Temperature history (and location) of various temperature stations established along the margin of Greenland, including the more than century-long histories from the stations of Godthab (Nuuk) and Ammassalik. Recent temperatures are only starting to approach those of the extended warm period from the 1920s through the 1940s (from Chylek et al., 2006).

Currently, in 2007, some glaciers along the periphery of Greenland are shrinking, but it has only been within the last couple of years that they have begun to approach, or in some cases, exceeded their recessed locations during the late-1940s and early 1950s (most Greenland glaciers advanced to a limited degree during the late-1950s through the early-1990s, during a period of cooling there).

On some glaciers, the recent recession as been dramatic, but despite the attention that these rapid changes garner in the media, they are the exception rather than the rule. For instance, the glacier that empties into the bay near Jakobshavn, on Greenland’s western coast, has been called the fastest moving glacier in the world. In recent years, it is reported to have speed up to nearly twice its previous speed and rapidly retreated. This glacier is the one that House Speaker Nancy Pelosi just visited (http://apnews.myway.com/article/20070528/D8PDMFK80.html), and it has scheduled visits by a string of global dignitaries who want to see the effects of “climate change” for themselves.

Interestingly, had Speaker Pelosi gone astray and stumbled upon the Store Glacier, a large outlet glacier lying just 100km to the north of Jakobshavn, she would have witnessed much of the same thing—a big glacier flowing off the central Greenland ice cap into a large bay, dramatically calving off large icebergs in the process. If fact, here is how a trip to Greenland’s Store glacier, via kayak, is described on a travelogue website (http://www.ushuaia.com/anglais_version/emission3/groenland/c1.htm):

On the western coast of Greenland is the Store glacier. Its source is in the very heart of the icecap and emerges in a funnel: the fjord of Uumannaq, in the bay of Disko. The icebergs and growlers pile up at the bottom of the fjord, floating slowly along with the current. Traveling through the bay in a kayak is chancy; it is necessary to push back the pieces of ice to make progress. In the midst of this distressed world, the various sculptures of striated ice, whose colors develop from dark blue to azure blue, make navigation seem surreal. Approaching the glacier, a big cracking noise is heard; it is the ice decompressing. During the Arctic summer, the Store glacier cracks and breaks apart. The sight is impressive, but it can also become dangerous: the more the icebergs melt, the greater the risk of falling pieces of ice.

This is precisely the scene that Pelosi and her entourage encountered at the end of Jakobshavn’s glacier. But there would be one major difference—the calving front of the Store glacier, instead of recessing some tens of kilometers like Jakobshavn glacier has done in recent years, has remained in virtually the same location for the past 35 or more years. Obviously, Store glacier would not well serve in the role of climate change icon, and thus receives little attention.

This same thing is true for scores of other glaciers along coastal Greenland. The full picture is that aside from a few headlining grabbing glacial recessions in recent years, a large number of Greenland’s glacier have not recessed beyond their positions established in the 1940s-1970s.

For example, there is a new and comprehensive study on the natural fluctuations of glacier activity around Disko Island, central West Greenland - not far away from Jakobshavn's glacier - that appeared to be missed by Speaker Pelosi and her science advisors. The University of Aarhus scientists, Jacob Yde and Tvis Knudesen, described the results of their study as follows:

This study assesses glacier fluctuations on Disko Island, central West Greenland, during the 20^th century. 247 glaciers of which 75 are classified as surge-type glaciers are included, representing about 95% of the glacierized area. ... [G]laciers on Disko Island have undergone a sustained period of recession throughout the 20^th century, although the MAAT [Mean Annual Air Temperature] and MSAT [Mean Summer Air Temperature] has shown no long-term trends between 1930 and 1990. ... In the 1900, many glaciers were under recession after the last advance period during the LIA (Steenstrup, 1901). Field observations in 1913 and comparison with the 1931-1933 map indicated that glacier recession continued during the first half of the 20^th century (Jost, 1940). From the early descriptions of glacier terminus positions and calculated recession rates, it seems that glacier recession rates have been higher during the first half of the 20^th century than during the second half. This supports the findings of Weidick (1968) that accelerated recession occurred between 1920 and 1940. During the period from 1953 to 1964 the majority of glacier termini remained stationary followed by a period (1964-1985) with more glaciers under recession. Towards the end of the 20^th century (1985-2005) most glaciers showed little change in length, although many still receded.

And in some cases, even the fast recessing glaciers have slowed back down. Consider this BBC story from December 2005, reporting on two rapidly retreating glaciers along Greenland’s central eastern coast (http://news.bbc.co.uk/2/hi/science/nature/4508964.stm):

Greenland glacier races to ocean

Kangerdlugssuaq Glacier on the east coast of Greenland has been clocked using GPS equipment and satellites to be flowing at a rate of 14km per year.

It is also losing mass extremely fast, with its front end retreating 5km back up its fjord this year alone. The glacier “drains” about 4% of the ice sheet, dumping tens of cubic km of fresh water in the North Atlantic. This gives it significant influence not just on global sea level rise but on the system of ocean circulation which drives through the Arctic.

“We've seen a 5km retreat of the terminus, we've see an almost 300% acceleration in the flow speed and we've seen about a 100m thinning of the glacier - all occurring in the last one or so years,” said Dr Gordon Hamilton, of the Climate Change Institute at the University of Maine.

“These are very dramatic changes.” And they are not confined to Kangerdlugssuaq. He was speaking here at the American Geophysical Union Fall Meeting. Helheim Glacier, just to the south of Kangerdlugssuaq, is exhibiting similar changed behaviour. It is flowing only slightly slower at 12km per year - the equivalent of half a football field a day.

Hamilton thinks a couple of factors may be triggering the quick melt. The observed recent increase in summer surface melting on the Greenland Ice Sheet is producing large quantities of liquid water which, if it percolates down to the base of the glacier, can lubricate its flow over rocks towards the ocean.

And if that same warming is bringing higher-temperature sea waters into contact with the front of Kangerdlugssuaq and Helheim, this could explain their rapid retreat. If other large glaciers in the region are seen to go the same way, it could begin to “pull the plug” on Greenland, said Dr Hamilton.

“The model predictions for sea level rise do not include the effects of rapid changes in ice dynamics” he added. “We're seeing now that this component might be extremely important. And what it suggests is that the predictions for both the rate and the timing for sea level rise in the next few decades will be largely underestimated.”

But, during the year and a half since the BBC ran its story, both the Helheim glacier as well as the Kangerdlugssuaq glacier have slowed down and stopped recessing. In fact, Helheim glacier has advanced in the past year such that it is currently within observed, documented, historical limits. Ian Howat and colleagues published an article in Science magazine in the spring of 2007 describing this turn of events:

They write:

The calving fronts of both glaciers appeared relatively stable from the mid-20th century until 2002, when [Helheim glacier] retreated over 7 km in 3 years. This was followed by a 5-km retreat of [Kangerdlugssuaq glacier] during the winter of 2004-5. These retreats are much greater than the 1 to 2-km seasonal fluctuations previously observed and followed a sustained period of low-elevation ice thinning. Retreats were concurrent with accelerated ice flow. This acceleration increased rates of mass loss by 28 and 15 Gt/yr at [Kangerdlugssuaq glacier] and [Helheim glacier], respectively, between 2000 and 2005, representing >40% of the ice sheet’s increase in mass loss…

[On the Kangerdlugssuaq glacier] [t]hinning moved inland between 2005 and 2006, with a peak thinning of 68 m at about 26 km, but with virtually no thinning at the front. Average thinning over the glacier during the summer of 2006 declined to near zero, with some apparent thickening in areas on the main trunk [emphasis added]…