January 21, 2008

Antarctica Snowfall Increase

Filed under: Antarctic, Polar

The ice caps hold a special place in the cold hearts of the global warming advocates who are all too quick to insist that our ice caps are currently melting at an unprecedented rate. We suspect that they will not be particularly thrilled to learn that a paper has just appeared in Geophysical Research Letters entitled “A doubling in snow accumulation in the western Antarctic Peninsula since 1850.” The article is by scientists with the British Antarctic Survey and the Desert Research Institute in Reno, Nevada; the work was funded by the UK Natural Environment Research Council and the U.S. National Science Foundation. In case you think that the Desert Research Institute in Nevada would have little interest in Antarctica, recall from geography classes you’ve had that Antarctica receives little precipitation and is regarded by climatologists as a frozen desert.

We have covered Antarctica many times in past essays, and despite literally thousands of websites claiming that some calamity is occurring in Antarctica related to global warming, we side with the United Nations Intergovernmental Panel on Climate Change (IPCC) in this matter. Magazine covers have wonderful pictures of melting of the Antarctic, but IPCC in their 2007 report clearly states “Antarctic sea ice extent continues to show inter-annual variability and localized changes but no statistically significant average trends, consistent with the lack of warming reflected in atmospheric temperatures averaged across the region” (in fact, Antarctic sea ice extent has recently set record highs for both total areal extent as well as total extent anomaly (see here and here)). Furthermore, IPCC tells the world (and we wonder if anyone is listening) “Current global model studies project that the Antarctic ice sheet will remain too cold for widespread surface melting and is expected to gain in mass due to increased snowfall.”

Elizabeth Thomas and her two colleagues begin their article noting “Antarctic precipitation is a difficult parameter to measure directly, primarily because of problems with blowing snow. A recent synthesis of available data suggests no significant change in snowfall across the continent as a whole since the 1950s. However, proxy indicators do suggest an increase in the Peninsula.” They note “that the number of days with precipitation — based on synoptic observations of ‘present weather’ — at Faraday station, in the north-western Peninsula, increased at a rate of 12.4 days/decade between 1950–99. In addition, model data reveal an upward trend in regional precipitation for the period 1980–2004 while satellite altimeter data indicate an increase in elevation in the western Peninsula for 1992–2003, thought to be due to greater snowfall.” Notice that they are talking about more snow and more snow accumulation – in Antarctica.

Thomas et al. analyzed a medium depth ice core drilled at a high accumulation site (Gomez) on the south-western Antarctic Peninsula (73.59°S, 70.36°W, 1400 m) (see map , Figure 1). If you want the details, the core was drilled in January 2007 using an electromechanical, 104 mm diameter drill to a depth of 136 m. As seen in the figure below, the snow accumulation (measured in meters of water equivalent per year, mweq y-1), has as the title of the article suggests, been rising like a rocket. In their own words, the authors state “Annual accumulation has more than doubled in the last 150 years: the mean for 1855–1864 was 0.49 mweq y-1while for 1997–2006 it was 1.10 mweq y-1. At the beginning of the record annual accumulation is relatively stable until about 1930 when it begins to increase steadily. Following a slight reduction in accumulation in the late 1960s, the most rapid increase occurs in the latter part of the record with the mean accumulation rate from the mid-1970s onwards increasing to 0.95 mweq y-1. Note that for the post-1980 period even the lowest annual accumulation values are still greater than the highest accumulation values from the first half of the record (1855–1924).” This huge increase may be unique to the Gomez area, but other cores sites certainly show increases in accumulation as well.


Figure 1. Annual accumulation at Gomez (dashed blue) and running decadal mean accumulation at Gomez (solid blue), Dyer Plateau (red), James Ross Island (black) and ITASE01_05 (green) in meters of water equivalent per year (mweq y-1) between 1850 and 2006 (from Thomas et al., 2008)

So while we’ve heard recent reports about Antarctica losing ice, here we again find evidence to the contrary, and then some, at least in these locations. Not only is there no evidence of melting at the Gomez site, snow is accumulating there at an amazingly high rate. Clearly, this paper adds to the evidence that suggests that we simply, as of yet, do not have a firm grasp on the climate changes and their drivers that are effecting Antarctica, past, present, or, much less, future.

Reference:

Thomas, E. R., G. J. Marshall, and J. R. McConnell, 2008. A doubling in snow accumulation in the western Antarctic Peninsula since 1850. Geophysical Research Leters, 35, L01706, doi:10.1029/2007GL032529.




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