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Rob Dekker

Thanks Neven !
I for one am glad that the melting season started.
It will put the focus back to climate and science after a winter of arguing politics on the ASIK :o)

Rob Dekker

Sorry. That was ASIF.


While arguing politics is likely pointless, there is an excellent running record of scientific evidence presented on this blog and the ASIF which explains the condition of the Arctic in an understandable manner for most of us amateur scientists or as I may say "lay scientists." It is compilations such as these that eventually will help "sway the masses," at least IMHO.
Many thanks to Neven and everyone else who contributes to this blog and the ASIF.


Speaking of ASIF, I forgot to mention that the 2018 melting season thread has also opened there.


I've also added a bar graph to the blog post, showing total freeze for the 2006-2018 period.

John Christensen

Speaking of melting; Rob, what is the timing of your first prediction for Sept SIE?

Rob Dekker

John, my prediction method, using NH snow cover, sea ice extent, and sea ice area as predictors, is useful with data from the end of May, but statistically significant only with data from the end of June.

Sorry, I still have not found any variables that make a statistically sound prediction earlier than that.

Jim Hunt

Apart from extent it's useful to also take a look at Arctic sea ice thickness at this time of year:


[The thickness maps] reveal large areas of relatively thin sea ice in the Okhotsk and Barents Seas where the ice can now be expected to melt as quickly as it formed. There is also remarkably little sea ice in the Bering Sea for the time of year.

P.S. The 2018 NASA Operation IceBridge campaign has just started:



Hi Jim

Upon further research a sun lower than 5 degrees affects thermistor readings if without winds, I am working on the exact sun elevation.... Hope you had a chance to measure top of snow temperatures when you had some.

I naturally notice when the Arctic becomes dryer, hence colder during winter of course, but not for the sub-Arctic where the higher sun will warm the surface much quicker. So this small maximum volume is sparred from much further disaster by the drying up of the Arctic atmosphere more than 3 months late:


Despite the good small cooling news all data points towards a massive melt come September, if the late drying of atmosphere accretes more sea ice where the sun is low, it melts it where it is high, especially at the fringes of the Arctic . Dry Arctic air is a 0 sum gain at this time of the year. Now is a matter of weather, no wide spanning fog and clouds are a disaster come mid April onwards.

Kevin McKinney

Thanks for another valuable summary, Neven! I have an odd feeling about this season, but we shall see how it plays out. "Odd feelings" are quite often nothing more than that.

John Christensen

Hi Rob,

Thank you for the reply!

Noting your factors (NH snow cover, SIA and SIE), I wonder why sea ice volume wouldn't make the list of significant factors.

See 2012 vs 2013:

- Sea ice volume (SIV) equal at beginning of melting season
- April SIE higher in 2012 than 2013
- Sept. SIE much lower in 2012 than 2013

Sea ice volume or distribution of the volume might have been able to better explain the actual difference in melting.

For 2018 compared to 2016 and 2017:

- April SIE lower in 2018 than 2016 and 2017
- April SIV (PolarPortal) higher in 2018 than 2016 and 2017

The increased level of compactness/thickness of the sea ice in 2018 IMO should favor a lower level of melting and therefore also relatively higher Sept SIE, so let's see.

That said, NH snow cover will probably also be higher in 2018 compared to past couple of years, which then alternatively will explain a reduced melting..
In general, weather patterns that cause low pressures to form over the Arctic Ocean from mid-late May probably will also help retain NH snow cover, although numbers not always reflect that.

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