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Author Topic: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland  (Read 335954 times)

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #550 on: November 14, 2015, 10:03:47 AM »
Zachariae Isstrøm, still moving and new future calving cracks are made in the process:
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oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #551 on: November 14, 2015, 10:57:13 AM »
The linked reference (and associated articles) discuss how the grounding line of Zachariæ Isstrøm became detached from a submarine sill and has been losing ice mass at an accelerating rate since 2012:

J. Mouginot, E. Rignot, B. Scheuchl, I. Fenty, A. Khazendar, M. Morlighem, A. Buzzi and J. Paden (12 Nov 2015), "Fast retreat of Zachariæ Isstrøm, northeast Greenland", Science DOI: 10.1126/science.aac7111


http://www.sciencemag.org/content/early/2015/11/11/science.aac7111.abstract


Abstract: "After 8 years of decay of its ice shelf, Zachariæ Isstrøm, a major glacier of northeast Greenland that holds a 0.5-meter sea-level rise equivalent, entered a phase of accelerated retreat in fall 2012. The acceleration rate of its ice velocity tripled, melting of its residual ice shelf and thinning of its grounded portion doubled, and calving is now occurring at its grounding line. Warmer air and ocean temperatures have caused the glacier to detach from a stabilizing sill and retreat rapidly along a downward-sloping, marine-based bed. Its equal-ice-volume neighbor, Nioghalvfjerdsfjorden, is also melting rapidly but retreating slowly along an upward-sloping bed. The destabilization of this marine-based sector will increase sea-level rise from the Greenland Ice Sheet for decades to come."

This is one of the most important research papers I've seen on this forum relating to Greenland. Finally ZI is getting the attention it deserves, along with some very detailed data showing the acceleration and retreat quantitatively, and providing detailed bathymetry and grounding line location.

Personally, I keep wondering whether at some point ZI will accelerate enough that it will divert ice currently discharging through NG, as both are fed from NEGIS if I understand correctly, and ZI has lost its heavy buttressing while NG is buttressed by the islands at its calving front. I'm not sure how much "cross-talk" between the drainage sub-basins is actually possible. A good way of trying to assess that is a multi-year Landsat animation of the area behind both calving fronts, showing the various flow directions on the ice-sheet and where the drainage divide actually is (which unfortunately I'm unable to produce with my limited computer resources).

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #552 on: November 14, 2015, 11:10:00 AM »
The linked reference (and associated articles) discuss how the grounding line of Zachariæ Isstrøm became detached from a submarine sill and has been losing ice mass at an accelerating rate since 2012:

J. Mouginot, E. Rignot, B. Scheuchl, I. Fenty, A. Khazendar, M. Morlighem, A. Buzzi and J. Paden (12 Nov 2015), "Fast retreat of Zachariæ Isstrøm, northeast Greenland", Science DOI: 10.1126/science.aac7111


http://www.sciencemag.org/content/early/2015/11/11/science.aac7111.abstract


Abstract: "After 8 years of decay of its ice shelf, Zachariæ Isstrøm, a major glacier of northeast Greenland that holds a 0.5-meter sea-level rise equivalent, entered a phase of accelerated retreat in fall 2012. The acceleration rate of its ice velocity tripled, melting of its residual ice shelf and thinning of its grounded portion doubled, and calving is now occurring at its grounding line. Warmer air and ocean temperatures have caused the glacier to detach from a stabilizing sill and retreat rapidly along a downward-sloping, marine-based bed. Its equal-ice-volume neighbor, Nioghalvfjerdsfjorden, is also melting rapidly but retreating slowly along an upward-sloping bed. The destabilization of this marine-based sector will increase sea-level rise from the Greenland Ice Sheet for decades to come."

This is one of the most important research papers I've seen on this forum relating to Greenland. Finally ZI is getting the attention it deserves, along with some very detailed data showing the acceleration and retreat quantitatively, and providing detailed bathymetry and grounding line location.

Personally, I keep wondering whether at some point ZI will accelerate enough that it will divert ice currently discharging through NG, as both are fed from NEGIS if I understand correctly, and ZI has lost its heavy buttressing while NG is buttressed by the islands at its calving front. I'm not sure how much "cross-talk" between the drainage sub-basins is actually possible. A good way of trying to assess that is a multi-year Landsat animation of the area behind both calving fronts, showing the various flow directions on the ice-sheet and where the drainage divide actually is (which unfortunately I'm unable to produce with my limited computer resources).

I don't see any new hard facts in these papers besides what we already knew?

This blog should be the collector of those funds they are looking for!

http://forum.arctic-sea-ice.net/index.php/topic,13.msg66022.html#msg66022
« Last Edit: November 14, 2015, 11:22:42 AM by Espen »
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A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #553 on: November 14, 2015, 01:02:48 PM »
Quote
don't see any new hard facts in these papers besides what we already knew?
The paper is very mainstream, no reason not to be. Its main purpose is to document, quantitate and explain  accelerating change at Zachariae by consolidating history over the satellite era and improving on many of the fine details of bedrock and surface flow. And the point is made, developments at Z are a bit alarming especially for its latitude.

While we knew all this here in some vague sense, it's quite a bit different pulling it together for a Science article (the review process alone took them from June into mid-October). Ask yourself, how far would we have gotten just telling peer reviewers come to this forum.

The devil is in the details. It's one thing to say Z is heating up and another to say by how much. We gesticulate at a kriged bedrock map and say 'it's retrograde, the future is bleak' but another to actually get it right. Here we learned the retrograde slope does not end at a sill 30 km from the calving front because there is a 300 m deep passageway and more retrograde slope beyond.

Where do I find this on the forum? Where did we comprehensively measure flowline velocities and acceleration? Where did we revise the ice volume discharge estimated by S Khan 2015? We copy and paste so much that it is easy to forget we observe a lot but don't actually derive too many results, mostly recycle them.

Quote
whether ZI will accelerate divert ice currently discharging through NG how much "cross-talk" between the drainage sub-basins is actually possible multi-year Landsat animation of the area behind both calving fronts flow directions on the ice-sheet and where the drainage divide actually is

Right. As the calving front (aka ocean) moves so far inland, it seems like it would melt into NG and utterly change its buttressing forces. I have not really seen any predictions about the extent of 'ice piracy' (called watershed capture on land). If this was extensive during the Eemian, Z should have excavated a far deeper channel offshore than NG -- but here we await better bathymetry.

A Landsat animation at the two flow divergences and iceshed boundaries (NG/Z and NEGIS/Stors) would be quite instructive. The slow steps there involve the download, cropping, co-registration, and consistent contrast repair of large files. Then there would be the issue of km scale and whether the motion could even be displayed at the resolution necessary. NEGIS itself is very narrow upstream with sharp shear boundaries.

It is trending right now to blame warm ocean currents for everything coming loose on Greenland glaciers. This is the tail wagging the dog. The ocean has nothing whatsoever to do with the whole anomaly of upstream NEGIS. We have to wonder if that is really attributable to a geothermal excursion and how stable that is.

Finally, note that the distribution of bottom upheavals doesn't really correlate well with any property of NG or Z described in this paper. Their significance to future flow scenarios needs to be considered.
« Last Edit: November 14, 2015, 01:37:05 PM by A-Team »

oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #554 on: November 14, 2015, 09:57:08 PM »
The linked reference (and associated articles) discuss how the grounding line of Zachariæ Isstrøm became detached from a submarine sill and has been losing ice mass at an accelerating rate since 2012:

J. Mouginot, E. Rignot, B. Scheuchl, I. Fenty, A. Khazendar, M. Morlighem, A. Buzzi and J. Paden (12 Nov 2015), "Fast retreat of Zachariæ Isstrøm, northeast Greenland", Science DOI: 10.1126/science.aac7111


http://www.sciencemag.org/content/early/2015/11/11/science.aac7111.abstract


Abstract: "After 8 years of decay of its ice shelf, Zachariæ Isstrøm, a major glacier of northeast Greenland that holds a 0.5-meter sea-level rise equivalent, entered a phase of accelerated retreat in fall 2012. The acceleration rate of its ice velocity tripled, melting of its residual ice shelf and thinning of its grounded portion doubled, and calving is now occurring at its grounding line. Warmer air and ocean temperatures have caused the glacier to detach from a stabilizing sill and retreat rapidly along a downward-sloping, marine-based bed. Its equal-ice-volume neighbor, Nioghalvfjerdsfjorden, is also melting rapidly but retreating slowly along an upward-sloping bed. The destabilization of this marine-based sector will increase sea-level rise from the Greenland Ice Sheet for decades to come."

This is one of the most important research papers I've seen on this forum relating to Greenland. Finally ZI is getting the attention it deserves, along with some very detailed data showing the acceleration and retreat quantitatively, and providing detailed bathymetry and grounding line location.

Personally, I keep wondering whether at some point ZI will accelerate enough that it will divert ice currently discharging through NG, as both are fed from NEGIS if I understand correctly, and ZI has lost its heavy buttressing while NG is buttressed by the islands at its calving front. I'm not sure how much "cross-talk" between the drainage sub-basins is actually possible. A good way of trying to assess that is a multi-year Landsat animation of the area behind both calving fronts, showing the various flow directions on the ice-sheet and where the drainage divide actually is (which unfortunately I'm unable to produce with my limited computer resources).

I don't see any new hard facts in these papers besides what we already knew?

This blog should be the collector of those funds they are looking for!

http://forum.arctic-sea-ice.net/index.php/topic,13.msg66022.html#msg66022

Well the fact that it's all concentrated in one article. Plus, at least for me: the detailed bathymetry map, the flow vectors, the division of basins between ZI and NG, the grounding line location, the measurement of acceleration, all things that I have been wondering about. I am a layman in these subjects, and not much time on my hands, so possibly it all already existed somewhere - but I couldn't find or didn't know to look for it.
In addition, I believe (thanks to your work here) that ZI is extremely important, and much overlooked, so this kind of high-profile paper is surely a step in the right direction.

nukefix

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #555 on: November 16, 2015, 08:40:43 PM »
Quote
on this radar echogram what is causing the banding upwards from the grounding line?
The scale on these radargrams is 10 pxls/km horizontally vs 200 vertically, ie there's a 20:1 compression of the horizontal. This results in exaggeration of banding. Basically as the radar passes over bedrock with steep topography, there is attenuation of backscatter by the steep walls. The Cresis radars typically collect from about 100 m x 100 m so data is not point-like.
So you're saying that if the fjord-bottom is very slanted the radar-return is smaller? In any case the previous two flights didn't show the same banding (the image is from the very recent Zacharias-paper).
Hold on folks, the LiDAR shows them as surface-depressions so they are visible both in LiDAR and Cresis. I'll postulate that these are the quasi-periodic crevasses seen also with optical sensors and SAR.

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #556 on: November 17, 2015, 10:15:23 AM »
Medium resolution (40m/pix) Sentinel 1A animation shows a calving at calving front #2. The new iceberg seems to lie on its side.

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #557 on: November 17, 2015, 05:12:10 PM »
Same as above, but instead of just using the HH polarization I create RGB images with the HV polarization for red and HH for green, blue is unused.

A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #558 on: November 18, 2015, 02:33:52 PM »
I looked at the annual velocity maps in the supplement to Mouginot 2015 to see if Zachariae might be doing a bit of ice piracy from its slower moving neighbor Nioghalvfjerdsfjorden to the north. There are six years between 2001 and 2014 for which data coverage is available for the region of potential interest.

This would totally change future discharge scenarios should Zacharia start draining the conjoined watersheds. However if this is happening, its onset is very slow. A better analysis would require the underlying data grayscales for the respective years to undo the logarithmic tinting of the Modis grayscale mosaic. The article does not indicate if or where those are available.

The third image takes the original slides for 2014 and 2001 (extreme time difference available), decomposes to HSV to capture the tint as grayscale, exponentiates those and renormalizes to [0,255] in ImageJ , then makes an RGB with blue taken as a neutral gray. Most of the relative change is near the calving fronts and again with only meagre support for upper iceshed capture.

It would also be feasible to take a pair of 2015 Landsats to see if ice flow still corresponds to their map of flowlines in the critical region.
« Last Edit: November 18, 2015, 03:58:00 PM by A-Team »

nukefix

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #559 on: November 19, 2015, 12:37:24 PM »
Scihub is down but Polarview has another EW-scene from yesterday.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #560 on: November 19, 2015, 04:13:41 PM »
S
Scihub is down but Polarview has another EW-scene from yesterday.

Yes it is usually more down than up?
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A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #561 on: November 19, 2015, 04:47:36 PM »
Quote
Yes it is usually more down than up?
Yes it is usually more down than up.

Totally incompetent interface. Not even high school level programming in the US. They seem content just having the satellite go round and round. Getting the data to the user community seems to be their lowest priority ... yet it is the highest.
« Last Edit: November 19, 2015, 04:58:20 PM by A-Team »

A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #562 on: November 20, 2015, 02:59:10 PM »
Here is a very decent composite of 1200 Sentinel wide-mode velocity determinations that shows what the instrument is capable of:

Quote
This map of Greenland ice sheet velocity was created using data from Sentinel-1A in January–March 2015 and complemented by the routine 12-day repeat acquisitions of the margins since June 2015. About 1200 radar scenes from the satellite’s wide-swath mode were used to produce the map, which clearly shows dynamic glacier outlets around the Greenland coast. In particular, the Zachariae Isstrom glacier in the northeast is changing rapidly, and recently reported as having become unmoored from a stabilising sill and now crumbling into the North Atlantic Ocean. (Colour scale in metres per day).

http://www.esa.int/spaceinimages/Images/2015/11/Ice_sheet_in_motion

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #563 on: November 20, 2015, 07:57:25 PM »
Quote
Yes it is usually more down than up?
Yes it is usually more down than up.

Totally incompetent interface. Not even high school level programming in the US. They seem content just having the satellite go round and round. Getting the data to the user community seems to be their lowest priority ... yet it is the highest.

And it continues for now 3 days:

The Sentinels Scientific Data Hub will be back soon!

Sorry for the inconvenience,
we're "performing" some maintenance at the moment.
We'll be back online shortly!


No bad feelings here (because ESA pinched the Jakobshavn event!!)

http://www.bbc.com/news/science-environment-34041531

We all know it happened between Aug. 14 and 16, but ESA can only prove it happened between Aug. 13 and 19, and that is not newsworthy especially not with BBC?

https://forum.arctic-sea-ice.net/index.php/topic,154.msg60933.html#msg60933
« Last Edit: November 20, 2015, 08:21:36 PM by Espen »
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Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #564 on: November 23, 2015, 05:04:04 PM »
ESA's data hub was back on line for a short while. Enough for a hi-res (10m/pix) detail animation of the event mentioned in %556 and #557. The calving from front #2 is seen broken in 4 parts at least.

johnm33

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #565 on: November 24, 2015, 03:27:56 PM »
Looking at the void below Nioghalvfjerdsfjorden's ice shelf it's no wonder that coastal currents and tides make no impact, its like a vast auditorium .5km high x by 75m long, plus it has a baffle on the sea bed by the entrance.

To the north of it however lies a long fjord with little ice cover which is prone to tidal movement and shows signs of attacking the ice shelf from the side. Here's a detail

and for orientation

Shared Humanity

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #566 on: November 24, 2015, 03:42:56 PM »
ESA's data hub was back on line for a short while. Enough for a hi-res (10m/pix) detail animation of the event mentioned in %556 and #557. The calving from front #2 is seen broken in 4 parts at least.

There also appears to be a small calving on the ice face that has occurred where the bergs have rolled over. Could this calving have triggered this break up?

If you look closely at the animation, you can see a dark rectangular patch appear that looks just like the calving that rolled over earlier in the season.

(Edit....Oooops...just read comment 556...already noted.)
« Last Edit: November 24, 2015, 03:49:29 PM by Shared Humanity »

Neven

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #567 on: November 26, 2015, 04:27:01 PM »
It's off-topic, but I thought this might be interesting to A-Team, Espen, Wipneus, nukefix et al:

Quote
Revealing glacier flow and surge dynamics from animated satellite image sequences: examples from the Karakoram

F. Paul
Department of Geography, University of Zurich, Zurich, Switzerland

Abstract. Although animated images are very popular on the internet, they have so far found only limited use for glaciological applications. With long time series of satellite images becoming increasingly available and glaciers being well recognized for their rapid changes and variable flow dynamics, animated sequences of multiple satellite images reveal glacier dynamics in a time-lapse mode, making the otherwise slow changes of glacier movement visible and understandable to the wider public. For this study, animated image sequences were created for four regions in the central Karakoram mountain range over a 25-year time period (1990–2015) from freely available image quick-looks of orthorectified Landsat scenes. The animations play automatically in a web browser and reveal highly complex patterns of glacier flow and surge dynamics that are difficult to obtain by other methods. In contrast to other regions, surging glaciers in the Karakoram are often small (10 km2 or less), steep, debris-free, and advance for several years to decades at relatively low annual rates (about 100 m a−1). These characteristics overlap with those of non-surge-type glaciers, making a clear identification difficult. However, as in other regions, the surging glaciers in the central Karakoram also show sudden increases of flow velocity and mass waves travelling down glacier. The surges of individual glaciers are generally out of phase, indicating a limited climatic control on their dynamics. On the other hand, nearly all other glaciers in the region are either stable or slightly advancing, indicating balanced or even positive mass budgets over the past few decades.
The Cryosphere

And EGU press release here (where the animations can be viewed).
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Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #568 on: November 26, 2015, 05:30:03 PM »
It's off-topic, but I thought this might be interesting to A-Team, Espen, Wipneus, nukefix et al:

Quote
Revealing glacier flow and surge dynamics from animated satellite image sequences: examples from the Karakoram

F. Paul
Department of Geography, University of Zurich, Zurich, Switzerland

Abstract. Although animated images are very popular on the internet, they have so far found only limited use for glaciological applications. With long time series of satellite images becoming increasingly available and glaciers being well recognized for their rapid changes and variable flow dynamics, animated sequences of multiple satellite images reveal glacier dynamics in a time-lapse mode, making the otherwise slow changes of glacier movement visible and understandable to the wider public. For this study, animated image sequences were created for four regions in the central Karakoram mountain range over a 25-year time period (1990–2015) from freely available image quick-looks of orthorectified Landsat scenes. The animations play automatically in a web browser and reveal highly complex patterns of glacier flow and surge dynamics that are difficult to obtain by other methods. In contrast to other regions, surging glaciers in the Karakoram are often small (10 km2 or less), steep, debris-free, and advance for several years to decades at relatively low annual rates (about 100 m a−1). These characteristics overlap with those of non-surge-type glaciers, making a clear identification difficult. However, as in other regions, the surging glaciers in the central Karakoram also show sudden increases of flow velocity and mass waves travelling down glacier. The surges of individual glaciers are generally out of phase, indicating a limited climatic control on their dynamics. On the other hand, nearly all other glaciers in the region are either stable or slightly advancing, indicating balanced or even positive mass budgets over the past few decades.
The Cryosphere

And EGU press release here (where the animations can be viewed).

Seems to be a reinvention of the wheel? ;) Although it has been done for years now?

In other words:  Scientific Dishonesty
« Last Edit: November 26, 2015, 05:36:17 PM by Espen »
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A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #569 on: November 26, 2015, 07:10:04 PM »
Quote
reinvention of the wheel  been done for years now   Scientific Dishonesty
Neven, thanks for bringing this to our attention. I'm afraid I don't share Espen's enthusiasm for this effort. First I double-checked the date 26 November 2015 as it is easy to mistakenly come across an old piece on the internet and think it is new, say 26 November 1995 but no, they somehow thought this was new and cutting edge, not noticing apparently that the gif89 animation spec utilized dates back, as the name itself states, to 1989.

The authors and EGU seem extremely naive -- compare this to the knock-your-socks off photorealistic effort posted today on Antarctica ocean bottom waters. http://forum.arctic-sea-ice.net/index.php/topic,622.msg66462.html#msg66462

The journal and press release don't actually offer the animations. That is a separate 64 MB zip download and unpack. The format is nice and large, 1736 × 1231, but there are a only a meagre number of frames (7) from unspecified years of the much much longer Landsat record looping at 100 ms (which makes no scientific sense as last year is not particularly relevant to the first).

The co-registration looks good but the colors are awful (given Landsat has long offered an online tutorial on natural color.) The resolution isn't specified but looks way off -- Landsat is much better than this and the project purpose really required full resolution. They should have tiled it down to 15 m and probably just stuck with band 8 grayscale. However there doesn't seem to be anything of scientific interest in the scene I looked at.

I clipped a forum-sized piece out of it, retaining original resolution, below. In the US at least, this would not be a satisfactory submission to a high school (ages 12-16) science fair project.

This is likely not a case of scientific dishonestly. Picture instead a distinguished elderly professor enjoying a three pint lunch with a old friend now a journal editor, office desks piled high with scientific reprints, shelves sagging from the weight of books and conference procedings, no need here for that internet thingamjigie, that's best left to the grandkids but hey look at what one of them showed me the other day on her portable telephone, a picture that moves, we could maybe use that in glaciology?

I've proposed elsewhere a massive pre-compute to animate the entire Landsat and Sentinel catalogs, all years, storing it at Amazon AWS, and serving whatever region visitor selected at the portal. This would have to be done by professionals because of contrast and cloud issues, not to mention significant but not insurrmountable CPU time. The end user just makes the final selection of frames and tweaks the defaulted animation speed.

This is what they do in the rest of science. Climate change is too important; we don't have time any more for people clowning around pretending to do research. They're hogging a university chair that should go to a productive young scientist. 

I am getting really fed up with glaciology on the data sharing and informatics side. We don't have time for mickey mouse any more. This means intervention on the peer review side: learn it, fix it, or forget it.
« Last Edit: November 26, 2015, 08:06:05 PM by A-Team »

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #570 on: November 26, 2015, 08:21:43 PM »
Quote
reinvention of the wheel  been done for years now   Scientific Dishonesty
Neven, thanks for bringing this to our attention. I'm afraid I don't share Espen's enthusiasm for this effort. First I double-checked the date 26 November 2015 as it is easy to mistakenly come across an old piece on the internet and think it is new, say 26 November 1995 but no, they somehow thought this was new and cutting edge, not noticing apparently that the gif89 animation spec utilized dates back, as the name itself states, to 1989.

The authors and EGU seem extremely naive -- compare this to the knock-your-socks off photorealistic effort posted today on Antarctica ocean bottom waters. http://forum.arctic-sea-ice.net/index.php/topic,622.msg66462.html#msg66462

The journal and press release don't actually offer the animations. That is a separate 64 MB zip download and unpack. The format is nice and large, 1736 × 1231, but there are a only a meagre number of frames (7) from unspecified years of the much much longer Landsat record looping at 100 ms (which makes no scientific sense as last year is not particularly relevant to the first).

The co-registration looks good but the colors are awful (given Landsat has long offered an online tutorial on natural color.) The resolution isn't specified but looks way off -- Landsat is much better than this and the project purpose really required full resolution. They should have tiled it down to 15 m and probably just stuck with band 8 grayscale. However there doesn't seem to be anything of scientific interest in the scene I looked at.

I clipped a forum-sized piece out of it, retaining original resolution, below. In the US at least, this would not be a satisfactory submission to a high school (ages 12-16) science fair project.

This is likely not a case of scientific dishonestly. Picture instead a distinguished elderly professor enjoying a three pint lunch with a old friend now a journal editor, office desks piled high with scientific reprints, shelves sagging from the weight of books and conference procedings, no need here for that internet thingamjigie, that's best left to the grandkids but hey look at what one of them showed me the other day on her portable telephone, a picture that moves, we could maybe use that in glaciology?

I've proposed elsewhere a massive pre-compute to animate the entire Landsat and Sentinel catalogs, all years, storing it at Amazon AWS, and serving whatever region visitor selected at the portal. This would have to be done by professionals because of contrast and cloud issues, not to mention significant but not insurrmountable CPU time. The end user just makes the final selection of frames and tweaks the defaulted animation speed.

This is what they do in the rest of science. Climate change is too important; we don't have time any more for people clowning around pretending to do research. They're hogging a university chair that should go to a productive young scientist. 

I am getting really fed up with glaciology on the data sharing and informatics side. We don't have time for mickey mouse any more. This means intervention on the peer review side: learn it, fix it, or forget it.

I am happy I am not a Peer!
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #571 on: November 26, 2015, 08:23:44 PM »
If this makes it into The Cryosphere, it should be possible to do something similar with the Jakobshavn/Zachariae images produced by you wonderful lot.
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #572 on: November 26, 2015, 08:34:23 PM »
I would prefer The Sun or Daily Mail. larger audience?

And a wider peer review result?
« Last Edit: November 26, 2015, 08:49:14 PM by Espen »
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #573 on: November 26, 2015, 11:30:25 PM »
Well, if you want to get into the Sun or Daily Mail, you'll have to make an animation of a glacier that is growing. If you want, I can give you David Rose's mail address. Or just send it to the GWPF and they'll forward it to their operative. ;-)
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #574 on: December 01, 2015, 10:24:01 AM »
Latest IW image from sentinel 1a. No "sudden" changes in the last 12 day sentinel 1 cycle. Cracks at new calving fronts #3-5 can be seen slightly extending/developing. General speed (measured at fron #5) is about 7.5 m/day.
The animation is scaled at 40m/pix and needs a click to start.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #575 on: December 04, 2015, 08:39:44 AM »
NASA's Earth Observatory Image of the day is dedicated to Zachariae today.

They have a nice ]comparison of 1999 with 2015.

And a You-Tube movie of the 2015 season as seen by Landsat 8:

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #576 on: December 04, 2015, 11:26:36 AM »
Quote
a nice comparison of 1999 with 2015
It is. The constancy of melt lake positions is amazing given how far forward the glacier has advanced over 15 years. There is a fair amount of inconsistency across matching lakes as to which year had the greater melt.

It is not so easy to auto-compare surface areas of liquid water between the two years because of the many shades of blue and submerged ice showing through. Depth is not doable for individual ponds without calibration. Thus a comparison of volumes of standing liquid water could only be roughly estimated. However there are methods for doing this from Landsat that have been carried out on West Greenland in recent publications.

The first animation provides an overall comparison of melt lakes. It is rotated 90º CW for purposes of better fitting forum space. The Nasa slider comparison is more effective but it doesn't seem like we can replicate it here (<div class="compare-container" id="compare-container">).

The second animation compares 3 specific melt lakes at 15 m resolution (which requires doubling down on the 1999 Landsat-7). The two scenes were aligned on fixed rocks above and below before cropping as lakes alone cannot be reliably enough aligned.

The third animation looks at details of one melt lake. Here the 1999 was contrast-adjusted and unsharp-masked to minimize distractions in comparing with 2015.

The fourth animation compares what Nasa terms the ice shelf remnant. Some features appear retained but shifted; earlier and  intermediate years are needed to get a handle on the origin and evolution of this region. Here 2015 has dramatically more melt -- possibly this area is more affected now by warming ocean. The animations all run at 400 ms.

It is a pity too see so much work (co-registering and pan-sharpening 26 Landsat-8 scenes from 2015) disappear down the rat hole of youtube -- better that Earth Observatory had archived the frames or at least listed the scene accessions needed for bulk download. It is a real nuisance to recover individual days: capturing a time series for the lakes above requires many frame grabs from the HD version, which does not include the date of the scene nor explain the relationship to the underlying 15 m resolution. And then there are the issues of mpeg codecs, intermediate fudged frames and the stupid upper drop shadow degrading the scientific value every frame.

Here we would just like to crop out a region of interest from the full screen HD display. This may be possible from http://www.youtube.com/editor if you wish to enroll and stay within the google ecosystem. This was a slide show from the beginning, not a video.
« Last Edit: December 04, 2015, 03:48:01 PM by A-Team »

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #577 on: December 04, 2015, 09:32:44 PM »
Quote
a nice comparison of 1999 with 2015
It is. The constancy of melt lake positions is amazing given how far forward the glacier has advanced over 15 years. There is a fair amount of inconsistency across matching lakes as to which year had the greater melt.

It is not so easy to auto-compare surface areas of liquid water between the two years because of the many shades of blue and submerged ice showing through. Depth is not doable for individual ponds without calibration. Thus a comparison of volumes of standing liquid water could only be roughly estimated. However there are methods for doing this from Landsat that have been carried out on West Greenland in recent publications.

The first animation provides an overall comparison of melt lakes. It is rotated 90º CW for purposes of better fitting forum space. The Nasa slider comparison is more effective but it doesn't seem like we can replicate it here (<div class="compare-container" id="compare-container">).

The second animation compares 3 specific melt lakes at 15 m resolution (which requires doubling down on the 1999 Landsat-7). The two scenes were aligned on fixed rocks above and below before cropping as lakes alone cannot be reliably enough aligned.

The third animation looks at details of one melt lake. Here the 1999 was contrast-adjusted and unsharp-masked to minimize distractions in comparing with 2015.

The fourth animation compares what Nasa terms the ice shelf remnant. Some features appear retained but shifted; earlier and  intermediate years are needed to get a handle on the origin and evolution of this region. Here 2015 has dramatically more melt -- possibly this area is more affected now by warming ocean. The animations all run at 400 ms.

It is a pity too see so much work (co-registering and pan-sharpening 26 Landsat-8 scenes from 2015) disappear down the rat hole of youtube -- better that Earth Observatory had archived the frames or at least listed the scene accessions needed for bulk download. It is a real nuisance to recover individual days: capturing a time series for the lakes above requires many frame grabs from the HD version, which does not include the date of the scene nor explain the relationship to the underlying 15 m resolution. And then there are the issues of mpeg codecs, intermediate fudged frames and the stupid upper drop shadow degrading the scientific value every frame.

Here we would just like to crop out a region of interest from the full screen HD display. This may be possible from http://www.youtube.com/editor if you wish to enroll and stay within the google ecosystem. This was a slide show from the beginning, not a video.

I have noticed this before at several location like at Humboldt Gletscher:

https://forum.arctic-sea-ice.net/index.php/topic,800.msg30731.html#msg30731
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #578 on: December 06, 2015, 01:33:44 PM »
I have noticed this before at several location like at Humboldt Gletscher:

https://forum.arctic-sea-ice.net/index.php/topic,800.msg30731.html#msg30731

I remember that post. A real eye-opener.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #579 on: December 09, 2015, 06:54:24 PM »
Also a late appearance of a Sentinel 1A IW (hi-res at 10m/px) from 4th December.
Here is a detail showing, exactly in the image center, a small opening at the position of calving front #4 (center right in this image is #1) since 22nd Nov.  The image in post #564 suggest of such an opening at calving front #5.

If last year can be taken as a guidance, these small opening may open fully during 2016.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #580 on: December 19, 2015, 03:25:42 PM »
Added a new frame for 16 December to the animation above. The crack mentioned above, and a few more in the area are opening and getting longer.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #581 on: December 22, 2015, 09:33:13 AM »
Also more north, the future calving fronts (up to #5) can be seen developing as this hi-res (10m/pix) Sentinel 1A sequence shows.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #582 on: December 22, 2015, 07:58:46 PM »
Yes Wipneus, this Monster is really amazing, the question is what will happen when the "pool" between the previous tongue and the calving front is filled with calving debris?
It is hard to get true that "Pinball" location!

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #583 on: December 23, 2015, 07:03:32 AM »
In August 2014 the sea ice cleared and the whole debris was washed away, along with major calving. This year the sea ice remained throughout August and the debris keeps piling up. I wonder what 2016 will bring.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #584 on: December 23, 2015, 09:59:21 AM »
Yes Wipneus, this Monster is really amazing, the question is what will happen when the "pool" between the previous tongue and the calving front is filled with calving debris?


Espen, all this activity of the future calving fronts indicates to me that there is little back-pressure from the the pool yet. The latest calving, a few weeks ago, managed to push quite a lot of bergs in front of it,  forwards.  Just by toppling over.

In the mean time, Sentinel 1A has increased the frequency of Zachariae images noticeably.  I could produce an image every day if I had the time (most lower resolution than the ones above)

Here is today's sequence. The (40m/pix) image is good enough to show the calving activity as well.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #585 on: January 14, 2016, 07:06:29 PM »
Zachariae Isstrøm update, still moving impressively:

Click on image to enlarge and animate!
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #586 on: January 14, 2016, 09:40:38 PM »
Animation not working for me. Maybe it's too large?

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #587 on: January 14, 2016, 10:01:16 PM »
Animation not working for me. Maybe it's too large?

Here is a smaller version:

Click on image to animate!
« Last Edit: January 15, 2016, 05:51:59 AM by Espen »
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #588 on: January 15, 2016, 08:17:48 AM »
Thanks Espen. Monster on the move.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #589 on: January 16, 2016, 05:51:44 PM »
Yes Wipneus, this Monster is really amazing, the question is what will happen when the "pool" between the previous tongue and the calving front is filled with calving debris?


Espen, all this activity of the future calving fronts indicates to me that there is little back-pressure from the the pool yet. The latest calving, a few weeks ago, managed to push quite a lot of bergs in front of it,  forwards.  Just by toppling over.

In the mean time, Sentinel 1A has increased the frequency of Zachariae images noticeably.  I could produce an image every day if I had the time (most lower resolution than the ones above)

Here is today's sequence. The (40m/pix) image is good enough to show the calving activity as well.

Great animation!

If you look at the bergy bits that are close to the tongue of ice that separated from the main glacier, (well documented by Espen) the movement of the glacier front is pushing them towards the face of the tongue. You would think the back pressure from the stationary tongue and sea ice formation would have locked these in place by now.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #590 on: January 18, 2016, 08:29:06 AM »
Zachariae still moving on with speeds 6-7 m/day at the calving fronts. In this animation of medium resolution (EW, 40m/pix) Sentinel 1A images, the boundary ( right side, middle) between sea ice/ice melange that is moving with the glacier and the more stationary sea ice "brightens" up. Ridging I presume.

 

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #591 on: January 18, 2016, 10:12:20 AM »
I came across a very nice javascript treatment of Zachariae that switches the view seamlessly upon mouse-over between separate co-registered layers for surface and bed elevations, ice thickness, surface velocity (linear or log), and satellite image.

This is a very slick container for data. Note a layer need not be static, it could be a gif animation. Also, layers can be 24-bit color png or jpg, or for that matter 16-bit tifs like Landsat.

Go to the first link below to see it in action. (The controller below won't work because of limitations in forum software.)

At the second link, I cleaned up the code into so that it displays properly at 700 pixel width with an easily modified controller so it can display our data. It is an alternative to animated gifs which gives the end-user better viewing options.

http://nholschuh.com/glaciers.html
http://forum.arctic-sea-ice.net/index.php/topic,1259.msg68520.html#msg68520

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #592 on: January 20, 2016, 04:14:56 AM »


I am happy I am not a Peer!
I would like to review that.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #593 on: January 28, 2016, 09:01:26 PM »
Zachariae Isstrøm movement January 16 to January 28 2016:

Note that Kap Zach is becoming more visible.

Please click on image to animate!
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #594 on: February 10, 2016, 04:42:51 PM »
A detail shows a cracking area where nearly every day new cracks appear, or existing cracks getting wider and longer. Resolution 10 m/pix, images 24 days (2 sentinel cycles) apart.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #595 on: February 12, 2016, 10:54:13 AM »
Possible big crack on 79N so far back it could be above the grounding line, or of little significance, we'll see.

taken from the high res version of http://www.polarview.aq/images/106_S1jpgsmall/201602/S1A_EW_GRDM_1SDH_20160211T180446_B34D_N_1.jpg

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #596 on: February 12, 2016, 12:16:55 PM »
John, here is a landsat image from August 2014 (different projection). I think most of the cracks are already there.

(click for the 30 m/pix image)

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #597 on: February 12, 2016, 01:10:00 PM »
Wipneus "John, here is a landsat image from August 2014 (different projection). I think most of the cracks are already there."
Thanks, it looks like it's moved a little downstream since then but nothing out of the ordinary. I look forward to seeing it in daylight.
[added] Looks like it was an artifact of some sort it's there on the 11th http://ocean.dmi.dk/arctic/images/MODIS/Joekelbugt/20160211s01a.ASAR.jpg  but gone on the 12th http://ocean.dmi.dk/arctic/images/MODIS/Joekelbugt/20160212s01a.ASAR.jpg
« Last Edit: February 13, 2016, 11:47:33 AM by johnm33 »

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #599 on: February 24, 2016, 10:33:51 AM »
Images across the calving front of 79N guesstimate 35km wide