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Messages - SirLurkALot

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1
Arctic sea ice / Re: "Stupid" Questions :o
« on: September 18, 2019, 02:31:14 PM »
October minimum is easy, it's due to refreeze start, lots of thin new ice takes average down. This should take place after area (not extent) minimum.
August minimum is more difficult, but I think it's due to the distribution of thicknesses in the model. When area is lost, the thinnest ice is gone. At some point the very thick ice is the bulk of the volume, and then average starts going up. Wipneus posts an internal distribution graph from time to time, you can check that graph to see if this explanation makes sense.
Ok, thanks Oren.

2
Arctic sea ice / Re: "Stupid" Questions :o
« on: September 17, 2019, 09:59:59 PM »
Just looking at Daily Average Arctic Sea Ice Thickness graph from PIOMAS.
So I get that momentum, and bottom melt cause
the minimum thickness for most years to be usually around mid October,
unlike extent, where minimum occurs a month earlier.
What I don't get is why there is a local minimum of thickness around
August, then a  'local maximum' of thickness around
mid/end September, which falls off steeply again to the global minimum.
I'd have expected any new ice formed after the extent minimum to be very thin, and
so cause the average thickness to also decrease.
Can someone put me straight on what the mechanism is for 
thickness graphs to have these double dips and peaks?
Thanks.
http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/Bpiomas_plot_daily_heff.2sst.png

3
Arctic sea ice / Re: The 2019 melting season
« on: July 10, 2019, 10:33:05 AM »
Is anyone else having trouble accessing the breman sea ice page, keep getting the security warning popping up and the image for 2019 on the Arctic sea ice graphs is blanked out.

Yes, me too.

4
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 01:54:45 PM »
...
There is also a weird band just east of the pole if anyone knows what it is?
I agree with you're analysis -  the ice melt  looks mostly very bad for 2019.
The expression "East of the pole" tripped me up for a short while.
But the feature to the right of the pole on this chart?
I'm a mathematician not a sea-ice expert, but..
The  dark vertical lines maybe the effect of compression
of more rounded areas of  lower concentration by general
drift to the right toward  Svalbard?
i had an hunch that it was related to ridging, that would be in agreement with your analysis.
On the other hand, at this latitude "low concentration" on that map is more likely to be meltponding than anything else, so either there are areas that are starting to get lower concentration in the north pole, which is a very bad sign (maybe related to the fram export), or it is maybe related to some peculiarities of the terrain that create that particular shape of melponding, like an increased elevation  that has the water accumulating at the base of it (guess that could be a consequence of ridging too), although the scale seems quite big for something so regular.
I am kinda used to the west east paradigm, as I do a lot of things with maps, but I guess in this case south would be more correct
Yes - could well be  melt-ponding, showing up as low concentration,  next to a ridge.
And you'll never be wrong if you say it's south of the pole -
of the North pole anyway.

5
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 10:29:07 AM »
...
There is also a weird band just east of the pole if anyone knows what it is?
I agree with you're analysis -  the ice melt  looks mostly very bad for 2019.
The expression "East of the pole" tripped me up for a short while.
But the feature to the right of the pole on this chart?
I'm a mathematician not a sea-ice expert, but..
The  dark vertical lines maybe the effect of compression
of more rounded areas of  lower concentration by general
drift to the right toward  Svalbard?

6
Arctic sea ice / Re: The 2019 melting season
« on: June 26, 2019, 11:51:21 AM »
Greenland sea ice extent dropping fast recently. Maybe due to the current stall in export, maybe due to the export being thinner, or both.
wipneus amsr2 uh, regional extent, jun25.
piomas(model), fram, jan1-jun15
From the gif, towards the end of the period,
it looks like there is a substantial drop near the south east coast of Greenland.
Could be due to  melting of already exported ice  to warming waters rather than a drop in export?

7
Arctic sea ice / Re: The 2019 melting season
« on: June 25, 2019, 10:33:25 PM »
The Arctic does tend to surprise us, as for me perhaps the biggest realisation has been how resilient the ice really is. Everything seems to be heading to total oblivion every year, but hey, then it just ends up more or less the same as last year.

But looking at the bigger picture, on average in the 2010s, about 2/3 of the annual max melts out, in other words, the annual melt is double the residual. In the 1980s it was closer to par, slightly more than half the annual maximum melted out.

The decadal average is falling by 1 million km2 each decade, so that gives us 40 years to reach 0 average extent.

To me these numbers imply that the ice is not likely to melt out this year, and that reaching a new record is going to be very difficult (average is 4,4 this decade, the record is 3,2) but reaching second place not so very difficult (4,1) and third place is really just average melt for this decade.
But the 40 year extrapolation  assumes that the melt will proceed in a linear fashion as we get closer to 0 extent.
Many predict that as the ice reduces, positive feedbacks such as lower albedo of open water compared to ice, easier export of less rigid ice masses  and changes to the jet stream mean that ice loss could accelerate and reach a tipping point which could mean 0 ice much sooner.

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