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Wipneus

When someone asks again whether ENSO influences Arctic sea ice, no need to look further than this Barents sea ice area graph.

My prediction: Barents sea ice will show some recovery in 2013/14.

Werther

Morning Wipneus,
I read your comment on ENSO and Barentsz Sea ice cover. I did a prelim check of both graphs, the AO graph and the MSU/AMSU TMT temp anomaly graph.
I can’t make up a straight parallel between ENSO and the Barentsz Sea. It must me more complicated than that. The immediate analogy, however, is the similarity between Barentsz Sea ice cover and global TMT temp anomaly.
What does it mean: it’s warming, and the Barentsz is warming, too.
An El Nino will contribute in extrapolating that globally through the lower atmosphere. Energy is redistributed, while it is relentlessly stocking up.
The Barentsz Sea has become Atlantic.

Wipneus

Werther:

I am ignoring the long time trend, which is of course negative as all arctic ice trends are.

Look at the wobbles with time scales of a couple of years.

http://www.esrl.noaa.gov/psd/enso/mei/ts.gif

El nino's in 1998,2003/4, 2010; beginning of the 90's (where the global temperature it is obscured by the Pinatuba cooling); two el nino's in the 80's.
Like wise the la nina's in 2011,2008,2000.

It is all there, except perhaps the la nina in 1988/1989.

You are right that ENSO and global temperature are correlated, but here the the correlation is negative: higher ENSO Index<->more Ice area. IOW the opposite what you would natively expect.

idunno

Hi Neven,

Sorry if I'm being obtuse, but I can't find these graphs. There doesn't seem to be an obvious link to them on the CT website.

Can anybody explain where the link is? Ta.

Neven

idunno, just go to the CT website (or the regional graphs page on the daily graphs page) and choose a region on the image with all the nice colours for the different regions. The long-term graphs is on top of the regular graph showing the SIA trend for the past year.

idunno

Sorry, Neven, still not finding them. Maybe a browser problem.

Janne Tuukkanen

How can cold statistics make you to cry :(

Werther

Hi Wipneus,
El NIno 83 had a lagging 2-year low anomaly
87 was followed by 2 y. of high anomalies
La Nina 89 was lagged by 2 y of low ano’s
Nino 92 coincided with a 300K low ano
The 93 and 94 reprises were followed by a 400K low ano i 95
Nino 97-98 (the big one) were followed by 2 y of high ano’s
La Nina 99 and 00 showed off 3 consecutive low Barentsz SI lows
Nino 93-95 gave a lagging downfall of ano’s
Nina 08-09 were still producing negative ano’s, although ‘recovering’
Nino 10 and Nina 11-12 preluded the downfall we witness today

Werther

Wipneus,
The Barentsz/Kara has been in the focus of my attention since september last year. I'm giving me hard time assuming why the course of action proceeds there as it does. Maybe comparison of anomalies isn't the right treat. Better check actual data.
The enigmatic part is what's going on right under the ice. It looks like the oceans are the driver this period. But to find a correlation, the differing measures (MEI/ENSO, PDO, AO, NAO) are too specific. They just don't fit a general approach.The only parameter I got a clue on is AMO, the Atlantic Multidecadal Oscillation.

Chris Biscan

I think the general rise in GHGS might be overlooked in all of this.

Werther

Chris,
I'm sure Wipneus as well as you and me are aware of 'the loading dice'. The intriguing part is to try to make sense of the regional impacts as consequences unfold.

Chris Biscan

I completely agree.

But we can never forget how fast GHGS are rising now. Just one decade is a lot of added forcing just from Co2.

Al Rodger

These new Regional Analyses of SIA from Chryopshere Today have inspired a post at Open Mind on the subject of the additive qualities of Least Squares regressions.
http://tamino.wordpress.com/2012/04/08/l-is-for-linear/#more-4867

William Crump

What is the trend line for the arctic basin for when it will become ice free at the minimum based on this data set?

http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/recent365.anom.region.1.html

Bob Wallace

I don't think you can create a meaningful trend line for the Arctic Basin if you look at only two dimensions of the ice in that area.

Extent/area for the most protected portion of the polar area is going to hold on to the 'bitter end'. But if you look at what is happening to the amount of 3, 4, 5+ year old ice then you can see that even this area is getting set up for a quick melt-out.

Look at all the non-green/white dots in the AB....

http://nsidc.org/arcticseaicenews/files/2012/04/Figure5.png

William Crump

A trend line for older ice would likely show that the Arctic Basin will be free of such ice in the near future and this may be the only conclusion that should be drawn from the volume line drawing exercise. The volume decline trend line reflects primarily the loss of this thick multi-year ice and the loss of volume in regions that have already reached a zero volume point at the September minimum.

I have not seen a data set that shows the rate of decline in thickness of first year ice in the Arctic Basin, so until that becomes available, I will use use the area graph as a substitute.

The Arctic Basin graph shows that it is able to maintain an area of 2.5 million sq km2 at the minimum since 2007. Over this period there has been relatively little decline, so it is possible that the thickness of first-year ice in the Arctic Basis will last far longer than the Arctic wide volume trend line would indicate.

It is possible that the volume of first year ice in the Arctic Basin has not declined at the same rate as multi-year ice as the area occupied by first year ice has expanded as first year ice now forms in areas previously occupied by multi-year ice.

Thinking three dimensionally, what is needed is a data set that uses the thickness of first year ice in the Arctic Basin to predict when the Arctic Basin will become ice free. Using volume data for all regions of the Arctic to predict when it will become ice free is flawed as many regions have reached their zero point and will not contribute to further volume declines. Additionally, the loss of thick multi-year ice will not contribute to the future rate of decline in volume in the same manner as it has in the past because there is so little of this ice remaining.

Werther

Wellcome again…
Just as I felt urged to express my relief at the re-appearance of our blog-friend the Lodger, Mr. William Crump re-emerged from hibernating...
Wellcome.
As we witness once more another Arctic cycle, it’s a privilege to do that with all Neven’s posters...
William, I sense a decline in your firm confidence on the Arctic buffering capacity. Which is perfectly sensible in today’s ‘State of the Environment’, 393,53 ppm CO2 and 1825 ppb CH4.

Mike

In reference to the Arctic becoming free from multi-year ice, as referenced by William Crump, if there is no multi-year ice left does that not imply that the ice would have to melt out every year for there to be only first year ice remaining? Any first year ice that survived the melt would become second year ice and so on, so you would have multi-year ice under that scenario. My contention is that from a purely logical point of view a complete melt-out will occur when there is no multi-year ice left.

William Crump

Werther:

Never said it would not melt out at the minimum, just that it is not going to melt out as fast as the volume trend lines indicate. I am still expecting plenty of ice in 2016. However, 2025 may be a different matter. I see no indication that the Arctic Basin will not be above 2 million km2 in September of 2012.

That is alot of ice to someone from Maryland, which is 32,133 sq km if you count the water. It is bigger than Texas, California and Montana plus 5 Marylands.

Mike:

What about ice that is less than a year old? Ice less than two years old is not multi-year ice.

There will be plenty of ice less than two years old at the September minimum in 2012 even if there is a reduced amount of multi-year ice at that date.

NSIDC states it this way in describing the March 2012 age of the ice:

"Ice age data show that first-year ice made up 75% of the Arctic sea ice cover this March. Thicker multiyear ice used to make up around a quarter of the Arctic sea ice cover. Now it constitutes only 2%." (I think they may be describing ice that is 4+ years old for the 2% statistic).

Based on NSIDC March 2012 chart, 70% of the ice cover is less than a year old. What survives of this 70% at the September minimum becomes one year old ice - still not multi-year ice.

http://nsidc.org/arcticseaicenews/files/2012/04/Figure5.png

Below is chart for September 2011. Note that 50% of the ice was one year ice, which is not multi-year ice.

http://nsidc.org/images/arcticseaicenews/20111004_Figure6.png

Wade

Has anyone else noticed that the images for daily arctic sea ice maps for 2012 are not on exactly the same scale as previous years?

http://igloo.atmos.uiuc.edu/cgi-bin/test/print.sh

If you look very closely at 12, 3, 9, 6 and use a paper or something as a gauge, you see the Earth takes up more of the box, even though the box is the same size.

Is the satellite being de-orbitted or something?

How might this effect calculations of Sea Ice Area, since this should change the real area corresponding to each pixel of the photos?

This is a bit annoying and frustrating, because it makes it difficult to "read" the changes by eye-balling it.

I noticed this a few weeks ago, but didn't complain to anyone.

Hasn't anyone else noticed this?

I mean, changing the scale from one year to another is sort of not good idea for interpretation of data...

Kevin McKinney

"...from a purely logical point of view a complete melt-out will occur when there is no multi-year ice left."

In addition to the 'less than two year-old ice' point made above, surely this would be the other way 'round, anyhow? That is, a "complete melt-out" would imply no multi-year ice in the following year--not vice versa.

There's nothing preventing a hefty chunk of 10-year-old ice from being the last thing to melt, logically speaking.

Neven

Based on NSIDC March 2012 chart, 70% of the ice cover is less than a year old. What survives of this 70% at the September minimum becomes one year old ice - still not multi-year ice.

What survives of this 70% technically becomes second-year ice, I believe. I don't know if that fits the definition of MYI.

Wade, I'm not seeing anything, but then again, I don't use the CT SIA comparison maps much (not enough details).

Peter Ellis

Wade: They don't calculate the ice area from the display images, it's calculated from the actual data files.

To generate the display images, the data is projected onto a plane (polar steroscopic projection), and finally the snow cover data superimposed. A few years ago they changed the "observer" height for the projection, which affects the visual areas slightly. It doesn't affect the actual data.

Mike

Thanks guys I've learnt something about the age of multi-year ice, I now realise that it is more than two years old (duh!). I found that the (truly) skeptical William Crump quotes some very disturbing figures with his 2025 perspective.

Mike

Kevin, I'm just reading your logic, and you are absolutely correct.

Espen

Hi Guys

I am sorry I dont have much time spare for this interesting forum, but this map may give you a knowledge of what the Russians think old/multiyear ice.

Regards Espen

Espen

Sorry I forgot the link, too stressed these days:
http://www.aari.ru/resources/d0015/arctic/gif.en/2011/20111227.GIF

Bob Wallace

William - take a look at this page. Click on the black square to stop the animation and move manually through the years using the "Advance One" button at the bottom.

http://polarbear.colorado.edu/IceAge/Age_Sep.html

As I watch the change in distribution of multi-year ice over the years, especially from 2007 on, I don't end up thinking of the Central Basin as being a strong hunk of thick ice, but simply the place where the oldest ice at the time gets shoved by the end of the melting season.

(Unfortunately 2011 and 2012 have not yet been added.)

This ice moves. It moves out of the area and melts. It gets replaced to some extent, but that isn't likely to continue for very long as the extent minimum drops.

Will the 'big melt-out' happen this year, by 2015 or not for another decade or so? I can't tell. I'd guess not this year, but I leave the door open. More than five years from now? I doubt that, but again I'm just guessing.

William Crump

Thanks for the animations and links - good stuff.

The volume trend line appears to be leveling out with 2012 closely tracking 2011. Is it possible that the regime of rapid decline in volume prior to 2011 has been replaced by a new phase of slower volume decline because of the demise of thick multi-year ice?


Bob Wallace

William -

I find it hard to determine a trend from one data point.

Watching the monthly PIOMAS graph it looked like we might see some volume growth when January was posted. By March it looks like volume was slightly down from 2011. Where is goes from now is something we'll have to wait to see.

Apr 12 Monthly Death Spiral

https://sites.google.com/site/arctischepinguin/home/piomas/piomas-trnd2.png


Will volume level out, grow, or continue on its downward path? My guess is that we'll get more of what we've been getting. The slight uptick is not unusual based on the previous thirty-some years of ice loss.

Were I a betting person I would bet we see a lot of volume loss early in the melt season. There seems to be a lot of thin ice and a lot of the current volume is in the "Pacific outside" where melt is usually early and complete.

crandles

>"Is it possible that the regime of rapid decline in volume prior to 2011 has been replaced by a new phase of slower volume decline because of the demise of thick multi-year ice?"

It should be obvious that you should expect the opposite. This is because multi-year ice is harder to melt through being fresher after brine rejection. So melting point is higher and the temperatures are likely to be above this higher melting point for a shorter period of time and by a smaller temperature margin.

If there is a decline in rate of volume decline, which is hard to spot as previously pointed out, then it would almost certainly be for different reasons. (and you should know that)

William Crump

Thanks Bob for the graph and I concur that we need 2-3 years of data before saying it has leveled off. I also agree with your assessment that we will see a rapid melt in the Bering Sea, but how much volume will this thin less than a year old ice represent? Additionally, I would not expect the Bering sea to have any additional impact on the volume measure at the minimum as the Bering sea has consistently hit a zero volume point at the minimum during the period of satellite records.

http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/recent365.anom.region.2.html

What is your assessment of the percentage of volume at the minimum during the period 2007 through 2011 that was in the Arctic Basin?

Crandles:

Empirical observations indicate that thick multi-year ice has diminished at a faster pace than younger ice. This is based on the NSIDC age of ice chart.

Maybe the deeper multi-year ice is subject to more bottom melt than first year ice. Maybe because it sits up higher it is more likely to be driven by winds. Regardless of the physics of which type of ice can be more easily melted by a blow torch, the empirical observations show that multi-year ice has declined more than other types of ice.

That is what the NSIDC has said:

After the near-record melt last summer, second-year ice declined again, but some of the ice that had survived the previous few summers made it through another year, increasing the proportion of third- and fourth-year ice. However the oldest, thickest ice, more than four years old, continued to decline. Ice older than four years used to make up about a quarter of the winter sea ice cover, but now constitutes only 2%. First-year ice (0 to 1 years old) this year makes up 75% of the total ice cover, the third highest at this time of year in the satellite record. In 2008 the proportion of first-year ice was 79%, and in 2009 it was 76%.

While it may be "obvious" to you that we should expect first year ice to disappear faster than multi-year ice, the facts as reported by NSIDC do not match that expectation.

http://nsidc.org/arcticseaicenews/files/2012/04/Figure5.png

crandles

>"While it may be "obvious" to you that we should expect first year ice to disappear faster than multi-year ice, the facts as reported by NSIDC do not match that expectation."

While above post you just made may be obvious to you, you seem to be missing alternative/extra explanations. The multi-year ice may be being flushed out of the Fram Strait and into Beauford at a faster rate than it can recover by making it round Beauford Gyre or though aging. This might lead to faster demise of multi-year ice than first year ice.

You posted a picture from Acticseaicenews to support what you were saying but it doesn't say anything about mechanisms which lead to the multi-year ice dissappearing faster.

Instead here is something else from Acticseaicenews:

"This multi-year ice appears to have played a key role in preserving the tongue of ice extending from near the North Pole toward the East Siberian Sea"
http://nsidc.org/arcticseaicenews/2011/10/

I think that is clearly saying that the multi-year ice is harder to melt. I was actually looking for a quote saying something to effect that Beauford had melted rapidly until it reached the multi-year ice when the melt slowed down. I think this quote will do but there are others out there. Also think this is more relevant to mechanisms we are discussing than the fact we seem to agree on that multi-year ice is disappearing at a faster rate than one year ice.

crandles

Sorry posted that half complete as I had to go.

I am arguing multi-year ice is harder to melt but is disappearing faster because large portions of it are being advected into regions where it will melt despite it being harder to melt.

Therefore, I think your "Maybe because it sits up higher it is more likely to be driven by winds." is supporting my position. Despite that, I think I disagree. There is more freeboard so wind has more to act on but there is also more mass to accelerate. More water resistance may matter more to top speed than there being more freeboard to act on.

>"Maybe the deeper multi-year ice is subject to more bottom melt than first year ice."

I am not objecting to faster melt being possible because thicker ice reaches down to warmer water. However, this argument does seem to have a couple of problems to overcome:

Firstly, it is admitting the multi-year ice is thicker so there is more ice to melt before an area becomes ice free through melting.

Secondly, suppose there is a faster rate of melting. So the thickness reduces at a faster rate beginning to catch up towards making thickness the same. If the reason for faster melting has then reduced or disappeared, why would the faster rate of melting continue? More/deeper melt pools trapping more heat perhaps? Seems rather dubious that it would overtake to me.

Hence, after reviewing your arguments, I don't see any reason to budge from "It should be obvious that you should expect the opposite."

My "(and you should know that)" might seem a little ill tempered but we have discussed this on this blog a few times and your position of multi-year ice must be easier to melt because it is disappearing faster along with other aguements do not seem to develop at all despite all the attempts to provide you with additional pointers/evidence/arguments. What do you do when someone won't change their argument despite all the arguments against that you present?

Peter Ellis

You're talking past each other.

Crandles: you're discussing how fast first-year or multi-year ice melts within a given season. Here, FYI melts much faster than MYI.

William is talking about thinning of a given class of ice from year to year. That is, if you compare the thickness of 2011 MYI to 2010 MYI, which is thicker? If you compare the thickness of 2008 FYI to 2007 FYI, which is thicker? That is a completely different question!

Addressing that question, then he's right. The thickness of FYI varies comparatively little from year to year. It gets to a maximum of ~2m or so and then stops growing. FYI formed in 2011 is much the same as FYI from the 90's, or the 80's, or the 70's. In contrast, MYI has not only been shrinking in area but also thinning - previously the MYI fraction in the Arctic could be up to 10m+ thick: these days it's ~3-5m.

John Christensen

crandles and Peter:

This is why it seems that water temperatures are rising more than air temperatures in the Arctic: MYI is more or less constantly thinning from below, but FYI has only been around since last winter, where the cold atmosphere (still) has dominance from above, so warmer water has less visible impact on FYI.

crandles

>"William is talking about thinning of a given class of ice from year to year. That is, if you compare the thickness of 2011 MYI to 2010 MYI, which is thicker?"

Is he? Let me quote
"Crandles:

Empirical observations indicate that thick multi-year ice has diminished at a faster pace than younger ice. This is based on the NSIDC age of ice chart."
later link is to
http://nsidc.org/arcticseaicenews/files/2012/04/Figure5.png

That chart is showing area percentage of multi-year dropping. So I think he is talking of area dropping not thickness dropping as Peter asserts (well at least some of the time).

I am not in any way disputing the numbers on the graph that the multi-year ice area is dropping faster than the area of first and second year ice (which in percentage terms seem to be growing not declining).

I am disputing the reasoning William is kind of promoting with things like:

"Is it possible that the regime of rapid decline in volume prior to 2011 has been replaced by a new phase of slower volume decline because of the demise of thick multi-year ice?"
and
"Maybe the deeper multi-year ice is subject to more bottom melt than first year ice."

Nevertheless we could be talking past each to some extent and if those quotes are addressing different issues to what I thought they were then fair enough we are talking past each other. Sorry for my part in any such confusion caused.

crandles

I do agree that multi-year ice is getting thinner.

Clearly part of the explanation is that the area of old ice that is now advecting into areas where it melts out is becoming a huge proportion of the multi-year ice area.

Hence, there is now very little 10+ year ice included in 5+ year ice. In the past 10+ year ice would be thick through having been crushed for long periods of time.

That obviously doesn't apply when comparing 2011 4-5 year ice in 2011 against 2010 4-5 year ice in 2010. For this we have to realise there is so little of it now, it can only be created from ice in a few fortuitous locations that don't get advected out. This holds out the posibility that 4-5 year ice could actually be getting thicker because so little of it is being created. The volume of this 4-5 year ice would clearly be going down and likely to practically disappear soon.

If the MYI is thinning from below almost constantly as well as the large proportion now advecting into areas where it will melt out, then it clearly isn't going to last long and we will get practically ice free days fairly soon. I think there is additional first year ice being frozen onto bottom of ice for a good proportion of winter. That melts off easily compared to the MYI but still provides some protection against melt in situ during summer.

Anyway, I don't want to believe "MYI is more or less constantly thinning from below" and don't consider it necessary for a near complete melt out for a few days in a year. However, do convince me with evidence rather than my silly ramblings if you can.

John Christensen

I am quoting from the same Science article that mentions a general warming of AW since 1850, but also studied more closely recent AW warming events ("Enhanced Modern Heat Transfer to the Arctic by Warm Atlantic Water", Science, 1/28/2011):

"Both effects—a temperature rise as well as a volume transport increase—introduce a larger heat input into the Arctic Ocean. Although there is no direct contact of the AAWL with the ocean surface in the Arctic, such an increased heat input has far-reaching consequences. The strong AW warming event in the Arctic Ocean in the 1990s caused a shoaling of the AW core and an enhanced heat flux to the surface (29), concurrent with decreasing sea ice (4). Recent oceanographic data from the Laptev Sea continental margin indicate the impact of warm AW-related water masses on the shallow (<50 m) shelf (30), a feature not observed before in a >80-year time series. The data also provide evidence for a significant heat flux to the overlying shelf waters (30). Even without any modification of the vertical heat transfer processes, the enhanced temperature contrast between the AW and the surface sea water freezing point (increased from ~5 to 7 K as identified here) leads to an increase in the vertical heat flux of ~40%."

I do not know enough about the level of energy transferred in the heat flux to the top layer of water under the ice that may be -1,9C, but if the AW layer (50-600m depth) in that area has seen an increase in temperature from 2,8-4,4C (before 1890) to 4,1-6,0C today, it sounds unsustainable in the longer run.

John Christensen

Note: The temperature increase mentioned is found in the east side of the Fram Strait, where Atlantic water enters the Arctic Basin.

crandles

I said the above were silly ramblings and I think I need to withdraw some of the silliness (perhaps only partially).

Thick MYI may well be reaching down to warmer water and be melting from below almost all the time. I think I do wish to argue that this is a small unimportant effect that is overwhelmed by the MYI being crushed into a smaller area that becomes higher. The older multi-year ice is thicker than newer multi-year ice, so the thickening effect must be dominating any melting from below and above thinning.

Going forward, the MYI is getting thinner. Taking the dominating crushing effect first: The thinner ice is weaker and more prone to being crushed initially but there is less mass of ice out there to do the crushing. While it will initially crush a bit, the eventual thickness that it will tend to grow towards will get thinner as the mass of ice in the basin decreases.

Melting from below may also decline as the thickness reduces the reach into warmer water. Also as the thickness reduces below 2m max for first year ice, it will gain FYI ice to bottom in winter.

So my "I don't want to believe MYI is more or less constantly thinning from below" should only be applied to thin MYI and it may be true for thicker MYI but even then is cancelled by the ice being crushed into smaller thicker areas.

.

"an increase in the vertical heat flux of ~40%." is impressive. Does that mean the 2m maximum thickness for FYI without crushing/slabbing etc is reduced to 1.43m or perhaps even less if there is some snow providing more insulation than ice?

William Crump

Thank you Peter Ellis.

Crandles:

Which class of ice has contributed more to the decline in volume:

A. ice that is a year old or less that now covers more area than it used to cover and had a larger volume in the winter of 2008 than it did in 2004 per ICESAT

http://www.nasa.gov/images/content/365871main_earth3-20090707-full.jpg

http://www.nasa.gov/images/content/365869main_earth2-20090707-full.jpg

or

B. ice that is four plus years old which used to constitute 25% of the ice area with a thickness of 10 meters but now constitutes 2% of the ice area and has an average thickness of 3.5 meters?


What is the rate of decline in the thickness of ice that is under two years old at the September minimum in the Arctic Basin?


crandles

I think we both fully agree that the answer is B and there is not much, if any, *average* thickness decline in ice under two years old.

I think this is very bad news because if the ice was 80% FYI and 20% second year ice and had area 13m km^2 and volume of 19.5k km^3 then the volume and type of ice would be such that it would practically all melt.

Last 4 years have melted over 18k km^3 and I think this would go up with less MYI and other reasons*.

Do you think it would go down? If so, why?

PIOMAS max volume is down to about 22k km^3. With continued loss of thick MYI, volume falling from 22k down to 19.5k seems to be at the edge of possibility if all MYI converts to 2nd year ice at a meter thinner.

Or do you think we have lost all the thick MYI we are going to lose?


A Entrance to safe area
B Safe area
CDE Exits from safe area
Compare size of A with sum of C, D & E.
(I have drawn areas roughly by hand, but what periods do you think they represent?)

*Other reasons:
If more is melted when there is less MYI then more area is likely to open up so more heat absorbed from albedo feedback.

Also freeze up is likely to be delayed which could lead to thinner FYI. I know there is no sign of this yet, but the area of FYI is spreading into more central areas which will be thicker, thereby hiding the thinning of FYI at the edges. When that spread stops, thinning of FYI at edges may become apparent in average thickness of FYI figures. I believe this thinning at edges is happening leading to more area opening up sooner, so more albedo feedback....


Maybe volume at max decline has ceased this year at 22k km^3, but it is too soon to tell and I think it is more likely to be natural variation causing a brief pause on way down and further MYI will be lost causing more thinning.

William Crump

Crandles, thanks for the quick response.

I will try to address the specific questions you are asking later tonight.

My assertion is that because most of the loss of ice volume has been in the multi-year ice and there is very little ice left that is multi-year ice, I would generally anticipate a slowing in the rate of decline of volume as determined by the PIOMAS chart.

For this reason, I do not believe the future trend lines that have been drawn using Arctic wide volume data can be used as a predictor of when a particular month will become ice free.

I suspect that there may be an acceleration in the rate of decline of young ice in the Arctic Basin (as defined by Cryosophere Today), but I do not think the volume loss will be as rapid as the trend lines drawn from PIOMAS volume data would suggest.

William Crump

Crandles:

The bad news has already occurred in the Arctic with ice older than 4+ years reduced by 92% and the remaining 8% of the multi-year ice down in thickness from 10 meters to 3.5 meters. Lets call this a disaster, not just bad news.

While it may be counter-intuitive that thin first and second year ice are declining at a slower rate than the multi-year ice, it may relate to the ability of the Arctic to more easily replenish young ice compared to the years it takes to build up thick multi-year ice once it is gone, (I do not see any evidence that the ice sheet in the Arctic will be able to be restored to the quality of ice which existed in the 1990's.)

I focus on the Arctic Basin region because it will be the last region to melt out. At the minimum for the last 5 years, this region has bounced around 2.5 million km2 in area, a significant number that constitutes more than 80 percent (by area) of the ice remaining at the minimum.

While it is undoubtedly thinning, I do not see and have not found a data set for the thickness of this young ice that would generate a trend line showing that it will be gone by 2016. Until then or until I see a sudden decline in the area of ice coverage in the Arctic Basin to 2.0 million and subsequently 1.5 million, it appears to this viewer that the ice in the Arctic Basis will be with us for a little longer than the 2016 projection and volume trend lines indicate.

William Crump

Bob Wallace:

The trend lines on the chart you site shows monthly average volume for the northern hemisphere will be zero from July through November by 2015.

Do you believe this will occur?

Werther

William,
I have been critical on your entries last year. But as we are hopefully all learning in the process, I feel you are a partner. We may not always agree, but you have held a consistent view on this while remaining polite.
As for now, I feel the demise may be represented better through a regional maze/loop pattern than an overall linear/exponential one. Maybe your view is valid (for a while). But beware of the 'mule'-event, an unforseen situation, quote Asimov's Foundation trilogy.

crandles

>"My assertion is that because most of the loss of ice volume has been in the multi-year ice and there is very little ice left that is multi-year ice, I would generally anticipate a slowing in the rate of decline of volume as determined by the PIOMAS chart."

Providing we are taking about volume at maximum then yes I agree about the slowing in the rate of decline. The thinner the ice is at the end of the melt season, the more heat can be lost and the ice can grow more quickly. This shouldn't lead to more ice volume at maximum because as the ice volume catches up to previous years volume, the reason for faster growth of ice volume disappears.

Also note that this only applies to ice that is thinner than 2m or whatever FYI can grow to. If we are losing MYI that is thicker than 2m, this doesn't apply as it won't grow thicker by freezing only by crushing.

Not sure where your 8% comes from as it looks like about 15% at March 2012 on the graph on NSIDC news.

Although we are down to 8/15% MYI at 3.5m thick, there is still some further volume losses before that leveling off in the maximum ice volume. Even using your figures 1.5m * 8% * 13m gives a 1560 km^3 further loss if all of that 8% MYI thins to 2m reducing 22k km^3 to 20.5k km^3.

Also note we seem to be saying the rate of loss declines not that it stops dead at 20.5k km^3. I think there is other thinning occuring besides just in the MYI and that means that the volume at max is likely to fall further before leveling off. Meanwhile the volume that melts each year continues to rise with albedo feedback and less difficult to melt MYI. So it seems likely to me that the max volume and the melt volume will get very close to each other fairly soon if the PIOMAS figures are correct. Note that only fairly small errors in the direction necessary would allow melt volume decline to level off at a level above the max volume leading to a much later date for an ice free arctic as you are suggesting.

Daniel Bailey

"I focus on the Arctic Basin region because it will be the last region to melt out."

This flies in the face of what we know of wind, weather and currents in the Arctic. One need merely consult an ice thickness chart to see where the declines have occurred over time.

The sheltered northern lees of Greenland and the Canadian Archipelago are much more likely to be the repository of the last remnants of ice in the Arctic Ocean than is the highly mobile, thinner ice of the Central Arctic Basin.

Bob Wallace

"...will be zero from July through November by 2015. Do you believe this will occur?"

Again, William, I have not formed a belief.

I look at the recent year history and see that if things continue as they have then it seems possible.

I've attempted an inventory those factors which speed the destruction of the ice and those which might increase in strength and reverse (or greatly slow) the melting. Based on what I know to date I do not form a feeling that Arctic sea ice has a long future ahead when it comes to continuous year-round ice.

But I leave the door open to some unforeseen slowing in the melt. Weather south of the Arctic seems to be getting quite weird at an alarming rate. It's hard to guess at what strangeness might occur during the next few years.

crandles

Daniel,

Perhaps that area is what William means per CT defined areas:

Also, an ice thickness chart will show largest thickness reductions from circa 10m -> 3.5m in the region we all think will be the last refuge of the summer ice. So I think you meant something other than an ice thickness chart. Perhaps an ice motion animation?

Daniel Bailey

Effin' Typepad not letting me post again.

Daniel Bailey

OK, just won't let me use any html.

Daniel Bailey

(No-hashtag version)

@ crandles

Not having Neven's facility with animations I can merely speak to what I meant. If one were to look at the various NSIDC sea ice age charts over time, then one would be able to see the retreat of the thicker ice towards those areas I mentioned. Such as in this graphic:

http://nsidc.org/arcticseaicenews/files/2012/04/Figure5.png

Or this animation from PIPS 3:
http://www.oc.nps.edu/~pips3/anim/heff18y365d.avi

When viewed over a long enough period of time, one sees the trend in the overall thinning of the ice, with the areas nearest North America better retaining the thicker (and therefore last to melt) ice. Ice transport will dominate the Central Basin declines, as the mechanically weaker ice will serve little deterrence to wind and current + weather systems.

Mr. Crump has on several occasions conflated the Arctic Basin with the Central Basin/region of the North Pole in his rear-guard action (which to me seems but hand-waving) to deny what is visually happening in the Arctic.

Again, only Maslowski's model has come close to replicating what time has revealed to be the case WRT Arctic sea ice (and its demise). Still on course, the death spiral continues...

A keeper:
http://www.youtube.com/watch?v=LjaVp6AS5XU

William Crump

For the record, when I use the phrase "Arctic Basin" I am referring to the light green area on Cryosphere Today which is represented by this graph:

http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/recent365.anom.region.1.html

Other sources appear to call this the central Arctic Basin but the areas do not always appear to match up with each other and I find that confusing so I generally reference the discussion back to Cryosphere Today as a source.

Thank you Daniel Bailey for correctly pointing out that certain areas where winds pile up ice will be the last to melt out, such as the sheltered northern lees of Greenland and the Canadian Archipelago. I have not focused on these areas as I have seen multiple sources

As a week defense to my focus on the Arctic Basin, in most discussions on the topic of "ice free" the term has generally been described in a fairly loose fashion as being ice free except for the areas mentioned by Daniel Bailey or as being a state at the minimum when total ice extent/area falls below some threshold such as 300,000 km2 rather than the absolute zero ice situation of 0.00km2.

The 8% figure is based on the information provided by NSIDC when they stated:

"Ice older than four years used to make up about a quarter of the winter sea ice cover, but now constitutes only 2%."

The 8% is derived by dividing 2% by 25%. The 92% figure for missing old ice is calculated by dividing 23% by 25%.

I do not have the source of the 10 meters to 3.5 meters decline, but these appear to be accepted numbers based on information provided by other commentators on this excellent site.

crandles

OK, I misread what the 8% represented and consequently the calculation of further ice loss before negative feedback kicks in was wrong. I wanted to refer to 3+ year ice so the 15% off the NSIDC article graph is more appropiate.

http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictnnowcast.gif

indicates 2.5 to 5m thick MYI which would make an average somewhere around 3.5 but I think it may tend to overestimate thickness for safety of shipping reasons. So the 1.5m difference from 2m to 3.5m I used may well be a little on the high side.

1m * 15% * 13m km^2 = 1950 km^3 which would bring the volume down to 20k km^3 without considering any other volume loss in 1 and 2 year ice. That seems awfully close to a more that 18k km^3 melt volume that I expect to continue to grow and natural variability can cause to vary by 2k km^3.

Chris Reynolds

I'm still reading this thread, but the Science paper John Christensen refers to about Atlantic Water influx during the last 100 years being very anomalous in the context of the last 2000 years is here:
http://instaar.colorado.edu/~marchitt/publications.html
Third paper down, no paywall.

I strongly recommend this paper for those interested in the Arctic, which is everyone here...

Tor Bejnar

I was hoping to see an updated Arctic Sea Ice Extent Maximum/Minimum Day… chart, and noticed that http://i137.photobucket.com/albums/q210/Sekerob/Climate/ArcticSIEDaysMillionStepMelts.png has a latter date than the chart on the long-term graphs page.

Neven

Thanks a lot, Tor. I had uploaded an image I had on my hard drive, as I couldn't find the link to Sekerob's updated image. I've linked to it directly now on the long-term graphs page.

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