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Author Topic: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland  (Read 243507 times)

A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #800 on: September 19, 2016, 02:37:42 PM »
last 2016 big calving of Zachariae that we can witness in visible light.
Closing down for sure, depending on the satellite's offset from local noon. Colors will fade too just like they do for our eyes at twilight. It will still be possible to resuscitate 16-bit images for a while using extreme methods on contrast.

It looks to me like Spaltegletscher is shutting down for the year based on the 15 Sept 16 Landsat-8 LC80120022016259LGN00.

While a noteworthy fracture this summer, this ice sheet makes one almost annually in recent years. Due to glacier advance of 79N during the long cold winter, this opening will have advanced past the pivoting leverage by next summer and may become dormant like the preceding three. It could still be several years away from separating from its base and more years away from tabular icebergs in the East Greenland Current.

Issuing false alarms is not a good idea even if they get good press, any more than crying wolf worked out for that apocryphal shepherd boy in ancient Greece.

Another example would be promoting open water at the north pole -- people here know that the pole is not emblematic of the Arctic Ocean ice pack and open water there is not a meaningful indicator of climate change progression, even though this plays with the public.

Andreas Muenchow

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #801 on: September 20, 2016, 03:17:48 AM »
People on R/V Polarstern visited the area last month and placed a self-reporting mooring of ocean temperature, salinity, and currents on <1.5 m thick sea ice between the loose segments of Spaltengletscher. Data for the mooring is reported in real time at

http://www.whoi.edu/page.do?pid=20781
(pick ITM5 after scrolling to bottom of page)

located at the red dot over LC80060032016233LGN00_B8.TIF lightly re-processed using open source gdal, GMT, and good-ol' Fortran
« Last Edit: September 20, 2016, 03:24:42 AM by Andreas Muenchow »
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Bruce Steele

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #802 on: September 20, 2016, 10:36:01 AM »
Dear Dr. Muenchow, please excuse my status as a rank amateur but could you chart the location of the sill that separates the Nioghalufjerdsfjorden from the Norske Trough. Microcat 4 on the ITM 5 is located in 503.4168 dbar of depth.
There was some discussion of this depth up thread when the WHOI page first started sending data from ITM 5. Some charts show much shallower depths.
                                                          note to Terry:
I have resolved my confusion about the location of ITM5 and you were correct , some locations are in
Degrees / minutes . It shouldn't have confused me and I should be able to read a nautical chart.

The location has not moved much,  79.6841N 20.3483 W when first launched and on Sept. 16
79.6844N 20.3474W

Andreas Muenchow

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #803 on: September 20, 2016, 04:35:50 PM »
Bruce: I do not know that anyone "knows" what the exact sill depths at 79N Glacier are, however, the most recent peer-reviewed publication on this topic is Wilson and Straneo, 2015: Water exchange between the continental shelf and the cavity beneath Nioghalvfjerdsbrae, Geophysical Research Letter ...

You can find a pre-print at http://ironicmtn.com/research/79ng_hydrog.html which is the web-site of the author and PhD student (Nat Wilson) who placed the mooring with lots of help by others. Have fun.

P.S.: No excuses, we are all amateurs when it comes to nature and the way that different disciplines have to come together to blindly poke this elephant ;-)
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A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #804 on: September 20, 2016, 05:45:55 PM »
ITM5 was deployed on a 1.35 m thick ice floe at the mouth of the 79 North Glacier in Greenland on August 23, 2016 at 79° 41.0 N, 20° 20.9 W during the ARK-XXX/2 (PS100) cruise on the German Icebreaker Polarstern

Nice find. This is getting interesting -- an inspired spot to hang an instrumented line through the ice. At first the refrozen gap seems surprisingly thin at 1.35 m for ice that's 3-4 years old but maybe it makes sense for end of melt season.

Landsat-8 posts its imagery in mercator coordinates according to the UTM zone of center coordinate; those posted at the Woods Hole site are given below. Using these and the corner coordinates provided in Landsat metadata, the drill site could be located, which Andreas M already did for the 20 Aug 16 image, LC80382432016233LGN00.

The animation below places the instrument string on the 24 Jul 16 - 07 Sep 16 Sentinel pair of the earlier post #774 in which band 4 is bumped up to 5 m resolution. The drift of 52.7 m between day 236 (Aug 24th) and day 262 (Sep 19th) is 10.5 pixels on the 5 m S2A, shown as the path from the red dot to small yellow dot on the third frame.

The motion of the large block of ice immediately to the NW of the instrument string also appears in this third frame as echoed feature. This ice has moved 1.69 m/d (0.617 km/yr) at very close to a 45º trajectory NE between the two Sentinel images. This compares very favorable to the 1.99 m/day motion of the instrument string at a similar angle. Niogshalvsfjerdfjorden itself is moving more slowly and more easterly as can also be measured off this frame.

79° 41.0 N, 20° 20.9 W
79° 41' 00" N, 20° 20' 54" W
79.6833, -20.34833
513028.57 easting, 8846314 northing in UTM 27X in WGS84 (supported as a preference in Google Earth)

The .dat files provided open in any text editor; it seems the position has changed by 52.5 m over the 26.39563 days between first and last entry which amounts to drifting off to the NE at 59.2º according to GE's display (which regrettably uses a 31 Jul 2013 background image).

%year day longitude(E+) latitude(N+) GF NSAT HDOP
2016  236.58424   -20.3487  79.6840  76   9 1.1
2016  262.97987   -20.3473  79.6844  59  11 0.8

start 513020.30, 8846388.54
stop 513047.79, 8846433.49

HDOP stands for 'horizontal dilution of precision' and serves as a measure of the geometric quality of a GPS satellite configuration, helping to determine relative accuracy of a horizontal position, the smaller the better the geometry. NSAt is probably the Norsat satellite company of Vancouver BC. GF, just a wild guess, has to do with ongoing GPS recallibration of a GF-8048 unit, a commercial GPS disciplined oscillator.

To dump the whole table into a velocity plot, paste the haversine formula into excel, where I've chased down the WGS84 earth radius for this latitude in km for the final constant:
 
=ACOS(COS(RADIANS(90-Lat1)) *COS(RADIANS(90-Lat2)) +SIN(RADIANS(90-Lat1)) *SIN(RADIANS(90-Lat2)) *COS(RADIANS(Long1-Long2))) *6357.444

For updated Sentinel imagery (no further cleavage as of Sep 17th), use this link:
http://sentinel-s2-l1c.s3-website.eu-central-1.amazonaws.com/#tiles/27/X/WJ/2016/9/15/0/

The attached .txt file, when renamed .kml, allows easy addition of way stations as the instrument drifts along with the ice it is frozen into.
« Last Edit: September 20, 2016, 05:51:12 PM by A-Team »

A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #805 on: September 20, 2016, 07:34:20 PM »
Here is what the data looks like for the other items in the zipped data package. It is spreadsheet friendly.

The 'microcat' seems to be a Sea-Bird MicroCAT conductivity-temperature-depth profiler (CTD) with some conversion of water pressure to water depth needed, which will depend on both the temperature and salinity profile above as modeled from the four microcat data points. None of these sit on the sea floor; the depth was probably determined but is not overtly provided.

%ITM 5, microcat 8575 at 600 dbar, sample interval = 900 seconds
%year day temperature(C) salinity pressure(dbar)
2016  236.62501    1.1457   34.7581 503.310
2016  236.63543    1.1483   34.7576 503.310
2016  236.64584    1.1614   34.7546 503.310
2016  236.65626    1.1571   34.7648 503.310
2016  236.66668    1.1490   34.7622 503.310
...

The 'aquadopp' would be a Nortek doppler acoustic current profiler able to measure current magnitude and direction, reporting as cartesian xyz (ENup) components in m/s (though only to one significant digit). System electronics integrate doppler velocity with temperature, pressure, tilt and compass direction. 

Some 2,520 data lines have been collected so far. There is very little scatter in velocity magnitude, with east ranging from -50 to +50 mm/s, north -60 to +80 mm/s, and up from -50 to +30 mm/s. Here 50 mm/s pencils out to 0.18 km/hr, 0.097 knots, or 4.3 km/day which is about a half EW width of Spaltegletscher.

This could flush the whole underbelly in a couple of weeks if the current moved north as depicted in an earlier post (from Nat Wilson article graphic). However it doesn't very often. Only 1005 days have a northward velocity greater than zero and these average 21.5 mm/sec.  The 1117 days of southbound current average -21.3 mm/sec.

So overall the net current at aquadopp 4 has been -2.17 mm/sec which as sampled 2520 times at 900 sec intervals works out (a lot more care needed here) to -4.9 km displacement to the south which is the opposite of the under ice shelf current anticipated. Here the depth and the other three aquadopp need analysis as well.

5.58 -2.21 -34.8  sum of east, north, up components
0.0022 -0.00088 -0.01 average of east, north, up components

Incidentally, the spelling Spalte Gletscher (two words) is unacceptable. Since day one, it has been just one word, with Spaltegletsjer now being pushed, though not used to date in english language articles, Spaltegletscher preferred at Geus and M Pelto's site. Two words does not work in google search because they are two common german terms. And we don't need any Niog Halv Fjerds Fjorden fjord either.

http://www.the-cryosphere.net/9/2215/2015/tc-9-2215-2015.pdf
https://figshare.com/articles/GreenlandGlacierNames_GGNv01/1449148

%ITM 5, aquadopp 4
%year day pressure(dbar) temperature(C) east north up (m/s)
2016  236.83333 504.08   1.08   0.00  -0.03  -0.02
2016  236.84375 504.09   1.09   0.02  -0.02  -0.03
2016  236.85417 504.08   1.09   0.01  -0.03  -0.00
2016  236.86458 504.07   1.08  -0.01  -0.03  -0.02
2016  236.87500 504.09   1.08   0.01  -0.03  -0.03
...
« Last Edit: September 20, 2016, 07:40:39 PM by A-Team »

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #806 on: September 20, 2016, 08:20:51 PM »
It is actually Spaltegletscher (Crevice Glacier in English) and no N or J in it.

Named by Elmar Drastrup's 1938-39 expedition for the numerous wide crevasses. Gustav Thostrup and Alfred Wegener were delayed by the crevasses when making the first traverse of the glacier in 1907. GEUS
« Last Edit: September 21, 2016, 05:47:16 AM by Espen »
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A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #807 on: September 21, 2016, 01:52:29 PM »
Geus: named for the numerous wide crevasses.
I believe they are mistaken in that. Spaltegletscher was an ice sheet then and now, never a grounded glacier in the Holocene. It shares a grounding zone with 79N over a hundred km to the west. Crevasses are slow motion ice falls over topography. They do not form on the flats. SG extended all the way to the sea then.

'Spalte' in german translates to split or cleaved. For crevasse, they use the noun
Gletscherspalte. Or depending on context, Kluft, Schrunde or maybe Bergschrund.

Looking at the satellite photo, Hovgaard Island splits off this ice sheet from Nioghalvfjerdsfjorden much in the way a blade at the sawmill peels a sheet of veneer off a log. This would have been evident to Thostrup and Wagener on the ground.

As noted earlier, this is a distributory -- and an unusual one going off almost at a right angle. So it caught their attention and warranted recognition in the name. It's much more common to see the opposite, the confluence of ice streams as in Alaskan glaciers.

There's an alternative, namely a downstream island in the middle of the Spaltegletscher channel where the ice sheet had to flow around both sides (back in the day). However flow around obstacles is common to almost all ice flows.

P-maker

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #808 on: September 21, 2016, 07:22:31 PM »
A-Team,

you are rambling again.

"Spalte" in Danish means "spreading out" and cleavage is the result of this physical process. If there was a rise below sealevel further away from the current ice front, this could have been called "Kløve Gletscher", and they deliberately decided to call it "Spalte Gletscher".

Cheers P

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #809 on: September 21, 2016, 09:11:34 PM »
I believe it could have been translated from several meanings, since Gustav Thostrup ( A Dane) and Alfred Wegener (a German) both could use the the word Spalte, but in German most probably Spalten?
Remember none of them were glaciologist so why use fancy words or terms?
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A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #810 on: September 22, 2016, 12:28:13 AM »
Good progress, though never quite got to Drastrup actual report and dog sled route, the first page of which should be online [Danish Dog-Sledge Expedition 1938-39] but is not due to a bungled/paywalled Polar Record web site by Cambridge Univ Press, see below.

Hmmm, the 1968 map of Spaltegletscher front looks very much like today's (ie is not suggestive of imminent calving). We've seen this before on West Greenland glaciers like Epiq, no retreat since WWII. However the USGS world glacier satellite atlas says:

In figure 43 the islands of Hovgaard Ø, Lambert Land, and Schnauder 0 can be seen in the central parts of the Landsat image. Lambert Land separates the Inland Ice outlet glaciers of Nioghalvfjerdsbræ and Zachariae Isstrøm just as Hovgaard Ø splits Nioghalvfjerdsbræ into a main stream that flows into Nioghalvfjerdsfjorden and a northern outlet glacier, Spaltegletscher, that flows into Dijmphna Sund.

Spaltegletscher is reported to have had a retreat of 18 km between 1907 and the 1950’s (Davies and Krinsley, 1962),and, in spite of the errors in determining the old frontal positions, a major recession of the outlet glaciers must have taken place during the first half of the 20th century in this part of Greenland.

Davies, W.E., and Krinsley, D.B., 1962, The recent regimen of the ice
cap margin in North Greenland, in Symposium of Obergurgl, Austria (10-18 September 1962): International Association of Scientific Hydrology, Publication No. 58, p. 119-130.
http://hydrologie.org/redbooks/a058/05813.pdf free full text!!!


"Named by Elmar Drastrup’s 1938–39 expedition for the numerous wide crevasses. Gustav Thostrup and Alfred Wegener were delayed by the crevasses when making the first traverse of the glacier in 1907."

That quote comes from Anthony K. Higgins:

GEOLOGICAL SURVEY OF DENMARK AND GREENLAND BULLETIN 21 · 2010
Exploration history and place names of northern East Greenland
http://www.geus.dk/publications/bull/nr21/nr21_p001-368.pdf

"Two Danish [fur seal] hunters, Elmer [sic] Drastrup and Finn Christoffersen ..."

Drastrup, E. 1932: Blandt danske og norske Fangstmænd i Nordøst -
grønland, 132 pp. København: Gyldendalske Boghandel, Nor -
disk Forlag. [Among Danish and Norwegian Catch Men in Northeast Greenland]

Drastrup, E. 1945: Contributions to the geography of Ingolfs Fjord
and the interior of Kronprins Christians Land. Meddelelser om
Grønland 142(1), 28 pp.

Elmar Drastrup, 1909-1981, dansk polarrejsende og forfatter. Elmar Drastrup var fangstmand for Østgrønlandsk Fangstkompagni Nanok på Sandodden fangststation 1931-32, hvor han på en slædetur ved juletid fik voldsomme forfrysninger og måtte returnere til Danmark i sommeren 1932. I vinteren 1933-34 arbejdede han for Lauge Koch på stationen Eskimonæs. Sammen med fangstmanden Finn Kristoffersen foretog han Den Danske Hundeslædeekspedition 1938-39, der havde til opgave at finde en bedre slæderute til Peary Land. Ekspeditionen var finansieret af Scoresbysund Komiteen. Da den nåede Romer Sø på 81ºN, måtte den imidlertid vende om på grund af åbent vand samt unormalt stort snefald. Efter en rejse på 2350 km nåede de to mænd tilbage til udgangspunktet Sandodden i Young Sund (det nuværende Daneborg).

I 1944 var hans bopæl i Nyhavn, men i 1960'erne flyttede han til Mallorca, hvor han antagelig ligger begravet. Han var gift flere gange.

Hans forfatterskab omfatter: Blandt danske og norske Fangstmænd i Nordøstgrønland (1932), tysk udgave Grönlandjäger (1933), Fordi de udfører så store Bedrifter, (1935, omhandler de arktiske slædehunde), Nunatame – Nyt land – en grønlandsk Robinsonade (1943), Grønlandsfærd (1944, med 17 træsnit af Gitz-Johansen), Contributions to the Geography of Ingolfs Fjord and the Interior of Kronprins Christian Land (1945, Bind 142-1 i Medd. om Grønland), Med Pulk og Ski til Lapland (1945), Pelsjægerne (1946), Nanuaraq (1953, børnebog på grønlandsk), Nalagag (1946, børnebog), Polarnattens farer (1956), Med vind i sejlene (1960, om en tur over Atlanten i sejlbåd), Lille Nanok (1975, børnebog).

Elmar Drastrup, 1909-1981, Danish polar traveler and writer. Elmar Drastrup was trapper for East Greenland Fishing Company Nanok on Sandodden hunting station 1931-32, where he was on a sleigh ride at Christmas got violent frostbite and had to return to Denmark in the summer of 1932. In the winter of 1933-34, he worked for Lauge Koch at the station Eskimonæs. Along with catching the man Finn Kristoffersen, he conducted the Danish Dogsled Expedition 1938-39, which had the task of finding a better sled route to Peary Land. The expedition was funded by Scoresby Committee. When it reached the Roman Lake at 81ºN, may however turn back because of open water and abnormally high snowfall. After a journey of 2350 km, the two men back to square Sandodden in Young Sund (the current Daneborg).

In 1944 his home in Nyhavn, but in 1960 he moved to Mallorca, where he presumably is buried. He was married several times.

There had been a previous expedition to NE Greenland led by Johan Peter Koch in 1913 —and in which Alfred Wegener had been a member— that had been named "Mørkefjord Expedition".

Recent Polar Literature  Cambridge University Press
journals.cambridge.org/article_S0032247400042716
[Danish Dog-Sledge Expedition 1938-39 to north-east Greenland; includes a survey of a new route to Peary Land.]  This google search result does not lead to the indicated quote!

Map of Northeastern Greenland by Defense Mapping Agency Aerospace Center, a derivative work of txu-pclmaps-oclc-8322829_b_9.jpg, from the map collection of the Perry-Castañeda Library (PCL) of the University of Texas at Austin.  1:1,000,000 scale Operational Navigation Chart, Sheet B-9, 1st edition. Covers Greenland (Denmark). Lambert Conformal Conic Projection. Standard Parallels 73 20N and 78 40N. Central longitude 32 45W. Operational Navigation Chart B-9, 1st edition.jpg Created: 29 February 1968
« Last Edit: September 22, 2016, 01:54:28 AM by A-Team »

A-Team

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #811 on: September 22, 2016, 01:53:39 AM »
There is a 109 year record of hand-drawn maps, aerial photos, Landsat-2 imagery, and more recently interferometric studies of the Spaltegletscher region, usually as a byproduct of a study of 79N or Zachariae. Neither the early Koch + Wegener study nor the Drastrup map seem to be online though the later is available cheaply in booklet form in the UK.
« Last Edit: September 22, 2016, 02:24:24 AM by A-Team »

Andreas T

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #812 on: September 22, 2016, 08:59:49 PM »
fairly clear sky yesterday and today allows to spot Tobias Oer as a fixed speck of white among the drifting ice. (left arrow at 79° 20.3' N 15° 48.2' W)
flip betweem 21. and 22.9. on
http://go.nasa.gov/2dkHJd3
see also http://www.nature.com/nature/journal/v416/n6876/fig_tab/416035a_F1.html

the second arrow points to another area where there seems to be no movement but the location is different from the new islands mentioned in the nature article.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #813 on: September 23, 2016, 01:10:46 AM »
These high elevation sites like Petermann and Spaltegletscher have fabulous satellite return coverage -- practically daily for the Sept 2016 Sentinel 2A #tiles/27/X/WJ/2016/9/. This would for allow really neat time lapse photography if skies were clear and something was actually happening on the ice.

The preview mode at the AWS site allows fairly quick screening of cloud conditions at SG itself which does not follow from overall scene cloud percentage. This saves on downloads though these are fairly small and could be co-registered in the stack that can be co-cropped with useless dates (layers) discarded. However the downloads lose all metadata (ie date) except for band!

I located a fair number of older images, the nicest of which is a Landsat-7 from 26 Jun 2001, L71012002_00220010626 (3rd image below, not enhanced). These seem to confirm Spaltegletscher hasn't changed much in recent decades. Will this time be different?

The parent glacier 79N -- the driving force coming down off the summit ridge -- has only moderately accelerated and retreated so the issue is primarily enhanced undercutting of the floating ice shelves by adjacent ocean waters as 2016 was a mediocre year for surface melt in this area.

01 opaque
02 clear
03 clear
04 light clouds
05 clear where needed
06 clear tip only
07 clear #774
10 cloudy
11 cloudy
12 clear
13 opaque
14 so-so
15 clear, see above
16 clear low
17 too cloudy
20 too cloudy

http://sentinel-s2-l1c.s3-website.eu-central-1.amazonaws.com/#tiles/27/X/WJ/2016/9/

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #814 on: September 25, 2016, 08:57:44 AM »
It seems it is not over yet. Minor calving in the north, but big cracks open for a future bigger calving. In the mean time one of the week old calvings gives in to the stress and breaks. All in 700x700 pixels.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #815 on: October 04, 2016, 09:23:35 PM »
Shooting star over Kap Zach Sep 24 - Oct 3 2016?
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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #816 on: October 06, 2016, 11:30:29 AM »
Entering the dark winter period with not one but two radar imaging Sentinels, as S1B has entered full service. That means repeat cycles are reduced from 12 days to 6 days.
Here is an animation (30 m/pix) of such a mixed S1A/B pair. Activity can be seen in about all cracks, so another calving looks possible.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #817 on: October 07, 2016, 10:37:24 AM »
S-1A&B will be imaging the entire (almost) Greenland coast every six days...incredible! So many new things to be discovered in that data..

Year-round velocity monitoring of every outlet glacier with calving front locations suddenly possible. Optical will never be able to do this...
« Last Edit: October 07, 2016, 11:49:11 AM by nukefix »

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #818 on: October 08, 2016, 05:49:24 PM »
And it is not finished yet, another big calving event. Images in medium resolution EW (extra width 40m/pix) Sentinel mode.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #819 on: November 03, 2016, 10:34:33 AM »
Even more calvings!
« Last Edit: November 03, 2016, 10:40:57 AM by Wipneus »

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #820 on: November 03, 2016, 03:14:59 PM »
A very big calving, Zach is always on the move. I keep wondering about the position of the calving front compared with last year, I have a feeling it did not rertreat this year. Didn't succeed yet in making a gif though.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #821 on: November 03, 2016, 04:04:09 PM »
A very big calving, Zach is always on the move. I keep wondering about the position of the calving front compared with last year, I have a feeling it did not rertreat this year. Didn't succeed yet in making a gif though.

Sometime near the end of summer I thought the same, but after that the calving continued and now the retreat is substantial.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #822 on: November 03, 2016, 05:07:57 PM »
Wow. That's significant. Thank you Wipneus.
I was expecting a retreat once the sea ice cleared, as it clears the bay and reduces buttressing for the almost-calvings, but didn't notice it actually happened. Guess eyeballing works only some of the time.

johnm33

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #823 on: November 04, 2016, 12:48:08 AM »
Tides peaked on 1st/2nd, there was melt hereabouts and further north about 4 days ago, and fresh water showing up on hy-com cice. I don't know if thats outflow of surface meltwater or the north flowing coastal current causing melt, but looking at the first animation it looks like the current flowed in along the north shore and undermined the front, there's just a little more movement on the north side. Given the state of things generally I'm really starting to speculate about when the tidal forces open the floodgates here, there's going to be a lot more ice coming out of here than current estimates admit to. There's nothing to stop the bulk of the ice sheet using this exit, and for whatever reason this north-eastern corner seems to be melting fast.


Tigertown

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #824 on: November 04, 2016, 01:48:23 AM »
Looking on HYCOM SSS model, the fresh water flow appears to have started in mid-June and increased since. How does the land lay on the NE corner;as in which way does it slope? Probably a dumb question, as this flow is most likely from one or more inlets or fjords.

johnm33

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #825 on: November 04, 2016, 11:05:56 AM »
The island separating the glaciers is about 40k e-w, iirc the arrow indicates the warm current.

from upthread posted by sidd  http://membrane.com/sidd/greenland-2013/

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #826 on: December 06, 2016, 04:24:36 PM »
Some calving activity in that dark (=smooth) glacier ice on the very top of Zachariae.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #827 on: February 07, 2017, 09:33:11 PM »
Spaltegletscher a part of 79 Glacier made big headlines back in September 2016:

http://nyheder.tv2.dk/samfund/2016-09-13-enorm-isflage-river-sig-los-efter-gronlandsk-varmerekord

http://jasonbox.net/separation-manhattan-sized-ice-shelf-pieces-79-glacier-far-northwestern-greenland/

but nothing really happened and I suspect the calf (iceberg) is partly grounded:

Click on image to animate!
Have a ice day!

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #828 on: February 15, 2017, 03:34:01 PM »
Animation of three and a half month ice streaming made from 9 hi-res (IW) S1B images, 12 days apart. For size the images are scaled at 40m/pixel (from 10).
Apart of the advancing glacier, the development of cracks I notice the melt ponds that one by one lighten up.

Click to load and view the 5Meg animation.

DrTskoul

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #829 on: February 15, 2017, 04:37:48 PM »
Neat!!!
“You can know the name of a bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird... So let's look at the bird and see what it's doing -- that's what counts.”
― Richard P. Feynman

oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #830 on: February 15, 2017, 08:43:44 PM »
Very enlightening animation. ZI never sleeps, although calving seems to be on hold (for the moment).

I know there is no consensus on this, but I could swear the animation shows how the immobile sea ice in the enclosed bay slows down the glacier somewhat (and perhaps stabilizes the front a little bit as well). The debris and icebergs can be seen to be pushed before the advancing glacier, and over time the movement propagates further into the bay.

Espen

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #831 on: February 15, 2017, 08:55:56 PM »
Very enlightening animation. ZI never sleeps, although calving seems to be on hold (for the moment).

I know there is no consensus on this, but I could swear the animation shows how the immobile sea ice in the enclosed bay slows down the glacier somewhat (and perhaps stabilizes the front a little bit as well). The debris and icebergs can be seen to be pushed before the advancing glacier, and over time the movement propagates further into the bay.

I am one of them, the sea ice , icebergs, and debris etc. in the bay is just piece of cake, considering the forces coming from behind the glacier!
There must be other reasons for the break in calvings at Zachariae?
Have a ice day!

Tealight

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #832 on: February 16, 2017, 12:28:46 AM »
Very enlightening animation. ZI never sleeps, although calving seems to be on hold (for the moment).

I know there is no consensus on this, but I could swear the animation shows how the immobile sea ice in the enclosed bay slows down the glacier somewhat (and perhaps stabilizes the front a little bit as well). The debris and icebergs can be seen to be pushed before the advancing glacier, and over time the movement propagates further into the bay.

I am one of them, the sea ice , icebergs, and debris etc. in the bay is just piece of cake, considering the forces coming from behind the glacier!
There must be other reasons for the break in calvings at Zachariae?

As far as I understand glaciers, there are two main forces at play.

The first are the millions of tons of ice pushing the front forwards. This pushing force is very strong but also slow. It can't create calvings because it only pushes the ice. However it can move sea ice out of the way.

The second force are winds/currents attacking the ice from below and above. They a lot weaker than the pusing force of ice, but also quicker and can transport loosely connected ice away from the glacier. It's what we call calving. I think sea ice can be strong enough in winter to withstand this second force.

johnm33

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #833 on: February 16, 2017, 11:24:38 AM »
My 2c take a look at the bottom image on this, http://membrane.com/sidd/greenland-2013/Zachtrough/ posted by Sidd way back. The calving ice comes  off in big peices so very inert, they'll hug the coast as they move south, the melting current comes in causing ongoing if varying melt, more on the northern side, that melt water percolates through the bergs and being easy to refreeze consolidates them in the shallows behind the island barrage to the south. To get a massive breakout either that southern ice mass needs to have melted or a torrent of meltwater needs to surge out, I doubt that will happen because there's probably meltwater below the ice seeping out consistently, consolidating the ice to the south.
Now take a pinch of salt.

Andreas T

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #834 on: March 05, 2017, 01:26:59 AM »
https://icyseas.files.wordpress.com/2014/06/p2833.jpg?w=650[/img]]

This is one of the images in a post on Andreas Muenchow's blog.
https://icyseas.org/2014/06/20/icebergs-islands-and-instruments-off-isle-de-france-north-east-greenland/#more-2510
These were taken some distance away but I believe they are icebergs from Zachariae. I vaguely remember someone measuring the height of icebergs at the calving front from topled bergs as 300m?
The point I am trying to make is that these bergs have pretty high wind resistance, and I can imagine when wind blows down from the inland ice, the lined up bergs would collectively be able to shove the sea ice which is "just" a couple of meters thick into an overlapping ridge.

budmantis

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #835 on: March 05, 2017, 06:49:35 AM »
This looks like it belongs in the Antarctic, not the Arctic. That berg is massive!

Shared Humanity

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #836 on: March 06, 2017, 03:24:11 PM »
Isn't that what we are seeing in the picture? It looks like the sea ice is piling up all around that berg.

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #837 on: March 06, 2017, 04:06:34 PM »
Yes; the tabular iceberg is grounded while the multi-year sea-ice around it moves to the south.

The photo was taken during the deployment of ocean current moorings placed on the sea bed in June of 2014. More than 2 years later in August 2016 this specific mooring (as well as all other 6 along the section) were recovered with full 2-year records of ocean currents from the bottom to the surface. So no icebergs plowed across the mooring site(s) and destroyed them. For all I know this iceberg may still be sitting where it was back in 2014.

Below are time series at the edge of a 80 km wide Trough or Canyon that snakes from the Fram Strait to the coastal glaciers such as 79N and Zachariae. The vertical panels show selected depth with surface currents at the top and bottom currents near the bottom. Oceanography is physics in action on the rotating "plane" that we call earth.
« Last Edit: March 06, 2017, 04:15:41 PM by Andreas Muenchow »
A Sailor in a Changing Climate
http://IcySeas.org

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #838 on: March 08, 2017, 10:22:50 AM »
The sun is back over the Zachariae calving front.

oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #839 on: March 08, 2017, 10:13:46 PM »
Interestingly, the calving front barely advanced over the winter, although the glacier kept on going.

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #840 on: March 19, 2017, 07:41:10 AM »
Sentinel 2A is back as well. Here is a detail of the northern tip of the calving front.

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #841 on: April 02, 2017, 09:04:04 AM »
Two Sentinel 2 images, 27th March one year apart. The two images have been shifted to make the ice at the center (where the most upper crack is visible in the 2017 frame) appear stationary.

The shift (216x6pixels) works out at a glacier speed of about 5.92 m/day (+/- 0.1 m/day).

Compared to my previous estimates in the past there is no increase in speed. The measurement is certainly more up-stream where the speeds where lower anyway.

ghoti

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #842 on: April 04, 2017, 01:03:28 AM »

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #843 on: April 30, 2017, 01:19:19 PM »
hat tip to Cate: More of these photos can be seen (also by non facebook users) here
https://jeremyharbeck.smugmug.com/Field-WorkExpeditions/Operation-IceBridge-2017-Arctic
this closer view from a plane overflying the glaciers and icebergs helps to get a better view of what we see in the satellite images.
Especially recomended: finger rafting (as happens where the calving front at Zachariae pushes sea ice into such overlapping layers)
 https://jeremyharbeck.smugmug.com/Field-WorkExpeditions/OIB-Arctic-2017-Daily-Galleries/April-3rd-2017-Zachariae79N-Fram-Strait/n-RmXGWN/i-qnVxs2F
« Last Edit: April 30, 2017, 01:27:37 PM by Andreas T »

oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #844 on: April 30, 2017, 02:11:56 PM »
Thanks Andreas and Cate for the link. Great pictures.

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #845 on: June 25, 2017, 09:38:00 AM »
Some activity at last (apart from the continuing advancing of the glacier front). Calving toppled over, with others breaking.


Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #846 on: June 28, 2017, 05:43:09 PM »
Melt ponds generally increase in numbers and grow in size (but a few do not) in this animation fro two images three days apart.

zxy

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #847 on: July 06, 2017, 06:12:25 PM »
There seems to be a calving in the past 24 hours.

Updated terra image.

« Last Edit: July 07, 2017, 01:41:07 AM by zxy »

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #848 on: July 07, 2017, 07:11:54 PM »
Multiple calvings actually. Sentinel 2 images scaled to 30 m/pix for size.

Tor Bejnar

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #849 on: July 07, 2017, 08:26:17 PM »
The one-day growth of the smaller melt pond (lower left corner) is impressive!

Interesting that the mélange on the right remains frozen.
Arctic ice is healthy for children and other living things.