Letters to the Editor and other People Speak
Letter: Sea ice comes and sea ice goes
Andreas Schmittner has recently commented twice on declining Arctic sea ice extent, noting particularly the 2007 record low and 2008 as the second lowest. Twice Dr. Schmittner failed to note the rapidity of the 2008 ice recovery, continuing in 2009 so that Arctic sea ice extent now nearly matches the 1979-2000 average.
NASA determined the 2007 record low resulted from unusual prevailing winds blowing the Arctic ice into the Atlantic and was not the result of global warming. Dr. Schmittner claims that the main cause of sea ice melting is increasing carbon dioxide, and presumably its warming potential. Why does he believe this? Because his computer model requires it. However, the Atlantic Multidecadal Oscillation (AMO) has much more influence on sea ice than a gas that’s only 0.038 percent of the atmosphere.
NOAA’s website describes the AMO as “…an ongoing series of long-duration changes in the sea surface temperature of the North Atlantic Ocean, with cool and warm phases that may last for 20-40 years at a time … These changes are natural and have been occurring for at least the last 1,000 years.”
When the AMO index is positive the Atlantic is warmer, when it’s negative it’s cooler. The AMO index turned positive in the 1990s and declining sea ice extent correlates well with this warm phase, much more so than with CO2 levels (see chart: http://img133.imageshack.us/img133/8510/nhse72anomamo.png).
The AMO index turned negative in late 2007 and — surprise! — the decline in sea ice extent was reversed. The Arctic and Antarctic Research Institute (AARI) in Saint Petersburg, Russia, is forecasting years of increasing sea ice extent because they know the AMO cycle will continue unabated, CO2 notwithstanding.