Tuesday, September 13, 2016

Arctic Sea Ice Has Nadired

Is "nadired" the opposite of "peaked?"

Anyway, that's what I'm going with. Arctic sea ice extent has bottomed out for the year.

JAXA:   4.02 Mkm2
NSIDC: 4.08 Mkm2

Hey, what's a difference of 60,000 km2 between friends? 

West Virginia!

(There's an old joke from where I grew up, that West Virginia would be the largest state in the Union if you flattened it out.)

For both datasets, 2016 is the 2nd-lowest extent minimum in the satellite record (1979-present), after only 2012. 

Recall this year has the lowest maximum extent (NSIDC: March 21st). But there isn't much variation in that number -- just -2.4% per decade (NSIDC data, which I'll focus on from here on out). 

Compared, the September minimum is decreasing at -12% per decade.

For the year-to-date average Arctic SIE -- through Sept. 12 -- 2016 has the lowest average extent of any recorded year, at 11.05 Mkm2

This YTD number is decreasing at -3.7% per decade.
(= overall_trend/overall_average)

Second YTD-lowest is last year, at 11.34 Mkm2. A good bit higher. 2012's value is 11.36 Mkm2.

So I would say, what we have is continued melting, though it hasn't yet reached the point where it will seriously threaten 2012's very low fluctuation due to a big summer storm in the Arctic that year.

But I remember when 2007 seemed like an unbelievable low. Though I can't find a link where I wrote about it.

The minimum extent's trend is -85,000 Mkm2/yr, which suggests it might be up to nine or so years before the 2012 minimum is...nadired. Likely, some future summer storm will send the September minimum more below the trendline by then, setting a new record low.

I guess I should put up a graph here, even though personally the numbers make more sense to me than the words or a picture (not a good quality for a science communicator):


David in Cal said...

I like that graph. It shows the dramatic reduction in Arctic sea ice extent. It's interesting that there was little reduction from 1979 - 1997 and rapid reduction from 1997 -2016, although the planet was warming throughout both periods. I don't know what that means, if anything.


OnymousGuy said...

Cold ice must first warm up to 0°C. It will remain frozen until then.

Layzej said...

Here's a longer term view. It looks like arctic summer sea ice extent was stable as far back as 1870 and started to drop after the 1950s. That chart doesn't include record year 2012 - it only goes up to 2011.