressed, and show how he quotes his sources selectively to give misleading impressions.

Venture to the Arctic is a popular account of the British scientific expedition to northeast Greenland, mounted in the early fifties. Individual chapters written by members of the expedition describe their researches. Referring to a study of the mass balance by H. Lister, Ginenthal states, "Measurements on Greenland's northeastern glaciers, carried out between 1952 and 1954, showed that they were losing [and here begins his quotation] `nearly 100 gm./cm.2 averaged over the whole glacier surface for one year -- equivalent to a depth of water of nearly one metre. Since all parts of the glacier showed a greater loss of ice in one year than was compensated by accumulation of snow, the whole of the glacier is said to be in the ablation area'." He then correctly comments: "The ablated ice is replaced by ice farther in, toward the center of the Greenland ice cap." 1 But apparently he doesn't understand his own comment. Where his quotation ends, the next sentence of Lister's report continues: "At a height of 1,000 m. (3,300 ft) the total accumulation of snow during the year melted (and evaporated etc.) completely; i.e. the supply exactly balanced the wastage."

Ginenthal makes it superabundantly clear that he understands the quoted statement to mean that the whole of northeast Greenland, which he then extends to all of Greenland, was melting away at a rate of a meter a year.

Velikovsky was a master of the out-of-context quote. Velikovskian writers continue to follow his example. If you crop it judiciously, the technique is perfect for confusing the meaning of a single key word or phrase, which can then be used as the opening wedge to a massive misunderstanding. The key word here is "glacier". Ginenthal takes it to be synonymous with the ice sheet. In context, Lister's meaning is so clear that to misread him so is more in the nature of delinquency than inadvertence -- even in a fool.

In his introduction, Lister states the questions he set out to answer, including: "What is the state of the balance-sheet of glaciers that flow from the huge Greenland ice-sheet?" 2 You have to know the topography. Most of the work of the expedition was carried out at its base camp on a lake called Britannia So in Dronning Louise Land. This is an area of bare mountains surrounded by ice, about 50 miles from the sea, where glacier tongues spill between peaks and terminate on barren ground. In other words, it's on the edge of the ice sheet. The expedition set up stations here in the ablation zone on two of these glacier tongues. Lister describes them: "The Britannia Gletscher [the Danish spelling is used] is about ten miles long and six miles wide.... The Admiralty Gletscher is twenty-five miles long, [and] has an average width of two and a half miles..." 3 Maps are included. This is what Lister means by "the glacier" in Ginenthal's quotation. The detailed figures for each glacier are given in a table on page 176.

This was only half of the study. The other half was conducted far inland, where it is far higher and much colder, and there is virtually no ablation, along a traverse to Thule on the west coast. Stakes were set out at intervals to measure the depth of snow accumulation.

Extrapolating from their measurements on Britannia and Admiralty glaciers, Lister estimated ablation in all of Dronning Louise Land at 4.7 cubic kilometers water equivalent of ice per year. For the area of the inland ice sheet drained by the glaciers of this area, he estimated annual accumulation at 4.5 cubic kilometers, extrapolating from the stake measurements. He concluded: "our estimates of area, ablation, and accumulation may well be about 10 per cent in error, but they indicate that in this area of north-east Greenland a state of approximate balance exists." 4

Were these passages illegible in Ginenthal's copy of Venture to the Arctic, did he not read them, or is his brain in the ablation zone, where annual information losses exceed gains?

Then there's the Forbes Magazine story, "Pat Epps' Excellent Adventure," about the enthusiasts who melted a hole through the ice sheet and lifted out a P-38 fighter plane that crash-landed in southern Greenland in 1942. He quotes this description of ablation at the site: "In mid-summer, with the sun melting a good deal of the snowy surface, the glacier, Epps had told me, `was like a saturated sponge on a kitchen counter.' The porous snowy top held lots of water, and the excess water ran along the hard icy shelf toward the coast..." 5 Ginenthal adds: "Of course, this dripping and migration of water is occurring over the entire snow-firn layer of the Greenland glacier..." 6

Why does he think so? No map of the crash site is given, but here's the giveaway: To reach the downed airmen, a rescue team "traveled aboard an ice-breaker to the nearest shore, then trekked eight miles across the ice sheet." 7 It was only eight miles from the edge of the ice sheet. Of course there is melting there. But even so, it's not in the ablation zone. To reach the airplanes, Epps and his fellow adventurers had to dig through 80 meters of ice. Eighty meters of ice accumulated there in the 50-odd years since the war. Go figure: If this were the ablation zone, those planes would still be sitting on the surface.

"Does this melting occur... say at Thule, northwest of the island [sic], where ice is not expected to melt?", he asks. And why should it not melt at Thule? Who is it that supposedly does not expect ice to melt at Thule? Ships anchor there -- It's right on the coast!

"Icecaps in the northern hemisphere melt from the southern to the northern ends because the southern region is warmer," he asserts, ex vacuo. 8 And on the next page: "Ice melts from the top or side, downward and inward." 9 He calls the northeast coast "the coldest region of Greenland" and reasons that if there's melting there, the whole ice sheet must be melting. These things might sound reasonable off the top of one's head, but Ginenthal is making it up. It's worse than that. He uses the words "ablation zone" or "ablation area" three times in his text. He has no excuse for not knowing what it means.

I've been through all this before, in "Ice Cores and Common Sense." The late Fred Hall was an inspirational figure to Ginenthal. Velikovskians have a special inability to read a simple sentence in plain language and understand it. In his "Solar System Studies," published in Aeon, 10 Hall garbled a description of the ablation zone given by U. Laroche at a scientific congress, 11 among other things, and claimed that the Greenland ice sheet was shrinking from the top down. In an addendum to "Ice Cores and Common Sense" called "Saturnian Juvenilia," I gave this description of the ablation process in glaciers:

Loss of mass from a glacier is called "ablation". Four processes are responsible: sublimation, runoff of meltwater, evaporation, and calving of icebergs. Ablation from the Greenland ice sheet exceeds accumulation only in a narrow strip near the coast called the "ablation zone" (see Figures 1 and 2). Perhaps nine tenths of the surface area of the ice sheet lie in the "accumulation zone", where annual accumulation exceeds ablation. What little melting does take place in the accumulation zone forms a crust or trickles downward in the snow. It doesn't remain in the liquid state long enough to go far. It is carried along very slowly toward the coast by the motion of the ice beneath it. (See Fig. 3.) If the ice did not move, it would get thicker and thicker, without limit. Available information is neither complete nor accurate enough to permit a reliable estimate of the mass balance of the ice sheet as a whole.

I'm not in love with my own words, but I think this is a pretty clear and concise explanation of ablation. And I gave a picture of it. I reproduced a map from a report by Carl Benson, 12 together with a cross-section of the various concentric zones of the ice sheet, with explanatory captions. (Benson breaks the accumulation zone down further into the "soaked facies", "percolation facies", and "dry snow facies".) The boundary line between the ablation zone and the accumulation zone is the equilibrium line. It has a mean altitude of about 950 meters in Greenland 13 -- lower in the north, higher in the southwest. 14 Above the equilibrium line, accumulation exceeds ablation. Below it, the balance is reversed. Since 87% of the ice sheet is above 4,000 feet (1220 meters), 15 it is evident that most of it lies in the accumulation zone. 16 Ice builds up slowly over a large area in the interior and flows outward to the edges, where it melts or breaks away as icebergs in a few days of summer, essentially.

Ice sheets melt from the bottom up, not from the top down. Glaciologists had this figured out early in the nineteenth century. As C. Leroy Ellenberger put it, "Anyone who has skied Hawaii or Chile should have no problem understanding how high-altitude arctic ice survived... the Hypsithermal" warming. 17 Ice sheets don't melt from south to north, either. Ablation is greater in southern Greenland, but so is accumulation. You can see this from maps, too. 18

Ginenthal has the idea that the northern coast is the coldest part of Greenland. He's dead wrong. In December of 1952, the temperature at Britannia So, where Lister made his ablation measurements, averaged 46° F warmer than at the expedition's meteorological station at Northice, in the interior. 19 This is because temperature is much more closely correlated with altitude than latitude. Ginenthal could have learned that from one of his sources. He cited Robin's Climatic Record in Polar Ice Sheets 20 for the rather trivial piece of information that much of the Greenland ice sheet does not meet Robin's strict definition of a polar glacier as one where the surface never reaches melting point. The very next paragraph on that page invites him to look at a map of temperature and elevation, where "We see that temperature is primarily related to surface elevation." (See Fig. 4.) Robin's book is a good general introduction to glaciology with much useful information that would have benefited him.

Rather than rely on Ginenthal's cockup of one forty-year-old study of mass balance in one part of Greenland, it might be interesting to look at recent developments in the state of glaciologists' knowledge of the ice-sheet balance. In 1985, Reeh and Gundestrup estimated that the ice at Dye 3 in southern Greenland was thickening at a rate of 3 centimeters a year, with a range of error of plus or minus 6 centimeters. 21

They had the use of surveys of accumulation and ice flow both above and below the drill site. They noted that previous studies at various other locations, lacking precise information, had indicated larger imbalances, sometimes amounting to more than a meter a year, "in some cases positive, in others negative." 22 They add: "The suggested thickening rates of a few centimetres per year for the interior ice- sheet regions, however, do not necessarily mean that the Greenland ice sheet as a whole is at present gaining mass. Observations from the ice-sheet margin in West Greenland indicate that in general this part of the ice sheet is thinning and receding...... almost nothing is known about the mass balance of the eastern and northern parts of the ice sheet." 23 (The ice could easily be thickening in the center and receding at the margins, because both abalation and accumulation increase with higher temperatures.)

Three years later Kostecka and Whillans published a study of the balance along two east-west transects across Greenland. For the OSU transect, which passes through Dye 3 at about 65° N, they found an annual increase of 60 centimeters, plus or minus 14 cm. For the EGIG line, which passes through Summit at about 70° N, they found a steady-state balance, with an uncertainty of plus or minus 7 centimeters. 24

In 1989, Ambach noted that "Most estimates of the present mass balance of the Greenland ice sheet suggest that gains and losses are about equal." 25 And in 1991, Oerlemans expressed the opinion that "early estimates only give an idea of the characteristic mass turnover of the ice sheet, but certainly not of the sign of the net balance." 26

We are now entering an era where it will be possible to measure net mass changes over the whole ice sheet by radar altimetry from satellites. The error in individual measurements of altitude can be as much as several meters, but statistical analysis of successive passages over the same point makes it possible to detect trends. There have been two analyses of the altimetry data available from three American satellites: Zwally et al. found an annual elevation increase of 23 centimeters between 1978 and 1985 over the southern half of Greenland, 27 while Lingle et al. found no significant change between 1978 and 1987. 28 It has been questioned whether this is a real effect. 29 If it is, observations over a longer period are still needed to interpret the results. Knowing how much the surface rose or fell in a short interval does not distinguish whether the gain or loss is ice, or a short-term fluctuation in snowfall, with half the density of ice. A satellite in polar orbit will be needed to provide coverage of the whole Greenland ice sheet.

As part of its preparations for launch of a laser altimetry satellite, NASA has been conducting laser altimetry from aircraft over transects of southern Greenland. Comparison of their measurements with the earlier satellite radar data indicates a thickening of as much as 2 meters in the southwest between 1980 and 1993. 30

Quite considerable precision can be achieved, at least for a few selected locations, using global positioning system satellites. Radio receivers have recently been planted at a few sites in Greenland for mass-balance studies. 31 To avoid the problem of interpreting short-term changes in surface elevation, the receivers are buried 20 meters deep.

This brief survey should suffice to show that Ginenthal's fantasy of the ice sheet wasting away at the rate of a meter a year has no basis in fact. Now we return to that fantasy.

The Magic Figure

(In Which Ginenthal Discovers a Most Interesting Result)

This is where Ginenthal presents his calculations proving that the Greenland ice sheet must have completely melted away during the hypsithermal. Ginenthal derives a figure of 1.5 meters of ice melted away each year, which he assures us is a very conservative figure, and simply multiplies it by the 5500 years which he assigns to the hypsithermal. Since the result is greater than the thickness of the ice sheet, Ginenthal feels that he can afford to be generous, and reduces this to half a meter a year.

The first meter of Ginenthal's magic figure, of course, is Lister's measurement of ablation in Dronning Louise Land, with no allowance for snowfall. The other half a meter was lifted straight out of a passage in Petr Borisov's Can Man Change the Climate?, with no regard for the context:

It has been calculated that, as a result of the melting of the sea ice, eight times as much heat is absorbed from solar radiation by the Arctic Basin as is necessary to reduce the thickness of the continental ice at the rate of 0.5 m a year. 32

The ice he was interested in melting was sea ice, not continental ice. But the energy required (the heat of fusion) is about the same, in spite of the salt content and a lower melting point. Back in the sixties and seventies, Borisov was pushing a scheme to melt the Arctic ice pack by pumping water out through the Bering strait, in a massive hydroengineering project to improve the Siberian climate.The actual figures used by Borisov are given 73 pages later, in a table on page 108 of his book. 33 Ginenthal just slaps Lister's meter together with Borisov's half a meter, and off he goes:

If we accept these calculations as reasonable, since one reflects what was measured at Greenland, and apply them to the Greenland icecap during the hipsithermal [sic], we discover a most interesting result: the Greenland icecap would have melted away completely. 34

Ginenthal's use of this passage shows a couple of interesting things. First, he has no grasp of his sources, and often leaps from one conclusion to another without any intervening reasoning process. To get from the radiant heat absorbed by an ice-free ocean to a specific figure of melting on the Greenland ice sheet, first you have to calculate how much net energy will be transferred to the air over the Arctic basin, and how it will be distributed by atmospheric circulation. Newson and Warshaw and Rapp would seem to have done this part of the work for him, except that their results are presented as annual, not seasonal averages, but he does not refer to them again. Then you need a realistic model of accumulation and ablation in Greenland to show the effect of increased atmospheric temperatures. All the intermediate steps are missing. It's not that the specific figure of half a meter for hypsithermal melting is too high or too low; it's just completely arbitrary.

But the really funny thing about it is that if the Greenland ice sheet is melting away today at the rate of a meter a year, Ginenthal doesn't need the hypsithermal at all to do the job. All the confused, labored arguments over hypsithermal warmth, all the misrepresentations of botanical evidence are completely beside the point. You get the feeling that Ginenthal doesn't understand his own argument.

How Stable is the Ice Sheet?

Serious people have considered how the stability of the Greenland ice sheet might be affected by global warming. Interestingly, in the 1926 edition of Climate Through the Ages, Brooks wrote: "Of course, Greenland and the Antarctic continent did not become ice-free during this short period..." (the hypsithermal). 35 Once it reaches a certain elevation, a large ice sheet largely creates its own climate. Cold downdrafts ("katabatic winds") blow outward from above, cooling the margins of the ice sheet. Both accumulation and ablation increase with temperature. Throughout a considerable range of temperature, these changes more or less keep pace with each other. But beyond a certain point, ablation will outpace accumulation, and the ice sheet will shrink rapidly. It takes a long time for an ice sheet to adjust to a change in climatic regime. In recent years, computer modelling has been used by several researchers to assess the long-term effects of warming.

All of the following studies have terms to represent isostatic adjustment of the bedrock topography, geothermal heat flux, and differences in the rheology of ice of different age and temperature. The model used by Letréguilly et al. (1991) 36 has a 20-kilometer-square geographic grid and 14 vertical layers. Accumulation rates are adjusted for changes in annual temperature. Ablation is a function of summer temperatures ("positive degree days"). The time step is two years.

Letréguilly and her co-authors found that the effects of a 2° C warming on the ice sheet model were hardly detectable. With a 4-degree warming, an ice-free corridor opens up between about 65 and 66 degrees north latitude, and "the ice sheet ... splits up into two parts, one large part covering central and northern Greenland, and a much smaller ice cap over the southern mountains." 37

"The ice sheet is only moderately vulnerable to a climate warming: it would take a temperature increase of 6°, sustained over 20 000 years, to allow the ice sheet to disappear completely..... Furthermore, under present-day climatic conditions, if the ice sheet did not already exist, it would re-form on the ice-free Greenland topography." 38

Abe-Ouchi (1993) modelled a two-dimensional transect through the ice sheet along the EGIG survey line in central Greenland. The ice is assumed to flow along this line. The model has a horizontal grid of 10 to 20 kilometers, and 92 vertical layers. Time steps for ice-sheet geometry and temperature vary from 0.2 to 2 years. Ablation is a function of equilibrium-line altitude and summer temperatures.

Abe-Ouchi's model shows greater vulnerability to warming than Letréguilly's. With a "3 to 4° C increase of the summer months' free atmospheric temperature in the region of 70° N... the ice in the central part of the Greenland ice sheet rapidly disintegrates. Once the drastic retreat starts, the ice sheet will retreat toward the mountain range in East Greenland in about 10,000 years." 39 However, like Letréguilly and her collaborators, Abe-Ouchi finds that "the present Greenland ice sheet is not only a remnant of the ice-age climate but that it would even start growing in a warmer climate than the present." 40

The three-dimensional model of Fabré et al. (1995) is similar to that of Letréguilly (who is one of Fabré's collaborators), but with slightly coarser spatial and temporal resolution. It also differs in incorporating an "orographic" correction term in the representation of accumulation, which is allowed to increase with an increase in surface slope. This factor "becomes more important for climate warming when a large part or all of the ice sheet may disappear." 41 Their perturbation experiments were allowed to run for 50,000 model years. Their ice-sheet model is quite robust -- with a seven-degree C warming, the margins retreat substantially, but the ice sheet survives. But when accumulation is not allowed to increase with temperature (a deliberately unrealistic assumption) it splits into two with a three-degree warming, and virtually disappears with a warming of 5 degrees C.

Crowley and Baum (1995) do not treat ice-sheet decay at all. Their model represents a Greenland surface bare of ice, coupled to a general-circulation model of the atmosphere. The surface albedo is adjusted for various types of vegetation cover. The geographic grid is a coarse 4.5° latitude by 7.5° longitude, and the model is run for only a few years. They find that once the ice sheet is removed, the higher surface temperatures would not permit it to re-form. 42

These theoretical studies generally indicate that the ice sheet could withstand any warming it may have actually experienced during the Hypsithermal interval. Ginenthal, however, maintains that it could not have done so, and that the present Greenland ice sheet was created all at once in a matter of a few days or weeks. Which brings us to the Kerplop! Theory. But first, a word about early maps.


Notes

1. Ginenthal, the sentence following his note 59, citing H. Lister, "Glaciology (1): The Balance Sheet or The Mass Balance," in R. A. Hamilton, ed., Venture to the Arctic (Penguin, 1958), pp. 175-176.

2. Lister, op. cit., p. 168.

3. Ibid., op. cit., p. 169.

4. Ibid., op. cit., p. 188.

5. Terence Monmaney, "Pat Epps' Excellent Adventure," Forbes magazine supplement FYI (March, 1994), p. 106. (Minor errors and editorial liberties corrected.)

6. Ginenthal, "I.C.E.," Part V.

7. Montmaney, op. cit., p. 110.

8. Ginenthal, "I.C.E.," Part VI, third to last paragraph.

9. Ginenthal, "I.C.E.," Part VII.

10. Fred Hall, "Solar System Studies"(Part Two), Aeon Vol. 1, no. 4, p. 34.

11. U. Laroche, "The Greenland Hydropower as a Source of Electrolytic Hydrogen," Proceedings of the First World Hydrogen Energy Conference, Vol. 3, p. 2C-34.

12. Carl S. Benson, "Stratigraphic Studies in the Snow and Firn of the Greenland Ice Sheet," U.S. Army Corps of Engineers Snow, Ice, and Permafrost Research Establishment Research Report 70 (July, 1962), Fig. 48, "Diagenetic Facies of the Greenland Ice Sheet."

13. Cornelius J. Van der Veen, "Land Ice and Climate," in Kevin E. Trenberth, ed., Climate System Modeling (Cambridge Univ. Press, 1992), p. 438.

14. J. Oerlemans, "The Mass Balance of the Greenland Ice Sheet: Sensitivity to Climate Change as Revealed by Energy-Balance Modelling," The Holocene Vol. 1, no. 1 (1991), pp. 43, 44.

15. P. Putnins, "The Climate of Greenland," in S. Orvig, ed., Climates of the Polar Regions (Elsevier, 1970), p. 3.

16. According to Niels Reeh, 84% of the ice sheet is in the accumulation zone. See "Dynamic and Climatic History of the Greenland Ice Sheet," in R. J. Fulton, ed., Quaternary Geology of Canada and Greenland (Geological Survey of Canada, 1989), p. 797. According to Zwally, the figure is 85%. See H. Jay Zwally, "Growth of Greenland Ice Sheet: Interpretation," Science Vol. 246 (Dec. 22, 1989), p. 1591.

17. C. Leroy Ellenberger, "The Ginenthal Factor," available on the web at: http://abob.libs.uga.edu/bobk/cle/cle-talbott.txt.

18. Benson, op. cit., Fig. 30, p. 40; Reeh, in Fulton, op. cit., Fig. 14.5, p. 801; G. de Q. Robin, "General Glaciology," in Robin, ed., The Climatic Record in Polar Ice Sheets, (Cambridge Univ. Press, 1983), Fig. 4.4, p. 96.

19. R. A. Hamilton, "Meteorology," in Venture to the Arctic, p. 83.

20. Ginenthal, Part V, note 31, citing G. de Q. Robin, "Ice Sheets: Isotopes and Temperatures," in Robin, ed., The Climatic Record in Polar Ice Sheets (Cambridge Univ. Press, 1983), p. 8.

21. Niels Reeh and Niels S. Gundestrup, "Mass Balance of the Greenland Ice Sheet at Dye 3," Journal of Glaciology Vol. 31, no. 108 (1985), p. 198.

22. Ibid., op. cit., p. 199.

23. Ibid., op. cit., p. 200.

24. J. M. Kostecka and I. M. Whillans, "Mass Balance along Two Transects of the West Side of the Greenland Ice Sheet," Journal of Glaciology Vol. 34, no. 116 (1988), pp. 31-39.

25. W. Ambach, "Effects of Climatic Perturbations on the Surface-Ablation Regime of the Greenland Ice Sheet, west Greenland," Journal of Glaciology Vol. 35, no. 121 (1989), p. 315.

26. J. Oerlemans, op. cit., p. 41.

27. H. Jay Zwally, Anita C. Brenner, Judy A. Major, Robert A. Bindschadler, and James G. Marsh, "Growth of Greenland Ice Sheet: Measurement," Science Vol. 246 (Dec. 22, 1989), pp. 1587-1589, and on pp. 1589-1591 of the same issue, H. Jay Zwally, "Growth of Greenland Ice Sheet: Interpretation."

28. C. S. Lingle, A. C. Brenner, H. J. Zwally, and J. P. DiMarzio, "Multi-Year Elevation Changes Near the West Margin of the Greenland Ice Sheet from Satellite Radar Altimetry," in Proceedings of the International Conference on the Role of the Polar Regions in Global Change (Univ. of Alaska, 1991) Vol. I, pp. 35-42.

29. C. J. Van der Veen, "Interpretation of Short-Term Ice-Sheet Elevation Changes Inferred from Satellite Altimetry," Climatic Change Vol 23 (1993), pp. 383-405; Roger J. Braithwaite, "Is the Greenland Ice Sheet Getting Thicker?," guest editorial, Climatic Change Vol. 23 (1993), pp. 379-381.

30. "Program for Arctic Regional Climate Assessment," Arctic Research of the United States Vol. 10 (Spring/Summer, 1996), p. 59.

31. I. Whillans, "Mass Balance of Greenland and Antarctic Ice Sheets," Ice, no. 110 (1st issue, 1996), p. 16.

32. Ginenthal's note 50, citing Petr Borisov, Can Man Change the Climate?, (Moscow, Progress, 1973), p. 35.

33. Borisov, Table 7, p. 108. It's an estimated annual energy budget for the Arctic Ocean, at present, and in a hypothetical ice-free state. The figures are given in kilocalories per square centimeter. Ignoring all terms except those for reflected and black-body radiation, Borisov finds a gain of 38.5 kilocalories if the ice is removed. Whether this is sufficient to keep it from refreezing depends on the values of the other terms. The heat of fusion for water is about 80 calories per gram. Fifty cubic centimeters of ice weigh about 46 grams. How much heat it takes to melt it depends on the temperature of the ice. At freezing point, it takes 3680 calories. Dividing 38,500 by 8, we get 4812.5 -- enough to melt through 65 cubic centimeters of ice at freezing point, or 50 cubic centimeters at minus 24.6 degrees Celsius.

34. Ginenthal, last paragraph of Part VI.

35. C. E. P. Brooks, op. cit., (N.Y., Coleman, 1926), p. 411.

36. Anne Letréguilly, Philippe Huybrechts, and Niels Reeh, "Steady-State Characteristics of the Greenland Ice Sheet under Different Climates," Journal of Glaciology Vol. 37, no. 125 (1991), pp. 153-154.

37. Ibid., op. cit., p. 156.

38. Ayako Abe-Ouchi, "Ice-Sheet Response to Climate Changes: A Modelling Approach," Zürcher Geographische Schriften Vol 54 (1993), p. 127.

39. Ibid., op. cit., p. 79.

40. Adeline Fabré, Anne Letréguilly, Catherine Ritz and Anne Mangeney, "Greenland under Changing Climates: Sensitivity Experiments with a New Three-Dimensional Ice-Sheet Model," Annals of Glaciology Vol. 21 (1995), p. 2.

41. Thomas J. Crowley and Steven K. Baum, "Is the Greenland Ice Sheet Bistable?," Paleoceanography Vol. 10, no. 3 (June, 1995), pp. 357-363.

42. Ibid., op. cit., p. 358.


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