December 21, 2009

A Christmas Story: Some Facts about Greenland

The wonderful Christmas season is upon us, and no Christmas story would be complete without snow. If you really like snow, Greenland is the place for you! The snow there lasts all year long and is 1,000s of feet deep in the interior – a white Christmas is guaranteed every year in this winter paradise.

Anyone following the global warming debate is aware that Greenland is a favorite topic of the apocalypse crowd – melt Greenland, sea level will rise, the ocean currents will be disrupted, and the climate of the world will be changed for thousands of years — all thanks to our inability to slow-down our greenhouse gas emissions. The rhetoric from Copenhagen recently was full of disasters involving rapid melting of Greenland. Within the past week alone, we found the headlines “Warming Hits Greenland’s Hunters” and “The Maldives and Greenland’s Ilulissat: Two Countries Experiencing Global Warming at an Alarming Rate”.

Two recent articles form the basis of our 2009 Christmas story. Under the tree is our first box of goodies, ironically from Jason Box of the Byrd Polar Research Center at Ohio State University. Box and his colleagues at Ohio State and China, with financial support from NASA, set out to reconstruct the near-surface temperature record from Greenland from 1840 to the near-present. They combined meteorological station records with a regional climate model to create a spatial reconstruction of monthly, seasonal, and annual near-surface air temperatures over Greenland.

The article is over 20 pages long in the prestigious Journal of Climate, but the key figure of interest to us is shown below. As seen in the figure, Greenland is warming over the past 25 years, no doubt about it. Let’s add to the story … Greenland is warming in all seasons over the past 25 years, Greenland has warmed by over a degree Celsius over the past 25 years, or how about this headline – Autumn temperatures soaring in Greenland?


Figure 1. Gaussian filtering of Greenland ice sheet annual 2-m temperature anomalies relative to the 1951–80 base period (from Box et al, 2009).

Of course there is another way to look at the same graph. Annual Greenland temperatures were higher in 1930 than today. The rate of warming in the past was much greater than the current rate of warming. Greenland warmed fastest before the concentration of greenhouse gases increased substantially. Greenland cooled substantially from 1930 to 1980 … during a period of greenhouse gas concentration increase. Box et al. note in their abstract that “The annual whole ice sheet 1919–32 warming trend is 33% greater in magnitude than the 1994–2007 warming.” The same graph can produce very different headlines?

Nonetheless, Box et al. provide evidence that Greenland is warming in recent decades, and that fact standing alone allows the alarmists to revisit Al Gore’s images of moulins. Warming creates melting, water flows into deep holes in the glacier (the photogenic moulins), the water lubricates the contact zone between the ice and the land below, and the glacier moves more quickly toward the sea. There is evidence of this happening, and the combination of warming, moulins, and accelerated advances of Greenland’s outlet glaciers can be used to paint yet another dangerous situation that results from the buildup of greenhouse gases.


Figure 2. One of many Greenland moulins

Our second feature article for our Christmas story is from a research team from the UK, Ohio State University, and the University of Washington; the work was funded by the UK Natural Environmental Research Council. Nick et al. (OK, for our story, Saint Nick et al.) investigated the retreat of the large Helheim Glacier which is one of Greenland’s largest outlet glaciers (we touched on this story once before). The team notes that one hypothesis for its retreat “is that warmer air temperatures increase the amount of surface meltwater reaching the glacier bed, increasing basal lubrication and the rate at which ice slides over its bed, leading to glacier acceleration, thinning and retreat”. Linking warmer air temperatures to a glacial retreat in Greenland will sell really well with the global warming advocates. However, Nick et al. state in their abstract that the changes observed with the Helheim Glacier “seem to be parallel to the warming trend in Greenland, but the mechanisms that link climate and ice dynamics are poorly understood, and current numerical models of ice sheets do not simulate these changes realistically”. Nick et al. are not going to win any awards from the climate change crowd with statements like that one in their abstract!

Nick et al. constructed a numerical model of the glacial system and in their own words, they state “From our numerical modelling, we conclude that Greenland tidewater outlet glaciers are highly sensitive to changes in their terminus boundary conditions and dynamically adjust extremely rapidly, providing an explanation for their almost synchronous behaviour to short-term fluctuations in climate. This implies that discharge changes near the glacier terminus reflect short-term dynamical adjustments, and do not provide a reliable measure for the longer-term mass balance of an ice sheet. We predict that longer-term rates of mass loss, at least for Helheim Glacier, may be less marked than observed in recent years.” The last sentence in their abstract is a dagger as they conclude “Our results imply that the recent rates of mass loss in Greenland’s outlet glaciers are transient and should not be extrapolated into the future.” Enough said.

Enjoy the holidays and continue to enjoy the information found at World Climate Report – it is a gift we provide to you throughout the year.

References:

Box, J.E., L. Yang, D.H. Bromwich, L.-S. Bai. 2009. Greenland ice sheet surface air temperature variability: 1840–2007. Journal of Climate, 22, 4029-4049.

Nick, F.M., A. Vieli, I.M. Howat, and I. Joughin. 2009. Large-scale changes in Greenland outlet glacier dynamics triggered at the terminus. Nature Geoscience, 2, 110-114.




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