Miller et al’s (2013) study on very old dead moss emerging from beneath ice caps on Baffin Island, indicating unusual warming, must have touched a nerve with the so-called climate skeptics. I’ve previously shown that attempts by Anthony Watts and Steve McIntyre to denounce this paper were flawed. Today it is the turn of ex-geologist Don Easterbrook to bring out his one graph and embarrass himself. He does it with aplomb.
a. Miller et al. assume that the ice caps are cold-based (i.e., basal ice is frozen to the ground below) and that there is no basal sliding of the ice and no basal erosion. However, deep fiords and ice-scoured scoured bedrock in the area attest to active subglacial erosion (i.e., basal sliding rather than frozen to the ground), although most of the obvious erosion is probably related to Pleistocene glaciation. The Greenland ice sheet just across the Davis Strait at the same latitude is not frozen to its base, and the average summer temperature at Clyde (north of the sample sites) is 3°C above freezing during June, July, August, and September (Fig. 5). Summer temperatures of all of the more than half dozen weather stations along the east coast of Baffin, where the sample sites are located, are above freezing during June, July, August, and September. Thus, the Miller et al. conclusion that the small ice caps in this study are frozen to their base is highly questionable and most like not true.
I thought Easterbrook’s expertise was in glaciology, but obviously not, as this paragraph is packed with errors.
Miller et al find still-rooted dead moss and lichen with a radiocarbon date >44,000 years melting out from under the icecaps. Moss and lichens are fragile. Basal movement of glaciers grinds rocks to clay. Had there been any basal ice movement during the last <44,000 years the plants would have been ripped off their roots. Therefore the places where Miller et al find their mosses cannot have experienced basal movement of glacial ice in at least 44,000 years. Either the ice was frozen to its bed – a cold based glacier – or the ice was so thin – a snowfield – that it was not capable of movement even though its bed was not frozen. Preservation of the moss is possible under either situation, it matters not which (but the ice must have survived or the plants would have been destroyed). There is plenty of evidence to support the existence of cold-based ice on Baffin Island, for example at the Penny Ice Cap.
But back to Easterbrook’s “evidence”. There are deep fjords on Baffin Inland that were obviously formed by warm-based, erosive ice. These fjords would have been filled with thick glaciers, thick enough to insulate the bed from the winter’s cold, so geothermal heat can warm the base to melting point.
Across Baffin Bay, the Greenland Ice Sheet, is only partially frozen to bedrock. Despite the great thickness of insulating ice in the interior of the ice sheet, only where the geothermal heat flux is high is there basal melting.
Clyde has an elevation of 26.5m. The icecaps yielding old moss are all at elevations exceeding 900m. Please can someone inform Don Easterbrook about lapse rates (~5°C/km).
b. Miller et al. contend that the Laurentide Ice Sheet did not cover the area of the ice caps and that there has been no erosion since the Eemian Interglacial 120,000 years ago. However, the Laurentide Ice Sheet (LIS) extended eastward beyond this area to the coast (Fig. 1) and reconstructed ice surface elevations show the area to be close to the 1000 m and 2000 m contours, i.e., close to or above the present ice caps. The scale of the ice surface reconstructions is not detailed enough to show exactly how high the LIS surface was at the sites, but at least suggest a good possibility that the area was overridden by the LIS. The importance of this is their conclusion that the older sites have not been disturbed for 120,000 years, but to make this assertion they need to provide adequate evidence.
Easterbrook is simply unfamiliar with the literature, and does not care. It does not take much effort to find Miller et al (2002), with the delightful title “The Goldilocks dilemma: big ice, little ice, or “just-right” ice in the Eastern Canadian Arctic”. Miller et al discuss three hypotheses for the Laurentide Ice Sheet: that it covered Baffin Island completely; that it terminated inland of the mountains; and that it filled the fjords but otherwise stayed behind the coastal mountains. The evidence against the first two possibilities is strong, whereas cosmogenically dated glacial trim-lines in the fjords and other evidence support the filled-fjord hypothesis. The mountains were not over-run by the Laurentide Ice Sheets. The adequate evidence has already been published.
c. The Miller et al. assertion that the ice caps were not more than 70m thick is highly questionable. The ice caps expanded noticeably during the Little Ice Age and even if the LIS didn’t overrun the ice cap sites, the ice caps must surely have thickened, especially since the surrounding lower areas were filled with LIS ice. Thus, their contention that the ice caps could not have been more than 70 m thick is most likely not valid.
Easterbrook has either not read or not understood the Supplementary Online Materials where the estimate that the icecaps cannot exceed 70m in thickness is explained:
Maximum size of a small ice cap
The relationship between ice-cap thickness and ice-cap area for an idealized circular ice cap on a horizontal plane is given by Nye, J. F. (1952). “The mechanics of glacier flow.”J. Glaciology 2: 82-93. Assuming a basal shear stress of 1 bar, the equation collapses to h = (23x)0.5, where h is the ice thickness at distance x from the ice edge, both expressed in meters. For a circular mountain summit of 200 m radius, the maximum ice thickness is calculated to be 68 m.
If Easterbrook want to contest the maximum thickness of the icecap, he needs to engage with the methods the authors used rather than arguing from personal incredulity.
 Miller et al. claim that recent exposure of moss by melting ice proves that modern temperatures at the site were as high or higher than at any time since the moss was covered by ice and that therefore present temperatures have not been exceeded in 120,000 years. But is this necessarily true? If a block of ice is placed on the floor of a room and the thermostat is turned to 90°F, the ice will begin to melt. If the thermostat is then turned down to 40°F before all of the ice has melted, ice will continue to melt until the floor is uncovered, but to conclude that the temperature had never risen above 40°F since the floor was first covered with ice would be totally false. The same is true of the Baffin ice caps—if moss is uncovered at today’s temperatures, that doesn’t mean that higher temperatures haven’t occurred previously. Thus, the Miller et al. conclusions that“temperatures of the past century must have exceeded those of any century in more than 44 ka” and “there has been no intervening century during which warmth exceeded that of the last 100 years” are illogical and badly flawed. One wonders how this bad logic got past peer review. …
Easterbrook’s analogy is painfully flawed and divorced from any understanding of how icecaps respond to climate. In the analogy, the early 90°F conditions are far from equilibrium, the ice would have all melted had this state continued. In contrast the early-mid Holocene was long enough for the icecap to reach an equilibrium with climate. It does not need long, as it would take less than a century to go from the maximum possible thickness to the present dimensions. In the analogy, the cooler 40°F conditions immediately follow the 90°F. In reality, there were several thousand years where ice accumulation exceeded ablation and the icecaps expanded. If the last century was cool compared with the Holocene thermal maximum, the icecaps would have reached an equilibrium size, where ablation equalled accumulation that was larger than the Holocene thermal maximum icecap and Eemian mosses would not be being exposed.
 Among the 145 14C dates on exposed moss in this study are10 dates ranging in age from 23,900 to 50,700 years, leading to their conclusion that temperatures today are the hottest in >50 ka and most likely in the past 120 ka. They explain the disparity between these old dates and the multitude of young Holocene dates as due to higher elevations of the older samples so the younger sites could be exposed by melting of ice while the higher, older sites remained ice covered. But as shown by their data, this really isn’t true. Figures 1 and 3 show site M10-231v as an ‘Eemian’ site with dates ranging from 23,900 to 44,300 years. But ages at two nearby sites, M10-B226v and M10-223v, whose ages are shown as 2-3,000 and 4-5,000 years old, are higher than the site with old dates (Figure 4).
Elevation is not the only factor that determines whether an icecap melts or not. The aspect of the site will affect how much insolation and hence ablation occurs. Sites on the lee-side of icecaps or other topographic features will accumulate more snow. These other factors could easily be important enough to overcome the influence of elevation, especially when the icecaps are not in equilibrium with climate.
Summer temperature records at Clyde, north of the sample sites, show no warming from 1940 to 2009 (Fig. 5). How is it that “temperatures of the past century must have exceeded those of any century in more than 44 ka” when temperature records clearly show no warming over the past 70 years? This makes no sense at all!
If Easterbrook could show that there was no warming over 700 years, he would have a point, but as 70 years is less than a century, he doesn’t.
Finally Easterbrook reverts to his role as the man with one graph. He goes on at length about the isotope-inferred temperature reconstruction from the GISP2 ice core on Greenland. However, as Easterbrook has been told before [see comments by Nick Stokes and wheelsoc], this record stops at 95BP i.e. 1855. There is no 20th Century in this record, consequently it is absurd for Easterbrook to use it to claim that “virtually all of the period from 1500 years ago to 5000 years ago was warmer than modern temperatures” when all that can be demonstrated is that “virtually all of the period from 1500 years ago to 5000 years ago was warmer than 1855”.
Easterbrook’s post is a mix of nonsense and ignorance, garnished with his one graph.