I have got complained at for responding to “The impact on the stability of the Greenland ice sheet as well as on global weather patterns would likely be nearly unimaginable” with “…as for the impact on the weather, there is no reason to suppose any problem.” This in the context of the recent loss of Arctic sea ice. So maybe its worth discussing a bit.
The refs for this are the press release containing a pretty pic that is a bit misleading; the Stroeve et al paper that started it; and my somewhat dismissive take.
Stoeve et al get obs trends (for September, ie ice minimum – no-one is suggesting an ice-free *winter* Arctic), in %/decade, of -7.7 (1953-2006); -9.1 (1979-2006) and -17.9 (1995-2006). Using the last figure, you could extrapolate ice-free conditions by 2050. Using the middle one, you’d have to wait till 2100, and the first, even longer. The first figure is bigger than all the model trends, hence the headlines. But its still not very fast. For the faster second and third figures, there are models with higher trends (e.g. for 1995-2006, HadCM3 produces -19.3 and the most extreme of the NCAR CCSM3 ensemble gets -28.3).
Anyway, suppose we suppose an ice free summer Arctic and wonder what this would do to global weather. And I don’t know the answer. You could look in the GCMs, of course, but you;d have a hard time sorting out the sea ice response from everything else. In the absence of any study, and not talking about local effects (it will help the warming of Greenland, for example), I see no reason why it should be bad or good overall. For instance, will it exacerbate or ease the drought in western US? Who knows?