Sure, i don't put "much" weight into my speculation above. Please note usage of words "may be", "probably", "seems to be" in my previous post.
Yet, there is more "behind" my speculation above. I'd explain. Please, dear reader, feel free to skip it if my bubbling doesn't interest you or you have no time for it.
See, we know that El-nino - is a massive change of heat distribution dynamics on Earth. And we know it takes significant time - months to years, - for enourmous masses of "unusually cold" or "unusually warm" water to travel around the globe (or to dissipate into "normal" - not unusually cold or warm - mass). In case of north pacific, there is that North pacific gyre (good pic of it - is
http://en.wikipedia.org/wiki/File:North_Pacific_Subtropical_Convergence_Zone.jpg ).
When i look at this picture, i see that distances involved are measured in tenths of thousands kilometers. Speeds involved are few kilometers per hour (for example, Kuroshio is said to be some 2.7 ... 3.6 kmh, and it's said that this is "fast" for a current of such a sort). Let's say average speed, then, would be 1.5 kph or so. Simple calculation for how much time unusually warm water (a result of an el-nino) would need to travel a significant portion of the gyre - would be something like this:
20000 / 1.5 / 24 / 365 = 1.52 years.
(20000 kilometers is "a significant portion of the gyre", 1.5 - is average gyre speed (purely guesswork by me).
Of course, there are different El-ninos, too. Some are "true" ones - happening mainly in eastern pacific; this means warmer water has to go nearly full circle around to reach those "Alaska" and "Bering" arrows on the picture. Relatively long time. But then there are "Modoki", too - an El-nino which is close to the central pacific, - this type could suuply warm water to high latitudes in less time, correspondedly.
Once some _part_ of "still unusually warm" water (on average, at least - and, to some degree, of course) "arrives" to places near Alaska and Bering, - it won't result in less ice cover right away, too. It takes time for ice to melt, for waters to mix (there are all sorts of "smaller side-circles" around any strong ocean current), and considering the scale, - it can't happen over-night nor even in one week, can it? The dissipation of all that extra heat will take months, possibly many months. Seasons don't wait for such processes, of course, - seasons come and go; but whatever time of the year it is, the extra heat from "last el-nino" - should still be felt. It'd slow glaciation in winter, and accelerate summer melt during summer.
Furthermore, as the Gyre transports "warmer than usual" waters closer to polar regions, - corresponding athmospheric events will also happen. More evaporation than usual, possibly stronger cyclones (on average for the duration of the effect), thus both more precipitation and also higher humidity and/or higher air temperatures, - and some part of such athmospheric events will certainly enter Arctic, i think. Stil, those events also take time to happen (may be less than "many months", but still some weeks at least, right?).
Granted, there are other factors in play, some are likely to be more potent, too. What i say is that El-nino will likely contribute in terms of summer ice melt (mainly directly or possibly via reducing winter ice growth - doesn't really matter) in some ~2 or so years from the peak of El-nino.
And since so far the strength of forming El-nino seems to be unprecedentally high - the "delayed effect" to Arctic (which is, again, is only my speculation) - might also be unprecedentally high. Especially since the balance seems to be going towards more melting even without El-nino.
