Saturday, February 11th 2012, 11:01 AM EST
Many of the more strident reports regarding runaway global warming center on rapid ice loss from the glaciers of Greenland. During the early 2000s the Greenland Ice Sheet experienced the largest ice-mass loss since accurate instrument readings have been kept. This was largely caused by the acceleration, thinning and retreat of large outlet glaciers in West and southeast Greenland. Now a new study in Nature Geoscience confirms that ice loss from the Helheim Glacier between 2003 and 2005 was the worst recorded—at least since the last period of rapid ice loss during the late 1930s.
We have all heard the reports by climate change alarmists, claiming that the glaciers of Greenland are losing ice at an accelerating rate—a sure indication of our impending doom as a result of anthropogenic global warming. A report in the journal Nature Geoscience by Camilla S. Andresen, et al., entitled “Rapid response of Helheim Glacier in Greenland to climate variability over the past century,” has confirmed that ice lost from some glaciers did, indeed, hit a peek during the last decade, even if the causes of this change in iceflow are not known. Quoting from the report:
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The forcings behind the rapid increase in mass loss from the Greenland Ice Sheet in the early 2000s are still debated. It is unclear whether the mass loss will continue in the near future and, if so, at what rate. These uncertainties are a consequence of our limited understanding of mechanisms regulating ice-sheet variability and the response of fast-flowing outlet glaciers to climate variability. In southeast Greenland, Helheim Glacier, one of the regions largest glaciers, thinned, accelerated and retreated during the period 2003–2005 and although it has since slowed down and re-advanced, it has still not returned to its pre-acceleration flow rates.
The authors' work is based on sediments that have collected over time in the fjord below the glacier. From three core samples (see the illustration below), the researchers were able to construct a continuous history going back 120 years. By studying the debris and silt deposited in the fjord, estimations can be made about the rate of iceberg calving, and hence ice loss from the flowing ice of the glacier. As the authors' put it: “The massive diamicton facies in the cores is produced by delivery of heterogeneous debris from drifting icebergs, commonly referred to as ice-rafted debris (IRD; clay, silt, sand and pebbles), and the down-fjord diminishing input of fine mud (clay and silt) suspended in the turbid meltwater plume extending from the base of Helheim Glacier. This lithofacies interpretation is in accordance with the findings from other East Greenland fjords with marine-terminating glaciers”
The annual calving rate dominates the IRD deposition rates, but the report mostly concentrated on sand. “we propose that increased sand deposition reflects increased iceberg calving from Helheim Glacier and to a far lesser extent also from the Midgaard and Fenris glaciers,” the authors' state. The sand deposition rates from the three cores vary both in magnitude and variability, as can be seen in the figure below, taken from the paper.
After interpreting the data from all three sites, the researchers were able to create a history of ice loss for Helheim. As can be seen from the plot above, there loss of ice has varied quite a bit over the last 120 years, with a notable spike around 1939.
The reconstructed 120-year-long calving record from Helheim Glacier shows calving maxima and minima lasting 2–5 years and often bundled into longer episodes of 5–10 years. Two pronounced calving maxima are observed: one during the past 10 years, the other in the late 1930s/early 1940s. The long-term calving increase is probably due to a shift from the Little Ice Age conditions, which were characterized by low air temperatures and strong polar-water influence in the Denmark Strait region and ended after AD 1900 here.
The uncomfortable question for the climate alarmists is why was there a peek of ice loss matching today's rate before the great rise in atmospheric CO2? The answer of course is that it isn't global warming that is driving the ever changing ice loss from Greenland's glaciers. Here is how the authors' put it:
Our analysis indicates that the recent increase in calving activity observed at Helheim Glacier is not unique but that a similarly large event occurred in the late 1930s/early 1940s. These two episodes occurred at times when the temperature of the Atlantic-water source was high (positive/warm Atlantic Multi-decadal Oscillation phase) and the polar-water export was at a record low (even if fluctuating). The NAO index was also frequently negative, but not markedly more than during many of the other calving episodes. Interestingly, both episodes are characterized by record high summer temperatures since 1895 (1939, 1941 and 2003). These conditions probably resulted in increased surface and submarine melt that may have contributed to the marked mass loss from Helheim Glacier.
Here NAO is short for North Atlantic Oscillation, a climatic phenomenon in the North Atlantic Ocean characterized by fluctuations in the difference of atmospheric pressure at sea level between the Icelandic low and the Azores high. Through east-west oscillation motions of the Icelandic low and the Azores high, it controls the strength and direction of westerly winds and storm tracks across the North Atlantic and is closely related to the Arctic Oscillation (AO). The authors' conclude, “Our study provides evidence that Helheim Glacier responds to changes in atmosphere–ocean variability on timescales as short as a few years.”
Like many other natural climate patterns—the Atlantic Multidecadal Oscillation, the Pacific Decadal Oscillation, the El Niño Southern Oscillation, the Interdecadal Pacific Oscillation, etc—the NAO is not reliably periodic like the changing of the seasons, but oscillate it does. Indeed, they all do. This means that most any set of conditions caused by these large patterns has happened before and will happen again, and again. And that is the trap that the climate change cheerleaders have fallen into here: the rapid loss of ice from Greenland's glaciers was not a sign of something “unprecedented,” as is so often claimed. No, it was just another episode in our ever changing climate.
Even more troubling than the over-hyping of natural variation by lay-idiots like Al Gore is the seeming blindness that many mainstream climate scientists have for long-term climate variation. It is almost as if any change that has not happened before in a researcher's lifetime is automatically “unprecedented.” Climate science could certainly benefit from a longer term perspective.
The fact of the matter is that there are many interacting and related oscillating patterns that drive the world's climate, and science is far from being able to make accurate long-term predictions based on our current knowledge. Currently the AO has handed most of the US an amazingly mild winter, attributed to global warming by the ignorant. At the same time, parts of Europe are about to experience the coldest winter conditions in memory. There is nothing abnormal about any of this. So the next time some know-nothing blatherskite tries to tell you melting glaciers in Greenland prove global warming tell them to check out the records from 1939.
Be safe, enjoy the interglacial and stay skeptical.