Thursday, 11 April 2013



Calculated from April PIOMAS gridded data, source.

Region - all ice pack,

Month - April. Originally posted March data, but now updated to April the month of peak volume.

Volume contribution for above and below 2m thick sea ice. 2m having been chosen because above this thickness growth is mainly compression and ridging, below 2m growth is mainly thermodynamic, so the 2m split represents a good proxy for young ice (<2m) and old ice (>2m). This also shows how the volume loss has previously been from thicker older ice.

Conclusion; despite this year and the previous two having similar net volumes, the decline of the pack is continuing.

What will happen in June when the Arctic Ocean melt starts in earnest with all that thinner ice?

I'm reminded of Maslanik et al, 2007, "A younger, thinner Arctic ice cover: Increased potential for rapid, extensive sea-ice loss."

This extreme and abrupt loss of ice cover in 2007, following the extensive and sustained reduction in the oldest, thickest ice beginning in the late 1980s, is consistent with the premise that younger, thinner ice is likely to be more sensitive to melt and to area loss due to ridging and rafting, with a variety of implications for the basic nature of the Arctic Ocean... 
...the mean age and thickness of ice within the remaining multiyear ice pack have decreased due to loss of the oldest ice types, and the remaining older and thicker ice is now confined to a much smaller portion of the Arctic Ocean than in earlier years. Given this, the ice cover is likely to be increasingly susceptible to large, rapid reductions in ice extent and fractional coverage.

Source spreadsheet available here.


Anonymous said...

your figure needs a better key. what do colors mean? bar lengths? numbers?

Chris Reynolds said...

The image is just part of an Excel spreadsheet. The colours and bars are merely proportional to the range between the highest and lowest number. The numbers are clearly visible as numbers.

Anonymous said...

(Same anomymous) Think I've got it. Browsing from a phone : no access to the excel. Numbers are volume in 10^6 km^3 for <= 2m vs > 2m thickness? And "Region: ALL" and "Month: 3" are overall settings, not column headings? (that one confused me for a while!). Colors and bars are redundant views of same data as the numbers.

Chris Reynolds said...

Now I see what you mean, should have made the >2m and <2m bold and/or larger font. Sorry.

I use the colour and bars to enable me to rapidly see patterns, after a day at work writing and reading tables of numbers I get blind to them at the end of the day.

Anonymous said...

Cool sheet! If you change the colorcoding so that the two parts in the middle touch & have the same color you would see a mini ice sheet meltdown (grey icesheet in a develish red boiling ocean)

Chris Reynolds said...


I do like Excel, has been trying to get me into another language but I find Excel and VBA Macros do most of what I want to.

I was just looking at what you said. Here's something I didn't point out in the post above:

From 2007 there's a jump in ice under 2m thick to 11k km^3, note that this was before the crash of 2007. Volumes in March for above and below 2m become near equal in the following years, until 2011.

2010 was a significant volume loss year, but its effect only becomes clear afterwards, in 2011. 2011 and 2012 have under 2m thick volumes of the same order as 2007 - 2010. BUT over 2m thick volume shows a big drop.

Now 2013 - a new low for >2m thick volume and a compensatory new high for <2m thick volume.

Are we in a new regime discrete from the post 2007 regime? The near record of 2011, the record of 2012, and what of this year?

Anonymous said...

(Same Anon)


I am 100% convinced that we have past a tipping point in 2007. It is absolutly clear to me that we changed from a lineair decline into catastrophic collapse. My guess why?

- albedo effect kicking in
- slight change in Atlantic ocean current because of salinity change/temperature gradient --> NOA shift
- co2 at 400 ppm is now irreversibly higher than the safe zone of <350 ppm

I have no training in climate/polar issues, i just look at undeniable graphs people like yourself make, and make my own conlusions.

NorthPole icefree before 2016

Chris Reynolds said...

My position remains that I expect a rapid transition to a virtually sea ice free state before 2020 and possibly much sooner. Frankly I haven't thought about when the North Pole will be sea ice free.

Thanks for commenting.

Anonymous said...

Agree, maybe I sound like I would enjoy an Icefree Northpole, but it's just that we are now so close, that we'd be better of with the ice gone : Greenpeace swimming at 90 degrees North will send shockwaves over the world and then the nations of the world will finaly start to agree on taking real measures.

Or maybe they won't :
"just wait two weeks, it'll freeze and then you can walk there again, problem solved"

Chris Reynolds said...

Well I must admit that a large crash would be exciting for me. This is my hobby because it's so exciting and challenging. I'm not ashamed at all to say I find the possibility of that exciting. My reaction to it isn't going to affect the process and one may as well get something out of it rather than walking around with a furrowed brow worrying - that won't save a single cubic metre of sea ice.