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Author Topic: Quantifying ice drift  (Read 817 times)

Andreas T

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Quantifying ice drift
« on: April 18, 2017, 05:20:42 PM »
I have experimented with tracking floes in AMSR images on Worldview
 https://go.nasa.gov/2oRASQc
squashing the colour scale to 155 / 270K I have produced this animation with an attempt at measuring area exported through Fram strait in the 30 days from 2. March to 1. April
The northern edge of the marked area is at 83.8N and the area exported through Fram amounts to 178 ,400 km2
I marked another area north of Spitsbergen which shrunk by about 70,000 km2
what that means is another question, some ice cover will have will have been compacted some could have melted from below due to the warm current into this area, some will have been exported on the eastern side of Spitsbergen.
« Last Edit: April 18, 2017, 11:03:22 PM by Neven »

Neven

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Re: Quantifying ice drift
« Reply #1 on: April 18, 2017, 11:04:06 PM »
Nice work, Andreas!
Il faut cultiver notre jardin

TerryM

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Re: Quantifying ice drift
« Reply #2 on: April 19, 2017, 02:18:18 PM »
Andreas
Is it my imagination or is a greater fraction of Lincoln Sea Ice caught up in the rush to Fram this year.


Thanks
Terry

Andreas T

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Re: Quantifying ice drift
« Reply #3 on: April 19, 2017, 03:32:38 PM »
I would like to be able to answer this question, but for that much more of this kind of tracking would need to be done.
In the several attempts I have made at this I have improved my workflow but it still is quite time consuming and can really only be done for a limited number of months. I am open for suggestions on what would be worth looking into, i.e. which other years/ months to compare.

I had the same impression as you but I am not so sure it is out of the usual looking at this:https://www.climate.gov/news-features/videos/old-ice-arctic-vanishingly-rare


these are earlier versions of this method, my present settings are better I think and could be a standard for further work:
I tried to get an estimate of area  exported through Fram strait by tracking floes in worldview's AMSR2 layer https://go.nasa.gov/2ovmD1c
this is rather laborious, I made screenshots in approx 4 day steps, tracking backwards by frequent toggling layers in GIMP as recommended by A-team some while back
The red dots show position ice floes near the 80deg latitude  on the April 14th and where they were on February 12th. The outlined area is what has gone or is about to disapear via the Greenland sea.
thank you Wipneus, nice to see a little "under the bonnet" of the PIOMAS model

The purpose of my effort here is to get a comparison via a different approach of the current rate of export with other years (although this is too cumbersome to do for a lot more months)
While AMSR2 data is only available since 2016, there are AMSRE data shown on worldview and I picked 2009 as an example of high export in the PIOMAS output.

I am attaching an animation of Feb / Mar / Apr 2009 with ice area which crossed 80N before 1. May marked by red dots and orange lines at end of month
a bit of work in progress but I want to see if this works before I continue
position of the dots on 2. Feb 2009:
 84,9N / 28.2W
 85.7N / 2.9W
 85.2N/ 22.8E
 eastern edge 25E

TerryM

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Re: Quantifying ice drift
« Reply #4 on: April 19, 2017, 08:00:12 PM »
Thanks
Wasn't suggesting a whole raft of work for you.
Your link seems to show that in some years the Lincoln sea ice squats down in it's niche, while in others the ice flees across the crest of Greenland and escapes the Arctic through Fram. Believe I was remembering the former to be more a regular occurrence than reality shows.


Terry

Andreas T

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Re: Quantifying ice drift
« Reply #5 on: May 06, 2017, 09:13:02 AM »
I have made another animation for May which surprised me with a smaller area export.
Northern edge of the marked floes on 2. April was 82.9N i.e. 322km from their position on 2. May (the date chosen for visibility)
The marked area is 136500 square km
I have marked points which do not lie on the 80N parallel on 2. 5. because I wanted to see what happens between the converging floes.
It would be interesting to look at the area north of Svalbard where ice is compacting and PIOMAS and Cryosat are showing thickness anomalies but it is difficult to track floes there, the compaction it seems makes it look more amorphous in the AMSR images (weather effects are not helping either)
Svalbard has seen snowfalls in April, possibly that area too?

This of course is area I would expect volume exported to be larger because thicker ice is leaving, and that is shown by Wipneus in the PIOMAS thread.
« Last Edit: May 06, 2017, 09:18:33 AM by Andreas T »