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gerontocrat

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Re: The 2020 melting season
« Reply #6200 on: September 19, 2020, 12:37:29 AM »
This is the best thread on the Internet. Thanks, everyone.

Neven, I join many others in thanking you for hosting us and making all this possible, and thanking Oren also for his excellent moderation.  This is such a valuable service to us as individuals.  You provide vital leadership in spreading understanding of what is happening to our beleaguered planet.
I was looking for a place for years and luckily for me I found it - the ASIF.
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be cause

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Re: The 2020 melting season
« Reply #6201 on: September 19, 2020, 02:02:01 AM »
 .. and you the best bit of first year ice in sight .. I bet Polarstern would be glad to find a floe with your characteristics .. especially as daughter of Sally spins in just as it all goes dark . b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 + 1 =  ' if only we could have seen it coming ' ...

bbr2315

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Re: The 2020 melting season
« Reply #6202 on: September 19, 2020, 02:28:16 AM »
If the PIOMAS update is correct the melt season may be ongoing when it comes to ASI volume. It was second place and plunging as of 9/15. While the plunge is unlikely to continue the massive cyclonic activity forecast to envelope the ATL - Eurasian front is likely to result in major problems for the remaining MYI while the area / extent gains in Beaufort will be very thin ice.

Given the latest PIOMAS update and the fact that volume is perhaps the most significant metric, I would suggest that this thread be pinned until the next PIOMAS update confirms a minima has indeed been reached because we may not be there yet and there is some possibility we may not be there soon.

oren

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Re: The 2020 melting season
« Reply #6203 on: September 19, 2020, 02:42:00 AM »
PIOMAS is quite sensitive to NSIDC area, and I am sure has by now reached its minimum, even if it did not do so on the 15th.

OffTheGrid

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Re: The 2020 melting season
« Reply #6204 on: September 19, 2020, 03:13:52 AM »
The crude piomas model <unsubstantiated dissing snipped>.
Hycom has not been falsified by any direct ice thickness measurement by human or buoy. We have about 25% of 2012 ice volume currently <warning: not true>, and far more near surface ocean heat with far thinner fresh surface barrier. It's basically inevitable that big storm activity will wreak havoc on what's left as continental temperatures drop, but Arctic ocean heat is unable to.

<Please make sure posts are fact-based. O>
« Last Edit: September 19, 2020, 06:27:57 PM by oren »

Ktb

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Re: The 2020 melting season
« Reply #6205 on: September 19, 2020, 03:16:59 AM »
Hycom updated their model a couple years ago and it is not possible to compare the updated version to the old version. This is well documented on the ASIF
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gandul

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Re: The 2020 melting season
« Reply #6206 on: September 19, 2020, 04:16:08 PM »
It’s been a really interesting melting season.
When will we see a GAAC again? A 20-day powerful and warm anticyclone dominating most of the Arctic in July.
There will be papers in the next years trying to explain it.

nanning

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Re: The 2020 melting season
« Reply #6207 on: September 19, 2020, 05:45:03 PM »
Thanks OffTheGrid.
If hycom is correct, and I must say that hycom's thickness graphs are a lot more likely than PIOMASS imo even with changed methods, then indeed a new record low volume is set. As is quite definitely expected by me after such an extreme melt season. Not very scientific of me of course but we do not have good 'sensors' regarding the arctic sea ice. There's a lot unknown and it's an extremely important piece of the planet, being a 'tipping point'. A couple of submarines would be nice. Dear Mr.Wadhams, do you still have some contacts there?
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gandul

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Re: The 2020 melting season
« Reply #6208 on: September 19, 2020, 06:28:55 PM »
Thanks OffTheGrid.
If hycom is correct, and I must say that hycom's thickness graphs are a lot more likely than PIOMASS imo even with changed methods, then indeed a new record low volume is set. As is quite definitely expected by me after such an extreme melt season. Not very scientific of me of course but we do not have good 'sensors' regarding the arctic sea ice. There's a lot unknown and it's an extremely important piece of the planet, being a 'tipping point'. A couple of submarines would be nice. Dear Mr.Wadhams, do you still have some contacts there?
No it’s not, and also read ktb post above, you’re looking at two different hycoms the 2012 hycom at that time, that grossly overestimated thickness and the ‘corrected’ glb hycom in 2020 that grossly underestimates it

oren

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Re: The 2020 melting season
« Reply #6209 on: September 19, 2020, 06:31:26 PM »
I edited some of OTG's comment since it was very far from the truth. 2020 Hycom cannot be compared to 2012 Hycom. There is zero indication sea ice volume is 25% of what it was in 2012. And Hycom cannot be falsified by buoy or local measurement, as it shows average thickness and not hi-res point thickness. Neither can PIOMAS. So this is irrelevant.

Glen Koehler

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Re: The 2020 melting season
« Reply #6210 on: September 19, 2020, 08:02:18 PM »
     I think OTG reference to 25% of Volume refers to 2020 (or 2012) in comparison to 1978.

oren

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Re: The 2020 melting season
« Reply #6211 on: September 19, 2020, 10:10:33 PM »
The reference was clear, 2012 vs. 2020 per the attached Hycom images.

interstitial

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Re: The 2020 melting season
« Reply #6212 on: September 19, 2020, 11:26:32 PM »
Thanks OffTheGrid.
If hycom is correct, and I must say that hycom's thickness graphs are a lot more likely than PIOMASS imo even with changed methods, then indeed a new record low volume is set. As is quite definitely expected by me after such an extreme melt season. Not very scientific of me of course but we do not have good 'sensors' regarding the arctic sea ice. There's a lot unknown and it's an extremely important piece of the planet, being a 'tipping point'. A couple of submarines would be nice. Dear Mr.Wadhams, do you still have some contacts there?
No it’s not, and also read ktb post above, you’re looking at two different hycoms the 2012 hycom at that time, that grossly overestimated thickness and the ‘corrected’ glb hycom in 2020 that grossly underestimates it
The regional and global hycoms have some overlap and the older regional one produce 1-2 meter thicker ice. Before assuming that they are both grossly wrong consider that this transistion between models coincides with several other arctic changes. Loss of multi year ice, destabilisation of halocine, high speed trip to north pole by Polarstern, increasing rain, continually warmer temperatures, cracking along Greenland CAA. The assumption that a substantial change in thickness didn't occur ignores all the indicators pointing to the contrary.  The newest regional hycom data was too thick which was part of the reason why they created the new model.

Glen Koehler

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Re: The 2020 melting season
« Reply #6213 on: September 19, 2020, 11:57:21 PM »
The reference was clear, 2012 vs. 2020 per the attached Hycom images.
   I agree that is what he said.  I was just trying to point out that he was applying the wrong starting year to the often-cited 75% decline in ASI Volume.

be cause

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Re: The 2020 melting season
« Reply #6214 on: September 20, 2020, 09:36:55 AM »
    https://modeles.meteociel.fr/modeles/gfs/runs/2020092000/gfsnh-0-114.png?0 ..
  the forecast storm hasn't gone away .. the next week will test the ice . Today's (expected) drop in extent shows that the certainty the melting season is over may prove premature .
 and the forecast continues until the term GAC may again become relevant ..
  https://modeles.meteociel.fr/modeles/gfs/runs/2020092000/gfsnh-0-186.png?0
 .. and warm air continues to flow from Eurasia ..
  https://modeles.meteociel.fr/modeles/gfs/runs/2020092000/gfsnh-15-84.png?0 . b.c.
 
 
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 + 1 =  ' if only we could have seen it coming ' ...

OffTheGrid

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Re: The 2020 melting season
« Reply #6215 on: September 20, 2020, 10:49:37 PM »
Well, Hycom certainly doesn't think the melting season is over. And with SSS at 31 a degree above melting point is the water temperature under Mosaic, 2 degrees whenever there is any winds. With what's forecast in the next two days, it's going to be very interesting. Btw that thick looking bit north of svalbard is a stream of icebergs from Greenland.
As usual, click the gifs.

A-Team

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Re: The 2020 melting season
« Reply #6216 on: September 20, 2020, 11:48:00 PM »
Quote
GlennK: what was so special about 2007?
Indeed, the extreme ice loss in the summer of 2007 really caught people's attention at the time. I came across a couple of assessments made shortly thereafter that attributed the outcome to Arctic conditions not unlike 2020. The ice by now was a lot younger and thiner than in 2007:

Sunlight, water, and ice: extreme Arctic sea ice melt during the summer of 2007
DK Perovich, JA Richter-Menge, KF Jones and B Light. 2008
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008GL034007

The summer extent of the Arctic sea ice cover, widely recognized as an indicator of climate change, has been declining for the past few decades reaching a record minimum in September 2007. The causes of the dramatic loss have implications for the future trajectory of the Arctic sea ice cover. Ice mass balance observations demonstrate that there was an extraordinarily large amount of melting on the bottom of the ice in the Beaufort Sea in the summer of 2007. Calculations indicate that solar heating of the upper ocean was the primary source of heat for this observed enhanced Beaufort Sea bottom melting. An increase in the open water fraction resulted in a 500% positive anomaly in solar heat input to the upper ocean, triggering an ice –albedo feedback and contributing to the accelerating ice retreat.

Arctic Sea Ice Extent Plummets in 2007
J. Stroeve, M. Serreze, S. Drobot, S. Gearheard, M. Holland, J. Maslanik, W. Meier,  T. Scambos
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008EO020001

Arctic sea ice declined rapidly to unprecedented low extents in the summer of 2007, raising concern that the Arctic may be on the verge of a fundamental transition toward a seasonal ice cover. Arctic sea ice extent typically attains a seasonal maximum in March and minimum in September. Over the course of the modern satellite record (1979 to present), sea ice extent has declined significantly in all months, with the decline being most pronounced in September. By mid-July 2007, it was clear that a new record low would be set during the summer of 2007.

While this thinning set the stage for pronounced summer ice loss, its effects were compounded by a favorable pattern of atmospheric circulation. An anticyclonic pattern over the central Arctic Ocean that formed in early June persisted for 3 months and was coupled with low pressures over central and western Siberia. Satellite data reveal that skies under the anticyclone were predominantly clear, fostering strong melt. Persistent southerly winds between the high- and low- pressure centers gave rise to above-average air temperatures north of Siberia that promoted melt and also transported ice away from the Siberian coast.
« Last Edit: September 21, 2020, 03:50:43 AM by A-Team »

binntho

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Re: The 2020 melting season
« Reply #6217 on: September 21, 2020, 08:12:27 AM »
Btw that thick looking bit north of svalbard is a stream of icebergs from Greenland.

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kassy

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Re: The 2020 melting season
« Reply #6218 on: September 21, 2020, 12:57:09 PM »
And with SSS at 31 a degree above melting point is the water temperature under Mosaic, 2 degrees whenever there is any winds.

SSS is Sea Surface Salinity with the scale in PSU not degrees F.
And for SST they use C.
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Davidsf

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Re: The 2020 melting season
« Reply #6219 on: September 21, 2020, 02:48:37 PM »
Thank you Oren. Thank you everyone for an educational melting thread. See you on the freezing thread or next year. Stay well, David

gerontocrat

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Re: The 2020 melting season
« Reply #6220 on: September 21, 2020, 02:53:57 PM »
Quote
GlennK: what was so special about 2007?
Indeed, the extreme ice loss in the summer of 2007 really caught people's attention at the time. I came across a couple of assessments made shortly thereafter that attributed the outcome to Arctic conditions not unlike 2020. The ice by now was a lot younger and thiner than in 2007:

Arctic Sea Ice Extent Plummets in 2007
J. Stroeve, M. Serreze, S. Drobot, S. Gearheard, M. Holland, J. Maslanik, W. Meier,  T. Scambos
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008EO020001
 Satellite data reveal that skies under the anticyclone were predominantly clear, fostering strong melt. Persistent southerly winds between the high- and low- pressure centers gave rise to above-average air temperatures north of Siberia that promoted melt and also transported ice away from the Siberian coast.
What I take from 2007 was that was the first year of a significant loss of sea ice extent and area in the Central Arctic Sea, i.e. North of 80 was breached on the Atlantic front, and even more stunning, 85 North was breached North of the ESS (at 165 East).

And now in 2020, to quote https://nsidc.org/arcticseaicenews/ on Sept 16th,
Quote
North of Scandinavia and Russia, a very broad sea-ice-free area exists with the ice edge lying near 85 degrees N, far to the north of Svalbard, Franz Josef Land, and Severnaya Zemlya (Northern Land) (Figure 1c). The sharply defined ice edge in this area, between about 0 degrees and 100 degrees longitude, indicates strong compaction of the ice by winds coming from the south and is the furthest north the ice edge has been in this location over the satellite data record.

That ice edge retreated north of 85 North for a few days more.

I have always been convinced by the arguments to support that bathymetry provides resistance to melt along that Atlantic front, but I am also convinced by the simple equation...

Global Heating + Polar Amplification = Resistance is Futile.
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BornFromTheVoid

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Re: The 2020 melting season
« Reply #6221 on: September 21, 2020, 03:23:31 PM »
As it's the end of the melt season, here's all the extent projections from March 1st to last week, using daily data from the last 20 years.
A pretty big file size, click to play.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

KenB

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Re: The 2020 melting season
« Reply #6222 on: September 21, 2020, 04:50:40 PM »
As it's the end of the melt season, here's all the extent projections from March 1st to last week, using daily data from the last 20 years.

Very slick, thanks.  One of my favorite parts of ASIF is the level of imagination and execution when it comes to visualizing data.  It's kind of an on-going master class. 
"When the melt ponds drain apparent compaction goes up because the satellite sees ice, not water in ponds." - FOoW

nanning

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Re: The 2020 melting season
« Reply #6223 on: September 21, 2020, 06:02:59 PM »
That's beautifully creative BornFromTheVoid. I like. A good one for next season for seeing the other minima crossed and the plume of course. Could go a bit slower for the last three weeks, but perhaps I'm too slow :).
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vox_mundi

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Re: The 2020 melting season
« Reply #6224 on: September 22, 2020, 02:25:35 AM »
Arctic Summer Sea Ice Second Lowest On Record: US Researchers
https://phys.org/news/2020-09-arctic-summer-sea-ice-lowest.html
https://nsidc.org/arcticseaicenews/2020/09/arctic-sea-ice-decline-stalls-out-at-second-lowest-minimum/

The year's minimum was reached on September 15, at 3.74 million square kilometers (1.44 million square miles), according to preliminary date from scientists at the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder.



https://nsidc.org/arcticseaicenews/2020/09/arctic-sea-ice-decline-stalls-out-at-second-lowest-minimum/
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uniquorn

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Re: The 2020 melting season
« Reply #6225 on: September 22, 2020, 02:12:06 PM »
Quote
Arctic sea ice decline stalls out at second lowest minimum

Strange title.

gerontocrat

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Re: The 2020 melting season
« Reply #6226 on: September 22, 2020, 03:55:54 PM »
NSIDC indulging in bad science?

And in that report for some unknown reason NSIDC decided to split the 42 years into 3 lots of 14 years. I show first what they've gone and done & then my rebuttal - which is basically that their analysis is arithmetically correct but not good science.

https://nsidc.org/arcticseaicenews/2020/09/arctic-sea-ice-decline-stalls-out-at-second-lowest-minimum/
Quote
The 42-minimum-extent values in the satellite record can be broken down into three 14-year periods. Most notably, minimum extents in the last 14 years of the time series are the lowest 14 in the 42-year record (Figure 2b). All three periods show a downward trend. The middle period, 1993 to 2006, shows the steepest downward trend of 13.3 percent per decade, relative to the 1981 to 2010 average. The earliest period, 1979 to 1992, has a downward trend of 6.4 percent per decade, while the most recent period of low extents, 2007 to 2020, has a downward trend of 4.0 percent per decade.

Quote
The overall, downward trend in the minimum extent from 1979 to 2020 is 13.4 percent per decade relative to the 1981 to 2010 average.
________________________________________________________________
My rebuttal

The last 14 year period starts in 2007. That year the minimum was well over 1 million km2 below trend, reflecting extremely favourable conditions for melt. Naturally this depresses the rate of decline in following years. I am reminded of a favourite trick of global warming denial was to use the very high global temperatures in 1997-98 arising from the super El Nino, and claim that as following years were cooler global warming was not happening. Cherry picking?

So I took my September monthly average graph from 1979 to 2020 (including my current estimate for the 2020), and added lines of the same data for 2007 to 2020, and one year earlier, 2006 to 2020.
- the R2 for 1979 to 2020 is a respectable 0.80,
- the  R2 for 2007 to 2020 is a pathetic 0.04. The R-squared value measures the proportion of variation in the dependent variable that can be attributed to the independent variable. In other words only 4% of the variation in the monthly average can be attributed to the year.

I then looked at what happens if one changes the start year of the last 14 year period by just one year - i.e. start in 2006 instead of 2007. The R2 for 2006 to 2020 is 0.16, 4 times greater than 0.04 but not exactly convincing. That one year change in start year also changes the average yearly extent loss from 23k to 50k, more than double. If a small data change can cause such a huge change in the result....?

[The graph for the last 14 year period published by NSIDC is, in my opimion, worse than meaningless - it is downright misleading. I won't be surprised to see it picked up by the denial industry.
_____________________________________________________
ps: I just couldn't be bothered to do the same work on the first two 14 year periods. Life's too short.

pps: Please shoot me down if you can. I don't really want to believe NSIDC could get it so wrong.
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BornFromTheVoid

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Re: The 2020 melting season
« Reply #6227 on: September 22, 2020, 04:17:11 PM »
NSIDC indulging in bad science?

And in that report for some unknown reason NSIDC decided to split the 42 years into 3 lots of 14 years.

It's not really an unknown reason though. The main point was highlighting how anomalous the minima have been since 2007 (14 years from then to 2020), which they have been. We haven't seen any minimum since 2007 equal or be above any minima pre-2007.

However, I agree that looking at the individual linear trends in those periods was pointless, for the reasons you highlight. If they had left them out and just focused on how low the post-2007 minima have been, it would have totally ok. But adding in the linear trends just seems arbitrary and open to misinterpretation.

It just comes across as a little rushed without considering the optics.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

gandul

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Re: The 2020 melting season
« Reply #6228 on: September 22, 2020, 04:53:26 PM »
NSIDC indulging in bad science?

And in that report for some unknown reason NSIDC decided to split the 42 years into 3 lots of 14 years. I show first what they've gone and done & then my rebuttal - which is basically that their analysis is arithmetically correct but not good science.

https://nsidc.org/arcticseaicenews/2020/09/arctic-sea-ice-decline-stalls-out-at-second-lowest-minimum/
Quote
The 42-minimum-extent values in the satellite record can be broken down into three 14-year periods. Most notably, minimum extents in the last 14 years of the time series are the lowest 14 in the 42-year record (Figure 2b). All three periods show a downward trend. The middle period, 1993 to 2006, shows the steepest downward trend of 13.3 percent per decade, relative to the 1981 to 2010 average. The earliest period, 1979 to 1992, has a downward trend of 6.4 percent per decade, while the most recent period of low extents, 2007 to 2020, has a downward trend of 4.0 percent per decade.

Quote
The overall, downward trend in the minimum extent from 1979 to 2020 is 13.4 percent per decade relative to the 1981 to 2010 average.
________________________________________________________________
My rebuttal

The last 14 year period starts in 2007. That year the minimum was well over 1 million km2 below trend, reflecting extremely favourable conditions for melt. Naturally this depresses the rate of decline in following years. I am reminded of a favourite trick of global warming denial was to use the very high global temperatures in 1997-98 arising from the super El Nino, and claim that as following years were cooler global warming was not happening. Cherry picking?

So I took my September monthly average graph from 1979 to 2020 (including my current estimate for the 2020), and added lines of the same data for 2007 to 2020, and one year earlier, 2006 to 2020.
- the R2 for 1979 to 2020 is a respectable 0.80,
- the  R2 for 2007 to 2020 is a pathetic 0.04. The R-squared value measures the proportion of variation in the dependent variable that can be attributed to the independent variable. In other words only 4% of the variation in the monthly average can be attributed to the year.

I then looked at what happens if one changes the start year of the last 14 year period by just one year - i.e. start in 2006 instead of 2007. The R2 for 2006 to 2020 is 0.16, 4 times greater than 0.04 but not exactly convincing. That one year change in start year also changes the average yearly extent loss from 23k to 50k, more than double. If a small data change can cause such a huge change in the result....?

[The graph for the last 14 year period published by NSIDC is, in my opimion, worse than meaningless - it is downright misleading. I won't be surprised to see it picked up by the denial industry.
_____________________________________________________
ps: I just couldn't be bothered to do the same work on the first two 14 year periods. Life's too short.

pps: Please shoot me down if you can. I don't really want to believe NSIDC could get it so wrong.

Clearly the splitting is subjective, but not completely arbitrary. The 2007 sinking after the 2000s gradual decline calls immediately to attention. That year there was a substantial and abrupt loss of old ice and volume as well.
The following years toward 2012 saw an exacerbation of loss of MYI. This is a real change of ice conditions that started in 2007 abruptly. As the NASA ice distribution shows, however, not much has changed in terms of multi year ice conditions since 2012. Ice extent has been around 4 mill. and the decline in volume and extent the 2010s has been notoriously reduced with respect to 2000s.
Personally I think climate warming is catching up with these 2007-2012 abrupt changes, and we’ll see a loss acceleration so that the 2020s keep pace with the gradual decline trend again.

Another abrupt change like 2007 is unpredictable.

Is this bad science from NSIDC? Well, it is sloppy if they don’t explain why they do the decomposition that they do. I explain above why it makes sense to me.

Tor Bejnar

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Re: The 2020 melting season
« Reply #6229 on: September 22, 2020, 06:47:47 PM »
I'm with Gerontocrat:  bad science. 

Cherry picking, even when done 'by chance', shouldn't be condoned.  They could have picked overlapping 16 year periods or two 21 year periods.   (Oh, but selecting 14 years gave 'good' results...)

If the dividing years were selected by doing a 'changepoint analysis' (something I don't know how to do, but I've read about on Tamino's WordPress blog), that would have put real science mathematics into the mix.  (The science would be discerning cause for the effect, something NSIDC didn't attempt.)

It may be frosting on the cake, Gero's showing the minimal mathematical significance of the last 14 year's data, when graphed alone.

How about 42 one-year periods, and an award for each being unique, and the best it could be?  ;D :o ::) :P :-\
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Freegrass

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Re: The 2020 melting season
« Reply #6230 on: September 22, 2020, 06:51:04 PM »
How is "melting" defined? When a storm destroys the ice, do we still call that melting? To me real melting means an input of energy into the system that raises the ocean temperature and makes the ice go away.

In 2012 the ice went away because of a storm. In 2020 the ice went away because of the input of solar energy.

There is a difference, no?

And 2020 was a year with a La Nina and a solar minimum. So now we wait for the next El Nino and solar maximum?
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Tor Bejnar

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Re: The 2020 melting season
« Reply #6231 on: September 22, 2020, 07:08:02 PM »
Melting is a change of state, not a change in temperature.  How the energy gets into the system to usher that change doesn't matter:  storm mixing warm water and ice, breezes shifting ice over warmed surface water or sunshine smiling down on ice and melt ponds.

I do wonder how much of the Beaufort's scorpion tail will melt before that sea is ice covered.  Some bottom melt can happen near surface freezing, I've been led to believe.  BFTV's GIFs are amazing!
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Richard Rathbone

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Re: The 2020 melting season
« Reply #6232 on: September 22, 2020, 08:56:51 PM »
NSIDC indulging in bad science?


This is the sort of thing Tamino shreds. Expect it to be shredded by him if it stays up for any length of time.

Its a typical denialist way of plotting the data.

The trendline should be continuous at the breakpoints, and the breakpoints should be chosen by statistical analysis rather than cherrypicked. (Why did they break it into 3 rather than 2 or 4? Its cherrypicked.)

They magic away about about 1/3 of the drop by the combination of not requiring continuity and cherrypicking the breakpoints.

binntho

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Re: The 2020 melting season
« Reply #6233 on: September 23, 2020, 07:09:07 AM »
As the NASA ice distribution shows, however, not much has changed in terms of multi year ice conditions since 2012. Ice extent has been around 4 mill. and the decline in volume and extent the 2010s has been notoriously reduced with respect to 2000s.

I would ask that you support these contentious claims with some proper analysis. I am unaware of there has been a reduction (notorious or otherwise) in the decline of volume and extent in the 2010s.

For extent, we can look at Gerontocrats 365 day average which clearly shows that the rate of decline is not slower in the 2010s than it was in the 20 year period before that. There are big swings, and the deep drop in 2008 stands out, but the general trend is clearly as close to a linear decline as makes no difference.



For volume, the graph below shows average monthly volume (from this excellent collection of graphs). Although a quick glance would seem to indicate changes in trend, particularly with the minima since 2010, the trendline (added by me, freehand) shows how unlikely it is that any putative slowdown were to be found to be statistically valid.
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binntho

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Re: The 2020 melting season
« Reply #6234 on: September 23, 2020, 07:27:18 AM »
How is "melting" defined? When a storm destroys the ice, do we still call that melting? To me real melting means an input of energy into the system that raises the ocean temperature and makes the ice go away.

There is only melting ... it is a phase change of water and requires a hell of a lot of energy. Which means that if a storm causes melt, it must have brought energy to the ice, both by itself (storms in northern latitudes tend to have higher air temperatures than surrounding air masses, and more latent heat in the form of rain and humidity) and by causing pre-existing heat in the ocean to come into contact with the ice.

The oceans are getting warmer because of AGW, and this increase in global ocean temperatures is perhaps the main driver behind the steady decline of Arctic sea ice. The vagaries of weather cause annual fluctuation while the underlying near-linear trend is probably underpinned by increased global ocean temperatures. Since the rate of warming has been increasing, the rate of ice loss should presumably also be increasing, but I suspect that this change is happening too slowly to be apparent in our limited data series so far.

Local positive feedback is presumably also a contributing cause to the underlying trend. Increased ocean surface during melting season is a strong positive feedback that should be increasing the underlying rate of melt. Continental amplification during summer is probably also on the increase - the rate of summer warming in Siberia is significantly larger than global warming generally.

All of these factors should be causing an increase in the underlying rate of melt in the Arctic, and I suspect that this is what is really happening. The variations in weather and the annual swings arund the trend may be hiding this, and the increase in the rate of decline may well be too slow at this time to show up in our limited data sets.

But any talk of "slow down" is pure speculation, and not supported by the data nor by the physics of the system.
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Re: The 2020 melting season
« Reply #6235 on: September 23, 2020, 09:06:29 AM »
pps: Please shoot me down if you can. I don't really want to believe NSIDC could get it so wrong.
Is it really bad science or just bad politics?

In a better world, say one without politically motivated science denialism, it would make sense to look at Arctic post-2007 as a separate timeline.

But in the fact-challenged mess we live in this will fuel the denialist camp with another faux hiatus.

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Re: The 2020 melting season
« Reply #6236 on: September 23, 2020, 06:39:44 PM »
pps: Please shoot me down if you can. I don't really want to believe NSIDC could get it so wrong.
Is it really bad science or just bad politics?

In a better world, say one without politically motivated science denialism, it would make sense to look at Arctic post-2007 as a separate timeline.

But in the fact-challenged mess we live in this will fuel the denialist camp with another faux hiatus.
I agree

gandul

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Re: The 2020 melting season
« Reply #6237 on: September 23, 2020, 06:43:51 PM »
As the NASA ice distribution shows, however, not much has changed in terms of multi year ice conditions since 2012. Ice extent has been around 4 mill. and the decline in volume and extent the 2010s has been notoriously reduced with respect to 2000s.

I would ask that you support these contentious claims with some proper analysis. I am unaware of there has been a reduction (notorious or otherwise) in the decline of volume and extent in the 2010s.

For extent, we can look at Gerontocrats 365 day average which clearly shows that the rate of decline is not slower in the 2010s than it was in the 20 year period before that. There are big swings, and the deep drop in 2008 stands out, but the general trend is clearly as close to a linear decline as makes no difference.



For volume, the graph below shows average monthly volume (from this excellent collection of graphs). Although a quick glance would seem to indicate changes in trend, particularly with the minima since 2010, the trendline (added by me, freehand) shows how unlikely it is that any putative slowdown were to be found to be statistically valid.
I was talking about the minima, but doesn’t matter, it is a sterile discussion in any case.

I find interesting nonetheless how people get triggered with this.

Looking back at the article, it would be just an innocent equidistant 14-year decomposition of the trend with a somehow surprising result, all innocent if, as bluice says, it wouldn’t give arguments to denialism, and I would add if it wouldn’t easily trigger insufferable alarmists.

I have seen in the past alarmists making wilder claims based in much less than 14 years (remember the projections in the wake of 2012? No matter linear, exp, or ther fit the end was somewhere before 2016)
(And those plots with “YOU ARE HERE!!” very dramatically written... well now we are there, little drop in the minimum since 2012, in fact, negative)
« Last Edit: September 23, 2020, 06:57:20 PM by gandul »

OffTheGrid

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Re: The 2020 melting season
« Reply #6238 on: September 24, 2020, 12:19:30 AM »
For pitys sake! Can someone here with a pixel counter run it over Hycom seaice thickness charts, so we can get an unpoliticised best available actual estimate on volume trends? And currently very obviously the lowest ever minimum that we are approaching?
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Richard Rathbone

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Re: The 2020 melting season
« Reply #6239 on: September 24, 2020, 12:41:50 AM »


Looking back at the article, it would be just an innocent equidistant 14-year decomposition of the trend with a somehow surprising result, all innocent if, as bluice says, it wouldn’t give arguments to denialism, and I would add if it wouldn’t easily trigger insufferable alarmists.


Its not innocent, because its not a 14-year decomposition. Its a 14-year decomposition with two episodes of alien abduction and the episodes of alien abduction account for about a quarter of ice loss. There's also no particular reason to choose 14 year periods, other than the size of the alien abduction it allows to be hidden.

This type of misrepresenting the scale of climate change by cherry picking the period chosen to split the data to include large episodes of alien abduction at either end of it is a common in denialist circles.

Its shockingly bad science. Laws of conservation are extremely basic principles and this analysis breaches them in a major way.

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Re: The 2020 melting season
« Reply #6240 on: September 24, 2020, 02:40:12 AM »
Indeed, 1992 to 1993 and 2006 to 2007 missing from the fancy analysis. Very bad science.

Freegrass

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Re: The 2020 melting season
« Reply #6241 on: September 24, 2020, 04:19:01 AM »
How is "melting" defined? When a storm destroys the ice, do we still call that melting? To me real melting means an input of energy into the system that raises the ocean temperature and makes the ice go away.

There is only melting ... it is a phase change of water and requires a hell of a lot of energy. Which means that if a storm causes melt, it must have brought energy to the ice, both by itself (storms in northern latitudes tend to have higher air temperatures than surrounding air masses, and more latent heat in the form of rain and humidity) and by causing pre-existing heat in the ocean to come into contact with the ice.

The oceans are getting warmer because of AGW, and this increase in global ocean temperatures is perhaps the main driver behind the steady decline of Arctic sea ice. The vagaries of weather cause annual fluctuation while the underlying near-linear trend is probably underpinned by increased global ocean temperatures. Since the rate of warming has been increasing, the rate of ice loss should presumably also be increasing, but I suspect that this change is happening too slowly to be apparent in our limited data series so far.

Local positive feedback is presumably also a contributing cause to the underlying trend. Increased ocean surface during melting season is a strong positive feedback that should be increasing the underlying rate of melt. Continental amplification during summer is probably also on the increase - the rate of summer warming in Siberia is significantly larger than global warming generally.

All of these factors should be causing an increase in the underlying rate of melt in the Arctic, and I suspect that this is what is really happening. The variations in weather and the annual swings arund the trend may be hiding this, and the increase in the rate of decline may well be too slow at this time to show up in our limited data sets.

But any talk of "slow down" is pure speculation, and not supported by the data nor by the physics of the system.
After I wrote that message I realized that this would bring us back to our discussion at the start of the season; What adds more energy to system? Storms, or insolation? So it's good you wrote that.

But do you understand what I'm trying to say?

If you take a glass of (salt) water and you put an ice cube into it, the ice will melt, but the meltwater will not mix with the bottom layer very quickly. But if you crush that ice and stir up the water (simulating an ice crushing storm) the temperature of the water in the entire glass will drop rapidly.

So when a storm breaks up the ice and mixes the water, the ice will melt. But you're not adding as much energy into it as when you would put that glass under a lamp.

I know I'm still trying to say things you keep discrediting, but I do hope there's someone out there that understands what I mean.  :-\

It's all about adding energy to the system, and so we're back to our debate from old; What adds more energy to the system? A storm, or the sun?

I'm stubborn thinking it must be insolation, but I understand your argument now that storms add a lot of energy to the system as well. And storms do open up the ocean so that the heat from the sun can more easily be added to the system...

I guess I'll never figure this one out completely...   :-[

Edit: and then there's also the heat already present in the deeper layers of the arctic ocean that storms bring to the surface. So that's a double whammy...

Ok... You win!  ;D
« Last Edit: September 24, 2020, 04:26:39 AM by Freegrass »
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binntho

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Re: The 2020 melting season
« Reply #6242 on: September 24, 2020, 06:33:07 AM »
After I wrote that message I realized that this would bring us back to our discussion at the start of the season; What adds more energy to system? Storms, or insolation? So it's good you wrote that.
...
It's all about adding energy to the system, and so we're back to our debate from old; What adds more energy to the system? A storm, or the sun?

I'm stubborn thinking it must be insolation, but I understand your argument now that storms add a lot of energy to the system as well. And storms do open up the ocean so that the heat from the sun can more easily be added to the system...

Indeed, it is a rehashing of an old haggis. And I seem to remember that both of us, and with Oren weighing in as well, came to the shared conclusion that insolation is the main cause of heat entering the system during peak insolation.

And we both agree that a storm causes mixing and thus brings heat from the ocean to bear on the ice.

But what seems to be missing from your reasoning is the fact that a typical storm is also a bringer and conveyor of warmth in and of itself. This is something that is obvious to those living in coastal areas in along the North Atlantic, Scotland, Iceland and Norway.

Outside of the short months of summer, a storm always has higher air temperatures than before or after. A typical late autumn or early spring storm in Iceland is easily 10 degrees centigrade, with heavy rain. I've even experienced storms like that in the middle of winter.  And there are periods where the storms come one after another, three or four in a week. And it is always colder between storms than during a storm except during high summer.

So back to the Arctic - I'd suggest that during June and July, storms would bring less energy to bear on the ice than insolation. During August, September and even further into the Autum, cyclones coming in from open water will transfer quite a lot of energy to the ice, while insolation is rapidly dropping down to nothing. During late spring, before insolation picks up, the same shold apply.

But we must not forget the third vector of energy infusion - ocean heat. And I would suggest that it is dwarves the others - but is at the same time inefficient in a melting contexts, since most of the heat does not reach the ice.

So can we rank these vectors and their interplay when it comes to melting ice? Even if Insolation would seem to be the favorite, we must remember that it still accounts for only around half the melt (simply because so much of a melting season happens outside of peak insolation).

Most of the rest I suppose is caused by ocean heat. And this is where storms kick in - they act both to give mechanical force to the system, mixing waters and moving the ice, and thus enabling the ocean heat to interact more efficiently with the ice. And secondly, the increased air temperatures and moisture that a storm carries in over the ice has it's origins in that same ocean heat.

So I'd suggest that insolation and ocean heat are the two main drivers of melt each year, with storms playing an important part in bringing the latter to bear on the ice, thus increasing melt at all times other than the during peak insolation.

And that storms can inhibit melt only during peak insolation, but will enhance melt during all other times.
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binntho

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Re: The 2020 melting season
« Reply #6243 on: September 24, 2020, 06:42:39 AM »
I was talking about the minima, but doesn’t matter, it is a sterile discussion in any case.

I find interesting nonetheless how people get triggered with this.
...
little drop in the minimum since 2012, in fact, negative)

That's the way of the world, I fear: seemingly false claims do have the potential to "trigger" people.

This focus on the minima is a bit like somebody claiming that the world is not waming up because the temperature record of 1913 (56.7 C) has not yeat been matched.

The reality of course is different. And to repeat: Neither the data nor the physics support any claim about a stall in melt or ice reduction in the 2010s.
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Re: The 2020 melting season
« Reply #6244 on: September 24, 2020, 08:59:16 AM »
also it must be said that, year after year the exent and the volume decrease
A conséquence of that is the variability in km2 (or other unit of measurement) which is in proportion to the net area of ​​the extent (oi of the physical quantity measured) also decreases
this may be gives the impression that the size of the melt is decreasing a bit, yet trends show that this is wrong.
Sorry, excuse my bad english

Freegrass

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Re: The 2020 melting season
« Reply #6245 on: September 24, 2020, 02:27:21 PM »
After I wrote that message I realized that this would bring us back to our discussion at the start of the season; What adds more energy to system? Storms, or insolation? So it's good you wrote that.
...
It's all about adding energy to the system, and so we're back to our debate from old; What adds more energy to the system? A storm, or the sun?

I'm stubborn thinking it must be insolation, but I understand your argument now that storms add a lot of energy to the system as well. And storms do open up the ocean so that the heat from the sun can more easily be added to the system...

Indeed, it is a rehashing of an old haggis. And I seem to remember that both of us, and with Oren weighing in as well, came to the shared conclusion that insolation is the main cause of heat entering the system during peak insolation.

And we both agree that a storm causes mixing and thus brings heat from the ocean to bear on the ice.

But what seems to be missing from your reasoning is the fact that a typical storm is also a bringer and conveyor of warmth in and of itself. This is something that is obvious to those living in coastal areas in along the North Atlantic, Scotland, Iceland and Norway.

Outside of the short months of summer, a storm always has higher air temperatures than before or after. A typical late autumn or early spring storm in Iceland is easily 10 degrees centigrade, with heavy rain. I've even experienced storms like that in the middle of winter.  And there are periods where the storms come one after another, three or four in a week. And it is always colder between storms than during a storm except during high summer.

So back to the Arctic - I'd suggest that during June and July, storms would bring less energy to bear on the ice than insolation. During August, September and even further into the Autum, cyclones coming in from open water will transfer quite a lot of energy to the ice, while insolation is rapidly dropping down to nothing. During late spring, before insolation picks up, the same shold apply.

But we must not forget the third vector of energy infusion - ocean heat. And I would suggest that it is dwarves the others - but is at the same time inefficient in a melting contexts, since most of the heat does not reach the ice.

So can we rank these vectors and their interplay when it comes to melting ice? Even if Insolation would seem to be the favorite, we must remember that it still accounts for only around half the melt (simply because so much of a melting season happens outside of peak insolation).

Most of the rest I suppose is caused by ocean heat. And this is where storms kick in - they act both to give mechanical force to the system, mixing waters and moving the ice, and thus enabling the ocean heat to interact more efficiently with the ice. And secondly, the increased air temperatures and moisture that a storm carries in over the ice has it's origins in that same ocean heat.

So I'd suggest that insolation and ocean heat are the two main drivers of melt each year, with storms playing an important part in bringing the latter to bear on the ice, thus increasing melt at all times other than the during peak insolation.

And that storms can inhibit melt only during peak insolation, but will enhance melt during all other times.
You completely nailed it with this one Binntho! This post should be article one of the arctic bible...

Storms at peak insolation block out the sun. Storms outside of peak insolation bring in heat and act as a warming blanket that prevent the heat from escaping.

One comment though. Insolation should always be put in first place. Because all that ocean heat is coming from the sun. Either directly in the arctic, or from more southern latitudes and brought in by ocean currents. Without the sun, we would have a snowball earth.

And so we end this season with the same discussion as we started it. With the difference that I finally get it now...  ;D

Many thanks to everyone on this forum for an educational season!  :)

PS: I actually wrote a much better post, but it sadly got lost again and I had to rewrite it... I so hate it when that happens...  :'(
« Last Edit: September 24, 2020, 02:40:48 PM by Freegrass »
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Glen Koehler

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Re: The 2020 melting season
« Reply #6246 on: September 24, 2020, 10:07:35 PM »
<snippage>
But we must not forget the third vector of energy infusion - ocean heat. And I would suggest that it is dwarves the others - but is at the same time inefficient in a melting contexts, since most of the heat does not reach the ice.

So can we rank these vectors and their interplay when it comes to melting ice? Even if Insolation would seem to be the favorite, we must remember that it still accounts for only around half the melt (simply because so much of a melting season happens outside of peak insolation).

Most of the rest I suppose is caused by ocean heat. And this is where storms kick in - they act both to give mechanical force to the system, mixing waters and moving the ice, and thus enabling the ocean heat to interact more efficiently with the ice. And secondly, the increased air temperatures and moisture that a storm carries in over the ice has it's origins in that same ocean heat.

So I'd suggest that insolation and ocean heat are the two main drivers of melt each year, with storms playing an important part in bringing the latter to bear on the ice, thus increasing melt at all times other than the during peak insolation.
   The Atlantification paper posted about a week ago stated that in the Laptev Sea study area ocean heat diffusion from incoming warm Atlantic water (now exacerbated by thinning of the cold halocline and increased turbulence), was equal to atmospheric warming as a cause for ice melt.  The ASI is getting hit from all sides.

   Edit -- Found the article:  https://journals.ametsoc.org/jcli/article/33/18/8107/353233/Weakening-of-Cold-Halocline-Layer-Exposes-Sea-Ice
« Last Edit: September 25, 2020, 04:00:01 AM by Glen Koehler »

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Re: The 2020 melting season
« Reply #6248 on: September 24, 2020, 10:24:12 PM »
Thanks Vox.  ;D A week ago turns into > a month ago pretty fast these days.

Tor Bejnar

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Re: The 2020 melting season
« Reply #6249 on: September 26, 2020, 08:52:14 PM »
The final 2020 extent graphic from Jim Petit: (A click will enlarge, but go to the on-line image to see it better.)

(Other data presentations will continue, I'm sure.)
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