Arctic sea ice has a seasonal cycle, when the sun starts to set in September for the long Arctic winter night the ice starts to grow, it continues to extend outwards until the sun starts to rise in March. After that, through spring and summer the ice retreats and extent drops.
This means that about this time of the year the maximum is set. This year the maximum looked like it might have been set in late February, but after that peak growth continued and currently the maximum is on 21 March at 14.576 million (M) kmsq extent. Will this stand? Maybe.
I find the most interesting thing is to step back from one year, which is just part of an ongoing trend and look at the longer term pattern of loss around the maximum.
The largest single contributor to the decline, and the area with the strongest decline is the Atlantic sector (sectors are shown here). The Atlantic sector is comprised of the Kara, Barents, and Greenland Seas, their individual behaviour is shown below.
So the decline comes equally from the Barents and Greenland Seas.
Stepping back again to look at all sea ice in the Northern Hemisphere, I have calculated the linear trends of loss for all sectors (using Excel's Slope function). The advantage of this is that these trends sum to equal the trend of loss for all sectors combined, so I can express the percentage contribution of loss trends for sectors to the overall loss trend for all sectors combined (Northern Hemisphere Sea Ice).
So about half of the loss trend is driven by the loss trend in the Atlantic sector, with a quarter from the Pacific sector and a fifth from the Canadian sector. This pattern of greater loss in the Atlantic sector is reflected by a peculiarity of the pattern of extent across the Northern Hemisphere.
Image Source, Bremen, 15/3/16.
The ice edge in the Pacific and Candian sectors is at around 50 to 60°N, yet in the Atlantic sector it is far further north at 80°N.
In Spielhagen, et al 2011 "Enhanced Modern Heat Transfer to the Arctic by Warm Atlantic Water", the authors find that current advection of heat through the Fram Strait (between Svalbard and Greenland) is exceptional in the context of the last 2000 years. They use a site in the Fram Strait and use foraminiferal plankton from sediment cores as a proxy for temperature.
The site is shown here.
And the increase in summer temperature is seen here.
Unfortunately this is for summer temperatures, plankton at 50m depth don't thrive under ice, however the cause of the temperature increase is Anthropogenic Global Warming, and this doesn't just act in the summer. So it is reasonable to presume North Atlantic ocean warming in the winter.