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Messages - Stephan

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1
Arctic sea ice / Re: The 2020/2021 freezing season
« on: September 19, 2020, 08:02:38 PM »
Animation of the annual max and min, from 1979 to present (click to play).

2
Arctic sea ice / Re: The 2020 melting season
« on: September 10, 2020, 01:53:49 PM »
Weekly sea ice losses from July 1st

3
Arctic sea ice / Re: What's new in the Arctic ?
« on: September 07, 2020, 03:20:37 PM »
Permafrost at Svalbard has entered the era of megamelt, and together with Russia’s Arctic coast, no other places on the earth warms faster. Also the sea ice in the surrounding Arctic Ocean experiences melting at a rate much faster than previous climate models predicted.

https://thebarentsobserver.com/en/climate-crisis/2020/09/svalbard-experienced-hottest-summer-record?fbclid=IwAR1cM0t8lAGeuR5lW3FuTDZJkhA63kYVkNJBCYk9nYhgZOJIzf-lOiz79Zk

4
Arctic sea ice / Re: The 2020 melting season
« on: September 01, 2020, 05:04:14 AM »
August 27-31.

August 1-31 (fast).

2019.

5
Arctic sea ice / Re: The 2020 melting season
« on: August 31, 2020, 11:35:53 PM »
Would a 2012-tier deviation from the trend of 2019/2020 result in a near BOE, or would there still be more room to fall? To phrase it differently, as 2020 appears to be progressing towards an in-trend approach (either this year or within the next few) to 2012 extent and area, has the risk of an outlier year causing even more extreme disruption increased?

To answer in very simplistic terms: 2012 saw a 1 million km2 drop from the year before (2011).  Assuming we see something in the range of 3.5 to 3.9 million km2 at the lowest point in 2020, *if* there was a similar 1 million km2 drop in 2021, we'd see something like 2.5 to 2.9 million km2.  Not yet threatening a BOE (defined as less than 1 million km2), but getting closer.

I may well be corrected by other people with more in depth analyses of your question, however.
This is using JAXA data. CAVEAT - all other things being equal.

2012's deviation from the linear trend was 1.5 million.
If you assume that was because 2012 saw an almost perfect set of circumstances, you can assume that 1.5 million is the maximum possible deviation possible,

The linear trend of the reduction in the minimum is circa 80-90k km2 per year.  So looking at say 2021, in 9 years that is circa 0.7 to 0.8 million km2 reduction in the expected value from the linear trend.
The 2012 minimum was 3.2 million km2, take off 0.8 million = 2.4 million km2 as the minimum possible in 2021.

BUT. The ice ain't what it used to be. Field evidence (MOSAIC etc), satellite data all say the ice is in awful shape.

So all other things are NOT equal. There is reason to at least hypothesise that a small change in the melting season weather favouring melt may produce a large increase in that melt.
One day volume will reduce to the extent (i.e. a tipping point) that sea ice area and extent losses must increase at a far greater rate (and that's just arithmetic).

A linear trend is a linear trend until... it isn't.

6
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: August 23, 2020, 05:17:06 PM »
NSIDC Graphs

Once again Central Arctic Sea area and extent losses continue to be high.

Beaufort Sea area losses have stalled, while although extent losses continue, extent is some 250,000 km2 above the 2010's average for this day. Will we see a sudden melt of that large area of 50% concentration ice shown in the Bremen false colour image (as happened in the Chukchi)? Or will it be just a bit too chilly?


7
Arctic sea ice / Re: The 2020 melting season
« on: August 23, 2020, 02:07:20 PM »
A tad off subject, but I would like to give credit to Oren, for his handling of the Moderator position during this melt season. I am sure at times he may have felt that Neven handed him a stick of dynamite. At times the comments this season have been fair contentious, but I think Oren has reigned with the required fairness and discipline.

Thank you Oren.

8
Arctic sea ice / Re: The 2020 melting season
« on: August 22, 2020, 10:24:42 PM »
First 3 weeks of August.

9
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: August 10, 2020, 07:13:06 PM »
I'd like to make an update on the NSM.

I'll use yesterday's high-resolution image that I commented on.
In this image I have embedded an image with elevations, and thus thickness, (David E. Shean et al. 2019; data used first half of 2010) and velocities (WorldView 2011).

The NE-IS is fed upstream by a small tributary and, far to the east, by ice overflowing the Ice Rumples next to the PIG (north of the ZD). The ice of this IS is carried westward by the PIG and pushed towards the funnel between the Ice Rise Evan's Knoll and the PIG itself, where it recompacts.
This is the final part of the funnel that is visible in the image.
In the funnel the movement is parallel to the PIG and the speed gradually changes from zero, Ice Rise side, to that of the PIG itself, PIG side.
As for the thickness we can estimate it at 500m, see more.

Currently the movement of the PIG and the induced tensions lead to the opening of small marginal rifts in the NE-IS orthogonal to the PIG and the pieces of IS between two rifts are bent by the movement of the PIG until complete detachment and calving. This is the area indicated in red in the image (I also added a zoomed image of this area, image from the day before yesterday).
This area creates, PIG side, a shear force (even if relative), which ensures a progressive increase of the shear as we go upstream without abrupt increases.  As a result there is almost no formation of marginal rifts in the PIG (which is positive).
Downstream there is final detachment of the pieces of IS with dynamic calvings: rapid initial movement of the icebergs and in many cases, given their size, their turning over.
This field of rifts, as well as the calving front migrate upstream and nothing seems to be able to stop this process, the only thing that can be hoped for is that this process is as slow as possible.

Clearly upstream, where the funnel widens, the process can only accelerate and there will be reunification with the already existing ZD and thus a detachment of the NE-IS from the PIG. But this process is expected to take several years.
What could accelerate it is a collapse of the part of the NE-IS already detached from the PIG and which currently provides support to the NE-IS upstream: this part is under pressure from the NE-IS upstream but it should resist, moving without breaking, for some time.

Following the detachment of the PIG from the NE-IS there may be some mini calvings (PIG side), one has recently arrived, but they should remain anecdotal.

To the west, on the front line, the large iceberg left over from the big calving (see third picture), already half detached from the PIG, should resist for a while.Indeed the rifts indicated r1 and r2 in the image are widening contentedly but their progression is slow (there is no modification of the rifts r3 and r4). This calving should have no effect on the PIG.

Click to enlarge

10
Arctic sea ice / Re: The 2020 melting season
« on: August 07, 2020, 10:32:13 PM »
An animation of the simple projections so far this melt season.

11
Arctic sea ice / Re: The 2020 melting season
« on: August 03, 2020, 07:16:10 PM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Large GiF!

Don't forget to click the like button from time to time if you like these forecasts!

12
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: July 29, 2020, 09:23:50 PM »
I wanted to add a lighter version:
with two intervals of 24 days: 17/02, 12/03 and 05/04,
and three intervals of 36 days: 05/04, 11/05, 16/06 and 22/07,
and adding little comments.

Click twice to zoom in



13
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: July 29, 2020, 02:14:25 PM »
I am starting to catch up and you will find attached the history of the PIG calving front since the big calving of 09/02 based on the Sentinel1 images of 17/02 + n * 12 days (last image that of 22/07), the image of 29/02 being missing.
The calving front has been cut in two parts: North and South, they overlap and therefore give the global vision.
I give two versions: white background and Sentinel1 image of the 22/07.

click to zoom in

14
I think it is less of either/or than both converging together.  In that case, extent would decrease faster, while volume decreases slower, merging when the ice disappears.  Note that thickness is decreasing at a rate in between volume and extent (roughly halfway according to Stephan's table).  Mathematically, this ensures that volume would decrease faster (initially) than extent as the added dimension (thickness) is decreasing also.  If thickness were held constant, volume and extent would decrease at the same rate.  As I pointed out to Glen, the slope of the volume decrease has lessened over the past decade, indicating that volume is decreasing at a slower rate.

Be careful not to fall into the circular argument trap. Average thickness is calculated from volume vs. extent and changes in a derived value tell us nothing extra.

Besides, the mathematics of the case are not important. This is a physical system, highly complex and variable. And I disagree that there is any indication of the slope of the volume decrease slowing down over the last decade. The variability is too great to allow any such conclusion. The image below, from Stephen's post gives me absolutely no indication of a slowdown.

Quote
It is not a matter of thinner ice melting at a different rate, which it does (we agree on that point).  Rather it is the location of the ice (further poleward) that matters more greatly.  The angle of the sun means that less incoming solar radiation is available for melt.  Granted, this point can be argued, and has been to a great deal.

This is an extremely simplified view of the physics of the system. I have argued for the opposite effect, i.e. the smaller the polar ice cap, the easier it is to melt because of the amount of open water surrounding it.

I'll perhaps expound on that further in another post, but here is the graph I promised. Just from eyeballing the graph and doing some quick calculations, the annual volume loss ticks in at 300 km3 over a 45 year period (1975-2020).

The apparent "slowdown" that you think you see in the last decade is not statistically valid - but the large fluctuation is interesting, and could perhaps be indicative of a stalled acceleration. In other words, the system could be trying to accelerate melt after 2010 but a temporary stall in the middle of the decade confuses the picture.

15
Welcome back binntho. Excellent post.
+1 :)

16
Welcome back binntho. Excellent post.

17
I think we all agree, as Glen points out, that the decline in extent must at some point catch up with the decline in volume. Hence the decline in extent cannot continue at its current linear rate. But will the rate of change be incremental or sudden? I.e. will the curve bend or break?

And is it somehow linked to the thickness of the ice, i.e. does the rate of melt increase with falling average thickness? The physics are not reversible, but still, the following holds true:

      It is well documented and accepted that the chemical and structural characteristics of Arctic sea ice varies with thickness.  Those qualitative differences have to make some difference to the melt rate. 

One of the important differences is to do with the core temperature of the ice. The sooner the core warms up, the faster the ice melts. And thinner ice warms up faster than thicker ice. Other differences between various thicknesses are based more on the age of the ice than the thickness per se. Brine channels, brittleness, structural strength etc. change with age rather than thickness, but then thickness also increases with age so again there is a link albeit not a direct causal link.

All in all I agree with Glen that ice melt should accelerate with decreasing thickness, but how large is this effect, and more importantly, could it be used as an explanation for the current rapid decline in ice extent?

     Is there a fallacy in this line of thinking?  What alternative mechanism accounts for the  required unification of Extent and Volume as they approach zero.  Binntho I'm talking to you!  This is right up your alley and I haven't seen you post for a while.

The Internet for the entire country was blocked for over 2 weeks, and then only activated in the capital. So I took the first plane and here I am in a hotel room, hoping to catch up on some work and instead indulging in my preferred pastime of writing on the ASI forum!

Coming back after 3 weeks and seeing the incredibly rapid melting that has taken place in July has been fairly stunning. As of today the difference between the current year and the second lowest is almost 630.000 km2 - an incredible difference.

My own view as developed over the seasons is that it is rather the amount of open water along the perifery of the ice that will be the largest contributor to accelerated fall in extent, rather than the average thickness of the ice.

Large areas of open water during maximum insolation means that a lot of extra energy enters the system, but of course only where the ice is not. A delay to refreeze rather than an accelerated melt. The second factor needed is storminess - which has been missing for all of July as far as I can gather, but which might well be picking up now. Storms move the warm waters around, bringing them to where the ice is, storms cause waves that break up the ice (and the longer the fetch, the bigger the waves), and storms late in the season probably have a positive impact on the radiative balance.

So the current situation is exactly what I would predict would accelerate melt as soon as the storms kick in. But that does not explain why we have so much open water to begin with!

Perhaps a simplification of the current situation would be to reduce it to three or four factors that combine to cause increased melt at different times - the first of course being the steadily increasing global temperature, the second being the unusually warm spring followed by a very sunny July this year, the third being the increasingly thin and fragile ice that undoubtedly melts faster than the older and thicker ice, and the final (and to my mind, increasingly important as time goes), is the amount of open water.

But for the future, in my opininon the main factor in increasing the rate of melt will be the amount of open water in the second (post max insolation) part of the melting season. A steady linear decline overall will secure the increased amount of open water up to that point, and a non-linear effect of open water + storminess will take care of the rest.

18
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: July 22, 2020, 11:15:21 AM »
Let me try to formulate an answer and see if I understand this myself.
X axis is years.
Y axis is each of the monthly-average parameters Stephan tracks (area, extent, volume, thickness).
Slope (negative) is the of the linear trend line of the previous years (1979-2020).
A line is approximated for each parameter, for each month of the year, and its slope is calculated.
BOE value is where the extrapolated line hits zero. For each given line, for Y=0, what X?

Take July volume. The slope of the linear trend is minus 0.359. This is the average loss per year. Given the current value of the trend line (not provided) and the slope, it is calculated to hit zero at year 2034.
Sharper slopes are highlighted with orange and yellow colors.
The same "BOE value" is calculated for a logarithmic trend, however I assume the provided slope is for the linear one.

19
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: July 19, 2020, 09:51:14 PM »
Update of Jim Pettits "step by step" milestone graph.

BTW, i feel the need to praise Jim Pettit. His sea ice graphs opened my eyes sometime in the past. He has a talent of making data visual and accessible. One of the best out there!

20
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: July 19, 2020, 07:07:31 PM »
Hudson   - 71 %


OK, i'll do something i don't usually do: Making a prediction!

I predict next week we'll see minus 100%.

21
Arctic sea ice / Re: The 2020 melting season
« on: July 10, 2020, 06:10:09 PM »
RE: #2478 bathymetry

22
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: July 09, 2020, 06:21:29 PM »
Not big news at the SSM, but the new rift has widened giving movement to the entire south side of P2.

At any given time calving of P2, Cork3 and Almand

12-day animation aligned with the PIG, which gives the movement of P2

Images très larges, click to animate

23
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: July 05, 2020, 08:59:50 PM »
Does this flow speed diagram contain any information about the position (and its possible change) of the grounding line?
It's been a while since I read the paper referenced on the site, but it does a pixel-by-pixel pattern matching which often results in a lot of outliers, but it is right enough that the trends are pretty solid.

I think it is safe to say the that long stretch of ice moving at a constant speed is the floating ice.  Except for rifting near the calving line it will move at a constant velocity, at least in the center of the glacier where the transect is located.

By comparing the earliest and the latest images below, you can see a slight regression of the grounding line, at least at the transect again.  There may be other areas where the grounding line has retreated, but I'm not sure there is enough detail from the velocity maps to pick them out.

In a steady state, thicker ice moves slower (because flow is velocity times thickness) so the change in velocity as you move back from the grounding line is due to the higher ice elevation.

I think the best macroscopic explanation for the faster velocity is simply that the length of the floating ice is shorter.  Calving at the front has reduced the amount of friction at the margins that slows the ice down.  Of course, faster ice is necessarily thinner (due to the flow argument) and thinner ice is weaker and calves sooner, giving you a positive feedback loop over the long term.

24
Science / Re: 2020 CO2 emissions
« on: July 05, 2020, 04:34:04 PM »
So we are 10 pandemics away from solving climate change. I'll talk to some bats and pangolins I know.

25
Science / Re: Re: 2020 Mauna Loa CO2 levels
« on: June 23, 2020, 09:12:30 PM »
It will be interesting to see if methane concentrations decrease later this year since much of the US and Canadian fracking decreased in May and looks to be reduced through 2021 with the oil oversupply and Covid recession demand destruction.

Considering methane leaks are a feature of fracked wells, and considering that the frackers have even less free cash than usual for properly abandoning their wells, I  do not expect methane pollution to drop appreciably.

26
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: June 06, 2020, 02:27:34 AM »
Mr. Paolo,

You are doing a very good job. Perhaps you might write up a short version and submit to the cryosphere journal ?

https://www.the-cryosphere.net/index.html

sidd

27
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: June 06, 2020, 12:51:16 AM »
Now let's turn our attention to the last few months and the effects of the SW-ZD on the MIS itself:
Indeed in the MIS the push towards the front is powerful and the problems start when the shear on one edge is not constant, but acts on precise zones and especially when these zones are no longer followed downstream by other zones with a shear of the same magnitude or even a shear zone at all. These shear differentials indeed determine tensions in the MIS that will create rifts that will extend to its center (remember that shear is not limited to the edge, but extends inside).
Image of 24/09/2019: the rifts R3 (downstream of P1) and mR1 (downstream of P2 do not exist yet)
The brake by the Cork on the downstream part of R2 is almost nil, because of its rotary movement, which no longer opposes the movement of the future Iceberg. Hence the rapid widening of R2. But, still because of its progressive rotation, the brake on P0 (the point downstream of P1) is not strong and will weaken later. This will cause, in October, the opening of mR1 in a first time, followed in a second time by the explosive opening of R3 and the entry into sleep of mR1. We can think that the Crescent/Keystone complex brake on P2 was initially stronger than the Cork2 brake on P1, but that quickly the latter, which is downstream, increased its action and became the main braking point of the MIS.
The result can be seen in the image of 23/12/2019.
In the final image of 16/03/2020 we see that P1 is free in its movement and that the action of the downstream brake is of the Crescent/Keystone complex on P2, which can only lead quickly to the calving of P2, which we have just witnessed, and the reactivation of mR2.
Another point to remember, in order to understand the events of this season, is that the edge of the PIG-fed part of the MIS is a point of resistance to the progression of rifts, which can lead to a temporary halt in their progression, or even to the birth of a separate, seamless extension beyond this point of resistance, and possibly to an extension in another direction as mR1 has recently done (in other words: stopping the extension of a rift may not mean that there is no more tension in progress).
In a next post I will analyze the present and the future, but already I invite you not to observe the SW-ZD with all the attention returned to its calving, but rather in the opposite direction: towards its braking action on the MIS, an action that can be extremely destructive.

Click twice to zoom in.

28
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: June 05, 2020, 10:59:21 PM »
In this post I present in more detail the history of the SW-ZD between 2016 and 2019.
I have noted the main elements of the SW-ZD and the surrounding elements that are used to understand recent history in the Sentinel-2 image of 17/11/2019 and in the D.E. Shean et al. 2019-Figure3 elevation image. I have added an animation with the images relative to the 2016/2019 period (images relative to the month of November).
An analysis of the last period as well as possible futures will be the subject of other posts.
To remember :
> As said in the previous post at the junction between T11 and the MIS pre-existing fractures (see second image) have reopened and transformed into rifts that have completely cut this tributary in all its width. This block was then broken on the MIS side.
> the line of weakness represented by the arc structure caused the complete breaking of the block between Cork2 and Cork3 giving rise to the Keystone (a runt of Cork).
> MSS includes not only the ice provided by the PIG, but also the contribution of T_ and part of T11. Indeed the tearing of the rift-isolated blocks occurred inside T11 and not on its MIS-side SM. This structure on the South side of the MIS, integrating parts of the SIS, explains some weaknesses of this part, weaknesses that appeared during the partial calvings, in late 2019 and early 2020, of the tip of the future Big Iceberg.
> relative to the first pinning point of the first image we can note that currently there is no longer a direct join between T11 and MIS, but only between its SM to the East and the MIS. We can hope that the movement of T11 can recreate a more efficient joint at least for a while.

Click twice to animate and zoom in

29
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: June 04, 2020, 08:33:53 PM »
I wanted to check with the Modis images between 2001 and 2019 whether the recent situation of the SSM was completely exceptional or whether similar, albeit smaller, phenomena had already occurred or not. So I retrieved Modis images, one per year relative to the month of December (except for a few cases for which there were no images for the month of December).
I found some expected results, but also an intriguing fact:
I have noticed the exceptionality of recent events compared to the history of the last two decades: there are indeed two depressions in 2001 towards the SWT, one of which will give birth to two very localized small fractures, and which move slowly towards the front to calve in 2017, but nothing comparable to what has just happened.
The fracture downstream of the future Cork dates from 2014, in 2016 the fractures multiply downstream of the Arc Structure and in 2017, following the beginning of the collapse to the north, the fractures also extend upstream of the Arc Structure.
These fractures in tributary T11 are located where fractures had started further upstream along its SM to the east.
These results were expected or reasonable.
The more detailed analysis of recent years will be in a later post and will be based on the Sentinel-2 images, but I will anticipate the publication of this animation because of the unexpected result:
Between 2011 and 2016 we have the visual impression that the T11 tributary is pushing the MIS north?!?!
I think that, at least in part, this is an impression and not a fact (different snow cover, the MIS is moving and the structures we visualize are not the same, ...), but the visual effect is very intriguing and continues year after year, so I wanted to have your opinion.

30
Arctic sea ice / Re: Arctic Image of the Day
« on: June 03, 2020, 01:39:34 AM »
Just imagine if the Henningsvær club makes it into the UEFA cup and is forced to re-build their stadium into an internationally accepted arena which gives place to (tens of) thousands of fans ?!?


Yeah, yeah, I know exactly what you mean, would just be another of those pittiful things that happened to become so common nowadays.


Glad you like them.

31
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: May 29, 2020, 12:01:23 PM »
Tor,

I forgot to say that the evolution in the SIS was not unexpected and I started talking about it in February: "I think they will extend later in the SWT and will have to be followed as they may lead to significant calvings in the SWT."

I add an animation with today's evolution: the ice mix above the Crescent is gone, the Crescent itself is taking off and the other iceberg is going to follow...

32
Arctic sea ice / Re: The 2020 melting season
« on: May 29, 2020, 12:54:02 AM »
Again, on the topic of the Kara sea. Here's a zoom in. 24./26./28.05.
       Thanks for those superb and highly informative images blumenkraft.  Am I correct that the reported Extent and Area values for that location on those three days is likely to show virtually no change?  Yet the change is dramatic when ice quality and thickness is considered.  That is the monster hiding under the bed for ASI loss.  It doesn't change much for a long time as it absorbs energy and rots out .... and then it falls prey to some intermittent melting event.

        A similar point (albeit in a far distant context) about smooth model projection tractories vs. the bumpy ups and downs of what actually happens is made in a short video by Peter Sinclair https://climatecrocks.com/2020/05/28/new-video-breaking-bad-news-in-florida-keys/
 
       That may seem off-topic, but my point is that the same principle applies to Arctic melt and is becoming increasingly relevant as 2020 early season conditioning softens up the ice for a potential sucker punch later.  Because of the ways we measure/perceive changes, they don't make an impression until a threshold is exceeded and then change seems to erupt suddenly.  But it was building all along.

       Loss of MYI was strike 1 of 'below the surface' change.  Thickness decline leading to structural weakness, fracturing and increased mobility is strike 2.  Strike 3 is when the rot is no longer hidden.

       As Juan Garcia's tag line says, Extent losses mask the other dimension of Thickness loss which is not as intuitively apparent to our visually based monitoring.  Thus, an entire dimension of ASI decline is essentially hidden, and accumulates with less notice.  Then another GAC (or current forecast for large areas of clear sky within 24-->10 days before solstice, https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.prcp-tcld-topo) comes around and Wham!, a whole lot of built-up change potential suddenly becomes manifest, appearing as a dramatic new event even to folks who have been watching all along. 

       I'm preaching to the choir of course, and not revealing anything new to the people who come here.  But those pictures compelled me to comment on ice condition as an under-appreciated dimension, and as the defining characteristic of the 2020 melt season so far.  Call me Chicken-Little, but that ice looks dangerous.  And the records indicate that reaching that condition in May is anomalously early for the Kara Sea.

       All of which is a long-winded way of saying what A-Team (I think) once said.... one of these days... the ice will go "poof."  The nature of complex, interactive, chaotic systems is to not see change coming until it suddenly happens.

33
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: May 26, 2020, 03:01:24 PM »
To help those who follow this forum less closely, to situate the events of this year's PIIS, I wanted to trace the calvings.
I based myself on the image of the 01/02
The lines drawn are relative to the PIIS losses and do not correspond to the current position of the front that has moved since 01/02.

Click twice to zoom in

34
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: May 22, 2020, 05:03:12 PM »
Same 6-day GIF, with a different focus.  Hard to be sure about cause and effect, but it certainly looks like the melange at the margin started to give way and the rift opened up in PIG.  Also predictions are even harder, but it sure seems like the calving could be soon.

35
Arctic sea ice / Re: Nullschool Forecasts
« on: May 21, 2020, 03:14:14 PM »
      FG  and others - when you comment on a benign or threatening forecast, please specify what it is you are referring to.  Otherwise, I may not be able to see what you are seeing, and I suspect neither do a lot of other people.  Sorry to nag, but this has happened a lot lately by various posters - noting something extreme or of supposed importance without specifying what it is. 

36
Antarctica / Re: Thwaites Glacier Discussion
« on: May 17, 2020, 09:54:49 PM »
Here is an additional image that puts everything from the last post in context.  Note the many fractures at the Western transition of the TECZ which are caused by ice moving faster than the neighboring pinned ice.

The grounding line from 2011 is in blue.

37
I found this page from ESRL/PSLab on Near Real-Time Verification of Short-Term Forecasts During MOSAiC.

https://psl.noaa.gov/people/amy.solomon/MOSAiC_NRV.html

The goal of MOSAiC-NRV is to evaluate the skill of fully-coupled short-term forecasts after each leg (approximately every 2-3 months) of the MOSAiC campaign at the Polarstern location. Multi-model diagnostics focus on process-based evaluation of the coupled system to identify systematic biases that limit the skill of Arctic forecasts.

The attached image highlights the difficulties with forecasting 2m temperatures in the high Arctic even at only 2 days out.

For example at day 44 (Nov 13th?) the obs was reporting - 18 C (probably from Polarstern) with NOAA - CAFS predicting -26.5 C and ECMWF IFS predicting -23 C.

There is quite a lot of variability on these charts, comparing the models to the obs. Especially when you get to a 10 day lead.   

38
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: May 17, 2020, 01:19:43 PM »
Two animations related to PIG news:

First animation related to a mini calving of the "Temporary Cork".
Are the images of the 16/05 and 17/05 (they are very different orbits, hence unwanted effects), aligned on P1.
The calving concerns a small piece that was stuck to the iceberg b4 (in front of b3)

Second animation on rift developments in the MIS.
Are the images of 23/04 and 17/05 (24 day interval; very large images)
Calving for the next season is getting ready!

Click twice to animate and zoom in

39
Arctic sea ice / Re: The 2020 melting season
« on: May 16, 2020, 01:47:20 AM »
    Ditto ArcticMelt2, thanks for the WAPost article and also those ice thickness images.  They could have spiced it up with some ASIF quotes from the Fabulous Friv.  It is a credit to the ASIF that the experts quoted in the article didn't add to what has already been noted in greater detail in the forum.  Good to see a major US press outlet paying attention to news that matters vs the latest ramblings of the mad King.  Actually, the WAPost climate team led by Chris Mooney is among the best of all the major newspapers/magazines.  Mooney even did a story about Neven and the ASIF back in 2016: https://www.washingtonpost.com/news/energy-environment/wp/2016/11/30/he-created-a-beloved-blog-about-the-melting-arctic-but-it-got-harder-and-harder-to-write/

     Comparing the 2012, 2019 & 2020 sea ice thickness images, the one strength 2020 had was the thick ice near the Fram Strait.  That is the very ice that was presumably pummeled by the warmth, sun, and WIND this week.   2012 and 2019 each had a long arm that may have impeded Arctic-wide rotation.  2020 lacks that structural brace.  I don't know if Arctic-wide ice translocation is affected by the distribution of thick ice at that scale.  The significance of that pattern could just be a visual figment of my imagination.  (Or as Pete Walker said: a "Fig Newton of my immaculation") 

     The last 7 days of the current GFS shows Kara Sea temps consistently above 0C.  Not much clear sky & direct sun in that forecast, but the clouds bring some rain (too warm for snow) to deliver additional thermal energy to the surface.  All of which leads to forecast zero snow cover in the Kara by May 24 https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.snowd-mslp.

    The Kara is already running below previous years (https://forum.arctic-sea-ice.net/index.php/topic,2975.600.html#lastPost thanks to Gerontocrat).  Putting that together with the forecast suggests that by June 1 the Kara could be in unprecedented condition.

    The Barents Sea hardly seems to matter since any ice in it is doomed anyway.  But FWIW, Earth Nullschool shows continued low-pressure system winds scouring it out for another day or two.  Does it make much difference to clear the lanes for more export out of the CAB?  Erosion of the ice on the CAB - Barents border can't help.  At least the great Fram Flush of early 2020 has ended. 

     Following up on Freegrass's tiptoe through the tulips of DMI images, looking at the DMI temperature graph for every year since 1958 shows that this early-mid May warmup has no real match in previous years. 

     It seems like every year the ASIF gets all heated about impending ice doom.  2020 so far is providing some hard numbers in that direction.  Yes, it is still early, but as wiser watchers have noted, it is the early momentum that sets the stage for the rest of the melt season.  True enough that a basin-scale clear-sky event would be worse if it happened 2-3 weeks from now and closer to the solar max.  Then again, decreasing albedo well BEFORE the solar max increases the impact of reduced reflection of solar radiation. And having a clear-sky event early does not preclude having another one later.

40
Science / Re: 2020 Mauna Loa CO2 levels
« on: May 03, 2020, 10:20:20 PM »
Stephan, the data has not been updated for the current week; your numbers are identical to last weeks post. We have to wait for the figures for the week starting April 26th.

41
Antarctica / Re: PIG has calved
« on: May 03, 2020, 12:12:25 PM »
Calving of sR1


42
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: May 01, 2020, 09:27:57 AM »
Semimonthly BOE evaluation. -- Sorry for missing the mid-month update, personal issues. By the time I was ready to post I figured I should just wait until the end of April anyway.

As of April 30th, extent is 12,627,020 km2. With on average 136 days to go until the end of the melt season on September 13th, we now require a daily drop of -85,493 km2 for a BOE to occur. (See Attachment 1).
Additional fun fact! In the month of April we had zero days where losses outstripped their daily BOE requirement. We had 4 of those days in April 2019.

Total extent loss so far this season is -1,820,621 km2. This has resulted in the current average daily drop of -31,390 km2. Since the year 2007, this is the 6th highest average daily loss from maximum to April 30th (2007-2020). (See Attachment 2).

Although it is worth noting that the total extent loss from maximum is 2nd highest on record behind only 2019. (See Attachment 3).

Looking only at the month of April, 2020 lost -972,854 km2, nearly 100,000 km2 less than the 2007-2019 average. This is the 5th smallest loss since 2007. (See Attachment 4).

43
Antarctica / Re: PIG has calved
« on: April 27, 2020, 12:34:09 PM »
I accidentally found this NASA photo of the crescent in his childhood.

I thought it was pretty and I post it.

click to zoom in


44
Arctic sea ice / Re: The 2020 melting season
« on: April 26, 2020, 09:45:50 AM »
April 20-25.

2019.

45
Antarctica / Re: PIG has calved
« on: April 23, 2020, 07:12:38 PM »
Temporary Cork, the die is cast:

The piece b1 that seemed solid, in the last Sentinel2 image, has lost half of it in several calvings in the last 12 days (see attached anime image), the last of which is the one highlighted this morning.
This piece, wedged between "keystone" and "crescent" is under heavy stress (pressure and shear) and now the distance between these two icebergs is greater than the length of b1. The situation is not tenable and the "keystone/b1/crescent" joint can now break at any time (let's say between 5 and 15 days).

So there's no point in looking at the stability of the other joints in the Temporary Cork.

46
Antarctica / Re: PIG has calved
« on: April 23, 2020, 04:36:56 PM »
Today there was also a high definition Sentinel1 image of 09:26.

So I wanted to check if there were any differences and of what type. I find a shift in the other direction, but more limited and concerning only the two bigger icebergs in the center.

So it remains a promising track and it is not invalidated.

Remark: For this type of tests using images corresponding to different orbits, it takes a lot of patience to align the images relative to what you want to highlight and you must be sure that you don't highlight effects induced by the fact that these images correspond to different orbits!

Click twice to animate and zoom in.

47
Antarctica / Re: PIG has calved
« on: April 23, 2020, 12:01:37 PM »
I compared the two Sentinel 1 images of 22/04 08h46 and 23/04 04h35 and I see that the rotating current of the Pine Island bay has been practically frozen. The speed of this action, planned by Baking, surprises me a little.

But above all I noticed a movement of the icebergs of the bay towards the SIS and the SWT, movement which can be explained only by currents related to the tides (there is about 4 hours difference between the time of day of the images).

I suspected that they existed but I thought it was impossible to highlight them with our very limited resources and I was wrong!

Remark: the movements towards the open sea in the top right corner are the consequence of the mini-calving communicated in my previous post.

Click twice to animate and click.

48
Antarctica / Re: PIG has calved
« on: April 23, 2020, 11:27:56 AM »
No problem, Interstitial, and thanks again for the articles.

Before the forecast, the news: a mini calving in the Temporary Cork, more precisely from b1

Click twice to animate and zoom in

49
Antarctica / Re: PIG has calved
« on: April 23, 2020, 11:09:56 AM »
I moved the maps to the thwaites thread where they belong. I shouldn't post while tired.  :P

50
Antarctica / Re: PIG has calved
« on: April 22, 2020, 04:10:36 PM »
Yesterday I had posted (post 2097) an animation to show the currents in action at the calving front.
Today's image confirms the analysis.
Remark: even if the sea is freezing, the movement continues and I remind you that this area will see the formation of polynyas in a few months, as soon as the outgoing current starts to regain strength.

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