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Arctic Nev

The AO is peaking quite a bit right now:

Similar to 2013 on almost the same date:

Are you watching this, John Christensen (you being the AO guy ;-) )?

Arctic Nev

Two years ago this resulted in a serious lull in ice growth (not that this means anything at this stage of the freezing season). Will be interesting to see if that happens again this year. The peaks are more sudden, whereas they were more gradual in 2013.

Cato Uticensis

Well, in accordance with the attached graph, the AO has been high for the last two weeks and in spite of that the ice extension increase has been just spectacular.

According to IJIS, today ice extension has reached y 2014 and is the second highest in the last decade.

A high AO means (among other things) the polar vortex is compact and very little heat exchange is happening between arctic and lower latitudes. In other terms, cold air is confined to the Arctic and temperatures are decreasing as a consequence - http://ocean.dmi.dk/arctic/meant80n.uk.php -

In the next few days a massive increase of ice extension is to be expected in Chukchi-Bering area based on the synoptic charts currently available. What is more, SST are lower than average in Okhotsk and in Hudson.

The only area which will be suffering is Barents, in accordance with tradition.

It's an interesting refreezing season up to now, definitely.

John Christensen

First; thank you Neven for another great PIOMAS update, even if nothing specular could be reported for October.

And yes, Arctic Nev, I certainly have noticed.
If you have been watching DMI's 60N surface pressure charts the past few days, you would notice the simultaneous LPs originating out of the North Pacific - a very intense and compact storm - as well as the North Atlantic, where the entire area between Greenland, Norway and Scotland was under a broad LP.
As Cato points out the strongly positive AO indicates a compact polar vortex, allowing ice to expand well within the boundaries of the vortex.

2013 and 2014 saw little ice expansion right at this time in comparison.

My main point in earlier posts was that a negative AO in wintertime allows the broader area defined in the AO index to be a more effective heat sink, while the broader cloudiness of a positive AO limits the heat sink effect.

The impact of AO on the sea ice depends on the extent of the ice versus the extent of the vortex, as well as certainly the specific distribution of LP and HP areas, which drives the movement of air masses.

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