By Joe D'Aleo
Monday, September 21, 2009
The arctic ice which bottomed out in 2007, has been bouncing back nicely the last two years. In fact the daily plots show the ice extent at the minimum this month was 23.4% greater than in 2007.
See the side-by side coverage courtesy of the Cryosphere at the University of Illinois.
Arctic ice changes are not new, there was a similar dip in the warmer 1930s-early 1950s period and according to Russian oceanographers in the 1800s. These predictable drops are due to natural factors including the sun, volcanic activity, ocean temperatures in the Atlantic and Pacific and the summer wind flow patterns, many of which are interrelated.
Willie Soon has shown a good correlation with the solar irradiance.
In a prior story I showed a good correlation of arctic temperatures with volcanic aerosols in the stratosphere. Higher levels of aerosols mean less sunlight and less summer warmth.
Atlantic water makes its way into the arctic beneath the ice from Barents Sea reaching Siberia a few years later. Pacific waters enter through the Bering Strait. See how the Pacific (PDO) and Atlantic (AMO based temperatures relate to the arctic temperatures as measured by Polyakov.
NOAA GHCN arctic temperatures show the same cyclical temperature pattern with peaks in the 1930s and early 2000s.
See in this NASA JPL story how changes in circulation affect the arctic.
Read more on the past history here.
Also recent reports of a passage of a German ship especially designed to travel in heavy ice and accompanied by two nuclear powered icebreakers had made it through the Northwest Passage. Some in the media incorrectly reported this was the first known passage through the Northwest Passage. See here why that is incorrect.
See also this fascinating history here.