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dnem

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Re: The 2017 melting season
« Reply #950 on: April 26, 2017, 01:36:41 PM »
The changes we are observing in the arctic are the result of continual and growing perturbation from a roughly equilibrium state, caused by building AGW.  This perturbation has caused measurable and growing changes in many monitoring variables (extent, area, volume) over the past few decades.  I think Bill's analysis relies on the assumption that the rate of change of the perturbation over time going forward will remain constant.  I am not convinced this is a valid assumption.  I believe the rate of change of the cumulative forcings may well change at an increasing rate in the future.

Past performance is not a reliable predictor of future performance.

dj

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Re: The 2017 melting season
« Reply #951 on: April 26, 2017, 01:37:13 PM »
Question:  I have used the PIOMAS volume and NSIDC area monthly averages to calculate thickness.  Has anyone noted the shift in timing of when maximal Arcic ice thickness occurs?  Or is this in some way an artifact that results from development of melt ponds early in the season?
I ask because there appears to be a dramatic shift from Sept/August to May/June.
I attribute this to a shift in the ratio of FYI to MYI with the first year ice rapidly melting off earlier.

First figure: Arctic Ice Thickness (m) reported as a stock with open, close, high, low.  Black = loss, White = Gain.
Second figure: Month of maximal thickness of Arctic Ice (from Sept to Aug).

« Last Edit: April 26, 2017, 03:39:29 PM by dj »

Buddy

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Re: The 2017 melting season
« Reply #952 on: April 26, 2017, 02:27:39 PM »
Has anyone noted the shift in timing of when maximal Arctic ice thickness occurs?  Or is this in some way an artifact that results from development of melt ponds early in the season?
I ask because there appears to be a dramatic shift from Sept/August to May/June.
I attribute this to a shift in the ratio of FYI to MYI with the first year ice rapidly melting off earlier.

SWEET....great chart.....and nice "find".  As a non-scientific person.....I will be VERY curious to hear what the physics folks have to say.  That chart really does "gobsmack" me.  Clearly there is a "physical reason" for it.....and I can't wait to find out what it is.  I LOVE IT when people start asking questions....because they eventually lead to answers.

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VeliAlbertKallio

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Re: The 2017 melting season
« Reply #953 on: April 26, 2017, 02:42:38 PM »
Although PIOMAS volume crossed to the lowest-ever category in mid-November 4 1/2 months ago, the substantial drops beneath any other have occurred in February and March. If May or June further pushes this gap we are really out, if the weathers became very cloudy, the gap would remain but close a bit and for those expecting an-ice-spectacular, this undoubtedly would be a disappointment. But the Arctic does have a certain degree of variability and unpredictability and one cannot be absolutely sure how much the elephant's trunk bends down. My gut feeling is that April and May would be very low just like February and March have been.





I think this is a year in which smart money does not bet against the first summer Arctic sea ice melt out.

I think there's a very good chance that once ice gets below 3,000 km3 we're likely to see very accelerated melting of ice which is not jammed against land masses.  In an ocean which is largely ice free the remaining pieces of ice are likely to move around rapidly, leaving the pockets of protective cold water that surrounds them.  And we'll see accelerated flushing out of the Central Basin into the killing fields.


Those are good points and probably right.  I have said similar things but expect the impact to become much more rapid once we drop below 1,000 km3.  I am currently projecting a minimum of 1,750 km3 +/- 1,500 km3.   From here on out it all depends on the weather and I am starting to see some projections of significant WV intrusion on the Pacific Side that is reminiscent of the early 2013 season.  We will see if it holds up or not.
« Last Edit: April 26, 2017, 02:51:20 PM by VeliAlbertKallio »

jai mitchell

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Re: The 2017 melting season
« Reply #954 on: April 26, 2017, 02:43:00 PM »
the average thickness graph is interesting and I have wondered for many years what it is actually telling us since it is really a function of two dynamic metrics, sea ice extent and volume.  I believe that your interpretation is correct that the loss of multi-year ice has skewed the distribution curve after 2007 and especially after 2012.  However, it should be noted that after a rapid collapse of sea ice extent, the average thickness would go up! Which on its face makes it kind of pointless to track, though there may be some interesting useful data there that I am not seeing.
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crandles

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Re: The 2017 melting season
« Reply #955 on: April 26, 2017, 03:12:16 PM »
Question:  I have used the PIOMAS volume and NSIDC area monthly averages to calculate thickness.  Has anyone noted the shift in timing of when maximal Arcic ice thickness occurs?  Or is this in some way an artifact that results from development of melt ponds early in the season?
I ask because there appears to be a dramatic shift from Sept/August to May/June.
I attribute this to a shift in the ratio of FYI to MYI with the first year ice rapidly melting off earlier.

First figure: Arctic Ice Thickness (m) reported as a stock with open, close, high, low.  Black = loss, White = Gain.
Second figure: Month of maximal thickness of Arctic Ice.


Monthly figures are not good averages of the whole month often equate to value around 21/22nd of month. Better to do it with daily values. Using NSIDC extent I get

Max thickness Year day no. PIOMAS volume
2.318364396   1988 154  28.859
2.289274106   1989 138  29.582
2.288970221   1990 264  13.759
2.261284793   1991 162  27.703
2.25912203   1992 157  28.047
2.261604054   1993 152  28.114
2.254532152   1994 160  27.733
2.160511824   1995 145  26.678
2.118136706   1996 152  26.464
2.257689178   1997 152  27.747
2.197949979   1998 159  26.804
2.151437466   1999 174  23.498
2.09246973   2000 157  25.231
2.105114887   2001 167  23.912
2.110257681   2002 154  25.551
2.044730392   2003 131  26.696
2.045465942   2004 152  24.474
2.006957997   2005 154  23.652
1.95871678   2006 155  22.774
1.826859136   2007 146  22.527
1.894886364   2008 140  24.012
1.842512479   2009 153  22.147
1.743161214   2010 138  22.112
1.686625805   2011 134  21.464
1.695425125   2012 121  23.051
1.694907372   2013 138  21.866
1.753696131   2014 133  22.300
1.859662816   2015 128  23.826
1.795368353   2016 128  22.250

One year 1990 seems to have day of max pushed into Sept day 264. There is a local peak at day 155. Apart from this strange 1990 year that latest day is 174 23rd June.

Yes there is a noticeable trend towards earlier dates but it looks to me to be more like day 160 back to day 130.  Approx 30 days over 28 year period. That seems more in accordance with:



I started in 1988 due to every other day gaps prior to this in NSIDC extent.

Using area will probably make the September peak more prominent and hence your different results but it looks to be confusing 2 different peaks in the pattern like 1990 is messed up using extent.

dj

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Re: The 2017 melting season
« Reply #956 on: April 26, 2017, 03:34:19 PM »
Question:  I have used the PIOMAS volume and NSIDC area monthly averages to calculate thickness.  Has anyone noted the shift in timing of when maximal Arcic ice thickness occurs?  Or is this in some way an artifact that results from development of melt ponds early in the season?
I ask because there appears to be a dramatic shift from Sept/August to May/June.
I attribute this to a shift in the ratio of FYI to MYI with the first year ice rapidly melting off earlier.

First figure: Arctic Ice Thickness (m) reported as a stock with open, close, high, low.  Black = loss, White = Gain.
Second figure: Month of maximal thickness of Arctic Ice.


Monthly figures are not good averages of the whole month often equate to value around 21/22nd of month. Better to do it with daily values. Using NSIDC extent I get

Max thickness Year day no. PIOMAS volume
2.318364396   1988 154  28.859
2.289274106   1989 138  29.582
2.288970221   1990 264  13.759
2.261284793   1991 162  27.703
2.25912203   1992 157  28.047
2.261604054   1993 152  28.114
2.254532152   1994 160  27.733
2.160511824   1995 145  26.678
2.118136706   1996 152  26.464
2.257689178   1997 152  27.747
2.197949979   1998 159  26.804
2.151437466   1999 174  23.498
2.09246973   2000 157  25.231
2.105114887   2001 167  23.912
2.110257681   2002 154  25.551
2.044730392   2003 131  26.696
2.045465942   2004 152  24.474
2.006957997   2005 154  23.652
1.95871678   2006 155  22.774
1.826859136   2007 146  22.527
1.894886364   2008 140  24.012
1.842512479   2009 153  22.147
1.743161214   2010 138  22.112
1.686625805   2011 134  21.464
1.695425125   2012 121  23.051
1.694907372   2013 138  21.866
1.753696131   2014 133  22.300
1.859662816   2015 128  23.826
1.795368353   2016 128  22.250

One year 1990 seems to have day of max pushed into Sept day 264. There is a local peak at day 155. Apart from this strange 1990 year that latest day is 174 23rd June.

Yes there is a noticeable trend towards earlier dates but it looks to me to be more like day 160 back to day 130.  Approx 30 days over 28 year period. That seems more in accordance with:



I started in 1988 due to every other day gaps prior to this in NSIDC extent.

Using area will probably make the September peak more prominent and hence your different results but it looks to be confusing 2 different peaks in the pattern like 1990 is messed up using extent.


Extent definitely would give a difference in dates, and due to how PIOMAS calculates thickness extent would not necessarily be appropriate
The average thickness is calculated for the PIOMAS domain by only including locations where ice is thicker than .15 m.

This may introduce some bias in PIOMAS' estimates?  Especially as the ice continues to get thinner with first year ice?
I guess one question should be, why is there such a distinct difference between PIOMAS's graph and the numbers reported.  I understand that differences in how things are calculated (cutoffs) would be in play.  Where does PIOMAS derive is numbers for extent/area?

dj

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Re: The 2017 melting season
« Reply #957 on: April 26, 2017, 03:42:49 PM »
I should point out, as confusing as it is - that for the second graph I used a single calendar year (Sept - Aug) instead of what is shown in the first graph (Sept to Sept), as I wanted to see if and when a shift occurred.
The first graph I made so that the students I teach could better "connect the dots" in that the start of one freeze/melt season was the finish of the prior freeze/melt season.

If that seems confusing - apologies.
« Last Edit: April 26, 2017, 04:01:14 PM by dj »

crandles

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Re: The 2017 melting season
« Reply #958 on: April 26, 2017, 03:50:59 PM »
I guess one question should be, why is there such a distinct difference between PIOMAS's graph and the numbers reported.  I understand that differences in how things are calculated (cutoffs) would be in play.  Where does PIOMAS derive is numbers for extent/area?

I thought they came out pretty similar really:
For 2016 I have 1.8m, reading off PIOMAS graph I get around 1.78m
For 2004 I have 2.05m, reading off PIOMAS graph I get around 2.14m

given "The average thickness is calculated for the PIOMAS domain by only including locations where ice is thicker than .15 m.", yes it is surprising they are so close.



dj

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Re: The 2017 melting season
« Reply #959 on: April 26, 2017, 03:56:41 PM »
I guess one question should be, why is there such a distinct difference between PIOMAS's graph and the numbers reported.  I understand that differences in how things are calculated (cutoffs) would be in play.  Where does PIOMAS derive is numbers for extent/area?

I thought they came out pretty similar really:
For 2016 I have 1.8m, reading off PIOMAS graph I get around 1.78m
For 2004 I have 2.05m, reading off PIOMAS graph I get around 2.14m

given "The average thickness is calculated for the PIOMAS domain by only including locations where ice is thicker than .15 m.", yes it is surprising they are so close.

Could it be that I am following the freeze/melt season, and not the calendar year?
Plotting from Sept 2014 to Aug 2015 (for the second graph).
And yes indeed, I do think that is remarkably close.

« Last Edit: April 26, 2017, 04:02:09 PM by dj »

crandles

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Re: The 2017 melting season
« Reply #960 on: April 26, 2017, 04:08:59 PM »

Could it be that I am following the melt season, and not the calendar year?
Plotting from Sept 2014 to Aug 2015?

Not at all sure I follow this question. Surely Jan 1 Piomas volume should be divided by Jan 1's area/extent and so on. I don't see why where the season ends matters.

Doing monthly is too coarse a resolution if you can get 2 peaks getting confused with each other. Near max extent and area are similar. At September area can be a lot less than extent so using area  gives a higher second peak and more chance of confusing the different peaks.

dj

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Re: The 2017 melting season
« Reply #961 on: April 26, 2017, 04:12:40 PM »
the average thickness graph is interesting and I have wondered for many years what it is actually telling us since it is really a function of two dynamic metrics, sea ice extent and volume.  I believe that your interpretation is correct that the loss of multi-year ice has skewed the distribution curve after 2007 and especially after 2012.  However, it should be noted that after a rapid collapse of sea ice extent, the average thickness would go up! Which on its face makes it kind of pointless to track, though there may be some interesting useful data there that I am not seeing.

I guess what I am wondering is that - with the thinning of the ice - is there a point where the average thickness will cross a threshold and allow for a rapid collapse?  For a variety of reasons?

Extent - I am not a fan of.  I agree that for a period of time there will be years of ice formation in the winter, and then ice loss in the summer.  And the debate about whether or not the Arctic is considered ice free will pointlessly rage on.  Environmentally, that ice is not the same and the changes will be significant - although one could argue they already are.



dj

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Re: The 2017 melting season
« Reply #962 on: April 26, 2017, 04:18:22 PM »

Could it be that I am following the melt season, and not the calendar year?
Plotting from Sept 2014 to Aug 2015?

Not at all sure I follow this question. Surely Jan 1 Piomas volume should be divided by Jan 1's area/extent and so on. I don't see why where the season ends matters.

Doing monthly is too coarse a resolution if you can get 2 peaks getting confused with each other. Near max extent and area are similar. At September area can be a lot less than extent so using area  gives a higher second peak and more chance of confusing the different peaks.

Yes but your January 1st 2014 is being compared with September - December 2014.
My September - December 2014 is being compared with January-August 2015.

Still there is a discrepancy between what I show and what PIOMAS shows.  After careful reading of PIOMAS it may be that they also do not included all areas that contain Ice and calculate only the thickness of the area that they calculate volume.  So, that may be one difference, in that the areas between PIOMAS and NSIDC are different.

Maybe back to the drawing board for me.   ;)

crandles

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Re: The 2017 melting season
« Reply #963 on: April 26, 2017, 04:25:16 PM »

I guess what I am wondering is that - with the thinning of the ice - is there a point where the average thickness will cross a threshold and allow for a rapid collapse?  For a variety of reasons?

If you have one foot in an ice bucket and one foot in near boiling water, does it matter whether you average temperature around you is a little too high or too low for comfort?

If there isn't all that much average thickness ice, why would you expect the tipping point threshold (if there is one) to be particularly noticeable in the average thickness measure?

dj

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Re: The 2017 melting season
« Reply #964 on: April 26, 2017, 04:46:43 PM »

I guess what I am wondering is that - with the thinning of the ice - is there a point where the average thickness will cross a threshold and allow for a rapid collapse?  For a variety of reasons?

If you have one foot in an ice bucket and one foot in near boiling water, does it matter whether you average temperature around you is a little too high or too low for comfort?

If there isn't all that much average thickness ice, why would you expect the tipping point threshold (if there is one) to be particularly noticeable in the average thickness measure?

I agree with you there - the average temperature is not going to be all that important.  We talk in terms of volume and extent.  Extent, is the least important but the thickness/volume is.  Any tipping point will be due to the loss of thick MYI versus FYI.
I am using some of this in classes, and stressing to my students that using averages is the appropriate method to do so (along with the standard other facors - variation, STD etc.).

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Re: The 2017 melting season
« Reply #965 on: April 26, 2017, 06:56:26 PM »
Question:  I have used the PIOMAS volume and NSIDC area monthly averages to calculate thickness. 

Not advisable. Since NSIDC area monthly averages do not include the area of the pole hole, the values vary with the satellite of the date.

If you want to use area (and not extent), either use CT-area (stopped updating last year) or my daily values:
https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/data/nsidc_arc_nt_main.txt

Both make an assumption of the sea ice concentration within the pole hole from the measurements around it.

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Re: The 2017 melting season
« Reply #966 on: April 26, 2017, 07:30:32 PM »
The changes we are observing in the arctic are the result of continual and growing perturbation from a roughly equilibrium state, caused by building AGW.  This perturbation has caused measurable and growing changes in many monitoring variables (extent, area, volume) over the past few decades.  I think Bill's analysis relies on the assumption that the rate of change of the perturbation over time going forward will remain constant.  I am not convinced this is a valid assumption.  I believe the rate of change of the cumulative forcings may well change at an increasing rate in the future.

Past performance is not a reliable predictor of future performance.

This is a good point. I have another thought, but I'm not sure I can articulate it well. I'll give it a try: I also wonder if the attempt at statistical predicting like Bill's analysis is also missing the geographical consideration of the difference between the Arctic Basin and the peripheral seas, with respect to melting feedbacks. Since Hudson, Bering, Baffin, Okhotsk are all included in the volume and extent measurements.

Basically, in the beginning, the open water was really only in the peripheral seas by the end of the summer. Then the ice in the Arctic basin protected itself by preventing preventing solar energy gain (albedo), and by preventing wave action from disrupting the halocline/layering of water under the ice, and by keeping the relative humidity of the region low, allowing a lot of heat to escape once freezing season started up.

Now, (starting at some point around 2000?) every year there is a vast extent of open water within the Arctic basin, so the halocline/thermal layering of the ocean is disrupted, the water is gaining a lot more solar energy, the atmosphere is more humid, trapping even more energy. All this really affects the freezing season, reducing the volume of ice left to melt by the following melt season.

My question is, would we find out something interesting if did this kind of analysis by doing it on 2 different time periods: pre-Arctic basin open water, and post Arctic basin open water?

What happens to the trends if you have one for 1979-2000 and one for 2001-2016?


JimboOmega

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Re: The 2017 melting season
« Reply #967 on: April 26, 2017, 07:36:52 PM »

I agree with you there - the average temperature is not going to be all that important.  We talk in terms of volume and extent.  Extent, is the least important but the thickness/volume is.  Any tipping point will be due to the loss of thick MYI versus FYI.
I am using some of this in classes, and stressing to my students that using averages is the appropriate method to do so (along with the standard other facors - variation, STD etc.).

My feeling is that thickness matters less than everyone thinks it does, because it is the surface that interacts the most thermodynamically - it is the frozen area that reflects the light, that radiates heat off to space.  Especially right now, it seems things opening up (or not) has more to do with wind creating polynya than the thickness of the relevant ice and its resistance to melting.

Also the modeling behind thickness is a lot more imprecise - from what I've heard - than it is for extent (looking down from space and seeing ice is one thing, knowing how thick it is requires some assumptions).  There are a couple different volume numbers with very contrasting values (last I heard, anyway!)

Last year I heard a lot that a real cliff was coming, that the volume was so bad, we're so much worse off than 2012, etc. This year I'm not (automatically) buying it.

I think that the global climate implications of a the melting season are much more driven by extent than by volume, because that's what (via Albedo) controls how much extra heat would enter the system because of ice (or the lack thereof).

Last time I brought this up I asked people to make predictions based on the volume, IE, when would we see the results of the current volume in extent or other grossly visible things. I'd repeat that challenge again. 

Of course if you want to argue that weather trumps volume and thus you can't make any real predictions beyond a week or two, that's a valid assertion - but of course is contrary to the argument that average temperature matters less than volume.

It's also possible that each year we're getting a thinner pack and this is the year the thinness really does lead to a catastrophic extent/area drop. Do you think it is?  If it's not, how thin would it need to be for it to happen?

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Re: The 2017 melting season
« Reply #968 on: April 26, 2017, 08:09:36 PM »
"I guess what I am wondering is that - with the thinning of the ice - is there a point where the average thickness will cross a threshold and allow for a rapid collapse?  For a variety of reasons?"
When the ice no longer resists wave action, and is broken to the point where it flows like water, then I think we'll see a rapid collapse, from both melt and export. It looks possible this year, I suspect the ice is already melting from below, to a small degree, the thicker peices touching water thats just above 0C, yeilding a steady supply of easy to freeze fresh[er] water, rapidly repairing any cracks. Plus there's been plenty of snow around the arctic, some must have fallen on the ice raising it's freeboard and increasing the likelyhood of it moving through the water, and when the currents flow as recently by chukchi presenting little resistence. If it does reach that state the freshest top fraction will flow out with every tide and be pumped out under every high pressure system, replaced by inevitably warmer waters from the south.

Lord M Vader

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Re: The 2017 melting season
« Reply #969 on: April 26, 2017, 09:12:20 PM »
ECMWF 12z operational run is a hella scaring one!!! This is what the Arctic has to work with if the forecast run for Day 9-10 verifies!! Look at that monstrous high pressure dome covering virtually the whole Arctic!!!!

Would be a complete disaster, especially if it continues to linger for 1-2 weeks or so!! Courtesy: Tropical Tidbits/Lewi Cowan


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Re: The 2017 melting season
« Reply #970 on: April 26, 2017, 10:05:48 PM »
The Sensitivity of the Arctic Ocean Sea Ice Thickness and Its Dependence on the Surface Albedo Parameterization

ABSTRACT

In this study, the response of sea ice thickness to changes in the external forcing is investigated and particularly how this response depends on the surface albedo formulation by means of a one-dimensional coupled ocean–ice–atmosphere model. The main focus is on the thickness response to the atmospheric heat advection Fwall, solar radiation FSW, and amount of snow precipitation Sprec. Different albedo parameterization schemes [ECHAM5, CSIRO, and Community Climate System Model, version 3 (CCSM3)] representing albedos commonly used in global climate models are compared together with more simplified schemes. Using different albedo schemes with the same external forcing produces large differences in ice thickness. The ice thickness response is similar for all realistic albedo schemes with a nearly linear decrease with increasing Fwall in the perennial ice regime and with a steplike transition into seasonal ice when Fwall exceeds a certain threshold. This transition occurs at an annual-mean ice thickness of 1.7–2.0 m. Latitudinal differences in solar insolation generally leads to increasing ice thickness toward the North Pole. The snow response varies significantly depending on which albedo scheme is used. The ECHAM5 scheme yields thinner ice with Sprec, the CSIRO scheme gives ice thickness nearly independent of Sprec, and with the CCSM3 scheme the ice thickness decreases with Sprec. A general result is that the modeled ice cover is rather sensitive to positive perturbations of the external heat supply when it is close to the transition such that just a small increase of, for example, Fwall can force the ice cover into the seasonal regime.

http://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-12-00085.1

If I understand correctly, this is saying that there is an ice-thickness / forcing threshold beyond which a move to seasonal sea ice occurs in a step-wise fashion - due to the albedo feedback mechanism. 

As the temperature differential between the Arctic and the rest of the Northern Hemisphere reduces, it becomes easier for warm air masses to enter the Arctic from the south (the Jet Stream weakens and becomes wavier). So the value of Fwall may increase, and the ice will have to be thicker to survive the melt season.

This of course does not take into account any mechanical changes in the ice as it thins, nor the possible mixing of the water column where there are areas of open water/thin ice.
« Last Edit: April 26, 2017, 10:13:28 PM by rboyd »

rboyd

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Re: The 2017 melting season
« Reply #971 on: April 26, 2017, 10:22:31 PM »
Magnitude and pattern of Arctic warming governed by the seasonality of radiative forcing

Abstract

Observed and projected climate warming is strongest in the Arctic regions, peaking in autumn/winter. Attempts to explain this feature have focused primarily on identifying the associated climate feedbacks, particularly the ice-albedo and lapse-rate feedbacks. Here we use a state-of-the-art global climate model in idealized seasonal forcing simulations to show that Arctic warming (especially in winter) and sea ice decline are particularly sensitive to radiative forcing in spring, during which the energy is effectively ‘absorbed’ by the ocean (through sea ice melt and ocean warming, amplified by the ice-albedo feedback) and consequently released to the lower atmosphere in autumn and winter, mainly along the sea ice periphery. In contrast, winter radiative forcing causes a more uniform response centered over the Arctic Ocean. This finding suggests that intermodel differences in simulated Arctic (winter) warming can to a considerable degree be attributed to model uncertainties in Arctic radiative fluxes, which peak in summer.

2016 was the perfect case of this, where the albedo was highest in the Spring with the added energy being carried into the Fall season. We are running a bit behind of 2016 so far according to Nico Sun (details of his methodology on the Albedo Warming Potential Topic).

https://sites.google.com/site/cryospherecomputing/warming-potential/graphs

Neven

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Re: The 2017 melting season
« Reply #972 on: April 26, 2017, 10:37:10 PM »
Dear friends, can we please stay on-topic? There are various threads for discussing PIOMAS, volume, thickness, research.

Melting season.
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Re: The 2017 melting season
« Reply #973 on: April 26, 2017, 11:10:46 PM »
rboyd: I would love to see more discussion on that first paper you posted. Maybe start a new thread, "The Fast Transition"?
I am an energy reservoir seemingly intent on lowering entropy for self preservation.

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Re: The 2017 melting season
« Reply #974 on: April 27, 2017, 12:25:25 AM »
For the next five days, high pressure system coming back to the pacific side of Arctic, but ACNFS predicts very modest intensity of induced clockwise drift.
Pressure gradients not as intense as in the first half of April? We'll see how it goes.

dj

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Re: The 2017 melting season
« Reply #975 on: April 27, 2017, 01:22:21 AM »
Thank you for the comments and the further resources to explore.

And thank you Wipneus for identifying the weakness (incorrectness) of my comparison, and providing the corrected data. 

Neven, apologies for picking the incorrect place to post this.
« Last Edit: April 27, 2017, 03:20:52 AM by dj »

Meirion

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Re: The 2017 melting season
« Reply #976 on: April 27, 2017, 04:43:13 AM »
You know when the "arctic sea ice isn't really melting" crowd start saying "but why should we trust the sea-ice concentration map" - or whatever - and you want to say - "well I've just seen it". Well...

I just flew London to Los Angeles and the routing looked interesting. Sadly there was thick cloud over the Fram but it cleared over western Greenland and you could see open sea with not a hint of ice for miles along the coast. Halfway across the channel to Baffin Island a very thin sheet of ice lay on the sea with the occasional iceberg ploughing through it and the water not refreezing behind. More ice may drift south but the ice that is there will not last long. Into Hudson Bay parts of the north had more open water than appears on the sea ice concentration map. There was also a lot of 60-70% concentration ice. In the middle the ice was heavily cracked but looked thicker as if would still last a few more weeks. In short, at least for that 100 mile wide slice of the arctic and sub arctic, if any sceptics are reading, my eyes broadly confirmed the concentration map.

Rob Dekker

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Re: The 2017 melting season
« Reply #977 on: April 27, 2017, 06:30:54 AM »
dj, I would suggest you re-post your entry (maybe with the responses from Wipneus and crandles) in a new thread, or use the existing thread on PIOMAS :
http://forum.arctic-sea-ice.net/index.php/topic,119.1600.html

Given that several people responded to you post, and there is no immediate answer, your findings are worth a discussion. Also, I have some thoughts on the issue I would like to share.
But not here in the "melting season" thread.
« Last Edit: April 27, 2017, 06:50:31 AM by Rob Dekker »

Cid_Yama

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Re: The 2017 melting season
« Reply #978 on: April 27, 2017, 06:35:04 AM »
Perception and interpretation is influenced by what you have to lose.  We have a lot of (relatively, I'm 73) young people on here that would rather not accept catastrophe until it happens.

It's ok.  Let them believe what they will.  Reality will come soon enough.  Not like there is anything that can or will be done about it.

   

Rob Dekker

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Re: The 2017 melting season
« Reply #979 on: April 27, 2017, 06:42:03 AM »
However, using Excel's CORREL, the correlation coefficient between the PIOMAS mean March-April-May residuals and the September residuals (1979-2016) comes out at an interesting 0.65

R=0.65 is not bad at all for a March predictor of September SIE.
But what is the SD over the residuals ? And is it better than the SD of 550 k km^2 from the simple linear trend ?
Either way, we should probably take this discussion elsewhere.
You want to take it to the PIOMAS thread ?
« Last Edit: April 27, 2017, 06:47:36 AM by Rob Dekker »

dj

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Re: The 2017 melting season
« Reply #980 on: April 27, 2017, 07:46:19 AM »
dj, I would suggest you re-post your entry (maybe with the responses from Wipneus and crandles) in a new thread, or use the existing thread on PIOMAS :
http://forum.arctic-sea-ice.net/index.php/topic,119.1600.html

Given that several people responded to you post, and there is no immediate answer, your findings are worth a discussion. Also, I have some thoughts on the issue I would like to share.
But not here in the "melting season" thread.


Done at the PIOMAS Update (the link you included).

Bill Fothergill

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Re: The 2017 melting season
« Reply #981 on: April 27, 2017, 10:50:53 AM »
Thank you for the comments and the further resources to explore.

And thank you Wipneus for identifying the weakness (incorrectness) of my comparison, and providing the corrected data. 

Neven, apologies for picking the incorrect place to post this.

As Wipneus correctly (natch!  ;)) pointed out, the NSIDC monthly values for area have a "pole hole". (NB This only applies to area; for extent, they work on the basis that the pole hole is fully covered by ice with >15% concentration, and therefore this is already included in the published numbers.)

I utilise the NSIDC monthly numbers in several of my tables, but, before using any of the values, the following offsets are added...

Nov 1978 - Jun 1987      1.19   million sq kms   
Jul 1987 - Dec 2007      0.31   million sq kms   
Jan 2008 - present      0.029 million sq kms   

(NBB By doing this, I am therefore assuming the pole hole is 100% ice covered. That's becoming a highly questionable assumption, but the current pole hole size is so small, it doesn't overly affect things.)

See...
http://nsidc.org/data/docs/noaa/g02135_seaice_index/#pole-hole-size


 

Bill Fothergill

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Re: The 2017 melting season
« Reply #982 on: April 27, 2017, 11:00:09 AM »
Dear friends, can we please stay on-topic? There are various threads for discussing PIOMAS, volume, thickness, research.

Melting season.
Sorry if it was my post #949 which was initially responsible for the OT seque.

I had been trying to provide a simplistic analysis concerning which metric (PIOMAS/extent/area) might be the better indicator for the forthcoming - and potentially horrific - melt season.

I'll copy #949 over to the PIOMAS thread, and will provide any relevant responses over there.

Thomas Barlow

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Re: The 2017 melting season
« Reply #983 on: April 27, 2017, 02:01:05 PM »
This mixes (colors) concentration with sea-ice thickness maps, so the blue areas (not deeper purples, or reds and blacks) show where the vulnerability is, being both thinner, and slightly lower concentration. Reds, blacks, and deeper purple, show thicker, more concentrated ice.
« Last Edit: April 27, 2017, 02:14:56 PM by Thomas Barlow »

Sarat

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Re: The 2017 melting season
« Reply #984 on: April 27, 2017, 04:54:24 PM »
Interesting graphic, really looks like where ice is close to 100% concentration it's thinner and areas with thicker ice are more fractured.

romett1

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Re: The 2017 melting season
« Reply #985 on: April 27, 2017, 08:45:26 PM »
Sea ice area over Bering Sea is lowest in recent years (black line, about 150,000 km²). In 2012 it was about 600,000 km² at the same time and around 950,000 km² second week of April 2012 (orange line). I'm looking this Wipneus site quite often, all other regions also updated daily, but maybe for new forum readers there is good overview here (third one): https://sites.google.com/site/arctischepinguin/home/amsr2/grf

rboyd

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Re: The 2017 melting season
« Reply #986 on: April 27, 2017, 09:07:51 PM »
Archimid - I started the The Fast Transition topic.

Tigertown

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Re: The 2017 melting season
« Reply #987 on: Today at 05:42:24 AM »
Looking a little haggard.

romett1

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Re: The 2017 melting season
« Reply #988 on: Today at 06:57:55 AM »
Looking a little haggard.

Indeed, we have talked about Bering, Chukchi and ESS, but concentration maps over Atlantic side are not better. Here is another example this morning, lot of cracks near North Pole, also visible on Worldview. Image: ftp://ftp-projects.cen.uni-hamburg.de/seaice/AMSR2/Arc_latest_yesterday_AMSR2_3.125km.png