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Author Topic: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland  (Read 336147 times)

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #400 on: April 10, 2015, 10:18:55 PM »
Still on the move: (We can expect a very big one soon)
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Iceismylife

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #401 on: April 16, 2015, 03:09:58 AM »
Zachariae calving from in 15m res. Lots of melt ponds now, discolorings and all kinds of interesting creases, wrinkles and cracks are appearing

I will make a comparison with a previous date later to check the movement.

You must click the picture if you are ready for a 4M downlod.

When I look at this image, (beautiful by the way) I can't help but get the sick feeling that  glaciologists are seriously underestimating the potential sea level rise due to glaciers. Not only this one but every single sea terminating glacier that is grounded below sea level. Just as they were surprised by having the Northeast Coast of Greenland getting unlocked, they will be registering surprise by how quickly these glaciers speed up, melt, calve and retreat.
When I first saw the movement at Ilulissat (2010) I said it would go fast.  We are on an exponential growth curve in ice flow.  We are not headed to a new stable higher flow rate.  Imho it will keep doubling every 5~10 years until it is gone.  A high side estimate rather than a low side one is 50% loss in 100 years.  Or more.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #402 on: April 16, 2015, 05:57:27 PM »
Zachariae Isstrøm is showing its muscle, lots of huge potential calvings ahead for this season:
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #403 on: April 19, 2015, 09:44:30 AM »
A small interesting detail from the calving front:
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Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #404 on: April 21, 2015, 04:13:36 PM »
Small caving at Kap Zach. New break line opens further upstream.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #405 on: April 26, 2015, 09:31:19 PM »
Zachariae Isstrøm is preparing for a massive calving:
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Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #406 on: April 27, 2015, 09:08:26 AM »
Yes. At the same time the (2014) calving's further away have stopped moving with the continuous glacier movement, which indicates to me more back pressure from there.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #407 on: May 01, 2015, 10:49:42 PM »
Be prepared for a "big one":
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Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #408 on: May 01, 2015, 11:18:02 PM »
The "big one" could be as much as +/- 15 km2, compared to Petermann (small) but Jakobshavn (big).
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Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #409 on: May 04, 2015, 08:19:52 AM »
The calving is progressing faster now.


Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #410 on: May 09, 2015, 08:37:46 AM »
So slow that it is difficult to judge when the calving is complete.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #411 on: May 13, 2015, 08:55:03 AM »
Latest Landsat image reveals that the new calving is separating from the glacier front. So a new calving front is establishing.

(click to enjoy)

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #412 on: May 16, 2015, 09:19:36 AM »
Latest Sentinel medium res image also shows the new calving front is brightening up.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #413 on: May 16, 2015, 08:26:52 PM »
Still working on it, labours I guess?:
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Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #414 on: May 16, 2015, 10:17:07 PM »
The changes at Zachariae Isstrøm since May 2013, a shame the sensors were so bad before 2013 since the year 2012 was dramatic: (the last image in the animation is May 16 2015 not 2014!!)
« Last Edit: May 17, 2015, 10:33:13 AM by Espen »
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Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #415 on: May 20, 2015, 07:53:35 AM »
Detail of the "new" calving front of the glacier (which is advancing at 6.9 m/day).

(don't forget to click)

nukefix

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #416 on: May 20, 2015, 10:23:30 AM »
I would not call it a new calving front just yet as it's still connected - I'm expecting the new piece to shatter once it breaks off completely...any day now I think :)

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #417 on: May 20, 2015, 09:07:06 PM »
I did some crude on-screen measuring to verify what my eyes are telling me: the glacier movement seems to be in rotation around the bottom of the image i.e. the top is moving faster than the bottom.  Anyone else see that?  Just an observation.

oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #418 on: May 20, 2015, 11:31:18 PM »
I did some crude on-screen measuring to verify what my eyes are telling me: the glacier movement seems to be in rotation around the bottom of the image i.e. the top is moving faster than the bottom.  Anyone else see that?  Just an observation.

I see that too. I believe Kap Zach the rock at the bottom of the picture is to blame, pinning the right-hand side of the ice flow. But best to get answers from the experts here.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #419 on: May 23, 2015, 09:32:24 PM »
The calving process is continuing at Zachariae Isstrøm:
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #420 on: May 25, 2015, 08:52:16 PM »
This time we have look at Spaltegletscher situated in into Dijmphna Sund and a part of Nioghalvfjerdsfjorden or the 79-glacier, it may soon be the end to Spaltegletscher since a serious crack is now almost crossing the whole glacier seen in the lower part of the animation seen below:
« Last Edit: May 25, 2015, 09:40:13 PM by Espen »
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Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #421 on: May 30, 2015, 09:46:30 PM »
There are indications of a large movement at Zachariae, more info when more reliable imagery is available.
« Last Edit: May 30, 2015, 09:56:21 PM by Espen »
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Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #422 on: May 31, 2015, 09:00:35 AM »
I see nothing in the Sentinel medium-res images yet (taken hours after the Landsat flew over).

(images aligned on the "new" calving front)

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #423 on: May 31, 2015, 09:43:58 AM »
Wipneus,

From where did you get the May 30 image from, in my polar view there is no image from Zach May 30?
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Wipneus

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Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #425 on: May 31, 2015, 12:26:11 PM »
Sentinel-1 Scientific Data Hub

Sorry about that, I thought the polar view site was just as quick?
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nukefix

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #426 on: May 31, 2015, 04:23:58 PM »
There's an image from the 31st as well on scihub now.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #427 on: May 31, 2015, 04:26:02 PM »
There's an image from the 31st as well on scihub now.

Already checked, thanks!
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Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #428 on: June 02, 2015, 08:07:54 AM »
12 day med-res Sentinel animation of the Zachariae calving front(s).

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #429 on: June 04, 2015, 09:10:08 AM »
But the Landsat optical image shows that  a new minor calving is taking place at the "new" calving front.

(pls click)

[EDIT: circled the feature at A-Teams's request]
« Last Edit: June 04, 2015, 06:27:46 PM by Wipneus »

A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #430 on: June 04, 2015, 04:39:05 PM »
Wipneus, any chance you could overlay some arrows or text? I'm not sure above what I should be looking at, quite a few changes to choose from. Thx! (PS: Images below have had local contrast enhancement and are inverted.)

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #431 on: June 04, 2015, 06:31:01 PM »
Wipneus, any chance you could overlay some arrows or text? I'm not sure above what I should be looking at, quite a few changes to choose from. Thx! (PS: Images below have had local contrast enhancement and are inverted.)

A-Team, I modified the post to remove the doubt what I was referring to. I cannot say your "enhancements" bring out my feature very well.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #432 on: June 06, 2015, 06:41:03 AM »
Thx for the circled feature above!

I need to know in advance what region is to be enhanced for what purpose. This may or may not be feasible. To make the second frame of the animation below, see http://www.imagemagick.org/discourse-server/viewtopic.php?t=27197

The fringes image (rgb = first, second, second dates as grays) shows the bluish fracture does not have a full length reddish counterpart, so is a new development.

The second animation co-registers fixed features west of the fracture to display geometrical distortion elsewhere, a small clockwise rotation relative to this coordinate frame but also quite bit more fracturing visible at 1.5x magnification. Here I didn't know if the path,row were the same in the two images which would minimize distortion contributed from the satellite. Click to view.
« Last Edit: June 06, 2015, 07:32:24 AM by A-Team »

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #433 on: June 06, 2015, 09:09:07 AM »
Here I didn't know if the path,row were the same in the two images which would minimize distortion contributed from the satellite.

Yes May-1 to June-2 is 32 days, 2 Landsat Cycles. Actually I show very few animations that are not from the same orbital position. I can not remember any Landsat animation that was not.

Thanks for the instructive comments!

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #434 on: June 06, 2015, 03:36:51 PM »
Quote
May-1 to June-2 is 32 days, 2 Landsat Cycles.  my animations are ~always use the same path,row.

Excellent practice. Others, in their search for pairs of cloud-free days, may not realize why this is important in avoiding artifacts, so I chased down the accession numbers (which are unambiguous in the case of Landsat-8 dates) to confirm the path,row business and look at the centers of scene (nadirs directly below satellite) which can wander a bit even with the same path,row.

Here they are both favorably near to the fracture of interest (rather than on the image margins) but displaced southeasterly by 5.4 km. This has a minimal effect compared to unavoidable sun elevation differences (and so shading), here over 7º.

This is what made possible widespread co-registration of upstream glacier features above by simple pixel shifting without the need for non-linear warping. Warping is problematic for Zachariae, Petermann and Jakobshavn because there aren't any fixed points (rocks) in the interior and everything else is in non-uniform motion. This means correcting along the coastal direction only.

I have been wrestling with the same issue of best fixed reference frame on a 15-year time series at Petermann. This is another story of a warm ocean current melting the underside of an ice shelf underside so does not have the dynamic thinning/stretching, calving and grounding line migration issues of Zachariae but instead a tapering of velocities as the main ice stream brushes against the edge of a tributary glacier contribution, which in turn brushes against a later tributary, which in turn brushes against a third tributary, which in turn scrapes along the rock wall.

Here two old fractures have remained the same distance apart and can be taken as the fixed points for alignment and rescaling. It all bears an uncanny resemblance to the Transverse Range in California, rotated as the Pacific Plate grinds past the N American.

Entity ID: LC80110032015153LGN00
Coordinates: 79.11406,-25.93111
Acquisition Date: 02-JUN-15
Path: 11
Row: 3
Sun Elevation 32.227“

Entity ID: LC80110032015121LGN00
Coordinates: 79.1478,-26.11325
Acquisition Date: 01-MAY-15
Path: 11
Row: 3
Sun Elevation 25.123º

Distances, bearings, and google earth kml provided by http://www.movable-type.co.uk/scripts/latlong.html
« Last Edit: June 06, 2015, 04:06:18 PM by A-Team »

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #435 on: June 06, 2015, 03:53:12 PM »
North East Greenland: Coldest May measured since 1949

http://www.dmi.dk/nyheder/arkiv/nyheder-2015/06/groenland-lagt-paa-is-i-maj/
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A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #436 on: June 06, 2015, 04:51:29 PM »
Espen, did you see where someone linked off-site to some most excellent plots of Greenland temperatures?

I cannot relocate that very recent post but it showed temperatures were a full month behind, almost flat-lining cold. If this keeps up, it will not be a big year for meltwater acceleration of Greenland glaciers (though would we be surprised if this stationary situation flipped to stationary extreme warmth later in the season?).

However cold air temperature will have a minimal effect on bulk ocean temperature and CTD stratification near Greenland. Quite a bit of calving front and ice shelf underside melting is driven by a change to warmer ocean. This is not global ocean warming from climate change per se (real but not responsible) but rather pre-existing warmer currents finding their way farther north under climate change and tidal exchange. At least that is the story being told for Zach, Niog, Jakobshavn and Petermann.

I'm not aware of much in the way of meltwater affecting upper Zach or Petermann. Ice deformation is much greater at depth where it is much warmer due to geothermal flux and sliding friction. This zone has only exceedingly weak couplings to the air temperatures 2-3 kms above.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #437 on: June 06, 2015, 05:17:34 PM »
A-Team, it will only have marginal effect on glacier activity, although my feeling is Zachariae etc. are slowing down at the moment.
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Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #438 on: June 06, 2015, 08:24:50 PM »
That being said (see above) a new calving row is developing:
« Last Edit: June 06, 2015, 08:36:58 PM by Espen »
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oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #439 on: June 06, 2015, 08:42:27 PM »
A-Team, it will only have marginal effect on glacier activity, although my feeling is Zachariae etc. are slowing down at the moment.

From my layman's point of view Zach seems to be calving full steam ahead, despite unfavorable conditions (low temps, frozen sea surface), but it's just a gut feeling. Could you perchance show a comparison to the calving front at this date last year? I wish I had your skills/knowhow of finding and presenting such info. Very much a newbie still.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #440 on: June 07, 2015, 02:06:16 AM »
From my layman's point of view Zach seems to be calving full steam ahead, despite unfavorable conditions (low temps, frozen sea surface), but it's just a gut feeling. Could you perchance show a comparison to the calving front at this date last year? I wish I had your skills/knowhow of finding and presenting such info. Very much a newbie still.

Last year when the sea ice in front of Zachariae melted in late August there was a lot of calving within a few days as shown by the following posts by Espen:

http://forum.arctic-sea-ice.net/index.php/topic,400.msg35513.html#msg35513
http://forum.arctic-sea-ice.net/index.php/topic,400.msg36496.html#msg36496

My guess is that those calvings were triggered by the easing of the back pressure by the sea ice.

A potential longer term effect is that the sea ice melting allows all those icebergs to move away which might ease the flow of warm waters to the calving front. If the summer were so cold that the sea ice in front of Zachariae never melts, that might have a significant negative effect.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #441 on: June 07, 2015, 05:29:24 AM »
oren asks for "perchance  a comparison to the calving front at this date last year?"

Espen had the good sense to see the changes coming in Zach and open this forum two years ago on June 25, that is to say 440 posts ago. I suspect that Espen and Wipneus between them have somewhere posted exactly the images you are seeking. If not, the easiest way to get started is with the small preview jpg images supplied by EarthExplorer.

From there it all depends on your computer set-up. I don't think any two people here use the same image processing software. People have made good efforts to describe the exact steps to follow in certain cases, notably Wipneus, sidd, and nukefix. This can be a real time and frustration saver as the satellite hosting sites offer next to nothing by way of practical tutorials.

If you can get past the download to a file that will open into a recognizable image on your monitor, the processing software needed for enhancement, cropping, comparison, and animations will have poorly documented and non-intuitive commands, a bizarre user interface such as no un-do's, and many bugs that never seem to get fixed. Followed by issues getting typepad to actually display your result as intended.

However after getting a few work flows down pat, it is great fun and not that time-consuming to pursue personal research agendas, all made possible by free access to satellite data in near real-time. Often someone here is the very first to notice and correctly interpret a new development.

There is a lot of synergy too with numerous contributors having substantial skills in one specialty or another. So Neven's project overall ends up being a very substantial climate change resource, with bloggers educating not only each other but whoever stops by wanting to take their personal understanding to the next level.

oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #442 on: June 07, 2015, 07:56:44 AM »
oren asks for "perchance  a comparison to the calving front at this date last year?"

Espen had the good sense to see the changes coming in Zach and open this forum two years ago on June 25, that is to say 440 posts ago. I suspect that Espen and Wipneus between them have somewhere posted exactly the images you are seeking. If not, the easiest way to get started is with the small preview jpg images supplied by EarthExplorer.

From there it all depends on your computer set-up. I don't think any two people here use the same image processing software. People have made good efforts to describe the exact steps to follow in certain cases, notably Wipneus, sidd, and nukefix. This can be a real time and frustration saver as the satellite hosting sites offer next to nothing by way of practical tutorials.

If you can get past the download to a file that will open into a recognizable image on your monitor, the processing software needed for enhancement, cropping, comparison, and animations will have poorly documented and non-intuitive commands, a bizarre user interface such as no un-do's, and many bugs that never seem to get fixed. Followed by issues getting typepad to actually display your result as intended.

However after getting a few work flows down pat, it is great fun and not that time-consuming to pursue personal research agendas, all made possible by free access to satellite data in near real-time. Often someone here is the very first to notice and correctly interpret a new development.

There is a lot of synergy too with numerous contributors having substantial skills in one specialty or another. So Neven's project overall ends up being a very substantial climate change resource, with bloggers educating not only each other but whoever stops by wanting to take their personal understanding to the next level.

I am SO stupid... It never occurred to me to check further upstream on this thread  ::)

Eyeballing http://forum.arctic-sea-ice.net/index.php/topic,400.msg28071.html#msg28071 compared to the current situation shows the calving front is now further back than the same time last year.
Still doesn't mean much as I am interested in the retreat speed. Next on my agenda is to subtract June 15 - June 14, comparing to June 14- June 13. And to subtract June 15 from Sep 14, and June 14 from Sep 13. And actually measure distances. I will try to do that and in the process learn some useful stuff. Thanks for the pointers.

btw I find it very interesting that Zach continues to retreat from Sep to June, compared to Jakobshavn that advances over the winter and retreats during summer.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #443 on: June 07, 2015, 12:43:37 PM »
There is a lot of synergy too with numerous contributors having substantial skills in one specialty or another. So Neven's project overall ends up being a very substantial climate change resource, with bloggers educating not only each other but whoever stops by wanting to take their personal understanding to the next level.

That was the whole idea, and I'm really glad the Forum is being used this way.  :)
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Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #444 on: June 14, 2015, 11:03:49 AM »
Calving front update, although Zachariae seems to be slowing down for the time being, the calving zone is still moving inland from 2014 (Click on image to enlarge):
The ground image is from September 2014, will be updated later in the season.
« Last Edit: June 14, 2015, 11:13:05 AM by Espen »
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Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #445 on: June 14, 2015, 11:26:42 AM »
Detail from the June 13 image, ta first "tranversal" crack in the new calving is visible in the centre of this image.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #446 on: June 14, 2015, 11:34:08 AM »
In tradition with place name giving in Greenland, I have taken the privilege to name the island south of Kap Zach "Søhesten" (The Sea Horse) in English:
« Last Edit: June 14, 2015, 02:25:44 PM by Espen »
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #447 on: June 14, 2015, 02:43:54 PM »
That's a great name for that island!

Seeing that the calving front has regressed less (on average) each year since 2010, is this proof that global warming is slowing down?  :P  (You know, one contrary cherry-picked bit of data overrides a world full of actual data.  ;D)

More Seriously, do you have ideas why 2010-11 and 2011-12 might have calved so much more than other years?  (I recall that 2012 was a big melt year for Greenland.  Would this be part of the picture?)
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Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #448 on: June 14, 2015, 03:20:09 PM »
That's a great name for that island!

Seeing that the calving front has regressed less (on average) each year since 2010, is this proof that global warming is slowing down?  :P  (You know, one contrary cherry-picked bit of data overrides a world full of actual data.  ;D)

More Seriously, do you have ideas why 2010-11 and 2011-12 might have calved so much more than other years?  (I recall that 2012 was a big melt year for Greenland.  Would this be part of the picture?)

I guess it is a combination of high melt in the area for that year and at the same time the collapse of the arch between the present calving front and the former tongue of the glacier.
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #449 on: June 14, 2015, 05:37:58 PM »
Calving front update, although Zachariae seems to be slowing down for the time being,

I am not seeing anything of a slow down.

Attached is an animation of day 148 and day 164, rendered at 7.5 m/pix. The images are shifted so that what I think is the main glacier (center of the glacier, about one calving inward) are aligned. I noted the shift (using The Gimp with layers visible in difference mode) which was 15 pixels horizontal, 1 vertical.
Ignoring the vertical, that works out as 15*7.5/16 = 7.0 m/day. Even allowing for 2 pixels error, that is still at minimum 6.1 m/day.
I would be surprised to see a slow down, in fact a speed-up is more likely.