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Messages - Stephan

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1
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.

2
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)

3
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.

4
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

5
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.


6
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

7
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.

8
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

9
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.


10
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

11
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).

12
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]

13
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.

14
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.

15
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..



16
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.

17
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.

18
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.

19
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.

20
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

21
Arctic sea ice / Re: September predictions challenge 2019
« on: October 02, 2019, 06:34:42 AM »
Congrats, Stephan!! \o/

22
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 ;) )

23
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).

24
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: September 29, 2019, 09:35:59 PM »
Couldn't agree more, Stephan!  :D

26
Antarctica / Re: Thwaites Glacier Discussion
« on: September 27, 2019, 06:10:19 AM »
Here's a final image scaled down by a factor of 8.  A tiny portion of B22-A can be seen at the bottom edge of the image.  The movement of sea ice over a vast region, along with isolated icebergs, iceberg formations, and a huge iceberg almost the size of Rhode Island cannot be a mere coincidence.

Ocean currents and/or wind had to have been the moving force, but the shifting position of B22-A must have allowed the sea ice behind it to follow along bringing smaller icebergs and formations with it.

It also raises the question of whether the fate of Thwaites Ice Tongue can be tied to Iceberg B22-A.  If B22-A were to ever unground and drift off, would the ice tongue become even more vulnerable?

27
Arctic sea ice / Re: meaningless freezingseason/melting season chatter.
« on: September 25, 2019, 03:31:06 PM »
🌍🔥  New #IPCC #ClimateChange report released today: "IPCC Special Report on the Ocean and Cryosphere in a Changing Climate" #SROCC

Press release: https://ipcc.ch/2019/09/25/srocc-press-release/

Full Report, & Summary for Policy Makers: https://ipcc.ch/srocc/chapter/summary-for-policymakers/ 🔥🌍

28
Arctic sea ice / Re: Accuracy of poll predictions
« on: September 22, 2019, 09:41:16 PM »
The JAXA extent minimum for 2019 was 3.96 million km2.

Here is an updated graphic, showing the distribution of the votes in the June polls for JAXA extent on this forum in the past few years.  The correct bin for each year is indicated with a fluo green background.




People on this forum tend to vote too low in the polls.  But the results this year were pretty good, especially compared to previous years.

The July and August polls were a bit worse than June this year:  The median of the votes in the June 2019 poll was 3.73 million km2, in the July poll it was 3.51 million km, and in the August poll it was 3.64.

---

Caveat: note that the format of these polls changed in 2018:

(1) From 2018 onward, the polls had overlapping bins of width 0.5 million km2, whereas in previous years the polls had bins of width 0.25 million km2.  For consistency with previous years, I split each of the overlapping bins in two equal halves and distributed the votes in the bin evenly over its two halves.

(2) The lowest bin in the 2019 poll was labeled "Under 2.00 million km^2".  I decided to treat this bin as 1.5-2.0.  Similarly, the 2018 poll had a lowest bin around 2.5-3.0.  In contrast, the 2017 and 2016 polls had bins all the way down to 0.

29
Antarctica / Re: What's new in Antarctica ?
« on: September 17, 2019, 08:29:55 PM »
Emperors on thin ice: three years of breeding failure at Halley Bay

https://www.cambridge.org/core/journals/antarctic-science/article/emperors-on-thin-ice-three-years-of-breeding-failure-at-halley-bay/4CA1A77971A4CD5D5CB823EBF338FAA9/core-reader


Abstract

Satellite imagery is used to show that the world's second largest emperor penguin colony, at Halley Bay, has suffered three years of almost total breeding failure. Although, like all emperor colonies, there has been large inter-annual variability in the breeding success at this site, the prolonged period of failure is unprecedented in the historical record. The observed events followed the early breakup of the fast ice in the ice creeks that the birds habitually used for breeding. The initial breakup was associated with a particularly stormy period in September 2015, which corresponded with the strongest El Niño in over 60 years, strong winds, and a record low sea-ice year locally. Conditions have not recovered in the two years since. Meanwhile, during the same three-year period, the nearby Dawson-Lambton colony, 55 km to the south, has seen a more than tenfold increase in penguin numbers. The authors associate this with immigration from the birds previously breeding at Halley Bay. Studying this ‘tale of two cities’ provides valuable information relevant to modelling penguin movement under future climate change scenarios.

Introduction
The emperor penguin (Aptenodytes forsteri Gray) colony at Halley Bay (75°33′S, 27°32′W) was one of the largest colonies in Antarctica, second only in size to that at Coulman Island in the Ross Sea (Fretwell et al. 2012). The colony is located on the northern side of the Brunt Ice Shelf (Fig. 1) and, for the past two decades, has been situated in a bay, locally named ‘Windy Creek’. Although no organized science has been conducted on the colony, it has been visited by staff from the Halley Research Station sporadically from 1956–2012 and estimates of size vary between approximately 14 300–23 000 pairs (Woehler 1993, British Antarctic Survey (BAS) unpublished data, H.J. Gillett personal communication 2018). It is likely that the colony is associated with foraging on the shallow McDonald Bank and McDonald Ice rumples, to the north and east of the site and the coastal polynya that forms north of the Brunt Ice shelf each summer season (Hodgson et al. 2018). Although this polynya is a consistent feature, the sheltered bays bordering the ice shelf usually retain fast ice until December and often the ice remains all summer. This ensures that emperors are able to raise their chicks at the site as their young fledge between mid-December and early January.


Fig. 1. Overview of the Brunt Ice Shelf, showing the location of Halley Bay and Dawson-Lambton emperor penguin colonies. The underlying image is a Landsat8 image from October 2016.

Although the recorded population has varied, the colony is consistently the largest in the Weddell Sea, over twice the size of any other colony in the region. There have been no previously recorded instances of total breeding failure at the site. It possibly represents 6.5–8.5% of the total global population and, as it is situated at high latitudes, it plausibly represents an important climate change refugia (Ainley et al. 2010, Jenouvrier et al. 2017).
The nearest colony to the Halley site is the Dawson-Lambton colony, some 55 km to the south, located where the Brunt Ice Shelf joins the continental coast (Fig. 1). Geographically this is an unusually small distance between emperor colonies (Ancel et al. 2017). Only the Mertz Ice Shelf colonies have a smaller distance between them, and these two colonies originated from a single site before the recent calving of the Mertz Ice Tongue in 2010 (Ancel et al. 2014).
However, recent monitoring has shown that the Halley Bay colony has suffered catastrophic breeding failure, whilst the nearby Dawson-Lambton colony has markedly increased in size. In this paper very high resolution (VHR) satellite imagery is used to estimate population changes at the two sites over the last ten years.

The exact number is difficult to estimate due to the rough ice surface confusing the automated image analysis. The best estimate is that around five times more birds were at, or within ~100 m of the sea-ice edge than at the main colony site. Many of the penguins were on refrozen brash ice or newly formed grease ice. This does not include the lines of birds moving between the colony site and the ice edge, which can easily be identified as birds in transit. Emperors do not breed or habitually feed their young at the ice edge as its position is dynamic and the high risk of breakup would pose a danger to unfledged chicks. Whether the adult birds here were failed breeders or non-breeders is difficult to assess from imagery alone. Subsequent Landsat8 and Sentinel2 imagery shows that by 29 November 2018, all of the fast ice on the north side of the Brunt Ice Shelf had gone, highlighting a third year of probable total breeding failure. These assumed failed breeding events are of a scale that is not apparent in the long, but sporadic record from the site (H.J. Gillett personal communication 2018, BAS records).


Fig. 2. Variability in the emperor penguin population breeding at Windy Creek, Halley Bay (solid line), and Dawson-Lambton colony (dashed line). Estimates made from very high resolution satellite imagery following the methods of Fretwell et al. (2012); upper and lower 95% confidence intervals are shown.

Understanding how environmental drivers, such as changes in SAM, sea ice, or wind speed, direction and velocity, impact upon the breeding colony at Halley, or indeed elsewhere, remains a key challenge. Further, exploring how extremes of such events lead to breeding failure is vital for projecting future population trajectories in a warming environment. The relationship between climate change and El Niño events, or positive SAM anomalies is still a matter of active research (Trenberth & Hoar 1997, Turner 2004, Turner et al. 2005, Yeh et al. 2009, Collins et al. 2010, Bracegirdle 2013, Cai et al. 2015). Recent research suggests that the frequency of El Niño and La Niña events are predicted to increase, while ENSO-related catastrophic weather events are also likely to occur more frequently with unabated greenhouse gas emissions (Cai et al. 2015). However, other evidence cautions that it is not yet possible to say whether ENSO activity will be enhanced or damped, or if the frequency of events will change (Collins et al. 2010). The evidence from observations of the present authors, and from earlier papers (Kooyman et al. 2007, Ancel et al. 2014), points to the fact that stochastic impacts upon emperors may be vital, even for high-latitude locations. Strong winds, or storm events can create coastal leads or polynyas that are beneficial to foraging, but prolonged periods of extreme winds can also lead to breakup and dissipation of fast ice, which can cause total breeding failure when it occurs at a sensitive time for the penguins.
At Halley, another important factor influencing the stability of the fast ice around the colony could be the dynamic nature of the creek in which it is located. Until recently, the colony was situated within a sheltered ice creek, on the northern side of the Brunt Ice Shelf, informally named Windy Creek. Over the past 60 years, the colony has occasionally moved to other adjacent sheltered creeks (H.J. Gillett personal communication 2018, BAS records). With the fast-ice breakout in 2016, ice shelf morphology changed (Fig. 3) and the resulting more open nature of the creek may now be less suitable for fast-ice retention. The Brunt Ice Shelf is a fast-moving and dynamic environment (Hodgson et al. 2018). Over the last two decades the creek has gradually moved westwards by over 600 m per year and it is possible that the migration and changing topography of Windy Creek has made it a less favourable site for emperor penguins. Any future breeding at Halley will almost certainly depend upon the juxtaposition of sheltered, stable fast ice, foraging opportunities, including over the nearby McDonald Bank, and the longer-term processes that will happen once the Brunt Ice Shelf calves, which at present rates will be within the next two years.


Fig. 3. Medium resolution satellite imagery of the Windy Creek breeding site for the years between spring 2015 and spring 2018.

Conclusion
The authors describe an unprecedented three-year period of breeding failure at the large Halley Bay emperor penguin colony. They link this to a dramatic rise in the population of the nearby Dawson-Lambton colony, a rise that can only have occurred due to immigration from Halley. These changes have been driven by a change in sea-ice conditions and early breakup of fast ice on the northern side of the Brunt Ice Shelf, which may be due to ENSO events and/or ice-shelf morphology.
In a warming world, it will be crucial to better understand the interplay between wind and ice shelf orography, and to appreciate how these factors impact the location of emperor penguin colonies. Understanding how emperor penguins react to catastrophic sea-ice loss will be of crucial importance if one is to predict the fate of the species over coming decades.

bligh


30
Science / Re: 2019 Mauna Loa CO2 levels
« on: September 08, 2019, 09:35:04 PM »
^^
Thanks for the posts!
Terry

31
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 08, 2019, 07:21:13 AM »
      FWIW, the Wipneus linear PIOMAS volume trend chart at
https://sites.google.com/site/arctischepinguin/home/piomas
suggests that by 2029 any individual year would have a 50% chance, by 2032 an 84% chance, and by 2036 a 97.5% chance, of going below 1 million km3 by the end of melt season.

     Given the argument that last phase of CAB will be the toughest to melt out, it would be interesting to graph CAB minimum volume over the years (or is such a graph already posted here and I missed it?).  That eliminates the influence of the peripheral sea contributions that could inflate loss rate relative to rate when the remaining late season ice is limited to CAB.  But it would also remove the effect of that ice in those peripheral seas has provided to protect CAB ice from open water melting effect (I think, not too sure about that).  Therefore, CAB rate of loss could increase once it loses that surrounding ice earlier in the melt season.

     The argument that the final CAB ice is at higher latitude does not seem to completely apply because the end of season CAB ice is not centered around North Pole, but is centered at lower latitude of triangle between NP, northern Greenland and northern edge of CAA. 

     Way above my knowledge, but my gut says that reinforcing feedbacks of wave action, open water albedo decline, fractured ice, increased exposure of remaining ice to transport currents, winter cloudiness or other factors giving weaker refreeze seasons, increasing SST (and with it increasing chance of GAC), and of course the ever increasing GHG levels in the atmosphere and monotonic warming-- esp. as 2 year lag in currently bottomed-out solar cycle starts to push temperatures up starting around 2023 -- will take a toll on the ice.  And by the late 2020s ENSO cycle could be trending towards El Nino phase adding even more push to surface warming (though I have no idea how surface air temperature effects from ENSO relate to SST and impact on ASI.  But at least it gave me an excuse to use 3 acronyms in the space of 8 words).   The point is, all those feedbacks working together seem likely to be more than enough to overwhelm any increased resistance of the final CAB core to melt. 

     And I suspect that measurement errors introduced by higher percentage of "rotten ice" are inflating reported extent values and thus suppressing the more recent rate of decline.  The remaining CAB doesn't look like a resistant pack, just a bunch of aggregated chunks.  All pure conjecture of course.

   The NASA animation up thread shows the Pacific side of ASI being an overwintering stronghold of MYI before 2007, taking a big hit in 2007 but recovering, taking another big hit in 2012, but coming back a bit in 2013-2015, then taking a third big hit in 2016 and not coming back after that.  Of course 3 years may be too short to say it won't come back, but with the one way trend of lessening ASI I doubt it will.  The loss of the Beaufort nursery seems to be a functional system change with major impact.  The MYI chart updated next spring could bring dramatic news on the MYI story, showing the virtual extinction of the oldest categories.

   Extent is declining less rapidly than Volume, but eventually will have to catch up it as both get closer to zero for September minimum (because 0 Volume forces 0 Extent).  Given the difference in trends between Ext. and Vol., it is important to specify which is being referred by BOE, though I guess the "official" definition is Extent.  By the time Volume gets close to 1 million km3, Extent should have mostly caught up, though I can also imagine a future with almost all FYI that by end of melt season still has large Extent but is approaching zero thickness and thus zero volume. 

    Even though 2019 is falling into 3rd or maybe 4th place for Extent, it is a solid second place for volume and will likely finish only about 200 km3 and about 5% above 2012 (and slightly below the Wipneus straight line trend).   As for 2019 Extent minimum, it is not over until the fat lady sings, and while she is standing close to the exit, she is still on stage. Given high SST and recent/forecast weather, a late finish such as 2007 looks very possible.   

32
Arctic sea ice / Re: The 2019 melting season
« on: September 07, 2019, 02:42:51 PM »
After spending four months at well above records, global ice has fallen to last year's levels definitely reflecting the recent slow down and up-tick in the north.  Speculation... are we to assume the 'original' global ice max would have been prior to man???  The CAB, not near to the coast is well able to survive recent extremes and it will take a definite step change (rain/export/blowtorchestothenth).  I don't think it matters much as we will not survive the weather as it is let alone the possibilities if it gets any worse...?!

33
Antarctica / Re: Thwaites Glacier Discussion
« on: September 04, 2019, 08:22:11 AM »
The Schroeder paper on Thwaites is interesting.

doi: 10.1073/pnas.1821646116

"In contrast to the stability of the FRIS basal channel, a similar comparison between a 1978 SPRI profile from the Amundsen Sea Embayment (ASE) of West Antarctica with 2 2009 Operation Ice Bridge (OIB) radar-sounding profiles (27) reveals dramatic changes in the subsurface geometry of the remnant eastern ice shelf of Thwaites Glacier, West Antarctica (Fig. 10), which we refer to hereafter as the Thwaites Eastern Ice Shelf (TEIS). In general, the TEIS begins to float seaward of a potentially stabilizing inland ridge and regrounds on an offshore ridge (28)(Fig. 10). The TEIS currently buttresses a portion of the ASE grounding zone along the Walgreen Coast, which is the boundary between Thwaites Glacier and Pine Island Glacier, 2 of the most rapidly changing and potentially unstable glaciers in Antarctica(2, 29). This ice shelf was previously dynamically coupled to the faster-flowing tongue of Thwaites Glacier. However, after 2006, the section connecting the ice shelves collapsed, leading to divergent flow histories (29, 30). This dynamic event caused TEIS to become the only portion of the ASE with decelerating ice flow, in part due to the portion grounded on an offshore ridge(28). "

"By comparing the thickness of the floating and the regrounded portions of the iceshelf interpreted in the radargrams (Fig. 10), we estimate that TEIS lost∼115±62 m of ice thickness (∼10–33%) from 1978 to 2009 (Fig. 10E)(Methods). This contrasts with the regrounded portion of the shelf, which appears stable within our uncertainty estimate (∼19±43 m) (Fig. 10F) over the same period (Methods), suggesting that basal melting rather than dynamic thinning may be the primary cause of the observed thickness change in the floating portion of TEIS. "

"These results suggest that the reduced ice velocities of TEIS during the past decade will not serve to stabilize the Walgreen Coast (29), but instead the TEIS will undergo further thinning and unpinning (28) that could act to destabilize the rest of the ice shelf in the coming decades."

sidd

35
Arctic sea ice / Re: The 2019 melting season
« on: August 29, 2019, 12:41:32 PM »
As there is some discussion about ice drift direction, here is osisaf ice drift overlaid onto unihamburg amsr2-uhh, aug18-28.
Arguably amsr2 should be overlaid onto the previous 2 day osisaf but 1 pixel of amsr2, ~15km^2 of slush probably has a fair bit of inertia so in this case day n-2 to dayn osisaf is overlaid onto dayn amsr2-uhh(25-27aug onto 27aug)
Note that although both products use algorithms to interpret the data, both are based on real data and not models.

Quote
Low Resolution Sea Ice Drift product (OSI-405)

Which satellite sensors are processed?
The sensors and channels used are SSMIS (91 GHz H&V pol.) on board DMSP platform F17, ASCAT (C-band backscatter) on board EUMETSAT platform Metop-A, and AMSR-2 on board JAXA platform GCOM-W.

What is the spatial resolution of this product?
The low resolution sea ice drift product is a gridded dataset. The grid has 62.5 km spacing on a Polar Stereographic projection mapping. Definitions for the projection parameters can be found in the NetCDF files as well as in the Product User's Manual.

What is the time-span of this product?
Two days (48 hours). This is the time delay between the start and the stop time of the motion described by one vector. For comparison, the merged products from IFREMER/CERSAT is a 3 days lag dataset while the AMSR-E product by the same data centre is 2 days (using 89 GHz channels).

Several datasets are distributed every day, which one should I use?
The OSI SAF low resolution sea ice drift product is indeed composed of several single-sensor products and one multi-sensor analysis, every day. They are all at the same spatial resolution , on the same grid and with a 48 hours time-span.

The multi-sensor (aka merged, multi-oi) is intended for users requiring a spatial covering dataset. In this product, missing vectors are indeed interpolated from the neighbours and each vector is computed from the individual single-sensor products. In this merging process, however, some level of aliasing and averaging is to be expected that slightly degrade the quality of the dataset.
click to run

36
Glaciers / Re: Barnes Ice Cap / Penney Ice Cap
« on: August 25, 2019, 01:19:07 AM »
Here is a high resolution Sentinel 2 animation of the retreat in the northern part. From Aug 2016 to Aug 2019 retreat ranges from about 50m on land to 130m in the lake. Or 16.6m/yr and 43.3m/yr.

Assuming a 33m/yr melt rate for the widest part it would take 750 years for the ice cap to melt away.

37
Science / Re: Global Forest Watch
« on: August 19, 2019, 06:13:14 PM »
Yes.

The initial quote said trees planted in India but India is rather big. UP is about as big as the UK.

Its a bit like Wales planting millions of trees and then saying the UK did so.

I think Stephan wants to know how meaningful that number is and in that case it would make sense to look at the trees cut in UP.

We won´t get that number because no one uses that metric or actually counts the trees.
We usually look at forest cover. Trend is slightly positive overall for 2015 to 2017.

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

And i think this will actually be repeated and be done in other Indian states as well because it is rather easy to do. I have read other reports on tree plantings there but they were smaller so i never considered posting them.

Actually people plant trees all over the world but it should be much more important to preserve old growth forests where we not just lose trees but the other plants and animals that evolved with them. Of course we are doing badly at that...

38
Arctic sea ice / Re: Sea Ice Melting Affected by Microplastics?
« on: August 15, 2019, 06:17:18 PM »
indeed .. today's bbc news of Greta setting sail to the Americas was followed by news of 10'000 particles of plastic per dissolved litre of 'pristine' Arctic snow . Lots of rubber and other unwelcome compounds too .. b.c.

This paper is making news today.

White and wonderful? Microplastics prevail in snow from the Alps to the Arctic

Microplastics have been found in snow all the way to the Arctic, suggesting that they are much more widespread than previously thought, and that some of the ways how they are transported are still not well understood (i.e., microplastics must be airborne to make it into those places).

Open access full paper:
https://advances.sciencemag.org/content/5/8/eaax1157.full

Summary:
https://www.eurekalert.org/pub_releases/2019-08/aaft-mia081219.php

Quote from: Eurekalert
The high amounts of microplastics in snow, as reported here, suggest that atmospheric transport and deposition could represent a significant pathway for these materials to places far afield

I'm part way through reading this paper.  One thing that keeps coming up is "lack of studies about..."  Geez, this crap is way nastier than I realized. 

There didn't seem to be anything mentioned about change in albedo and heat retention changes caused by this stuff.  Per my personal observation of pieces of plastic and garbage in ice and snow causing enhanced melting near this garbage, I would certainly think this stuff would enhance melting of ice and snow and heat retention in water.  Granted, the particles are small and any one particle would have a miniscule effect, however there are such a pervasive number of these particles I can imagine that the total effect could be significant.  Tor stated upthread that reflectivity could be greater so the total effect on heat absorption and retention is a question mark.  Naturally there appears to be a "lack of information..."

39
Arctic sea ice / Re: 2019 vs 2012
« on: August 10, 2019, 01:29:48 PM »
For some Folks not uninteresting


Data: ftp://ftp.remss.com/sst/daily/mw_ir/v05.0/netcdf/ (need for registry)
Red: 2019 warmer
Blue: 2019 cooler


https://seaice.uni-bremen.de/data/amsr2/asi_daygrid_swath/n6250/netcdf/

Red: 2019 more SIC
Blue: 2019 less SIC

40
Antarctica / Re: Majestic Antarctic Images
« on: August 09, 2019, 08:17:52 PM »

41
Glaciers / Re: North Cascade glaciers Disastrous conditions
« on: August 09, 2019, 07:19:29 PM »
Massive Boulders, Floodwater Rush Down Mount Rainier After Glacial Outburst
https://www.seattletimes.com/seattle-news/environment/massive-boulders-floodwater-rush-down-mount-rainier-after-glacial-outburst/



A glacial outburst at about 6:50 p.m. Monday at the Mount Rainier’s South Tahoma Glacier sent debris and boulders as big as pickup trucks flowing down the mountain, said Mount Rainier National Park geologist Scott Beason.

The debris flow registered on seismic monitors and ran for more than 8 miles, Beason said.

Beason suspects warm, sunny weather filled the glacier with melt, rearranged the “internal plumbing” at the glacier’s base, caused water to blast a new channel through the glacier, and then flooded glacial melt into Tahoma Creek.


A glacial blowout on Mount Rainier sent debris as big as a pickup truck flowing for miles.

“The event lasted an hour and had four separate surges,” Beason said of the outburst flooding. “The outlet channel definitely shifted. It picked up a lot of loose material just below the glacier and carried it downstream and mobilized it into a debris flow.”

As the world warms and Mount Rainier’s glaciers thin and retreat over time, these massive debris flows have become a common occurrence on the mountain’s south side. The park is building systems to forecast massive debris flows and send alerts to park staff when they’re triggered, Beason said.


A view of a cavern in the terminus of the South Tahoma Glacier, from where floodwaters burst, carrying debris miles down.

The park has recorded some 32 debris flows along Tahoma Creek. The South Tahoma Glacier that feeds the creek began to retreat in the 1960s, Beason said.

42
I wonder about the grey coloured ice free spot in the lower third at the calving front. Is this a place where meltwater from underneath the glacier flows into the sea?

I am not what sure what creates these ice free spots, but will you find them reguarly at the calving front of many glaciers.

As here in Giesecke Isfjord:


This time it was a lake that emptied. See attached gif.


43
Arctic sea ice / Re: 2019 vs 2012
« on: August 03, 2019, 11:38:49 AM »
8/01/2019 = -51k
                = 5.91M km sq., a record low for the date.

8/02/2019 = -60k, or 5.85M

Daily Change to Exceed 2012 Record Daily Lows

8/03/2012 = 6.03M km sq.
8/02/2019 = Gain of < 180k km sq. required for the record.

 Call it -65k+/-10k to 5.785 (5.79).

Analysis: I don't see anything that's going to change the daily numbers much for 8/03. We've had a 40k, 50k, and 60k day in the last three days largely because, imo, the wind direction favors expansion of the sea ice, particularly in areas where concentration is low allowing for easy wind effect. That still holds: Winds coming off of the CAA and Greenland aid compaction, but there's precious little space to move with the main ice pack sitting there; winds from Svalbard to Russia generally favor expansion, but the island chain is there and there are some crossing winds muching things up. There's a cyclone straddling the Bering Strait which currently  should be creating a net expansion of ice. Later in the day this one moves north of the CAA and another is entering the Bering Strait... cancelling each other out?

A push. Another middling day mostly because all the mush on the Pacific side and along Siberia should continue melting, plus a little help along the CAA and Greenland.

Caveat: All that mush. A bunch of it could melt away due to the cyclones.

Daily Changes Needed to Exceed 2012 low on Aug. 10. (Related to effect of GAC and it's import vs. 2019's melt cycle.)

8/10/2012 stood at 4.94M km sq.
2019 needs an average daily drop of > 113.75k km sq. for a record low on this post-GAC date. (9 days.)

I fully expect 2019 to have a higher extent than 2012 sometime between the 5th and 7th, and much more likely the 5th or 6th than the 7th except for the "caveat" above. We could see very little actual ice loss over the next 8 days and still see a huge drop in extent if that mush melts away.

Daily Changes Needed to Exceed 2012 Record Low on Sept. 15. (Related to comparison of 2012 vs 2019's melt cycle.)

9/15/2012 stood at 3.18M km sq. on this date.
2019 needs an average daily drop of > 60.68k km sq. for a record low on this date. (45 days)

This still has a fair chance of happening, but gets less likely each day these small meltouts happen. The caveat is... the above caveat. There's an awful lot of low concentration ASI right now and if that all melts out, things will be getting interesting.

Will 2019 get it's "big week in June" and/or "big week in August?"

44
Consequences / Re: Heatwaves
« on: July 26, 2019, 12:03:49 AM »
So Stephan,

assuming it's neither a local Urban Heat Island effect, nor the local nuclear power plant letting out steam, I wish to thank you for your efforts keeping us up-to-date.

I also noted that Wikipedia for Lingen had already been updated this evening:

Quote
On 25 July 2019, Lingen set the record for the temperature record ever recorded within Germany with a daytime high temperature of 42.6 degrees Celsius (109 degrees Fahrenheit) during a heat wave affecting much of Europe.

I agree, it's time to call it a day.

45
Antarctica / Re: Melt water in Antarctica
« on: July 15, 2019, 06:47:43 PM »
#1 Nansen ice shelf

#2 Blood Falls is an outflow of an iron oxide-tainted plume of saltwater, flowing from the tongue of Taylor Glacier onto the ice-covered surface of West Lake Bonney in the Taylor Valley of the McMurdo Dry Valleys in Victoria Land, East Antarctica.
Iron-rich hypersaline water sporadically emerges from small fissures in the ice cascades. The saltwater source is a subglacial pool of unknown size overlain by about 400 metres (1,300 ft) of ice several kilometers from its tiny outlet at Blood Falls.

46
Arctic sea ice / Re: Latest PIOMAS update (July 2019)
« on: July 14, 2019, 08:39:06 AM »
Another question Wipneus, you posted a chart last year that showed the distribution of PIOMAS thickness bins and was a good predictor of area at minimum, if I am not mistaken. Could you post it again this year?

That would be the gice graphs. For an explanation of gice see https://forum.arctic-sea-ice.net/index.php/topic,119.msg152005.html#msg152005

Attached are the 30th June graphs.

47
Arctic sea ice / Re: The 2019 melting season
« on: July 14, 2019, 12:11:21 AM »
The weather forecasts look great for dramatically slowing ice melt compared to what we have seen most of the summer.

Yep. And we've melted off most of the easier to melt ice.

At end of May we had 6.7M km2 of ice (area) outside the CAB and 3.0M km2 inside the CAB.

Now we have 2.8M km2 inside and 2.8M km2 outside.

The degree of difficulty in melt is increasing as the easy stuff on the shallow perimeter has shrunk considerably.
Isn't this primarily the same equation that exists at this time of year for every melt year, good or bad? Very few years have had any significant reduction in actual CAB ice by July 12 and probably none where the atlantic front is not the leading region of melt. The melt out of the 'easy ice' around the CAB happens every year and results somewhere around July 10th in a very similar remainder of 50% CAB and 50% other seas.

The bigger questions are 'how easy' is the remaining ice and in the 2012 record year there was almost 0 ice remaining in Hudson, Barents, or Kara where 2019 still has a lot of 'easy ice' and the conditions of the remaining ice on the Asian side (ESS, Chukchi, and Laptev looks 'easier' than it did in 2012. The CAB itself with less MYI since 2012 also looks 'easier' even if the Atlantic side of the CAB is not as exposed at this time.

How good the PIOMAS data is might be questionable but the number at the end of June suggests 2019 had on that date the 'easiest' remaining ice to melt and the best 'momentum'. The first part of July hasn't changed that perspective in my view.

Weather during the next 45 days will have a huge effect. 2019 may slow like other years since 2012 but I think we still have a wide range of possible Sept conditions including a record or a more average 2010s minimum.

48
Arctic sea ice / Re: Latest PIOMAS update (July 2019)
« on: July 08, 2019, 06:15:10 AM »
Do you have the June 2019 average ice volume at hand? http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/PIOMAS.2sst.monthly.Current.v2.1.txt is still not updated. Thanks
It has been updated now:

Lowest   Year    1,000 km3

    1st.   2017    15.400
    2nd.  2019    15.905
    3rd.   2012    16.002   

49
Science / Re: 2019 Mauna Loa CO2 levels
« on: July 07, 2019, 08:58:23 PM »
It isn't that long ago that I thought a high 2 ppm increase was something noteworthy; now we're seeing 3.81 even without a strong el-nino or other natural cause that I am aware of; scary.

50
Arctic sea ice / Re: The 2019 melting season
« on: July 03, 2019, 11:10:56 PM »
For context, here's a quickly assembled map with the areas I've been discussing labelled.

Meanwhile, note that the satellite image uniquorn just posted shows a wide CAA/CAB crack extending at least as far east as Borden Island, with fairly dodgy-looking ice encroaching into the northern boundary of the PGAS (albeit mostly off-frame).

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