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Tor Bejnar

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #250 on: July 21, 2015, 06:36:48 PM »
Thanks, A-Team
Arctic ice is healthy for children and other living things.

solartim27

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #251 on: July 21, 2015, 07:44:07 PM »
So, is this clouds, corrupt data, or did someone detonate a small thermonuclear device?  Looks like the left side went away, with the center portion stable.  Click to animate.
« Last Edit: July 21, 2015, 07:49:08 PM by solartim27 »
FNORD

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #252 on: July 21, 2015, 09:26:39 PM »
Interesting observation.  (Don't forget to crop after co-registration, if you can get down to 700 pixel width, animations will display w/o click.)

Those black bands -- and the disappearance of yesterday's clean rifts -- are a bit mysterious. I suppose the bands could be low, wet, salty spray (elevated dielectric) that then murk up radar penetrance. Smoke wafting across the scene? The calving front does not seem affected insofar as it can be seen at all.

Looking now at HV send-receive polarization, the bands are gone -- but so are the rifts. Are we looking at surface melt or frazil? -- this ice wasn't very thick to begin with. We need to look at other wavelengths. Hmm, Aqua showing banded clouds regionally (standing waves in air pressure). Hard to say what is underneath at Petermann ... looks like water.

s1a-ew-grd-hv-20150721t123227-20150721t123327-006909-00956a-002.tiff
s1a-ew-grd-hh-20150721t123227-20150721t123327-006909-00956a-001.tiff
« Last Edit: July 21, 2015, 09:54:10 PM by A-Team »

Espen

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #253 on: July 21, 2015, 10:07:12 PM »
Just an example from Kimmirut in Canada, watch how quickly the sea ice disappear over the last 7 days:

http://www.lookr.com/lookout/1198520951-Kimmirut#action-play-month 
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A-Team

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #254 on: July 21, 2015, 10:07:34 PM »
Here is 'NOAA" at DMI (which may refer to the NOAA-19 weather satellite instrument package). The 19th is there in the lower half to show where Petermann is located (DMI co-registers the images). The second calving of seasonal ice is clearly visible. On the upper image of July 21st, a lot of clouds cover the upper fjord. I've not seen an explanation of what the colors signify in these images.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #255 on: July 23, 2015, 06:47:15 PM »
I'm curious to see what Petermann will do now that the backpressure from seasonally frozen melange has been released. It has been cloudy lately but the 22 July 15 Landsat has the immediate calving front. This being the 23rd, the Sentinel is more to the point. No noteworthy response as yet.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #256 on: July 23, 2015, 07:10:11 PM »
A-Team, I dont believe the sea ice back pressure in Petermann Fjord play a major role, on the other hand I think melt water do, it is cutting through the glacier ice in many places, like what a Glaser do when he wants to cut a window glass.
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #257 on: July 24, 2015, 03:10:51 AM »
No matter what the glacier does, that blue and white photo looks magnificent, A-Team.
Open other end.

A-Team

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #258 on: July 27, 2015, 08:50:01 PM »
Quote
dont believe the sea ice back pressure in Petermann Fjord play a major role, on the other hand I think melt water do, it is cutting through the glacier ice in many places

It's important here to keep in mind the 7 distinct components of the Petermann system: the glacier proper, its attached floating ice shelf, the ice from the four east side tributaries, ice along the western wall, and floating melange in front of it all.

The glacier is pushing the whole system forward all year long at about 3 m per day (with mild seasonal variations). The ice shelf moves at this speed too as it is rigidly connected and there is little internal dynamics (thinning or thickening by stretching or compression).

The tributary ice is not quite keeping up and an area of rotating blocks (ball bearings) takes up the difference though there is shearing too. At its edge, this ice is essentially frozen to the eastern wall. The western wall has no tributary ice but is deformed (wrinkled longitudinally) by drag between the rock walls and the moving central ice.

The melange goes from nothing most summers to a continuous extension of the floating Nares Strait ice. If that ice is stuck, which it often is, the melange has nowhere to go even as the ice shelf keeps pushing on its rear. This compression should result in ridging and rafting by early spring but we may not have enough resolution to see it.

If you accept Newton's 3rd law, the rigidly frozen melange exerts a force to the south, equal and opposite to the force exerted on it by the ice sheet. The magnitude of this force varies seasonally.

After the irresistible force meets an immovable object business gets sorted out, this melange buttressing force still may effectively resist the opening and widening of rifts (especially those near the calving front) because these represent parts of the ice sheet moving faster than parts somewhat hung up on the tributary sides.

Rift origination in Petermann Glacier has nothing to do with melt pond draining or hydrofracturing of melt water extensional crevasses. Rifts always originate on the sides on flat ice. On the west, that means off the rock walls; on the east, on the tributary ice boundary.

No rift has ever originated in the central 2/3 of the ice sheet, hinge line or anywhere else during the satellite, aerial photographic or explorer-map eras as far as I can tell.

Rift development and tip propagation initially precede obliquely backwards towards the center for the reason given. Exposed sea water in the rift can freeze over without really healing the rift however.

In 2010 and 2012, I recall an overwintering rift developed a rift within the rift that extended through this briny thin ice which eventually came to fail fairly abruptly across the entire width as leveraged motion became prodigious. Landsat did not provide high resolution imagery in these years.

Water from any active meltwater channels or intercepted melt lakes could accrue in the rift bottom but is not material since that ice is already so thin/weak/warm/briny compared to the ~200 m ice that must be broken to extend the rift. The water has little access to the growing rift tip and lacks sufficient volume, depth and time for tip melt or hydrofracture. It will simply find a melt channel through the brine ice and exit to the fjord water below.

Rifts do originate and extend mostly in the summer season, at a time when the upstream glacier is moving at its fastest, meaning the side drag is at its highest. The ice up to the grounding line is at interior ice sheet temperatures but over the ~50 years it spends in the fjord adjust to ocean temperatures from below and solar and air heat inputs from above, as dirichlet boundary conditions of Fourier's heat equation. The issue here is not ductile vs brittle but rather tensile failure.

None of the 2015 rifts developed liquid water this year. I don't recall any liquid water in any of the 0.5 m resolution WorldView rifts for August 2014 either. Rifting is mainly just a carpenter snagging his shirt on a nail.

Now Rignot one time suggested -- because of maximal erosive cavitation just past the grounding line -- that the ice sheet could calve off everything in one giant event due to tidal flexure. That hasn't happened to date but the big news is that Andreas M is setting out to actually measure tides within the fjord, notably under the ice shelf, using differential GPS.

It is possible that large tides and resonances over bedrock sills have some responsibility for rift origination hot spots or tip propagation, in a manner reminiscent of a very slow swell (here seiche or soliton) breaking up pack ice. However that would crack the ice straight across the channel which is not the reverse herringbone pattern of the contemporary rift set.
« Last Edit: July 28, 2015, 06:51:03 AM by A-Team »

A-Team

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #259 on: July 27, 2015, 10:08:01 PM »
This year had considerable meltwater at some points in mid June to mid July but apparently not as much or as late as in some years. How though do we go about making a quantitative home comparison?

First off, we will be limited to 2013-15 because that is the range of Landsat-8 and there is no hope of a process working across different instruments.

The Landsat preview image has some possibilities: melt water shows up clearly as dark blue on medium blue. If our eye can see it, the gimp color picker can pull it.

When you click on a dark blue pixel, that defines a point (color) in the RGB color cube. However the tool has an adjustable radius in that space, enabling it to pick out every pixel in the image within that little sub-cube defined by the tolerance, either contiguously with it or globally.

Even better, the tool can be set to find a more representative average of whatever radius out from the designated pixel. By filling in a little square in an unused part of the image with this average color, it can be used as a better base color (for non-contiguous picking) even if it never exactly occurred in the original image.

The selection of meltwater pixels can often be improved by the 'grow' and 'border' commands which firm up lake boundaries by picking up off-color pixels that really belong to the melt but cannot be picked initially without making the selection too broad.

So far, so good but the initial image consists of 30 m bands 1,3, and 7 whereas there may be better combinations where meltwater really jumps out. The combinatorics of picking 3 bands out of the 10 available (10*9*8 = 720) already requires a walk-through animation generated by a script to see what was working.

Even fancier, given two representative areas (melt vs nearby ice), the distance between cluster centers in color space could be calculated in advance to eliminate many frames in the animation, or even just filter to the best (which might not be so apparent visually). This is effectively re-inventing support vector machines (see wiki) without much thought to the kernel.

To precede more rationally, it might make sense to de-correlate the Landsat bands with principle component analysis. The first 3 components then serve as RGB, presumably with beneficial effects on meltwater color space isolation. However there is the issue here of whether contrast enhancement should be provided first to the higher bands. See second link below.

Another option -- which is surprisingly effective -- is rapidly scrolling through a large number of color spaces besides RGB (still using bands 137). There is freeware for this (Dstretch) that acts as an ImageJ plugin. It has been primarily used for faint petroglyph visualization; I've discussed ages ago in other forums but don't know if it still works in ImageJ2.

http://forum.arctic-sea-ice.net/index.php/topic,154.msg34636.html#msg34636
http://forum.arctic-sea-ice.net/index.php/topic,909.msg34293.html#msg34293

A-Team

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #260 on: July 29, 2015, 11:41:28 PM »
There was quite an interesting Sentinel showing at DMI today. Despite low resolution, I am finding not a whole lot gained by downloading the very large high resolution images. In this case, only the HH polarization matched DMI features. I've attached the large version for what it is worth, s1a-ew-grd-hh-20150729t1127226-001.tiff which will need a click to display

There do seem to be things happening but without a Landsat of the same day, these brightening areas on radar reflectance are difficult to interpret. Landsat though has been cloudy. This was a huge issue for about six weeks in 2014.

The fjord ice has cleared. Again. Hopefully it stays that way until Andreas M's ship can get in.

I added July 30th. This just scans through a succession of adaptive contrast adjustments, hopefully drawing out the best of this DMI Sentinel product somewhere along the way. ImageJ animations are really easy, not the overhead of Gimp.

Landsat showed up with something for the 29th, quite a bit of it cloudy. It looks like a very small piece maybe calved off the extreme NW corner. Cracks here have not widened or extended. This has no significance to the future lifespan of this, one of the last remaining ice shelves in the Northern Hemisphere.
« Last Edit: July 31, 2015, 12:39:31 AM by A-Team »

Espen

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #261 on: August 02, 2015, 12:41:52 AM »
And here is a welcome calving to Andreas at Petermann:
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Espen

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #262 on: August 02, 2015, 01:13:56 AM »
And more shaky ground will be waiting for Andreas, the crack further down is developing:
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Espen

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #263 on: August 02, 2015, 01:44:21 AM »
Here is a revised animation showing July 31 vs August 1 2015, note the crack further down the glacier:
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A-Team

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #264 on: August 02, 2015, 07:20:27 AM »
Nice action! This is a good one to study for its mechanistic history -- growth from the vertical rift until it met the more established horizontal rift that had taken an unproductive turn to the south. We should check winds from the Hans Island AWS as well as Petermann's own (if it's still reporting).

However the pivoting that moved the northeast side out and away could just as well be attributable to retreating tidal currents tuggin on the newly unbuttressed calving edge. Note the calved piece cannot rotate because of two pinning points. Although it is still free to translate to the NNE, that may not reflect the forces available to it.

Petermann is much more favorable for time series of rapid events than Jakobshavn because of the almost daily Landsat images of the former compared to weekly for the latter.

The area of the broken off piece is  94977*56.25/1000000 = 5.34 km2, counting the pixels, using the 7.5 m/pxl square and sq m in a sq km (needs a commonsense check, maybe tomorrow). I'm not real sure why we would want to, but compare this to the 59 km2 for Manhattan Island.

The tabular berg will not tip like ones at Jakobshavn as it is ~0.1km thick (ie 100 m below, 10 m freeboard). This means the volume estimate comes in at 0.53 km3, still much larger than the inside of a Walmart SuperStore. As we know, calved ice shelves do not contribute to sea level rise as they are already floating (though this one isn't fully).
« Last Edit: August 02, 2015, 06:47:16 PM by A-Team »

A-Team

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #265 on: August 02, 2015, 07:36:04 AM »
The middle rift has not extended in the 01 Aug 15 image -- it is indistinguishable from the 31 Jul 15 in Landsat band 8 15 m. It often appears to change in the Landsat preview image, probably because of illumination or melt issues. However the tip has notably extended since mid-August 2014.

The history of any Petermann ice sheet fracture can be tracked back to the year 2000 using the previously posted image series assembled by NASA. Most have a multi-year history of initiating and extending, followed by pausing if not end-stage stagnation. Rifts never quite heal over as new ice is briny whereas ice coming off the Summit is completely fresh.

The second image was provided, as a lab notebook sketch, by Andrew Muenchow on his very informative outreach blog. It looks like they decided on a 1 1 (1+1) 1 array for their steam-drilling, tidal GPS, sediment sampling and CTD casts. This is quite a ways south, 10 km maybe, of the fracture tip area. Not that it wouldn't be hair-raising to be camped there as this broke off.
http://icyseas.org/2015/07/20/petermann-glacier-tidal-heaving/
« Last Edit: August 02, 2015, 03:40:46 PM by A-Team »

oren

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #266 on: August 02, 2015, 09:38:35 AM »
It seems that the calving took place along with clearing of the sea ice.

Espen

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #267 on: August 02, 2015, 10:09:01 AM »
It seems that the calving took place along with clearing of the sea ice.

It was a Blue Moon action?
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #268 on: August 02, 2015, 11:31:52 AM »
This image "screen dump from Google Earth" before the latest calving show a large brown area, looks like rocks but probably mud, any ideas?
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #269 on: August 02, 2015, 02:28:36 PM »
Just received a mail from the Captain on Oden, they are fighting the ice in Nares Strait  but through the worst and now entering Washington Strait.
Andreas is informed that a "parcel" is waiting around the corner.
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A-Team

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #270 on: August 02, 2015, 02:42:35 PM »
Those wonderful high resolution Worldview images in zoomed Google Earth were taken in July/August 2014 (discussed already in posts many moons ago) show lines of glacial till from tributary glaciers, notably Sigurd Berg and Porsild. Initially lateral moraines, these become medial moraines as tributaries merge. Not so common in central or northern Greenland glaciers but you can see lots of them by googling images of more erosive 'Alaska glaciers'.

At first this till looks like solid rock but that is because it is draped as a thin layer conforming to forms in the ice. The rift is not cutting through solid rock but merely through dirty ice. In some regions, the glacial flour has been redistributed by meltwater flow but mostly it is frozen solid (mud is liquid).

The till provides excellent markers for the slow-motion (decadal) shearing at the ice sheet/tributary ice boundary as shown before in earlier animations. There is no till on the northwest side because the minor tributary glaciers are not coming down off a highland and so have little erosive capability.

There is no scientific interest in the till per se as the parent rocks would provide better geological sampling. However since some members of the Muenchow expedition plan to sample Holocene moraines under the Petermann ice sheet, the question comes up, especially for the northernmost sampling site, as to whether sediment would be confused by the contribution of tributaries rather than Petermann itself.

In terms of tides, a blue moon has no significance beyond the large spring tides of any full moon syzygy. Andreas M has posted diurnal data on neap tides in the Nares Strait, including from a station just opposite Petermann.

Nothing is currently known about tidal circulation within Petermann fjord as that falls between the cracks for global tide modeling projects. We do know however from the work of E Rignot that the hinge line below Porsild can be detected by SAR fringes, that is, the boundary between grounded glacier and floating ice sheet as only the latter rises and falls with the tides.

The team will be studying tidally driven vertical motion of the floating ice sheet using differential GPS at four of their study stations, as well as the 3 m/day horizontal creep.

The range of outcomes are discussed at the iceseas link above: one extreme is the sea cave scenario in which the ice shelf is too rigid to rise with an incoming tide (meaning hydrostatic pressure rises instead), another where the ice shelf itself is rigid but flexes at the hinge line, and a third where the ice shelf can bend throughout its length to accommodate an incoming tide (ie a wave front passing through successive GPS units). Warmish ice might be flexible enough over the time scale of tides to accommodate them without crevassing.

The tides themselves are not large here, going by the nearest site with data, Discovery Bay in Canada, but it takes work to lift the many megatonnes of ice sheet even the slightest. Tides themselves cannot be equated to oceanic circulation under the ice shelf because of meltwater flows and other issues that could be more important in disrupting temperature and density stratification.

The issue really is that a stagnant layer of water under the ice sheet would exchange heat very slowly with the bottom ice, whereas the current paradigm both here and in Antarctica calls for more dynamic circulation patterns and rapid channelized melt of the underside, resulting in a shorter shelf life.
« Last Edit: August 02, 2015, 04:08:45 PM by A-Team »

A-Team

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #271 on: August 02, 2015, 03:53:24 PM »
Quote
It seems that the calving took place along with clearing of the sea ice. It was a Blue Moon action?
We have a great opportunity here to observe surface currents not only in the Nares Strait (been done) but also in the inlet to Petermann Fjord. My impression is that clearing/re-packing of the sea ice against the calving front has taken place repeatedly in the last week on an overnight time scale.

Now we have a chance to follow the journey of this particular tabular iceberg within the inlet. It has a distinct shape and a sizable area many times the size of a football field Walmart parking lot. This is of interest in determining tidal and wind driven circulation which have implications for sea water circulation under the ice shelf proper (and so its stability).

Here we are going to need coverage provided by all the open source satellites to get enough snapshots to measure velocity between them. Note for this we need timestamps. As discussed above, it is best practice to attach these to images or file names so they cannot get separated.

I see now that DMI does provide the UTC timestamp for NOAA images in the upper right corner (2015-08-02  07:27 UTC for the 02 Aug 15 below) though not for Modis Terra, Aqua or Sentinel. However the NOAA-19 imagery is really marginal for tracking our berg. We might however get images 4 times a day between Landsat, Sentinel, Aqua and Terra (depending on the A-train ordering of polar orbit satellites).
« Last Edit: August 02, 2015, 04:04:52 PM by A-Team »

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #272 on: August 02, 2015, 03:55:03 PM »
There is nothing special about the Blue Moon, that is simply only a 2nd full moon in a calendar month, but that said I believe full moon and the accompanying "tidal" movements have an impact on floating glaciers in particular, that was seen at 79 Fjord around July 31 2015  http://forum.arctic-sea-ice.net/index.php/topic,400.msg59045.html#msg59045

and to my best recollection at the 2 latest and only recorded calvings at Steensby Gletscher.
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #273 on: August 02, 2015, 06:04:02 PM »
The calf is preparing its trip to the south image from 12:50 UTC August 2 2015:
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #274 on: August 02, 2015, 07:04:18 PM »
Definitely broken away from its mooring points. Not clear if something more has happened.

Whoa ... where did all the ice go in Nares overnight?

Sentinel is perhaps showing a crack already in the cleaved piece.
« Last Edit: August 02, 2015, 07:51:48 PM by A-Team »

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #275 on: August 02, 2015, 07:55:04 PM »
I don't enough about that image to interpret what it shows, but this http://rapidfire.sci.gsfc.nasa.gov/cgi-bin/imagery/single.cgi?image=crefl1_367.A2015214154500-2015214155000.1km.jpg shows ice in Nares at 15:45 UTC

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #276 on: August 02, 2015, 08:41:29 PM »
aqua has the better view http://lance-modis.eosdis.nasa.gov/cgi-bin/imagery/single.cgi?image=crefl2_143.A2015214143000-2015214143500.500m.jpg

the ice is moving south faster below Peterman fjord, than above (north of it)where it moves not very much, which opens up an easy route for Oden which is (was?) moving at 7.7 knots http://oden.geo.su.se/map/
The ice map is misaligned on that chart (same thing happened at the start of last years cruise)
or is that just my explorer playing up?

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #277 on: August 03, 2015, 12:48:18 AM »
There is nothing special about the Blue Moon, that is simply only a 2nd full moon in a calendar month, but that said I believe full moon and the accompanying "tidal" movements have an impact on floating glaciers in particular, that was seen at 79 Fjord around July 31 2015  http://forum.arctic-sea-ice.net/index.php/topic,400.msg59045.html#msg59045

and to my best recollection at the 2 latest and only recorded calvings at Steensby Gletscher.


When watching for changes in fast ice formations I've found that a few days after a spring tide is often the most likely time to see some action. My assumption has been that the extreme tide fractures the ice & then it takes a day or so for wind or current to move the freed portion.


Terry

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #278 on: August 03, 2015, 04:51:49 AM »
Quote
I've found that a few days after a spring tide is often the most likely time to see some action.
Attribution not easy between big tide, peak melt season, melange buttressing removal, or all of the above. if this keeps up, where does it end?

I would not care to be out in a kayak right about now in front of the Belgrade Glacier chaos -- the lower rifts just shattered with the release of blocking pressure. In turn, what up-glacier is contingent on them?

Note the surface till from Sigurd Berg/Porsild being taken for a ride down the fjord, to confuse the next generation of sedimentary geologists. The calved piece is riding down a conventional flowline, no sign of cross-currents.

Viewing this same region in 2013 and 2014, it is apparent that this calving event was over two years in the making.
« Last Edit: August 03, 2015, 01:02:08 PM by A-Team »

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #279 on: August 03, 2015, 10:32:58 AM »
Just received an email from Andreas:

Espen:

Thank you for the e-mail that reached me today. It was delivered by the Captain in person to me during a science meeting, so it was shared with a few people aboard. We did indeed see the small 2-5 km^2 calving on the north-eastern side of Petermann where we will arrive tommorrow morning. There are people from 10 different countries aboard including the ice-drilling team from the British Antarctic Service that will try to drill through the ice-shelf to deploy ocean sensors below the ice cavity. I am struggling with the instrumentation for the central hole which incudes an automated weather station as well as 5 discretly sampling ocean sensors. All data will be transmitted, if I can work the eletronics and Iridium, thrugh the web, so you (and everyone else) should have almost real time access to what is happenening both above and below Petermann's ice-shelf.

Andreas
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #280 on: August 03, 2015, 12:52:22 PM »
Andreas M does a fantastic job of communicating climate research ... this is really a sea change from the past where people worked secretly, fretting endlessly over data theft and being scooped by ruthless competitors [based on what happened to Rosalind Franklin].

To get a sense what may be going on at Petermann, I looked up two PI's on the Oden grant to get a grip on their research interests (last ten papers): quite impressive. To root around in the articles, enter the names into Google Scholar, then go to Profiles (to remove hits to similar names) and then reverse-sort chronology to most recent for active links (or just paste complete titles below into regular Google search).

Alan C Mix is a professor of oceanography at Oregon State active in paleoceanography, paleoclimatology, micropaleontology and geochemistry who directs the OSU Stable Isotope lab http://stable-isotope.coas.oregonstate.edu/

Links between atmospheric carbon dioxide, the land carbon reservoir and climate over the past millennium
TK Bauska, F Joos, AC Mix, R Roth, J Ahn, EJ Brook
Nature Geoscience

Climate change decouples oceanic primary and export productivity and organic carbon burial
C Lopes, M Kucera, AC Mix
Proceedings of the National Academy of Sciences 112 (2), 332-335

Tracing Bering Sea Circulation With Benthic Foraminiferal Stable Isotopes During the Pleistocene
MS Cook, AC Ravelo, AC Mix, IM Nesbitt, N Miller
AGU Fall Meeting Abstracts 1, 08

Seismic stratigraphy of the Bering Trough, Gulf of Alaska: Late Quaternary history of Bering Glacier dynamics
A Montelli, SPS Gulick, LL Worthington, AC Mix, S Zellers, JM Jaeger
AGU Fall Meeting Abstracts 1, 1287

Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming.
SK Praetorius, AC Mix,
Science, 345(6195), 444-448.

Oxygen isotope stratigraphy in the Gulf of Alaska (IODP Exp. 341)
H Asahi, AC Mix, I Suto, CL Belanger, A Fukumura, S Gupta, S Konno, ...
AGU Fall Meeting Abstracts 1, 1286

Long-term perspective underscores need for stronger near-term policies on climate change
SA Marcott, JD Shakun, PU Clark, AC Mix, R Pierrehumbert, AP Goldner
AGU Fall Meeting Abstracts 1, 4044

Timing of Cordilleran Ice Rafting, Freshwater Discharge, and Implications for Subsurface Ventilation in the Northeast Pacific During the Last Deglaciation
S Praetorius, AC Mix, FG Prahl, MD Wolhowe, MH Davies
AGU Fall Meeting Abstracts 1, 06

A High-resolution Detrital and Oxygen Isotope Record from Flemish Pass, Labrador Sea
E deJesus, JS Hoffman, PU Clark, AC Mix
AGU Fall Meeting Abstracts 1, 1420

Advection of Sea-Ice Meltwater and Halocline Water Along the Siberian Continental Margin
D Bauch, S Torres-Valdes, I Polyakov, E Chernyavskaya, A Novikhin, ...
AGU Fall Meeting Abstracts 1, 1006


Martin Jakobsson is a professor of maringeologi och geofysik at Stockholm U

A New Digital Bathymetric Model of the World's Oceans
P Weatherall, KM Marks, M Jakobsson, T Schmitt, S Tani, JE Arndt, ...
Earth and Space Science

Mapping the Surficial Geology of the Arctic Ocean: A Layer for the IBCAO
DC Mosher, RC Courtney, M Jakobsson, C Gebhardt, L Mayer
OTC Arctic Technology Conference

Grain Size Variability and Sea Ice in Middle to Late Quaternary Sediments along the Lomonosov Ridge, Arctic Ocean
R Gyllencreutz, M O'Regan, LA Lowemark, M Jakobsson
AGU Fall Meeting Abstracts 1, 1294

An Atlas of Submarine Glacial Landforms: Modern, Quaternary and Ancient
M Jakobsson, JA Dowdeswell, M Canals, BJ Todd, EK Dowdeswell, ...
AGU Fall Meeting Abstracts 1, 0971

High-resolution Mapping of Offshore and Onshore Glaciogenic Features in Melville Bay, Northwestern Greenland
F Freire, R Gyllencreutz, S Greenwood, LA Mayer, M Jakobsson
AGU Fall Meeting Abstracts 1, 0973

A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum
MJ Bentley, CÓ Cofaigh, JB Anderson, H Conway, B Davies, ...
Quaternary Science Reviews 100, 1-9

Reconstruction of changes in the Amundsen Sea and Bellingshausen sea sector of the West Antarctic ice sheet since the last glacial maximum
RD Larter, JB Anderson, AGC Graham, K Gohl, CD Hillenbrand, ...
Quaternary Science Reviews 100, 55-86

Ross Sea paleo-ice sheet drainage and deglacial history during and since the LGM
JB Anderson, H Conway, PJ Bart, AE Witus, SL Greenwood, RM McKay, ...
Quaternary Science Reviews 100, 31-54

Acoustic evidence of a submarine slide in the deepest part of the Arctic, the Molloy Hole
F Freire, R Gyllencreutz, RU Jafri, M Jakobsson
Geo-Marine Letters 34 (4), 315-325

Middle to late Quaternary grain size variations and sea-ice rafting on the Lomonosov Ridge
M O'regan, E Sellén, M Jakobsson
Polar Research 33

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #281 on: August 03, 2015, 01:31:54 PM »
Just the Aqua and somewhat later Terra snapshots of yesterday's calving event. They did capture some intermediate states. I have not located timestamps for them. Changes in the NW corner are shadowing artifacts though this region could also go. There may be other satellite coverage but we don't have access to it.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #282 on: August 03, 2015, 04:32:53 PM »
It looks like the Oden placed a weather buoy at the mouth of the Petermann fjord. I now see temperature pressure and dew point data for there on Wundermap.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #283 on: August 03, 2015, 06:37:11 PM »
13:35 UTC:
Have a ice day!

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #284 on: August 03, 2015, 10:33:11 PM »
Quote
It looks like the Oden placed a weather buoy at the mouth of the Petermann fjord. I now see temperature pressure and dew point data for there on Wundermap.
Hmmm, is there some trick to getting it to display or is the satellite out of position to receive? I am not seeing an active station on Petermann at http://www.wunderground.com/wundermap/. There has been an AWS there for years as part of the overall Greenland network but it has not been actively reporting for the last couple of years.
« Last Edit: August 03, 2015, 10:48:11 PM by A-Team »

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #285 on: August 03, 2015, 10:53:52 PM »
could wundermap be using weatherdata from Oden itself?
http://oden.geo.su.se/map/ shows air pressure and temperature and relative humidity.
Also water temperature, wind speed and direction. It is at the entrance of Peterman fjord at low speed. The data points from earlier today show speeds of 8knots without making much progress on the map, I wonder whether that is an indication of it ramming through ice where short bursts of speed are to be expected. Comparison with worldview shows it should have entered the ice.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #286 on: August 03, 2015, 11:23:10 PM »
Makes sense. Though I've not heard of wundermap accepting mobil base stations. And it has not updated in quite a whileThey have not yet reached the edge of the icesheet and would not have set up on their first drill station. As part of differential GPS, they are placing a triangulation unit quite high on rock wall. But that wouldn't be suitable for ice shelf conditions. So ship meteorology. Unless they are just using Hans Island.

I interpret 12:50:00 GMT-700 (PDT) as local time in Corvallis, Oregon (home of PI Mix) or Pacific Daylight Time and 7 hours off Greenwich Mean Time which is UTC for our purposes. However it was 14:29 there when I retrieved the weather report.
« Last Edit: August 03, 2015, 11:28:30 PM by A-Team »

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #287 on: August 03, 2015, 11:42:37 PM »
I don't see it anymore on Wundermap so I don't know what to think. It was labeled as Buoy and 4 letters which I of course  didn't record and don't remember :(

When I clicked on it for more details it had no history graph which I interpreted as normal for a station that has just started up. Oh well not important really since the Oden provides the same data.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #288 on: August 04, 2015, 12:57:59 AM »
Do the tabular bergs that break off of Petermann get names like the ones that form in Antarctica from the ice shelves there?

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #289 on: August 04, 2015, 01:30:22 AM »
If you go back to the start of this thread two years ago  you'll find people talking about PII2012 and about its fragments later in the Nares strait thread.
Also have a look at http://icyseas.org/2012/07/17/petermann-glacier-and-2010-and-2012-ice-islands/

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #290 on: August 04, 2015, 10:08:48 PM »
At 18:50 GMT+1 Oden was back in Peterman fjord reporting 11.4m/s wind from 187 deg (i.e. south?) 5.8 deg C air temp and -1.2 deg water temp. http://oden.geo.su.se/map/
The sea ice overlay is still way out but can be switched off

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #291 on: August 05, 2015, 03:37:53 PM »
The calved pieces continue to move north along the side of the fjord with little evidence for any rotational eddies but a slight drift to the center. The area of tabular iceberg calculated above could almost be doubled given the secondary pieces, still not quite half of annual forward movement of 1.25 km * 14 width = 18 km2.

Note both polarizations show two distinct regions on the calved piece. Possibly the southern portion (right half) got sloshed with sea water during the calving process.

There appears to be additional wasting along the northwestern wall. It is hard to see in there as the tall steep walls can shadow both Landsat (sun angle) and Sentinel (forward scanning).

This Sentinel image hh hv RGB has a lot of other interesting features back on the mainland, no idea what they are or why just showing up now (end-season ablation? improved processing?)

The Oden looks to be moored at the calving front, hooray let the online science begin!
« Last Edit: August 05, 2015, 05:04:25 PM by A-Team »

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #292 on: August 05, 2015, 11:08:46 PM »
Here is a link to a nice blog post by Céline Heuzé - http://polarfever.com/2015/08/05/sea-ice-vs-glacier/ . She is on board the Oden.  There are some great pictures of the sea ice they have encountered as well as a picture of the face of Petermann

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #293 on: August 05, 2015, 11:29:50 PM »
I noticed today that the Oden is moving around and that the water temperatures are above 0C.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #294 on: August 05, 2015, 11:44:52 PM »
Nothing like being there. Sometimes looking straight down from 7,080 km is hard to interpret relative to an oblique image (say off the bridge of the Oden).

The first image follows up on the apparent debris stream along the west wall seen in Sentinel above. I managed to mostly lift off the shadows but it is still not clear whether fjord water has been able to work its way down along the rocks or the ice sheet continues over to the rocks but just with smoother ice. The ice sheet moves at a meter per day so is not frozen on.

Over at the rifted area on the east wall, it looks to be a clean break with no further rifting induce by loss of the buttressing from the first rifted ice. Note the break is right at the incoming Belgrade Glacier ice -- it will be vying for fjord space with the oncoming ice sheet. Further down, the major future rift remains dormant.

The third image shows the rather dingy-looking face of Petermann from Céline Heuzé's blog linked above (as contrast adjusted). I like to get these things on the record here because external links have a way of disappearing. It does not quite show the area we need. I presume that is Faith Glacier but photos can also get horizontally flipped.

She has an early blog post too about shipboard safety http://polarfever.com/2015/08/03/helicopter-safety-and-ctd-yoga/ and a twitter feed with more pictures. https://twitter.com/clnhz
« Last Edit: August 06, 2015, 12:09:03 AM by A-Team »

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #295 on: August 06, 2015, 09:08:30 AM »
Here is a link to a nice blog post by Céline Heuzé - http://polarfever.com/2015/08/05/sea-ice-vs-glacier/ . She is on board the Oden.  There are some great pictures of the sea ice they have encountered as well as a picture of the face of Petermann
a link from that site leads to more photos at
 https://petermannsglacialhistory.wordpress.com/2015/06/18/hello-world/

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #296 on: August 06, 2015, 06:00:34 PM »
That and the twitter site are billed as the official account for the Petermann Glacier expedition on I/B Oden - August 2015. No team member name is associated with it; possibly multiple individuals contribute. Or it is done back on campus somewhere by an outreach PR person?

It is really sketchy on photo locations for an expedition carrying all these high precision GPS units. Ordinary cell phone cameras can sometimes stamp position (don't know if the ship carries a tower emulator). It would be better to 'attach' photos to a Google Earth view (ironically as Andreas M and Espen have done so extensively here).

For example, where in the world are these people "looking for clues in rock, sediment, shells, & bone along Petermann Fjord to decipher past sea level changes" whereas Petermann fjord itself is shown on the undated Landsat drape over 30 m DEM (which wasn't effective) as far too steep and mountainous to have the flat ice-free terrain shown in the image.

Quote
Land teams have all been deployed – boulder, ice shelf, & ecology teams are on site and ready to go!

Current oceanographic data are sparse, providing only a “snapshot” of conditions  and almost nothing is known about how the oceanography of the fjord varies over time – does warm water permanently circulate beneath the floating tongue? Does turbulence in the fjord help melt the ice?
I attached today's Sentinel. The calved pieces have moved to the central part of the fjord. It is not easy to disentangle tides, currents, and wind pushing on them. However movement is 'trending' towards exit out into the Nares current.

https://twitter.com/@Petermann_ice/
https://petermannsglacialhistory.wordpress.com/2015/06/18/hello-world/
« Last Edit: August 07, 2015, 03:25:20 PM by A-Team »

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #297 on: August 07, 2015, 08:33:43 AM »
From this blog post - http://polar.se/blogg/mammal-observations-hall-land/ it is possible that some of the photos of the land might be Hall Land - I don't know where exactly that is, but other Greenland experts on the forum can perhaps locate it.  My understanding is that the land teams were delivered to their research locations via helicopter, so perhaps they are "in the vicinity" of Petermann

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #298 on: August 07, 2015, 09:20:48 AM »
A bit more info from the Swedish Polar Research Sectreteriat regarding Petermann 2015.
http://polar.se/en/expedition/petermann-2015/

Quote
The expedition will examine the relatively unexplored outlet end of this large system, by documenting changes in the grounded Petermann Glacier, its buttressing ice shelf, and ocean conditions since the end of the last glacial period. Primary scientific questions include:
1.How sensitive is Petermann ice shelf extent to documented climate changes within the Holocene?
2.Is ice-shelf response independent of, or linked to, variations in the grounded Petermann Glacier, ocean thermal conditions, or relative sea level (i.e., sill depth)?
3.What are the rates of change and variability of these systems in response to early Holocene warming, Neoglacial cooling, and post-Neoglacial (late 19th century to present) warming?

Chief scientists: Alan Mix, Oregon State University, USA and Martin Jakobsson, Stockholm University

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #299 on: August 07, 2015, 07:22:32 PM »
Am I the only one who got problems downloading Landsat data?
Have a ice day!