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seaicesailor

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Re: The 2016 melting season
« Reply #850 on: May 04, 2016, 07:52:33 PM »
seaicesailor, you should not call these images "IR" they are thermal radiation but in the microwave part of the spectrum. Intensities are lower which reduces the resolution of these images below those of IR images and the emissivity of water and ice is different at these wavelengths, which makes them used for determining the AMSR-2 ice concentration maps.

Thanks for the correction Andreas

6roucho

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Re: The 2016 melting season
« Reply #851 on: May 04, 2016, 08:01:21 PM »
Okay.. from a quick look at EOSDIS. I warn you I am an amateur on ice and satellite images.

I was looking at the images of the Beaufort and noticed that there are big curved cracks extending towards Wrangle Island from the Anzhu islands that propagated roughly 1000km across the East Siberian sea towards Alaska from around the 29th April to today. The direction of separation is along the coast of Russian. Basically East to West (examining the cracks in detail give a good indication of the movement). It implies that these were opened by clockwise rotation.  There are chunks of ice in the cracks that are being rotated. There is one below, that was rotated through 10-15km by the motion on 2nd may, and moved about 15km in the last 24 hours, or around 17cm/s.

I'm a new observer.. Is my interpretation reasonable and would this support detachment seen above?

Yes that is a crack that appeared in mid April and relieved the ice in that huge area in its tendency to rotate following the Gyre (although the displacement speed was much slower than that at Beaufort, as apparent from the drift maps too).

It was very clear from IR images, I will see if I can find any, on the mobile now. Bust rest assured there is no such a thing as "ice detachment" in the way implied in some comments here. Even if the whole Arctic rotates unison. It is not like a giant let loose from its chains. At any location, ice inertia is balanced by ocean dragging at the bottom, wind pulling at the top, pressure and shear forces at sides , and other forces. Gravity balanced too. It is not going to "fly away". ;-)

I doubt anyone on here thinks that! The prospect of a wider polar gyre has been discussed in detail before. It's that even the limited interpretation is alarming in context.

A-Team

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Re: The 2016 melting season
« Reply #852 on: May 04, 2016, 09:21:40 PM »
Quite about IR vs microwave and a nice explanation why this matters.
Quote
1000hPa winds because they show force driving the ice more clearly (I think).
As explained earlier, here you want nullschool's 1000hPa 'instantaneous wind power density' WPD map, wind3 is what moves the floes of ice (freeboard ~turbine blade), not gentle zephyrs of wind1. They are both derived primarily from air pressure reanalysis/forecast, not measured in situ to any extent.
 
I've noticed no one has been posting time series of nullschool, presumably because it's a total  nuisance layering up screenshots: the slightest mouse movement throws off the nullschool alignment (it has browser page-back but it could be several).

We would further like the nullschool images to be at at the same map scale, projection, and land mass orientation as the WorldView satellite time series, the scalable but non-rotating EPSG 3143, NSIDC's polar stereographic Greenland-down 70º main parallel.

There are two easy ways to script out an animated nullschool overlay of WorldView at maximal forum-compatible size of 700x700.

The first trick is to carefully precondition the view in nullschool's AE projection (azimuthal equidistant). This projection defaults exactly to a north pole-centered -45º rotation relative to rigid WorldView which surprisingly aligns indistinguishably to EPSG 3143 on the scale of the Arctic Ocean.

Mousing over the screen (never clicking) enlarges the scale without introducing a rotation, best done on a blank advanced date that has 'no data'. Note the url actually changes in real time as you mouse which can be co-calibrated with WorldView to match scales.

The second trick is to put the mouse down and use keyboard commands instead (below) to cycle through the date range build layers in Gimp (respectively stacks in ImageJ) via whole-window screenshots (command option shift 4 space on a Mac), switching apps back and forth (with command tab/tilde).

Although it takes only ~3-4 minutes for a 10-day time series, including the chained rotation, cropping, a round or two of contrast enhancement, pause-building, frame rate testing and uploading to forum, it pays to turn on keystroke recording to add other nullschool views like temperature.

One frame of nullschool tracers suffices to disambiguate wind direction; there's a keyboard command to turn them off. As noted, the palette has a linear decomposition to grayscale as the L layer of L.a.b color space. This allows replacement of the original ugly palette by arbitrary contoured indexed color which in turn enables quantitation or GIS layer arithmetic interaction.

The second approach starts with an easy tear-down of the starting date's dynamic url into a flat file database of its building blocks. No scripting: build additional dates and incremental views with 'fill-down' spreadsheet commands (kept as template), the new urls are layered with 'Open Location' in Gimp.

Repeating with the same dates in Worldview, the two animations can be butted side-by-side with 'filmstrip' and 'guide-cropping'. In the case of wind WPD, the suspected dominant contributor to daily variation in floe displacement, it makes sense to stagger the times, ie to anticipate WorldView dated movement. The former are furnished at 3 hour intervals (8x per day); the latter are wedge-shaped tiles from different orbital passes.

I will be offline traveling for the next few weeks and will post some examples later
« Last Edit: May 05, 2016, 03:28:42 AM by A-Team »

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Re: The 2016 melting season
« Reply #853 on: May 04, 2016, 11:32:15 PM »

I have often wondered if the regular decline in arctic DMI temperatures that occurs between April 15 and May 15th each of the past 4 years (and right around that time) through 2009!  is in some way all or partially attributable to the shift in U.S. gasoline refineries production of summer blend gasoline that occurs in late march.

just a thought, another would be a shift in polar cell behavior as the mid-latitudes warms up and the increased solar melt-transpiration of snow leading to increased water vapor content in early spring. . .
I think the answer to this is a very prosaic issue, weather. Summer temperatures tend to  be fairly stable but from sept -> may temperatures in the north typically jump around quite a bit. Winter temperatures are now typically 3-4 degrees warmer than the average so they appear 'warm' even in cold spells. However by April / May  temperatues are rising rapidly and a decline for a week or so plunges the temperatures below average.
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Re: The 2016 melting season
« Reply #854 on: May 04, 2016, 11:57:07 PM »
Keep in mind that with the previous detachment events north of CAA over the past couple of years, the thickest and oldest ice is no longer adjacent to the islands. The bulk of the ice adjacent to the shores are thinner and no older than 2nd year ice.

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Re: The 2016 melting season
« Reply #855 on: May 05, 2016, 03:42:07 AM »
Amazing

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Re: The 2016 melting season
« Reply #856 on: May 05, 2016, 04:44:58 AM »
Dramatic

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Re: The 2016 melting season
« Reply #857 on: May 05, 2016, 05:31:18 AM »
Have I misunderstood today's EOSDIS image?  Are there cracks in the ice from Svalbard almost across the pole to this new crack show in Jai Mitchell's post above?  See attached.  Or are those dark lines something else?


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Re: The 2016 melting season
« Reply #858 on: May 05, 2016, 05:41:16 AM »
Sorry - should have included lat/long lines...

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Re: The 2016 melting season
« Reply #859 on: May 05, 2016, 06:13:41 AM »
 very bad, gif attached/click to animate (may 3 vs 4)

should add that first glimpse of images from 5/5 show the crack now splitting/expanding and almost meeting the ones originating from the Russian/ATL sides, imagery later today should be pretty crazy

& if models are right, the western CAB is going to shatter further this week, with area decrease steepening across Beaufort in a very dramatic way
« Last Edit: May 05, 2016, 06:18:54 AM by bbr2314 »

bbr2314

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Re: The 2016 melting season
« Reply #860 on: May 05, 2016, 07:22:01 AM »
The models are now showing catastrophic potential through D10 for the sea ice. The blowtorch begins around 120 hours on the GFS.



The blowtorch ends up covering over half the Arctic Ocean by D10. Insane.





This is truly insane.

If there's any year that could be a black swan from several angles, it seems like 2016 could be it. The fracturing we have already seen and the decline in snowcover over Alaska (combined with a very minimal Pacific pack) look to allow an unprecedented belch of heat (for this time of the yr) access to what may well be the entire Arctic Ocean when all is said and done.

While this will be bad for the thick pack on the Russian side it will be truly devastating to what's left in the Beaufort & the other areas on the Pac side that already have open water. I would think area numbers will begin to plummet at this point -- and worse, the open water means a repeat of the GAC from 2012 becomes more likely, especially as it absorbs all the springtime radiation sea ice would normally reflect.

This is quite possibly our black swan/blue Arctic year.

Andreas T

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Re: The 2016 melting season
« Reply #861 on: May 05, 2016, 09:16:16 AM »
Have I misunderstood today's EOSDIS image?  Are there cracks in the ice from Svalbard almost across the pole to this new crack show in Jai Mitchell's post above?  See attached.  Or are those dark lines something else?
cracks can be seen in this microwave image from the 5th of April. the difference is that temperatures are now higher over the whole arctic and cracks which open freeze over more slowly so they now show up in the visible wavelengths.

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Re: The 2016 melting season
« Reply #862 on: May 05, 2016, 09:53:56 AM »
Snow cover anomalies HAVE plummeted.





April was the lowest April on record.

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Re: The 2016 melting season
« Reply #863 on: May 05, 2016, 10:19:21 AM »

I have often wondered if the regular decline in arctic DMI temperatures that occurs between April 15 and May 15th each of the past 4 years (and right around that time) through 2009!  is in some way all or partially attributable to the shift in U.S. gasoline refineries production of summer blend gasoline that occurs in late march.

just a thought, another would be a shift in polar cell behavior as the mid-latitudes warms up and the increased solar melt-transpiration of snow leading to increased water vapor content in early spring. . .
I think the answer to this is a very prosaic issue, weather. Summer temperatures tend to  be fairly stable but from sept -> may temperatures in the north typically jump around quite a bit. Winter temperatures are now typically 3-4 degrees warmer than the average so they appear 'warm' even in cold spells. However by April / May  temperatues are rising rapidly and a decline for a week or so plunges the temperatures below average.
Possible, but not very likely. There is "normal" or even a bit "delayed" temperature increase trend lately, instead of expected "things should get warmer sooner" for spring time, out of general Arctic amplification. If it'd be a single year, sure thing, "it's weather" would be most appealing. Or even two or three years. But when it's a trend, "it's weather" stops to be an explanation, me thinks...

DoomInTheUK

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Re: The 2016 melting season
« Reply #864 on: May 05, 2016, 10:33:08 AM »
The only consistent input that I can think of that could give a trend around the same time of year is insolation. Weather may affect the result by a week or two either way, but the sun starts to make it's way back over the horizon in a very predictable fashion. As to why that may hold or drop the temperatures I can only guess.
If the plateau seems to be around the same temperature maybe it's a phase change in the ice that needs a little extra energy to get it over the hump.


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Re: The 2016 melting season
« Reply #865 on: May 05, 2016, 10:36:42 AM »
Dramatic


do not get too excited Neil those dramatic wiggles are down to a satellite problem not real ice changes.

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Re: The 2016 melting season
« Reply #866 on: May 05, 2016, 10:44:36 AM »
There is an awful lot of ice missing from this year's map compared to 2012 don't you think?

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Re: The 2016 melting season
« Reply #867 on: May 05, 2016, 11:44:49 AM »
Dramatic


do not get too excited Neil those dramatic wiggles are down to a satellite problem not real ice changes.
I bet he sees the same thing i do: area going WAY below lowest-ever. Wiggles above the trend are at select dates and IMHO can safely be ignored as long as the "bottom" part of the graph still have enough days in it to allow to see what's going on.

YMMV, though.

P.S. Or one can put it in another way about this data Neil presented: 2016 day 123 has nearly same ice area (~11,13M km2) as
 - 2006 day 129 (previously being the fastest-ever year to get to ~11,13M km2, and now its "record" is smashed in 2016 by SIX days at once),
 - 2015 day 131,
 - 2012 day 136,
 - 2007 day 136,
 - 1986 day 151 (almost full MONTH later than 2016, you know...)
« Last Edit: May 05, 2016, 11:55:03 AM by F.Tnioli »

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Re: The 2016 melting season
« Reply #868 on: May 05, 2016, 11:50:27 AM »
Yep, lot of ice missing.

For the CAA, things will accelerate in the days to come, the supposedly very thick ice will break apart easily (let's see). From April 4th to May 4th.

magnamentis

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Re: The 2016 melting season
« Reply #869 on: May 05, 2016, 01:04:37 PM »

I have often wondered if the regular decline in arctic DMI temperatures that occurs between April 15 and May 15th each of the past 4 years (and right around that time) through 2009!  is in some way all or partially attributable to the shift in U.S. gasoline refineries production of summer blend gasoline that occurs in late march.

just a thought, another would be a shift in polar cell behavior as the mid-latitudes warms up and the increased solar melt-transpiration of snow leading to increased water vapor content in early spring. . .
I think the answer to this is a very prosaic issue, weather. Summer temperatures tend to  be fairly stable but from sept -> may temperatures in the north typically jump around quite a bit. Winter temperatures are now typically 3-4 degrees warmer than the average so they appear 'warm' even in cold spells. However by April / May  temperatues are rising rapidly and a decline for a week or so plunges the temperatures below average.
Possible, but not very likely. There is "normal" or even a bit "delayed" temperature increase trend lately, instead of expected "things should get warmer sooner" for spring time, out of general Arctic amplification. If it'd be a single year, sure thing, "it's weather" would be most appealing. Or even two or three years. But when it's a trend, "it's weather" stops to be an explanation, me thinks...

while exactly this year will brake the trend in the way that we are already beyond or at the point where temps would have to start retreating towards crossing the line which IMO is not in close sight. chances are high that we won't have a year without a single drop below normal but:

a) chance is indeed there

b) as it seems the curve will not follow the pattern you mention which makes sense considering the accelerated warming over the last 10 years, sooner or later the acceleration will out perform the 30-40 year averages IMO

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Re: The 2016 melting season
« Reply #870 on: May 05, 2016, 01:09:18 PM »
F.Tnioli, yes that's exactly what I was saying.

It's right off the bottom.  I know the wiggles are issues with the sensors, but the overall is down, down, down.

Still, I'm waiting for it to stall....
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Re: The 2016 melting season
« Reply #871 on: May 05, 2016, 01:28:08 PM »
Upward spikes are clearly wrong - can see spurious ice where there isn't any. But should we trust the low values? They don't look ridiculously wrong and comparing

IJIS 240k below previous lowest.
CT 348k below previous lowest.
Certainly not inconsistent.

but I really don't know and some caution before blindly believing latest CT really low values seems advisable?

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Re: The 2016 melting season
« Reply #872 on: May 05, 2016, 02:13:45 PM »
Upward spikes are clearly wrong - can see spurious ice where there isn't any. But should we trust the low values? They don't look ridiculously wrong and comparing

IJIS 240k below previous lowest.
CT 348k below previous lowest.
Certainly not inconsistent.

but I really don't know and some caution before blindly believing latest CT really low values seems advisable?

I agree with all that. BUT on the other side, the Antarctic, F17 measurements show they can be off in both directions. Perhaps that is because the orientation of the spacecraft to the sun is different there, so in the Arctic we don't have that problem. I would not bet on it. 

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Re: The 2016 melting season
« Reply #873 on: May 05, 2016, 02:38:08 PM »
but I really don't know and some caution before blindly believing latest CT really low values seems advisable?

if it were not for what we are seeing on the Bremen AMSR2, which uses a different sensor does it not? Then I would probably feel the same.
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Re: The 2016 melting season
« Reply #874 on: May 05, 2016, 03:05:18 PM »
The only consistent input that I can think of that could give a trend around the same time of year is insolation. Weather may affect the result by a week or two either way, but the sun starts to make it's way back over the horizon in a very predictable fashion. As to why that may hold or drop the temperatures I can only guess.
If the plateau seems to be around the same temperature maybe it's a phase change in the ice that needs a little extra energy to get it over the hump.
Insolation provides the base line, but doesn't explain the variation. We are not seeing greater melt this year, than 10 years ago,  because of insolation.  The issue when viewing  the massive melt this year is not going to  be explained by insolation.  If insolation was the key  factor in variation then we wouldn't be here discussing the dramatic ice loss over the past 15 years.
The key  factor is the warmth in the Arctic that  prevents ice growth in winter and promotes melt in summer.  the Arctic is warming  because the planet  is warming but the Arctic is warming a whole lot  faster than the rest of the world.
« Last Edit: May 05, 2016, 11:04:15 PM by DavidR »
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Re: The 2016 melting season
« Reply #875 on: May 05, 2016, 03:17:29 PM »
DavidR  - the issue wasn't about the melting per se, but why there's a fairly consistent drop in average temperatures around March/April. Even this year with it's stupidly high temperatures managed it.

It's probably just one of those issues where humans are very good at spotting patterns even when there probably isn't one there. It does look a bit odd though.

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Re: The 2016 melting season
« Reply #876 on: May 05, 2016, 03:45:19 PM »
Dramatic


do not get too excited Neil those dramatic wiggles are down to a satellite problem not real ice changes.
I bet he sees the same thing i do: area going WAY below lowest-ever. Wiggles above the trend are at select dates and IMHO can safely be ignored as long as the "bottom" part of the graph still have enough days in it to allow to see what's going on.

YMMV, though.

P.S. Or one can put it in another way about this data Neil presented: 2016 day 123 has nearly same ice area (~11,13M km2) as
 - 2006 day 129 (previously being the fastest-ever year to get to ~11,13M km2, and now its "record" is smashed in 2016 by SIX days at once),
 - 2015 day 131,
 - 2012 day 136,
 - 2007 day 136,
 - 1986 day 151 (almost full MONTH later than 2016, you know...)
It makes no sense to accept one measurement and not others. the sensor is obviously not working correctly all measurements are suspect at this time as can be seen by the antarctic chart which varies in both directions. http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html   

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Re: The 2016 melting season
« Reply #877 on: May 05, 2016, 06:38:03 PM »
Dramatic


do not get too excited Neil those dramatic wiggles are down to a satellite problem not real ice changes.
I bet he sees the same thing i do: area going WAY below lowest-ever. Wiggles above the trend are at select dates and IMHO can safely be ignored as long as the "bottom" part of the graph still have enough days in it to allow to see what's going on.

YMMV, though.

P.S. Or one can put it in another way about this data Neil presented: 2016 day 123 has nearly same ice area (~11,13M km2) as
 - 2006 day 129 (previously being the fastest-ever year to get to ~11,13M km2, and now its "record" is smashed in 2016 by SIX days at once),
 - 2015 day 131,
 - 2012 day 136,
 - 2007 day 136,
 - 1986 day 151 (almost full MONTH later than 2016, you know...)
It makes no sense to accept one measurement and not others. the sensor is obviously not working correctly all measurements are suspect at this time as can be seen by the antarctic chart which varies in both directions. http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html
We know that NSIDC's SSMIS data from F-17 contains only spuriously high (not low) readings by comparing it to JAXA's AMSR2 from Shizuki.

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Re: The 2016 melting season
« Reply #878 on: May 05, 2016, 07:32:48 PM »
Snow cover anomalies HAVE plummeted.

April was the lowest April on record.

It looks that it will be getting worse.  Cycling through CCI images, over the next few days the whole western Arctic is going to get hammered, hard.  Well above freezing across the Bering, Chukchi, Beaufort and western end of the CAA, spreading into the CAB proper.

It looks like the Siberian side gets a slight respite, but heat does look to be spilling into the Okhotsk as well. 

That said, I think by the end of next week there will be very little snow cover left on the North American side and a lot of the snow cover on the pack will get butchered as well.
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Re: The 2016 melting season
« Reply #879 on: May 05, 2016, 09:07:10 PM »
The low Cryosphere Today area looks correct to me.

I calculated the area from AMSR2 concentration data with 15% cut off (I think that's what CT uses, but it doesn't make a big difference anyway)

More significant are the errors around the coast. Even Iceland, Britain or South Alaska have some ice because I didn't apply a mask and lake Michigan appears to be covered by 50% ice according to the data.
See attached image for concentration data.

04 May 2016
AMSR: 11,343,964
CT: 11,136,060 (actually data for 03 May because its behind)

difference: 207,904

I had a concentration data file from the 05 March still on my pc and this had a similar difference.

05 March 2016
AMSR: 12,914,932
CT: 12,746,350

difference: 168,582

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Re: The 2016 melting season
« Reply #880 on: May 05, 2016, 10:26:38 PM »
The. 12z euro flattens the beaufort, Chuchki, and Western CAB.

Both the euro and gfs have ridging, sunny skies and 50s-60s reaching the Mackenzie Delta and 50s+ all along the arctic shoreline in the area.
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Re: The 2016 melting season
« Reply #881 on: May 05, 2016, 11:32:56 PM »
The. 12z euro flattens the beaufort, Chuchki, and Western CAB.

Both the euro and gfs have ridging, sunny skies and 50s-60s reaching the Mackenzie Delta and 50s+ all along the arctic shoreline in the area.

Yep -- both are showing a widespread surface melt event starting around 00Z on the 10th as ridging aloft builds in over AK and into the Beaufort. The ridge then strengthens into a large block and greatly expands the melt region through the end of the run, encompassing all of the Beaufort, most of the Chukchi and even partially into the CAB. Ensembles and the weekly CFSv2 have been hinting at this for a while as well.

As bad as that is, the CFSv2 has become increasingly bullish on ridging persisting through the end of the month, with any relief being a temporary affair. Looks like a rocket start to the melt season. 

DMI 80N temps are likely to fall to normal or slightly below right around the 10th before likely rocketing back above normal by the 15th as ridging expands.

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Re: The 2016 melting season
« Reply #882 on: May 05, 2016, 11:43:02 PM »
Although the last mini-heatwave in the Beaufort didn't verify, this next predicted one is getting into the within one week = usually quite accurate range

magnamentis

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Re: The 2016 melting season
« Reply #883 on: May 06, 2016, 01:58:17 AM »
for all those of you who miss the interactive sea-ice-extent charts from NSIDC, here is a worthy replacement IMHO: https://ads.nipr.ac.jp/vishop/vishop-extent.html

in a way it's even better, more feature rich. just click all the buttons, there are a few nice surprised hidden behind nondescript buttons :-) ;)

werther

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Re: The 2016 melting season
« Reply #884 on: May 06, 2016, 08:52:41 AM »
Yesterday further break-up was visible in the Kara Sea. This is an enhanced view of the Sea in it’s NE part, near Vilkitsky Strait.



Condition of the sea ice is worse than ever for this time of the year. Not surprising after a winter producing mean temp anomalies +4 - +9 dC.

This continued during April: +2 - +7 dC:



Mean temps were just under freezing in the Southern part of the Sea.
Under these conditions, currents and tides are strong enough to keep ice in Vilkitsky Strait mobile. Last week, Northeastern winds crept in. Although those winds contributed to hold temps in the NE part under -8 dC, they tore up part of the small swath of fast-ice against Severnaya Zemlya.

All in all, it looks like Vilkitsky Strait will be ice-free on a very early date.

« Last Edit: May 06, 2016, 09:22:10 PM by werther »

abbottisgone

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Re: The 2016 melting season
« Reply #885 on: May 06, 2016, 08:59:55 AM »
The only consistent input that I can think of that could give a trend around the same time of year is insolation. Weather may affect the result by a week or two either way, but the sun starts to make it's way back over the horizon in a very predictable fashion. As to why that may hold or drop the temperatures I can only guess.
If the plateau seems to be around the same temperature maybe it's a phase change in the ice that needs a little extra energy to get it over the hump.
Insolation provides the base line, but doesn't explain the variation. We are not seeing greater melt this year, than 10 years ago,  because of insolation.  The issue when viewing  the massive melt this year is not going to  be explained by insolation.  If insolation was the key  factor in variation then we wouldn't be here discussing the dramatic ice loss over the past 15 years.
The key  factor is the warmth in the Arctic that  prevents ice growth in winter and promotes melt in summer.  the Arctic is warming  because the planet  is warming but the Arctic is warming a whole lot  faster than the rest of the world.
You talk about the last 15 years: what is the clearest way of seeing this dramatic loss?
..
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Neven

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Re: The 2016 melting season
« Reply #886 on: May 06, 2016, 11:09:45 AM »
The. 12z euro flattens the beaufort, Chuchki, and Western CAB.

Both the euro and gfs have ridging, sunny skies and 50s-60s reaching the Mackenzie Delta and 50s+ all along the arctic shoreline in the area.
I'm discussing all things Beaufort in this latest blog post: Beaufort under relentless (high) pressure

Here's how that wave of above freezing temps looks like:



And here's the weekly changes in NH snow cover in the past month:

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andy_t_roo

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Re: The 2016 melting season
« Reply #887 on: May 06, 2016, 11:13:37 AM »
...
You talk about the last 15 years: what is the clearest way of seeing this dramatic loss?
to put things into perspective, volume wise :


DavidR

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Re: The 2016 melting season
« Reply #888 on: May 06, 2016, 11:14:04 AM »
You talk about the last 15 years: what is the clearest way of seeing this dramatic loss?

The IJIS data is here:
https://ads.nipr.ac.jp/vishop/data/graph/plot_extent_n_v2.csv

Determine the minimum for each year and plot the decline. All very easy using Excel.
The trend line is 120,000 Sq Km per year or about 2.4% per year on the original minimums of about 5.7 M Km^2 thats about  31% from 2002 to 2015
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crandles

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Re: The 2016 melting season
« Reply #889 on: May 06, 2016, 11:19:53 AM »
You talk about the last 15 years: what is the clearest way of seeing this dramatic loss?

Maybe PIOMAS data?



Perhaps gompertz fits would fit the data better than those exponential curves. Exponential looks too alarmist, but recent bump of last 3 years could well distort gompertz into falsely looking like there is no expected further loss. So maybe neither exponential or gompertz works well and perhaps just straight line fits would be better?

dnem

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Re: The 2016 melting season
« Reply #890 on: May 06, 2016, 01:32:35 PM »
I'm just a poor biologist, so what the heck do I know, but I can't see how picking one statistical model or another to fit these data makes much sense at all.  First, the PIOMAS data are model to begin with.  Then we are trying to fit a statistical model to the trend of a complex three-dimensional process (volume loss) being influenced by a complex and chaotic process (inter-annual weather) and a poorly understood, complex and continually changing press perturbation (climate).  That seems like a very tall order to me.

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Re: The 2016 melting season
« Reply #891 on: May 06, 2016, 01:49:42 PM »
I'm just a poor biologist, so what the heck do I know, but I can't see how picking one statistical model or another to fit these data makes much sense at all.  First, the PIOMAS data are model to begin with.  Then we are trying to fit a statistical model to the trend of a complex three-dimensional process (volume loss) being influenced by a complex and chaotic process (inter-annual weather) and a poorly understood, complex and continually changing press perturbation (climate).  That seems like a very tall order to me.
That's certainly true for model predictions of future changes in the ice. All of the models lack crucial variables that we can't measure for many reasons. We may not have a complete model of sea ice decline until long after it has gone.

On the other hand, we can still extrapolate trends using data such as the total volume of ice, despite having only an incomplete knowledge of its physics, in the same way that an actuary can estimate your likely age of death, within measurable margins of error, despite knowing nothing about the biological process of aging.
« Last Edit: May 06, 2016, 02:05:26 PM by 6roucho »

crandles

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Re: The 2016 melting season
« Reply #892 on: May 06, 2016, 03:03:20 PM »
maybe piecewise-linear would be better? (if it can confirm any rate changes are significant)
 
https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/

Extrapolation of curves can be rather dodgy as demonstrated by the difference between exponential fit to data up to 2012 hitting 0 in 2015 compared with now you might think it looks more gompertz shaped and that never hits zero.

The task was to clearly show the dramatic loss. For that we want to show what has happened not what we think will happen. Piecewise-linear is perhaps useful if there are changes in rate that are significant and if not some sort of smoothing might be better for this particular purpose.

The graph I picked seemed to show the PIOMAS data nicely but the exponential trends didn't seem ideal for the purpose so I added a few comments but perhaps I went into detail (distracted by old discussions of exponential vs gompertz) that wasn't particularly relevant to staying focussed on the particular task.

Yes picking one statistical model or another to fit these data doesn't makes much sense if the task is show what has happened. A suitable trend may usefully communicate information by drawing the eye to important changes. It is possible the exponential trend used may be worse than nothing tending to hide the acceleration in rate followed by a slowdown in rate.

With an alternative task of considering extrapolation then saying it doesn't make much sense to pick one statistical model or another would be like saying we should give up on the aim of extrapolating. Yes things are complex and a simple extrapolation isn't going to have tiny errors, but I don't think it is so complex that there is nothing else than give up.

In this extrapolating purpose case, if different statistical models could make a great deal of difference to the extrapolation, then it would be an important point to make.

dnem

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Re: The 2016 melting season
« Reply #893 on: May 06, 2016, 03:35:48 PM »
Again, I'm a total amateur here, but if your purpose is to try and predict where volume (or extent or area for that matter) is heading over the next decade say, I still think fitting any model to the data to date is a fool's errand. Yes, 6roucho, actuarial data are useful in modeling what will happen to a large and well-described population, but for a single individual within that population, not so much.  There is only one arctic and we are watching it go through changes that are utterly unprecedented during the instrumental record.  If you add to that the fairly well accepted belief that the variability exhibited by complex systems tends to increase as it approaches a state change, I'm pretty close to throwing up my hands and leaving it at: "there is no evidence suggesting that the arctic is not collapsing toward a seasonally ice free state and that is likely to happen within... (pick a number of years)." Sure, playing with curve fitting can help a bit in picking that number, but only so much.  The weather is going to control the end game and no curve fitting is going to predict that.

6roucho

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Re: The 2016 melting season
« Reply #894 on: May 06, 2016, 04:11:16 PM »
Again, I'm a total amateur here, but if your purpose is to try and predict where volume (or extent or area for that matter) is heading over the next decade say, I still think fitting any model to the data to date is a fool's errand. Yes, 6roucho, actuarial data are useful in modeling what will happen to a large and well-described population, but for a single individual within that population, not so much.  There is only one arctic and we are watching it go through changes that are utterly unprecedented during the instrumental record.  If you add to that the fairly well accepted belief that the variability exhibited by complex systems tends to increase as it approaches a state change, I'm pretty close to throwing up my hands and leaving it at: "there is no evidence suggesting that the arctic is not collapsing toward a seasonally ice free state and that is likely to happen within... (pick a number of years)." Sure, playing with curve fitting can help a bit in picking that number, but only so much.  The weather is going to control the end game and no curve fitting is going to predict that.
On that point I certainly do agree with you dnem. The models will all 'break' as the system enters a state change. And that state change could produce unexpected outcomes, per Hansen et al. Maybe we're going there now.

F.Tnioli

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Re: The 2016 melting season
« Reply #895 on: May 06, 2016, 05:53:02 PM »
You talk about the last 15 years: what is the clearest way of seeing this dramatic loss?

Maybe PIOMAS data?



Perhaps gompertz fits would fit the data better than those exponential curves. Exponential looks too alarmist, but recent bump of last 3 years could well distort gompertz into falsely looking like there is no expected further loss. So maybe neither exponential or gompertz works well and perhaps just straight line fits would be better?
Yep, PIOMASS is definitely one of best ways to show the loss clearly.

As for curves - it is my understanding that Arctic sea ice volume amount at any given months is a function of several significant independent or inter-dependent factors, including but not limited to
 - large weather events during a month and weeks/months prior to it,
 - composition and amount of light-reflecting and/or IR-reflecting particulate in the athmosphere, those being man-made (example - pollution), semi-man-made (say, soot from more forest fires generally caused by AGW), and natural (most notably clouds, ash from volcanoes),
 - volume, location, speed and temperature of incoming into arctic air and water (both salt water and fresh water from rivers and Greenland melt),
 - "quality", area and thickness of previously existed ice (not just average figures, but as a whole massive of data describing state of the ice at each and every location for a large while prior to any given month, since same "average" figures with much different distribution around the basin will produce mighty different feedbacks on further gain/loss of ice volume),
 - global and also local emissions of GHGs (extra methane content being a concern lately for the Arctic especially, and is projected to increase as we go, possibly dramatically).

As such, the resulting sequences of figures is highly unlikely to be a fit for any simple mathematical function, except when most/all factors behave rather stable (linearly), which until recently was quite the case. Especially unlikely volume graph would fit any "curve" if intentional efforts to slow/halt the melt are the part of the deal starting some date "in the middle" of the graph. Humans tend to be quite potent in changing trends, even if for a short while when they eventually fail to prevent the inevitable.

The pre-2013 exponential trend was fitting PIOMASS graphs rather well. One can indeed expect that if the process is going on on its own with steadly (linearly) increasing general energy input (as a function of CO2e, if to consider it in most simplistic way) from the athmosphere, and all "other" things behaving naturally. One can expect it, because the more ice is gone from the picture, the less ice remains "insulated enough" from warmer surroundings to stay much below freezing point. And thus the less fraction of the same delta of energy income will eventually be spent to warm up those "remaining until now much below freezing point temperature" masses of ice to freezing point of water. Which means, the larger fraction of the same energy delta will be instead spent on changing solid ice into liquid water.

And since the thickness of Arctic sea ice is relatively small - mere meters, - this consideration is IMHO the lead reason for Arctic sea ice melt to "normally" be exponential-like process (should be very different for much thicker ice masses such as Greenland and Antarctic main sheets, - those will be melting in very different manner, in several stages, each stage doing its own "thing" as the main melt process - such as formation of large under-ice "lakes" and even "seas" of liquid water under the most of the ice, which happens nowadays).

But now - after 2013/2014, - some of those major factors - one or several, - were changed, and the ice behaved rather unexpectedly. This means no simple curve can now be used to extrapolate the process the way it was used before (pre-2014). The process became too complex to be seen that simply; not with sensible amount of error and generalization, that is.
« Last Edit: May 06, 2016, 06:44:56 PM by F.Tnioli »

epiphyte

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Re: The 2016 melting season
« Reply #896 on: May 06, 2016, 08:25:19 PM »
Unusually for this longditude, Sentinel 1A has before and after images of the crack-up...

These were taken 25 hours apart. If you look carefully you can see dotted-lines of "polyannas" (sic) appearing along shear lines in the earlier image. For in illustration of this, see the zoomed section at the bottom.

[edit  - now that I look at this again - what I said above is not correct... The dotted line does not coincide with any of the new cracks, and is still visible in the later image. ]



« Last Edit: May 06, 2016, 08:32:48 PM by epiphyte »

Andreas T

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Re: The 2016 melting season
« Reply #897 on: May 06, 2016, 09:58:32 PM »
S1A also gave a view of Amundsen gulf on the 3. 5.  http://www.polarview.aq/images/106_S1jpgsmall/201605/S1A_EW_GRDM_1SDH_20160503T151146_649C_N_1.jpg.
 This area of drifting ice has been commented on and is seen in the ice concentration maps but  can't be seen in the visible MODIS images because of cloud cover.

Revillo

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Re: The 2016 melting season
« Reply #898 on: May 06, 2016, 10:23:27 PM »
Some good news today. The NSIDC extent graphs are updating again, though the data is uncalibrated and subject to change.

http://nsidc.org/arcticseaicenews/2016/05/daily-sea-ice-extent-updates-resume-with-provisional-data/

Quote
NSIDC has obtained data from the DMSP F-18 satellite and is in the process of intercalibrating the F-18 data with F-17 data. Intercalibration addresses differences between the series of sensors, in order to provide a long-term, consistent sea ice record. While this work continues, we are displaying the uncalibrated F-18 data in the daily extent image. The daily time series graph shows F-17 data through March 31, and F-18 data from April 1 forward. Initial evaluation of the uncalibrated F-18 data indicates reasonable agreement with F-17, but the data should be considered provisional and quantitative comparisons with other data should not be done at this time.

But we've got some sort of tentative graph for April and May that I can oggle over morning coffee again.

werther

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Re: The 2016 melting season
« Reply #899 on: May 06, 2016, 10:27:16 PM »
One more day in the Kara Sea shows further break-up near Vilkitsky Strait. No fast-ice left soon; the Kara Sea is being set up for complete melt out.