The Arctic Sea Ice Outlook has just been updated for July. It”s based on a synthesis of 16 estimates which utilise a range of different projection methods. They note that there is “no indication that a return to historical levels will occur”.
The full range of estimates range from 4.0-5.2 million square kilometers, the record low in 2007 was around 4.3 million square kilometres (2008 was 4.7). Most estimates therefore fall between the record lows in 2007 and 2008, although they do note that:
There appears to be about a 20% chance of reaching a new minimum in 2009.
Arctic Sea Ice Outlook (July)
On the flip-side, based on their estimates there is a 40% chance of sea-ice coverage being greater than 2008 levels. Even more interestingly, depending on which method you select, the chance of 2009 levels setting a new record is between 5-36%...
To quote from the summary:
The two lowest estimates, 4.0 and 4.2 million square kilometers, would represent a new record minimum. All estimates are well online casino below the 1979–2007 September climatological mean value of 6.7 million square kilometers. The uncertainty / error values, from those groups that provided them, are about 0.4 million square kilometers, thus many of the values essentially overlap.
Although the majority of the responses indicate either persistent conditions or a slight increase over the 2008 sea ice extent, there appears to be about a 20% chance of reaching a new minimum in 2009. The September 2009 extent, as we track it for the rest of the summer, will depend on several factors, including the dynamics of the relatively high levels of thin, first year ice; temperature and wind conditions; and sea level pressure.
The report confirms the importance of first-year ice (FYI):
Multi-year sea ice has been reduced to such low levels that the overall September sea ice extent is largely tied to the fate of the first-year sea ice, which appears thin or with low concentrations away from the central Arctic. Depending on August conditions, much of this first-year sea ice could either melt out by September or survive the summer as a vast expanse of thin sea ice.
Accounting for their low 4 million square kilometre estimate, Rignor et al commented that:
In comparison to 2007 and 2008, there is much more first year (FY) ice in the Beaufort and Chukchi Seas in 2009, which we expect to precondition thisarea for a more extensive retreat than in 2007 and 2008.
Place your bets in the comments below, the winner gets a free trip to the PIRC office in sunny Machynlleth, mid-Wales!