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AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #250 on: November 19, 2014, 08:06:46 PM »
The attached Terra image of PIIS was taken on Nov 19 2014 and shows little change to the calving face in the past week or two.
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AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #251 on: November 23, 2014, 07:02:03 PM »
The attached "Natural Light" Landsat 8 image from Nov 23 2014 indicates that both the shear and flexural cracks in the PIIS are widening and lengthening.
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AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #252 on: November 26, 2014, 09:58:26 PM »
I will be on vacation until Dec 8 2014, so I will not be posting in that period.

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ASLR
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #253 on: November 26, 2014, 10:23:51 PM »
Have a good vacation, ASLR.  :)
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #254 on: November 27, 2014, 01:21:28 PM »
same crack seen with S-1 on 26.11.2014

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #256 on: December 03, 2014, 11:36:07 AM »
Nice article on EarthSky about B31.

Given that helpful hint, B31 is plain for all to see on Worldview:

http://1.usa.gov/1yNhGRc
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #257 on: December 05, 2014, 09:30:39 AM »
Nice clear weather over the PIG area and a Landsat satellite flying over. In this medium resolution (60m/pix) the crack can be clearly seen.

(click to see the 1MB image)

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #258 on: December 05, 2014, 09:47:34 AM »
Here is a hi-res detail of the crack. I cannot say that is has widened very much (still about 90 meter), but this image shows more clearly than before that is runs more or less straight through and beyond the band with ridges.

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #259 on: December 05, 2014, 10:39:56 AM »
Thanks guys, for the great spotting!
I was surprised how fast the flow had compensated for the loss of front-stretch last year. The new crack might be an indication the process of calving is gradually getting upstream.

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #260 on: December 08, 2014, 05:17:09 PM »
While it is hard to say for certain, because of the cloud cover, I believe that the attached Aqua image taken Dec 7 2014 shows a relatively small calving event (if I am correct then this would account for the white flow in the notch rather than cloud cover) of the highly fractured ice at the northeast tip of the "notch".  Thus when the clouds clear, we will likely see that the notch is a little bit longer now than before yesterday.
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AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #261 on: December 08, 2014, 05:57:10 PM »
Here is a hi-res detail of the crack. I cannot say that is has widened very much (still about 90 meter), but this image shows more clearly than before that is runs more or less straight through and beyond the band with ridges.

I agree that the "flexural" crack is not widening, nor lengthening, quickly (relative to the speed of the ice flow in the PIIS).  Thus my current concern is that by about next November (2015) the ice shelf will have flowed downstream sufficiently that a new compressive strut would form (see attached image, and Replies #221 and #225) from the compression introduced from the inflow of the SW Tributary glacier, so that by Nov-Dec 2015 (or later) a new crack might form roughly parallel to the current crack, and that when the new crack ruptures it may kick-out (see panel b of the image) sufficiently to cause the current "flexural" crack to extend (abruptly) sufficiently to connect with both the "shear" cracks at the northeastern tip of the notch and at the southwestern corner.  If so, then a major calving event could occur with the new iceberg (B-32?) moving seaward at the southwestern corner and rotating about the submerged pinnacle (near the mouth of the notch), and if such a calving event were to be energetic enough, B-32?  could become unpinned and float away. 
If B-32? were to float away, it could provide enough room for a tidal (vertical bending) induced second calving event (B-33?) possibly before the end of the Austral Summer of 2015-2016, with B-33? splitting away along the postulated second "flexural" crack.  If this second calving event were to occur, it would partially (possibly by 50%) reduce the buttressing action of the PIIS against the SW Tributary glacier (which would then accelerate; which would eventually influence the shear strain along the northeastern shear margin of the Thwaites ice stream). 

It is conceivable, that this second type of calving could happen repeatedly in coming years(possibly producing future B-34, 35, etc icebergs every say 2-years).  If so this would keep the buttressing action on the SW Tributary glacier low for many years; which might then contribute to an acceleration of the Thwaites ice stream velocities (particularly if the Thwaites Eastern Ice Shelf continues to degrading in coming years due to the continued advection of warm CDW in this area).
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #262 on: December 09, 2014, 08:42:36 PM »
While still a little bit cloudy the attached Terra image of the PIIS for Dec 9 2014, makes it clear that indeed the notch has extended some distance to the east (likely due to a calving event on Dec 7th).
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #263 on: December 10, 2014, 07:18:37 PM »
While still a little bit cloudy the attached Terra image of the PIIS for Dec 9 2014, makes it clear that indeed the notch has extended some distance to the east (likely due to a calving event on Dec 7th).

Confirmed by a little bit cloudy Landsat:
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #264 on: December 10, 2014, 08:10:32 PM »
Jim,

Thanks for the catch on Landsat 8 for Dec 9 2014.  Based on the two attached extracts from that Landsat 8 image, I don't think that many people would be very surprised if: (a) the notch extends all the way to the end of the shear fractured ice zone (shown in the first attached image) by the end of the austral summer and thus widens and elongates the shear crack shown near the end of this shear fractured ice zone; and (b) there is more calving in the Southwest corner of the PIIS (see the second attached image); which could similarly result in the local Southwest shear cracks from extending towards what I am calling the flexural crack by the end of this austral summer.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #265 on: December 10, 2014, 09:08:03 PM »
I thought that I would post this Nov 14 2014 Landsat 8 image of the residual Thwaites Ice Tongue and Eastern Ice Shelf to illustrate that once the pinned remains of the old Thwaites Ice Tongue gets unpinned and floats away as an iceberg, then all of the upstream ice is in the form of bergy bits that will not become pinned and will just float away, which will essentially relieve any remaining buttressing action on the Thwaites ice stream that fed the old Thwaites Ice Tongue.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #266 on: December 11, 2014, 05:28:39 PM »
The attached Terra image from Dec 11 2014, appears to indicate a very small minor possible calving event near the tip of the notch.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #267 on: December 13, 2014, 01:36:09 AM »
I thought that it might be interesting to see in the attached Aqua image of Thwaites for Dec 12 2014, that there is still a fairly significant amount of sea ice around the Thwaites Ice Shelf & Residual Ice Tongue, possibly because the air temperatures in this area have been colder than normal for this time of year:
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #268 on: December 16, 2014, 12:40:37 AM »
The two attached images extracted from the Landsat 8 image for Dec 14, 2014, shows that both the notch and the Southwest corner areas of the Pine Island Ice Shelf, PIIS, are continuing to slowly degrade.
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AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #269 on: December 18, 2014, 08:27:01 PM »
The first attached Landsat8 image of the area near the tip of the Thwaites Eastern Ice Shelf taken Dec 14 2014 shows the continued impact of advection (which is less for Thwaites than for PIG) forming a small polynya between the tip of the Thwaites Eastern Ice Shelf and the grounded iceberg at the end of the residual Thwaites Ice Tongue.

The second attached Terra image of the PIIS for Dec 18 2014 indicates that a very minor amount of calving occurred of the fractured glacial ice at the tip of the notch on Dec 17 2014.
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AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #270 on: December 19, 2014, 07:08:19 PM »
The first attached Landsat 8 image of the PIIS notch tip on Dec 18 2014 shows that indeed there was a minor calving event at the tip of the notch on Dec 17 2014.  Also, this first image shows that location of the shear cracks at the notch tip in regards to the location of the "Flexural Crack", indicating the feasibility of the idea that a new "Flexural Crack" parallel to the current "Flexural Crack, possibly forming as early a Nov 2015 (with the timing linked to the ice velocity of the PIIS ice stream), by inducing a "kick" that would extend the existing cracks to form a major calving mechanism.

The second image show a Terra image of the PIIS for Dec 19 2014; which I provide as a reference, for comparison with possible future minor calving events this austral summer.
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AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #271 on: December 28, 2014, 01:22:16 AM »
Comparing the attached Aqua image of the PIIS from Dec 27 2014, with the Terra image for Dec 19 2014 in my preceding post, it is clear that a meaningful (but small) calving event in the week in between these two dates in the Southwest Corner of the PIIS (also the "flexural" crack is very clear in this Aqua image):
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #272 on: December 29, 2014, 09:39:48 PM »
Per the first two attached Aqua images of the PIIS (one natural light and the other filtered to differentiate ice and clouds, respectively) from Dec 29 2014, it looks like the Southwest corner of PIIS is being reconfigured (possibly due to compression) with some associated calving debris in the adjoining ocean.  Based on the third attached Aqua image of the PIIS taken yesterday, it appears that this reconfiguration began on Dec 28 2014 and is continuing into today.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #273 on: January 03, 2015, 01:05:16 AM »
While not 100% certain, the attached Terra image of the PIIS for Jan 2 2015 indicates that meaningfully calving event has occurred in the SW corner:
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #274 on: January 07, 2015, 09:54:31 PM »
The two attached images are from the Landsat8 picture taken on January 6 2015 and the first image shows the Southwest Corner has a free-floating iceberg that has not yet been displaced from the calving face, while the second attached image shows that the notch and the "flexural" crack are slowly degrading (possibly on pace to facilitate a major calving event in the Nov to Dec 2015 timeframe).
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #275 on: January 13, 2015, 10:16:36 PM »
The attached Terra image of PIIS taken on Jan 13 2015 shows that the iceberg that had been moving around within the small Southwest notch has finally floated away from the calving face.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #276 on: January 15, 2015, 06:49:58 AM »
Sequence of two Sentinel-1A panorama quick-look images separated by 3 months in time.

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #277 on: January 15, 2015, 05:55:51 PM »
Wipneus,

Thanks for the great Sentinel-1A sequence that not only shows how quickly the PIIS is extending its calving face seaward, but also indicates to me that the residual Thwaites Ice Tongue is also moving seaward and may only be held in-place by the surrounding land-fast sea ice.  While I do not expect the PIIS to have another major calving event until the Nov-Dec 2015 timeframe, it would be interesting if the residual Thwaites Ice Tongue were to float away once the sea ice breaks-up later this austral summer.

Also, the attached PIIS Landsat 8 image is from Jan 15 2015.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #278 on: January 16, 2015, 12:16:40 AM »
There's also a possibility of a medium size calving event at the eastern end of Thwaites calving front.
That would be an ice berg of about the size of Manhattan if it calves off in one piece.



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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #279 on: January 19, 2015, 08:20:28 PM »
There's also a possibility of a medium size calving event at the eastern end of Thwaites calving front.
That would be an ice berg of about the size of Manhattan if it calves off in one piece.

As the attached Aqua image of the Thwaites Ice Shelf for Jan 19 2015 indicates, the break-up of some of the previous fast sea ice on the eastern edge of the Thwaites Ice Shelf is allowing for the Manhattan sized iceberg for the calving event that Yuha discusses, to move away from the calving face.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #280 on: January 26, 2015, 06:24:39 PM »
While the attached Aqua image of the PIIS from Jan 26 2015 is not much different than the Jan 13th image shown in Reply #275, I thought that I would post it and note that even if the extent of the notch is not growing rapidly nevertheless:

(a) As the ice flow velocity increases the resistance of the shear margins are decreasing (see the link regarding MacGregor et al 2012)

http://www.skepticalscience.com/West-Antarctic-Ice-Shelves_U-of-Texas-at-Austin.html

(b) Due to both basal ice melting and ice flow acceleration the thickness of the PIIS is decreasing and thus its propensity to calve is increasing and its buttressing action is decreasing.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #281 on: February 05, 2015, 10:18:21 PM »
The attached Terra image of Thwaites was taken today (Feb 5 2015), and indicates that the land-fast ice in this area is starting to break-up which will likely release a number of bergy bits that have been calved from both the Eastern Thwaites Ice Shelf and the residual Thwaites Ice Tongue in the past year, or so.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #282 on: February 06, 2015, 08:31:20 PM »
The first attached image of the ASE taken Feb 6 2015 shows that the sea ice in this area is slowly starting to break-up and retreat from the embayment.  It will interesting to watch this sea ice in the coming weeks.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #283 on: February 09, 2015, 02:48:05 PM »
Here is a sequence composed of Landsat images (30m/pix) from Dec 4 and Feb 6, spanning a 64 day interval.
Measuring pixel movement, using the 15m native resolution, the ice moved about 701.5 meter. That translates to an average speed of 11 m/day, the highest figure that I measured yet.

The "crack" has widened a little, but the visible part is also much longer. Especially to the west (right in this image).

A next crack-like feature, parallel to this one, is faintly visible upstream. Whether this is an optical aberration or really a new crack is as yet an open question.

(click to see the 2.8 MB animation)


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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #284 on: February 09, 2015, 04:28:57 PM »
Thanks Wipneus. Is there any chance you could try something similar for the Roi Baudouin Ice Shelf. Here's the reason I ask:

http://GreatWhiteCon.info/2015/02/new-antarctic-sea-ice-resources/

Quote
While large icebergs calve regularly from fast-flowing ice shelves in West Antarctica, the coast of cooler, drier East Antarctica tends to be less active. That made it a mild surprise when a 70-square-kilometer chunk of ice broke off from the King Baudouin Ice Shelf in January 2015. The last time that part of King Baudouin calved such a large iceberg was in the 1960s.

I hope all the associated information is OK with you?
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #285 on: February 22, 2015, 05:27:25 PM »
The two attached Terra images of the PIIS for Feb 22 2015 (one with natural light and one with a red filter, respectively) clearly indicate a localized calving event within the "notch".  I believe that such localized calving events are dominated by the influence of the advection of warm CDW beneath both the local sea ice and beneath the PIIS itself.  Furthermore, there are forecasts of a moderately strong classical El Nino event by the boreal Fall (austral Spring) of 2015; which could intensify the flow of such warm CDW beneath the PIIS by November 2015; which in turn might promote a possible major calving event by Nov - Dec 2015.

Also, I note that such localized calving events in the "notch" reduces the boundary restraints that are currently slowing the elongation of the "flexural" crack in the PIIS (documented by Wipneus).
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #287 on: February 23, 2015, 08:08:51 PM »
I do not see anything unusual:


When comparing to the Landsat8 image from Feb 6 2015 in Reply #283, it is clear to me that the notch is longer than in the attached first Polarview image from Feb 21 2015.  Thus either Terra image from Feb 22 2015 is showing snow blown into the seawater in the notch, or there was an actual calving event of the shear fractured glacial ice at the tip of the notch on or near that data.

The second attached image is a Terra photo of PIIS on Feb 23 2015.

The third attached image is an Aqua photo of Thwaites on Feb 23 2015.

The fourth attached image of the ASE is also from Feb 23 2015 and shows that the sea ice in the embayment may slowly be breaking-up.
« Last Edit: February 23, 2015, 10:05:57 PM by AbruptSLR »
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #288 on: February 23, 2015, 08:32:54 PM »
Note that the polarview image is from 20150221. The brake up ASLR noticed was on the 22:nd.
A small animation from terra Feb 21-23.

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #289 on: February 24, 2015, 06:02:40 PM »
Looks like some wind kicked up around the corner of Thwaites.  I'm having trouble wrapping my head around the change here.  Definately some sea ice moving, but was there a calving or further breakup of landfast ice? 
Both images have a date stamp of 2/24.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #290 on: February 24, 2015, 06:11:41 PM »
Looks like some wind kicked up around the corner of Thwaites.  I'm having trouble wrapping my head around the change here.  Definately some sea ice moving, but was there a calving or further breakup of landfast ice? 
Both images have a date stamp of 2/24.

solartim,

Thanks for the nice images (attached also is a closer view of the Terra image on Thwaites from today).  As discussed earlier in this thread a meaningful chunk of glacial ice calved from the Southeastern portion of the Thwaites Eastern Ice Shelf a few months ago, but was trapped by the fast sea ice.  So now that the sea ice is slowly breaking-up this calved iceberg is now slowly floating away.

Best,
ASLR
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #291 on: February 25, 2015, 01:14:29 PM »
Polarview from today. How long before that entire section leaves the port?

icefest

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #292 on: February 25, 2015, 01:29:41 PM »
That crack is getting closer and closer.....
Open other end.

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #293 on: March 07, 2015, 01:24:51 AM »
The attached Landsat8 image of the Thwaites gateway on March 6 2015 shows that the sea ice to the North and East is moving away, but that there is still a significant amount of fast sea ice to the West of the Thwaites Eastern Ice Shelf.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #294 on: March 07, 2015, 07:29:47 AM »
The crack is more visible on Polarview from 20150305.

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #295 on: March 07, 2015, 06:11:25 PM »
I provide the four attached images of the PIG area in order to document an apparent calving event of grounded glacial ice (not floating) in the area immediately to the Southwest of the PIIS (so I have labeled the images PIG Southwest Corner to differentiate from my other PIIS images).

The first Terra image from March 6 2015 shows this area before the calving event.  The second Landsat8 image from March 6 2015 shows this area immediately after the primary calving event.  The third Aqua image from March 6 2015 shows some secondary calving following the primary calving activity.  Finally, the fourth attached image from this morning, March 7 2015 shows the about the same size debris field floating in the ocean at the calving site as the Aqua image from the evening of March 6.

While I do not know why this ice calved (it may be normal calving activity); however, it could be related to warm CDW water advecting near the calving event grounding line, and/or could be related to a compressive stress field on this PIG Southwest Corner area as the PIIS accelerates and bears harder against this grounded corner glacial ice.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #296 on: March 11, 2015, 11:51:38 AM »
Close-up of the crack seen by Landsat 8 this time. The crack is 105-120m wide over a long range and appears slowly widening. The length of the crack is increasing also, I have put some arrows at the end points where I can reliably identify the crack.
The second upstream crack is now visible without a doubt. Marked with an arrow as well.

(click to see the full resolution image)

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #297 on: March 11, 2015, 06:42:45 PM »
Thanks Wipneus. Could you add this frame to your animation from Feb 9?  I'm trying to get a sense of the rate of expansion- both width and length - of the crack.

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #298 on: March 11, 2015, 06:52:50 PM »
It's just a matter of time...tidal flexing etc. will propagate the crack through sooner or later. When was the last time PIG had a major calving event? A few years at least?

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #299 on: March 11, 2015, 07:06:57 PM »
It's just a matter of time...tidal flexing etc. will propagate the crack through sooner or later. When was the last time PIG had a major calving event? A few years at least?

If my speculation in Reply #261 is correct, then this up-coming calving event may be different than the July 2012 to November 2012 calving event (see Replies 225 and 230), in that the failure plane may extend from the "flexural" crack towards the shear cracks in the Southwest corner (see attached Landsat8 image from March 8 2015), and then rotate outwards around the submerged pinnacles to float away.  If so this different calving mechanism is important because it would result in a new calving face that is further upstream than the 2012 calving event (see Reply 230); which would relieve some of the buttressing on the Southwest Tributary Glacier, which would help to destabilize the Thwaites Gateway.

Edit: As a reminder I have stuck my neck-out and projected that a new major calving event could occur in the Nov-Dec 2015 timeframe (based on geometry and the rate of ice flow velocity for the PIIS).  This would be followed by successive major calving events every two to three years with each new calving face moving further upstream (thus successively relieving buttressing from the Southwest Tributary Glacier).
« Last Edit: March 11, 2015, 07:20:49 PM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson