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Messages - wdmn

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1
Thank you Oren and The Walrus,

@The Walrus
Yes, the graphs show a peak in the period you had pointed out. During our earlier conversation I expected ice levels to be slightly lower prior to that based on the temperature data I had already processed, and the global surface temperature record.

However, I have since added another data set to my modelling (from Houghton, Michigan). The data set was missing 4 years, but still produced a strong predictive relationship to AAIC for temperatures reaching -17.78C (0F) or below when this count was summed with other stations.

So, I was able to model the years 1962-1972 with this new relationship (r2 = 0.8909; Black on Fig 8 below), and the years 1950-1961 with a relationship between Duluth, SSMUS and Houghton (r2 = 0.8697; Purple on fig. 8 below). Fig 8 (the first one below) shows these new models along with the ones provided in the previous graph of AAIC (Fig 5 above).

The average of these models (Fig 9 below) shows a less dramatic change between the late 30s until the late 50s and the subsequent period. This is also reflected in the average of the models for maximum extent (Fig 10 below).

As for the post 2012 period, it is so short, and includes what is clearly an extremely exeptional year in 2014 (compare the AAIC for this year with the rest of the data set to see how exceptional it is), that I am hesitant to say that the "pause" in the trend is anything more than short term noise. Unfortunately, only time will tell.

2
This is the second of two posts.

Fig 5 Shows Annual Average Ice Cover (AAIC) for Lake Superior from 1973-2020 (Yellow) and several back projections of AAIC.

The first back projection (Green: 1962-1972) was made using the actual data from all three weather stations, since all three went back to at least 1962. R2 for model = 0.8927.

The second back projection (Red: 1949-1961) was made using the actual data from Duluth and SSM, Michigan. R2 = 0.8676

The third back projection (Orange: 1949-1961) was made using the same model used for the first (green) projection, by combining the data from Duluth and SSM, Michigan, with a projected count of extreme days in SSM, Canada (using the relationship shown in Fig 4, above; R2 = 0.8842).

Finally, a back projection (Blue) was made fro the period 1932-1972 using the actual count from SSM, Michigan, combined with the projected count for SSM, Canada. This was done through 1972, so that the period of 1962-1972 could be compared between the strongest model (Green) and the one with the most extrapolation (Blue).

Fig. 6 Shows a the maximum extent of ice cover on Lake Superior (Yellow: 1973-2020), and several back projections of maximum extent from 1932-1972 based on the projections of AAIC outlined above. The relationship between AAIC and max extent is given in Fig. 3, above.

The colours are the same as those on Fig 5.

The data suggests that while Lake Superior experienced somewhat lower ice levels from the late 30s until the late 50s, compared to the period from 1959-1980 (a pattern reflective of the global mean surface temperature anomaly; Fig 7), the general trend has been of a decline in both area covered, and maximum extent. With the exception of 1932 (known as the year without a winter), a notable decline in minima for both AAIC and max extent can be observed beginning in the 1980s, and particularly after the 1998 "super" el nino. Also of note is the increased inter annual variability, especially notable in the maximum extent data over this same period.

Whether these models have any value, or could be improved upon is an open question, but I found them to be interesting enough to be worth sharing. I hope that some of the readers of this forum agree.

3
The following is the first of two posts, due to the large number of images.


Satellite records for Great Lakes ice cover only go back to the winter of 1972-1973 (referred to as 1973).

There are two annual measurements for each of the five Great Lakes plus Lake St. Clair for this time period. One is the maximum ice extent reached during the season in percentage of lake cover, and the other is average annual ice cover (AAIC), which is calculated by averaging the extent recorded on each day of the freezing season.

Living near Lake Superior, I took some interest in both temperature records for the area, and the ice data for the late.

Looking at the data, I found that extreme minimum temperatures between Dec. 1 and March 31st from some weather stations (Sault Ste Marie Canada (-20C or lower), Sault Ste Marie, Michigan (-17.78C or lower), and Duluth, Minnesota (-20C or lower)) around Lake Superior gave a very strong correlation with AAIC (0.899085 SSM Canada; 0.8670059 Duluth; 0.9098268 SSM Michigan), and that summing these figures across stations produced an even stronger correlation (Fig 1, correlation = 0.9287145). (Unfortunately, due to incomplete data sets I could not look at other weather stations around the lake).

An ad-hoc mathematical relationship was found between the count of these extreme cold days and AAIC for each weather station, and was again strongest when the counts for all three were summed (Fig. 2, r2 = 0.8927). This relationship allowed for some predictive power during the freezing season (by using two week forecasts, for example), which was of use due to an interest in having forewarning of the possibility of ice bridges forming to some of the large off-shore islands on the lake. The latter being possible because AAIC has a high predictive power for max ice extent (Fig 3, r2 = 0.9358), and max ice extent is a good predictor of years when ice bridges formed.

The temperature data for Duluth went back as far as 1949, SSM Canada to 1962, and SSM Michigan to 1932. Because of strong relationships between extreme cold days and AAIC, and AAIC and max extent, as well as the the count of days reaching -17.78C or below in SSM Michigan, and the count of days reaching -20C or bellow in SSM Canada (Fig 4), I have been able to create some back projections of both AAIC and max extent extending to 1932, which I will share in the following post.

4
Arctic sea ice / Re: The 2020 melting season
« on: September 15, 2020, 06:40:51 PM »
Odd things going on on the Central Arctic Sea....
It's not odd that concentration is going up, as it does every year. Refreeze has begun a few days ago in several regions in the heart of the pack, nearly eliminating surrounded open water pixels. The odd thing is that extent - and even area - are still shrinking despite this, due to melting at the edges. Not for long, but already an oddity.

This is a bit of a lazy post because I don't have the tools to do the analysis at the moment. But I wonder if this is partially to do with the ice edge being over deep water because of the low extent, but also the relative "compactness" of the ice pack compared to say 2016, where low concentration ice was scattered over shallower waters. At this time of year, the refreeze can start at higher air temperatures than would otherwise be required to make ice over open water, because of adjacent ice, but over deep water (especially water that has high SSTAs) even this process would be slowed somewhat... i.e hypothesis: air temperatures will have to fall lower than usual before ice can begin growing on the ice edge, due to much of the ice edge being over unusually deep waters.

5
Arctic sea ice / When will 2020 JAXA extent cross 2012?
« on: September 15, 2020, 03:19:39 AM »
How fast will refreeze start this year? When will JAXA extent for 2020 cross with 2012?


6
The rest / Re: The off topic off topic thread
« on: September 13, 2020, 10:47:53 PM »
To anyone who would like to think with more complexity than, "one culture and one time period are to blame for everything, and that culture is unnatural," I suggest the book "A Short History of Progress by Ronald Wright.

https://en.wikipedia.org/wiki/A_Short_History_of_Progress

"A Short History of Progress is a non-fiction book and lecture series by Ronald Wright about societal collapse. The lectures were delivered as a series of five speeches, each taking place in different cities across Canada as part of the 2004 Massey Lectures which were broadcast on the CBC Radio program, Ideas...

Wright... uses the fallen civilisations of Easter Island, Sumer, Rome, and Maya, as well as examples from the Stone Age, to see what conditions led to the downfall of those societies. He examines the meaning of progress and its implications for civilizations—past and present—arguing that the twentieth century was a time of runaway growth in human population, consumption, and technology that has now placed an unsustainable burden on all natural systems."

7
Science / Re: Where are we now in CO2e , which pathway are we on?
« on: September 12, 2020, 11:19:00 PM »
@Stephen

My apologies.

The graph comes from: https://twitter.com/alxrdk/status/1295016785180270594

The time period (x-axis) is 12,000 years, 9980 BC - 2020 AD.
Baseline is 20th century mean. Minimum temperature shown = -1.37°C, Max T = 0.99°C (2020).

Sources for the data are provided in the above linked twitter thread.

The graph shows the end of the last glacial period, the Holocene and the Anthropocene (if you are so inclined to use the latter designation). The Holocene is the period in which agriculture and settled human civilization was born. Humans of course lived during the last glacial period, but were not present in large parts of currently inhabited land, as that land was under thick ice sheets.

I used this graph, because it very clearly shows the slow arc down from the Holocene maximum temperature. That arc had us on the trajectory to another glacial period, which would be -- one could argue -- at least as devastating to human civilization as global heating now threatens to be.

@wili

I of course agree that we are in a dire situation regarding climate change, as is unanimously stated by the most reputable climate scientists. The 350 ppm target was set by one of those same scientists, James Hansen.

While the consequences of industrialization are now threatening human civilization, I think it is ridiculous to dismiss the whole period as a cancer that should be done away with. I simply want to point out that the pre-industrial target would also condemn human civilization.

I also question the 280ppm target as arbitrary; it already includes human activity throughout the Holocene, so why is that "nature's track" as it was intended?. Why not "put it back as it was" before the Holocene? Before humans? What is "undoing the harm?" What is nature's track, if not the one that we're on? That of course includes the possibility that we address global heating before it does as much damage as it might (i.e. that we might completely overhaul our culture, including learning from those non-industrialized cultures that still exist).

Nanning's logic -- as has been discussed elsewhere ad nauseam -- presumes that humans have no right to take actions that affect nature's path, while at the same time declaring that we should make a decision to go back to one specific point in nature's path (i.e. making the human decision as to what nature's path should be; i.e. doing the same thing he condemns when we set the target at 350 ppm). He also seems to condemn human beings to either being passive animals that accept whatever fate is handed to us by "nature" (we should allow a glacial period or an astroid to hit us, even if we could avoid it, for example; which condemns nature for giving us a survival instinct and the ability to practice climate science or astronomy, etc.), or to eliminate us completely from nature (which, as pointed out, condemns nature, which gave rise to our species).

8
Consequences / Re: Hurricane Season 2020
« on: September 12, 2020, 07:40:15 PM »
HRWF now forecasting possible cat 3/4 at landfall...

https://twitter.com/climateguyw/status/1304834379273981952

9
Science / Re: Where are we now in CO2e , which pathway are we on?
« on: September 12, 2020, 07:35:37 PM »
280 ppm is the pre-industrial level. Reaching that means returning to nature's original track. That should be the goal. To undo the damage we've done.

Back on this old nonsense eh nanning? It would have been better had humans never evolved! But then that would mean blaming... nature?

At 280ppm we were heading into a glacial period.

10
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: September 08, 2020, 05:21:10 PM »
Back up now...

Sept. 7th: 3.834

11
Consequences / Re: Arctic Amplification and Extreme Weather
« on: September 05, 2020, 05:18:42 PM »
I'm very interested in the "cool" Spring signal in North America. Is it just noise?

In any case, it's a hurdle for educating people on climate change. People here around the Great Lakes notice it when Spring starts late, or when we get old style extremely cold winters.

12
Some related data, which further confirms the overall warming trend's impact on ice around the Great Lakes, can be found in the table below (taken from the paper Historical Trends in Lake and River Ice Cover in the Northern Hemisphere, Magnuson et al, 2000).

Table shows statistically significant changes in freeze, and break-up date for many areas around the Great Lakes (look for Michigan, Minnesota, NY, Wisconsin or Ontario).

13
1) You are right that it was a minor reference, and I wish the article had been more robust; however, what is stated is that, "overall [the shipping records show] a clear signal of human-caused warming since the industrial revolution." Which, as you agree in your second point, would mean also a sign of declining ice cover.

2) Yes, this is true (I will have more on the topic soon). There is no disagreement here, and this seems only to reaffirm my point. It would be cherry picking to say this supported your argument that max ice cover "peaked in the 1970s," because we know there was a c.1930-1954 warm period in the temperature record. Rather, if we're comfortable making that claim, we should be comfortable to say that it peaked in the pre-industrial, early industrial period; i.e. the long term trend -- even outside of the satellite record -- is one of decline.

3) This seems like more cherry picking given what you've already admitted. But, the article also talks about certain lakes having less clear trends, due to shallow waters, etc. If we take, for example, Lake Superior (see below), the last 38 years do indeed show a clear trend, even if the R value is low due to lots of inter-annual variability.

You've done almost the exact same thing as those who were claiming there was a "hiatus" in warming, and you seem to concede (as the evidence clearly shows), that the long term trend has been of decline.

As I stated previously, I do think it is remarkable -- and I wish more discussed in an approachable way -- that we've had some extremely cold winters around the Great Lakes in recent years. However, the minima in max extent continue to be "post-1998" level (and, there are many more years reaching below 30% cover than in the period prior), showing that the system has indeed changed. The inter-annual variability has gone up, and the system seems to be oscillating. If you have good reason to believe that when it settles, lake ice will continue to grow, I would really love to hear your case. I tend to believe -- along with most scientists -- that within the next 30 years, we will see lake ice on the Great Lakes mostly disappear.

Now imagine we had not had this exchange and your original post (that I took issue with) was the last and only word. Can you see all that would have been left out, and how that might be misleading to the casual reader... how it might actually even feed a narrative of climate change denial?

14
Arctic sea ice / Re: The 2020 melting season
« on: September 04, 2020, 05:43:28 AM »
[ADS NIPR VISHOP (JAXA)] Arctic Sea Ice Extent.

September 3rd, 2020:

Our service will be stopped from Sep. 4th 12:00 JST  to 7th 12:00 JST by planned electrical  outage for legal inspection.
We sincerely apologize for inconveniencing you for a long time.

https://twitter.com/ADS_NIPR/status/1300656613674463232?s=20

This is cruel and unusual punishment...

15
The reason it is not more precise to say that it reached a maximum in the 70s is because the data set starts in the 70s. Wording it that way makes it sound like there's a cycle of increasing and decreasing max ice cover (and we are currently increasing again), when we in fact know the long term trend has been one of decline.

Also, 2019 was a low max extent year, which your graph doesn't capture.

In addition, average annual ice cover (AAIC; amount of ice on the lakes each day during freezing season averaged over the whole season) has been lower during recent maxima than at times of comparably high maxima pre-1998; that is to say, the maximum extent lasts less time. Other than 2014-2015 the freezing seasons are getting shorter and less severe.
Without data from before 1975, we cannot make scientific claims about the maximum ice coverage prior to then.  Again, the max ice is less and the freezing season is shorter than pre-1998.  Since then, the max ice is more and the freezing season is longer. 

How can we be certain that the long term trend is one of decline, if the past two decades is one of increase?

There are a few ways to answer your superficially rigorous questioning.

1) Non-scientific measurements/anecdotal evidence: Did you read the Nat Geo article? They refer to shipping records which talk of break up and start of season, which do not give us max ice cover, but provide some information on Great Lakes ice.

2) Related information about the physical system and accepted physics: We know that the climate has been warming, including around the Great Lakes (as the Nat Geo article also states), and so we have good reason -- i.e. temperature records and physics -- to believe that ice cover was not lower prior to the 1970s than it is now. Nor do we have reason to believe that max ice would have been significantly higher in the 70s than the 1900-1970 period.

3) Meaning of "long term trend" in the satellite records: Finally, in lieu of other satellite data the long term trend is from 1973-2020. And the trend is one of decline in maximum cover.

It is certainly interesting that there have been some very harsh winters in the 2010s, but without some contextualization your graph and the wording of your post are misleading, as I stated in my previous post.

16
The reason it is not more precise to say that it reached a maximum in the 70s is because the data set starts in the 70s. Wording it that way makes it sound like there's a cycle of increasing and decreasing max ice cover (and we are currently increasing again), when we in fact know the long term trend has been one of decline.

Also, 2019 was a low max extent year, which your graph doesn't capture (called 2020 in the below annual graph).

In addition, average annual ice cover (AAIC; amount of ice on the lakes each day during freezing season averaged over the whole season) has been lower during recent maxima than at times of comparably high maxima pre-1998; that is to say, the maximum extent lasts less time. Other than 2014-2015 the freezing seasons are getting shorter and less severe.

17
The 09.2020 issue of National Geographic has an excellent article on the impact of the shrinking winter on the Great Lakes area starting on page 74.

According to the graph on page 85, the maximum ice coverage on the Great Lakes has  increased 10% over the past 25 years.  Indeed, the maximum ice coverage reached a maximum in the late 70s, dropped until ~2005, and has been rising since.

This is slightly misleading. There was a deep trough (in terms of max cover) from 1998-2003, but the 2003-2019 trend for max cover is much lower than the period between 1973-1998 (lower minima, and less frequent maxima).

18
This may have been posted before, but thought it would be of interest (in spite of its age).

The image compares multiple records of ice break in rivers, bays and lakes, and plots them in terms of rate of melt based on ice thickness (y axis) and duration of melt (in days; x axis). It then plots hypothesied minimum and maximum melt rates, where the maximum rate has lots of movement in the water (wind, waves, currents), and the minimum is based solely on increasing air temperatures.

The image comes from the paper:

CORRELATING FREEZE-UP AND BREAK-UP WITH WEATHER CONDITIONS by G. P. Williams, 1965.

https://www.nrcresearchpress.com/doi/pdfplus/10.1139/t65-047

19
Consequences / Re: Hurricane Season 2020
« on: August 27, 2020, 04:11:43 AM »
Tropical Storm Hanna looks like it's going to pull a rapid escalation to hurricane status before making landfall in Texas. The advisory this morning (as well as all previous) still had it making landfall as a tropical storm. Seems like the models are still having trouble with the sometimes explosive development of these storms.

https://www.nhc.noaa.gov/graphics_at3.shtml?start#contents

Models continue having problems over high SST anomaly waters.

20
Arctic sea ice / Re: The 2020 melting season
« on: August 22, 2020, 06:52:29 PM »
It's worth noting that, after another large drop in NSIDC area, compaction remains at record low for the date, and significantly lower than 2012. Surely those who were adamant in late July that this year could well finish behind 2019 are now ready to revise their outlooks?


21
Consequences / Re: Global Surface Air Temperatures
« on: August 15, 2020, 05:34:45 PM »
Thanks for the false balance Hefaistos, it's certainly needed given the sensationalism of my statement that the 60mo running mean was soaring and would continue to soar and never come down again at all with la nina's or annual variability, and my unwillingness to provide a link to further discussion by Hansen, and my general incitement to PANIC!

22
Consequences / Re: Global Surface Air Temperatures
« on: August 14, 2020, 05:56:11 PM »
James Hansen posted a graph updating global temperature anomaly through July 2020 with a 60 month (5 year) running mean that is truly frightening.

https://twitter.com/DrJamesEHansen/status/1294288845664641025

23
Thanks Blumenkraft,

I have seen that graph. I'm just wondering how to start thinking about kJ/kg in terms of temperature that is not instantaneous (I assume all of those kJ need not be available at the same instant in order for melt to occur, since it occurs over time)...

24
I'm trying to conceptualize a seemingly simple problem about freezing physics. My goal is to determine air temperatures at which ice forms rapidly on the surface (assuming no waves/little wind). After some thought I have decided I have to first think in terms of melting physics.

If we have the enthalpy of fusion for ice at:

333.55 J/g (heat of fusion of ice) = 333.55 kJ/kg = 333.55 kJ for 1 kg of ice to melt

If we want to simplify this and understand melting potential just from the watts/m2 from insolation + air temperature (assuming the latter is possible), we could calculate roughly 1 kg of ice into m2 (for a given thickness). This then becomes a question of thermal conductivity between air/insolation in W/m2 and ice in m2.

In order to think about freezing, I reverse and further simplifying this problem, by first eliminating insolation as a factor (ice often forms at night in lower latitudes and in the arctic insolation is not a factor for most of freezing season), and just getting a watts/m2 value from water at 4, 3, 2 and 1 degree celsius (how, I don't know), and imagining this as an energy source trying to heat the surrounding air, and then calculating at what air temperature ice rapidly forms due to the heat source in the water no longer being able to keep air temperature at the surface of the water above freezing.

I'm wondering if I am even approaching it right in wanting to think about W/m2 between two surfaces (the surface of the water, and the surface of the adjacent air, where both temperatures could be known), treating it as the water heating the air, rather than the air cooling the water. Obviously it would be better to have a W/m3 measure, but maybe m2 is simpler for now...

Any general advice to sort out my thinking would be much appreciated.

25
Arctic sea ice / Re: The 2020 melting season
« on: August 09, 2020, 01:43:31 PM »
There was some curiosity about the sea ice holding out near SZ.  Here is the middle of the ice pack just south and west of October Revolution Island.  This is supposed to be natural colour, interesting...

Something similar off the coast of Baffin Island. Likely an indication that this ice is the remnants of ridging in the shallow water up against the shore. Lots of sand gets pulled up into/splashed onto the ice during the freezing season.

EDIT: Adding another photo, this one from James Bay earlier in the season (July 13).

26
The rest / Re: Pareidolia
« on: August 02, 2020, 12:33:46 AM »
Finally can see what you mean. Her head is in Thailand. The skirt is long, no legs/feet below. Pigtails sort of. And it's an arm.

Yeah, her face is Thailand, I see her looking towards the water... her left pig tail (on the right for us as I see it) is Thailand and mainland Malaysia.

But I don't see her as bending backwards, but as bending forwards slightly like she's waiting a table or stooping to pick a flower... (I see it more with Sri Lanka as heal, but her face is still turned -- in the image -- down and right).

Why German? Well the dutch damsel photo is pretty convincing, but image attached (skirt is too short though... and maybe the beer cheapens it, I donno).

27
The rest / Re: Pareidolia
« on: August 01, 2020, 07:22:25 PM »
Yes, pigtails. I always get those mixed up.  :-\
Her skirt is India. I can see it so clearly...
The Arabian Peninsula is the foot of the big doglike creature walking. With big ears...
Maybe I smoke too much weed.  ;D

I am certain I see her. She's sort of bending at the waist a bit right? She might be German... But I don't see the doglike creature... Is it in the water?

28
Arctic sea ice / Re: The 2020 melting season
« on: July 31, 2020, 01:14:02 AM »
@UCMiami

Yes, I can see the ice remnants, if mostly stationary, creating a microclimate through their melt, causing a negative feedback that slows further melt.

@thejazzmarauder
I think bottom melt can be extremely significant from early in the season, but it has more to do with how much the water is moving. Moving water has friction as well as getting rid of delays in thermal conductivity as adjacent water has to warm the lens of meltwater around the ice when there is no movement. (This is layman's physics, I could be wrong).

@arcticmelt
It doesn't look thick right now, though it may have been at the start of the melt season. It looks like very decayed ice/slush.




29
Arctic sea ice / Re: The 2020 melting season
« on: July 30, 2020, 11:16:23 PM »
I'm really surprised at how long it can take for what appears as slush on worldview to melt out. For example this patch of "ice" in Hudson's Bay, which -- according to nullschool -- is in water well above -1.8C. Why wouldn't this go poof? Is it the lack of movement, which creates a cool pocket? Surely if there was wind this would disappear over the course of a day?

GIF of the last three days.

30
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 02:53:33 PM »
Back to the current state of the ice...

The outer bands from the cyclone are not being kind to the ice in parts of the CAA.

This gif from RAMMB CIRA shows the ice in the Melville Sound moving towards the Barrow Strait.

Click to play

31
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 01:54:23 PM »
Can't quite understand the comments from wdmn and off the grid.
Simply reported on an updated report from a reputable source
Thought readers might be interested in their findings.

As oren stated, the image was a reaction to the report, not to you reporting on the report.

Specifically it was a reaction to two statements within the summary that, "the situation is little changed from the June report... there will be no rapid decreases in Arctic sea-ice extent through the rest of the summer." I was not responding to the actual extent predictions, and I don't know whether there will be a record low. I understand the post was low effort, but my reasons for finding the summary statement worthy of derision will be obvious to many posters given the recent discussion, the current weather, and what we've watched unfold since May (and June).

In other news, area is now following what extent did earlier in the month and bending downwards. With it, compaction has also come way down.

32
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 08:45:13 AM »
July Arcus report now out https://www.arcus.org/sipn/sea-ice-outlook/2020/july

"Overall, the situation is little changed from the June report. There is a collective view that September ice extent will be reasonably close to the observed linear trend line, implying there will be no rapid decreases in Arctic sea-ice extent through the rest of the summer leading to a new record low."

33
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 08:16:48 AM »
Look at how much dispersion has happened in the Beaufort over the 5 hours. Alaska is off the bottom of the image.

Click to play.

34
The rest / Re: Good music
« on: July 27, 2020, 02:51:58 AM »
The master Skip James' depression era songs are resonating especially well now.



35
Arctic sea ice / Re: The 2020 melting season
« on: July 26, 2020, 01:33:01 AM »
A look at one small part of the CAA, south of King William Island, over the last week. This is one of the southern most parts of the CAA.

July 18 - July 25. Click to play.

36
Arctic sea ice / Re: The science of ice ridging and rafting
« on: July 25, 2020, 05:50:49 PM »
I didn't say it "only forms on leads." You presented images you claimed (without any evidence) showed pressure ridges from the GAAC. They were 100s of kms long. Either they formed along leads, or a ridge formed along 100s of kms of pack ice between floes of all varying thicknesses during the summer months in unison (in spite of all of the different thicknesses potentially involved). The latter seems even more unlikely the former, as I'm sure anyone who is reading this thread will agree. That is why I concluded what your hypothesis must be -- I was giving you the benefit of the doubt. It seems clear now that you don't actually have an hypothesis, beyond that there was ridging during the GAAC -- potentially so significant as to effect the PIOMAS numbers -- and you'll throw anything that you think might stick.

The "one" paper that says that is the one looking at the mechanics of ridging versus rafting. Your statement is very disingenuous. However, it is also said in many other places, such as the report from Mosaic I sent, and -- according to wikipedia -- in the text book Weeks, W. F. (2010) On sea ice. University of Alaska Press, Fairbanks, p 664: "The blocks making up pressure ridges are mostly from the thinner ice floe involved in the interaction, but it can also include pieces from the other floe if it is not too thick."

Granted that the white lines could be pressure ridges, if those "ridges" are 2km in width you've got even more explaining to do. Not even rafting has been documented anywhere close to that.

As for the photo, where does it say the ridge was freshly formed, or that it was formed in summer? And even if you find some examples of ridges forming from multiyear ice (covered with accumulated snow), how does that prove that such things were occurring in the GAAC? Because they would better match your MODIS imagery? Your argument is circular.

When hunting for ice ridges, radar satellites are used. Not sure if we access to those, but if so you might look there.

I also note that all discussion of ridges from the MOSAiC stories describe the events as occurring in winter during freezing season: "But the ice dynamic wasn’t just a logistical problem; it was also an outstanding object of study – pressure ridges, and their effects on energy transfer, lead formation and biological activity, which were revealed – we finally had the chance to monitor and investigate all these things that take place on the ocean in winter, yielding a treasure trove of new data"


37
Arctic sea ice / Re: The science of ice ridging and rafting
« on: July 25, 2020, 09:45:23 AM »
Michael,

You are quite tenacious. Through this back and forth, I finally think we are getting to a clearly formulated hypothesis.

The papers I included in the first post above, and most reading on the internet confirms that ridging occurs primarily between ice sheets of different thicknesses. For a ridge to form 100s of kms long can only occur if there is a crack in the pack and a lead forms (i.e. new, thin ice). Subsequently, "the two sheets of ice on either side of a lead can collide with a force large enough to form ridges," out of the thinner lead ice. (NASA article on MOSAiC https://earthobservatory.nasa.gov/images/146508/drifting-with-broken-sea-ice)

So then, your hypothesis is that the GAAC formed pressure ridges in areas where there were new leads (formed maybe as late as April?) with thin ice that could be crushed.

For reasons already stated in this thread, it seems unlikely that such thin ice on newly formed leads would have maintained its structural integrity through May and June (and the insolation during the GAAC).

Nevertheless, as evidence for your hypothesis you present the MODIS images showing what you say are pressure ridges.

If we grant that these are pressure ridges, you still have yet to prove that these ridges formed during the GAAC.

I was on the NISDC website and found this: "ridges are initially thin and transparent with very sharp edges from blocks of ice piling up; also see keels" (https://nsidc.org/cryosphere/glossary/term/ridging).

This makes sense given that they are formed over open water in areas with thin, lead ice, but it doesn't bode well for your MODIS evidence, since if these were ridges formed during the GAAC, they should be "thin and transparent," and likely not show up from space.

In summary, your hypothesis has been clarified as: "pressure ridges were formed during the GAAC in areas where new leads were crushed by the movement of the pack on either side of the lead."

But,

The only evidence you have provided, even if it does depict pressure ridges, does not establish that these ridges were formed during the GAAC, and we now have additional evidence that suggests such ridging -- if it did occur -- is highly unlikely to be visible on MODIS.

38
Arctic sea ice / Re: The 2020 melting season
« on: July 25, 2020, 05:42:58 AM »
Two glimpses through the clouds today from RAMMB CIRA confirm the concentration map from Bremen.

First photo of the Beaufort. For orientation, Alaska is at the bottom of the image.
Second photo is of the Atlantic side. Islands in the photo are Franz Josef Land.

N.B. any tips on better bands to use would be welcome via private message or in this thread if it's appropriate.

EDIT: very small (almost nil) loss in JAXA extent today.

Thank You for the image and the proper giggle.

 :o LOL! I honestly don't know how that happened. The ASIF gods are messing with me... with us all!

39
Consequences / Re: Hurricane Season 2020
« on: July 25, 2020, 05:32:07 AM »
Tropical Storm Hanna looks like it's going to pull a rapid escalation to hurricane status before making landfall in Texas. The advisory this morning (as well as all previous) still had it making landfall as a tropical storm. Seems like the models are still having trouble with the sometimes explosive development of these storms.

https://www.nhc.noaa.gov/graphics_at3.shtml?start#contents

40
Arctic sea ice / Re: The 2020 melting season
« on: July 25, 2020, 05:24:08 AM »
Two glimpses through the clouds today from RAMMB CIRA confirm the concentration map from Bremen.

First photo of the Beaufort. For orientation, Alaska is at the bottom of the image.
Second photo is of the Atlantic side. Islands in the photo are Franz Josef Land.

N.B. any tips on better bands to use would be welcome via private message or in this thread if it's appropriate.

EDIT: very small (almost nil) loss in JAXA extent today.

41
Arctic sea ice / Re: The science of ice ridging and rafting
« on: July 25, 2020, 01:45:19 AM »
Good thread. Although I'd like to point out to Michael that if he thinks anticyclonic ridging during summer can be seen in satellite imagery, he has some maasssssssive explaining to do.


Whats to explain?  Are the white streaks that look like ridging not visible to you?  I cannot prove that they are for sure ridging, but look at the facts:

-ridging is proven to happen mid ocean.  So you can't say that they can't be ridges because they are mid ocean

Michael,

If you glanced at the articles I shared in the first post of this thread, you would see that assessing ridging from satellites is usually quite difficult. There's also the fact that some of the white streaks you are referring to are 100s of kms long, but there are no floes that large. Finally, you only provided an "after photo," so that even if those white streaks are ridges, you haven't provided any evidence that they were formed during the GAAC.

42
Arctic sea ice / Re: The science of ice ridging and rafting
« on: July 24, 2020, 09:37:37 AM »
It's very close-minded to shut the door to the possibility of ridging or piling up of some kind in Summer just because studies are focused to Winter, naturally.

And it's pretty unhelpful to join this discussion by leading off your post with a straw man.

43
Arctic sea ice / Re: The science of ice ridging and rafting
« on: July 24, 2020, 03:13:24 AM »
Michael, please note that the study was looking at the ice up until 2003.

That is relevant because the 30% summer (23% figure in terms of total annual ridging - which, if it were evenly distributed over the summer months would be 4.6% per month) figure has likely declined. My justification for believing that is the time period covered by the study, and the fact that volume of ridged ice peaked in June:

"This annual cycle is explained by the fact that before June, ice stays adequately compact in the Arctic basin and ridging continues..."

In the study, summer was counted as May-October. So almost all of that summer ridging happened before peak melt. The paper states that the lowest monthly production is in August, when the most energy would be in the system:

"Only a small percentage of the level ice volume is involved in the ridging processes during each month. This amount varies between 0.2% and 7.4% and has an average of 2.2% for August when monthly ridge production is minimal..."

Obviously conditions have changed a lot in the arctic, and especially this year where so little of the ice has been close to shore. This has to be acknowledged, since the ice is already reached an extent that would have been close to annual minimum in almost all of the years the study looked at, and lower than August. Moreover, the paper seems to be saying that almost all of this ridging occurs along the coast.

Let's also recall the reason why this discussion came up in the first place: it was claimed that the GAAC created enough ridging/thickening of the ice this year that it would impact the September minimum by preventing/slowing melt. Is there anything in the papers put forward so far that suggests that is likely?

44
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 10:45:38 PM »
I have created a new thread on the science of ridging and rafting in the hopes that we can begin to answer some of the questions that have come up in this thread:

https://forum.arctic-sea-ice.net/index.php/topic,3210.msg276496/topicseen.html#msg276496

45
Arctic sea ice / The science of ice ridging and rafting
« on: July 23, 2020, 10:43:50 PM »
Since there has been continued interest by several posters in the 2020 melt season thread on the question of whether the 2020 HP anti-cyclone caused ice ridging or rafting over open water (i.e. not against shore) due to centripetal forces, I am creating this thread.

There seem to be three pertinent questions:

1) Do ridging and rafting occur during the summer melt season?

2) Do ridging and rafting occur over open water? If so what kind of force is required?

3) Is there a way to answer these questions by comparing pre-anticyclone, and post-anticyclone satellite imagery?

First some definitions:

Ridging: is created by "the flexural failure of opposing ice sheets and subsequent piling of the ice blocks created by the flexural failure on top of and beneath the two sheets." It occurs most frequently between ice sheets of different thickness, and particularly when one sheet is fast (against shore).

Rafting: when one ice sheet overlaps another, and progresses until "the frictional force between the sheets, which increases linearly with the amount of overlap, arrests motion or causes buckling." It tends to occur when ice sheets are almost the same thickness, but can also happen when rubble is created between ice sheets of varying thickness, and the rubble then forces the thinner sheet into a rafting situation.

Taken from this article (hat tip to the Artful Dodger): "Rafting and ridging of thin ice sheets" https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/1999JC900031

I looked through some literature as best I could to answer the three questions above, and provide the initial findings below.

1) Some ridging does occur during the summer, though it is a fraction of what occurs during the winter months:

"Total winter production from November to April (mean value of 4629 km3 over 56 years) is 3.5 times more than the summer production from May to October (mean value of 1324 km3) and occupies about 77% of the annual amount."

"ridge volume has a maximum of 12 150 km3 in June and minimum of 9490 km3 in October. This annual cycle is explained by the fact that before June, ice stays adequately compact in the Arctic basin and ridging continues, but before October the amount of leads exists sufficiently, which reduces ridging."

"the summer seasonal production (May to October) reaches, on average, about 30% of the winter production (November to April) and gives rise to only 23% of the annual production."

Source: "Dynamic–Thermodynamic Sea Ice Model: Ridging and Its Application to Climate Study and Navigation" https://journals.ametsoc.org/jcli/article/18/18/3840/30529/Dynamic-Thermodynamic-Sea-Ice-Model-Ridging-and

2) The same article suggests that compacting forces from anticyclones can cause ridging. However, I had a difficult time deciphering a couple of passages in the paper, which seemed to me contradictory.

"The yearly averaged ice volume systematically grows in the Arctic Ocean (Figs. 1 and 2), especially in the Canadian region, during the periods with anticyclonic circulation (Makshtas et al. 2003), but the prevailing cyclonic regime leads to a shrink of ice cover, as noted by Walsh et al. (1996)... The model also shows that periods with the anticyclonic circulation in the atmosphere lead to a decrease in ridging intensity in the Canada Basin, adjacent parts of the central Arctic, and marginal seas. This decrease causes, on average, the thinning of sea ice in the early 1990s, when cyclonic circulation in the polar atmosphere was well developed."

And the other confusing passage I found, which seems highly relevant:

"The distribution of ridge production is rather nonuniform over the Arctic Ocean. It should be noted that the high ridge production around the islands, comparable to the ridge production in the Beaufort Gyre, is the reflection of ridge accumulation under onshore winds. This natural effect is an essential feature of the coastal area, where the ridged ice zones and rubble fields actually exist. Meanwhile, this ridging around the islands is not reflected in the average ice thickness here because the model does not reproduce grounded ice, fast ice, and ice freezing to the beach. Therefore, winds with changeable direction lead to ridged ice floating away from shore and spreading over the Arctic."

3) There is a method applied to the Baltic Sea to determine winter ridging to assist navigation, and this method will be (or is being?) applied to the Arctic sea ice. It is far beyond my current level of understanding or familiarity with the imagery available to us to know if we could assess the CAB ice before and after the GAAC of this year.

"Estimation of degree of sea ice ridging based on dual-polarized C-band SAR data" https://tc.copernicus.org/articles/12/343/2018/tc-12-343-2018.pdf

"Satellite Observations for Detecting and Forecasting Sea-Ice Conditions: A Summary of Advances Made in the SPICES Project by the EU's Horizon 2020 Programme" https://www.researchgate.net/publication/340548390_Satellite_Observations_for_Detecting_and_Forecasting_Sea-Ice_Conditions_A_Summary_of_Advances_Made_in_the_SPICES_Project_by_the_EU's_Horizon_2020_Programme

Finally, as Gerontocrat asked whether wind would move ridged ice more easily than flat ice. Ridges are called "sails" above the ice, and "keels" bellow, so perhaps ridging does make ice more mobile in the wind (due to having a sail).

46
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 05:43:58 AM »
After a 117k km2 loss in JAXA extent today, I wonder how long it would take the ice to change from moving in a way that leads to compaction to moving according to the new weather pattern.

In other words, when can we start ruling out compaction as a (primary) factor in the 100k+ daily extent losses?

P.S. I ask this question sincerely, not in a snarky way.

47
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 04:01:24 AM »
Victoria Strait (SE of Victoria Island in the CAA) was clear today. Below is a video of changes from July 16 to today (just two frames, as it was cloudy on the other days).

Click to play.

48
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 03:32:13 AM »
Michael,

I'd like to preface this by saying that I don't even like to guess at where the season will finish, because it seems like an easy way to be wrong about one more thing in life. I have made some predictions about the end of the month, which are modest and based off of long term loss patterns for the various arctic seas. So I am not claiming to know about what position this year will finish in, and your belief in 3rd place or above is not really what bothers me. What I find slightly off putting about your posts is the degree of certainty you speak with, in spite of the fact that many long term observers on this forum have put forward evidence that should at least make you question your conclusions. Also, you never admit when called out on something (such as your comment about the open water being "mostly on the fringes").

As for your specific replies:

Why would it be just as likely that there is more area and not less given the record low extent? You're treating this as a logical problem (area could be either higher or lower, so there's 50% chance each way), whereas such a statement must be justified empirically.

I would like to compare to 2019, for example, but 2019 had a low pressure system over the arctic for almost all of July, so it's difficult to make comparisons for most of the ice. Clearly the Beaufort was in worse shape in 2019, but that's about all that is clear (other than that way more momentum has been built up this year due to insolation).

As for the ridging/rafting, no one was questioning that this happens, so your PIOMAS link offers nothing to the discussion. A paper was already put forward on the difference in the mechanics between rafting and ridging. The question was whether we could expect this to occur during melt season on structurally compromised ice, due to compaction. You haven't provided any new information on that question.

49
Arctic sea ice / Re: The 2020 melting season
« on: July 22, 2020, 11:39:40 PM »
Implications of a compact ice pack:

According to area and volume we are currently in 3rd position, and not a huge way ahead as we are for extent.  This implies the reason for the low extent is primarily compaction and not melt.  It implies that if the ice becomes as disperse as other years extent will also be 3rd in position.  With the weather suddenly turning favorable for ice retention, a new record is out of reach from 3rd position.

Lots of sunlight is being absorbed wherever the ocean is not covered in ice.  During this year that ocean is mostly on the fringes.  A large part of this heat energy will still be there come minimum, and the energy will be used for delaying the freeze season and not for causing a low minimum.  In contrast in a year like 2012 lots of sunlight is being absorbed by ocean within the ice pack which is then available for melting ice  within days or weeks as the ice moves around and over this water that had been warming in the sunlight.

And yes I expect the compaction to also result in some thickening due to ridging/stacking etc.  Whether this is enough to be important I don't know.  But do note that it is well accepted that ice can only grow to about 2m through thermodynamic processes, and ice only grows thicker than this through some form of ridging/compaction process.

You keep repeating arguments that have already been addressed, or are otherwise nonsense.

1) Area is less reliable of a measure than extent during the summer. Obviously the GAAC causes compaction, which was the consensus before the event even started. But we have also witnessed melt out in areas that did not melt last year, such as the CAA, which is clearly not due to compaction. jdallen provided some imagery re this subject also.

2) The ice always melts from the outside in, so to say that "this year" the open water is "on the fringes" is absurd. There is more open water surrounding the ice than ever before at this date.

3) We already had the conversation about ridging/stacking. Unless you have new evidence to add that goes against the paper provided by Lodger or what was presented in the thread, please stop repeating this misleading, unsubstantiated claim.

50
Arctic sea ice / Re: The 2020 melting season
« on: July 22, 2020, 10:02:02 PM »
Looking at the individual sea data I calculate a pretty easy 700,000km2 to go by the end of the month, which would still leave us at about 400k ahead of 2019.

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