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slow wing

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Re: The 2016 melting season
« Reply #100 on: March 25, 2016, 12:23:07 AM »
Agree with crandles that weather will have a large effect on date of maximum sea ice area.

If looking for a trend over the years, then I would suggest doing a fit each year to a several week interval around the mean maximum date and then using that maximum determined by the fit for each year. The fit could be to e.g. the top of a sine wave, or a quadratic. That would be more robust and remove some of the weather noise.

plinius

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Re: The 2016 melting season
« Reply #101 on: March 25, 2016, 07:49:25 PM »
Agree with crandles that weather will have a large effect on date of maximum sea ice area.

If looking for a trend over the years, then I would suggest doing a fit each year to a several week interval around the mean maximum date and then using that maximum determined by the fit for each year. The fit could be to e.g. the top of a sine wave, or a quadratic. That would be more robust and remove some of the weather noise.

That is not more robust, but limiting your functional shape with rather unpredictable consequences. I would advise strongly against that.

@crandles: Have you possibly attempted to exclude the Ochotsk? Additionally it might be worthwhile to try to fit simultaneously the time trends in both variables and the correlation term. Should give a bit of a better guidance for that.

crandles

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Re: The 2016 melting season
« Reply #102 on: March 25, 2016, 09:11:33 PM »
Agree with crandles that weather will have a large effect on date of maximum sea ice area.

If looking for a trend over the years, then I would suggest doing a fit each year to a several week interval around the mean maximum date and then using that maximum determined by the fit for each year. The fit could be to e.g. the top of a sine wave, or a quadratic. That would be more robust and remove some of the weather noise.

That is not more robust, but limiting your functional shape with rather unpredictable consequences. I would advise strongly against that.

I thought it might help if the weather changes frequently between warm/melt inducing and cold/freeze extending conditions frequently. However I suspect the 31 day average deals with that adequately enough and the remaining problem is if it is warm or cool for a large part of the 31 day period. I doubt fitting to a sine wave shape helps against this remaining problem. That is just a gut reaction - doing it would help remove the doubt.


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@crandles: Have you possibly attempted to exclude the Ochotsk? Additionally it might be worthwhile to try to fit simultaneously the time trends in both variables and the correlation term. Should give a bit of a better guidance for that.

I haven't tried to exclude Ochotsk. I guess that would reduce some of the variability.

Not sure if you are suggesting a multiple linear regression fit (of max date using time and extent) or something else. I could see if that gives a lower standard error than using just time or just extent.
Would suspect the noise would be such that any reduction would be tiny. Guess I won't know unless I try these suggestions.

So thanks for suggestions and sorry if I take a long time or fail to get around to them.

slow wing

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Re: The 2016 melting season
« Reply #103 on: March 26, 2016, 04:09:48 AM »
Thanks for replies.

Yep, taking a 31 day average would be another way of reducing year-to-year noise.


Concerning whether to remove Sea of Ochotsk, that depends on your actual motivation in studying this.

Are you looking for anything around peak ice area with a statistically significant non-zero trend through the years? If so then ice coverage at Ochotsk could be part of your signal.

Are you instead looking for a predictor of Arctic sea ice coverage at minimum? If so then I agree Ochotsk should be removed.

seaicesailor

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Re: The 2016 melting season
« Reply #104 on: March 26, 2016, 01:30:25 PM »
Another way to put these interesting ideas:
- In a warmer Earth, ice extent growth ceases earlier: the loss of heat during the Winter night is balanced at higher latitudes by the greenhouse-trapped heat that is convected from lower latitudes.
- However, melting of sea ice:
 1. Hysteretic behavior: it requires more temperature to start surface melting than what it needed for freezing, it is fresher than when it froze. And it needs time for convecting heat from atmosphere to ocean for bottom melting.
2. Need of sunlight for direct heat, which comes always at the same time every year
3. Geographical/geometric aspect that edge retreat at outer seas means much less extent loss rate than when it retreats within the Arctic Ocean proper.

The last three convince me to think that extent curve flattens and slowly merges with previous years curves in April after a two month plateau.

Problably this is still uncharted, but to me it makes quite some sense. Unsupported by data? Absolutely : -)

crandles

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Re: The 2016 melting season
« Reply #105 on: March 26, 2016, 02:16:00 PM »
Not sure I am following what you wrote correctly.

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In a warmer Earth, ice extent growth ceases earlier
Yes I think I get that and is the same as saying higher GHG levels can compensate for a slightly lower sun angle so the expansion of ice extent stops earlier.

Quote
the loss of heat during the Winter night is balanced at higher latitudes by the greenhouse-trapped heat that is convected from lower latitudes.

Higher GHG level reduce rate of heat being lost to space. There is also wind transported heat from lower latitudes. If the lower latitudes are getting warmer then more heat may be transported, but winds being more zonal or meridonal might play a bigger role but that quickly gets complex.

These reasons suggest lower and earlier peak, and I am not disagreeing with this.

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1. Hysteretic behavior: it requires more temperature to start surface melting than what it needed for freezing, it is fresher than when it froze.

Is this changing from year to year? If so, why? If not, I am not sure how it affects things.

Quote
And it needs time for convecting heat from atmosphere to ocean for bottom melting.
Yes but it takes so much time before that starts, I don't really see it affecting timing of maximum.

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2. Need of sunlight for direct heat, which comes always at the same time every year

Same time for same place, yes. However if extent is lower so edge is further north then it will be later.

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3. Geographical/geometric aspect that edge retreat at outer seas means much less extent loss rate than when it retreats within the Arctic Ocean proper.

Not sure I am getting this at all. If lower extent means there is less ice outside the Arctic ocean proper then perhaps you get a swift reduction of this smaller amount of ice but then the ice loss stalls before it can get going within Arctic Ocean proper?

I guess I can see that as a possibility with Okhotz and Bering. But there is a much wider ocean/ice boundary for Barents, Kara. The shape of the extent graphs seems to me to typically continuing to accelerate the ice loss rather than showing a stall at a particular level.

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The last three convince me to think that extent curve flattens and slowly merges with previous years curves in April after a two month plateau.

Not sure how you arrive at this. There seems an argument for an earlier peak and one for a later peak. Does this drive a longer more level top of the curve? Or is it more a case of determining whether the later peak or earlier peak is the stronger effect? I suggest that the data show that for a big change in extent level like happened after 2007 the later peak wins but without a significant change in extent an earlier peak tends to win. So the peak is mainly moving to a lower level with little change in date of peak.

Perhaps there are arguments for a longer flatter peak, but I am not seeing them in what you have written, but perhaps that is just me failing to understand the reasoning you labelled as '3'.

Minimums are moving downward faster than maximums. Doesn't that tend to suggest a lower left shoulder rather than longer flatter peak?

oren

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Re: The 2016 melting season
« Reply #106 on: March 27, 2016, 07:11:08 AM »
seaicesailor - my intuition goes along with yours, though in less scientific terms.
I feel like there is the freezing season, the melting season, and the nothing/plateau season in between. Cold is not enough to produce lasting freezing in the marginal areas, heat and sunlight are not enough to produce significant melting, so it goes back and forth for a while.

Jim Hunt

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Re: The 2016 melting season
« Reply #107 on: March 27, 2016, 06:27:27 PM »
As the intrepid Russians build ice camp Barneo 2016 the intrepid Americans have been forced to abandon Ice Camp Sargo in a hurry:

http://www.navytimes.com/story/military/2016/03/25/ice-ex-ends-abruptly-cracks-in-the-ice/82248404/

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A crack through the Navy's Arctic ice camp forced submariners and researchers to break camp in a hurry Thursday.

More than 40 international researchers and personnel were evacuated by aircraft back to the U.S. after the crack was discovered, bringing the Navy's biennial ice station to a premature close, according to two officials familiar with the exercise. The operation, which began in early March, was slated to run another week.



There's also video of the USS Hartford surfacing near Ice Camp Sargo:


« Last Edit: March 27, 2016, 06:34:35 PM by Jim Hunt »
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Laurent

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Re: The 2016 melting season
« Reply #108 on: March 27, 2016, 07:40:47 PM »
That's because Russians know how to swim... hum, hum.

BornFromTheVoid

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Re: The 2016 melting season
« Reply #109 on: March 27, 2016, 08:19:20 PM »
I'll call the 5 day NSIDC max as March 24th, at 14.52 million km2.

seaicesailor

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Re: The 2016 melting season
« Reply #110 on: March 28, 2016, 01:15:56 AM »
Not sure I am following what you wrote correct ...

Hi Crandles, thanks for your answers. I am short of time for a proper response but suffice to say I agree on many of the points you make particularly for debunking my point 1 and 2 but there are other comments Id argue. One thing, I intended to say that curve flattens earlier (not that the max is strickly in Freruary but the chances grow)  and stays around similar values until early April (not that the max occurs in April either) just as Oren implies too. Anyway the exact date is relevant but not so important.

One thing though related to my point 3:  you probably wondered why extent curves collapse so closely about May? No matter how thin ice comes out of winter, no matter how low the extent can fall in September, the spread of extents during this month is pretty small. Maybe there is an answer to this that I dont know, but my first bet would be that outer seas getting depleted of ice while the main ice retrat still on the brew. But I give you the extent already is falling considerably because Hudson, Baffin come later, then Kara and possibly Chukchi and Beaufort are already opening up (Barents is more trecharous AFAIK).

Neven

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Re: The 2016 melting season
« Reply #111 on: March 28, 2016, 10:08:09 AM »
I've finally found the energy and motivation to write the 2015/2016 Winter analysis, a synthesis of the many things discussed over here on the ASIF.

Conclusion: Pacific side looks weak, more ice on the Atlantic side, ideally positioned for Fram Strait export.
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Lord M Vader

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Re: The 2016 melting season
« Reply #112 on: March 28, 2016, 11:08:52 AM »
Fair to say that the melting season really have started. Last couple ofdayshave seen adropof about 130K. St Lawrence will most likely begone with the wind in 1-2 weeks or so. PIOMAS for March will likely show an increase in the volume, especially on the Atlantic side.
If the AO continues to be positive for the next months I find it unlikely that we'll see a new SIE record minimumthis year. The last few years have seen a dominance of positive AO.I don't think this will change much this year but if the index should go negative during june-july it certainly should have a big impact on tje minimum. The dominance of +AO won't last forever.

Another thing to look at is how all that heat from El Nino will impact the sea ice.

Meirion

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Re: The 2016 melting season
« Reply #113 on: March 28, 2016, 11:29:24 AM »
The AARI is definitely a brown sheep this time

Neven

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Re: The 2016 melting season
« Reply #114 on: March 28, 2016, 12:02:54 PM »
The AARI is definitely a brown sheep this time

Indeed. A ram, even. Hadn't noticed it.  ;D
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oren

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Re: The 2016 melting season
« Reply #115 on: March 28, 2016, 02:04:42 PM »
The AARI is definitely a brown sheep this time

The similarity is striking. I almost thought you had it photoshopped.

6roucho

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Re: The 2016 melting season
« Reply #116 on: March 28, 2016, 03:12:20 PM »
The AARI is definitely a brown sheep this time

Indeed. A ram, even. Hadn't noticed it.  ;D
A strangely womb-like scene. That ram lamb will never fit out the Fram.

jai mitchell

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Re: The 2016 melting season
« Reply #117 on: March 28, 2016, 06:47:16 PM »
http://www.huffingtonpost.com/entry/alaska-pavlof-volcano-erupts_us_56f90f3ae4b0143a9b4890da?ir=Science&section=us_science&utm_hp_ref=science

Alert Levels Raised As Alaska’s Pavlof Volcano Spews Ash 20,000 Feet Into The Sky
Smoke started spurting at 4:18 p.m. local time on Sunday.

Location with current 250 mb jet stream patterns:  http://earth.nullschool.net/#current/wind/isobaric/250hPa/orthographic=-159.92,55.36,1024/loc=-162.006,55.473

Currently the strong pacific ridge is causing most of the upper troposphere aerosols to stay out of the Polar Atmospheric Cell, some small percentage (less than 25%) may migrate and impact the coming warming/melt season.  If the eruption continues for a long-period and/or if the upper wind pattern changes then this may create significant reductions in temperature/insolation and ice melt through the coming season.

1 week ahead projections show a much stronger likelihood of volcanic aerosols becoming captured by the Polar Atmospheric Cell.  http://earth.nullschool.net/#2016/04/02/1200Z/wind/isobaric/250hPa/orthographic=-160.57,69.66,1024/loc=-161.609,55.660
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crandles

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Re: The 2016 melting season
« Reply #118 on: March 28, 2016, 06:59:52 PM »
Do you think that is 20000 feet above the summit at 8261 feet or to a height of 20000 feet above sea level?

Is 20000 feet above sea level insufficient to reach stratosphere and therefore not able to stay suspended for some time?

So effect could mainly be restricted to albedo and melting point of snow assuming it reaches Alaska or sea ice covered oceans?

jdallen

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Re: The 2016 melting season
« Reply #119 on: March 28, 2016, 07:19:05 PM »
Do you think that is 20000 feet above the summit at 8261 feet or to a height of 20000 feet above sea level?

Is 20000 feet above sea level insufficient to reach stratosphere and therefore not able to stay suspended for some time?

So effect could mainly be restricted to albedo and melting point of snow assuming it reaches Alaska or sea ice covered oceans?
While 20,000 feet sound like a lot, it is measured from sea level, not the summit.

Also, any activity with a VEI of less than 4 is not going to produce enough aerosols to significant affect insulation, even if restricted to the Arctic cell.  I haven't checked numbers, but this explosion is probably only a "2", if that.  In summary - the coming wildfire season will have a far greater impact than this activity.
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Steven

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Re: The 2016 melting season
« Reply #120 on: March 28, 2016, 08:54:14 PM »
Do you think that is 20000 feet above the summit at 8261 feet or to a height of 20000 feet above sea level?

According to the latest update from Alaska Volcano Observatory, the Pavlof volcanic ash plume is now up to 37,000 feet above sea level:

Quote
Issued: Monday, March 28, 2016, 8:34 AM AKDT
...
Recent Observations:
[Volcanic cloud height] 37,000 ft ASL in SIGMET
[Other volcanic cloud information] Extending for 400 miles to the NE as of 07:00 UTC

https://www.avo.alaska.edu/activity/search_reports_results.php?volcano=ak210
« Last Edit: March 28, 2016, 09:24:03 PM by Steven »

Andreas T

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Re: The 2016 melting season
« Reply #121 on: March 28, 2016, 10:20:00 PM »
At this altitude the top of the ashcloud shows up as a cold streak in this nighttime IR image. Note some other volcanos standing out because of their altitude.

jai mitchell

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Re: The 2016 melting season
« Reply #122 on: March 28, 2016, 11:34:16 PM »
Ash Cloud is not Sulfur Dioxide height.  Sulfur Dioxide will necessarily migrate higher. 

Tropopause height at 55'N latitude is (roughly) 28,500 feet.  This is a strato-volcanic event.
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Csnavywx

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Re: The 2016 melting season
« Reply #123 on: March 29, 2016, 03:20:47 AM »
Ash Cloud is not Sulfur Dioxide height.  Sulfur Dioxide will necessarily migrate higher. 

Tropopause height at 55'N latitude is (roughly) 28,500 feet.  This is a strato-volcanic event.

Normally. It isn't right now because of a massive omega block setting up over the region. Current Skew-Ts have the tropopause near 40kft. In fact, the 37-38.5k figures listed for plume height are probably accurate as the plume spreads under the tropopause. Jet config will also cause the ash cloud to curl around the block and spread east and then southeast as it heads inland. The block will be stable for at least several days.

jdallen

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Re: The 2016 melting season
« Reply #124 on: March 29, 2016, 06:31:06 AM »
Ash Cloud is not Sulfur Dioxide height.  Sulfur Dioxide will necessarily migrate higher. 

Tropopause height at 55'N latitude is (roughly) 28,500 feet.  This is a strato-volcanic event.

Normally. It isn't right now because of a massive omega block setting up over the region. Current Skew-Ts have the tropopause near 40kft. In fact, the 37-38.5k figures listed for plume height are probably accurate as the plume spreads under the tropopause. Jet config will also cause the ash cloud to curl around the block and spread east and then southeast as it heads inland. The block will be stable for at least several days.

It is *still* not enough volume to make a significant difference.  It's most likely well under 1/10th KM3 of material, even including compressed volatiles like SO2 and CO2.  The silicate ash itself will be net neutral regarding atmospheric heating.
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jai mitchell

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Re: The 2016 melting season
« Reply #125 on: March 29, 2016, 06:44:30 AM »
[The block will be stable for at least several days.

Agreed, it looks like it will move off at 0000 UTC on April 1st.

However, It seems to me that the rate of SO2 emission has a much stronger potential to move across the tropopause.  Estimates of anthropogenic SO2 emissions moving into the stratosphere are (if I recall correctly) around 2-3% of total annual emissions.
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jdallen

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Re: The 2016 melting season
« Reply #126 on: March 29, 2016, 08:25:50 AM »
I really think we are making far too much of the potential SO2 emissions from this eruption.  Pinatubo, which had over 50 times the emission of ash and volatiles (probably more like 100-200 times...) than the current event at Pavlof, reduced global temperatures by only 0.6C .

The volcanoe's proximity to the arctic really won't make that big a difference either.

This eruption really isn't going to significantly alter what happens during the melt season.
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jai mitchell

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Re: The 2016 melting season
« Reply #127 on: March 29, 2016, 05:50:02 PM »
Pinatubo was a southern hemisphere tropical event.  The distribution of aerosols from volcanic activity on a globally averaged temperature impact was great but impacts to the arctic sea ice were minimum.  Volcanic activity in the arctic disproportionally affects that region but has little-or no effect on globally averaged temperatures, with the possible exception of a super-eruption from iceland which did both (due to scale of eruption). 

the 2011 iceland eruption lasted about 3 days and had an ash plume rise to 20k feet and drop to 10k feet elevations after 1 day. 

We can only wait and see from this point.
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jdallen

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Re: The 2016 melting season
« Reply #128 on: March 29, 2016, 07:19:02 PM »
Pinatubo was a southern hemisphere tropical event.  The distribution of aerosols from volcanic activity on a globally averaged temperature impact was great but impacts to the arctic sea ice were minimum.  Volcanic activity in the arctic disproportionally affects that region but has little-or no effect on globally averaged temperatures, with the possible exception of a super-eruption from iceland which did both (due to scale of eruption). 

the 2011 iceland eruption lasted about 3 days and had an ash plume rise to 20k feet and drop to 10k feet elevations after 1 day. 

We can only wait and see from this point.
Minor Kvetch - 15.14° N, 120.34° E  - Not southern hemisphere.

But yes, we need to wait and see.
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jdallen

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Re: The 2016 melting season
« Reply #129 on: March 29, 2016, 08:12:07 PM »
Sometimes I can't help myself.

I've dug up a list of all of the near-arctic - Kamchatka/Kuril, Aleutian, Alaskan and Icelandic - VEI 2+ eruptions in the last 20 years that I could find.  They are listed below.

I also want to point out early in 2015, there were a number of significant eruptions on the same scale as what we are seeing with Pavlof.  They do not appear to have significantly affected the melt season outcome.

I want to emphasize, I think it is easy to overestimate the impact of one of these volcanic events.  They are a lot more common than most people realize.  A VEI 4 (like Eyjafjallajokull in 2010 and Grimsvotn in 2011)  while enormously disruptive of our lives had negligible impact on the arctic melt or refreeze seasons.

http://www.kscnet.ru/ivs/kvert/index_eng.php
http://volcano.si.edu/

VolcanoDateVEI
Cleveland201312283
Veniaminof201306133
Pavlof201305133
Kanaga201210302
Cleveland201107202
Cleveland201009122
Cleveland201005302
Cleveland201005273
Cleveland200910022
Cleveland200906252
Redoubt200903153
Cleveland200901022
Kasatochi200808074
Omok200807124
Pavlof200708152
Cleveland200706172
Fourpeaked200609172
Cleveland200602063
Augustine200512093
Cleveland200503132
Veniaminof200501042
Shishaldin200402172
Veniaminof200402162
Cleveland200102023
Shishaldin199903133
Korovin199805083
Cleveland199705052
Omok199702113
Pavlof199607112
Shshaldin199512233
Klyuchevskoy20150828? (2+)
Karymsky20150119? (2+)
Klyuchevskoy20150101? (3+)
Zhupanovsky201406063
Zhupanovsky201310233
Chirinkotan20130611?
Tolbachhik20121127?
Alaid201210052
Kizimen201011113
Ekarma201006302
Bezymianny201005213
Bezymianny200912173
Klyuchevskoy200908012
Sarychev Peak200906114
Koryaksky200810082
Chikurachki200807292
Bezymianny200806113
Chikurachki200708192
Bezymianny200705103
Chikurachki200708192
Klyuchevskoy200702152
Bezymianny200604003
Bezymianny200511292
Ebeko200501292
Klyuchevskoy200501202
Chirinkotan200407202
Bezymianny200401143
Bezymianny200307263
Chikurachki200304172
Bezymianny200212242
Klyuchevskoy200204092
Chikurachki200201252
Bezymianny200112102
Karmsky200111153
Bezymianny200107233
Klyuchevskoy200007282
Bezymianny200007182
Mutnovsky200003172
Bezymianny200003142
Klyuchevskoy200002032
Sheveluch199907154
Sheveluch199902252
Klyuchevskoy199902052
Klyuchevskoy199807232
Sheveluch199805303
Bezymianny199712053
Bezymianny199705083
Sheveluch199703082
Alaid199612032
Klyuchevskoy199611142
Karymsky199601023
Akademia Nauk199601023
Bezymianny199509013
Grimsvotn201105214
Eyjafjallajokull201003204
Grimsvotn200411013
Hekla200002263
Grimsvotn199812183
Grimsvotn199609303
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Neven

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Re: The 2016 melting season
« Reply #130 on: March 29, 2016, 11:36:44 PM »
Nice work, jdallen.  :)

It's a small annual milestone, but the black hole on the LANCE-MODIS Arctic Mosaic has disappeared, meaning that light has now reached the North Pole.

Somehow as I typed that, I thought it might be incorrect. Please correct, if so.
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Flocke

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Re: The 2016 melting season
« Reply #131 on: March 30, 2016, 07:39:17 AM »
The center of the sun should have passed the horizon at the north pole at 4:30 on 20th March.

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Re: The 2016 melting season
« Reply #132 on: March 30, 2016, 08:29:33 AM »
Cryosphere Today shows an uptick in arctic ice extent.  Is now the highest of 2016 at 12.8993 on day 87.  So I guess ice is still growing?

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Re: The 2016 melting season
« Reply #133 on: March 30, 2016, 08:41:34 AM »
Thanks, Flocke! So, it took around 10 days for there to be enough light at the pole for the satellite sensor to 'see' the ice.

Cryosphere Today shows an uptick in arctic ice extent.  Is now the highest of 2016 at 12.8993 on day 87.  So I guess ice is still growing?

Welcome, Skier. Over on the 2016 sea ice area and extent data thread Wipneus wrote:

Quote
A big century drop almost certainly ends the march to the top, and starts the race to the bottom.

From today's NSIDC sea ice concentration data I calculate sea ice area, in the Cryosphere Today way. Here "day" is the day that CT normally publishes that data for the Northern Hemisphere, SH and global normally follow the next day. "CT-date" is approximately the date that CT uses.
When NSIDC does not revise its concentration data (they do occasionally), my values are normally accurate within a few k. Uncertainties are the exact algorithm for assumed concentration in the pole hole and some subtleties handling bad data.

day  CT-date       NH               SH                Global
Tue 2016.2356   +8.2 12.899085 +111.1  3.600973  +119.2 16.500058
Wed 2016.2384  +22.1 12.921232 +120.3  3.721245  +142.4 16.642477
Thu 2016.2411 -124.4 12.796836 +104.9  3.826190   -19.5 16.623026

It looks like CT SIA has peaked as well. Given the forecast and the time of year I don't expect it to bounce up 125K or more.
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Entropy101

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Re: The 2016 melting season
« Reply #134 on: March 30, 2016, 09:05:05 AM »
The Pinatubo was a VEI 6 event. The current event is rated at VEI 3? Since the VEI scale is a base 10 scale, a VEI 6 is a 1000 times more powerfull than a VEI 3. So we will need 1000 eruptions of this scale or a 100 Eyjafjallajokulls to get to a Pinatubo size event and the effect on weather that was associated with that.

So as jdallen mentioned, this single eruption will not have a significant influence on the melt season.

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Re: The 2016 melting season
« Reply #135 on: March 30, 2016, 10:09:22 AM »
Vigorous snow melt underway over the W/NW region of North America.

Snow melt has also erupted over Western Russia reaching well into the interior.

This is earlier than 2014.  But even with 2015.

But earlier than 2010 and way earlier than 2009.

Expect the snow cover departure anomalies to slowly grow the next few weeks.

Also air running like 20C above normal is being brought into the Kara and Nansen basin.

Thanks to parents ssts being upwards of 3-5C above normal over large regions low level air masses are much warmer than historical norms as they reach the ice edge in that region.

The current flow is pumping warm air directly into the ice.

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Re: The 2016 melting season
« Reply #136 on: March 30, 2016, 10:20:21 AM »
Modus shows a full surface albedo drop over the Southern Kara showing surface melt starting.

Today's imagine is hopefully a but more clear.

The average temp is -18C over the Southern Kara right now.


 
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Re: The 2016 melting season
« Reply #137 on: March 30, 2016, 11:26:46 AM »
That is insane.


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Re: The 2016 melting season
« Reply #138 on: March 30, 2016, 11:36:37 AM »
You're right, Friv. NH snow cover has been going down again, lowest in the recent record:
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Re: The 2016 melting season
« Reply #139 on: March 30, 2016, 11:38:52 AM »
Oh yeah.  The Kara surface melt on today's image has expanded.

Incredible
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Re: The 2016 melting season
« Reply #140 on: March 30, 2016, 12:01:51 PM »
Oh yeah.  The Kara surface melt on today's image has expanded.

Incredible

Can you share that image here?

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Re: The 2016 melting season
« Reply #141 on: March 30, 2016, 01:16:13 PM »
Groundhog day is coming....again ???

More warm Arctic air....with anomaly getting above the +5 C level is coming in about 6 or 7 days per CCI.

The same region which was wracked by warmer than normal weather in Jan and Feb:  The area from northern Greenland....across Svalbard and Franz Joseph....to the Barents and Kara Seas off the central/northern coast of Russia.

Not good.....




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Re: The 2016 melting season
« Reply #142 on: March 30, 2016, 01:52:01 PM »
North of Swalbard is even more impressive to me. http://go.nasa.gov/1UUgffY

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Re: The 2016 melting season
« Reply #143 on: March 30, 2016, 02:23:49 PM »
Modus shows a full surface albedo drop over the Southern Kara showing surface melt starting.

Today's imagine is hopefully a but more clear.

The average temp is -18C over the Southern Kara right now.
Shouldn't this be caused by ice drift, strictly speaking? No signs of direct surface melting like bluer tonality. Refrozen parts detached from the coast have sharp boundary and don't look to be melting yet.
Albedo drop, yes.



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Re: The 2016 melting season
« Reply #144 on: March 30, 2016, 05:25:54 PM »
I agree that ice edge retreat isn't always melting and the area shown by Laurent, east of Svalbard does look much more like the is ice being pushed back by wind. What is noteworthy is that 10 days ago with wind from the northeast the water opening in the lee of Franz Josef Land was freezing over, now with a southeasterly direction the water stays open without refreezing.

Directly north of Svalbard it is remarkable that the ice edge has retreated north with the general drift of the pack along and towards it. This seems to indicate sufficiently warm water to cause melt. Air temperatures measured on Svalbard only briefly reached up to 0 deg.

see the Svalbard thread I started.
Thanks Jim, that helps.
My comment is based on tracing floes (following the shape day by day on worldview is more convincing than the images below) and seeing ice between that floe and the edge disintegrate but it seems that it should spread out more if it would only break up without any melting.
interesting is also how the gaps opening between floes in the pack freeze over while the cold air doesn't manage to do that south of the edge (as far as I can see)

and south of Svalbard there is definitely melting ice (disappearing)

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Re: The 2016 melting season
« Reply #145 on: March 30, 2016, 05:30:23 PM »
Here's the thing regarding the Kara, Barents and near-Atlantic pack.  The significantly increased temperatures, and high temperature of the ice has a direct and measurable effect on the ice's compressive and tensile strength.  The abstract of this article citation has a summary good enough for my purposes.

http://link.springer.com/article/10.1023%2FA%3A1021134128038

Between -20C and -10C, the compressive strength of ice decreases by a factor of *5*.  So, even with similar volumes, we can be very confident that because of much higher ice temperature, not just earlier in the season, but before the *start* of the melt season the ice will begin disintegrating almost immediately when subjected to kinetic force.  I think the satellite imagery bears that out.

So, while I do think the temperatures are still far to low to support surface melting, the highly elevated temperatures, not just now, but over the entire season are responsible for what we see currently.  This isn't a result of current conditions; this is a result of the entire winter's conditions.  It is also why we really can't take much comfort in the lead ice appearing from refreezing.  Once there is no longer enough heat export to maintain it, it will rapidly turn not just into ice cubes, but slush.  It is a qualitative difference between 2016 and previous years, and a very negative one.
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Re: The 2016 melting season
« Reply #146 on: March 30, 2016, 08:43:58 PM »
Here's the thing regarding the Kara, Barents and near-Atlantic pack.  The significantly increased temperatures, and high temperature of the ice has a direct and measurable effect on the ice's compressive and tensile strength.  The abstract of this article citation has a summary good enough for my purposes.
Strange. I always assumed the energy compressing ice was released via formation of pressure ridges. Keeping a 1 to 2 m ice cap compressed over thousands of km2 seems a mighty unstable situation to me.
Likewise, fractures quickly release the stretching of ice.

Ice seems a pretty fragile matter being a crystal. Shouldn't we be talking about resiliency/fragility rather than structural strengths?

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Re: The 2016 melting season
« Reply #147 on: March 30, 2016, 09:36:17 PM »
Here's the thing regarding the Kara, Barents and near-Atlantic pack.  The significantly increased temperatures, and high temperature of the ice has a direct and measurable effect on the ice's compressive and tensile strength.  The abstract of this article citation has a summary good enough for my purposes.
Strange. I always assumed the energy compressing ice was released via formation of pressure ridges. Keeping a 1 to 2 m ice cap compressed over thousands of km2 seems a mighty unstable situation to me.
Likewise, fractures quickly release the stretching of ice.

Ice seems a pretty fragile matter being a crystal. Shouldn't we be talking about resiliency/fragility rather than structural strengths?
The lower strengths - tensile similarly declines by a factor of 4 over that span of temperature - reduce the ice's resistance on a larger scale.  It breaks into smaller pieces, and I would expect rather than forming durable ridges, shatters into melange - much as you see rock in fault zones ground into rubble.  That may be a good metaphor for it as well - rather than being shaped into new structures, it gets ground into rubble, which while it might get lightly welded by some freezing, doesn't gain the durability required to be persistent.

It means also that larger structures - think multi KM stretches of ice - cease to have the strength required to resist internal stresses, and break down more easily into smaller elements than the colder, stronger ice.

We've seen very good evidence supportive of this over the last few years of observation in these forums.

This year becomes even more exceptional, as for significant stretches of the main basin, as well as the peripheral seas, we've seen temperatures so high that the pack has never had sufficient opportunity to consolidate, thicken, cool and strengthen.  Buoy temperatures where we have them pretty consistently indicate temperatures considerably above -20C, which was not the case if you go back a few years.  I vaguely recall looking at temperature profiles in late spring ice, 3M thick, with core temperatures still close to -20C.

The breakage issue is important mechanically for a number of reasons I think.

1) water column turnover.  More movement of ice and direct access to sea surface by wind will increase Eckman pumping and transfer of heat from depth to the surface.

2) Lateral melt.  Melting profiles in different studies tend to suggest that lateral melting does not contribute significantly to volume loss until your flow size drops down under about 100M or so.  Once that threshold is reached, lateral melt contribution increases geometrically as the diameter decreases.  It's pure arithmetic - you decrease flow size, you increase the area available to attack by sea water.  You decrease the coherence of the ice - it's ability to maintain large expanses of unbroken ice - and you can see how the pack is evolving to a point where this will be an issue.

3) Mechanical attack by waves.  We don't need collisions or compression to cause ruptures.  With the ice significantly reduced in strength, where ever we see significant leads and fetch for wind, it will be far more prone to break up than in the past.  Further, it will do so much earlier in the season.

4) More sea surface open to insolation.  We won't need as much in the way of melt ponding to DEcrease albedo if, poorly consolidated ice ruptures, gets dispersed by movement, and opens sizeable leads.  That was part of what was at work in 2015.  I think it will only be worse this year, and may start earlier. *Has* started earlier.

Timing is important here.  In the past, the ice would weaken, and that you would see significant reduction in strength over large stretches of the Arctic - but not until fairly late in the season.  Even then, even in years like 2007, 2010, 2011 even 2012... you still had pretty sizeable stretches of ice which retained fairly high coherence.  That really hasn't been true since 2013 onwards, if you consider the megacracking events we've seen, and the near complete atomization of the pack such as we saw in 2013.  That year in particular, we were saved by nothing more than the whims of the weather and a cold freezing season.

We haven't had that for two years now.

I will be watching how the pack evolves over the early melt season with great interest.

[Edit:  One more thing occurs to me - higher temperatures means brinier ice.  It won't have had as much time or good conditions to "desalinate".  That should translate into lower melting temperatures, closer to the current SST.  Bottom melt will start sooner.]
« Last Edit: March 30, 2016, 09:46:35 PM by jdallen »
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Re: The 2016 melting season
« Reply #148 on: March 30, 2016, 09:54:42 PM »
Ice which undergoes compressive failure makes pressure ridges. Pressure ridges are a way of increasing average thickness of ice. The people setting up Barneo icecamp are reporting having to clear more ridges than in previous years to built their runway to land planes on the ice.
The interesting question isn't whether the ice is less strong than in other years, the interesting question is what consequences that has. If the ice compacts against the north coast of Greenland it stores volume where it keeps over the summer. If it moves into places where it gets too warm it increases volume loss.
Ice has always cracked, the stresses over such a large area are just too huge not to.
Increased melting around the periphery is giving it space into which the ice can spread. That spreading with the opening of water between floes in the summer is what could have a big effect. But it still needs time and the right weather conditions over a short melting season.

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Re: The 2016 melting season
« Reply #149 on: March 30, 2016, 10:22:53 PM »
Ice which undergoes compressive failure makes pressure ridges. Pressure ridges are a way of increasing average thickness of ice. The people setting up Barneo icecamp are reporting having to clear more ridges than in previous years to built their runway to land planes on the ice.
The interesting question isn't whether the ice is less strong than in other years, the interesting question is what consequences that has. If the ice compacts against the north coast of Greenland it stores volume where it keeps over the summer. If it moves into places where it gets too warm it increases volume loss.
Less consolidated ice, more cracking. I will add - I expect those individual ridges to be smaller as well - less force to compress the ice as the stress is distributed across more failures.  They will have more opportunity to relieve it through movement rather than physical deformation.  The same basic mechanism you'd see in strike/slip faults - which essentially is what the ridges are in miniature - fault zones in the ice.

Limited opportunity for this as most of the cracking will be well away from areas which are stable.



Ice has always cracked, the stresses over such a large area are just too huge not to.
Increased melting around the periphery is giving it space into which the ice can spread. That spreading with the opening of water between floes in the summer is what could have a big effect. But it still needs time and the right weather conditions over a short melting season.

Absolutely true - but what is different, is the cracking now takes place at a much smaller scale - instead of ruptures at 1 or 2KM, we see multiple ruptures across the same expanse.  The ice isn't as resistant.


Very much to the point and yes, weather will be key.  But even with favorable conditions for ice retention, we will still see a minimum of well under 5M KM2.  Average for the last few years takes us down under 4 Million.  Unfavorable flirts with 2012.
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