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F.Tnioli

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Re: The 2014 Melting Season
« Reply #3150 on: August 14, 2014, 02:42:44 PM »
To the moderators:

Could we please move the geoengineering posts from this location to a new or different thread?

This is a topic for which there is far more heat than light, and which is clogging this thread with OT posts.  Relocating them would by nature refocus the discussion.
Procedural note. Since i was involved, i find it rational to hereby express complete absense of any objections to the quoted jdallen's proposal. The topic which started by ChrisReynolds - http://forum.arctic-sea-ice.net/index.php/topic,958.0.html - would be a good place for such move. This post, if the move would be done, will then be not needed, and i will not object if this post will therefore be permanently deleted from this topic and forum.
To everyone: before posting in a melting season topic, please be sure to know contents of this moderator's post: https://forum.arctic-sea-ice.net/index.php/topic,3017.msg261893.html#msg261893 . Thanks!

Neven

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Re: The 2014 Melting Season
« Reply #3151 on: August 14, 2014, 03:33:20 PM »
Even if I could move comments from one thread to another, I wouldn't have the time or motivation to do it.

Wouldn't it be much easier if everyone just stayed on topic from now on?
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Re: The 2014 Melting Season
« Reply #3152 on: August 14, 2014, 04:34:51 PM »
Over the last couple of weeks, both Navy thickness models show the thick MYI just north of the CAA breaking free of land and moving west. First the western section breaks off around Aug 1, then the entire thing breaks off around Aug 6.

1. Is this real?
2. Is it normal?
3. Is it bad (for long-term ice preservation), good, or neither?


This kind of ice movement is normal and happens in any season. You can see the normal counterclockwise movement of the Beaufort Gyre in the ice drift maps posted by Frivolousz21 above.

For the last big blocks (or blobs?) of the thickest ice to break loose and drift away to the south is another matter. Maybe someone else can answer. The thick ice that moved to the Beaufort Sea and beyond since last summer melted away this summer.

Comradez

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Re: The 2014 Melting Season
« Reply #3153 on: August 14, 2014, 05:03:12 PM »
If anyone is curious about how to calculate the point in the transition into fall at which certain parts of the arctic can be expected to be giving off a net heat loss rather than getting a net heat gain from solar radiation to melt ice, here are some tools I've found.  First, you start with this well-known graph showing lattitude vs. date vs. insolation:



Then you can go to this handy Stefan-Boltzmann law calculator here:

http://www.endmemo.com/physics/radenergy.php

To find out the emissivity of the Earth (under clear skies), I went here:

http://rabett.blogspot.com/2008/02/why-it-pays-to-have-clever-anonymice.html

So, if you punch "0.96" into the emissivity field, and 273 K into the temperature field, and "1" into the meters^2 field, you get...302 Watts.  So, the Earth will lose 302 W/m^2 at 273 K (0 Celsius). 

So, really, to be gaining net heat to melt ice, a part of the Earth needs to be getting more than 300 W/m^2.  (Otherwise, melting can only happen through heat transport from other parts of the ocean and atmosphere that are getting more than 300 W/m^2, or that have heat stored up in water that is significantly above 0 Celsius). 

In our first graph, 90-North dips below the 300 W/m^2 insolation mark at about August 20th.  60-North dips below 300 W/m^2 by about September 5th.  We can guess that 75-North would be about August 30th. 

There's only about another 1-2 weeks left where the sun still matters, folks!  After that, clouds become the friend of (next year's) sea ice melt.  A cloudy sky drops the emissivity all the way down to 0.5.  That almost halves the lost heat to space.  If you drop the temperature down to 243 K (-30 Celsius) and assume cloudy skies, then the heat lost to space in the winter is only 98 W/m^2. 

Here's a math problem:  let's imagine that the arctic was totally cut off from the rest of the climate system.  Whatever ice it had to melt in the summer, it had to do on its own yearly budget.  How cold would it need to get in the winter to balance the budget? 

Let's say that the arctic gets about an average of 350 W/m^2 for the six months of the melt season.  Let's imagine that it is losing 300 W/m^2 during those six months (because the temperature is brought up to 0 Celsius).  That's a net gain of 50 W/m^2 over six months, or overall, the arctic would soak up 4,320 Watt-hours/m^2 over that melting season. 

On the flipside, there are six months where the average insolation is maybe 50 W/m^2.  That would mean that the arctic would be able to afford to lose only 100 W/m^2 on average in order to end up with the 50 W/m^2 net loss over six months to lose the 4,320 accumulated Watt-hours/m^2. 

One way to lose 100 W/m^2 is to have cloudy skies (emissivity = 0.5) and an average temperature of 243 K (-30 Celsius).  But what if the skies are clear (emissivity = 0.96)?  Then you'd need the average temperature in the arctic in the winter to get down to about 205 K (about -68 Celsius) to lose only ~100 W/m^2.  What if the emissivity were 0.64 (which is what some estimate to be the average emissivity of the atmosphere, factoring in cloudy and clear days)?  Then you could get away with having an average arctic temperature of 228 K (-45 Celsius) and still manage to lose only an average of 100 W/m^2 over those six months (50 W/m^2 net loss). 

Since the average arctic temperature from September to March is probably a little bit above -45 Celsius, we can tell that the arctic is receiving substantial heat inputs from the lower lattitudes. 

Next math problem:  how much more would first-year ice thicken with an average temperature of -45 Celsius over a six-month freezing season compared to how much it tends to thicken now with whatever the average temperature from September to March is now?  ;D

Comradez

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Re: The 2014 Melting Season
« Reply #3154 on: August 14, 2014, 05:19:16 PM »
Another thought just occurred to me:  given a certain sea ice volume, the most efficient way to melt ice is NOT to have a clearly-delineated area of open ocean that heats up to 283 K and a solid area of sea ice that doesn't get much of that heat.  No, the most efficient way to melt sea ice is to have the volume and area be widely-dispersed (high extent, low area = low CAPIE), such that most of the water is at 273 K, and most of the heat is going directly into melting sea ice rather than being radiated out to space. 

A body of water at 283 K (10 Celsius) under clear skies is LOSING TO SPACE 349 W/m^2.  If that same water were at 273 K, it would only be losing 302 W/m^2.  That's almost 50 W/m^2 of difference!

That 10-degree Celsius water in the Laptev right now would be doing much more work against the sea ice if it were, with the same amount of heat, sitting in little pockets in the middle of the Central Arctic Basin at 0 Celsius.  It would have 50 W/m^2 more heat flux with which to do useful work against the ice.  That's big!  That's the difference between the CAB having experienced a -30 Celsius winter and a -45 Celsius winter right there!

Perhaps this is why the June CAPIE index is such a good predictor of September sea ice measures - not necessarily because melt ponds or cracks indicate volume that has already been lost, per se, but because melt ponds and cracks at that time of year allow the heat to actually do more work on the sea ice where it counts, rather than get radiated into space in the southern Laptev like it is now.

ChrisReynolds

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Re: The 2014 Melting Season
« Reply #3155 on: August 14, 2014, 08:14:26 PM »
Comradez,

"There's only about another 1-2 weeks left where the sun still matters, folks!"

Agreed. But for much of the central pack, that point may in reality have been passed weeks ago.

Yes the most efficient way to melt the ice is to have high dispersion with open water between floes. That's leaving aside effects such as the vertical mixing from the August cyclone of 2012. Anyway radiation isn't the only effect, convective mixing is a way to take heat away from the surface too.

Your temperatures for winter in the Arctic are a bit high. Attached is a plot from NCEP/NCAR showing Dec/Jan/Feb surface temperatures, scaled from 0 to -40 in 3degC intervals. It's obtained from here:
http://www.esrl.noaa.gov/psd/cgi-bin/data/composites/printpage.pl
If you want me to explain I can, but not tonight. Perhaps a thread somewhere would be of use...

Lord M Vader

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Re: The 2014 Melting Season
« Reply #3156 on: August 14, 2014, 09:11:57 PM »
ChrisR, Neven, Friv et al: as we're talking about melting and the lack of strong winds an interesting possibility exists on EURO 12 OP run which as +240h shows a rather powerful cyclone that eventually could be able to penetrate into the Arctic from the Pacific.. I'm very well aware about the skill level on the forecast that far away, but at least it would be interesting to speculate what the impacts would be from a quite strong cyclone... At least as the melt season is closing to the end and we're far far away from any new record...

//LMV

Frivolousz21

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Re: The 2014 Melting Season
« Reply #3157 on: August 15, 2014, 12:01:34 AM »
ChrisR, Neven, Friv et al: as we're talking about melting and the lack of strong winds an interesting possibility exists on EURO 12 OP run which as +240h shows a rather powerful cyclone that eventually could be able to penetrate into the Arctic from the Pacific.. I'm very well aware about the skill level on the forecast that far away, but at least it would be interesting to speculate what the impacts would be from a quite strong cyclone... At least as the melt season is closing to the end and we're far far away from any new record...

//LMV

There is definitely going to be a sustained level of losses like we have been seeing the last week on Jaxa.  This is where 2014 is going to overtake 2009 and 2013.

NSIDC is picking up now as well.

The models keep wavering back and forth on the strength of the ridging but the mean flow stays in place for the foreseeable future.

The Chukchi open water area might be able to carve it's way to 80N.



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Bruce

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Re: The 2014 Melting Season
« Reply #3158 on: August 15, 2014, 02:16:47 AM »
The Chukchi open water area might be able to carve it's way to 80N.
I'm going to put that in the "extremely unlikely" category. There is a lot of solid, thicker ice between the current hole and 80N.

The question I'm asking is "Are the areas that are currently yellow and green on the AMSR2 maps going to melt out before they re-freeze?" Normally I'd say "no problem," but this year the ice has been very reluctant to melt. Barring some major weather event, I think we're unlikely to see more that about 750K of (extent) melt for the rest of the year.

Frivolousz21

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Re: The 2014 Melting Season
« Reply #3159 on: August 15, 2014, 03:45:31 AM »
It's not so much melting as the ice being compressed and moved.  The fetch is is thru the entire basin.

There is a lot more room for that then the concentrations appears to have.

I also disagree with only -750K the rest of the way.

If we assume at least -300K in September that would be only -25,000K per day on Jaxa the rest of the month.

Yesterday was -75K and the last week has been about -65K per day on average.  Just eye balling today's graphic I think tonight will be about -65K. 

With a dipole anomaly taking over it's extremely unlikely IMO that we only drop less than -400K between the 15th and 31st.

At -750K the rest of the season that would end 2014 at 5,227,575km2.  I can't see how that happens.

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cesium62

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Re: The 2014 Melting Season
« Reply #3160 on: August 15, 2014, 04:35:13 AM »
With a dipole anomaly taking over it's extremely unlikely IMO that we only drop less than -400K between the 15th and 31st.

At -750K the rest of the season that would end 2014 at 5,227,575km2.  I can't see how that happens.

It looks like the projections are for 20 knot winds through the Fram strait for three or four days.  Anyone want to take a stab as to how much ice would move through the Fram?  What's the width of the strait?  How far will ice move with a 20 knot wind for four days?

Frivolousz21

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Re: The 2014 Melting Season
« Reply #3161 on: August 15, 2014, 05:32:12 AM »
Jaxa dropped another -75K today.  Now down to 5.9 mil km2.

The pace of the drops has speed up a lot this past week.

2014 is going to close in and over take 2013 over the next 10 days.  2013 only drops -38K per day the next 10 days and -41K the rest of the month.

In order for 2014 to be at least tied with 2013 on September 1st it must average -47K drops the rest of August.

To be tied with 2009 on Sept 1st it has to only drop -35K per day.

To be tied with 2010 on Sept 1st it only has to drop  -43K per day.

To be tied with 2008 on Sept 1st it has to drop -63K per day.

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cesium62

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Re: The 2014 Melting Season
« Reply #3162 on: August 15, 2014, 06:09:04 AM »
With a dipole anomaly taking over it's extremely unlikely IMO that we only drop less than -400K between the 15th and 31st.

At -750K the rest of the season that would end 2014 at 5,227,575km2.  I can't see how that happens.

It looks like the projections are for 20 knot winds through the Fram strait for three or four days.  Anyone want to take a stab as to how much ice would move through the Fram?  What's the width of the strait?  How far will ice move with a 20 knot wind for four days?

I guess I can google that...  I'm getting: the Fram strait is 450km wide.  And http://nsidc.org/cryosphere/seaice/processes/dynamics.html says that ice moves at 2% of the wind speed.  Google says 20 knots is about 10m/s, so the ice would move about 0.2m/s.  4 days is around 400,000 seconds, so the ice moves 80 km.  So 36000km^2 of ice area would blow out through the Fram.  Looks like 36K is about one September day of ice loss...
« Last Edit: August 15, 2014, 06:27:25 AM by cesium62 »

Frivolousz21

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Re: The 2014 Melting Season
« Reply #3163 on: August 15, 2014, 06:29:11 AM »
That does seem quite low. 


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Bruce

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Re: The 2014 Melting Season
« Reply #3164 on: August 15, 2014, 06:29:55 AM »
I guess I can google that...  I'm getting: the Fram strait is 450km wide.  And http://nsidc.org/cryosphere/seaice/processes/dynamics.html says that ice moves at 2% of the wind speed.  Google says 20 knots is about 10m/s, so the ice would move about 0.1m/s.  4 days is around 400,000 seconds, so the ice moves 40 km.  So 18000km^2 of ice area would blow out through the Fram.  Looks like 18K is small compared to the other area/extent losses being mentioned.
Given the current state of the Greenland Sea, ice moving through the Fram will actually increase extent, not reduce it. At least until and unless it melts away. Which may or may not happen.

Friv, I can't argue with your numbers. But we're running out of daylight, so to speak. Right now it's a race as to whether the ice edge retreats faster than the freeze-up advances. But I agree with you that it's going to take some compaction -- I don't think a melt out like we're having in the Chukchi will be sufficient. But the current drift maps favor compaction, so who knows, maybe we will drop below 5M.

Michael Hauber

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Re: The 2014 Melting Season
« Reply #3165 on: August 15, 2014, 07:26:29 AM »
A tip for watching for the start of the refreeze - it has to get more than cold enough for snow to settle on land before ice will freeze in the ocean.  Whether it gets cold enough to freeze at the coldest part of the ocean (presumably at the pole) before it gets cold enough for snow to settle on the north shore of Greenland and Ellesmere island I'm not sure.

From trying to spot small gaps deep in the ice pack closing over in previous freeze seasons I suspect that the freezing zone starts only a few days or maybe a week before extent minimum and expands to the edge of the ice pack quite rapidly over this period.
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Lord M Vader

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Re: The 2014 Melting Season
« Reply #3166 on: August 15, 2014, 07:33:15 AM »
All years from 2007 and onwards have managed to scrape at least roughly 1 million km2 from this date to minima. (Remark my choice of words as 2013 saw a loss of 0,998 Mn km2...). Last year around this time temps above 80N had already dipped below freeze point and stayed much below normal until minima date. This year it seems that we actually have a incredible small positive anomaly right now according to DMI (first time this summer).

Seems very realistic to believe we'll see a minima around 4,75-4,99 Mn km2 this year.

Frivolousz21

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Re: The 2014 Melting Season
« Reply #3167 on: August 15, 2014, 07:47:15 AM »
There is plenty of time left for relatively large losses.

Remember to use context.  This year has more ice coverage on the Pacific side that isn't that thick at all. With the dipole and winds compacting from Alaska, Bering, and NE Russia air temps will be above normal with a long and steady wind fetch that goes all the way into the NATL.  The water is also relatively warm as well as the Pacific sub surface water that is only 40-50M below the ice over the Pacific side and closer to the ice in the ESS and parts of the Chukchi.

If this pattern persists into September we probably won't see the minimum for another 30 days maybe 35 if it blows up again around September 10th.

The Laptev sector probably won't start to refreeze until September 15th or later.  The Kara and Atlantic side are either full of ice or won't freeze up until late September.

If we have a warm flow from the Pacific into the Pacific basin it will prevent the ice from growing longer than normal.

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Re: The 2014 Melting Season
« Reply #3168 on: August 15, 2014, 10:42:50 AM »
The next 6 days at the least could potentially be the last major push for relatively large losses.  The OP models are having issues with continuity now in the medium range.

Euro ensemble mean doesn't agree with the OP.  Same ole same ole.







« Last Edit: August 15, 2014, 11:41:09 AM by Frivolousz21 »
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Re: The 2014 Melting Season
« Reply #3169 on: August 15, 2014, 11:56:46 AM »
Possible Fram losses.

I'm not sure where we are getting the response of the ice to the winds from? It appears a very low value? We are told that the ice moves a lot faster these days to to its thin, fragmented nature and the figs used in thr upthread calc just appear too small?

Once the pack is in motion I'd imagine that it does not take much to keep it moving?

I'd also agree that any transfer would not really impact extent/area negatively as the ice would still fall into the Greenland Sea ice area plot? My contention is that it takes good ice from the basin leaving more FY ice there as a replacement?

Any move toward the types of synoptics that brought the scale of Fram losses in the 80's could leave us a very impoverished basin by spring whilst keeping extent/area values high
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Frivolousz21

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Re: The 2014 Melting Season
« Reply #3170 on: August 15, 2014, 01:18:25 PM »
 Last night after seeing the 00z GFS I wrote this on americanwx:

Quote
I still contend in the day 6-10 range the models are flattening the ridge to much and some runs have what I call an erroneous SLP next to the larger vortex over the Russian coast.

I expect it to be one elongated vortex with a stronger NA ridge.

This is pretty much how I saw it in my head with what the 06Z GFS shows.  Talk about possibly going out with a bang.  If this persists well into September I could see possibly down to 4.5 mil km2 on Jaxa and definitely under 5.0 mil km2 on the NSIDC monthly for Sept.

Minus the elongated vortex but the erroneous SLP vanished and the ridging/surface pressure looks like the Euro ensemble mean looks.  I bet we would have to go back to 2012 to see such a persistent dipole in the JJA months.  Luckily for the ice this is happening to late to do any major damage in terms of melting except the outer rim.

Now we will see how far the Pacific side ice can be compacted/bottom/side melted the next two weeks before bottom melt slows pretty abruptly as we go into September.  However if we maintain this dipole into September bottom melt outside of 80N can persist and be impactful with the right wind scheme with ice 0.5M or thinner along the pack edges.


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Lord M Vader

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Re: The 2014 Melting Season
« Reply #3171 on: August 15, 2014, 04:55:18 PM »
We are gradually backtracking to more AO/NAO-negative regims which will be really bad for the ice.

As Friv states this dipole is coming too late to make any serious damage to the ice. Thicker ice that have been acting as a "wall" around Svalbard will be pushed further south and be replaced by thinner ice. The ice that's succeeds to moce through Fram strait and Victoria strait should get really big troubles next month until refreezing starts.

Adding to that is warm water from Laptev to be pushed to the ice edge.

Some important questions for the current future:

1. How much soot from the many fires in siberia and Canada have reached the Arctic and been deposited on the snow cover? This doesn't have any impact for this season but maybe for the next one.

2. HYCOMs estimate of the ice thickness is apparently too big but are there other links to see the ice thickness?

3. Will we trend toward a more negative AO/NAO-regime the next two years? Was the positive anomaly in 2013 and the beginning just a temporary period?

4. Will 2015 have a more wavier jet stream? IMO both 2013 and 2014 (especially 2013) have lacked a really wavy jet.

5. Will El Niño make its appearance this year?

6. How much precipitation will the Arctic get this autumn and winter? A lot of precipitation at wrong time may have great impact for the next melt season.

The worst case scenario should be if the Arctic gets a lot of snow early in the season with some soot from the fires to single down at the snow cover followed by a negative AO through the rest of the winter. This should make the ice growth slow and allow for a quick onset next spring if a more persistent negative AO-regime evolves then and succeeds to establish during the summer. If an El Niño also developes, either 2015 or 2016 should smash 2012 really big!

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Re: The 2014 Melting Season
« Reply #3172 on: August 15, 2014, 05:44:35 PM »
Even with current sea ice coverage loss, I still think the jet stream should stay rather messed up. It was the recent Coumou paper which observed an increase in quasi-resonant waves/extreme weather patterns since 2000 corresponding to rapid warming in the Arctic. Ever since 2002, there have been frequent, extensive losses of ice and more exposed ocean around the Laptev and ESS regions, allowing heat to accumulate throughout summer and be re-released to the atmosphere during autumn. Hard to say what El Niño will do, but winter 2014-2015 could bring more rain than snow to much of North America if it gets to moderate strength, which is bad for albedo.

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Re: The 2014 Melting Season
« Reply #3173 on: August 16, 2014, 06:36:50 AM »
Jaxa dropped -69K.  Still -90K above 2013.  However 2013 slows down tremendously in two days.

To be tied with 2013 on September 1st 2014 must average -46.7K or more per day.

To be tied with 2010 on September 1st 2014 must average -41.4K or more per day.

To be tied with 2009 on September 1st 2014 must average -33.6K or more per day.

To be tied with 2008 on September 1st 2014 must average -62.8K or more per day.

The GFS keeps the dipole going thru the next 8-10 days.

This will keep Extent dropping steadily. But it will also keep the flow of the thickest ice into the Atlantic going and probably get the Fram going.  Ice mobility is reaching it's peak. 

With the long fetch over the same ice for days on end + the fact that it's already well in motion the entire ice pack will be moving quite vigorously at the same time from the Pacific side to the Atlantic side.




« Last Edit: August 16, 2014, 07:23:39 AM by Frivolousz21 »
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Frivolousz21

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Re: The 2014 Melting Season
« Reply #3174 on: August 16, 2014, 07:57:38 AM »
Enhanced visible to see ice structure better

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Re: The 2014 Melting Season
« Reply #3175 on: August 16, 2014, 10:06:30 AM »
LMV,

Re Thickness  - There is only model data during the summer. IceBridge is available for winter.
http://nsidc.org/icebridge/portal/
But it only covers the Canadian side of the Arctic.

Wavy Jet? Do you mean over the US and the Atlantic? I think this was a result of anomalous Greenland ridging, the ridging was absent last year, this year (Jun/Jul avg) it is of a similar level to the lowest of the 2007 to 2012 years (2010). But in the Atlantic there has been dominant high pressure and the wider Greenland centred pattern of 2007 to 2012 has failed.

My WAG is that this is due to the PNA pattern, it seems to have disrupted the 2007 to 2012 summer pattern. The Jet during summers 2007 to 2012 seems (on average) to have entered the US in the northern Rockies and been steered into a large loop in the East Coast US/Atlantic by Greenland. It is possible that the PNA centre of action in the north Pacific has affected this  steering. It is  equally possible that it is the Jet that is enhancing ridging over Greenland, not the adjacent pattern over the Arctic Ocean. So, whereas I had thought the pattern over the Arctic had led to the Greenland ridging I may need to change my view. It may be that the effect of sea ice is at the entry of the dipole flow into the Arctic Ocean (Bering region) and that it is this that is affecting the Jet as it enters the US, then enhancing the Greenland ridge and affecting European summer rainfall.

However the PNA is not causing all this. PNA has been largely positive since 1998, the Greenland centred summer pattern has been since 2007, until 2012.

The atmosphere is very complex and I am not sufficiently qualified to do more than guess.

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Re: The 2014 Melting Season
« Reply #3176 on: August 16, 2014, 04:29:23 PM »
Re Thickness  - There is only model data during the summer. IceBridge is available for winter.

But it only covers the Canadian side of the Arctic.

Don't forget Wipneus' sterling work with SMOS:

http://GreatWhiteCon.info/resources/arctic-sea-ice-graphs/#SMOS
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Re: The 2014 Melting Season
« Reply #3177 on: August 16, 2014, 05:45:04 PM »
The stall in CT area is almost getting interesting. While we're seeing solid extent declines by most measures, and decent area declines at least by Wippy's measure, CT is basically stuck. I would put it down to compaction, but we're seeing declines in other area measures. Any thoughts? Is it a resolution effect?

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Re: The 2014 Melting Season
« Reply #3178 on: August 16, 2014, 06:31:48 PM »
The stall in CT area is almost getting interesting.

This is understated as far as I am concerned. It is very interesting and I would love to have someone offer an explanation.

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Re: The 2014 Melting Season
« Reply #3179 on: August 16, 2014, 07:02:46 PM »
Probably melt ponds freezing over.  If I recall correctly, CT area uses an algorithm which is more susceptible to counting melt ponds as water, which is why it shows this effect more strongly than other sources.  Could also be new snowfall over the ice.

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Re: The 2014 Melting Season
« Reply #3180 on: August 16, 2014, 07:43:18 PM »
Probably melt ponds freezing over.  If I recall correctly, CT area uses an algorithm which is more susceptible to counting melt ponds as water, which is why it shows this effect more strongly than other sources.  Could also be new snowfall over the ice.

I was at one point willing to accept this as the full explanation, but am becoming increasing skeptical of it as either sufficient or complete.  Do we have some examination of it which is more than anecdotal? 
« Last Edit: August 17, 2014, 12:00:08 AM by jdallen »
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Re: The 2014 Melting Season
« Reply #3181 on: August 16, 2014, 10:33:33 PM »
Over the last couple of weeks, both Navy thickness models show the thick MYI just north of the CAA breaking free of land and moving west. First the western section breaks off around Aug 1, then the entire thing breaks off around Aug 6.

1. Is this real?
2. Is it normal?
3. Is it bad (for long-term ice preservation), good, or neither?


This kind of ice movement is normal and happens in any season. You can see the normal counterclockwise movement of the Beaufort Gyre in the ice drift maps posted by Frivolousz21 above.

For the last big blocks (or blobs?) of the thickest ice to break loose and drift away to the south is another matter. Maybe someone else can answer. The thick ice that moved to the Beaufort Sea and beyond since last summer melted away this summer.

Greatdying:  Does the yearly animation help answer your questions? http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim365d.gif

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Re: The 2014 Melting Season
« Reply #3182 on: August 17, 2014, 12:15:29 AM »
Cesium (& Rick),

I'm aware of the general direction of ice movement. My question is whether it's normal for the thickest ice to completely detach from the CAA and become mobile, how far it might end up moving, and whether this may be the beginning of the end for the last of the thick ice.

The yearly animation does help a bit (thank you): it show that this hasn't happened previously this melt season until the last couple weeks. But of course that isn't so surprising. More telling would be animations from previous years (which I have been unable to find).
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Re: The 2014 Melting Season
« Reply #3183 on: August 17, 2014, 01:28:53 AM »
Well I guess the multi year ice has a deeper draught than thinner first year ice.  So it will be more susceptible to currents flowing around it than the FYI, while it will have the same drag force acting on it from wind across its surface.

The initiation of the westward movement of the MYI towards the Beaufort seemed to be an abrupt and clear movement away from the CAA coast which seemed to unhook the MYI from its grounding.  Something shoved it all north and kept it away from the coast, aand the gyre is sending it west from whence it will never return.

Have northbound currents in the CAA increased to do this?

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Re: The 2014 Melting Season
« Reply #3184 on: August 17, 2014, 06:07:55 AM »
It has most certainly not been snowing over the arctic basin.  Not even close.





But melt ponds freezing over is more likely. 





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Re: The 2014 Melting Season
« Reply #3185 on: August 17, 2014, 06:50:31 AM »
Perhaps this isn't news,  but...

Quote
The authors compared data from NASA airborne surveys, collected between 2009 and 2013, with U.S. Army Corps of Engineers buoys frozen into the sea ice, and earlier data from Soviet drifting ice stations in 1937 and from 1954 through 1991. Results showed that snowpack has thinned from 14 inches to 9 inches (35 cm to 22 cm) in the western Arctic, and from 13 inches to 6 inches (33 cm to 14.5 cm) in the Beaufort and Chukchi seas, west and north of Alaska.
That's a decline in the western Arctic of about a third, and snowpack in the Beaufort and Chukchi seas less than half as thick in spring in recent years compared to the average Soviet-era records for that time of year.
....
The authors speculate the reason for the thinner snow, especially in the Beaufort and Chukchi seas, may be that the surface freeze-up is happening later in the fall so the year's heaviest snowfalls, in September and October, mostly fall into the open ocean.
What thinner snow will mean for the ice is not certain. Deeper snow actually shields ice from cold air, so a thinner blanket may allow the ice to grow thicker during the winter. On the other hand, thinner snow cover may allow the ice to melt earlier in the springtime.


 http://phys.org/news/2014-08-thinned-arctic-sea-ice.html#jCp

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Re: The 2014 Melting Season
« Reply #3186 on: August 17, 2014, 07:26:58 AM »

The 00z GFS keeps the compaction regime going for the next 8 days at least.

I think by the end of the 7-8 day period jaxa will drop below 2013 and 2010.  But keeping pace with 2008 will probably be to much.

The main thing going for 2014 to continue with relatively large drops is the region under the gun is the lower latitude ice.







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Re: The 2014 Melting Season
« Reply #3187 on: August 17, 2014, 07:56:54 AM »
Cesium (& Rick),

I'm aware of the general direction of ice movement. My question is whether it's normal for the thickest ice to completely detach from the CAA and become mobile, how far it might end up moving, and whether this may be the beginning of the end for the last of the thick ice.

The yearly animation does help a bit (thank you): it show that this hasn't happened previously this melt season until the last couple weeks. But of course that isn't so surprising. More telling would be animations from previous years (which I have been unable to find).

by the by, the link I posted was at one point a 365 day animation, but looks like it got truncated to about a 5 month animation when it was updated to the current date.

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Re: The 2014 Melting Season
« Reply #3188 on: August 17, 2014, 12:34:16 PM »
Probably melt ponds freezing over.  If I recall correctly, CT area uses an algorithm which is more susceptible to counting melt ponds as water, which is why it shows this effect more strongly than other sources.  Could also be new snowfall over the ice.

I was at one point willing to accept this as the full explanation, but am becoming increasing skeptical of it as either sufficient or complete.  Do we have some examination of it which is more than anecdotal?

No we don't, it remains a guess.

A major reason is the June 'cliff' in years like 2012. It would be quite easy to do some code to estimate changes in the ice edge and changes of area within the pack to see where changes (and stalls) are actually coming from using NSIDC gridded concentration. I think CT Area uses that gridded data, but Wipneus would be the expert on that matter.

It's on my list of jobs, but most of this year my day job has been pushing out this hobby. Hopefully that will change. If I get the chance this Autumn I'll look at it, I've got the code to get gridded NSIDC into arrays, I've just not had the time to do anything with it.

Mmmm, actually...

Just checked Wipneus's area data. The Arctic Ocean shows a stall in area loss in that data, from 5 to 15 August average is 4.53M km^2, stdev = 0.035M km^2, Slope is -0.004M km^2/day, slope for the preceding period of same length is -0.0577M km^2/day. So that is a stall.  ;)

Slopes for stated periods (M km^2 / day) and regions
5 to 15 Aug / 25 Jul to 4 Aug
Beaufort. 0.001 / -0.002
Chukchi -0.006 / -0.007
ESS -0.003 / -0.027
Laptev -0.001 / -0.004
Kara -0.004 / -0.007
Barents 0.001 / 0.001
Central 0.009 / -0.009
CAA 0.000 / -0.003
Greenland -0.001 / 0.000
Arctic Ocean -0.005 / -0.058

The sums of each period make up the total for the Arctic Ocean.

From 25 Jul to 4 Aug all regions lose area apart from Greenland and Barents. Then from 5 to 15 Aug:

Beaufort Barents Central gain area, Central is the largest and this year plays little role in the ice edge, so it suggests there may be a role for ponds freezing there (?). Barents was gaining area before the stall, it bottomed out in late July.

Chukchi is as near as damn it the same during and before the stall. But the ESS shows a clear reduction of loss rate, 1/10 of the loss rate before the stall period. Laptev and Kara (also CAA) have reduced rates of loss.

Taking the above figures, calculating the difference between loss rates for all regions and then scaling as a percentage of the total loss rate difference for the Arctic Ocean gives the following percentage difference in loss rates.

Beaufort.   6%
Chukchi   2%
ESS   45%
Laptev   6%
Kara   6%
Barents   0%
Central   34%
CAA   6%
Greenland   -2%

So I'd say that the two biggest contributors to 'the stall' are the ESS, and the Central Arctic Region. Together they explain nearly 80% of the 'stall'.

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Re: The 2014 Melting Season
« Reply #3189 on: August 17, 2014, 12:36:40 PM »
Re Thickness  - There is only model data during the summer. IceBridge is available for winter.

But it only covers the Canadian side of the Arctic.

Don't forget Wipneus' sterling work with SMOS:

I did say 'during the summer'....

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Re: The 2014 Melting Season
« Reply #3190 on: August 17, 2014, 04:35:42 PM »
I’ve only read the past 9 days of this thread, but I’m loving it! I think it proves that the more you know about a given subject, the more you appreciate and understand the day–to–day changes. For instance, I was waiting patiently for Svalbard and Josef’s Land to go ice–free, yet now I understand that these straits are used for emptying CAB ice during the ADA dipole anomaly. It’s fantastic to see how this thread adjusts to the factors currently working on the ice, as a novice can then get a day–to–day feel of what and how many they are, and also how qualitatively different each melting season actually is from the previous ones.

Hopefully with a steep learning curve and some math & graph work I can contribute to this thread and future freeze/melt threads. But for now I just want to thank everyone for the splendid crash–course.
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Re: The 2014 Melting Season
« Reply #3191 on: August 17, 2014, 06:13:58 PM »
Thanks, Chris, for the great analysis. Given your results, I can understand that the CAB "stall" may be largely due to melt ponds freezing. The ESS is a bit harder to understand. Given the weather of the past two weeks, it would be difficult to put down to any sort of freezing. Given the rapid retreat of the ice edge and the generally bad state of the ice, it's questionable to put down to compaction, too. But I note that the ESS had the greatest rate of loss of any region prior to the last two weeks, so maybe we're just seeing that area loss (which I now recall was mostly in situ melting before Friv's ridge came to town) slowing down due to much of the ESS ice being gone. I've attached the CA plot for the region. It looks to me like the first week of Aug. saw rapid loss, then almost completely stalled when area got to about 30% of its peak. It looks like losses may be picking up again, but it's too early to tell.

Looking at all the regional plots, it's the ESS, CAA, and CAB that are the big differences with other recent years (with a bit of Beaufort). Given their low latitudes, there's still time for loss in the ESS and CAA, so we might still see some drops in area. It will depend on how fast the high latitudes freeze.

Thanks again, Chris. That was a big help.

ChrisReynolds

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Re: The 2014 Melting Season
« Reply #3192 on: August 17, 2014, 07:15:50 PM »
Bruce,

I suspect the ESS may be in the process of starting to bottom out, we'll see what's happened by the end of the month.

Viddalo,

I look forward to your contribution. If you need data just ask and someone will give links.

Some useful data (for the lurkers too).
NSIDC Extent.
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/north/daily/data
CT Area.
http://arctic.atmos.uiuc.edu/cryosphere/timeseries.anom.1979-2008
Wipneus's area & Extent data.
https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/data
You'll probably need nsidc_nt_final_detail.txt.gz and nsidc_nt_nrt_detail.txt
My calculation of regional volume from PIOMAS gridded data.
http://dosbat.blogspot.co.uk/2013/12/regional-piomas-volume-data.html

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Re: The 2014 Melting Season
« Reply #3193 on: August 17, 2014, 11:55:03 PM »
Thanks, Chris, for the great analysis. Given your results, I can understand that the CAB "stall" may be largely due to melt ponds freezing. The ESS is a bit harder to understand. Given the weather of the past two weeks, it would be difficult to put down to any sort of freezing. Given the rapid retreat of the ice edge and the generally bad state of the ice, it's questionable to put down to compaction, too. But I note that the ESS had the greatest rate of loss of any region prior to the last two weeks, so maybe we're just seeing that area loss (which I now recall was mostly in situ melting before Friv's ridge came to town) slowing down due to much of the ESS ice being gone. I've attached the CA plot for the region. It looks to me like the first week of Aug. saw rapid loss, then almost completely stalled when area got to about 30% of its peak. It looks like losses may be picking up again, but it's too early to tell.

Looking at all the regional plots, it's the ESS, CAA, and CAB that are the big differences with other recent years (with a bit of Beaufort). Given their low latitudes, there's still time for loss in the ESS and CAA, so we might still see some drops in area. It will depend on how fast the high latitudes freeze.

Thanks again, Chris. That was a big help.

The surface there has been freezing over.  But in spite of the compaction the ice is still melting strongly from the bottom which could go on for another 7-10 days with favorable winds.  You can see the ice transform on modis and large

The winds are blowing over the continental shelf where things are really shallow.  Mixing and wave action would be pretty easy to come by.  The water under the ice is warmer.  Disruption of this and mixing to the surface would aid in bottom melt.

Consider how much compression the ice has taken as well as the surface temps cooling enough to freeze the top layer of the ice in a hard freeze at night and yet you see areas where ice has melted out enough for large pools of open water to continue to show up even with ice moving tremendously the last two weeks.  Remember when this started the ESS appeared to be "solid" from the same modis vantage.

And it's still breaking up.

The source of heat coming from the Pacific ocean in the 50-200M layer is unlimited.  Consider how shallow the continental ridge is. 

Then consider how above normal the North Pacific is.  That high salinity warm water dives under the cold fresh water surface layer that supports the ice.  But the water depth is only 50-100M or even less in some cases over the shelf until you further North in the 76-77N range. 

This makes it much easier to be tapped as a source of bottom melt heat.














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Re: The 2014 Melting Season
« Reply #3194 on: August 18, 2014, 12:52:14 AM »
The source of heat coming from the Pacific ocean in the 50-200M layer is unlimited.  Consider how shallow the continental ridge is. 

Indeed, the Chukchi bite two does seems to be above some shallow seafloor features, namely the Chukchi Plateau. Looking more closely, the east side of the plateau appears to drop and rise again, a sunken area ringed by a ridge. I wonder if this topography might induce some turbulence in the Pacific currents?
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Re: The 2014 Melting Season
« Reply #3195 on: August 18, 2014, 03:52:40 AM »
Well ITP77 is over deep water in the far Western CAB where the sub-surface is much more stable then in the 50-100M shelf.

But you can see the power of the sub-surface warm current.  The last update for the OHC profile was August 5th.  But that is an incredible amount of heat not because it's so warm itseld but because of how much volume it takes up.





IT{ 79 in the Beaufort still shows some decent sub surface warmth in the fresh water layer with the winds expected to blow from a Southerly/Easterly direction most of the next 7 days at least we should see bottom melt keep pushing there at least in the 74-76N range.




« Last Edit: August 18, 2014, 04:19:48 AM by Frivolousz21 »
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Re: The 2014 Melting Season
« Reply #3196 on: August 18, 2014, 05:12:28 AM »
Yeah, from those plots, it seems that the top 50 m at both buoys has heated up in the last ~2 weeks.
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Re: The 2014 Melting Season
« Reply #3197 on: August 18, 2014, 05:18:24 AM »

Google says 20 knots is about 10m/s, so the ice would move about 0.2m/s.  4 days is around 400,000 seconds, so the ice moves 80 km.  So 36000km^2 of ice area would blow out through the Fram.  Looks like 36K is about one September day of ice loss...
cesium62,
You  would have to include the underlying East  Greenland current which can be up to 0.4 m/s but  averages about 0.1 m/s over the year,  to  get  a better estimate. Your 36,000 km^2 estimate could easily  be doubled.  However its  extent  not  area that moves through the strait so the loss of sea ice area would be significantly  lower than that.

Also the North Atlantic Current moves north around the west  of Svalbard, which  tends to  melt out the ice before it moves into the Fram Strait. 
« Last Edit: August 18, 2014, 05:56:20 AM by DavidR »
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Re: The 2014 Melting Season
« Reply #3198 on: August 18, 2014, 07:35:43 AM »
The 00z GFS pushes a last surge of relatively warm air into the Pacific side.  I am not sure if area will respond much at this point.  I still think it gets down to around 3.6-3.75 km2 but that is in part because I think extent will get down to 4.6 mil km2 on jaxa.

That is a pretty solid area with a mean above 0C.

The GFS shows warm air advection over spreading the Pacific side in a couple days.



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Re: The 2014 Melting Season
« Reply #3199 on: August 18, 2014, 02:43:39 PM »
...  The ESS is a bit harder to understand. Given the weather of the past two weeks, it would be difficult to put down to any sort of freezing. Given the rapid retreat of the ice edge and the generally bad state of the ice, it's questionable to put down to compaction, too. But I note that the ESS had the greatest rate of loss of any region prior to the last two weeks...
My reading of Wipneus' graphics is that much of the melt from the recent warm winds remained as relatively fresh water near the surface - especially in the interior of the pack.  Then some of it refroze when temperatures dropped, offsetting continued melt around the edges.

Bruce,
I suspect the ESS may be in the process of starting to bottom out, we'll see what's happened by the end of the month.
Starting to, yes, but look for a few sizable drops (22nd - 24th August) from the combination of melting and ice edge movement with warm winds off the coast.