Arctic Sea Ice

ASI 2016 update 1: both sides

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Because of issues with data based on the SSMIS sensor aboard DMSP satellites, I mainly focus on higher-resolution AMSR2 data from the Japan Aerospace Exploration Agency (JAXA), as reported on the Arctic Data archive System website. I also look at other things like regional sea ice area, compactness, temperature and weather forecasts, anything of particular interest.

The animation on the right consists of NSIDC
sea ice concentration maps, one for each ASI update.

Check out the Arctic Sea Ice Graphs website (ASIG)
for daily updated graphs, maps, live webcam images, and
the Arctic Sea Ice Forum (ASIF) for detailed discussions.

May 27th 2016

After an unprecedented warm winter and an unprecedented early opening of the Beaufort Sea, the 2016 melting season isn't showing any signs of shrugging off the 'unprecedented' label. What has struck me most so far, is that unprecedented things have been happening on both the Pacific and Atlantic side of the Arctic.

I've been closely observing events in the Arctic for almost a decade now, and have been writing about them since 2010, and during that time I have gotten used to this sort of see-saw, where fast melting on one side of the Arctic would be compensated by events unfolding slowly on the other side of the Arctic. But this year is different. This year the ice pack is under attack on both sides of the Arctic.

I have written separate blog posts to describe these events (see here and here), and in weeks to come these ASI updates will provide a comprehensive overview on what is happening to the sea ice in the Arctic, and how this melting season is unfolding.

Sea ice extent (SIE)

Let's jump right into it. Here's the latest JAXA SIE graph:That gap is pretty intense. I wasn't kidding when I said 'unprecedented'. Last year - orange line - was already quite spectacular, but this year is crazy.

As commenter Jim Pettit wrote on the Arctic Sea Ice Forum earlier today:

ASI 2015 update 6: one more high

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2014 period (NSIDC has a good explanation of sea ice extent and area in their FAQ). I also look at other things like regional sea ice area, compactness, temperature and weather forecasts, anything of particular interest.

The animation on the right consists of NSIDC
sea ice concentration maps, one for each ASI update.

Check out the Arctic Sea Ice Graphs website (ASIG)
for daily updated graphs, maps, live webcam images and
the Arctic Sea Ice Forum (ASIF) for detailed discussions.

August 19th 2015

We are now entering the final weeks of the 2015 melting season. A relatively cold and cloudy start (not as cold and cloudy as the two previous rebound years) was compensated by a July that was ideal for melting. A continuous bombardment of heat and sunshine for weeks on end has caused some late melting momentum which is now keeping sea ice extent and area numbers dropping relatively evenly, despite a switch in weather conditions since the beginning of the month (see ASI 2015 update 5: late momentum).

As expected, the 2015 trend line on most graphs is hovering between top 3 years 2012, 2007 and 2011, and rebound years 2013 and 2014. It's difficult to tell how low things will end up. Melting momentum is one thing, but at this stage of the melting season weather conditions have the last word. It's compaction rather than melting that determines the final shape of the ice pack, and compaction depends on which way the winds are blowing, which in turn depend on the constellation of cyclones and anti-cyclones, or high pressure areas. See this blog post from an eternity ago, 2010, that explains how it works.

And now for the details...

Sea ice area (SIA)

Here's the latest Cryosphere Today SIA chart, to which I've added preliminary data as calculated by Wipneus:

Jenga July 2015

And thus the tradition of the ASIB alliteration of months continues. This one is a bit corny, but kind of appropriate too, so bear with me. Melt Pond May refers to the onset of melt pond formation, and Junction June is about the possible paths the melting season may follow after these two months of preconditioning. The ice pack might remain relatively stable because of a lack of preconditioning, but that balance can still be upset during July, just like a game of Jenga. It has to be an exceptional July, though, and this year's July was exceptional.

To reiterate why preconditioning is important: if the ice pack gets covered by melt ponds early on in the melting season, more solar radiation will be soaked up because melt ponds are much less reflective than ice. That way something which I call melting momentum is built up, a combination of thinned ice and warmer waters on, under and around the ice floes. This momentum can sustain relatively high melting rates, even when weather conditions aren't optimal, as we've seen during the 2011 and 2012 melting seasons. The reverse is also true. Little preconditioning, as happened in the 2013 and 2014 rebound melting seasons, causes trend lines to simply stall at some point, even when weather conditions are conducive to melting.

This melting season didn't undergo any serious preconditioning to speak of. All in all more melt ponds formed on the ice pack than in 2013 or 2014, but it started late and wasn't comparable to years with lots of preconditioning, like 2010 and 2012. It was clear early on that 2015 wouldn't be breaking any records, and the main question seemed to be whether it would end up below 2013 and 2014, or become the third rebound year in a row.

But then July came, and July was hot, as can be seen on this temperature graph made by the NSIDC's Andrew Slater (hat-tip to Chris Reynolds and his latest PIOMAS analysis):

To be able to assess the impact of this relatively high temperature anomaly we need to compare it to other years, in this case the big melters since 2006, and the two recent rebound years. I've divided July up into two halves and here's the first map for July 1st to 15th: