Wednesday, 29 June 2016

No Early Warning of a 2016 Crash

Last May I put forward an early warning indicator for late summer sea ice crashes. What is the state of that indicator like this year?



In May last year I used 10 June to 30 June average compactness. This year, I'm using 10 June to 28 June compactness, again this is for the Peripheral Seas of the Arctic Ocean. 28 June is the latest data available as of today.


2007 and 2012 were new record low September extents by large margins, in both of those years compactness of the Peripheral Seas was at extreme low levels. That is not the case this year, on the basis of this indicator I do not consider a new record loss this year is at all likely. My April prediction was for a September 2016 extent of  4.0 to 5.3 million kmsq, my expectation is that this September will be in the lower part of that range.

7 comments:

Neven said...

Thanks for this, Chris. I've put in a link to this in the latest ASI update.

Bill Fothergill said...

Hi Chris,

Can I just check for understanding please?

If the interpretation is that when the metric exhibits a pronounced downward spike, a low September is to be expected, then 2007 & 2012 certainly bear this out.

However, if the absolute value of the metric is generally taken as an indicator for September, then the predictive skill for 2011 doesn't look too good.

Sorry if I'm being slow - it's directly proportional to the number of candles on the birthday cake.

Chris Reynolds said...

Thanks Neven,

Bill,

What made 2007 and 2012 so odd? They were massive drops from the preceding extent minimum levels in summer. This technique suggests that low compactness played a role, this might be through ice/ocean albedo, it might be through dominant pressure regimes and resultant insolation, it might be a combination.

The bottom line is in 2007 and 2012 compactness was very anomalously low in the peripheral seas, this year it isn't.

2011 was just a regular post 2007 year, 2012 wasn't. Similarly 2006 was a regular year for the 2000s, 2007 wasn't.

The absolute value of the metric isn't the issue, it's whether it's dropped abnormally low.

Bill Fothergill said...

Chris,

Thanks for clarifying that point. That's what I thought, but I could see the alternative interpretation as well.

When I look more closely at your chart, the two earlier downward spikes (both around the 0.75 mark) would therefore have given some early warning of the 1990 and 2002 September records.

Chris Reynolds said...

Bill,

Last year I did look at that whilst digging into the behaviour but can't remember what I concluded - I do recollect it hitting some years, not others. I think that as the ice has thinned it's emerged as a potentially useful predictor.

We'll see what happens this year and in future years.

Torstein Viddal said...

First half of the year is behind us and it's time to set the record straight. Some ice bloggers say 2016 won't even make it into the Top 3 lowest years for autumn minimum. To sea ice bloggers Chris Reynolds and Neven I pose this mid–year challenge: Please tell me how being 2nd lowest on record for July 3rd, being lowest on record for the longest consecutive period (90 days) on record, being lowest on record for a record number (125) of days so far, as well as being lower than any of the Top 3 in annual average extent and having lost more in annual average extent than any of the Top 3 years, to any rational human being can in any way be a telltale sign of a low melting momentum or signal a 2016 autumn minimum outside of the Top 3 scoreboard. I fear this may be just another round of wishful thinking.

http://www.wunderground.com/blog/viddaloo/annual-average-extent-26-june3-july

Chris Reynolds said...

Torsten,

It might be 2nd place this year, it is very unlikely to beat 2012.

Check out my latest post, it has a graph showing how staggeringly far ahead 2016 was in April, and how far from that position it has fallen in June.