Antarctic & Arctic News 1/26/09

A study was published in last Thursday’s issue of Nature and was covered in this MSNBC article.  It examined temperature trends across Antartica.  The continent as a whole has seen its average annual temperature rise 1F since 1957.  If Western Antarctica is contrasted with Eastern Antarctica, a very dramatic warming comes through: West Antarctica is 20F warmer and has warmed at twice the rate that East Antarctica has.  Previously, significant warming was noted for just the Antarctic Peninsula.  West Antarctica covers much more land surface than just the Peninsula.

The ozone hole is one cause for East Antarctica’s slower warming.  The hole influences the polar vortex, which distributes warm and cool air around the Antarctic Circle.  Cooler air has been maintained over East Antarctica since the 1970s than would have been the case without it.  Efforts in the late-20th century to stop destroying the ozone layer will continue to bear fruit throughout the remainder of the 21st century.  As the hole closes, the polar vortex will shift with it.  East Antarctica should begin experiencing more warming as the century goes on.

Very large ice sheets have broken off from Antarctica in recent years.  The rate at which the sheets are moving toward the ocean has accelerated, as they have in Greenland.  The Wilkins Ice Sheet is hanging on by a very tenuous piece of ice and should be the next sheet to calve.  These events are likely to increase in magnitude and frequency in the near-term.  Ice in West Antarctica rests below sea level.  If its melt increases, which wouldn’t take much more warming than has already occurred and is well within climate model projections, it will find its way to the oceans, rising sea levels.  It won’t take much sea level rise to significantly alter how coastal residents live.  A rise of only a few inches from current levels will impact millions of people worldwide.

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The Arctic is experiencing its third instance of very little to no ice growth since its minimum extent back in September:

In each instance prior to this, areal extent grew at climatologically normal rates.  Similar signals can be seen in the 2006-2007 data.  The progression of weather systems across the arctic is of course responsible for the temporary lack of growth.  I would say that it is unlikely that areal extent will match the climatological average this winter.  Conditions and this time series indicates to me that this winter is closer to the 2006-2007 winter than the climatological winter.  Maximum extent will be reached in approximately seven weeks’ time.  Then, the 2009 melt season is on.  What will things look like come September?

Recent Antarctic Cooling and Future Antarctic Warming

One fantasy climate change deniers and delayers have latched onto is that Antarctic cooling proves climate change in the form of global warming isn’t occurring. Their arguments noted that Arctic melting and Antarctic freezing of water wouldn’t change sea levels, etc. Which isn’t as true as they’d like it to be: sea levels rose throughout the 20th century and have continued to do so this century. In addition, warming has occurred at the edges of the Antarctic peninsula, resulting in the breakup of very large ice sheets that have acted as a bottleneck for ice flows from the higher peninsula.

A new research paper (by actual scientists, btw) proposes a rationale for cooling in the Antarctic interior and how that cooling might be nearing an end. The cause of cold air maintenance: the ozone hole. The hole’s formation every austral spring has kept the interior cold because it decreases the thickness of the stratosphere. Less ultraviolet light is absorbed, circulations are thus set up in a way that allows temperatures to stay cooler than they otherwise would, especially in the presence of the increased greenhouse gas concentrations.

Because of the ban on chlorofluorocarbons, ozone in the Southern Hemisphere isn’t being broken down as much and ozone concentrations are forecasted to slowly recover this century. As they do so, they will increase the thickness of the stratosphere and absorb more ultraviolet light. That’s mostly a good thing as far as reducing the risk of damaging DNA in life forms. However, circulation patterns are also forecasted to completely reverse. Cold air would no longer be trapped over the Antarctic peninsula. In fact, as far as the Southern Hemisphere goes, Australia could get even warmer and South America wetter if patterns shift as expected.

The authors made use of a chemistry climate model, which is different than the general circulation models used in the Intergovernmental Panel on Climate Change’s recent work. Those GCMs need to have this and other recently researched items included so that more comprehensive analyses can be made. If the CCM results come to pass, the 21st century could experience rapid warming and ice loss at both poles.