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Author Topic: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland  (Read 234880 times)

Andreas T

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #850 on: July 08, 2017, 02:30:48 AM »
the northern end is interesting too, the bergs formed there are narrower than elsewhere along the front where ice which is lee wide than high topples as soon as it separates from the glacier. I assume that means the ice is thinner there. Which would not be surprising with the slower movement it would be exposed to melting from below for longer.
The piece which wipneus focussed on back in March spalled off a southfacing remnant due to sideways pressure. The remnant itself has no forward movement since it is almost separate from the moving glacier.
Sentinel 2A is back as well. Here is a detail of the northern tip of the calving front.

oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #851 on: July 08, 2017, 09:12:41 AM »
The one-day growth of the smaller melt pond (lower left corner) is impressive!

Interesting that the mélange on the right remains frozen.
This animatiion and others similar to it are what led me to the unconventional conclusion that in ZI the sea ice has a slight buttressing effect (being enclosed by rocks further east), as it forces the glacier to push all the calved bergs, and crush/ridge the sea ice, in order to advance.
This is why I expect more calving activity when the sea ice clears, typically in August, and the delicately balanced front loses support.


Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #853 on: July 12, 2017, 06:48:53 PM »
One of Zachariae's old calvings decides to do something dramatic.

sidd

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #854 on: July 12, 2017, 10:39:16 PM »
Paper on the Cryosphere discuss about 79N, (and Peterman and Ryder). 79N is thinning

"At Nioghalvfjerdsbræ the total melt flux (14.2±1.6 km^3/yr water-equivalent) exceeds the inflow of ice
(10.2±0.59 km^3/yr water-equivalent) indicating present thinning of the ice tongue"

I attach part of fig 1 and fig 2. Nice paper,read the whole thing.

http://www.the-cryosphere-discuss.net/tc-2017-99/


Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #855 on: July 14, 2017, 12:39:36 PM »
A relatively narrow calving is unstable: the calvings topple over.

Tor Bejnar

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #856 on: July 14, 2017, 02:45:04 PM »
Although small, they do a good job at pushing previously calved icebergs away from the front.
Arctic ice is healthy for children and other living things.

Andreas T

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #857 on: July 15, 2017, 10:31:09 AM »
I know this has been done before but I find this so impressive I think it is worth repeating. Images are largely self explanatory I hope, icebergs tip over when they are taller than wide. These bergs are 300m tall!  Quite a splash even with ice that is already afloat (not grounded).
In physics terms the work done to move a lot of bergs a few hundred meters sideways is not easily quantified as energy required (from lowering center of mass of the berg). I expect the upwelling of meltwater below the glacier front will add to the push on the floating bergs towards the sea ice which still covers the bay.

Wipneus

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #858 on: July 15, 2017, 07:30:18 PM »
For fun: two melt ponds on the Zachariae Isstrøm, one seems to drain into the other.

oren

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #859 on: July 15, 2017, 09:09:46 PM »
For fun: two melt ponds on the Zachariae Isstrøm, one seems to drain into the other.
Thanks, amazing resolution. The draining pond's length is ~1-1.5 km assuming each pixel is 10m. Must have been quite a waterfall.

Andreas T

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #860 on: July 15, 2017, 11:09:27 PM »
reading back through the thread I was reminded of the microcat sensors of itm5 which were placed at 79N last August. What I don't understand is the change in pressure, they all seem to be at lower pressure, 10 dbar less than a year ago. This might be that somehow they are sitting less deep in the water or does anyone have a better explanation? Temperatures have risen at all 4 sensors which isn't explained by a change in depth (if that is what happened) because temperature is higher at greater depth.
http://www.whoi.edu/page.do?pid=154416

Shared Humanity

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Re: Zachariae Isstrøm / Nioghalvfjerdsfjorden / North East Greenland
« Reply #861 on: July 16, 2017, 12:27:20 AM »
For fun: two melt ponds on the Zachariae Isstrøm, one seems to drain into the other.

That is so cool.