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Messages - Nightvid Cole

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51
Arctic sea ice / Re: Latest PIOMAS update (August)
« on: August 04, 2015, 06:50:53 PM »
Same as above: thickness 2012 and the difference between July 2015-2012

The "2012" July thickness map looks just like the 2014 map. Did you copy the 2014 hyperlink again accidentally?

52
Arctic sea ice / Re: The 2015 melting season
« on: August 04, 2015, 12:03:54 AM »
Glad you posted this...it supports why I think Hudson Bay, Baffin Bay, and the Greenland Sea are going to refreeze in a couple weeks preventing a top 3 minimum.
That would be a full two months ahead of when those seas typically begin freezing.  Especially in the case of Hudson Bay reaching almost 50 degrees latitude (thus receiving significant insolation for another couple months),  the energy budget simply won't allow it.

Ordinarily you would be right but a 6-8C anomaly is not normal either and its 6-8C on the cold side. The heat energy needed to warm that is leaving and will be gone by September...Its like Lake Superior last year, it didn't completely ice out until the beginning of June 2014....Ice began reforming a month and a half above schedule in late October because the water never warmed up...given these anomalies the Hudson usually starts freezing in October I'm calling for a 4 week early start if weather conditions are normal because there is no built in heat energy in the water to fight. Once its consistently below freezing that's it there won't be a delayed reaction you typically see

No, plenty of other years (e.g. 2009) had Hudson Bay lagging in melt just as much as this year if not more, and had very cold water for much of the summer. Yet, the next freezing season did NOT begin in September. In 2009 for instance, there wasn't significant ice until late November (which is slightly later than the historical average.)

54
Arctic sea ice / Re: The 2015 melting season
« on: August 02, 2015, 04:07:59 PM »
July Blog post - How Low Can It Go...
http://dosbat.blogspot.co.uk/2015/08/july-status-how-low-can-it-go.html

I last used that title in mid August 2012, the only year PIOMAS has released data mid month!

Blink comparison. 31 July 2012 and 2015. Red line is 15 September 2007 ice edge.


You mean 15 September 2012 ice edge?

55
Arctic sea ice / Re: The 2015 melting season
« on: August 01, 2015, 04:24:50 PM »
CAB has begun its area cliff sooner than 2012 (Wipneus area, taken from Arctic Sea Ice Graphs page): (orange = 2012, green = 2013, pink = 2014)




56
Arctic sea ice / Re: The 2015 melting season
« on: July 31, 2015, 03:29:04 PM »
Witness the (first-ever) "Lomonosov Ridge channel", an expressway from Russia to Ellesmere Island:




57
Arctic sea ice / Re: The 2015 melting season
« on: July 31, 2015, 03:01:45 PM »
Wipneus compactness is below 2012 right now, on all 3 metrics, indicating that "slush" has continued to take over the Arctic:


58
Arctic sea ice / Re: The 2015 melting season
« on: July 31, 2015, 01:37:19 AM »
Its not just the ice north of CAA that is cracking up and leaving the shores, also some of the most resilient ice in between the islands is cracking up and exiting north. This picture is todays modis from Prince Gustav Adolf Sea (to the west) and Peary Channel, both areas which have always seen close to 100% concentration at minimum as far as satellite records go.

Lou, good post.

Great image. I suspected something of this sort would happen, since the amount of melt ponding in June over the CAA was just out of this world.

59
Arctic sea ice / Re: The Slow Transition
« on: July 26, 2015, 07:46:13 PM »
Cesium,

Regards the last paragraph, I don't get that at all, can't see which graph you mean.

I'm not sure how straightforward Glacial models of melt are.

If you're relating melt to melt degree days then a problem is that the ice pegs temperature at close to zero in summer, like ice in a drink. So there is hardly any upward trend in my calculation of melt degree days. I attach a quick plot of seasonal temperature anomalies relaive to the NASA GISS basline period of 1951 to 1980.

Anyway I recommend reading Blizzard of Oz's comment linked to above as a start to getting your head around the problem.

I suppose you could set the base temperature a few tenths of a degree below freezing for your melt degree days calculation - at least this relates to the amount of time the ice is in a melting state.

60
Arctic sea ice / Re: The 2015 melting season
« on: July 26, 2015, 02:09:35 PM »
Is this algae deep on the surface or is that crystal clear Arctic ocean with algae deeper down?
From todays satellite. Towards  NE Russia, near those islands out in that part of ocean

http://satwagraphics.com/testing/algae.jpg

.


It's close to the surface. Blue-green algae can't live as far below the surface as red algae.

61
Arctic sea ice / Re: The 2015 melting season
« on: July 25, 2015, 05:55:58 PM »
Yesterday (July 23) was a clear day over Beaufort, so the Bremen map reflected the true sea ice concentration there and in the adjacent area of the CAB. And this reality is a huge area with 50% concentration, with just a few remaining relatively small patches at high density (MYI remnants?) and about the same amount of holes at 0%.

So, is most of this ice doomed?

Yes. The concentration is now below 50% over much of that region. There's already more water than ice surface, and it is still July.

I think not: both area and extent are currently higher than in 2014, when Beaufort didn't come close to melting out.  Granted that the slowdown starting next week is unlikely to be as pronounced or prolonged as in 2014, and concentration is unusually low.
     The dynamic is noteworthy, though - a lot of those high-concentration MYI patches will become stranded in open water before the minimum.  Don't think I've seen that phenomenon before on this scale.

Can you find a single example of <50% concentration ice as of July 23/24 of a given year surviving the season? I think not.

Extent and area tell you that there's a lot of slush, sure, but a lot of slush is still just slush.

62
Arctic sea ice / Re: The 2015 melting season
« on: July 25, 2015, 03:15:10 PM »
Yesterday (July 23) was a clear day over Beaufort, so the Bremen map reflected the true sea ice concentration there and in the adjacent area of the CAB. And this reality is a huge area with 50% concentration, with just a few remaining relatively small patches at high density (MYI remnants?) and about the same amount of holes at 0%.

So, is most of this ice doomed?

Yes. The concentration is now below 50% over much of that region. There's already more water than ice surface, and it is still July.

63
Arctic sea ice / Re: The 2015 melting season
« on: July 25, 2015, 03:11:57 PM »
Yes, please. I've looked for an existing thread, and maybe this one is suitable: OLR in the Arctic. Otherwise, open a new thread, someone. All of this will be lost, never to be found again, as this is the thread with the most pages on the forum.

Atmospheric OLR stuff can go to that thread, and anything about absorption/reflection/emission by ice can go to my arctic sea ice optics thread...

64
Arctic sea ice / Re: The 2015 melting season
« on: July 25, 2015, 01:23:28 AM »
Northern Sea Route is "open" based on ZMAW's map...


65
Arctic sea ice / Re: The 2015 melting season
« on: July 25, 2015, 12:48:45 AM »
Forecast (both ECMWF and GFS) is still for 3-4 more days of this, high pressure moving to Siberia and then away, but perhaps high pressure building up again near the CAA and Beaufort coasts.

This freezing temps that GSF forecasts, however, right in the smashed up MYI zone, could stop the 2015 trend line dead in its tracks, I think:

I doubt it - it will nearly be August by the time those temps hit. It's "bottom melt" season, not "surface melt" season which extends from June through July.

Bottom melt dominates beginning from late July really, so slightly below freezing temps won't do anything to the melt. Bottom melt continues until the SST drops to near -1.7 C (or until the surface air is several degrees below freezing).

66
Arctic sea ice / Re: The 2015 melting season
« on: July 24, 2015, 09:21:40 PM »
Is it just me or is the western CAB now also "turning green"? Here's Terra 4km/MODIS for today:


67
Arctic sea ice / Arctic sea ice OPTICS
« on: July 24, 2015, 08:00:07 PM »
Even snow-covered sea ice is not a Lambertian reflector, since at shallower incidence angles not only is the illumination nearer the surface and thus more photons escape without absorption, but also the individual snow crystals scatter preferentially in the forward direction and thus at shallow incidence angles you can get more single-scatter-escaping photons. For these reasons, light at shallow incidence angles has a higher % reflected.

When snow melts and leaves bare ice, there is still a surface scattering layer, though it has a lower air/ice ratio than snow does, but the same phenomena occur.

When you replace it with melt ponds, albedo drops, but a water surface also has higher albedo at shallower incidence angles (see https://en.wikipedia.org/wiki/Fresnel_equations).

Finally, when you have a field of low-concentration but irregular ice, shallow-incidence-angle light is almost certain to hit the peak of a floe before reaching the liquid water, while steep incidence angle light has a good shot at actually hitting liquid surface.

There are several consequences of this. One interesting consequence is that when the sun is low in the sky, clouds may actually *enhance* the absorbed insolation rather than reducing it, because more light is coming from higher in the sky (steeper incidence angles), particularly when the ice is still covered by snow and thus the total illumination doesn't decrease much on account of multiple reflections between surface and clouds.

However, when the sun is at higher angles, clouds of course reduce it.

Another consequence of this is that while the north pole may be getting more insolation than the peripheral Arctic near the Solstice, less energy is absorbed, because almost all of it is coming in at shallow incidence angles. At lower latitudes such as 70N or 75N, the time of day with the most insolation also has the lowest albedo, so the net effect is larger absorbed energy.

A truly accurate understanding of energy balance of sea ice must use proper optics - a single "albedo" figure will never be physically reasonable.

68
Arctic sea ice / Re: IJIS
« on: July 24, 2015, 03:25:20 PM »
IJIS:

7,201,855 km2(July 23, 2015)down 100.037 km2 from previous.

Have you converted from American to European now, using a period instead of a comma for daily decrease number? Dual citizenship?  ;)

69
Arctic sea ice / Re: The 2015 melting season
« on: July 24, 2015, 03:06:50 PM »
Another day where the ice in the peripheral seas slops around - as shown by edge movement and shifting concentrations - while the CAB ice mass (i.e. inside the 80 degrees N line) remains rock solid in concentration.

It continues to look like not much of the ice in the peripheral seas will survive the melt season while, conversely, not much of the CAB ice will be lost.

Click on .gif to flash back to yesterday's map...

I think the high concentrations in the CAB are genuine on the CAA and Atlantic side, but not in the Pacific sector below ~84N. What seems to be happening is that we haven't really had a clear day in that area since around the 9th of this month.

Have you tried looking through the 89GHz polarization ratio maps on the ADS/VISHOP page (JAXA)? If you animate those maps, you can see where thick clouds are (white) and where thin clouds/fog are (nebulous/translucent-looking).

The concentration actually had dropped quite markedly in the region within about 30 degrees longitude of the date line up to about 84 North. Look at the archives on Bremen maps for July 7th, 8th, and 9th.

Since then, it has been cloudy. So I don't know how one is supposed to determine the real concentration since we have been without a good clear day over the entire region for two whole weeks...

70
Arctic sea ice / Re: Arctic Image of the Day
« on: July 23, 2015, 07:50:45 PM »
Earth is the target of an alien attack on the polar regions using a giant blow torch:


71
Arctic sea ice / Re: The 2015 melting season
« on: July 22, 2015, 03:53:38 PM »
To Slow Wing  and Juan Garcia:
And anyone else who can answer my layman questions below

Yes, it looks like the Pacific Blob has been seeping into the Arctic, the warm water staying on the surface, melting a much bigger area than equivalent date in 2012, and snaking around the edges melting those places.
What will happen when the last ice-bridge to land in Northern Siberia melts through and that Pacific Blob water on the surface breaks all the way through?
What is the state of the temperature of the waters coming on from the Atlantic?
Or does the Arctic water flow into the Atlantic, not the Atlantic into the Arctic?
If there is a current through the Arctic from the Pacific that has any strength ( warm water at the surface ), will that warm water current actually quickly pull MORE warm water into the Arctic from the Pacific Blob, once that last ice barrier  once that melts in Northern Russia, and the gates are open?

Tommy.

No, you've got the direction of the currents backwards. Between Severnaya Zemlya and the mainland, the flow is West to East (i.e. Atlantic to Pacific).

72
Arctic sea ice / Re: IJIS
« on: July 22, 2015, 03:40:34 PM »
IJIS:

7,415,444 km2(July 21, 2015)down 107,064 km2 from previous.

...and 5th lowest for the date.

73
Arctic sea ice / Re: The 2015 melting season
« on: July 22, 2015, 03:36:21 PM »
ECMWF now definitely has the high pressure moving over to the Siberian side of the Arctic. It's still pretty high pressure for a couple of days (forecast for days 7-10 show basically the same set-up), but of course no Beaufort Gyre or transport, and more clouds over the vulnerable ice in the Beaufort and CAA. I'm very curious to see what this will bring!

Definitely will be good viewing weather. I also expect area graphs to drop precipitously as a result of the cloud-effects (which tend to bias measured concentration high) dropping out.

74
Arctic sea ice / Re: Northwest Passage thread
« on: July 22, 2015, 01:01:25 AM »
The fracture zones are within 150KM or so of one another.

I wonder how much faster the disintegration will proceed once they do?

Depends upon the wind.

75
Arctic sea ice / Re: The 2015 melting season
« on: July 21, 2015, 11:00:54 PM »
...
3) There is a lot of excitement about rotten ice round here, much of it is not founded - I don't want to make myself more unpopular round here, but this is simply the case! This 'rotten ice' will get worse in the years to come, it will play a pivotal role in the coming transition to a seasonally ice free state. But it is not behaving in such a manner as to indicate highly abnormal increase in rotten ice in the context of the post 2007 period portending a rapid crash. Instead the behaviour is pretty average for recent years.
...

I agree, Chris.  We've seen a lot of rotten Arctic sea ice in recent years.

We know a GAC (Great Arctic Cyclone) can do a great deal of damage to sea ice, if 'well' timed.  I wonder, though, what the next 'new' force will be to unexpectedly disappear some ice.  A tsunami? A meteor? 2" of rain? Business as usual?

Business as usual is the most certain bet, we've got plan A (exponential growth) or plan B (exponential growth + greenwash).  ;)

Two graphs, 2015 is the bright red plot...

Compactness in the peripheral seas.



Extent in the peripheral seas.



We're still in the range of past years...

Sorry but these are only to 18 July 2015, not had the time to update.

EDIT
Actually I am up to 19 July, which throws light on those weird plots from CT Area,

Greenbelt/Nightvid/SeaIceSailor.

Compactness for the Central Arctic...
14-Jul   0.787
15-Jul   0.776
16-Jul   0.780
17-Jul   0.780
18-Jul   0.780
19-Jul   0.776

No massive jump in compactness, values before 14 Jul are similar. So that jump in concentration isn't in the data, Wipneus's calculations would have caught it and reflected it as a jump in compactness.

It's nice to have "algorithmic continuity" back again from CT.  :)

76
Arctic sea ice / Re: The 2015 melting season
« on: July 21, 2015, 07:04:47 PM »
CT has reverted to maps with the "old" ice algorithm, but without the snow of February...

77
Arctic sea ice / Re: Arctic Image of the Day
« on: July 21, 2015, 06:19:55 PM »
Magnificent exposure of the Foxe basin today (2015-07-20)

Beautiful blooms on the Eastern shores...

78
Arctic sea ice / Re: The 2015 melting season
« on: July 21, 2015, 05:23:27 PM »
This melting season started out slow, despite warmer conditions than in 2013 and 2014. How can the ice possibly be super weak and on the verge of collapse?

But if the conditions were warmer and the parameters indicate that the melt started later - perphaps there is something wrong with the parameters?

I am not saying that's the case, but it is a possiblity.
My impression at least is that the warmth has been chewing into the volume more than in to extent or area (if that makes any sense at all ;-))

Here is for instance the view of TOPAZ4. 2012, 2014 and 2015. First image is  30/06, second image 20/07 - to get an impression of the melt momentum (Warning, images seem to be pretty big so they take quite a time to load).
Here 2012 seems to start out with more volume (measured by the most scientific method known to me - pure eyeballing) - which seems odd or agains PIOMAS - and has the most momentum. But 2015  looks to be not too fare behind momentum-wise & perhaps even worse wrt the ice thickness.
Of course it is just another POV & to be taken with a huge grain of salt imho (ah I just see that they also use the data from the HYCOM model so probably not so much of a different then).

2012:
2012-06-30
2012-07-20

2014:
2014-30-06
2014-20-07

2015:

2015-30-06
2015-20-07

Yes, this is key. We have to wait for the "80 North" bug in HYCOM/CICE to be fixed, until then, any model which takes the problematic outputs as its own input is thus affected by the bug.

79
Arctic sea ice / Re: The 2015 melting season
« on: July 21, 2015, 04:07:10 PM »
Look, 2012 was followed by two cold rebound years. The amount of multi-year ice increased, and so did volume most probably. This melting season started out slow, despite warmer conditions than in 2013 and 2014. How can the ice possibly be super weak and on the verge of collapse?
Here you present two separate issues. One being the MYI rebounded giving the impression that the new MYI is equal to pre 2007 MYI. I remember the reports coming out at the end of 2012 melt season that there was virtually NO MYI left in the Arctic. Therefore how can all this new MYI that suddenly shows up be the same? It does not take only one season to get rid of salt to change it from FYI to MYI. Therefore my contention is all this new MYI is actually very salty. Not only that, but held together by FYI.
Part two is that we had low Max low melt yet warm conditions. You argue that because we still have  high area and extent numbers the ice must be very strong and will still hold out to the end. It could be right in that it will hold out to the end but having lived most of my life in snow country I know that snow and ice can fool you into believing it will be there for a long time and then you wake up one morning it it has all disappeared over night.
If I start out with the premiss that the MYI is not true MYI and all the ice that is around is being attacked by higher then normal heat, then I am left with the conclusion that the ice is faking us out. If it does not happen this season then unless we get a very cold long winter and a very cold short summer that ice is in very serious trouble. I live in a country where you can have 6 feet of snow everywhere vanish in less then a week.
I also keep on seeing posts talking about heat that is only being generated within the Arctic and that there is not enough left to do the job. That only works out if you have a very strong jet stream that is keeping the Arctic isolated from the rest of the world weather patterns and cool ocean currents running into the Arctic. Under today's conditions even an Arctic low can draw in a lot of heat from its surrounding environment and all that water flowing into the Arctic is all well above average. Not ideal conditions to sustain strong ice and keeping it strong.

Well, one thing that we can say for sure is, the MYI that was advected into the Beaufort Sea over this past winter is now broken up and low-concentration, and that ice with a concentration below 65% by July 20th does not survive the season. I've looked through every year since 2002 and have been unable to find a single exception.

Beaufort is a goner.

80
Arctic sea ice / Re: The 2015 melting season
« on: July 21, 2015, 12:19:05 AM »
So what's to keep area from falling as much as 2011 did for the next two weeks, and then as much as 2012 did for the rest of the way? Surely that's not impossible?

Despite the past few weeks, I don't think the lack of preconditioning can be fully compensated, and thus melting momentum will not be sufficient to keep the rate of decrease as high as it has been the past 2 weeks. But we'll see when the weather switches.

If it switches.  :)

I think so as well. also to answer Nick, i meant I feel this year will not be a rebound year anymore (forget linguistics, I mean bye bye 2013 2014) after looking at that map and the nice Montecarlo sims presented today, just as improbable as this year smashing 2012 record. Ok (well, not exactly hehe, 0.01% to being nearly equal to 0.1%, but both very small wrt 100% tbh). But nothing of that still strictly impossible as jdallen says. Lol

Nothing is truly impossible in a Gaussian distribution.  ;D

81
Arctic sea ice / Re: The 2015 melting season
« on: July 20, 2015, 11:24:21 PM »
So what's to keep area from falling as much as 2011 did for the next two weeks, and then as much as 2012 did for the rest of the way? Surely that's not impossible?

Despite the past few weeks, I don't think the lack of preconditioning can be fully compensated, and thus melting momentum will not be sufficient to keep the rate of decrease as high as it has been the past 2 weeks. But we'll see when the weather switches.

If it switches.  :)

Both GFS and ECMWF are predicting High pressure dominance for a full week....transitioning away from dipole and more towards "centered" High. The latter is the best weather for viewing the ice more-or-less cloudfree. Since clouds interfere so much with observation, even in microwave data, I am very much looking forward to this clear weather spell.

82
Arctic sea ice / Re: The 2015 melting season
« on: July 20, 2015, 11:20:08 PM »
I think Nick was asking about the result you'd get if included only pre-2012 years in computing the distribution for 2012 (i.e. forecast, not hindcast).

I thought that too initially, but it wasn't what was written.

Graph attached. probability of 2012 rises to 0.3% (for the individual date, apply a reaonable range and the probability will increase - any spot figure is rather improbable, some are less improbable than others).

The disrtibution for 2007 to 2012 drops notably, showing the role of 2013 and 2014 in the preceding 2012 and 2015 distributions based on 2007 to 2014 data.

So the graph shows 2007 to 2012 applied to 2015 and 2007 to 2012 applied to 2012.

"Pre-2012" would have to be 2007-2011, not 2007-2012 as you show.

83
Arctic sea ice / Re: The 2015 melting season
« on: July 20, 2015, 10:40:42 PM »
No seperate thread needed, I don't think there's a great deal more to say...

Nick,

2012, or any other year, would just be a shift in the distribution. In practice the curves change slightly because even with 1,000,000 iterations the results haven't converged totally between runs. With 100,000 runs the standard deviation of the average for each run is around 0.001, 1,000,000 should be good enough.

I have attached a plot of 2012 and 2015 start extent for the 18 July.

You are right about the probability for 2012, see my comment below to OSMM. The probability for the 2015 start extent is 0.012%, for the 2012 start extent it is 0.082%.

OSMM,

For each day there are 8 possible losses from years 2007 to 2014, increment day through 18 July to 15 Sept and randomly select one loss from the 8 losses for that day.

I can't add anything more to what Nick has said about autocorrelation. I think the major issue here however is not autocorrelation but dependence on initial conditions. 2012 appears to be a very unlikely event with this monte carlo approach. In reality it was not. Initial (April) volume (or thickness) provided conditions conducive to high loss due to extensive thin ice and a low export from the central arctic of MYI. This manifested as very low compactness by July, which in a different approach could be used to add priming information to a prediction. However this information, which suggested strong August losses was not available in the monte carlo approach, as I have implmented it. So it gives an unrealistically low probability of the 2012 minimum.

Note that in the approach used now I have deliberately chosen Arctic Ocean (which includes CAA, Barents & Greenland Seas), this is because of my reading of ice state in the peripheral seas (Beaufort round to Latpev) which suggests to me that overall extent is giving an inaccurate impression of ice state. Like 2012 I expect above average losses in August due to state in the peripheral seas. However the choice of Arctic Ocean rather than whole Arctic does itself reflect my bias (or prior).

Jai,

The standard deviation of the 1,000,000 'predictions' is 0.308M km^2, which can be applied to the peak value of 4.5. However due to the autocorrelation as mentioned by OSMM using the probabilities normally associated with the standard deviations is not really sound.

I think Nick was asking about the result you'd get if included only pre-2012 years in computing the distribution for 2012 (i.e. forecast, not hindcast).

84
Arctic sea ice / Re: 2015 sea ice area and extent data
« on: July 20, 2015, 05:00:18 PM »
Charctic SIE loss today is 1.63 million Km^2
2012 loss for the same day was 1.004 million Km^2

http://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/

I think you need to move the decimal point one spot to the left...

85
Arctic sea ice / Re: 2015 sea ice area and extent data
« on: July 20, 2015, 04:41:25 PM »
Wipneus,

Quote
Note: snow cover data not updating ... we hope to have a new data source by July, 2015.

CT is going through a planned data source change. It may effect NSIDC as well. That may be the reason for the remarkable stability. You can see that the change effects concentration as well as snow by looking at the animation:

http://arctic.atmos.uiuc.edu/CT/animate.arctic.color.0.html

Verg

Could this be simply due to the 2-3 day lag "dropping out"?

86
I was reminded of this site http://polarportal.dk/en/havisen-i-arktis/nbsp/sea-ice-temperature/
and had some fun moving the temperature scale 1 degree up and moving bits of loose ice to the Arctic basin pack. Not that this is a valid method for prediction, though at some thickness the ice appears to warm up to melting point all through the ice before melting away completely. I wish all maps would have a scale in them so the area could be approximated from the pixels. No idea what this amounts to.

Interesting...

87
Arctic sea ice / Re: The 2015 melting season
« on: July 20, 2015, 02:20:27 PM »
Personally, I'm not ruling anything out.

http://igloo.atmos.uiuc.edu/cgi-bin/test/print.sh?fm=07&fd=17&fy=2015&sm=07&sd=17&sy=2012

Santa must have decided to re-paint his house (the Pole Hole is a new color...)  :)

88
Arctic sea ice / Re: The 2015 melting season
« on: July 20, 2015, 02:17:52 PM »
Having twisted my ankle and being off work as a result, I have some free time...

Taking Arctic Ocean extent data, where my definition of Arctic Ocean includes CAA, Greenland Sea, Barents, Kara - a choice made to get a dataset that represents conditions for the regions that set the minimum. I have tabulated day to day losses for 15 July to 15 September for each year 2007 to 2014. This data is then used to do a monte carlo estimate of the probability distribution for the 2015 minimum.

The code written does one million runs. In each run the 15 July 2015 extent is used as the start extent, and for each day a daily loss is chosen at random from the available 8 year dataset. These losses are summed and applied to the 15 July 2015 extent to create a simulated extent for 15 September 2015. The resulting 1,000,000 extent values are then combined in a histogram and normalised to 1 to produce a probability distribution.



92% of the probability lies between 4 and 5 million kmsq.

The peak probability is at 4.5 million kmsq.

Could you do a similar one for CT area?

89
Arctic sea ice / Re: The Slow Transition
« on: July 20, 2015, 03:07:32 AM »
I think the argument that the decline in max volume will flatten is likely correct.

But that's the only part I agree with. If increases in melt are due to more open water, are you claiming that there will be less open water? Because it seems the opposite is what is happening and will continue to happen. More open water earlier in the season, as well as many other factors all pushing the system towards more melt.

It seems to me that the argument that increased melt is caused by declining max volumes is putting the cart before the horse.

I agree it is putting the cart before the horse.

The problem with Chris's argument in post #49 exemplified by the correlations in the first plot therein, is that *of course* spring volume loss correlates with year-on-year volume loss; spring is part of the year! What Chris should be doing is comparing de-trended spring max volume to de-trended spring-to-summer volume loss; if there is a statistically significant correlation, it supports Chris's hypothesis, if no significant correlation, the hypothesis is unsupported.

Chris argues also based on open water formation efficiency, which includes physically plausible assumptions, however, one must not confuse area/extent loss increasing with volume loss increasing. While volume loss can certainly increase as a result of lower albedo of a fragmented pack, as Chris rightly points out, it does not follow that other factors such as June snow cover can't have a similar effect; thus the conclusion of a "slow transition" is not justified.

90
Arctic sea ice / Re: What the Buoys are telling
« on: July 19, 2015, 05:25:37 PM »
this floe at camera2 shows what ice looks like when it is getting thin.
I think the ice is now porous from molten brine channels and therefore translucent when low in the water and wet but white when the the drained brine has been replaced by air.  The image shows that the surface of the floe on which the camera stands is still well clear of the water but the reduced density of the ice above the waterline gives an exaggerated impression of its overall thickness.

This is an amazing image!!!

Look in the sky, close to the horizon. You can see subtle lighter and darker regions.

This phenomenon is known as blink, sky blink, ice blink, or sometimes water sky blink. It is caused by reflection of light from areas with a lot of ice and not from open water.

It is very interesting in part because it gives us a sense of what the ice looks like on a spatial scale of a few km, rather than the mere meters we can get from the direct view of the surface.

It is apparent that the ice concentration in that region, out to a few kilometers, is ~50%.

91
Arctic sea ice / Re: The 2015 melting season
« on: July 19, 2015, 05:03:17 PM »
Really enjoying the great analysis and graphics in this exciting part of the melt season.

Years 2007 onwards are actually fairly close at mid-July and it is the second half of July where 2012 in particular streaks away, as Neven posted and showed graphically above.

The daily University of Bremen concentration map has been posted. Beaufort, Chukchi & the Siberian side continue to deteriorate.

The 80 degrees North line indeed looks a good demarcation line between the zone outside where concentrations are waning and, on the other hand, inside it the high concentrations have scarcely been dented on the Pacific and Siberian sides.

Will we end up with a fairly roundish ice distribution at minimum this year?

Click on the map below to also sample the two preceding days...

00z ECMWF suggests that we will have a much clearer view of much of the CAB on several days this week, due to the large dome of High pressure.

Be patient (I have trouble with this myself on occasion!)

92
Arctic sea ice / Re: The 2015 melting season
« on: July 18, 2015, 04:59:34 PM »
A new page and we're back on sea ice.  ;)

Sea Ice Sailor,

I have a suspicion that Beaufort might be surprisingly resilient this year and that the melt there will remain only slightly greater than average.

Greater than *which* average? 1979-2000? 1981-2010? 2007-present?

93
Arctic sea ice / Re: The 2015 melting season
« on: July 17, 2015, 02:27:41 PM »
The Fram Strait export machine will be on, full throttle, according to Climate Reanalyzer, in a week (Orange = High Pressure, Purple = low pressure):


94
Arctic sea ice / Re: The 2015 melting season
« on: July 16, 2015, 02:14:28 PM »
Some of those ablation stakes have had too much to drink...  ;D

95
Arctic sea ice / Re: What's wrong with HYCOM?
« on: July 15, 2015, 06:12:28 PM »
Plinius first mentioned it here about a week ago:
If you look at this again:
http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticsss_nowcast_anim30d.gif

There is a perfect, circled boundary in the salinity near the end of the simulation. No way that this is caused by some natural current [...]

It's still there, it's now in the nowcasts as well as the forecasts, and it affects both versions of the Navy's models, see here:
http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticsssnowcast.gif
http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticsssnowcast.gif

Does anyone have any contacts with the people running these models so we can ask what's going on?  As it stands, I don't think either of the versions of the model can be remotely trusted since they are both giving grossly unphysical outputs.

Try their contact info web page:

http://hycom.org/contact-info

96
Arctic sea ice / Re: The 2015 melting season
« on: July 14, 2015, 07:39:30 PM »
DMI's thickness map (Danish Polar Portal web site) shows the following for thickness progression over the recent weeks:



I'm a little bit surprised by the thinning being so sensitive to compaction. Though tough to tell from looking at these maps, by paying attention to the yellow region, between June 20th and July 1st, there was considerable thinning, but not so much from July 1st - July 13th, though that region did shrink, due to compaction from the Siberian side (note the edge position). Note that 11 days passed between the first two maps, and 12 days passed between the second and third maps.

If this is accurate, compaction may actually preserve ice, not get rid of it.

97
Arctic sea ice / Re: The 2015 melting season
« on: July 14, 2015, 04:39:46 PM »
Outlined in orange is the "high concentration" region on the NSIDC map (rotated to put Bering Strait on top):



This is very nearly the same as suggested by snow cover one month earlier:


98
Arctic sea ice / Re: The 2015 melting season
« on: July 13, 2015, 04:06:57 PM »
I never said much extra methane forcing "was" earlier this year. It's possibly in store for next few months, i think. Ask Wadhams about it if you can, but my guess is that local (Arctic-emitted, Arctic-affecting) methane problem is the least during spring and early summer, grows during summer and peaks some time in autumn.

Then it will not have much impact on the Arctic ice extent, because the crucial early season is still normal. A methane episode beginning in August, September, or (obviously) October, I would argue, is simply too late in the season to have much effect.

It is really May and June, it seems, that make or break a melt season.

99
Arctic sea ice / Re: The 2015 melting season
« on: July 13, 2015, 01:49:38 PM »
...
Wadham's prediction of 1M km^2 is best put in context by the fact that even though we have some record low area/extent/compactness, none of those figures are so much wildly lower than other recent years that they suggest something as extreme as a 1M km^2 September extent.
...
Wadhams happen to be a part of AMEG. Despite all the questionable suggestions and arguments the group spits out, they do have a point. CH4 is ~120 times more efficient GHG shortly upon release than CO2 (during ~6 months or so after release of any given portion of it). And last few years, we do have so-called (by russian scientists in the field) methane-related "cold eruptions" of large masses of soil from permafrost regions. Last illustration of this story gives an idea what these eruptions are.

I've seen close footage and heard russian scientists explaining details about this; there is no doubt this is pressure-caused soil eruptions, and there is no doubt the pressure is created by methane to a large degree, since lakes forming in such "craters" after a few weeks have their waters oversaturated with methane - those few ones which were analyzed for that.

I would suggest that Wadhams' predictions are in large part based on methane emissions in the Arctic - not only from land permafrost, but also from shelf methane clathrate deposits, which hold thousands gigatons of methane in total, of which few dozens (~50) gigatons in ESAS alone may be released "at any time", as discovered by Shakhova et al famous paper. I am not saying it's happening now - i have no reliable data myself to state that, - but i say it's likely prof. Wadhams thinks it is happening now on a scale sufficient to produce large extra melt effect during the melt season.

The only unconfirmed data about last 2...3 years of actual net methane annual emission in Arctic which i happened to see not so long ago - suggests that said emission was nearly doubled in 2013 and once again nearly doubled in 2014. Sadly, i am not at freedom to provide the source here. It is my understanding that if we'll get three or four more years like that - doubling Arctic's annual methane release each year, - then Arctic will by then be emitting over 1Gt of methane into the athmosphere every year, which would certainly be a major factor to a huge extra summer melt. While i am not sure whether my data is true (and i am not sure what's more likely - whether it under- or over-estimates!), i believe it's enough reason to suspect that prof. Wadhams certainly took extra warming from extra methane into account when he made his prediction about 1M km^2.

The problem with that is, if the methane forcing were really large enough for that to be reasonable, it would surely be obvious when looking at other indicators such as Arctic temperatures, longwave radiation, or springtime ice thickness.

The snow retreat in May and June should also bear it out. What we actually saw is that the land-based snow for May and June was within the typical range of the last few years, not extraordinary. However the snow cover on Arctic sea ice retreated very rapidly in June.

Nonetheless, while that snow retreat does justify the conclusion of the 2012 records being beaten this year, it does not point to a nearly-ice-free Arctic this year if one simply does the linear regression. Occam's Razor says that you don't multiply entities beyond necessity - so if one wants to use a non-linear regression rather than a linear one, it needs to be independently justified.


100
Arctic sea ice / Re: The 2015 melting season
« on: July 12, 2015, 12:34:48 AM »
Quote
At the face of it, I don't see how 2015 is in better shape than 2012.

Could we get someone with data skills to put numbers to the 'big bowl'?  Extent, area, concentration, and thickness.

Check the last two blog posts on the ASIB.

Edit: Not that I would call myself someone with data skills, but there's a lot of info and comparison in there. Tomorrow I'm posting more comparisons for June.

The big question now is: How low can a melting season go without compaction? Last year didn't go low. This year there's (much) more heat.

It can go as long as the high-pressure isn't in the right place for compaction. In July 2011 we had a period with the big dome of high pressure right in the middle of the Arctic Ocean. This time around it is close to the CAA, and we have essentially a weak dipole.

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