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551
The August poll is now out.

552
This poll will run for 10 days. You can change your vote.

PIOMAS volume minima for previous years:
Year --- Min (km3)
1979 16900
1980 16100
1981 12600
1982 13400
1983 15100
1984 14500
1985 14500
1986 15900
1987 15200
1988 14900
1989 14600
1990 13700
1991 13500
1992 14900
1993 12200
1994 13600
1995 11200
1996 13700
1997 13200
1998 11500
1999 10900
2000 11000
2001 12200
2002 10800
2003 10200
2004  9900
2005  9200
2006  9000
2007  6500
2008  7100
2009  6800
2010  4600
2011  4300
2012  3700
2013  5400



Daily volume plots by year...

(Plot and link courtesy of Wipneus.)

See this thread and post for the thickness graphs of July 2013 and 2014 and the difference (also supplied by Wipneus).

This thread has the equivalent poll for last month: July 2014.

553
Arctic sea ice / Re: Latest PIOMAS update (August)
« on: August 05, 2014, 10:23:49 AM »
Fascinating! Thanks, Wipneus!



The volume has split right away upwards from 2013 and is now hanging out with 2009 and 2007!



It's going to take a lot of melt in the next month or so to get back to the post-2009 years at minimum. Otherwise, we will end up back around the minimum volume levels of the 2007-2009 years!

554
Polling has closed now.


Forty-nine people voted and the median bin chosen for this month's poll, taken in July 2014, was "between 5000 and 5250 km^3".


That is three bins and 750 km^3 higher than the median bin for the poll for the month before, June 2014.

555
About a day to go in the poll.


I went with "Between 5250 and 5500 km3" - the same bin as the 2013 result.

That is just from eye-balling the curves in Wipneus' plot of the OP and noting that the June volume was several hundred km^3 higher than 2013 but that 2013 appeared as a poor melt year from here on in when compared to other recent years.


So it appears that we will end close to the 2013 minimum value of 5400 km^3.


My central value and 1-sigma uncertainty for minimum volume is (5400 +/- 800) km^3.

556
Arctic sea ice / Re: Latest PIOMAS update (July)
« on: July 10, 2014, 08:04:55 AM »
Wipneus, so is that last plot the thickness change for: (June 2014 - May2014) - (same for 2013)?



I recall you asking for suggestions for the plot title; you could indicate the formula in the title...


"PIOMAS ice thickness trend: (June2014-May2014)-(June2013-May2013)".



Another option might be to write the formula on the legend.


"ice thickness change [m]: (June2014-May2014)-(June2013-May2013)".

557
The median bin chosen for this month's poll, taken in June 2014, was "between 4250 and 4500 km3".



A new poll and thread is up now for the next month: July 2014.

558
This poll will run for 10 days. You can change your vote.

PIOMAS volume minima for previous years:
Year --- Min (km3)
1979 16900
1980 16100
1981 12600
1982 13400
1983 15100
1984 14500
1985 14500
1986 15900
1987 15200
1988 14900
1989 14600
1990 13700
1991 13500
1992 14900
1993 12200
1994 13600
1995 11200
1996 13700
1997 13200
1998 11500
1999 10900
2000 11000
2001 12200
2002 10800
2003 10200
2004  9900
2005  9200
2006  9000
2007  6500
2008  7100
2009  6800
2010  4600
2011  4300
2012  3700
2013  5400



Daily volume plots by year...

(Plot and link courtesy of Wipneus.)

See this thread and post for the thickness graphs of June 2013 and 2014 and the difference (also supplied by Wipneus).

This thread has the equivalent poll for last month: June 2014.

559
So much depends on the weather (mainly) and the currents this month, July, and next month, August, that I simply repeated last month's value and sigma...

This early, I just took the 2012 and 2013 values as minus and plus one sigma, respectively.

So 4.49 +/- 0.86 million square kilometres.

That falls within the "4.25-4.50" bin.

Those 2 years might be considered outliers - 2012 with favourable melt conditions, 2013 the opposite - but I consider there is enough room for unforeseen systematic changes for them to each be at only 1 sigma from the central value.


560
OSMM, yes, I will be happy to do it for July once the June data is released, thanks for asking.

561
Policy and solutions / Re: Renewables Reach a Tipping Point...
« on: June 26, 2014, 10:48:34 AM »
...I just wanted to make sure you had read the FAQ, and not dismissed it too quickly. Like I said, there have been many years and several teams working on this since it was first critiqued several years ago.

Don't worry, I'm also quick at dismissing perpetual motion machines, and there are plenty of people working on those as well.



OK, I looked on their theory page...

http://emdrive.com/principle.html
Quote
The inevitable objection raised, is that the apparently closed system produced by this arrangement cannot result in an output force, but will merely produce strain within the waveguide walls. However, this ignores Einstein’s Special Law of Relativity in which separate frames of reference have to be applied at velocities approaching the speed of light. Thus the system of EM wave and waveguide can be regarded as an open system, with the EM wave and the waveguide having separate frames of reference.

That is poppycock, presumably intended for those unfamiliar with special relativity. People analyse relativistic systems all the time using a single frame of reference.


And then the claim that their method of relativistic analysis somehow makes it an open system is ridiculous.


Momentum is conserved, component by component, in any (inertial) reference frame.

They can pump up the EM energy inside the cavity all they want - the cavity won't start shooting off in one direction without something else shooting off from it in one or more other directions.



It's not even a clever fraud.


This EmDrive is mumbo jumbo, voodoo science, ...

562
Policy and solutions / Re: Renewables Reach a Tipping Point...
« on: June 26, 2014, 02:57:07 AM »
Jonthed,

That EMdrive is rubbish, based on your first link.

Quote
Shawyer aimed to develop an EmDrive: a closed, conical container which, when filled with resonating microwaves, experiences a net thrust towards the wide end. It seems to violate of the law of conservation of momentum, implied by Newton, which says that no closed system can have a net thrust. However, Shawyer says net thrust occurs because the microwaves have a group velocity which is greater in one direction than the other and Einstein's relativity comes into play. Group velocity, the speed of a collection of electromagnetic waves, is a tricky business -- a pulse of light can even have a group velocity which is greater than the speed of light -- but can it really cause net thrust?

Einstein's relativity doesn't save it because momentum is conserved in relativistic systems as well.

No, a closed system cannot sustain net thrust, no matter what is inside it.

563
Arctic sea ice / Re: 2014 sea ice area and extent data
« on: June 21, 2014, 02:11:43 AM »
... Comments on improving usability are welcome. ...


Main comment: love your work!


Those regional area and extent graphs are superb. They show the 'state of play' relative to previous years almost at a glance.


 The overall area and extent numbers are made less relevant for my tastes by having components from regions where there will be little or no ice left at the minimum. Come September, the CAB will largely determine how this year will rank and the graphs show that clearly.


Therefore, the only minor change I would suggest if it is easy to do would be to extend the "Arctic Basin" y-axis down to zero like the others. (Who knows, the ice might be heading down there in the not-too-distant future.)


Thanks for your efforts, Wipneus. Your 'home brew' thread is often the first one I check when coming onto this forum.


564
Arctic sea ice / Re: The 2014 Melting Season
« on: June 13, 2014, 01:24:03 PM »
...Classic land to arctic torch.


Surely the sun is a better torch than the wind in June and July?


Near the Summer solstice, my instinct is to look at high pressure over the CAB - presumably bringing clear skies - as the best predictor of enhanced ice loss to follow.


Fair?

565
Thanks OSweetMrMath, much appreciated. I have updated the volume numbers for previous years given in the opening post.

Since the changes are substantial for recent years I HAVE RESET THE VOTING.


Apologies for having used the outdated figures and  so requiring people to recast their vote.

566
Hope this is OK, Neven?

This poll will run for 10 days. You can change your vote.

PIOMAS volume minima for previous years:
Year --- Min (km3)
1979 16900
1980 16100
1981 12600
1982 13400
1983 15100
1984 14500
1985 14500
1986 15900
1987 15200
1988 14900
1989 14600
1990 13700
1991 13500
1992 14900
1993 12200
1994 13600
1995 11200
1996 13700
1997 13200
1998 11500
1999 10900
2000 11000
2001 12200
2002 10800
2003 10200
2004  9900
2005  9200
2006  9000
2007  6500
2008  7100
2009  6800
2010  4600
2011  4300
2012  3700
2013  5400
(Revised values courtesy of OSweetMrMath, posted on 12 June 2014. And reset the voting.)



Daily volume plots by year...

(Plot and link courtesy of Wipneus.)

567
This early, I just took the 2012 and 2013 values as minus and plus one sigma, respectively.

So 2.89 +/- 0.66 million square kilometres.

That falls within the "2.75-3.00" bin.

568
This early, I just took the 2012 and 2013 values as minus and plus one sigma, respectively.

So 4.49 +/- 0.86 million square kilometres.

That falls within the "4.25-4.50" bin.

569
Arctic sea ice / Re: IJIS/JAXA
« on: March 24, 2014, 08:59:45 AM »
Tor, that is a good question and something I have wondered myself. In fact, I have several questions, particularly about the Winter as snow is an excellent insulator...

How much of a role does it play in retarding the growth of ice thickness over the Winter?

What is the year-to-year variation in that?

Is there a trend over the years?

Is it too cold over the Winter for much snow to fall, given that cold air can't carry much moisture?

Can enough snow fall on ice by early in the Winter to essentially block growth from then on in those places?

If snow falls, does it tend to become hard-packed and stay in place as an effective insulator, or does it instead get blown around into localised drifts?


And mainly to repeat Tor's question: how important is snow fall overall, relative to other physical effects, in the amount of ice growth and its variation?




570
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 15, 2014, 12:34:11 AM »
Thanks for these plots, Wipneus and Chris. Very interesting and much appreciated!   :D

571
Arctic sea ice / Re: Predicting PIOMAS Max volume 2014
« on: March 01, 2014, 02:36:18 AM »
24.0 +- 0.7 thousand cubic kilometres, with one sigma confidence limits.

That is, about a 2/3 probability of being between 23.3 and 24.7 thousand cubic kilometres.


This is just from eyeballing Wipneus' volume plot vs. time, which currently goes up to the end of January 2014. I haven't read anything to improve much on that or to convince that the rise from the end of January this year will be significantly biased one way or the other from those of recent years.


That prediction was a bit of fun and very easy to do as it takes advantage of a lot of work from others. Thanks to the likes of Wipneus and Chris Reynolds who present the data in convenient form and thanks especially to the scientists and technicians who have collected and analysed the data and made it available.


572
Policy and solutions / Re: Renewables Reach a Tipping Point...
« on: January 20, 2014, 11:41:49 AM »
Johnm, thank you for posting that blog post from "the Druid". However, I find it unconvincing, relying as it does on precise numerical comparisons of energy return on energy invested (EROEI). Furthermore, references aren't provided for most of the stated EROEI values.


For the example of solar PV, the Druid says...

"According to best current estimates, the EROEI needed to sustain an industrial civilization of any kind is somewhere between 10 and 12; according to most other calculations—leaving out the optimistic estimates being circulated by solar promoters as sales pitches—the EROEI of large scale solar photovoltaic systems comes in between 8 and 9 ... [so] the energy return from solar PV isn’t high enough to support the kind of industrial system needed to manufacture and maintain solar PV."


And similarly for wind power...

"...estimates of the EROEI of windpower cluster around 9, which again is too little to support a society that can build and maintain wind turbines."


  The first obvious question concerns the rigour and true uncertainty in the unsourced estimates for "the EROEI needed to sustain an industrial civilization". With what confidence can one model that, or place constraints, for an as-yet unknown future technological state? Can it really be boxed in to within plus-or-minus 10%, as claimed? (Namely, 11 +- 1).


  And that matters, as the EROEI values quoted for today's renewable technologies are close to that: 8 or 9 for PV (though with one study giving much lower), and 9 for wind.


  The pessimistic conclusion of the article hinges largely on the above numerical comparison.


  I am more accepting of the further argument that is made only for wind power - notably not for solar -  that the size of the wind resource might be too small to supply 100% of the world's energy needs.

  It has to be wondered why the equivalent presentation isn't made for solar where, in contrast, the amount of energy available is easily large enough at least in principle. Enough solar energy falls on the world's deserts that collecting over only around one percent of their area could supply the world's entire energy needs, as was pointed out as early as before World War One by solar thermal electricity pioneer and visionary Frank Schuman(n?) - see http://en.wikipedia.org/wiki/Frank_Shuman, and Google for further information on this fascinating person and his achievements.


  The relative size of the solar and wind sources is unsurprising given that the wind is itself largely driven by solar energy. The extra energy conversion to mechanical energy for wind makes it entirely sensible for the harvestable wind resource to be, say, around three orders of magnitude down on its driving solar resource.





So in summary I would argue that the solar energy resource is easily large enough to sustainably supply our future on timescales of decades and centuries, even on its own. The Druid's argument to allegedly exclude this scenario, which is based on a fine balance of EROIE calculations, lacks force.


  Personally I am optimistic on a sustainable energy future, perhaps involving some growing pains but eventually with at least a comparatively high standard of living to today. The largest contributing energy source will presumably be solar energy.








573
Wipneus, on another thread, provides the minimum as 4942 km3:

Updated, monthly graphs are in the top post.

The minimum 2013 value was 4.942 [1000 km3] at September 7.

Yearly minimum fit to exponential trend:



Yearly minimum fit to linear trend:



Yearly minimum fit to Gomperts trend:



574
Arctic sea ice / Re: NSIDC 2013 Arctic SIE September minimum: August poll
« on: October 04, 2013, 07:19:57 AM »
Diablo,

  Is the lower part of their Figure 5 not what you were seeking...?


575
Arctic sea ice / Re: Arctic Image of the Day
« on: September 22, 2013, 01:33:47 AM »
A ten minute span between images and it hasn't moved a jot...






Yep, presumably Jim is right and it is an ice breaker. Some ice blots on the lens appear to have partly disguised its profile.

Nice spot!

576
Arctic sea ice / Re: Arctic Image of the Day
« on: September 22, 2013, 01:20:13 AM »
It appears to have a whole lot of jagged features, like roots.


My guess is that a polar bear has dragged a tree stump into the Arctic and placed it in front of the cam...  :o



577
Policy and solutions / Re: Renewables Reach a Tipping Point...
« on: September 16, 2013, 02:00:57 PM »
Agree with the importance of demand response as raised by Satire and also addressed by Jim Hunt.

The market can address the matching of demand with supply if real time pricing is available to the consumer that reflects the instantaneous supply and demand for electricity. For example, the consumer electricity cost could be marked up from the wholesale price by a constant factor.

Doing that would make electricity available for a few cents per kWh for those willing to buy it for off peak use and for those with batteries.

The cheapest 'battery' that I am aware of is well-insulated hot water tanks that can store 24 hours worth of hot water. Hot water accounts for around 30% of total energy usage in a typical household. If that energy is available at only a few cents per kWh then such tanks could play a major role in matching energy demand with supply even for grids with large amounts of renewable energy such as wind power.



578
Arctic sea ice / Re: Arctic Image of the Day
« on: September 05, 2013, 12:24:20 AM »
Spectacular image! And a very nice explanation, Chris.

579
Arctic sea ice / Re: Latest PIOMAS update (August)
« on: September 02, 2013, 04:00:36 AM »
Thanks for letting me know, Chris, much appreciated.


The next update is going to be very interesting!

580
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 30, 2013, 11:55:37 AM »
Wipneus,

   On looking at MODIS Worldview, there appears to be a thin skin of new ice now over much of the exposed water near the Pole and on the Pacific side. When zoomed right in, little cracks that are even darker can be seen on the already dark regions between the floes: polynya within polynya! So that appears to show that the regions between the floes are mostly thin ice rather than completely exposed water.

This region is where some blue patches appear in your difference map, indicating ice where there was none before.

 So maybe that provides some explanation for increased area but not increased extent: new thin ice on areas that already had floes and so the cells were already above the 15% threshold you use in the extent calculation.

Does that explanation hang together given the observations and understanding of the processes that people have?

581
Arctic sea ice / Re: This melt seasons analysis
« on: August 27, 2013, 02:38:36 PM »
Thanks, Werther. Very interesting introduction to the discussion.

So you are saying that this year has been dynamically very different to all recent previous years and that you expect this to continue in future years?

This may be true. But do we know for sure that it will be? What drives the new dynamics? And why didn't it appear in any of the years 2007-2012 in particular, when ice coverage wasn't so different?

Because it didn't appear in any of those years, I would suspect at least an element of fluctuation this year. However, I don't feel I understand the dynamics myself.

  As an initial hypothesis, I have been wondering if the presence this year of all those leads and that open water within the ice pack has let to greater thermal exchange and moisture exchange than in any of years 2007-2012, thus promoting cooler and cloudier weather. Just a hypothesis - further evidence would be needed to support or else discredit it.

Does that hypothesis make any sense to you? And how does it mesh with the dynamical explanation you have given above, if at all?

I will be interested to read the comments from those with greater experience and understanding than myself...


582
Arctic sea ice / Re: NSIDC 2013 Arctic SIE September minimum: July poll
« on: August 26, 2013, 02:19:32 AM »
He's trolling.

There may be a valid point buried in there somewhere. However, he is berating the forum for allegedly being off by more than 2 sigma, where he himself has chosen the sigma (uncertainty) and with a justification that is dubious at best. Participants in the poll weren't required to state an uncertainty.

  The other point he deliberately ignores is that most competent experimental scientists will anyway have been off by more than 2 sigma on at least some occasions, through no fault of their own. Sometimes nature does that to you!

583
Arctic sea ice / Re: NSIDC 2013 Arctic SIE September minimum: July poll
« on: August 24, 2013, 12:34:15 PM »
Most scientific predictions of sea ice generally have confidence intervals of +/- 1 million

Yep he is a troll, spouting nonsense.

584
The voting has closed. Thanks to those who voted and/or commented.

I picked the bin for between 4000 and 4250 km3.

As a central value and sigma, I would pick 4200 +/- 400 km3. (I.e. about a 2/3 chance of lying within those limits.)
So that is a drop of 2900 +/- 400 km3 from the known PIOMAS Volume at 31 July 2013 of 7104 km3.

 I based that on historical guidance mainly from 2010-12 as the Arctic sea ice volume was much higher in all years prior to that. The corresponding drops for those years have been eye-balled from Wipneus' graph as 2600, 2400 and 2700 km3 for 2010, 2011 and 2012 respectively. I have guessed that the loss will be a bit higher this year given the poorer state of the ice on the eastern side of the Arctic Basin. On the other hand, the Arctic has been cooler this month than it was last year. So the chosen uncertainty also brackets the loss amounts for 2012 and 2010.




585
Is it just me, or has HYCOM suddenly and discontinuously 'thickened' the ice pack?
Oh wow. Yes, by a lot.

586
Arctic sea ice / Re: Latest PIOMAS update (August)
« on: August 18, 2013, 03:13:04 PM »
It would be fantastic if someone who knows how would be kind enough to do the PIOMAS sea ice thickness maps for the July data...  :)

587
Arctic sea ice / Re: When will we see open ocean at the north pole?
« on: August 17, 2013, 05:08:43 AM »
Danp,

That is a powerful image, thanks for posting.
To give the size scale, how many metres or km across does the green circle correspond to?

588
Steven, thanks for your comments on the binning. It turned out though that the votes are spread over quite a few bins, so I'm now comfortable with the granularity chosen. I always prefer to err on the side of a wide enough range that few, if any, voters are relegated to the underflow or overflow bins.

589
This poll will run for one week. You can change your vote.

PIOMAS volume minima for previous years:
Year --- Min (km3)
1979 --- 16,900
1980 --- 16,100
1981 --- 12,600
1982 --- 14,000
1983 --- 15,100
1984 --- 14,500
1985 --- 14,500
1986 --- 15,900
1987 --- 15,200
1988 --- 14,900
1989 --- 14,600
1990 --- 13,700
1991 --- 13,500
1992 --- 14,900
1993 --- 12,200
1994 --- 13,600
1995 --- 11,200
1996 --- 13,700
1997 --- 13,200
1998 --- 11,500
1999 --- 10,900
2000 --- 11,000
2001 --- 12,200
2002 --- 10,800
2003 --- 10,200
2004 --- 9900
2005 --- 9200
2006 --- 9000
2007 --- 6500
2008 --- 7100
2009 --- 6900
2010 --- 4400
2011 --- 4000
2012 --- 3300
(Values from 2003 copied from Volume Predictions thread by Dave C; private communication from Wipneus for values prior to 2003.)

PIOMAS Volume at 31 July 2013: 7104 km3
(Reference: Latest PIOMAS Update thread by Wipneus)

Daily volume plots by year...

(Plot and link courtesy of Wipneus.)

590
Arctic sea ice / Re: When will we see open ocean at the north pole?
« on: August 12, 2013, 11:40:10 AM »
Maybe even this month. The ice near the Pole is taking a pounding from strong winds for now and probably at least for the next few days, as I posted on another thread.

591
That low concentration region is even more evident on today's Bremen AMSR2 image...





And predictions are for it to be worked over by several more days of strong winds...


(This image will update, unfortunately.)



What will it look like afterwards?!

592
Arctic sea ice / Re: Latest PIOMAS update (August)
« on: August 11, 2013, 04:37:10 AM »
I'm wondering if there is going to be a poll for PIOMAS minimum volume?


We already have them for minimum area and minimum extent...  :P


593
Arctic sea ice / Re: What the Buoys are telling
« on: August 07, 2013, 11:29:43 AM »
Made me laugh, Pikaia...   ;D

594
Arctic sea ice / Re: What the Buoys are telling
« on: August 06, 2013, 10:33:22 AM »
 It's not a bird though. The polar bear has left a dirty mark on the lens.

It has also tilted the camera.


This can be seen by comparing the 'before' and 'after' images at
http://psc.apl.washington.edu/northpole/NPEO2013/WEBCAM1/ARCHIVE/,
where the first 'after' image is npeo_cam1_20130805195920.jpg

595
So again, the only possible reason I can come up with is freezing melt ponds, perhaps combined with ice floes falling apart in small pieces that spread apart, but don't melt out just yet. But even if that were the case, that still would't explain it.
Hi Neven,

  I like your explanation. It makes sense to me. But why do you say it wouldn't explain it?

  Isn't it true that the area algorithms have trouble with melt ponds? Indeed, isn't that the reason, or at least a reason, why extent has become established as an alternative measure, because it suffers less from this defect?

  With this year a bit colder than in recent years, it is possible that the melt ponds may have all frozen over earlier in the season than in previous years. (And why is this year a bit colder? Speculatively, could it be that all the cracks and openings in the ice are keeping the air temperature in closer equilibrium with the sea water temperature - at about -2 degrees C, or whatever it is?)

596
Arctic sea ice / Re: Arctic Image of the Day
« on: August 05, 2013, 09:47:01 AM »
No way!!  ;D

What a great photo!


597
EDIT on 11 August 2013...

Have bumped my prediction up by one sigma. Now:

2.75-3.00 bin.
Prediction is 2.9 +/- 0.7 million km^2


The reason is that the storm didn't do enough. I still expect losses this August to beat 2012's record for August, with lots of ice on the Eastern side that is even more vulnerable after the storm. However, the vulnerable ice is mostly where the ice had already largely disappeared by this time last year, while the ice off Alaska is a long way behind...

10 August 2013:


10 August 2012:




Original post (now revised)...
2.00-2.25 bin.
Prediction is 2.2 +/- 0.7 million km^2

I bumped up 0.2 million km^2 from last month after another poor month for melting. The central value of 2.2 million km^2 is the same as last year's value - so I'm saying it is about 50-50 that we will beat last year's record.

The uncertainty value is unchanged at 0.7 million km^2 as I still don't have a good idea of which way the melt is going to go.
This is a 1-sigma uncertainty - so about a 2/3 chance of between 1.5-2.9 million km^2.

Am I correct in saying that this year has had a lot more area with concentration well below 100% than any previous year with data? I still think that is going to take its toll over the coming month. By how much is the big question.

  If the predicted cyclone comes off in the next week then that might potentially break up the ice still further as well as stir up some warmer, saltier water into contact with it. That, as well as further weather favourable for melt, might push us below 2012. On the other hand, another month unfavourable to melting could leave us well above 2012.

598
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 03, 2013, 12:21:05 PM »
This thread rocks, Wipneus!  :)

599
Arctic sea ice / Re: Predictions
« on: August 03, 2013, 12:17:41 PM »
Again in the spirit of this thread, I predict record Arctic sea ice losses for August in all of NSIDC extent, Cryosphere Today area and PIOMAS volume. (Does 2012 hold the current records?)


That even takes into account the slow start to August, particularly in CT area. I just think there is a lot of ice that is ready to go, on the Eastern side in particular.

600
Arctic sea ice / Re: Predictions
« on: August 03, 2013, 01:59:44 AM »
Chris, that is a good question about why the remaining ice doesn't just spread out to fill the whole ocean.

  My guess is that it is because there is a prevailing direction or pattern for the wind + currents that move the ice. The ice tends to pile up against the northern coast of Canada. (And some of it squirts out the Fram Strait etc.)

  From time to time the ice will locally be moved in the opposite direction to the prevailing one, and so will spread out. Also, sometimes it will be pushed apart by low pressure systems and sometimes compacted by highs. But the spatial extent and duration of these systems is not enough for the ice to be spread out all the way across the Arctic Ocean. Instead, the ice will tend to be pushed back in the prevailing direction once that local system has died away.

  Another possible reason during the melt season is that the ice at the edges is more susceptible to melt than that in the pack, so it is being eaten away even as it is spreading.

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