Support the Arctic Sea Ice Forum and Blog

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - Stephan

Pages: [1] 2 3 ... 6
1
Antarctica / Re: PIG has calved
« on: Today at 07:03:41 PM »
I call this one "Schrodinger's Tip"

2
Antarctica / Re: PIG has calved
« on: Today at 06:30:48 PM »
While waiting for the images of the 26th we have the images of the 25th concerning the ice rumple on the west side of the SWT:
The whole north side is breaking up and calving very quickly, although the icebergs may stay there for a while because of the pinning points:

* Overall picture

* Zooming in on the iceberg that has almost calved

* Animation of the zoom on the south side from the images of 06/01 and 25/01 (the interval is not optimal, different orbits, but the image of 05/01 was not good  >:( )

Translated with www.DeepL.com/Translator (free version)

3
Science / Re: 2020 Mauna Loa CO2 levels
« on: January 19, 2020, 06:42:05 PM »
Thank you Stephan. Since you are regularly updating several GHG readings, would it be possible to add a CO2e figure?
In that way we'll have the cumulative GHG effect updated. I know it depends on assumptions but you can put those in.

4
Antarctica / Re: PIG has calved
« on: January 19, 2020, 04:27:05 AM »
Previously!

27 frames, monthly increments, click to play.

5
Antarctica / Re: PIG has calved
« on: January 18, 2020, 04:25:41 PM »
Thanks for that Paolo, much better than my effort.

With 12 days between those images, it looks to me that if the movement continues at the same rate then green line will become perpendicular in about 24 days. So it seems unlikely that cork could continue to provide much resistance for more than about 24 days. (Could of course happen earlier with small calvings/splits/increased speed etc.) Slowing the movement might make it longer but there is so nearly enough room now whereas previous a high rate of squeeze was needed to make the progress it has, so slowdown now doesn't seem likely. Perhaps this is what Paola is referring to when he said "As soon as the pressure stops (and it is decreasing)"?

6
Antarctica / Re: PIG has calved
« on: January 18, 2020, 03:16:00 PM »
I tried to be as precise as possible, for this reason I used the images of 06/01 and 18/01 (the two most recent homogeneous images).
I used the same colors as Crandle.
We can see that the movement tends to be perpendiculous at the Cork and that on the 18th we're not far from 90°, but not yet...

The compression effort, in the past months, has had several effects and, to limit myself to the future Iceberg:
* mini-calving at the joint
* opening of the longitudinal fractures (parallel to the calving front) in the Iceberg
* in the north it probably delayed the opening of fractures parallel to the flow due to the shearing, which may cause more damage to the pinning point (in the static or semi-static shelf in front of the pinning point) which may move the pinning point upstream (which is not good at all)

I also suspect that the action of the Cork it is for something in the very fast opening of the R3 (which is not good at all)

7
Antarctica / Re: PIG has calved
« on: January 18, 2020, 12:48:50 PM »
Where is this pressure coming from? The shelf seems to move perpendicular to the cork, not towards it. And it looks to be in a position where if the shelf does push towards it, it would not hold back at all, it would just rotate away effortlessly and yield.

This is how I interpret it. The compression pressure increases until we get to the narrowest pinch point which I have tried to indicate below. Basically calving and cork are too wide to fit through the gap but we are now nearly at the pinch point.

This shows the pressure will soon start decreasing but not quite there yet. However I am not sure my perpendicular and direction of travel are perfect.

Southernmost point in direction perpendicular to travel is nearly at the narrowest point. Also just a little more rotation by cork and direction of travel for calving will be free. Or maybe a combination of these.

The southern pinch point has been slowly deforming to make the gap wider. While ahead of the northern pinchpoint there have been calvings which I think are indicative of this compression stress.

8
Antarctica / Re: PIG has calved
« on: January 11, 2020, 04:12:36 PM »
Three new animations based on the high definition images of the Sentinel 1 of 30/12/2019 and 11/01/2020 (not big news) :

Rifts on the NE side:
* R1 widening, but no extension
* R2: tension at NE with almost complete overshooting of the resistence point and joint between the two fractures and small NW extension before the resistence point (this extension partly absorbs the tension of the shelf and could temporarily block the extension at NE).
* R0 major extension and widening

Rifts on the SW side :
* R1 small extension : the very thin piece between R1 and R2 doesn't oppose any resistence it tends to follow the movement of R1 and widening.
* R2 major widening
* R3 impressive expansion and widening

Cork:
* tends to partially detach itself from the SIS and stick to the future SWT-SIS iceberg

Twice click to animate and zoom in


Translated with www.DeepL.com/Translator (free version)

9
Antarctica / Re: PIG has calved
« on: December 26, 2019, 08:14:59 PM »
Attached are the zooms related to the degradation of the rift (to position it see previous post), the modifications are small, but in 17 days, and normally it moves very slowly ...
It will be necessary to monitor it from time to time.

10
Antarctica / Re: PIG has calved
« on: December 24, 2019, 03:25:50 PM »
Thanks for all the recent updates. The PIG really looks bad. I am very surprised the big one hasn't calved yet, but overall the cracks and destruction zones seem more prevalent (and of course more inland) than they used to be.

11
Antarctica / Re: PIG has calved
« on: December 24, 2019, 08:42:50 AM »
(the "blumencrack area").

LOL, never thought this term gets adopted... ;D Anyway, i feel honoured, Stephan. Thanks for that. :)

So, suppose the grounding line is behind the line you draw it. That would cause the area behind the cracks to slowly start to float. Since this part of the shelf is thicker than the floating part, it would elevate higher, would cause cracks at the points where the cracks are... Right?

12
Antarctica / Re: PIG has calved
« on: December 24, 2019, 12:00:21 AM »
Stephan,
Once the iceberg has calved, the "Cork", if it doesn't break off at that time, won't be able to stay in place for long anyway. The next piece won't be able to assume this function (it doesn't have the physical configuration to do so) and behind it there's nothing left.
It will take time, it's a dense mix of big pieces, but it's inevitable: this whole area will empty. The SIS is not moving fast enough to stop it, and even if it was moving faster the PIG would end up breaking it again (the PIG is moving too fast to hope for anything else). It is unstoppable
This area is fed by a tributary which will be destabilized too (and behind it is the TWG which in the future could suffer from it).

Finding the grunding line is very difficult, normally it requires interferometry between high-resolution radar images corresponding to identical passages very close to each other (one must determine the subsidence and the uplift induced by the tides), so having a suitable satellite and making it available to the scientists (for example for the calculation of the grunding line of the PIIS part related to the PIG in 2015, and limited to this part, they used the COSMO-SkyMed satellite, and in particular two satellites of the COSMOS satellite constellation which allow for two acquisitions one day apart, and with campaigns lasting several days; I would post information related to this article). It cannot be deduced from an image of the surface (from these images one can deduce only areas that almost certainly do not float: uplift that cannot be explained otherwise).

Small remark: we can't really use the term PIIS, which includes NIS, SIS and the "PIG" component, to design only this component. For this reason, I use the PIG notation also for this component, which is also incorrect. Some authors use the term "Main Ice Shelf" or "Central Ice Shelf" which are correct, but I believe that this term would cause confusion in this forum (I don't use them for that reason). We would have to find a term that is appropriate for everyone.

PS: In the last post (1325) the PIG annotation at the top right disturbs me a little bit, at the limit, by not being able to position it upstream of the big yellow arrow (out of the frame), it could have been put completely at the bottom.
And a thank you for all your work on the last image of Sentinel 2.  :)


Translated with www.DeepL.com/Translator (free version)

13
Antarctica / Re: Thwaites Glacier Discussion
« on: December 08, 2019, 05:06:45 PM »
I thought I would show a long-term GIF to demonstrate what I've been talking about.  It shows the "wedge" being driven into the ice mass and the pressure point is causes on the Tongue.  All motion is relative to the Tongue, so things you see moving left to right are moving slower than the Tongue.

There are three phases to the GIF: 1) February-August The wedge is being driven into the ice mass, 2) September The ice mass pushes "down" on the Tongue, and 3) October-November The "cork" comes free (not shown) and everything moves along with the Tongue so there is little relative motion.

It may not be a coincidence that the "cork" pops free just as the melange starts to push hard against the Tongue.  It could be that the Tongue pushing back put enough pressure on the cork.

EDIT: See my Reply #142 from October 13 for a GIF of the "cork" coming loose.

14
Antarctica / Re: Thwaites Glacier Discussion
« on: December 07, 2019, 11:18:32 PM »
. . . looking forward to an actual Sentinel picture of that area in the next days...

Here is today's Sentinel-1 radar image compared with 12 days ago.  Fairly substantial movement, but nothing "surprising" to anyone who has been following along.

15
Antarctica / Re: PIG has calved
« on: December 07, 2019, 12:24:31 PM »
Sure enough, enough people are having an eye on this!!  ;D

(Deleted my post since Wipneus' GIF is so much better. But i want to point out that i was first! :P)

16
Antarctica / Re: PIG has calved
« on: December 07, 2019, 12:22:22 PM »
Indeed, very little support left on this side left. The darkening has reversed again (Sentinel 1 SAR, at least for the PIG) and we can make a decent animation again.

17
Antarctica / Re: PIG has calved
« on: December 06, 2019, 02:31:33 AM »
The PIG definitely seems like it's undergoing a slow-motion collapse, with the only consolation being the super-high level of science in this thread. Thanks to all the posters keeping us updated with images, animations and commentary.

18
Antarctica / Re: PIG has calved
« on: December 04, 2019, 08:26:35 PM »
There is currently a small scientific team camped in tents within sight of Pine Island Glacier.  Anyone who thinks the calving will be within the next month should be watching this twitter feed:

https://twitter.com/geologicalJo/status/1198916665808961536

19
Arctic sea ice / Re: "Stupid" Questions :o
« on: November 30, 2019, 08:21:18 PM »
Tom,
You may want to especially read (listen to) what Katharine Hayhoe has to say (e.g., her site, Wikipedia, TED talk, YouTube, etc.).  From Wikipedia:
Quote
Katharine Anne Scott Hayhoe (born April 15, 1972) is an atmospheric scientist and professor of political science at Texas Tech University, where she is director of the Climate Science Center.
...
In 2009, she and her husband, Andrew Farley, co-authored a book called A Climate for Change: Global Warming Facts for Faith-Based Decisions, which outlines the ways in which climate science reflects conservative Christian beliefs.
...
Hayhoe, who is an evangelical Christian, is the daughter of missionaries.
...
She has figured out some ways to sidestep denier memes.  (As someone wrote above [in this thread], don't pretend to know things you don't know.)

20
Antarctica / Re: Thwaites Glacier Discussion
« on: November 26, 2019, 01:16:44 AM »
I have overlaid a recent bathymetric chart over a Sentinel-1 radar image of B22-A from November 21, that shows the iceberg is probably grounded in two locations.  In the West and a large shallows area and in the East on a smaller peak.  Both are higher than 300 meters below the surface.

When looking at movements of B22-A it should be useful to have these reference points in mind.  I will make another post detailing the recent movements of B22-A, but as a first pass the iceberg seems to be pivoting on the Western shallows and the Eastern end is rotating counter-clockwise to the North.  This means that it is moving over the Eastern Peak, but it far from moving off the peak.

I note that the trough under the middle of B22-A means that is the most likely place for basal melting and the possibility of the iceberg splitting into two pieces has to be considered.

Millan 2017: "Bathymetry of the Amundsen Sea Embayment sector of West Antarctica from Operation IceBridge gravity and other data"
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL072071

21
Antarctica / Re: PIG has calved
« on: November 25, 2019, 08:28:10 PM »
Blumenkraft,

1.   If the rift widens "quickly" and the middle surface is sufficiently rigid being frozen, then inevitably there are open waters parallel to the edges of the rift (what shows the gif, post 1213)


2.   On the other hand, a current that creates open water tends normally to create them orthogonal to the movement of water

22
Antarctica / Re: PIG has calved
« on: November 25, 2019, 07:38:32 PM »
Greetings from Germany Stephan

Grüsse aus dem Pfälzer Wald zurück! ;)

23
Science / Re: 2019 Mauna Loa CO2 levels
« on: November 25, 2019, 05:58:07 PM »
Impressive video! But not the good way...  :-[

Carbon Dioxide Pumphandle 2019


24
Antarctica / Re: PIG has calved
« on: November 24, 2019, 12:50:50 PM »
And the middle.

25
Antarctica / Re: Thwaites Glacier Discussion
« on: November 23, 2019, 11:32:07 PM »
I'm glad you knew, Stephan.  I've been sick and didn't have the energy to point to Baking's reply to my earlier surmise clarifying all that.
Cheers (even if subdued!),
Tor

26
Antarctica / Re: Thwaites Glacier Discussion
« on: November 23, 2019, 03:45:18 PM »
For those that like natural color images, here is a 10-day movement of the Western Tongue Rift between November 12 and 22.

27
Antarctica / Re: PIG has calved
« on: November 19, 2019, 12:40:29 AM »
Supplements on PIG changes between 03/11 and 17/11

28
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 09, 2019, 06:46:53 PM »
http://psc.apl.washington.edu/zhang/IDAO/multi.html
Animation of ASI Thickness out to 2050 by Dr. Zhang at Polar Science Center.  Shows first BOE by the 1m km2 definition around 2032 (eyeball estimate) with some recovery years in mid-2030s.  By 2040 September min is essentially a BOE every every year and August almost as low.  By 2046 August is at or near BOE every year.  Still plenty of Extent into July even by 2050.

The page and animations are not dated.  Because they use an older emissions-warming scenario (B2) and start future projections in 2005  I assume they were created before the most recent full IPCC reports in 2013-14 (which used RCP scenarios), and probably been created ca. 2004.  A lot has happened since then.  But the animations are still interesting to watch if only too see what state of the art was at that time.

    The files ran on Windows Media Player when viewed through Google Chrome browser over home wifi.  For unknown reasons I could not view  with Firefox. First time through it had some long pauses.  Playing through 2nd time is smoother.  If you are quick with the mouse you can stop and view any single month as freeze frame.

29
Antarctica / Re: PIG has calved
« on: November 08, 2019, 09:55:53 PM »
I wanted to do a movement analysis in the current joint between PIG and SWT.

The results clearly show the play of the pressures between PIG, SWT and the three pieces of the SSI forming the join between PIG and SWT, which lead these three pieces to strong deformations, and, in the case of piece 3 ("Cork"), to calving’s and to turn (which caused an acceleration in the movement of the corresponding part of the PIG that generated the recent mini-calving

Attached to this post:

1.   The image of 03/11/2010 with general notations for existing elements (in red), join limits (orange), main actions: deformations, compressions, rotations and update with the mini-calving of 06/11

2.   Always the image of 03/11 with indications of movements between 24/10 and 03/11 (10 days). For each position tested I circled with a circle the area containing the points tested (for each position I measured the displacement of several points to check the consistency of the measurements; normally 2 or 3). I also measured changes in the distance between two points straddling the PIG rift

3.   The image of 31/01/2019 with the notations relating to the current join (this image clearly shows the deformations that have occurred since 31/01)

30
Science / Re: Trends in atmospheric CH4
« on: November 08, 2019, 12:20:25 AM »
There are plenty of other sources so that is only part of it.

31
Science / Re: Trends in atmospheric CH4
« on: November 08, 2019, 12:05:23 AM »
Data from Barrow, in the high Arctic. This year shows a 50 ppb increase.

So that might be where the global acceleration comes from.
Source: https://www.esrl.noaa.gov/gmd/dv/iadv/graph.php?code=BRW&program=ccgg&type=ts

32
Antarctica / Re: PIG has calved
« on: November 07, 2019, 01:32:13 PM »
I pulled all the high resolution Sentinel-1 images I could get.  I have a bunch from late March through late June then there is a four month gap and a new set in the last 30 days with the most recent being from today.  I made them into a GIF below and I have labeled today's image with the significant features.

I think the most significant observation is the new rifts forming on the glacier side of the shear margin.  Presumably they are forming after the glacier passes the submerged ridge.  Two have formed in the last year or so.  These are important because they are moving with the glacier and if they continue to form and move along they will weaken more and more of the northern shear margin causing continued acceleration of the glacier.  (This is what happened on the southern shear margin beginning in 1999 and the rifts there have almost reached the ice front.)

What I am call thing the Northern Ice Shelf "Pocket" is a roughly triangular shaped shelf that is not attached to the rest of the Northern Ice Shelf.  It is bordered by the Pine Island glacier to the South, the Hudson Mountains to the North, and a submerged ridge to the East.

The new crevasse (I hesitate to call it a "crack") is probably a transverse crevasse caused by movement of the ice shelf off of the ridge.  Whether this movement is faster than normal is hard to say.  The important point is that the crevasse is relatively stationary and not moving with the glacier.  Yes the shelf does provide support for the glacier, and weakening of the shelf does imply further weakening of the glacier, but I find the spreading of the rifts along the margin to be a greater concern.


33
Antarctica / Re: PIG has calved
« on: November 07, 2019, 09:28:27 AM »
That's the correct location, Stephan! Thanks for pointing it out.

Sorry for not being detailed enough, Baking.

Here is a GIF showing the supposed Sentinel grounding line.


https://m.imgur.com/ha91dZW

34
Antarctica / Re: PIG has calved
« on: November 04, 2019, 09:35:49 PM »
Oh cool! Thanks for the hint, Stephan.

Here is for comparison as GIFs.

Click to play.

35
Antarctica / Re: PIG has calved
« on: October 25, 2019, 01:07:02 AM »
PIG : the northern rift is joining the southern rift, 1.5 kilometer to join.
Images of Sentinel of 09/14 and 10/24

36
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: October 20, 2019, 10:20:36 AM »

Thanks Stephan - timely reminder....


I think there is something to be said for viewing the melt and later freezing as being behind / ahead x days. 


Most of the statistics are km2 above / below average / record - whereas maybe a good way of looking at it is that we are 10 /31 days behind in the freezing  compared to average - and will probably have 10 /31 days "less" freezing as a result.


37
Antarctica / Re: Potential Collapse Scenario for the WAIS
« on: October 18, 2019, 08:01:06 AM »
The findings of the linked reference imply that current ice shelf models err on the side of least drama with regard to ice mass loss associated with relatively warm ocean water beneath such ice shelves, as illustrated by measurements from the Getz Ice Shelf in West Antarctica:

Rippin, D. M.: Significant submarine ice loss from the Getz Ice Shelf, Antarctica, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-163, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2018-163/
New calving at Getz, short gif at link
http://www.esa.int/spaceinimages/Images/2019/10/B47_breaks_off_Getz_Ice_Shelf

38
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: October 16, 2019, 05:43:55 AM »
[ADS NIPR VISHOP (JAXA)] Arctic Sea Ice Extent.

October 15th, 2019:
     5,034,952 km2, an increase of 92,169 km2.
     2019 is the lowest on record.
     The difference versus the lowest and 2nd lowest is 350K+ km2.  :o
     (2007, 2012 & 2016 highlighted).

39
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: October 14, 2019, 01:07:44 AM »
Still you should leave those years there. Well-intentioned mods as yours can give deniers arguments as much as discussing a hiatus. The statistical tendency backed by almost 40 years is clear without needing tweaks.

Also a good and valid point but you know what?

While this will take nothing away from your reasoning (not kidding) one of the ways a denier
is distinguished from a realistic and honest thinker is, that it does not matter what we tell them.
because they DENY facts ;) ;)

In other words, your point is valid and Gero's point is valid, and the results are very close and the tendency is obvious (even without tweaks) but since a denier denies ANY valid point, there is no
point in spending a lot of time and energy to find out which of all the valid points we want to
present to a DENIER to DENY ;)

[half kidding but true nevertheless]

40
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: October 13, 2019, 08:44:10 PM »
By the way, I still think that endless discussions on what charts that use extent & area are best to predict an ice-free Arctic are a waste of time because:-
- CO2 ppm is increasing at an accelerating rate (looks like will at 3 ppm per year this year)
- There is evidence that the Carbon Sinks are not doing so well, (recent post by AbruptSLR re the Southern Ocean & some work I did on carbon sinks c.f. emissions and CO" increases),
- Global Surface ar temps at record levels in an ENSO neutral year plus scary WMO report on recent trends.

BUT - I read the NSIDC talking about a hiatus in extent loss & I think it is WRONG.. Even though they emphasise caveats & the need to look at longer-term trends, it is God's gift to the denier industry.

So here is a 2nd post about it.
____________________________________________

By why stop with your so-called exaggerated years in one direction only?  If your are going to selectively discard data points, why not toss out the high years of 2000 and 2006 also?

Indeed, why not? So I googled to refresh my hazy memory of a Uni course on Mathematical Statistics to fin the standard methodology for identification of outliers. (That course was so long ago for analysis we did it by hand on mechanical machine Babbage would have recognised.)

It got wider - seems to be a big thing in machine learning (AI ?):-

https://machinelearningmastery.com/how-to-use-statistics-to-identify-outliers-in-data/
Machine Learning Mastery
How to Use Statistics to Identify Outliers in Data

Sometimes a dataset can contain extreme values that are outside the range of what is expected and unlike the other data. These are called outliers and often machine learning modeling and model skill in general can be improved by understanding and even removing these outlier values.

- An outlier is an unlikely observation in a dataset and may have one of many causes.
-Standard deviation can be used to identify outliers in Gaussian or Gaussian-like data.
- The interquartile range can be used to identify outliers in data regardless of the distribution.

I followed the recognised  interquartile range method using absolute deviations from the "expected" value from the linear regression used by NSIDC & me in these graphs

For NSIDC Extent it told me to dump an extra year, the very high extent value in 1996.

I did they same analysis or PIOMAS September volume, and it told me to dump 3 years, all very low values, 1981, 1982, and 2012.

The answers re all the same -
- there is barely any change from the linear regression with or without the "outlier years",
- there is no "hiatus" in the steady loss of Arctic Sea Ice extent as implied on the 3rd October  NSIDC analysis (https://nsidc.org/arcticseaicenews/)

Quote
Within the overall decline, it is notable that the most recent 13 years, from 2007 to 2019, have shown very little decline (Figure 3b). Both 2007 and 2012 were extreme low extent years, and variability has been high in this period. However, an earlier 13 year period, 1999 to 2012, shows a rate of decline that is more than double the overall rate in the satellite record. This illustrates the challenge of extracting a quantitative rate of decline in a highly variable system like sea ice, and the benefits of looking at decadal, and not year-to-year variations.

41
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: October 12, 2019, 01:06:46 AM »
… but all we have to do is wait & see (just a few years).
I definitely don't like the "wait & see". I am concerned about passing no-return points. If we look at volume, we lost almost 1/3 on 2000-2009 and almost 2/3 on 2010-2019, against the 1979-2000 average.

That is too much!

The 2007, 2012 and 2019 are outliers when you see NSIDC extent figures, but not with PIOMAS volumes. I also don't like monthly averages on extent. 2016 was a terrible year, but because it had an early refreeze, doesn't look that bad. 2017 was also a terrible year looking at volume the whole year. It was just ok around September.

IMO, 2020-2029 will be pretty bad, even if we only have 2 or 3 years like 2012. We don't need a BOE, if Greenland ice and permafrost accelerate their melt.

P.D. Of course, following the events on the ASIF, I am on the "wait & see". But I am becoming more an activist also.

42
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: October 11, 2019, 08:56:56 PM »
NSIDC appear to be a bit supportive of a "hiatus" in Arctic Sea Ice Loss.

Here is their spiel about it from Oct 3  https://nsidc.org/arcticseaicenews/ (Graph also attached)

Quote
Within the overall decline, it is notable that the most recent 13 years, from 2007 to 2019, have shown very little decline (Figure 3b). Both 2007 and 2012 were extreme low extent years, and variability has been high in this period. However, an earlier 13 year period, 1999 to 2012, shows a rate of decline that is more than double the overall rate in the satellite record. This illustrates the challenge of extracting a quantitative rate of decline in a highly variable system like sea ice, and the benefits of looking at decadal, and not year-to-year variations. Our updates to our public analysis tool, Charctic now allows the user to see the decadal average trends as well as each year (Figure 3c).

Who am I, a mere observer to disagree - but I do...

Evidence 1
Let us assume that 2007 & 2012 are outliers - i.e. caused by a combination of climatic occurrences that converged to produce the maximum possible ice loss at that time. If so, it is legitimate to exclude those years from the data.

The result  (see graph attached, that has both sets of data, i.e. with & without 2012 and 2007),
- a far more orderly progression in a downwards direction.
- no real sign of a hiatus
- a slightly better linear trend R2 value.,
- average annual loss reduced by 5k (82 to 77k)

Note well:- all I did was tell the spreadsheet to make the graphs & add the trend lines. No manipulation by yours truly

Evidence 2
All the data now indicates that the October Average is likely to be a record low, even if area and extent gain revert back to average levels.

Evidence 3
There is likely to be a new record low 365 day average in early to middle 2020

So my statement that belongs to me is that 2007 and 2012 distort the trends to the extent that they create the illusion of a hiatus where none exists..



43
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: October 09, 2019, 03:57:32 PM »
     Thanks Stephan.  A zero Arctic sea ice volume date for September, and shortly thereafter for August and October has been on my radar for a long time from the Wipneus and your earlier graphs. 
 
      But zero ASI volume-in-July estimates of 2034 (linear) or 2038 (log) are shocking to even my jaded eyes.  Yikes.  The albedo impact of losing ice coverage in July is much greater than August and very much greater than September.  Actually, the whole situation is shocking, but we just get used to the evolving catastrophic trends as a new abnormal.  If that zero Arctic sea ice estimate in July date is anywhere near accurate then we are in big trouble sooner than previously realized.  Remember, you can't have Extent or Area without Volume, so 0 Vol in 2034/2038 also = 0 Ext. 

     FWIW, the September 2019 IPCC cryosphere report shows Extent becoming asymptotic at about 10% of the 2000 level around 2070. 
https://report.ipcc.ch/srocc/pdf/SROCC_FinalDraft_FullReport.pdf
     
     Given the length and detail of the IPCC cryosphere report, there is a surprisingly brief discussion of Arctic sea ice trends.  ASIF is a better source than IPCC! (seriously). After a quick search, I found nothing in the IPCC report about ASI volume projections.  Figure 3.3 on page 3-13 is the closest information.  It charts ASI Extent under the RCP scenarios.  In those projections, even the RCP8.5 scenario retains 10% September Extent for 2070-2100. 

      The scientists who donate their hard work to IPCC reports are the experts and I feel like an ungrateful flea telling the dog what to do in critiquing their work.  But my small fevered brain is unable to reconcile the trends charted by Wipneus and Stephan, or that I can see for myself in the data from PIOMAS, with the IPCC statements shown below from page 3-25.  To be blunt, I suspect that the IPCC is under-estimating the severity of the ASI trends.  If that were in fact the case, it would almost certainly be due to the political (in addition to scientific) consensus required before IPCC reports are released.  But let me not digress into conspiracy theory.  Here is the gist of what the IPCC Cryosphere report has to say about the expected future ASI:

      "There is a large spread in the timing of when the Arctic may become ice free in the summer, and for how long during the season (Massonnet et al., 2012; Stroeve et al., 2012a; Overland and Wang, 2013) as a result of natural climate variability (Notz, 2015; Swart et al., 2015b; Screen and Deser, 2019), scenario uncertainty (Stroeve et al., 2012a; Liu et al., 2013), and model uncertainties related to sea ice dynamics (Rampal et al., 2011; Tandon et al., 2018) and thermodynamics (Massonnet et al., 2018). Internal climate variability results in an uncertainty of approximately 20 years in the timing of seasonally ice-free conditions (Notz, 2015; Jahn, 2018), but the clear link between summer sea ice extent and cumulative CO2 emissions provide a basis for when consistent ice-free conditions may be expected. For stabilized global warming of 1.5°C, sea ice in September is likely to be present at end of century with an approximately 1% chance of individual ice-free years (emphasis mine) (Notz and Stroeve, 2016; Sanderson et al., 2017; Jahn, 2018; Sigmond et al., 2018); after 10 years of stabilized warming at a 2°C increase, more frequent occurrence of an ice-free summer Arctic is expected (around 10-35%) (Mahlstein and Knutti, 2012; Jahn et al., 2016; Notz and Stroeve, 2016)."

    They do say elsewhere in the report that CMIP5 models have relatively poor ability to recreate Arctic sea ice behavior.  The new generation of CMIP6 models are coming out and have improved capabilities.  It will be interesting to see what they have to say about ASI projections.  So far the only statements I have seen on output from the few CMIP6 model results being reported is that they (i.e. the multiple new component models of the new CMIP6 set) are consistently showing greater sensitivity of global surface temperature to rising CO2 levels than the CMIP5 estimates. 

       None of this bodes well for the ASI, or for human civilization unless we finally take heed and respond to the crisis with the intensity and commitment it requires.  Make your support for any politician explicitly contingent on their climate policy.  Talk about it even if you annoy people by doing so.  Vote climate as if your life depended on it.  Because it does.

44
Arctic sea ice / Re: Latest PIOMAS update (October 2019)
« on: October 06, 2019, 10:15:12 AM »
Here is the exponential fit. The 2019 minimum is above the trend, shifting the extrapolated zero ice after  2025 where with only data up to 2018 it was 2014.

45
Antarctica / Re: Thwaites Glacier Discussion
« on: October 06, 2019, 01:47:58 AM »
Spoiler Alert!

Do the exercise in the above post first to see if you come to the same or a different conclusion than I do.  I have identified the approximate locations of four potential peaks in the picture below.  They are in order of importance.  Only the first two can be identified from the 4-year GIF, but the second one may be hard to pick out without knowing where it is.  The other two, lesser peaks, can be detected from a close viewing of the last eight months of Sentinel images.

1.  The iceberg currently at this location has been grounded for over a year, going back to September 2018.  With all the movement and chaos going on around it, that berg has not budged one bit.  The only possible explanation is a fairly high peak under it, which it is currently grounded on.  Before that time, the peak was probably responsible for causing two separate rows of icebergs to break away from the Western side of the Tongue in 2017 resulting in a substantial narrowing of the Tongue.

2.  A peak at this location is beginning to have a larger effect.  When Iceberg B-22A shifted during Sept. 22-26, the sea ice between it and the Tongue moved with it, along with the tip of the Tongue causing the rift Stephen has labeled in blue.  The most likely explanation is that this was built up compression from the Tongue during the Southern Hemisphere winter pushing against the thicker sea ice that was released when B-22A shifted.  The Eastern side of the Tongue expanded more naturally and pushed the rest of the tip to the North while the Western side of the Tongue was held by by Peak 2 causing the rift just to the North of it.

Peak 2 is also probably responsible for Stephen's red rift to the South that may cause a further narrowing of the Tongue in the near future.  There is a second parallel rift forming next to it which may also come into play.  The actual motion of the Tongue is shown roughly with the white arrow.

Peaks 3 and 4 are shown for completeness.  I don't expect either one to have a substantial effect on the Tongue going forward.

3.  The thicker of the two icebergs off the Northwestern corner of the Tongue has apparently been grounded ever since it broke off from the Tongue, but it is most likely about to float free since it has almost passed over it's original grounding point.  Its narrower companion berg does not seem to be grounded, but only sheltered by the other one.

4.  A peak can be detected here from the splitting of icebergs as they pass over it.  There is no sign that they are grounded enough to affect the movement of nearby icebergs.

46
Antarctica / Re: PIG has calved
« on: October 05, 2019, 05:04:25 PM »
OT:
Did you recognize that B-22-A has turned backwards in NE direction the last days? It seems to be flowing freely now without pinning points. Hope it can escape into deeper seas to give room for new icebergs from Thwaites.

This is a good catch.  Movement to the West (or NW) is "good" because it means the iceberg is becoming grounded again.  This is pretty much what it has been doing every few months lately.  Movement to the East (or NE) is "bad" because that is movement towards deeper water and possibly floating free (or at least farther away.)  It bears watching.

Of course, an iceberg of this age, condition, and size could also breakup under the stresses of being grounded, regrounded, and pushed by wind and currents.  Floating off intact seemed like the least likely scenario.

47
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 02, 2019, 08:29:41 PM »
I wasnt aware (until today) that the old Norwegian Met Ice Service and charts, previously available at http://polarview.met.no/ (url no longer works) are now available in a new revamped website at:

https://cryo.met.no/en

I've just perused through this site and it is a treasure trove of charts and data. ASIF members, bookmark it ! 

Maybe mods would like to add it to the ASIG section ?

Here is a sample of some of the images available on the website  (Mosaic view of Sentinel 1 images) :

https://cryo.met.no/sites/cryo.met.no/files/latest/SAR-mosaic-latest.png

48
Arctic sea ice / Re: September predictions challenge 2019
« on: October 02, 2019, 06:34:42 AM »
Congrats, Stephan!! \o/

49
Arctic sea ice / Re: September predictions challenge 2019
« on: October 02, 2019, 01:32:32 AM »
Hope all the calculations are ok.
(Let me know if there is a correction to make ;) )

50
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: September 30, 2019, 05:48:01 AM »
September 28th, 2019: 4,344,557 km2, an increase of 33,789 km2.

(have fun at the wedding, Juan :) )
Thanks Blumenkraft and Stephan for your posts.  :)

[ADS NIPR VISHOP (JAXA)] Arctic Sea Ice Extent.
September 29th, 2019:
     4,371,624 km2, an increase of 27,067 km2.
     2019 is still?  ;) 3rd lowest on record.
     (2007, 2012 & 2016 highlighted).

Pages: [1] 2 3 ... 6