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AbruptSLR

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Re: PIG has calved
« Reply #100 on: February 12, 2014, 02:23:23 AM »
Based on the attached images from Terra on the afternoon of Feb 11 2014, I conclude that what the morning images showed was a minor calving event of fractured ice from the west by northwest tip of Block 1.  It appear clear in these afternoon images that Block 1 is still attached to the PIIS Ice Stream (and is probably still pinned by the pinnacle), and that the PIIS Ice Stream did not lurch forward (even locally in the notch area).  Again, these images only indicate continuing local calving of fractured ice in and around the notch.
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Wipneus

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Re: PIG has calved
« Reply #101 on: February 12, 2014, 01:07:26 PM »
Added Feb 10 to the sequence, a bit cloudy but the ice is quite visible. Estimated movement since Jan 27: 7 pixels down 6 left, about 138m. So no dramatic change in speed.

Click on the image for the animation.

AbruptSLR

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Re: PIG has calved
« Reply #102 on: February 12, 2014, 05:34:23 PM »
Wipneus,

Thanks for the great updated sequence.  I concur that most, or all, of the calving events that we are seeing from the notch appears to be fractured glacial ice debris that was sheared upstream as the PIIS ice stream flows west by northwestward.  Thus not indicating a general acceleration of the PIIS ice stream, and as similar notch have been seen in the past, the presence of the notch by itself does not bring into question the structural integrity of the PIIS ice stream.  Again, what I am mostly concerned about is that all previous notches were many kilometers towards the west by northwest, while this current notch is right near the pinnacle.  Thus as long as PIIS stream remained pinned by the pinnacle we can assume behavior similar to the past.

I believe that the attached Aqua image from February 12 2014 likely shows additional calving of previously fractured glacial ice debris from the northwest corner of the notch (i.e. from the non-ice-stream portion of the notch).  It seems likely to me that we are seeing so much calving activity (of fractured ice) because the ocean water is warmer than normal, thus forming the notch so far eastward, and we can reasonably assume that such warm ocean water is accelerating basal melting from PIIS causing it to thin faster than in the past.
« Last Edit: February 12, 2014, 08:39:32 PM by AbruptSLR »
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AbruptSLR

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Re: PIG has calved
« Reply #103 on: February 13, 2014, 07:10:03 PM »
In the way of a status report, I thought that I would post these images from Terra for Feb 13, 2014, of the PIIS and the Thwaites Ice Shelf, respectively; although the images do not show much recent change:
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AbruptSLR

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Re: PIG has calved
« Reply #104 on: February 15, 2014, 01:19:16 AM »
While there are some clouds in this image, it appears to me that the arm of the notch pointing eastward looks a little longer in this Feb 14, 2014 - Terra afternoon image.
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Re: PIG has calved
« Reply #105 on: February 15, 2014, 04:26:02 AM »
Landsat had this image available from Feb 10 2014, but I see very little differences in the ice from the Feb 8 2014 Landsat image that I posted earlier this week.  It will be interesting to see a Landsat image from after the Feb 11 & 12 calving events, when it (they) become(s) available.
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AbruptSLR

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Re: PIG has calved
« Reply #106 on: February 15, 2014, 07:40:41 PM »
Comparing the accompanying Landsat image of the PIIS notch area from Feb 15 2014, with the Feb 10 2014 image in my last post, the areas of fractured glacial ice that have calved always on Feb 11 & 12 are clear (leaving the "arm" pointing eastward much longer.  But I am even more concerned that when comparing the Feb 10 and the Feb 15 images that the fissures around Block 2 look to have a growing amount of open water, which might portend a future calving of Block 2 this austral summer.
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AbruptSLR

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Re: PIG has calved
« Reply #107 on: February 15, 2014, 07:50:03 PM »
Both of the Landsat images show the area around the iceberg that calved from the Thwaites Ice Tongue in October of 2012, which is now stuck in landfast sea ice.  The first image is from Feb 13 2014 and shows a major crack in the landfast sea ice to the west of the iceberg; which the second image from Feb 15 shows a large area of this landfast sea ice previously to the west of the iceberg has disappeared.  This does not necessarily mean that the iceberg will break free of the landfast ice this austral summer, but it clearly means that the relatively warm ocean water in this area is continuing to melt the local landfast sea ice.  It is my believe that if, and when, this iceberg finally does break free (possibly next austral summer if a big El Nino event happens at the end of 2014), this will expose the western side of the Thwaites Eastern Ice Shelf to accelerated calving.
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steve s

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Re: PIG has calved
« Reply #108 on: February 15, 2014, 09:09:48 PM »
Thank you ASLR for posting these detailed images.

I've been watching that notch form and increase in size over the last few days, but using the less detailed MODIS images. How the notch could open to the extent it did without spilling visible ice into the ocean was difficult to understand. Apparently there are a pair of actions involved. The ice (which apparently was thin) crumbled, but remained along the other ice, apparently pinned by a current. The other action is a surface current flowing west under the ice which has shifted ice west opening that notch while closing the obvious crack in the first photo.

If one examines the movements of separating ice blocks along the coast between the Thwaites tongue and the PIG over series of images, the same current seems to be active.

Has to be a lot of water moving, possibly augmented by high flows through the Thwaites gateway. This area may prove interesting in the next week or so.


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Re: PIG has calved
« Reply #109 on: February 16, 2014, 03:33:28 AM »
ASLR, I believe the iceberg in post #107 is not (just) stuck in landfast ice but is pinned on an underwater peak. In the figure below (from "Progressive unpinning of Thwaites Glacier from newly identified offshore ridge: Constraints from aerogravity" by Tinto & Bell, Geophysical Research Letters, Vol. 38, L20503, doi:10.1029/2011GL049026, 2011) the peak is labelled 2 in Figure C and is about 400-500 meters below surface according to Figure B.

The iceberg is actually moving slowly northwards, probably pushed by the remnants of the ice tongue. If so, the iceberg may be slowing down the flow of Thwaites at least a bit. Sometime fairly soon, within a few years, either the iceberg advances past the peak and sails away, or the ice tongue breaks down and stops pushing the iceberg. Either event could speed up the flow of Thwaites, which is a scary thought as that part of Thwaites is already the fastest moving part and also where the Byrd Subglacial Basin comes closest to the Thwaites grounding line.

AbruptSLR

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Re: PIG has calved
« Reply #110 on: February 16, 2014, 04:16:45 AM »
Yuha,

I believe that you are correct; however, I think that the coordinates Tinto & Bell show on their drawings are not very precise.  In any event with the top of the pinnacle labeled 2  is shown as being between -400 and -500m, and as the old ice tongue was thinning with time, it may be that this new iceberg is easier to dislodge as compared to prior icebergs that where temporarily pinned on this pinnacle 2.  Also, I note that MacGregor et al 2012 states that that the buttressing action from the stunted Thwaites Ice Tongue was not as significant as some earlier researchers had suspected.

We will all need to wait to see what happens in this area with time in the warming ocean of the ASE. 

Thanks,
ASLR
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AbruptSLR

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Re: PIG has calved
« Reply #111 on: February 16, 2014, 06:16:40 AM »
For those who are interested, I am posting the attached image of the Thwaites Ice Tongue Iceberg (and of the Thwaites Eastern Ice Shelf) in this Modis image from Feb 8 2013; however, the image is rotated 90 degrees from the other images of this area in this thread.  It can be seen in this image that all the currently extant ice to the west of the Thwaites Ice Tongue Iceberg is sea ice, as in Feb 2013 all of this area was open water.  This supports Yuha's statement that the iceberg is pinned by the pinnacle labeled 2 by Tinto & Bell, and not by the sea ice. 

Nevertheless, it is also clear from the Feb 8 2013 image that the ice south of the iceberg was gradually calving blocks of bergy bits, and this local calving of blocks of bergy bits could accelerate if this sea ice to the west of the old Thwaites Ice Tongue disappears in the future (maybe next austral summer).
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AbruptSLR

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Re: PIG has calved
« Reply #112 on: February 16, 2014, 12:18:18 PM »
Further to my last post about the Thwaites Ice Tongue Iceberg, I provide the first image from Modis March21 2013 (where north is at the top of the image), and also the second Terra image from Dec 11 2013 (where north is at the left of the image).  This gives more information about the changes (timing & location) in the local sea ice, and the gradual calving of small blocks of glacial bergy bits.
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Re: PIG has calved
« Reply #113 on: February 16, 2014, 11:45:32 PM »
I provide a series of weblinks and the two attached images to give those who are interested a better back story about the major 2012 calving event for the Thwaties Ice Tongue that has left it roughly in the configuration that it is in today.


The first link is to a weblink dated Oct 8 2012, but which has been updated periodically since that date.  It presents the most comprehensive back story to the 2012 Thwaites Ice Tongue calving event, and was the inspiration for my "Surge" thread (which concludes that the 2012 surge of the Thwaites Ice Tongue appears to in-filled the subglacial cavity discussed by Tinto & Bell, 2011).  This website is also the source of the first attached image from Feb 2012 showing the Thwaites Ice Tongue and Ice Shelf prior to the calving event, while the second attached image from Sept 2012 shows this area after the calving event.  This website also has embedded the related video by Mauri Pelto also referenced in the second link below:

http://glacierchange.wordpress.com/2012/10/08/thwaites-glacier-tongue-major-calving-event-antarctica/

The following links directly to a YouTube video by Mauri Pelto about the 2012 calving event from the Thwaites Ice Tongue

https://www.youtube.com/watch?v=DWYIM29xNzk&feature=player_embedded

The following links to a NOAA article about the 2002 calving of iceberg B-22 from the Thwaites Ice Tongue
http://www.noaanews.noaa.gov/stories/s879.htm
P.S.: I also am modifying this post to attach a third NOAA image from March 2002 of the B-22 iceberg.

The following links to the WAIS 2013 Workshop thread, where: (a) reply #11 talks about the change in surface elevation of the Thwaites Glacier near the grounding line of the Thwaites Ice Tongue to the the 2012 major calving event; and the crevasse cracking pattern in that same area with a depressed surface elevation; and (b) reply #17 talks about a March 2011 calving event which I speculated might have weakened the Thwaites Ice Tongue sufficiently to trigger the major 2012 calving event:

http://forum.arctic-sea-ice.net/index.php?topic=694.0


I hope that this back story makes it clear that there have been a series of icebergs calved from the Thwaities Ice Tongue in the past, which have floated away; while the iceberg that I have most recently been referred to as being pinned by the pinnacle 2 (per Tinto & Bell, 2011), has never floated freely, but which has clearly broken off from the ice tongue as the crevasse pattern in its surface is rotated away from the crevasse pattern visible in the residual ice tongue (now broken into a bunch of approximately 1km by 1km blocks) and in the recently thinned portion of the Thwaites Ice Stream feeding into the residual ice tongue.
« Last Edit: February 17, 2014, 12:11:58 AM by AbruptSLR »
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AbruptSLR

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Re: PIG has calved
« Reply #114 on: February 17, 2014, 12:07:45 AM »
In the way of a status report, I post the accompanying four images all from Feb 16 2014 from Terra, with the first two images being of Thwaites and the second two images being of PIIS:
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AbruptSLR

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Re: PIG has calved
« Reply #115 on: February 17, 2014, 10:57:09 AM »
I am posting this magnified image of the residual Thwaites Ice Tongue (the area east of the polyna), to emphasize the following points:
(1) While Yuha is correct that this highly fractured ice zone is in compression (between the northward flow of the local Thwaites ice stream and the iceberg pinned on pinnacle 2) still: (a) when comparing this image from Feb 13 to the Feb 16 image in my prior post, it can be seen that one small bergy bit has dislodged from the southeast corner of the polyna, indicating that this small corner of the residual ice tongue was not in compression, otherwise the bergy bit could not have floated away; (b) the residual ice tongue is pushing the pinned iceberg at an angle, causing the pinned iceberg to slowly rotate, which should cause the pinned iceberg to dislodge from the pinnacle more easily, given enough time (possibly by the next austral summer); and (c) one the pinned iceberg dislodges, there will be no new iceberg from the residual ice tongue to take its turn being pinned on pinnacle 2, as the residual ice tongue is so fractured, that when the compressive stress in it is relieved by the iceberg floating away (in the future) then the ice tongue will likely fragment rapidly into individual bergy bits.
(2) The local conditions around the Thwaites residual Ice Tongue and Eastern Ice Shelf are becoming more conducive to the fragmentation of these ice features due to: (a) the increasing ocean water temperatures, which causes continuing basal ice melting of these features; (b) the eastern face of the Thwaites Eastern Ice Shelf has recently calved a few relatively large ice blocks from its eastern face, indicating it is also degrading together with the ice tongue; and (c) when looking a the findings of MacGregor et al 2012, it is clear that the rate of major calving events for the Thwaites Ice Tongue has been accelerating in recent years.
(3) The melt conditions in the ASE look likely to be worst next austal summer than in recent years due to: (a) the healing ozone hole should move the ABSL from its current location closer to the Ross Sea back eastward toward the ASE; (b) an El Nino event is likely by the next austral summer; and (c) it seems likely to me that what I called "horizontal advection" between PIG and Thwaites appears to be strengthening as the basal melting in PIG/PIIS is accelerating thus directing more warm CDW towards Thwaites.
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AbruptSLR

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Re: PIG has calved
« Reply #116 on: February 17, 2014, 06:12:35 PM »
I am concerned some readers will think that the influence of any El Nino event (possibly in the 2014-2015 austral summer) on the ASE marine glaciers and pinned ice shelves (i.e. PIIS, and Thwaites) is primarily due to the temporary increase in the volume of warm CDW conveyed into the ASE, and that due to the relatively slow rate of sub-ice-shelf melting from an incremental increase in CDW volume, that this effect would be relatively small and short-lived.  However, due to the interaction between an El Nino event and the ABSL (see following discussion of the ABSL), an El Nino event can also temporarily (multiple months, particularly from October to February) increase sea level in the ASE; which can: (a) reduce the pinning action of pinnacles; and (b) release pressurized subglacial hydrological basal water that previously had been sealed by the weight of the ice overburden at the marine glacial gateways (e.g. PIG and Thwaites); which can in-turn accelerate ice flow velocities from the marine glaciers (which could cause the residual Thwaites Ice Tongue to surge, which might shift, or displace, the pinned Thwaites Ice Tongue iceberg, discussed in my prior posts in this thread).

The following quote  is from the link after the quote, gives an idea about the importance of the ABSL and the ENSO/SAM cycles to the stability of the marine glaciers and pinned ice shelves in the ASE (I recommend going to the linked website about the ABSL and looking at the whole write-up and the various PowerPoint presentations there):

"Given these relationships, a main suspected factor from an atmospheric standpoint causing the temperature and sea ice changes described above are variations in the strength and position of the ABSL. Fundamentally, the ABSL exists because the Antarctic Peninsula and the off-axis nature of the Antarctic topography dynamically influence the atmospheric flow of the region (Baines and Fraedrich 1989; Lachlan-Cope et al. 2001). Its strength is influenced by large-scale patterns of climate variability that impact Antarctica, namely the Southern Annular Mode (SAM) and the El Niño - Southern Oscillation (ENSO). The SAM describes the strength of the mid-to-high latitude meridional pressure gradient and circumpolar zonal winds (Thompson and Wallace 2000; Marshall 2003). Although ENSO is a tropical climate oscillation, it impacts the whole globe through teleconnections. Its impact near Antarctica is in the region of the ABSL, part of an alternating wave-train of pressure/height anomalies stemming from the Tropics during ENSO events, known as the Pacific South American pattern (Karoly 1989; Mo and Ghil 1987; Renwick and Revell 1999; Mo and Paegle, 2001; Turner 2004; Yuan 2004; Lachlan-Cope and Connolley 2006)."

http://www.scalialab.com/absl/site/about.shtml


The attached image (from the following link) showing how the ABSL drives wind and associate ocean surface currents towards the ASE, which not only drives warm CDW into the ASE, but also increase sea level within the ASE which serves to destabilize the marine glaciers and the pinned ice shelves in the ASE

http://www.scalialab.com/absl/site/presentationsFiles/zbacnik_AMS_ozone.pdf

The following website discusses how telecommunication from the Pacific South American, PSA, pattern conveys energy to the Amundsen and Bellingshausen Sea areas (including the ASE):

http://www.sheffield.ac.uk/geography/phd/projects/teleconnection



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AbruptSLR

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Re: PIG has calved
« Reply #117 on: February 17, 2014, 06:39:04 PM »
I am making this post to acknowledge that the Antarctic sea ice melt season approaching its annual minimum (see the first attached image of the SH The Cryosphere Today SIA for Feb 16 2014, and the second image of the University of Bremen sea ice extent concentrations in the ASE for Feb 16 2014).  Therefore, I have enlarged the photo areas for the third and fourth attached images from Feb 17 2014 - Aqua, of the PIIS and Thwaites, areas respectively, in order to show that while some landfast sea ice is continuing to break-off (break-up), there are also signs of some areas of re-freezing of sea ice.
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AbruptSLR

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Re: PIG has calved
« Reply #118 on: February 18, 2014, 03:58:16 AM »
While I am sure that Wipneus can do a much better job, I present the attached four Landsat images of cracks in the Southwest corner of the PIIS (near the junction with the SW Tributary).  From first to fourth, the images are from: Dec 6 2013, Dec 29 2013, Feb 8 2014 and Feb 17 2014; and I believe that these images show that the crack pattern is slowly growing and in particular, the crack appear to becoming slowly wider.  I imagine that at some point some significant areas of ice will calve from this area:
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AbruptSLR

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Re: PIG has calved
« Reply #119 on: February 18, 2014, 04:50:08 PM »
The attached Landsat image is from Dec 6 2013 and indicates some recent (shortly before Dec 6th) calving in the notch area (as can be seen by looking a the images in reply 27 on Nov 26 2013 and in reply 30 on Dec 9 2013).  Also, note that in this image Block 2 is longer than more recent images show, indicating that Blocks 1 & 3 could be subjected to future calving depending on crevasse formation.
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Wipneus

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Re: PIG has calved
« Reply #120 on: February 23, 2014, 10:44:57 AM »
Extending the animation with one scene:  Feb 19. The glacier ice moved in 9 days 3 pixels left, 4 down = 75m.

Sun elevation in the last scene is 18.1 degrees, down 3.0 degrees since Feb 10.

(don't forget to click the attached image)

AbruptSLR

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Re: PIG has calved
« Reply #121 on: February 23, 2014, 05:07:59 PM »
Wipneus,

It is great to see Feb 19 added to the sequence, and with the sun declining so quickly, it is unclear to me as to how much more, if any, fractured glacial ice will calve out of the notch area this austral summer.

However, I think that we should all remember that Favier et al. (2014), see reference at in of this post); have scientifically conservatively (omitting the influence of ocean-ice interaction and the influence of basal meltwater for both the glacier and the ice shelf, and the influence of the coming positive PDO cycle) projected that the speed of the PIG/PIIS ice stream will increase by a factor of five over the next twenty year, based on gravitation effects from the ice stream being unpinned from a ridge further upstream (further upstream than the pinnacle in the notch area).  Thus we can expect the PIIS ice stream to continue thinning, distorting and shearing at increasing rates in the future (winter & summer) regardless of what happens in the notch area.

Finally, I post a Feb 19 2014 Landsat 8 image of the cracking pattern in the PIIS near the SW tributary corner area, indicating to me that some of these cracks are shearing across the fracture plane, due to complex stresses in the ice in this local area.



http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2094.html

L. Favier, G. Durand, S. L. Cornford, G. H. Gudmundsson, O. Gagliardini, F. Gillet-Chaulet, T. Zwinger, A. J. Payne & A. M. Le Brocq, (2014) "Retreat of Pine Island Glacier controlled by marine ice-sheet instability", Nature Climate Change,  (2014); doi:10.1038/nclimate2094; 12 January 2014
« Last Edit: February 23, 2014, 05:36:43 PM by AbruptSLR »
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AbruptSLR

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Re: PIG has calved
« Reply #122 on: February 26, 2014, 04:54:23 PM »
The attached three images from Landsat for Feb 24 2014, provide an update on the status of the notch area of PIIS, the SW Tributary corner of PIIS, and a portion of the Thwaites area, respectively.  These images some limited amount of recent calving and a few new cracks:
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Re: PIG has calved
« Reply #123 on: March 01, 2014, 07:05:13 PM »
The attached images of the Thwaites Ice Shelf/Residual Ice Tongue area are from Modis/Terra from the morning of March 1, 2014.  By comparing these two March 1 images with the Feb 24th Landsat image in my prior post, it is clear to see that while sea ice is starting grow in other parts of Antarctica, in the ASE the sea ice is still retreating; which is clearly freeing-up some of the berg-bit previously held by land-fast sea ice between the west side of the Thwaites Eastern Ice Shelf, and the grounded iceberg at the north end of the residual Thwaites Ice Tongue.  Also, the Southeastern base of the Thwaites Eastern Ice Shelf is showing more crevasse cracking now than on Feb 17 (see prior posts in this thread):
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AbruptSLR

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Re: PIG has calved
« Reply #124 on: March 02, 2014, 05:36:15 AM »
As there still seems to be interest in this images, I am posting the attached Aqua images from the afternoon of March 1 2014, of the PIIS notch area (with some cloud cover), and of the Thwaites area, respectively.
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AbruptSLR

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Re: PIG has calved
« Reply #125 on: March 03, 2014, 01:16:27 AM »
While there is cloud cover in these March 2 2014 Lance/Modis images of the PIIS and Thwaites, nevertheless, it is clear that in comparison with the March 1 2014 images: (a) in the first Aqua image some more fractures glacial ice has calved way from the eastern side of block 1 in the PIIS notch area; and (b) in the second and third attached Terra images show that there has been a significant amount of outward displacement of the bergy-bits previously trapped between the western side of the Thwaites Eastern Ice Shelf and the eastern side of the grounded iceberg at the end of the residual Thwaites Ice Tongue.  This indicates to me that there ocean water in the ASE is still relatively warm, and also probably that the wind is blowing northward.
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AbruptSLR

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Re: PIG has calved
« Reply #126 on: March 04, 2014, 01:42:19 AM »
The attached March 3 2014 Terra image of the Thwaites area is much clearer than the March 2nd image:
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Re: PIG has calved
« Reply #127 on: March 04, 2014, 07:16:25 PM »
The attached Terra images from March 4, 2014 are the first clear images of both the PIIS and the Thwaites area, respectively.  The ice displacements are as I previously discussed.
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AbruptSLR

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Re: PIG has calved
« Reply #128 on: March 06, 2014, 12:31:03 AM »
The first attached image of the PIIS notch area is from Aqua this morning (March 5, 2014), and shows no change from yesterday.

The second attached image is of the same area but from Terra several hours later on March 5 2014, but shows a large white field in the notch area.

The third attached image is of the same area but from Terra light contracted which indicates that the large white field in the notch area is not a cloud; therefore it must be: (a) an ice debris field (from a calving event), (b) snow blowing into the notch from the top of PIIS; or (c) newly frozen sea ice.

Subsequent images should clarify what this white field is.
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crandles

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Re: PIG has calved
« Reply #129 on: March 06, 2014, 02:42:18 AM »
The first attached image of the PIIS notch area is from Aqua this morning (March 5, 2014), and shows no change from yesterday.

no change?

Is it me or does it look as if there is a lot less water in the notch? Has the glacier moved forward or is it something else?

Later terra image makes it look like the large block is nearer to hitting ice on the side.

Is that ice on the side going to be really weak or could impact? cause some blocks to dislodge from glacier?

Wipneus

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Re: PIG has calved
« Reply #130 on: March 06, 2014, 09:55:32 AM »
Also Landsat 8 was there, so I could add another frame to the sequence, March 5.

The glacier has moved about 5 pixels left, 7 down, about 130 meter since Feb 19.

(click that picture or no animation)

AbruptSLR

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Re: PIG has calved
« Reply #131 on: March 06, 2014, 01:24:23 PM »
Wipneus,

Thanks for adding the March 5 frame so quickly, as this image makes it very clear that the fractures glacier ice to the east of Block 1 calved, and knowing that the ice stream has moved 130m in two weeks gives us a good idea when Block 1 is going to run into the fractured glacial ice on the northern land-fast side of the PIIS.

crandles,

I have found that the Aqua image seems to suffer from some optical distortion, as the Landsat images makes it clear that the area of water in the notch is much larger than the March 5 Aqua image might otherwise indicate.

To respond to your question of the consequences of Block 1 eventually (in 2 of 3 months time) running into the northern land-fast side of the ice shelf: (a) the ice that Block 1 will impact is clearly fractured glacial ice and therefore is not a strong as an un-fractured ice shelf face, so I guess that it is weak but if this fractured ice gets pinned against the sound ice shelf face so that it can become compressed instead of sheared than it will put up much more resistance; (b) by the time Block 1 runs into the northern land-fast ice it will have moved off of the pinnacle so even if it becomes dislodged when it contacts the land-fast ice, that does not mean that the ice stream will necessarily accelerate; and (c) in 3 months time it will be relative dark in Antarctica so by then we may need to wait until m-d Sept. or early Oct. (depending on cloud cover at that time) to see what happened.
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AbruptSLR

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Re: PIG has calved
« Reply #132 on: March 06, 2014, 11:53:14 PM »
The attached images for the PIIS and Thwaites are from Terra (afternoon) on March 6 2014.  You can see the recently calved area from the PIIS notch, but I do not see much change in the Thwaites area.
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AbruptSLR

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Re: PIG has calved
« Reply #133 on: March 08, 2014, 11:47:29 AM »
The first image of the PIIS notch area is from Landsat on March 7 2014, and this image is what I would expect to see based on the Terra view from March 6 2014.

The second image of the PIIS is from Aqua for the morning of March 8 2014, and this image is not what I would expect to see and I am not sure what to say (optical distortion?, cloud? ice movement?)
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Andreas T

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Re: PIG has calved
« Reply #134 on: March 08, 2014, 02:11:36 PM »
It is starting to get cold down there http://efdl_5.cims.nyu.edu/aws_pig/pig_env.html
with the low sun the shadows to the right in the picture identify high clouds, but lower fog and drifting snow would be hard to distinguish from snow covered ice. How soon before the (relatively) narrow notch gets an new ice cover?

AbruptSLR

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Re: PIG has calved
« Reply #135 on: March 08, 2014, 06:05:41 PM »
Andreas T,

I agree that at this time of year the atmosphere is getting colder, and there is a lot less solar radiance, and that one very likely explanation for the March 8 2014 Aqua image of the PIIS notch area is that sea ice is forming in portions of the notch; which might, or might not, has snow on top of such sea ice.  However, if the sea water advecting out from beneath the PIIS is warm enough, then it is also possible that the apparently new what material with the notch (on March 8 ) might also be newly calved fractured glacial ice from the shear zone extending East by Southeast from the notch.

The Terra image from the morning of March 8 are too cloudy to clarify this matter.

Best,
ASLR
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AbruptSLR

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Re: PIG has calved
« Reply #136 on: March 09, 2014, 05:00:41 AM »
While the attached Aqua image of the PIIS from the afternoon of March 8 2014 has cloud cover that partially obstructs the view; to me it looks like the notch area is slightly larger than on March 7 2014, possibly indicating that the Aqua image from this morning was showing an ice debris field in the notch from a possible calving event of previously fractured glacial ice from the shear zone between the ice stream and the land-fast ice shelf (it is also possible that Block 2 has shifted but the view is so poor that I cannot tell, but I think that it is a cloud that I see rather than shifted ice).
« Last Edit: March 09, 2014, 05:05:50 AM by AbruptSLR »
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AbruptSLR

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Re: PIG has calved
« Reply #137 on: March 09, 2014, 06:56:05 PM »
The first attached image from Terra of the PIIS area for the morning of March 9 2014, shows that on March 8 2014 a major ice calving event happened on the land-fast section for fractured glacial ice (rather than for the fractured glacial ice to the East by Southeast side of the notch, nor has any shifting of Block 2 occurred) to the north side of the notch.  As this calved-ice-mass floats away, the notch will become larger.  Also, this image shows no signs of sea ice re-freezing.

The second attached image also from Terra of the Thwaites area for the morning of March 9 2014, shows little change within the past several days; however, this image also confirms that there is little, or no, re-freezing of sea ice in this area of the ASE.
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AbruptSLR

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Re: PIG has calved
« Reply #138 on: March 10, 2014, 04:05:49 AM »
The first two images are from the Aqua afternoon imagining (some hours later than the Terra morning images in my immediately prior post) on March 9 2014, for the PIIS and Thwaites, respectively.  For comparison, I also provide a view of the PIIS from Landsat on March 5 2014.

With regards to the PIIS, in the Aqua image one can see that: (a) the calved fractured glacial ice masses (icebergs) are slowly moving away from the notch; and (b) I failed to previously note that the portion of the PIIS that I previously called the cracked area near the SW Tributary corner, also cracked-off on March 8 2014, forming a new iceberg.  Therefore, I speculate that the entire PIIS shock due to the cracking-off of the SW Tributary corner iceberg, which may have then induced the fractured land-fast glacial ice in the notch area to also calve-off (or the sequence of calving could be in the reverse order).

I provide the image of the Thwaites area for completeness, as I do not see much change from the Terra image this morning.
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sidd

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Re: PIG has calved
« Reply #139 on: March 10, 2014, 04:40:09 AM »
Thanx for the pictures of the calving front. I am sorta interested in upstream views by the grounding line and even further up. I suspect something can be deduced from careful time lapse analysis of i ce surface elevation there. But that sounds like work, to which I am allergic. When i get to it in my copious spare time (ha!) i might try. This is related to VAF analysis, and my misgivings that seawater has got further upstream than we imagine. I shall try to find the time.

sidd

AbruptSLR

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Re: PIG has calved
« Reply #140 on: March 10, 2014, 02:16:45 PM »
sidd,

As we are both well aware Durand et al 2014 have projected that the contribution to SLR from PIG will increase by a factor of at least five within the next 20 years (due largely to traditional gravitational response); therefore, and VAF analysis (including rate of grounding line retreat) for PIG that you have time would be particularly interesting during this time of ice loss acceleration. 

If you do find time, then please open a new folder on this topic, as with the likely Super El Nino likely coming in 2014-15 (see the El Nino thread in the Consequence folder); it is probable that the acceleration in ice mass loss of five times in 20 years will be too low, due to both increase warming and particularly increase volume flow of CDW beneath the PIIS; which should activate more sub-ice-shelf basal melting; which should accelerate the "vertical" advection action beneath the PIIS; which I believe will lead to more "horizontal" advection of warm CDW from the PIG to the Thwaites Glacier; which should increase ice mass loss there.
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AbruptSLR

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Re: PIG has calved
« Reply #141 on: March 10, 2014, 10:19:22 PM »
As today's Terra view has cloud cover, I decided to post this morning's images from Aqua for March 10, 2014, for the PIIS and Thwaites, respectively; even though the attached images look a little blurry and optically distorted to me.  Even though the PIIS image is distorted, one can see that both of the new fractured glacial ice icebergs have moved slightly from their locations from the March 9 2014 Aqua images.
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AbruptSLR

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Re: PIG has calved
« Reply #142 on: March 11, 2014, 05:51:38 PM »
The first image is from Aqua on the afternoon of March 10 2014 and can be compared to the prior post from the morning of March 10.
The second image is from Terra on the morning of March 11 2014 and shows still more movement of the recently calves fractured icebergs.
The third image is from Terra on the morning of March 11 2014 and shows that simultaneous sea ice cracking/calving and sea ice formation are going on.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: PIG has calved
« Reply #143 on: March 12, 2014, 01:03:25 AM »
I am just posting this March 11 2014 Aqua Afternoon image of PIIS because a portion of fragmented ice berg is floating away from the notch (as compared to this morning's image).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: PIG has calved
« Reply #144 on: March 13, 2014, 01:39:24 AM »
The attached images from Terra on March 12 2014 for the PIIS, and Thwaites, respectively, are clear and self-explanatory:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Wipneus

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Re: PIG has calved
« Reply #145 on: March 13, 2014, 08:38:14 AM »
Indeed, fabulous clear weather on March 12. And to our luck, Landsat 8 was there as well.
Here a somewhat larger cut, at 30m resolution/8bits color to keep the file size small, for a wider view than I show in the animations.

Do click the picture for the full resolution image!

(animation will be updated later)

Wipneus

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Re: PIG has calved
« Reply #146 on: March 13, 2014, 09:01:06 AM »
Here is the animation (starts after a click).
I forgot to mention the sun elevation is 10.5 degress in that last frame.

johnm33

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Re: PIG has calved
« Reply #147 on: March 13, 2014, 10:28:51 AM »
Great images thanks Wipneus

Laurent

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Re: PIG has calved
« Reply #148 on: March 13, 2014, 11:16:28 AM »
What is the width of what we are seeing ? 15 m/pixel but what is the pixel size?
Thanks a lot for your work all.

Wipneus

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Re: PIG has calved
« Reply #149 on: March 13, 2014, 11:37:49 AM »
What is the width of what we are seeing ? 15 m/pixel but what is the pixel size?
Thanks a lot for your work all.

It (the forum software)  shows below the picture its size:1068x855

Multiplying by 15 m, gives widthxheight: 16.020x12.825 (km x km)

(but perhaps I misunderstood your question)