Less summer sea ice = less cooling albedo = more warming = more methane release
The most recent published review of the science finds "the system may be poised to undergo rapid change" (The Arctic’s rapidly shrinking sea ice cover: A research synthesis, Julienne C. Stroeve, 2011).
The 2012 summer sea ice is a record low in volume and extent by a large margin, making it obvious we are in a post tipping point sea ice collapse situation.
A huge amount of sea ice surface (the size of West Europe) and sea ice volume have been lost already.
According to satellite data for both extent and the 2011 low was a record and for 2012 a great loss for extent and volume over one year.
The last five minima (2007-2011) are the four lowest on record. The sea ice maximum is in March and the minimum in September.
The minimum is occurring later in September, reflecting a longer melt period.
The summer sea ice extent and the sea volume over time have been steadily decreasingand are now collapsing.
The receding Arctic summer sea ice is a strong positive (bad) feedback and at the same time, the sea ice is thinning.
In 2011 an MIT sea ice model showed the ice is thinning 4 times faster than the IPCC 2007 models estimated.
NASA images dramatically show that the amount of ice that is multi-year is vanishing fast so that now almost all the sea ice extent is new ice.
The Arctic Institute has the first interactive graphs for Arctic sea ice extent and volume (December 2011). The volume is decreasing faster than the extent. The Institute says, "The accelerating loss of volume may be a more accurate indicator than the rate of decline of ice extent when attempting to predict the time horizon for an ice-free Arctic Ocean.
Ice volume data helps to put the recovery of sea ice extent since the 2007 minimum into perspective. Sea ice volume continues to decline rapidly and has occurred at an exponential rate since 1979 according to the PIOMAS retrospctive sea ice model.
If this trend persists over the coming years we could experience an ice free Arctic Ocean by the summer of 2015.
After 2001, the rate of ice loss switched to a faster rate, with another faster switch from 2007 to present making an ice-free summer Arctic look very likely by 2015. Less ice has been forming over the winter freeze, while more ice is being lost over the summer melt.
Leading Arctic expert, Professor Peter Wadhams (UK), said in 2011 (BBC) that in summer it could easily happen that we'll have an ice-free North Pole within a year or two. Later that year (Telegraph), Prof. Wadhams commented on a projection of sea ice loss, saying that it "is really showing the fall-off in ice volume is so fast that it is going to bring us to zero very quickly. 2015 is a very serious prediction and I am pretty much persuaded that that's when it will happen."
James Hansen said in 2009 that the Arctic sea ice had passed its tipping point.
The PIOMAS model finds 2011 to be a clear record in ice volume loss. The ice overall is thinning as multi-year old ice has been declining rapidly.
As shown in this NOAA animation, after each summer minumum, the amount of ice build up over winter is declining steadily, meaning a tipping point has been passed, as James Hansen says happened in 2007.
A 2011 study looking into why the sea ice loss models underestimate the actual rate of loss, found that the Arctic is losing 10% of its permanent sea ice per decade since 1980, which is 4 times faster than models project. In general, the models project the summer sea ice will last until the end of the century but it is now agreed that projection is at least 50 years out. Direct records from Canada (Statistics Canada, December 2011) show the same and more. The largest decline is in the Northern Labrador Sea at a rate of almost 600 square miles or 17 percent per decade, Hudson Strait down 16 percent per decade, and Davis Strait down 14 percent.
When will there be no summer sea ice in the Arctic?
What we really need to know is how fast summer sea ice surface albedo is being lost. From the PIOMAS volume loss, it certainly can be seen that the summer sea ice is on a heading to vanish by 2015 or even 2013.
Why is the summer sea ice melting away so rapidly?
The reason for the huge error in the model projections is multiple positive feedbacks.
The latest 2011 research by C. Kinnard suggests it is more complicated. "Arctic sea ice extent is now more than two million square kilometres less than it was in the late twentieth century, with important consequences for the climate, the ocean.... Observations show a more or less continuous decline for the past four or five decades.... Both the duration and magnitude of the current decline in sea ice seem to be unprecedented for the past 1,450 years.... Enhanced advection of warm Atlantic water to the Arctic seems to be the main factor driving the decline of sea ice extent on multidecadal timescales, and may result from nonlinear feedbacks between sea ice and the Atlantic meridional overturning circulation. These results reinforce the assertion that sea ice is an active component of Arctic climate variability."
Rapid Arctic surface warming, loss of Arctic albedo, melting of Arctic land ice and change in Arctic ocean currents have set up a complex positive feedback process causing the Arctic to lose sea ice from above and below at an increasing rate.
NASA has excellent videos explaining Arctic sea ice.
NASA has excellent videos explaining Arctic sea ice (see box to right)
NSIDC Daily sea ice
The Cryosphere Today
Oceans North Pew Environment
The Arctic Institute
Ocean North Sea ice minimum map slide presentation 2007-2011