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Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2100 on: June 19, 2016, 08:24:44 AM »
And an animation of the Nares Strait were the heat is now torching the ice and the cracks in the central pack are now closer than ever (this year).

oren

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Re: Home brew AMSR2 extent & area calculation
« Reply #2101 on: June 19, 2016, 08:46:49 AM »
The blue ice in Kane Basin shows up beautifully.

Andreas T

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Re: Home brew AMSR2 extent & area calculation
« Reply #2102 on: June 20, 2016, 01:30:26 AM »
And an animation of the Nares Strait were the heat is now torching the ice and the cracks in the central pack are now closer than ever (this year).
I know that the darkening in these animations is often a temporary effect but this one shows areas south and west of Resolute going a full black which can be seen on worldview of 19.6. as fully ice covered (albeit with surface melt) http://go.nasa.gov/1tvFPgj which is a bit surprising
Same about those fjords in Ellesmere island

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2103 on: June 20, 2016, 05:28:07 PM »
Extent is just dropped a bit, since 2012 is also in a (temporary) slowdown the relative standings stay comparable.

Update 20160619.

Extent: -26.9 (-478k vs 2015, -549k vs 2014, -945k vs 2013, -92k vs 2012)
Area: -77.5 (-403k vs 2015, -424k vs 2014, -670k vs 2013, -65k vs 2012)
 
You will find the updated graphs in the top post

The only regional extent worth mentioning is Greenland Sea that dropped another -18k
Area went down stronger with the CAA clearly going strong again (-41k), Greenland Sea some less at -29k and Chukchi -20k. Small increases in Kara, Beaufort and Laptev (about +12k each).

The regional delta image is the Nares Strait. The melting and cracking in the Lincoln Sea is getting stronger still.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2104 on: June 20, 2016, 05:33:37 PM »
The animation is of the Hudson region where the ice is now feeling the heat.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2105 on: June 20, 2016, 05:44:43 PM »
The surface melting images from ADS are back. The "melting extent" that I calculate from them has increased somewhat but is behind recent years.

Lord M Vader

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Re: Home brew AMSR2 extent & area calculation
« Reply #2106 on: June 20, 2016, 05:52:08 PM »
Wipneus,  Hudson is "feeling the Bern"  ;D

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Re: Home brew AMSR2 extent & area calculation
« Reply #2107 on: June 20, 2016, 10:46:44 PM »
The animation is of the Hudson region where the ice is now feeling the heat.
There is a heat dome building in SW North America right now bringing temperatures which are flirting with the 50C mark.

Over the next few days that heat is expected to build NE across the continent all the way to the Arctic.

Hudson's Bay should start feeling it in the form of 25C+ temperatures in another day or so.
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Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2108 on: June 21, 2016, 08:35:41 AM »
Slow decline of extent and a bump in area!

Update 20160620.

Extent: -36.0 (-449k vs 2015, -460k vs 2014, -935k vs 2013, -112k vs 2012)
Area: +53.6 (-215k vs 2015, -222k vs 2014, -541k vs 2013, +77k vs 2012)
 
You will find the updated graphs in the top post

Extent dropped in Kara and Baffin, -19k and -17k. An increase in the CAA (+16k).
Area Increased in many regions CAB most (+32k).  Baffin, Hudson, CAA and Greenland Sea each about +20k. The only "reliable" region is Baffin that lost -23k.

The regional delta-map is the CAA. I some places the drop in concentration continues, but in many others the colors have changed. Temporary no doubt.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2109 on: June 21, 2016, 08:45:49 AM »
The animation is of the Beaufort region. Extent has been stable for the the past three weeks.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2110 on: June 21, 2016, 08:52:30 AM »
And the surface melting situation according to ADS/Jaxa data has changed little. That means it is low for the years for which we have data.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2111 on: June 21, 2016, 07:48:05 PM »
Extent has been stable for the the past three weeks.

That must be the only thing that has remained stable

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2112 on: June 22, 2016, 05:34:33 PM »
The daily "home brew" report, belated and short.

Still leading 2012 (and the rest of my limited data set):

Update 20160621.

Extent: -83.1 (-487k vs 2015, -452k vs 2014, -931k vs 2013, -156k vs 2012)
Area: -153.3 (-367k vs 2015, -255k vs 2014, -640k vs 2013, -138k vs 2012)
 
You will find the updated graphs in the top post

Hudson Kara and Baffin declined most in extent (-27k, -15k and -15k)
Hudson and  Kara  declined most in area (-44k and -41k).

In the attached delta map little or nothing can be seen of the arctic low.





Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2113 on: June 22, 2016, 05:41:42 PM »
The development of the arctic low animated.

(needs a click)
« Last Edit: June 22, 2016, 05:48:05 PM by Wipneus »

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Re: Home brew AMSR2 extent & area calculation
« Reply #2114 on: June 22, 2016, 05:50:35 PM »
The activity of the arctic low is very recognizable in ADS/Jaxa melt data. As a result the melt extent bumped.

TerryM

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Re: Home brew AMSR2 extent & area calculation
« Reply #2115 on: June 22, 2016, 06:02:05 PM »
The development of the arctic low animated.

(needs a click)


Every where that I see through the clouds I see water &/or rubble.
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Re: Home brew AMSR2 extent & area calculation
« Reply #2116 on: June 23, 2016, 07:49:11 AM »
Quote
Everywhere that I see through the clouds I see water &/or rubble.
Large bands of dodgy ice on June 22nd and 23rd, shown is a small portion of 250 m Aqua visible. The little by way of recent cloud-free scenes of the pole area do however show a fairly conventional fractured but reannealed ice pack.
« Last Edit: June 23, 2016, 08:07:51 AM by A-Team »

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Re: Home brew AMSR2 extent & area calculation
« Reply #2117 on: June 23, 2016, 11:22:58 AM »
Centuries keep 2016 ahead of 2012.

Update 20160622.

Extent: -112.0 (-540k vs 2015, -477k vs 2014, -974k vs 2013, -156k vs 2012)
Area: -161.5 (-464k vs 2015, -406k vs 2014, -776k vs 2013, -258k vs 2012)
 
You will find the updated graphs in the top post

Regional extent Kara had a strong decline: -34k. Chukchi, ESS, Laptev, Baffin and Hudson had smaller drops about -12k each.
Regional area decline stron in the CAB (-60k), Laptev (-31k) and Kara (-29k). The CAA showed a increase of +36k.

Attached the arctic delta image. I think you can see the effects of the clear skies after the arctic low has passed.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2118 on: June 23, 2016, 12:16:38 PM »
The regional animation is from the Canadian Archipelago. Winds from the central Arctic, close the gap between the islands and the central pack.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2119 on: June 23, 2016, 12:21:16 PM »
The effects of the polar low still linger. The surface melting in the central pack increased even more as a result.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2120 on: June 23, 2016, 12:56:50 PM »
The 2016 PROPORTION of surface melt area to extent is in first place now!
« Last Edit: June 23, 2016, 01:11:13 PM by Thawing Thunder »
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Re: Home brew AMSR2 extent & area calculation
« Reply #2121 on: June 23, 2016, 02:18:33 PM »
The regional animation is from the Canadian Archipelago. Winds from the central Arctic, close the gap between the islands and the central pack.

Is it just me, or does anyone else see smaller floes going poof in the Beaufort whenever they look at one of those animations? It really seems like ice is disappearing there, even if the extent and area numbers aren't dropping that fast. I wonder how long it'll take before those big thick floes start going poof too?

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Re: Home brew AMSR2 extent & area calculation
« Reply #2122 on: June 23, 2016, 04:07:18 PM »
The CAA ice pack looks solid enough, shown at various levels of zoom taken  from S1A_EW_GRDM_1SSH_20160621 at http://www.polarview.aq/arctic. This gets through the clouds ok -- with good interpretability at respectable resolution -- but not necessarily where and when it's most wanted!

The lower images show where the corner of this S1A touches on Ellesmere Island, passing through a bit of Ward Hunt ice shelf.
« Last Edit: June 23, 2016, 05:29:51 PM by A-Team »

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Re: Home brew AMSR2 extent & area calculation
« Reply #2123 on: June 23, 2016, 05:02:19 PM »
The regional animation is from the Canadian Archipelago. Winds from the central Arctic, close the gap between the islands and the central pack.

Is it just me, or does anyone else see smaller floes going poof in the Beaufort whenever they look at one of those animations? It really seems like ice is disappearing there, even if the extent and area numbers aren't dropping that fast. I wonder how long it'll take before those big thick floes start going poof too?

In a word, yes. And not just there, either. Until recently in Beaufort this has been not so much the huge MYI floes furthest south as a continuous thinning out of the more heterogeneous mix coming up behind them. Then two days ago several of the very largest lost their snow cover to reveal almost nothing underneath, and stared to disintegrate.

I've been resisting posting too much for fear of sounding overly combative, but all the talk of this season's melt as "tepid" and "anaemic" seems to ring very hollow when you look at the actual ice.

When you do so you can see ubiquitous evidence of ongoing collapse in surface integrity (esp. increasing fragmentation & mobility), which not only bodes ill for the future, but also arguably confounds efforts to track extent and area from day to day, on a coarse grid, under continuous cloud cover, and confuses those who rely on these metrics as a measure of progression.


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Re: Home brew AMSR2 extent & area calculation
« Reply #2124 on: June 23, 2016, 06:50:28 PM »
Quote
confounds efforts to track extent and area from day to day, confuses metrics.
Right. The original purpose of time series like extent and volume was they went back far enough in time to allow statistical establishment of trends in the face of considerable natural (and unnatural) variability.

However as the ice and atmosphere change character, it is becoming increasingly dangerous to rely on older data for forward predictions or reassurances.

Below is a 15-23 June time series for the Beaufort Gyre. I am not seeing too much by way of disappearing floes though there has been further fragmentation, additional blueing, and rather remarkable extent of independent floe movement.

On the obscure technical side, you may have noticed WorldView posts the latest image as 'corrected reflectance (true color)' when in fact it is only color-corrected later in the day when all the slices of pie have come in.

The animation below adjusts the final frame of June 23rd to more or less match the tone of the earlier dates. What Nasa seems to be doing is squeezing the high end range of 'yellow' (which is conveniently done in ImageJ under the Adjust --> Color Balance). We've discussed a similar fix last August for Landsat-8 on the Greenland forums.

The satellite has to look down through the whole atmospheric column to see the ice so this would be a correction for round-trip Raleigh scattering of sunlight. An actual ocean buoy moored off Hawaii provides for 'vicarious calibration' of true ocean color in some applications.
https://en.wikipedia.org/wiki/Marine_Optical_Buoy

For our purposes, it is dicey to look at a single date and say wow that floe looks blue, time to twitter the Arctic Methane Emergency Group about tomorrow's catastrophic melt-out. However, people here experienced with this imagery over several melt seasons, upon perceiving a blueing trend over a dozen consecutive dates, after discounting cloud effects, despite their uncalibrated monitor, are justified in bringing it to our attention, be it interpreted as snow melt, surface melt pond formation, increased ice translucency, or floe pixels mixing it up with adjacent open leads.
« Last Edit: June 24, 2016, 03:27:13 PM by A-Team »

oren

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Re: Home brew AMSR2 extent & area calculation
« Reply #2125 on: June 23, 2016, 08:21:29 PM »
Below is a 15-23 June time series for the Beaufort Gyre. I am not seeing too much by way of disappearing floes though there has been further fragmentation, additional blueing, and rather remarkable extent of independent floe movement.

In the lower left of the animation it seems that there is a counter-clockwise vortex in the Beaufort taking floes on wild rides, directly opposing the clockwise Gyre. Amazing how this can happen.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2126 on: June 23, 2016, 08:49:33 PM »
Quote
counter-clockwise vortex in the Beaufort taking floes on wild rides
It's a bit of challenge to reconcile the various motions with surface winds history at GFS nullschool, what is known about near-surface currents, shelf bathymetry, and ongoing peak discharge from the Mackenzie. The animation below is cut out from the larger one above, scaled up 3x, and slowed slightly.

The cross-post at 2016 Melting Season compares radar to visible for the small floe on far left, midway. I'll look in a bit if the larger fracturing floe showed any predisposition on the June 16th S1A date available.

http://forum.arctic-sea-ice.net/index.php/topic,1493.msg81165.html#msg81165

Andreas T

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Re: Home brew AMSR2 extent & area calculation
« Reply #2127 on: June 23, 2016, 09:26:40 PM »
Quote
counter-clockwise vortex in the Beaufort taking floes on wild rides
It's a bit of challenge to reconcile the various motions with surface winds history at GFS nullschool, what is known about near-surface currents, shelf bathymetry, and ongoing peak discharge from the Mackenzie.
.....

The key to an understanding of what happens there is keeping in mind that this motion is taking place in three dimensions whereas we are looking at two dimensional projections. You would need a pretty good ocean model and current density profiles to fit all the pieces of the puzzle together here.
How does the presence of ice affect drag of wind on the ocean surface?  What is the momentum of deeper water masses?  I suspect a plot of elevation of the water surface would be interesting too, just add a few more factors to A-teams list.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2128 on: June 23, 2016, 09:31:00 PM »
It strikes me, we need to remember this isn't happening on a flat plane.

With those floes moving towards the coast, especially the larger ones, it seems to me some of the movement is driven by coriolis effect.  Upon running south into an area with a different rotational velocity, the force applied breaks them up.  Might it be, that 70-75 degrees of latitude might be a point where the gradient in those forces increase?  <cracks open a few old textbooks>

[edit:  Seems AndreasT was thinking along the same lines.]
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Re: Home brew AMSR2 extent & area calculation
« Reply #2129 on: June 23, 2016, 09:57:58 PM »
Good suggestions. I suppose each floe has a different keel and sail configuration, as well as draft. That small one just twirling around might have an asymmetrically elevated surface causing it to be blown around and around like an empty inflatable kayak.

The image below aligns the floe that had fractured into thirds in the animation above by the 22nd with the S1A scene of June 16th in which it was intact. The red line is the future fracture line. It looks offset on the left half but is not. In the upper right, the break does seem to follow a pre-existing weakness. Needs a click to see full size.
« Last Edit: June 24, 2016, 03:26:17 PM by A-Team »

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Re: Home brew AMSR2 extent & area calculation
« Reply #2130 on: June 24, 2016, 01:22:01 AM »
"It strikes me, we need to remember this isn't happening on a flat plane."
At 600N your about 1/2 way from the equator towards the axis of rotation, at 300N about 1/8, if you turn that round it indicates at 600N there's about 110 inclination to the pole, at 700N maybe 70, given the flattening towards the pole. So it's close to flat, that said as water moves north/south there's a lot of overturning moment since to all intents and purposes your approaching or retreating from the axis of rotation pretty much directly/ orthoganally.
One other thought is that if you watch for the tidal flows between Baffin and the arctic they move in sync, even in Amundsen gulf, so when a high tide is due in the north of Baffin current will increase either side of Banks island.

Rob Dekker

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Re: Home brew AMSR2 extent & area calculation
« Reply #2131 on: June 24, 2016, 07:36:21 AM »
A-team, thanks, what an amazing animation of the Beaufort, and that floe breaking up.

Incidentally, isn't that the floe that you have been tracking (and measured) since the start of May ?
http://forum.arctic-sea-ice.net/index.php/topic,1493.msg78429.html#msg78429

At that time (end of May), I commented that it would bottom-melt once it reached the Beaufort open water and then break up. And I suggested that we should take another look in a week.
Well, that is now 3 weeks ago  ;)

This is (was) quite certainly a MYI floe, and it is quite amazing how long it lasted.
But now that it broke I don't see anything magical about the exact fracture lines. Collisions causes odd shear forces, and either way, even toilet paper does not rip along the perforated lines  :D

It is unlikely that Coriolis forces had anything to do with the breakup. Just sustained bottom-melt and a bump from a neighboring floe.

But Coriolis forces almost certainly DO play a role in your animation :
If a floe drifts in a current, Coriolis forces will push it to the right. The ice that drifts in that Beaufort Gyre will thus want to compact, and that is why the whole pack is staying together and not flying all over the place.



Only at the boundary of the Beaufort Gyre, the Alaskan Coastal Current goes the other way.
That's when you get these weird Eddies that spin the ice floes out of the Gyre, and counterclockwise back to the CAA. And yes, some catapult effects are also apparent.

What most astounds me is how much ice the CAB is pushing into the Beaufort, while that sea still manages to melt out so much that its overall area and extent do not go up (while the section of the CAB where all this ice comes from is being torn to shreds).
« Last Edit: June 24, 2016, 07:41:45 AM by Rob Dekker »
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Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2132 on: June 24, 2016, 09:10:02 AM »
Extent and area dropped enough to stay ahead of 2012.

Update 20160623.

Extent: -88.2 (-582k vs 2015, -430k vs 2014, -1012k vs 2013, -172k vs 2012)
Area: -64.6 (-503k vs 2015, -315k vs 2014, -869k vs 2013, -320k vs 2012)
 
You will find the updated graphs in the top post

Hudson (-24k) and Kara (-22k) declined most in extent.
In area CAB recovers from the effects of the polar low (+38k). Laptev (-21k) and Greenland Sea (-20k) declined most.

The regional delta map is CAA. The bump in apparent sea ice concentration seems to be largely over.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2133 on: June 24, 2016, 09:18:39 AM »
The animation is from Laptev. As can be seen in the regional graphs, 2016 is not a fast melt year here. Here I compare it with 2015 the slowest thus far in my limited data set.

needs a click to start.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2134 on: June 24, 2016, 09:24:39 AM »
The surface melt extent did not change much today. After most of the effects of the arctic low have eased off, most of the surface in melting is on the Pacific half  of the Arctic Basin.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2135 on: June 24, 2016, 12:09:24 PM »
A-team, thanks, what an amazing animation of the Beaufort, and that floe breaking up.

It is unlikely that Coriolis forces had anything to do with the breakup. Just sustained bottom-melt and a bump from a neighboring floe.

But Coriolis forces almost certainly DO play a role in your animation :
If a floe drifts in a current, Coriolis forces will push it to the right. The ice that drifts in that Beaufort Gyre will thus want to compact, and that is why the whole pack is staying together and not flying all over the place.



Only at the boundary of the Beaufort Gyre, the Alaskan Coastal Current goes the other way.
That's when you get these weird Eddies that spin the ice floes out of the Gyre, and counterclockwise back to the CAA. And yes, some catapult effects are also apparent.
...


If this is so, an consequence that affects the ice is that the mixing of more saline water along the coast (except river output) and fresher from melting can be very fast since this so-called 2D-turbulence is very efficient in mixing in very long distances (it is called 2D because oceanographers assume stratification inhibits major vertical motion ... far enough from the coast which may be the case for the big floes, ... or approximately).
Whatever current forms these vortexes, it is displacing the floes at a much faster velocity than the (weakened) Gyre .


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Re: Home brew AMSR2 extent & area calculation
« Reply #2136 on: June 24, 2016, 04:10:35 PM »
Regarding the compactness graph by Wipneus, I wonder if a 5 or 10 days running average would help reading the graphs. At work, the running average method allows me to have a better view on electrical consumption graphs. By 5 days running average , I mean that for today, I take the average value of the last 5 days (today included). To analyse the electricity consumption, I even do running averages on 365 days in order to avoid seasonnal changes, but I can also do it on 1 or 2 hours if I want to see how electricity is used during the day.

Best regards,

Etienne

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Re: Home brew AMSR2 extent & area calculation
« Reply #2137 on: June 24, 2016, 04:28:50 PM »
Quote
Incidentally, isn't that the floe  breaking up that you have been tracking (and measured) since the start of May ?
That one, named Big Block, is still intact and unchanged. It is at the top center of the #2130 animation (western edge of Gyre) and has not experienced significant net transport since May 24th when it was spun out of the Gyre. The floe AndreasT follows has quite a different history even though it was once adjacent to and tracked with Big Block.

There might be some interest in an end of season retrospective if we had enough adopt-a-floes in terms of transport, melt and fragmentation histories. So far I am not seeing the slightest suggestion of melt or edge loss in Big Block. It is no longer under a S1A repeat swath.

While we do have a thickness transect from an airplane overflight, that won't be repeated either. It has not passed over any of the BGOS fixed mooring instrumentation (http://www.whoi.edu/page.do?pid=66566) as yet and probably won't. It's a massive floe that could conceivably last the season.

The two-day animation just shows a bit of rocker motion between today and yesterday. Floes are labelled on June 23rd; the inset provides locational context.

The 23rd also offers a clear shot of Mackenzie river discharge. The second frame shows the plume to be much more extensive than it appears on the WorldView 'true color'.

On the technical side, contrast was sacrificed on the floes in the second frame to optimally image the sediment. The floes could easily have been protected with a mask but here the interest was just in whether the plume extended out to the floe region (which is does, just barely). Sediment is an imperfect proxy for the influx and redistribution of relatively warm and buoyant fresh water from the river. However if sea surface salinity were available, it could help disentangle river from floe melt fresh water as well as coriolis doming.
« Last Edit: June 24, 2016, 04:56:11 PM by A-Team »

Rob Dekker

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Re: Home brew AMSR2 extent & area calculation
« Reply #2138 on: June 25, 2016, 07:56:54 AM »
Quote
Incidentally, isn't that the floe  breaking up that you have been tracking (and measured) since the start of May ?
That one, named Big Block, is still intact and unchanged. It is at the top center of the #2130 animation (western edge of Gyre) and has not experienced significant net transport since May 24th when it was spun out of the Gyre. The floe AndreasT follows has quite a different history even though it was once adjacent to and tracked with Big Block.

There might be some interest in an end of season retrospective if we had enough adopt-a-floes in terms of transport, melt and fragmentation histories. So far I am not seeing the slightest suggestion of melt or edge loss in Big Block. It is no longer under a S1A repeat swath.

"Big Block" indeed does not show any signs of melt yet. But remember that you can't "see" bottom melt. "Big Block"s time will come, but it will take time, and it will probably be the last one to go in the Beaufort, since it is the biggest block around (some 300 km across ?).

But the floe that just broke up, and that I referred to, you measured in May :
http://forum.arctic-sea-ice.net/index.php/topic,1493.msg78429.html#msg78429
and it's not "Big Block".

Quote
On the technical side, contrast was sacrificed on the floes in the second frame to optimally image the sediment. The floes could easily have been protected with a mask but here the interest was just in whether the plume extended out to the floe region (which is does, just barely). Sediment is an imperfect proxy for the influx and redistribution of relatively warm and buoyant fresh water from the river. However if sea surface salinity were available, it could help disentangle river from floe melt fresh water as well as coriolis doming.

Thanks A-team, that last picture compare (with contrast difference) shows, apart from the sediment out of the McKenzie, also shows clearly the streaks of "melting residue" of the MYI floes now drifting in the Beaufort.
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etienne

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Re: Home brew AMSR2 extent & area calculation
« Reply #2139 on: June 25, 2016, 09:10:46 AM »
About running average on 365 days (1 year) on area and extend.

Unfortunately, I didn't find data after 2011 and my open source software is not so flexible for graphs. Here is the place where I found the data :
ftp://ftp-projects.zmaw.de/seaice/AMSR-E_ASI_IceConc/area-extent/



First graph is the extend, the second one the area.

Best regards,

Etienne

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Re: Home brew AMSR2 extent & area calculation
« Reply #2140 on: June 25, 2016, 09:34:57 AM »
If this is so, an consequence that affects the ice is that the mixing of more saline water along the coast (except river output) and fresher from melting can be very fast since this so-called 2D-turbulence is very efficient in mixing in very long distances (it is called 2D because oceanographers assume stratification inhibits major vertical motion ... far enough from the coast which may be the case for the big floes, ... or approximately).

I agree. Just that I'm not sure if that (salinity pumping) makes any difference. After all, these vortices are very close (if not over) the continental shelf, where the water is real shallow.

Quote
Whatever current forms these vortexes, it is displacing the floes at a much faster velocity than the (weakened) Gyre .

Yes. Remember that Coriolis forces always push the floes to the right, which is AWAY from the center for these counterclockwise vortices that we see in the Beaufort.

I'm just surprised how much of the ice that gets pushed into the Beaufort melts out, and I wonder how long the CAB can provide ice before it shatters so much that holes will start to open in the CAB.
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Re: Home brew AMSR2 extent & area calculation
« Reply #2141 on: June 25, 2016, 10:31:38 AM »
etienne, in your link
ftp://ftp-projects.zmaw.de/seaice/AMSR-E_ASI_IceConc/area-extent/
which specific files are you referring to for "area" and "extent" ?

[edit] Never mind.
I found this file :
ftp://ftp-projects.zmaw.de/seaice/AMSR-E_ASI_IceConc/area-extent/area_ASI-AMSR-E_v5.6i_Arc.txt
which shows "area" from 2002 - 2011.
and this one
ftp://ftp-projects.zmaw.de/seaice/AMSR-E_ASI_IceConc/area-extent/extent_ASI-AMSR-E_v5.6i_Arc.txt
which shows "extent" from 2002 - 2011.

Which is nice, but does this source have any data before of after these dates ?
« Last Edit: June 25, 2016, 10:45:37 AM by Rob Dekker »
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Re: Home brew AMSR2 extent & area calculation
« Reply #2142 on: June 25, 2016, 11:50:05 AM »
Quote
Incidentally, isn't that the floe  breaking up that you have been tracking (and measured) since the start of May ?
That one, named Big Block, is still intact and unchanged. It is at the top center of the #2130 animation (western edge of Gyre) and has not experienced significant net transport since May 24th when it was spun out of the Gyre. The floe AndreasT follows has quite a different history even though it was once adjacent to and tracked with Big Block.

There might be some interest in an end of season retrospective if we had enough adopt-a-floes in terms of transport, melt and fragmentation histories. So far I am not seeing the slightest suggestion of melt or edge loss in Big Block. It is no longer under a S1A repeat swath.

While we do have a thickness transect from an airplane overflight, that won't be repeated either. It has not passed over any of the BGOS fixed mooring instrumentation (http://www.whoi.edu/page.do?pid=66566) as yet and probably won't. It's a massive floe that could conceivably last the season.

The two-day animation just shows a bit of rocker motion between today and yesterday. Floes are labelled on June 23rd; the inset provides locational context.

...

As flattering as it is to have an ice floe with my name on it, this is the wrong floe and the one I tracked and wrote about here http://forum.arctic-sea-ice.net/index.php/topic,382.msg79235.html#msg79235 most recently has fragmented into too many pieces to track them all.
It is nevertheless instructive to take the bother to look for them and one has not changed much since the original floe broke up on the 27. of May.
http://forum.arctic-sea-ice.net/index.php/topic,1493.msg78438.html#msg78438
I am showing 721bands this time because it tells more about the nature of the ice of which the floes are composed.

Andreas T

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Re: Home brew AMSR2 extent & area calculation
« Reply #2143 on: June 25, 2016, 11:51:56 AM »
split post for more images...
dates are in the file name
http://go.nasa.gov/28Wr7Jq

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Re: Home brew AMSR2 extent & area calculation
« Reply #2144 on: June 25, 2016, 12:50:54 PM »
these images http://forum.arctic-sea-ice.net/index.php/topic,382.msg81296.html#msg81296 show several features:

floe fragments can be very persistent (over a month at the edge of the pack in the case of fragment II )

floes are in many cases composed of younger and older ice, I think the different shades of blue show differences in meltponding for FYI and MYI. Snow cover will also be different for ice which was around when snow started to fall at the beginning of Sept.

The different movement of initially close floe fragments is impressive. Between the 20th and 24th fragment II completed a full circle around the large piece of fragment III just to end up in nearly the same place!

It is tempting to invoke the magic word "coriolis" whenever movement is odd and hard to understand and I don't think I can explain the flow dynamics of this corner of the arctic ocean in a forum comment, but I don't want to give the impression of tacit agreement with some of the things which have been written in this thread.
When ice is moved south (for example) by a water current the water current is equally subject to "the coriolis effect" so a different explanation is required why there is differential movement between water and ice (if present)
The coriolis force is an apparent force and will not rip ice floes apart. Forces take effect when there is differential movement between water and ice or water and seafloor/coastline.

It is significant that the area where eddies are strongest (shear forces from an eddy pulled fragment I apart I believe) are where the shelf blocks the deep water momentum moving west from carrying the surface away from the Canadian Archipelago. Because of the precipitation input into the arctic ocean, the "natural"  direction of flow is draining through the Northwest passage towards the west (and south after that)
« Last Edit: June 25, 2016, 02:04:10 PM by Andreas T »

etienne

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Re: Home brew AMSR2 extent & area calculation
« Reply #2145 on: June 25, 2016, 01:42:40 PM »
Which is nice, but does this source have any data before of after these dates ?

I have no idea, it was the first data I found. If I find something better, I'll do a new graph.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2146 on: June 25, 2016, 01:53:47 PM »
Which is nice, but does this source have any data before of after these dates ?

Not from AMSR-E it doesn't:

https://nsidc.org/data/amsre

Quote
The AMSR-E instrument launched on 02 May 2002 and ceased operations 04 December 2011. Temporal coverage for the data products is from 18 June 2002 through 04 October 2011.

As the topic title suggests, Wipneus provides area and extent data from the subsequent AMSR2 instrument. What are you and/or Etienne endeavouring to achieve?
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Re: Home brew AMSR2 extent & area calculation
« Reply #2147 on: June 25, 2016, 03:16:15 PM »
Update 20160624.

Extent: -65.5 (-562k vs 2015, -414k vs 2014, -934k vs 2013, -165k vs 2012)
Area: -82.4 (-441k vs 2015, -320k vs 2014, -839k vs 2013, -273k vs 2012)
 
You will find the updated graphs in the top post

Regional extent has no region really standing out. CAA (-21k) and Beaufort (-14k) declined most.
For regional area CAA showed a big decrease (-38k) and the CAB an increase of +20k.
Beaufort, Chukchi and Hudson declined about -17k.

The regional delta map if of the Beaufort. I wonder if you can recognize "BigBlock" and other discussed ice floes?


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Re: Home brew AMSR2 extent & area calculation
« Reply #2148 on: June 25, 2016, 03:20:32 PM »
The animation is of the Greenland Sea. Now even the pack ice in the north is going, leaving just a lot of fast ice which is also under attack.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2149 on: June 25, 2016, 03:36:29 PM »
And the surface melting situation. Only slight changes with most of the pacific half of the arctic in melting.