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Messages - slow wing

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1
Arctic sea ice / Re: The 2017 melting season
« on: April 20, 2017, 01:37:56 AM »
Attached is a month-by-month gif of the ice coverage maps from the Arctic and Antarctic Research Institute, St. Petersburg, Russia,
http://www.aari.ru/odata/_d0015.php?lang=1.

The maps are interesting because they track the old ice that has survived at least one melt season - shown in reddish-brown.

One example map was chosen for each month from 2016-10 to 2017-04, with a date around 18th of each month.

Apologies for my poor gif-making skills.

 The gif seems to show a continuing loss of the old ice on the Russian and Atlantic sides that extends in time all the way through to the January 2017 frame. This happened despite new ice completely surrounding the old ice region.

  It is seen that the old ice has been pushed away from the Russian side and also nibbled away at on the Atlantic side - the infamous 'Atlantic kill zone'.

   The pattern by now seems to be a continuation of that movement away from the Russian side. That is now driving a bifurcation, with some of the compressed ice turning left and heading towards the Atlantic side kill zone and the rest turning right towards the Beaufort Sea.

   The latter seems to be the 'Beaufort gyre' setting up due to the recent high pressure systems in the Beaufort. If that continues then this year will again have a wall of old ice between the Beaufort Sea and Central Arctic Basin (CAB), albeit thinner ice than last year.

2
Arctic sea ice / Re: The 2017 melting season
« on: April 15, 2017, 12:58:06 AM »
Great animation Andreas. Any idea of the total distance moved? Is this something like 1000 km?
sorry, that 100km marker is only partly shown. On average the northern edge of the area is just south of 85degN. That makes it a little over 500km long. Width is about 300km
Yes, very nice plot Andreas. Thanks for posting it.

Concerning the length of the designated region and its Northern edge, the North Pole is where the two lines of constant longitude intersect.  I used 2 rulers to find the point of intersection (i.e. the position of the North Pole, not shown in the images) and to extimate that the Northern edge of the designated area intersects the 0 degrees longitude line at ~86degN.

The length of the line segment inside the area and down to the 80degN curve is therefore 6 degrees of latitude, which is around 670 km.

So that means the ice starting at the Northern end of the line segment travelled about 670 km
out through the Fram Strait in the 2 months beginning on 12 February. That's an average flow speed of around 20 km per day.


Approximating your area by a rectangle with the Southern side at 80degN then the width of the rectangle is about 60% of its length.

So the ice area enclosed is ~ 0.6 x (670 km)^2 ~ 270,000 km^2

That area can be considered lost by export in ~61 days, or ~4400 km^2/day.

If assuming the ice thickness averages 2.3m = 0.0023 km then 4400 x 0.0023 = 10 km^3/day
is lost by Fram export; a total of ~600 km^3 over the 2 months.


If we approximate the maximum sea ice volume this year at ~20,000 km^3 (from PIOMAS) then the fraction lost is:
~600/20,000 ~ 3%.



So Andreas' animation shows about 3% of this year's maximum Arctic sea ice volume has been lost by export through the Fram Strait over the past 2 months.

3
Arctic sea ice / Re: Stupid Questions :o
« on: April 06, 2017, 07:55:03 AM »
No, the break even day is not the equinox.

The vernal equinox has passed but I very much doubt that break even has been reached for a clear sky over the North Pole.

Break even - presumably defined as when the surface temperature holds steady - requires the outgoing energy to balance the incoming energy.

The plot below from NASA, though intended for a slightly different purpose and displaying numerical values that wouldn't be appropriate at the North Pole, shows the contributions.

Outgoing from surface:
longwave thermal radiation from surface (will dominate at the moment at North Pole)
sunlight reflected from surface (EDIT: this isn't part of the thermal energy balance)
thermals
evapotranspiration


Incoming from atmosphere:
downgoing longwave thermal radiation from atmosphere (will dominate at the moment at North Pole)
incident sunlight absorbed


The values and relative sizes of these terms will depend on surface temperature, atmospheric temperature profile, surface emissivity/reflectance (which depends on wavelength and is very different for ice than for liquid water), atmospheric moisture content and the elevation of the sun above the horizon.

So there's no fixed date for break even.

In general, break even at the North Pole or in the Arctic, with a clear sky, can only occur when the sun is well above the horizon - so that will be well past the vernal equinox.

4
Arctic sea ice / Re: Latest PIOMAS update (April)
« on: April 05, 2017, 11:24:04 PM »
Thanks for the update Wipneus, much appreciated.

Those year-to-year differences maps for 31 March are telling: the ice appears in worse shape this year than in any of the previous years shown, apart from that blob of thick ice poised over Fram Strait.

5
Arctic sea ice / Re: The 2017 melting season
« on: April 05, 2017, 10:21:52 AM »
Looks like it's setting up for a Siberian high.
Yes, I'm thinking that should offer some temporary respite for the ice, following all the strong low pressure systems of past weeks.

  The forecast winds around the Arctic basin over the next several days are relatively weak and, with the sun still low on the horizon, clear skies from the high should allow long wave thermal radiation to escape to space without the ice being exposed to too much down going short wave radiation.

6
Arctic sea ice / Re: The 2017 melting season
« on: April 02, 2017, 12:58:31 PM »
Arctic Sea Ice Currently Taking a Hit From All Sides
Yes, the Arctic sea ice seems to be taking a hit from all 4 sides of the Arctic Basin at the beginning of the melt season.

Summarising recent posts above:
1) Russian side - big cracks and areas of low concentration as the ice is blown out to sea
2) Atlantic side - ice blown out into the Barents sea, where bottom melt might be expected
3) Ice transport through the Nares Strait seems to be setting up
4) Ice is being blown out through the Bering Strait and the ice already South of there is breaking up and being blown further South.


U. Bremen Ice Concentration Map Year-on-Year Comparison for 1 April
April 1st is one of the chosen days for Neven's useful year-to-year comparison of the U. Bremen Arctic sea ice concentration maps.

As attached below, this comparison shows the ice this year on the Russian side - i.e. the ESS and Laptev Sea (red arrow) to be, on the face of it, in the worst state for this date of any of the illustrated years.


CPOM/ESA Spring Ice Thickness Maps for 2011-14 and 2017
The CPOM/ESA measurements of ice thickness are wrapping up for the end of this freeze season. As they are actual measurements - albeit with corrections - rather than more model-based assessments, I tend to consider that they probably give the most accurate picture of the ice thickness distribution over the Arctic Basin. Also attached then is a gif showing their latest 28-day map compared against the years for which they publish well-calibrated Spring maps, namely 2011-14.

  From these maps, the 2013 Arctic sea is seen to have been in terrible condition after the carnage of the record 2012 melt season. On the face of it, 2013 had less thick ice around this date than even this year, in contrast to the other years shown having considerably more ice than this year.

   And yet 2013 turned out to be a recovery year for the sea ice, which suggests that this year also has that potential in the case that this year's upcoming melt season turns out to be mild. On the other hand, is this year's ice already being blown around more than was the case in 2013?

   The bottom line from this comparison is that a mild melt season this year could still lead to a recovery in the Arctic sea ice but, on the other hand, a historic low minimum extent in 2017 is looking quite likely. It's early days yet.

7
Arctic sea ice / Re: The 2017 melting season
« on: March 31, 2017, 02:48:07 AM »
WorldView shows the big tears in the ESS and Laptev Sea and the exposed water gaps next to them.

Compare with last year on the same date: the outer boundary of the fast ice was still visible as a crack but the ocean side still had solid ice right next to the crack (albeit with some smaller fractures visible).

EDIT:
2015 was similar to last year.

A bit more action was seen in the Laptev in 2014 although less dramatic than this year and, again, there was no big water gap in the ESS.

8
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: March 29, 2017, 04:18:12 PM »
Wipneus and SeaIceSailor,

  Thanks for your comments on the potential causes of the concentration loss observed in the Laptev Sea.

  Yes, a snow/rain connection looks reasonable: toggling to the "3-hour precipitation" option on Nullschool and stepping through the 3-hourly displays does indeed show precipitation of order 1 mm (which could be ~1 cm if it fell as snow) drifting over the region around that time.

9
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: March 29, 2017, 02:32:59 PM »
The crack in the ESS is getting real wide. The Laptev fast ice is torched.

Wow! So what is happening here?

 EDIT: U. Bremen's AMSR2 concentration map for 2017-03-28 is also showing the loss - with around 75% concentration in the fast-ice region of the Laptev Sea that has gone dark in Wipneus' graphic.

Is it melt ponds or is there actually no ice over around 25% of that region?

Options:
A. We're only just past the equinox, there presumably won't be enough sunlight to cause melt ponds, fair?
B. But it's plausible that winds could have melted some snow cover?
C. Alternatively, the ice could have been in such a poor state that the winds tipped it over the boundary to where much of it is no longer classified as ice cover?
D. Or it might be tearing in the wind and now full of micro-cracks?

Anyone more knowledgeable have a take on which of the options is most likely?

The screenshot is from Nullschool at 12:00 UTC on 2017-03-27.
The illustrative chosen point in the Laptev Sea with the green circle is showing 25 kph winds at -2.6 degrees C.

10
Arctic sea ice / Re: The 2017 melting season
« on: March 27, 2017, 10:05:16 PM »
SeaIceSailor,

  My guess at the reason why there are no visible cracks in the Beaufort Sea at the moment is because it has been under fairly constant compression over at least the past month. So the lack of cracks probably doesn't speak much to the quality, or otherwise, of the ice there.

11
Arctic sea ice / Re: Roundhouse punches from the ApocalyptoKraken
« on: March 27, 2017, 08:41:29 AM »
Thanks Hyperion, I agree that it's interesting to look at the potential contribution of atmospheric water to Arctic sea ice melt so I will take you up on your 'peer review' offer...

...
Quickstab at what this setup might mean numerically. Peer review and alternative approaches most welcome:
 ;)

1,680,000,000,000,000J
18.748 kg/sqm
200km x 50kmph (ballpark flow estimate) x 24hr = 240 000 sqkm = 240 000 000 000 sqm
240 000 000 000 sqm x 19 kg x 4200J = 19,152,000,000,000,000 Joules per day
=19.52 petajoules per day
...

That's the specific heat capacity of water - the amount of energy required to raise the temperature of 1 kg liquid water by 1 degree Kelvin \ Celsius. Better to use the heat of evaporation as the "Total precipitable water" is almost all vapour (use "Total cloud water" option to see the small part that isn't) and can melt ice by condensing. This contribution to heating the ice is much larger than the heats from temperature changes.

Water properties here.
It's actually even easier to use the ratio of heats of vaporisation to fusion.
Latent heat of melting - 334 kJ/kg
Latent heat of evaporation - 2257 kJ/kg
Ratio ~ 2257 / 334 ~ 6.76. So each kg of water vapour can, by condensing, cause the melt of nearly 7 kgs of ice.

Expressed in scientific notation, you estimated 2.4e11 m^2 of moist air entering the Arctic per day, carrying 18 kg/m^2 of water vapour, so on multiplying you say about 4e12 kg/day of water vapour entering the Arctic.

From above, this could melt 2.4e11 x 18 x 6.8 kg/day ~ 3e13 kg/day of ice.

To see if this would be a relevant amount, we should ask how many kg of ice are in the Arctic?

From PIOMAS, we see that the volume of Arctic sea ice at the end of the freeze season is around 20 000 km^3 ~ 2e13 m^3. Ice weighs around 900 kg/m^3, so this is ~ 2e16 kg of ice.

On comparing the two, it would take several hundred days to melt all the ice at the assumed rate of ingress of water vapour and assuming a large fraction of it condenses to melt ice.

  As an initial impression, I would also say that the rate of ingress you assume is anyway much larger than would be typical, perhaps by an order of magnitude or more.


So this back-of-the-envelope calculation suggests that the ingress of atmospheric water vapour into the Arctic can't account for a large fraction of the yearly ice loss. However, it wouldn't be surprising if it contributed at the percent level or maybe up to a few percent of the ice loss.

Given the observed rise in atmospheric moisture beginning around the start of 2016, this could still mean a significant rise in sea ice loss by this mechanism.

Presumably this has been studied at a more rigorous level. Does anyone know of such a study and their findings?
EDIT: already answered and it has been studied. Thanks, Jai Mitchell.

12
Arctic sea ice / Re: The 2017 melting season
« on: March 26, 2017, 03:09:27 AM »
Terrific, Hyperion!

Yes, start a thread please.

The greatest of respect to the many dedicated scientists, technicians etc. who are already providing the experimental information we rely on to understand the state of the Arctic.

Having said that, it's a disgrace that we don't have more coverage; a disgrace that we need inadequately calibrated models for the currents, water temperatures and salinities, etc - as well as information on the ice and snow state and thickness.

   Smart probes for the Arctic are difficult to fund even while smart bombs are streaming off the assembly lines.

   More broadly than your particular solution, it makes a lot of sense to have a thread on the future experimental program for monitoring the Arctic.

   Better in"Policy and solutions" or in "Science"?

   I had a look previously and couldn't find an existing thread. (Did I just miss it?)

   So there were a series of posts in the "What the Buoys are telling" thread kicking off with this one from me and then with those more knowledgeable and experienced posting valuable content.

Maybe all that can be moved to a new dedicated thread for e.g. "Existing and proposed experimental apparatus and programs for the Arctic" and add your stuff and other proposed solutions?

13
Arctic sea ice / Re: The 2017 melting season
« on: March 24, 2017, 12:50:07 AM »
"...the Arctic turns into a single gyre"?

 There hasn't even been a gyre lately. Instead the ice in the Arctic Basin has been blown from the Russian side and compressed against the Canadian side, with some leaking out towards the Atlantic...




  The good news is that the compression has helped to heal the Beaufort Sea back to around a 2 metre thickness.

   And if the pattern ends soon then there is still well over a month left of weather cold enough to somewhat heal the tears on the Russian side.

   But what if the tear-and-compression continues well into April or May? Will large stretches of water remain open on the Russian side, efficiently absorbing the peak insolation around the Summer solstice?

  A broader question is why so much compression? Is there enough thin and weak ice this year in the Arctic Basin that any wind pressure from the Russian side will always result in movement and compression? And is this movement replacing the Beaufort gyre of seasons past, with the ice now compressing rather than transferring the force for rotation?

   If so, does this mean that maximum Arctic sea ice volume for the year has descended this season to a transition value, or even a tipping point, where the ice will continue to tear-and-compress from the Russian side heading into the Summer melt season, with the Russian side therefore opening up anomalously early?

   Or, instead, will the movement damp down within a few weeks and those consequences won't come to pass this year?

   Either way, the plot twists and turns of the melt season are going to provide us with riveting viewing.

14
Arctic sea ice / Re: Arctic Image of the Day
« on: March 20, 2017, 10:16:59 PM »
It's Icepacman!  :o

15
Arctic sea ice / Re: The 2017 melting season
« on: March 14, 2017, 08:42:52 PM »
Thanks Romett1. Yes, the HYCOM prediction is scary, with a lot of thicker ice either exiting through the Fram Strait or else heading in that direction.

  A lot of the thickening in the Beaufort Sea appears to be from compression, with the ice blown towards the Alaskan and Canadian Arctic coastlines.

  It's going to be critical how much new ice grows over the next month on the Siberian side to replace the ice that has migrated West. Are we going to have much of the thin ice on the Atlantic side of the Laptev Sea melted out and exposed to peak insolation by around the Summer solstice?

16
Arctic sea ice / Re: Stupid Questions :o
« on: March 14, 2017, 04:41:55 AM »
OK, that's a different statement. Note however that last year, 2016, didn't top out early and last year also had anomalously high 80N+ temperatures at this time of year.

At the beginning of March this year was about 2K km^3 below 2016 - which topped out as the record min-max (~tied with 2011) - so, yes, it wouldn't be too surprising if we ended up around 2K km^3 below that.

17
Arctic sea ice / Re: Stupid Questions :o
« on: March 14, 2017, 03:14:43 AM »
This is as much ice as we are going to get.

Based on what? It's only mid-March. According to PIOMAS, ice volume typically grows into mid-April - so another month or so.


18
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 05, 2017, 01:10:42 AM »
Terrific information, thanks Andreas! Your reply, #1387 above, beautifully addressed my question on how much insolation the Arctic actually receives.

What a great forum this is!

19
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 04, 2017, 10:46:35 PM »
I'm still uncertain on how much insolation the Arctic actually gets.

Is the plot showing insolation on a horizontal surface? Or on a tracking surface always perpendicular to the sun? (I presume the former.)


More importantly, does it include a model or measurement of the effects of the atmosphere, including the variable moisture content and cloud cover? If it's insolation at the top of the atmosphere then that's much larger than what reaches the ground. That is particularly true in the Arctic, given the typically low solar elevations from the horizon.

  The Arctic was cloudier than usual last summer, so the insolation reaching the ground would also have been less than usual. Will this summer be similar?


So the question of how much insolation reaches the Arctic is not simple and is not fully addressed by a single graph.

20
Arctic sea ice / Re: Poll: 2017 PIOMAS Maximum Monthly Figure
« on: March 04, 2017, 10:27:46 AM »
Voted 20.5-21.0 x 10^3 km^3.


At day 59 we were at 18.6 in those units.

Archimid posted on the PIOMAS update thread that, in past years, the average gain to maximum from there has been 2.1. Taking the average gives 18.6 + 2.1 = 20.7 - hence the choice of bin.


It could be argued that the Arctic Basin hasn't been as cold as usual this year, with FDDs way down. That trend may well continue over the next month or two.

On the other hand, I see lots of potential for adding volume in the 'ice factory' on the Russian side of the Arctic Basin. Offshore winds there have been, and still are, exposing new sea surface there which is rapidly freezing over and thickening.

So I think taking the average gain from day 59 to maximum ice volume is reasonable.







21
Developers Corner / Re: Mapping GeoCoded Data Sets
« on: February 26, 2017, 11:58:06 PM »
Hi CognitiveBias

   Yep, that should also be fine. I might have been getting ahead of myself thinking about a problem that doesn't matter - your option of using Sept 1 everywhere is simpler and it would be great to get a first look at the distributions!

22
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 26, 2017, 11:27:49 PM »
2/2 (needed a second post due to 4 attachment limit)

Continuing with inspecting the Canadian Ice Service (CIS) charts of the 2009 melt season in the West Arctic, which corresponds roughly to the Beaufort Sea as well as some of CAB between the Beaufort and the North Pole. Recall from the posts above that the sea ice in the West Arctic currently (late February) looks worst in the CIS archives and that 2009 looks the second worst.

  It turns out that the first year ice mostly melted out anyway by the end of the 2009 melt season in the West Arctic, but much of the multi-year ice survived.


  So that gives us some idea of what might happen again in the West Arctic this year, in the scenario of similar weather to 2009 over the next several months. Unsurprisingly, the Beaufort Sea will melt right out. But the multi-year ice North of that could survive.


  In the alternative scenario that the stormier weather of 2016-7 persists into the 2017 melt season, then much of the multi-year ice currently in the West Arctic may also be lost, due to transport by the wind into either the CAA 'garlic press' or into a Beaufort Sea 'kill zone' that has already melted out.

Attached: Canadian Ice Service chart for West Arctic on 2009-09-28.

23
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 26, 2017, 11:17:54 AM »
[EDIT: I redid this post as I was dissatisfied with my original characterisation of the 2009 charts]

1/2
Had further look at the archived Canadian Ice Service(CIS) sea ice charts for the Beaufort Sea. Previously, I had only looked back to 2010 whereas the archive goes back to 2004.

It turns out that the 2009 Beaufort ice also looked fairly weak at this time of year - the weakest in the archive outside of this year.  (The years earlier than 2009, however, had considerably more thick ice than this year.)

  As one historical surrogate then for the potential Beaufort sea ice development this melt season, the 2009 progress of the Beaufort ice can be examined for through the end of the freeze season and then for the melt season. On inspection, it turns out the 2009 Beaufort ice continued to thicken until at least mid-March and most survived well into July.

The relevant charts from the CIS archive follow, for dates in this order:
2017-02-20 (repost) - the ice condition this year; note all the light green = 1st year ice <120cm thick
2009-02-16 - note that 2009 also had a lot of light green around mid-February
2009-03-16 - one month later, the light green has ~all gone dark = >120 cm
2009-07-13 - the Beaufort hadn't melted out much by mid-July 2009

24
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 24, 2017, 11:32:48 PM »
4/4 It is seen that this year stands out in having the least multi-year ice (brown) in the region and easily the most light green, which is first year ice of 70-120 cm thick - presumably too thin at the moment to stand much chance of surviving the next melt season.

Shared Humanity also has a good point about the CAA now turning into a sink (the 'garlic press', as Neven has coined) rather than a sanctuary for thicker multi-year ice.


So the Beaufort Sea looks in trouble this season.


Concerning a wider view of the Arctic ice, it's helpful to have this region with detailed charts that are presumably reliable. These can be used for assessing and maybe even cross calibrating some of the other ice maps that show the entire Arctic Basin.

25
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 24, 2017, 11:22:14 PM »
Some explanation on how to read the charts.

Canadian Ice Service has a detailed explanation in their online Manual of Ice (MANICE), the most relevant page of which is the start of Chapter 3: Observed Ice Charts, at http://www.ec.gc.ca/glaces-ice/default.asp?lang=En&n=2CE448E2-1&offset=6&toc=show.

Briefly, the little "Egg Code" number charts are very helpful in giving the concentration, stage of development (e.g. "First stage thin first-year,   30 - 50 centimetres") and form (e.g. "Big floe,   500 - 2,000 metres") of each designated local region of ice.

The most relevant colour coding for us is:
'light olive' = thin first year ice, 30-70 cm thick
light green = medium first year ice, 70-120 cm thick
dark green = thick first year ice, >120 cm thick
brown = older than first year ice.

Here is a map of the Western Arctic region displayed ...



26
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 24, 2017, 11:02:36 PM »
Above was the charts closest to 20 February for 2017, 2016, 2015 and 2014; now the same for
2013, 2012, 2011 and 2010...


27
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 24, 2017, 10:59:30 PM »
Thanks again, Jim. Canadian Ice Service have a superb website,
http://www.ec.gc.ca/glaces-ice/default.asp?lang=En, with a fine archive facility, retrieving ice charts at:
http://iceweb1.cis.ec.gc.ca/Archive/page1.xhtml?lang=en.

From the options tables, I selected:
Weekly Regional Ice Charts - WMO Colour (2003 - 2017)
Western Arctic Regional
... and saved to zip the weekly charts for around this date for each of the past 8 years (files end in "SD'), as follows (latest to earliest year)...

28
Arctic sea ice / Re: Glossary ... for newbies and others
« on: February 24, 2017, 09:43:09 PM »
Thanks shmengie! I didn't know that and it really works!

29
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 24, 2017, 11:29:13 AM »
Thanks Jim, appreciated.

2017, 2016, 2015 and 2014 sea ice in the Beaufort compared by ACNFS for 23 February...

The code version has changed between years, and the colour palette has slightly. But the difference this year is still striking! :o


Now it really would be nice to also check this using the Canadian maps for the Beaufort!

30
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 24, 2017, 06:37:21 AM »
For comparison, it would be great to see ACNFS maps for the same dates in previous years. Are any available? Or that other Canadian sea ice map?

Does either have a map archive on their web page?

I had a quick skim of last year's freezing season thread,
http://forum.arctic-sea-ice.net/index.php/topic,1377.500.html
and couldn't immediately see a corresponding map.

Shouldn't those maps in particular give about the best information available on whether the Beaufort sea ice is in better or worse condition than last year?





As consolation, here's a gif Neven did of the Atlantic side about a year ago, taken from last year's thread. The ice around Svalbard wasn't in good shape then either...
It seems that it is now (almost?) possible to circumnavigate Svalbard. It is a little early for that, isn't it?


Nah, we're not impressed by that one anymore. Circumnavigating Svalbard AND Franz Josef Land, however, is a different cookie:  ;)





31
Arctic sea ice / Re: IJIS
« on: February 15, 2017, 07:21:07 AM »
It appears that the strong upwards trend should continue in the next few days as well.

At least that's how I interpret the 'ARC' prediction map posted by Tigertown in post #2779 on the Freezing thread:
http://forum.arctic-sea-ice.net/index.php/topic,1611.msg103206.html#msg103206.


That should take this year's IJIS extent out of first place, probably beginning tomorrow.

32
Developers Corner / Re: Mapping GeoCoded Data Sets
« on: February 12, 2017, 01:44:42 AM »
Thanks for the interest in a map of FDD and for looking into coding it up. I am looking forward to seeing these plots and - thanks Blizzard for the links - there is an outside chance I might try to learn Python to try something myself, but likely not realistic.


Would like to raise one issue of definition: when is the first day to use for calculating FDD(x) at each point, x (shorthand for a two dimensional coordinate)?


Use a single, universal date for the whole map, i_start? This seems a poor solution to me. The problem with that is that the colder places will begin freezing before the warmer ones. The warmer places would still be having days above the reference temperature, Tref (either 0 or -1.8 degrees C, not sure that has been decided?) while the cooler places begin accumulating FDDs.

  A better solution imo would be to store a separate start date, i_start(x) appropriate for each point x on your 2-dimensional map grid.

Further, I would propose a suitable definition for i_start(x) as the start day that maximises the FDD at that point x.

That is, the FDD at point x on day n, FDD(n,x) is determined by stepping over days, j, and finding the maximum for:


FDD(n,x) = max. for i_start(x) of, sum[j=i_start(x),n] (Tref-T(j,x)).


The day i_start(x) only needs to be determined once for each x - just step through the days up to any day n well into the freezing season and record the value of i_start(x) that maximises it.


Has anyone encountered this as an issue? Does the above proposed solution make any sense?

33
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 03, 2017, 05:12:50 AM »
...
  However, the FDD daily map itself is actually dead easy to do given the daily temperature maps for the Arctic Basin. As I said, one simply increments the FDD value at each location by the degrees freezing for the day at that location. Done!

  That procedure gives a perfectly well defined FDD-to-date map.

   I would suggest also that this FDD is intrinsically interesting - it tells you how cold each location or region of the Arctic Basin has been during the freezing season. That extends greatly on e.g. the one parameter information available from the FDD 80N graph.

  The maps can be compared for different years. E.g. "has the Beaufort Sea been colder than usual this freeze season?"

 
 The FDD 80N graph itself can be derived from the FDD-to-date maps, as can FDD graphs for the entire Arctic Basin or for any other defined region. So the maps are useful for that purpose as well.

...

Thanks for you posts extending on my localized temperature post, slow wing.  I had hoped some might find this data 'intrinsically interesting' as I do.  You have provided the logical next step I was looking for, and my next project.   

--CB
Great stuff! Thanks for following up.

34
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 02, 2017, 07:58:32 AM »
Thanks for your reply, Tigertown.

  I agree up to a point.

  However, the FDD daily map itself is actually dead easy to do given the daily temperature maps for the Arctic Basin. As I said, one simply increments the FDD value at each location by the degrees freezing for the day at that location. Done!

  That procedure gives a perfectly well defined FDD-to-date map.

   I would suggest also that this FDD is intrinsically interesting - it tells you how cold each location or region of the Arctic Basin has been during the freezing season. That extends greatly on e.g. the one parameter information available from the FDD 80N graph.

  The maps can be compared for different years. E.g. "has the Beaufort Sea been colder than usual this freeze season?"

 
 The FDD 80N graph itself can be derived from the FDD-to-date maps, as can FDD graphs for the entire Arctic Basin or for any other defined region. So the maps are useful for that purpose as well.




  Where the issues of drift etc. come in is when one tries to derive an ice thickness map from the FDD daily map, e.g. using the Lebedev formula. As you suggest, the corrections, or else the uncorrected deviations, might be quite large. How large? It might be quite interesting in and of itself to find out. To the extent the ice depth prediction has interest, correction procedures can be come up with and applied.

35
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 02, 2017, 07:07:12 AM »
Yes, this FDD (Freezing Degree Days) is a nice idea to get a handle on the depth of ice expected.

The FDD 80N is just a one-parameter measure. Cognitive Bias has posted a couple of other such measures above, at #2438. Yet another one would be the average FDD over a defined boundary for the Arctic Basin "the FDD Arctic Basin".

 This freezing season's anomaly in the FDD 80N parameter appears to come largely from the Atlantic side, particularly around the Barents Sea area where the open water is - at least that is the impression I get from the daily temperature maps and temperature anomaly.

I'm wondering if FDD Arctic Basin would show quite as large an anomaly? Have the temperature anomalies been as large on the Beaufort Sea side of the Arctic Basin? I haven't followed it closely enough to confidently answer that one.


   As an extension to this analytical tool, a daily FDD map could be constructed from the daily temperature map for the freezing season up to the current date  ("FDD-to-date map") over the Arctic Basin. (Specifically, just add the "freezing degrees" for the day at each location to the accumulated FDD value at that location from yesterday's map.)

   Neglecting ice movement, such a map would predict - using the Lebedev formula or the other one - ice thickness at each date and for each location within the Arctic Basin (at least where there was no ice at the start of the freeze season, as well as where the initial thickness was known or estimated).

   Would that simple thickness prediction correspond well with the actual measured thickness at each location? It ignores factors such as water temperature and salinity below the ice. Even if not, would the difference give us information on those and other factors at each location? Also, the Lebedev parameterization could be assessed and improved.

  Unfortunately I have neither the time nor the coding wherewithal to create and keep current such an FDD-to-date map. But anyway that is a suggested extension to the interesting concept of FDD if anyone happens to be interested.

36
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 02, 2017, 03:30:53 AM »
My current understanding/prejudice is that the most reliable thickness data for the current Arctic sea ice is the Cryosat NRT data from CPOM:
http://www.cpom.ucl.ac.uk/csopr/seaice.html.

As I understand it, that data set is from actual measurements rather than models. Also, I haven't heard so far of any reason not to trust its accuracy.

 Is that fair? I have no reason for bias but am simply an amateur.



So I wanted to compare this year's status to previous years, using that site. Only certain data sets are readily available that I can see, and so the gif below shows some sort of apples-to-oranges comparison.

The frames are, in order
1) Latest 5km Grid of 28-day Thickness : 2/1/17 - 29/1/17 (shows for 200 ms)
2) Thickness over March+April 2011 (shows for 50 ms) = "Spring 2011"
3) Spring 2012
4) Spring 2013
5) Spring 2014
(Those are the only years I can see readily available.)

So basically its comparing the ice thickness around mid-January 2017 with that around the end of March for 2011 to 2014.

So we have to imagine how much ice will be added over the next month-and-a-half if we want to see if we are worse off, or better off, than in those previous years.

  The worst ice situation from those previous years was in 2013.

   As can be seen from the gif, the ice pack in the vertical middle of the plot - i.e. excluding the Beaufort, Chukchi and Bering Sea on the Pacific Side and the Barents, Kara etc on the Atlantic side - was not really worse than currently. Add another month-and-a-half of ice growth and that part might generally be thicker in Spring 2017 than it was in 2013.

(Say add about a half-metre of ice then, roughly:
dark blue -> light blue
light blue -> green
green -> yellow
yellow -> red
etc.)

So the vertical-centre part as described above will probably not be the weakness this Spring.

Instead, the worry is the Pacific and, particularly, Atlantic peripheral seas. These are seen to have much less ice than in previous years, albeit shown 1.5 months later.

The worst sea in the comparison is probably the Barents Sea. Unless the ice is added there, quickly and dramatically, the Barents Sea is likely to melt out early in the upcoming melt season. That, in turn, might make the whole Atlantic side into a 'kill zone' for any ice drifting over there during the melt season.

On the Pacific side, the Beaufort, Bering and Chukchi Seas might also melt out earlier in the 2017 melt season than they did in 2011-14, forming another 'kill zone', on the Pacific side. We already saw that feature in 2015 and, even more, last year.



  In summary, a quick comparison was made of the available CPOM CryoSat NRT Arctic sea ice thickness data for this January vs. Spring in 2011-14. The main conclusion is that the sea ice this melt season looks likely to be vulnerable on the Atlantic (mainly) and also Pacific sides. Now it's all up to the weather and currents over the next six months.



The gif needs a click to start.

37
Arctic sea ice / Re: The 2016/2017 freezing season
« on: January 28, 2017, 05:18:52 AM »
FOOW,

   Thanks for the sea surface height and surface salinity plots.

   Are they as extraordinary as they seem to an amateur such as me?  For example, the surface salinity just North of Severnaya Zemlya is not much less than that of the bulk Atlantic Ocean! The orange region extends to about the North Pole.

   Is that reliable? (Where does it come from? Is it e.g. derived from satellite measurements of sea surface height plus interpolating between buoy readings?)

   Presuming it's reliable, how anomalous is that for this time of year?

   Is it fair to say that the usual thermohaline depth structure must have largely broken down in the reddish (and, less so, orange) regions within the Arctic Basin proper? And, consequently, that any warmer Atlantic water transported into those regions is now more likely to mix from the storm churn than it is to sink due to any greater salinity and hence density? If so then is it reasonable to assume that any heat transported into those regions from the Atlantic currents from now on will largely be available to melt the sea ice where in past years it would not have been?

   And, as you have indicated, the high salinity regions appear to correlate with regions of sea ice damage as pointed out and plotted by A-Team.

   I have no expertise or background knowledge in this area but these plots appear to me like they could be important. Perhaps could you and others please give some more expert interpretation of these plots and what they mean for the Arctic sea ice? Thanks.

38
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 05, 2016, 10:08:07 AM »
A-Team, thanks very much for your continuing posts that have certainly helped with my understanding.

The bathymetry connection is fascinating.

So is it conceptually useful to separate some analyses into the 'deep' Arctic Basin and 'shallow' Arctic Basin, with an ocean depth scale of order 100m used for the partition?

Then 'shallow' corresponds largely to the Russian side as well as the CAA and peripheral seas on the Atlantic side. 'Deep' is most of the rest of the central Arctic Basin.

If 'shallow' then:
  - mixing processes such as waves and Ekman pumping - with characteristic depths scales in the tens of metres - can therefore reach over much of the ocean depth.
  - warm, heavy salty currents from the Atlantic and Pacific Oceans can still potentially mix with the surface layer of water, bringing heat and salinity to the ice at the surface.

If 'deep':
  - there is probably still a stable and persistent salinity gradient below of order 100 metres
  - the warm Atlantic and Pacific Ocean currents have already sunk to below that depth, and so below where they could potentially influence the sea ice.


Your wonderfully informative graphics in your post #1182
appear to show the ice having remained/formed preferentially over the 'deep' Arctic Basin and you have posted previously about the mixing and trapped heat retarding ice formation in - from memory - the ESS.

  With all the presumed mixing from storms this year, maybe the 'shallow' Arctic is in historically poor condition for ice formation and growth over the Winter? While the 'deep' Arctic might be expected to be less affected?
 

39
Arctic sea ice / Re: Piomas vs. CryoSat
« on: November 24, 2016, 02:21:02 AM »
Thanks diablobanquisa, that's very interesting.

Presumably they are all 28-day Thickness maps collecting measurements over 24/10 - 20/11?

So this is precise and well-calibrated for year-to-year comparisons?

It shows almost no ice thicker than 2 m at that time of year in 2011, then 2013 a big recovery year before falling away again.

This year at least has some thicker ice off the Canadian Arctic coastline but the overall extent is of course the lowest.

40
Arctic sea ice / Re: Arctic Image of the Day
« on: November 22, 2016, 06:32:40 AM »
Nice image, Cate!

It was taken by Patty Waymire and published in a National Geographic feature on climate change:
http://yourshot.nationalgeographic.com/stories/climate-change-focus/

"A solitary bear sits on the edge of one of the Barter Islands."

Barter Island (singular, according to Wikipedia) is on the Arctic Coast of Alaska:
https://en.wikipedia.org/wiki/Barter_Island

41
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 20, 2016, 01:01:05 AM »

.... just because 2016 is starting to superficially resemble earlier years (in terms of diminishing open water), it is not starting to resemble 2015 in terms of ice thickness (or its integral, total ice volume).


Quite true. 

Ice thickness formation has been in the literature since at least Bydin in 1933.  Lebedev in 1938 presented the formula: thickness (cm) = 1.53 * FDD ^ 0.59 (where FDD is Freezing Degree Days). Berillo in 1961 gave 1.33 * FDD ^ 0.58.   Chris Reynolds covers the basic thermodynamics that leads to these formulas in his post The Simplest Model of Sea Ice Growth

Eyeballing the current DMI N80 graph it appears we've accumulated about 600 FDDs since the end of the melt season.  Baseline would be about 1300 FDDs.  A thickness deficit of 700 FDDs would imply a reduction in thickness of 0.3m (based on 3100 projected FDDs compared to 3800 FDDs for recent years).

Temperatures can return to somewhere near normal and extent can return to somewhere near normal, but it's highly unlikely that the size of the FDD deficit can be recouped.  Ice is going to be significantly thinner come the 2017 melting season.

Thanks ktonine, very helpful post.

Do I have your calculations correct though?
"Berillo in 1961 gave 1.33 * FDD ^ 0.58"

FDD_baseline = 3800
FDD_2016proj = 3100

H_baseline = 159 cm
H_2016proj = 141 cm

H_deficit2016 = 18 cm.

So the predicted ice thickness in that scenario would be about 18/159 = 11% down from the baseline at the start of the 2017 melt season.


That is for new ice. For multi-year ice, both the fractional and absolute reductions in thickness will be less in this model.

42
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 19, 2016, 11:55:46 AM »
No more strong Arctic storms in the forecast horizon for the coming week, and a high pressure system settling in in the central Arctic Basin.

Temperatures there should drop. Will the DMI temperature graph drop down as far as the baseline, this month? Before the end of 2016?

43
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 14, 2016, 10:55:37 PM »
bbr,

  Yes, the high, and rising, average surface air temperature above 80N is unprecedented for the date in the DMI record, going at least as far back as 1958, as Terry has checked & posted on another thread.

  This is as I predicted yesterday in comment #671 above.

  It is caused by the strong low pressure currently at 954 hPa that is entering the Arctic Basin through the Fram Strait and is additionally opposed by high pressures above 1040 hPa over Siberia - see first graphic below.

  This dipole setup across the Atlantic side of the Arctic is sweeping warmer (and presumably moisture laden) strong winds into the Arctic basin - see the nullschool graphic below. The point marked by the small green circle, North of Svalbard, registers 64 km/h winds at +0.4oC.


  The current air pressure configuration, at its current strength, is probably also unprecedented in the records for the Arctic at this time of year, given the unprecedented DMI temperature value.

44
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 14, 2016, 04:12:59 AM »
Yep, fantastic work, A-team and the others working on this - really helps to understand what is going on.


  In the short term, yet another strong storm is predicted to be entering the Arctic Basin through the Fram Strait around tomorrow, with a central pressure bottoming out in the 950s in hPa - see attached graphics.

This will bring waves and strong, warmer, moist winds into the Arctic Basin from the Atlantic side.

For those watching the graph of average surface air temperature north of 80N, that should bump the temperature value up even further above the temperature baseline for this time of year. 

45
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 07, 2016, 11:54:49 PM »
A strong low pressure system is currently entering the Arctic Basin through the Fram Strait.

GFS predicts it to bottom out in about 12 hours at around 966 hPa.

How much of an effect will this have on current and future sea ice formation on the Atlantic side?

Waves disrupting ice formation?
Waves and Ekman pumping mixing in warmer, saltier water from the Atlantic near the ice edge?

I don't feel I can quantify these effects even at a level to determine whether they are significant.

Usual gut feeling is the Winter is long and cold and tends to wash out any potential effects on next year's melt season of the weather at this time of year.

46
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 02, 2016, 10:52:49 PM »
That DMI graph is only for >80 degrees N, that is, a 10-degree circle around the North Pole.

The temperature bumps in the graph come from weather patterns that are easily identified from looking at nullschool:
https://earth.nullschool.net/#current/wind/surface/level/overlay=temp/orthographic=-35.44,93.43,1444

The current bump is due to warmer southerly winds heading into the 10-degree circle from Svalbard and through the Fram Strait. The nullschool screenshot has has already been posted above at #482
http://forum.arctic-sea-ice.net/index.php/topic,1611.msg92869.html#msg92869

Nullschool also displays the current temperatures in, e.g., the Beaufort-, Chukchi and ESS seas.

47
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 02, 2016, 07:16:06 AM »
Agree, Tigertown, that it is vitally important to deploy more buoys &/or robot divers to better characterise the air, ice, snow and water parameters throughout the Arctic Basin.


This topic has been discussed in some detail on the "What the Buoys are Telling" thread, beginning with http://forum.arctic-sea-ice.net/index.php/topic,327.msg90613.html#msg90613 (#1184).

See, in particular,
http://forum.arctic-sea-ice.net/index.php/topic,327.msg90678.html#msg90678 (#1194 - on the Argo program you refer to).


Yes, a large-scale program such as this should definitely be implemented by next year's melt season!

Is there anyone on here who can assist in making this happen?  :)

Anyone in the Argo collaboration who knows of Argo's Arctic plans? Can push for more monitoring there?

48
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 02, 2016, 04:14:57 AM »
From Neven's comparison page, https://sites.google.com/site/arcticseaicegraphs/concentration-maps/sic1101, this year has a lot more blue water on the Pacific side of the Arctic Basin than on any other 01 November in the satellite record:

49
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 01, 2016, 09:38:10 AM »
Agree, jdallen.

Another factor - as pointed out by A-Team in his terrific post - is the cloud cover minimizes the radiative heat loss from the ocean surface into space, which would presumably otherwise be the dominant heat loss mechanism at this time of year.

  On the Pacific side of the Arctic basin, that weather pattern is forecast to continue at least for the next few days, though with weakening winds.

  On the Atlantic side, the forecast is for the high pressure system that is currently on the Arctic side of Greenland to drift southwards. I'm guessing that will bring clear skies to help cool the water near the ice pack edge and so allow the ice pack to expand somewhat more quickly on the Atlantic side. There are lots of unknowns though - at least to me - in the relative importance of the various heat flows and reservoirs - and there appears to be a lot more heat this year than usual in the surface water near the Atlantic sea ice edge - so we will see what happens.

50
Arctic sea ice / Re: The 2016/2017 freezing season
« on: October 29, 2016, 10:05:53 PM »
The building storm is pulling lots of warm moist air into the Arctic basin.

With long reaches of ~60 km/h winds, there will be some waves as well.

Current NullSchool...

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