The very warm PDO of the last ~2 years is the main cause of the strong oscillations of the Antarctic ice extent, from the quite stable previous state of positive anomalies since 2012.
The increasing anomalies should return after the PDO goes down to neutral and negative again in about 6 months, more or less.
One thing I don’t understand though is why it got so warm, especially at the end of 2014 and beginning of this year.
A possible reason is a spike of the EUV (E10.7 index) that happened exactly during this period, which was also the highest – in the present solar cycle – since the end of 2011,
The first spike of E10.7 flux corresponds to the Sun’s N. Pole maximum, the second spike is more prominent and corresponds to the the stronger S.Pole maximum.
The magnetic NP of the Sun has been around zero micro-T since it crossed zero in 2011 (http://www.solen.info/solar/polarfields/polar.html)
This is more than 4 years of low fields, after crossing. I believe it could be an indication of the LP-effect being proved correct. The anomalous PDO+ could be an indication of chaotic behavior due to the anomalous intensity of the NS-poles of the Sun.
There are always strong winds around Antarctica, if you look at the NSIDC map for ice extent daily you’ll notice the ice moving / bulging around the continent as if pushed by a strong wind in the clockwise direction
This is normal there due to the large mass of oceans around the continent that allow the atmosphere move over the surfaced unimpeded.
I think the increased ice of recent years is due to progressive cooling of the region (the entire S Hemisphere has been cooling in recent years, specially the oceans),
The difference in 2015 with respect to previous years, since ~2011, is the strong warming of central Pacific (El NIno) that is taking its toll on the ice extent.
I believe this will cease in a few months, the extent is already not so low as a couple of months ago, but it’s not yet as high as in 2013 and 14.
… BTW looks like SH ice is again taking off big time (anomaly)
The following is an impressive graph,
No wonder the Antarctic ice is growing so steadily in recent years.
I believe it’s possible to identify a step-change in temperatures at the beginning of the present solar cycle.