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Messages - slow wing

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1
Arctic sea ice / Re: "Stupid" Questions :o
« on: August 10, 2019, 12:23:40 AM »
Uniquorn, the formulae for orthographic projection are here:
https://en.wikipedia.org/wiki/Orthographic_projection_in_cartography

They are taken from a book for which the .pdf file is available online: https://ia802909.us.archive.org/34/items/Snyder1987MapProjectionsAWorkingManual/Snyder%201994%20Map_Projections_a_Working_Manual.pdf

They are actually simple though, and simplify still further when centred on the North Pole.
phi_0 = 90 degrees
lambda_0 = -45 degrees (example with 'Greenland down')

x = R cos(phi)sin(lambda+45)
y = -R cos(phi)cos(lambda+45)

R ~ size scale of your map. You will presumably have to calibrate it using known coordinates, e.g. Svalbard.

2
Arctic sea ice / Re: The 2019 melting season
« on: August 08, 2019, 05:46:29 AM »
7 August is another date where Neven has a year-to-year comparison of the U. Bremen AMSR2 sea ice concentration maps.

See figure below. The latest 2019 map is bottom right. It can be compared by eye to some of the previous worst years for sea ice minimum extent. Other recent years are available for comparison on the web page.

2019 looks worse to me on this date than any of the previous years other than 2012 and 2007. (2016 caught up later in the month - see the web page.) Even so, it's still to be determined how much of this year's lowered-concentration regions -- particularly in the Laptev sector, and north of the CAA -- will melt out by the minimum.

3
Arctic sea ice / Re: The 2019 melting season
« on: August 04, 2019, 09:11:51 AM »
The heat can mostly move through conduction
You mean convection I assume?
Nope. Conduction.  No convection through the halocline unless wave action stirs things up.

Very little heat moves up through conduction - the thermal conductivity of seawater is just too poor.


I just did a quantitative calculation of that here on the Stupid Questions thread. The amount of heat reaching the ice will seldom be enough to melt more than of order 1 millimeter of ice in a year.

4
Arctic sea ice / Re: "Stupid" Questions :o
« on: August 04, 2019, 05:56:11 AM »
Q. Can it? My response to this statement on the 2019 Melting Thread.

There is more than enough heat in the deep water to melt the ice and keep the arctic ice free year round. 

However, the heat can not move upwards through the halocline. 

The halocline is 50 meters thick (at least) and is very difficult to breach.  If it ever happens, look out!   The arctic will be a completely different place.


I've often wondered if/why the thermal conductivity of seawater is insufficient for significant melting of the ice just by thermal conduction, when the halocline is stable.

So let's see...


Consider the year-round loss of ice thickness due to thermal conduction from a 1-degree-C-warmer layer at a 50 meter depth.


ASSUMPTIONS & PROPERTIES:




CALCULATIONS:

Upwards heat flux = (temperature gradient) x (thermal conductivity) = 2e-2 K/m x 0.6W/mK = 1.2e-2 W/m^2

Thermal energy added to ice in 1 year = (Upwards heat flux) x (time in 1 year) = 1.2e-2 W/m^2  x 3.1e7 s = 3.7e5 J/m^2; multiply by 1e-4 m^2/cm^2 = 37 J/cm^2

Depth of ice melted = thermal energy added / (heat of melting x density)
= 37 J/cm^2 / (334 J/g x 0.9 g/cm^3) = 0.12 cm depth



CONCLUSIONS

So the thickness of ice melted over a year in the above scenario is only of order a millimeter.

Indeed, the thermal conductivity of seawater is insufficient to provide significant melting from deep layers of warmer, saltier water below the ice.

5
For now I'm sticking with last month's estimate: "Between 3.25 and 3.75 million km^2".

I'll keep watching and may exercise my discretion to change it before the poll closes.


July has been at least average and arguably a bit worse than that for the ice. No major storms or events but usually some wind and sometimes a fair bit of sun.

The reference area I always use to compare to is the 80N circle, which encloses an area of about 3.9 million km^2. So I'm guessing the ice extent will end up a little lower than that.


If 'no surprises' then it would probably end up at around 3.8 million but any surprises are likely to push it lower.


Considering the areas where there is currently ice south of 80N:

->  the Pacific side has already almost melted out - more so for this date than happened in any other year besides 2007;

-> The usual 'Beaufort tail' in front of the west CAA will presumably melt away to a large degree as the ice there is already broken up and there appears to be plenty of heat in the water in that region;

-> Yes, the CAA will retain some ice, but it will only be a couple of hundred thousand km^2. To balance that, the Greenland Sea is looking to end barer than in some years, including the record year 2012.


As for the ice detachment from the CAA, the degree to which that has happened is unprecedented in the years of the satellite record. I still expect the pack to drift back to the land before the extent minimum, but it might not. Also, that ice sanctuary has probably seen more heat than any previous year in the record, so some extent will be nibbled away there.


In addition to the possibility of a strong storm anywhere over the ice pack, I look to the Atlantic side for potential 'surprises' even if there is no such storm. The ice there has held on so far, but what about the claimed 'Atlantification' of the water there within the past couple of years? (More salinity and heat.) The Navy thickness map estimate shown below (for 2019-08-09) has relatively thin ice north of Svalbard and the Fram Strait. As we have seen on the Atlantic ice front in some previous years, some of that ice above the shelf of shallower water might disappear fast due to any heat in the water.

The Laptev sector may also get eaten away to well inside 80N.


So here is my guessed boundary, to be compared by eye with the 3.9 million km^2 enclosed by the 80N line. Again, it looks like "Between 3.25 and 3.75 million km^2".


So guessing a second place finish for low extent, behind only 2012. Guessing a record low volume, beating even 2012.

6
Arctic sea ice / Re: The 2019 melting season
« on: July 31, 2019, 03:41:39 AM »
Given the accuracy of past Slater projections to minimum, a record should not happen this year, but I don't think a Slater projection for 2012 is available.

Slater's prediction for 2012 can be seen at http://cires1.colorado.edu/~aslater/SEAICE/Slater_AGU_2013_poster.pdf.


His model did successfully predict a record low extent minimum 2012, but not as low as reality. The predicted 2012 minimum was just a bit under 4 million km2 - which is also what the Slater model predicts for this year.

Given its similar predictions for the extent minima in the record year 2012 and in 2019, the Slater model can't be said to rule out a new record low extent this year.

7
Arctic sea ice / Re: The 2019 melting season
« on: July 25, 2019, 07:29:23 AM »
it seems that the heat at / near the surface will determine the melt, not the heat 1,000 feet up.

It's a fair question. The short answer is that the air near the surface holds hardly any heat energy because it's a gas and so it contains hardly any mass per unit volume.



In more detail, these 3 points are relevant:

1) If we are just looking at the air temperature then we are ignoring water vapor, which can be important. (The dew point shows how much water vapor is in the air.) But now considering just dry air...

2) The temperature at 2 meters is not representative of the amount of heat in the air column as it is somewhat tied to the ~0 degrees temperature just below it.

3) The (dry) air in the meters just above the ice is carrying very little energy and so can melt only a negligible depth of ice. To get significant melt, a significant fraction of the heat in the air column has to be transported somehow into melting the ice (water vapor, infrared radiation, convection...)




To illustrate point 3, consider how much warm air would be required to melt, e.g., a 1 cm thickness of ice.

 (We assume some quasi-static conditions where the air column above the ice causes the melt directly below it - with the caveat that this is not normally a very good assumption.)


To melt, e.g.,  a 1 cm depth of ice requires (334 J/g specific heat of melt) x 0.9 g/cm^3 = 300 J/cm^2.

So 300 J would need to be supplied by the air column above each square cm of ice.

But the specific heat of air is only 1 J/g.(degree C) and the mass of air in the entire column all the way up into space is only about 1000 g/cm^2 (i.e one atmosphere) What average loss of air temperature, dT_air, would be needed to supply the 300 J/cm^2 to melt a 1 cm thickness of ice?

Require:

dT_air[Celsius] x 1.0 J/g.[degree C] x 1000 g/cm^2 = 300 J/cm^2

=> dT_air = 0.3 degrees C.


So THE ENTIRE COLUMN OF AIR UP INTO SPACE would need to lose 0.3 degrees C to melt a 1 cm depth of ice. Obviously, the air just directly above the ice can't melt much ice at all.

8
Arctic sea ice / Re: The 2019 melting season
« on: July 18, 2019, 05:25:55 AM »
My condolences Neven.


Last week (July 10-16), 3-day lagging median.

Click to animate.

Much appreciating the fine graphics displays made by the scientific community and very nicely presented on this forum. They give some of the best insights into what is going on in the Arctic.

Adding in July 17 reinforces that the Pacific-side sea ice is already collapsing to well inside the 75N latitude line.

9
Arctic sea ice / Re: The 2019 melting season
« on: July 13, 2019, 09:55:09 AM »
In discussing the rate of melting, it's good to always bear in mind that it is not accurately measured by the day-by-day extent drop.

A big low pressure system is the dominant feature in the Arctic Basin at the moment, as shown below. The counter-clockwise winds cause dispersion -- 'spreading out' -- which in turn tends to increase the extent even though no new ice is being formed.

That may be one reason for the lower extent drops over the past couple of days -- the ice melting is being partly counteracted by the spreading of the ice. However, dispersion is generally bad for the health of the ice because it creates gaps in the ice that the sun can heat up and, also, the movement of the ice through the water exposes it more to whatever heat is in the water.

So at the moment the melting will tend to be worse than is represented by the daily measured extent drops.

10
Missed the cut but would have gone "Between 3.25 and 3.75 million km^2".

That's dropping down 2 bins from my prediction last month, after a month's brutal weather for the ice.

That agrees with my eyeballing of the Navy ice thickness prediction. Like last month, I drew a boundary line partitioning the ice pack at, for this month 0.7-0.8 metres thickness (last month was 1.3 m thickness) - depending on how close the line is to the edge of the ice pack.

Like last month, on comparing by eye with the area inside 80 degrees latitude -- which is 3.9 million km^2 -- the enclosed area is a little less: about 3.5 million km^2 of ice, including a couple of 100,000 km^2 in the CAA.

So that confirms the bin I'm predicting as "Between 3.25 and 3.75 million km^2".

11
Arctic sea ice / Re: The 2019 melting season
« on: June 28, 2019, 02:25:18 PM »
Some of the people knocking the Slater map may not understand it?

I'm a big fan of it - it's a great approach to predicting future extent. I appreciate what Dr Slater did and also appreciate those who have continued to maintain it since his untimely passing.

I look at it every day when it updates; it gives an indication of where the ice is vulnerable in the coming weeks.

It can also be compared with thickness plots, such as this US Navy prediction for 4 July. (Unfortunately, they use different orientation conventions, so you have to mentally rotate one or the other by 45 degrees.)

Of course we always bear in mind that these are all imperfect models, and we are even aware of some of the shortcomings:

So there is a survival probability for each ice concentration, but we know, that 70% ice concentration is sure to melt out in the Barents, but not so sure to melt out in the CAB.

... Nonetheless, this is a very nice tool.

However, I agree with El Cid that they're valuable all the same in visualizing what is going on with the Arctic ice.

12
Arctic sea ice / Re: The 2019 melting season
« on: June 27, 2019, 08:56:12 AM »
The discoloration of ice in early summer in the Chukchi is an annual thing, I've posted about it previously and nobody seems to have an explanation. Sometimes the discoloration is striated, i.e. there are bands of different colors following the edge of the ice...

Growth of algae, mostly on the undersurface of the ice, may well be the cause of dirty ice you have been seeing each year in early summer in the Chukchi Sea.

The photo -- and others in the article -- are from June 2009 in the Chukchi.

"This was not dirt, but massive blooms of sea ice algae, such as the aptly named ice diatom Nitzschia frigida."

The algae grow when the ice is just thin enough for the sunlight to penetrate.

The author, Dr. Bruce Marcot, speculates that warming of the Arctic may lead to more of this algae growth, potentially enhancing the melting of the ice.

13
Arctic sea ice / Re: The 2019 melting season
« on: June 26, 2019, 06:22:37 AM »
2019 is certainly still in the running for a top 2 finish (+/- 1), with the two main reasons besides the relentless weather:
Low area inside the Inner Basin (courtesy of Wipneus).
Extreme export into the Atlantic throughout the season, which has taken a lot of the MYI - shown in lighter shades on Ascat - out of the basin (courtesy of A-Team in the Test Space thread). The FYI has now reached the North Pole.
[link to post]

Thanks A-Team, and to Oren for posting it in this thread.

That is impressive differentiation between MYI and FYI in the ASCAT gif!

A-Team has posted in the Test space thread that ASCAT uses microwaves: "a real aperture active radar operating at 5.3 GHz (5.7 cm wavelength)".

That Test space post also refers to the other microwave data we are looking at regularly here: "SMOS, a passive radar operating at 1.3 GHz (21 cm wavelength)".

A-Team has also been reading the SMOS literature and reports:

"SMOS is not a melt pond tool. If it were, they would be shouting hooray. Elsewhere, over land, it measure moisture in soil. It does not measure moisture per se in ice/snow/re-frozen melt. At 21 cm wavelength, it is greatly affected by an assortment of surface properties, most but not all salinity-related."

  So, referring that back to the ASCAT gif, given that SMOS and ASCAT are both microwave measurements -- albeit with significant differences -- may I ask this: does the good ASCAT differentiation between (lighter) MYI and (darker) FYI come from picking up the characteristic differences in ice thickness, or does it instead come from the characteristic differences in ice salinity, or even something else?

Asked briefly: is that gif showing ice thickness or, instead, ice salinity?

14
Arctic sea ice / Re: Arctic Image of the Day
« on: June 18, 2019, 11:20:44 PM »
Found on Reddit, not sure if the Arctic. Edit: of course not Arctic, there are trees!

But it's freaking awesome...

It might be Lake Baikal. Similar amazing photos here, here, and here.

15
Arctic sea ice / Re: The 2019 melting season
« on: June 18, 2019, 11:15:11 PM »
SMOS is showing a record low dry ice area for 16 June.

Where does the BEIGE pixel chart update?
The links are both there.

All the SMOS maps are here. The page updates daily by adding the new daily maps at the bottom - so you have to scroll to the bottom. The specific map I post is [date]_hvnorth_rfi_l1c.png

Steven's graph is here. It, also, updates daily and the updating appears to be automated as it seems to update as soon as the SMOS map appears.

The daily updates may be at ~07:00 UTC, but I might be wrong on that.

16
Arctic sea ice / Re: The 2019 melting season
« on: June 17, 2019, 09:05:11 AM »
SMOS is showing a record low dry ice area for 16 June.

17
Arctic sea ice / Re: The 2019 melting season
« on: June 16, 2019, 09:19:33 AM »
25cm loss in thickness in 1 day in some areas.

That's not what these maps are showing. Don't use them for thickness during summer. They say something about how wet the ice is, roughly. That's it.

Why does any credible organization put out a map with a legend for ice thickness that reveals something else?


Is this basically a misleading garbage map?

No, it's valuable measurements made in a frequency range - microwaves - that is unique and providing an orthogonal view of the ice to all the other satellite measurements.

That scale is correct for the Winter months. University of Bremen have been kind enough to continue sharing the map even over the summer months where their calibration is not valid but where the map is perhaps the best single resource we have for quantifying the amount of melt ponding and wet sea ice.

18
Arctic sea ice / Re: The 2019 melting season
« on: June 16, 2019, 09:13:52 AM »
According to the SMOS maps -- which show satellite microwave measurements, displayed on a map of the Arctic by University of Bremen -- 15 June 2019, just released, may have had the smallest area of 'dry' Arctic sea ice on record for the date, going back to 2010 and just pipping the exceptional melt year, 2012.

That's according to the 'beige pixel count' graph by Steven.

EDIT: as Neven has just pointed out in such a timely and informative manner..  :D

19
Arctic sea ice / Re: The 2019 melting season
« on: June 15, 2019, 01:59:52 PM »
SMOS (satellite microwave measurements) beige pixel count on the University of Bremen maps has just dropped to second lowest in the years from with data, beginning from 2010, on the latest date for which the Bremen SMOS map is now available: 14 June 2019.

That ranking is according to the very useful graph that Steven puts out.


The beige pixel count provides a measurement of the area of Arctic sea ice that has NOT yet been wetted by (mainly) melt ponds, and that is therefore still reflecting most of any direct sunlight rather than absorbing it as heat.

So a lower beige pixel count corresponds to more of what Neven calls 'melting momentum'.


For 14 June, this year, 2019, is still well above the anomalous year 2012 and is just below the 3rd lowest year, which is 2016.

A large part of the reason for the drop into second place is the notable appearance of non-beige pixels on the Canadian+Greenland side of the Arctic sea ice on 14 June 2019, indicating the onset of significant surface melting there.

20
Arctic sea ice / Re: The 2019 melting season
« on: June 13, 2019, 10:35:53 AM »
Click on the .gif to see an SMOS (satellite microwave measurements) map comparison for the 12 June on 2010 through this year, which is all the years in the database.

I find it easiest just to eyeball and compare the sizes of the beige area for each year, which tends to represent ice without a noticeable layer of surface water.

The size of this year's beige area is seen to be still 'within the pack' - with 2012, the year that still holds the record for lowest extent at the end of the melt season - standing out as having much less beige area than all the other years on this date, 12 June.

How much was that a coincidence for 2012; how much was it causal?  :P

21
Arctic sea ice / Re: The 2019 melting season
« on: June 12, 2019, 11:51:48 PM »
The entire Asian sector is actively collapsing. This is a catastrophe.

No it's not. (Thanks Pagophilus for pointing this out.) The SMOS microwave maps must be interpreted with caution during the melt season.

I always post this when I post them...

These images are sensitive to melt ponds.
IGNORE THE COLOR LEGEND'S NUMERICAL SCALE & LABEL (the color order progression should be valid though) - DURING THE MELT SEASON THESE ARE NOT LEGITIMATE THICKNESS MEASUREMENTS. Instead, my understanding is that any color other than beige indicates ice that is:
a) thin, ~<50 cm; &/or
b) has concentration well below 100%; &/or
c) has surface liquid water.
In particular, colours other than beige in the ice pack interior are likely to indicate the presence of surface water.


According to the SMOS maps, this year is only in the middle of the pack for the years beginning with 2010, or at least it was on 10 June.


Steven, looking forward to any updates of your very informative plot.


Meanwhile, a direct comparison of SMOS maps for this date can be made by looking at the archive here: https://seaice.uni-bremen.de/data/smos/png/.

22
Arctic sea ice / Re: September predictions challenge 2019
« on: June 12, 2019, 05:23:46 AM »
June

JAXA: 3.75 to 4.25, medium
NSIDC: 4.00 to 4.50, medium

23
Arctic sea ice / Re: The 2019 melting season
« on: June 10, 2019, 08:19:10 AM »
Thanks ReverendMilkbone, the Mt Sinabung eruption is interesting.

It turns out that this might be expected to have only a negligible effect on the climate though. I base that on this tweet from volcanologist Simon Carn, reporting that only 11 kT of released SO2 has been detected: https://twitter.com/simoncarn/status/1137833523191066624

For comparison, the 1991 Mt Pinatubo released about 20 MT of SO2, so ~2000x times as much. That cooled global temperatures by about 0.4 degrees C, for about 2 years.
https://en.wikipedia.org/wiki/Mount_Pinatubo#Global_environmental_effects

There may be other factors in play but I presume that this eruption should have effects around 3 orders of magnitude down on that from the Pinatubo eruption, so negligible.


As Wallen has just indicated, volcanic ash - whether blocking the sunlight or darkening the Arctic ice - is a separate issue. Mt Sinabung is in Sumatra, Indonesia, so a long way from the Arctic.

24
Arctic sea ice / Re: The 2019 melting season
« on: June 08, 2019, 09:34:27 AM »
Imo it's premature to be surprised about the small fraction of ice surface showing melt ponds.

Attached is a gif of SMOS microwave images for each year from 2010 through 2019.

Specifically, the images are yyyy0607_hvnorth_rfi_l1c.png, where yyyy is the year, obtained from https://seaice.uni-bremen.de/data/smos/png/.

These images are sensitive to melt ponds.
IGNORE THE COLOR LEGEND'S NUMERICAL SCALE & LABEL (the color order progression should be valid though) - DURING THE MELT SEASON THESE ARE NOT LEGITIMATE THICKNESS MEASUREMENTS. Instead, my understanding is that any color other than beige indicates ice that is:
a) thin, ~<50 cm; &/or
b) has concentration well below 100%; &/or
c) has surface liquid water.
In particular, colours other than beige in the ice pack interior are likely to indicate the presence of surface water.

& it is seen that only 4 of the 10 years have extensive melt ponding in the Arctic Basin on 7 June: 2012, 15, 16, and 18.

All of 2010, 11, 13, 14, 17, and now 2019, don't have extensive melt ponding by 7 June.

So the comparisons above with 2012 are not particularly surprising, given that 2012 is one of the 4 years in the data record that has extensive melt ponding on 7 June, while 5 of the 9 previous years on record are similar to 2019 in not displaying extensive melt ponds by 7 June.


P.S. Given the weather forecast, I expect SMOS to show extensive melt ponding, especially on the Russian side, within the next few days.

25
Arctic sea ice / Re: AMSR2 Snow & Ice Volume/Thickness
« on: June 02, 2019, 02:18:27 AM »
Thanks Tealight! Great stuff and very much appreciated!  :)

26
Arctic sea ice / Re: The 2019 melting season
« on: May 31, 2019, 02:07:37 AM »
2019 vs. 2012 on this date, using SMOS microwave data

Probing with microwaves can help to compare current sea ice state with how it was at the same date but 7 years ago, in 2012 - which ended the melt season with the record low extent to date.

Caveat:
IGNORE THE COLOR LEGEND'S NUMERICAL SCALE & LABEL (the color order progression should be valid though) - DURING THE MELT SEASON THESE ARE NOT LEGITIMATE THICKNESS MEASUREMENTS.

Instead, my understanding is that any color other than beige indicates ice that is:
a) thin, ~<50 cm; &/or
b) has concentration well below 100%; &/or
c) has surface liquid water.

The comparison for 29 May:

1) on the Atlantic side, 2012 looks much worse than 2019. The ice edge in 2012 has a much larger fringe inside that is wet &/or thin;

2) extending around to the Laptev Sea, 2012 is also worse;

3) In the Beaufort, both years are bad for the date but 2019 is worse;

4) At the Bering Sea and southwards (Chukchi Sea) 2019 is much worse than 2012, with the ice edge much further in.


In summary, 2012 is worse over the Atlantic half (perhaps the main takeaway here from looking at the SMOS data), but 2019 is worse over the Pacific half.


Also, neither 2012 nor 2019 has significant surface water in the ice interior. In 2012, this arrived and progressed within the next few days and weeks. Given the continuing dominance of high air pressure over the CAB -- which brings clear skies and exposes the ice to direct sun -- I expect that to also happen this year.



Click to view the comparison:

27
Arctic sea ice / Re: The 2019 melting season
« on: May 21, 2019, 11:08:00 AM »
Apologies for commenting on the above off-topic discussion, Neven, but imho important to clear up the false information on this thread that melt-out of the Vavilov ice cap would allegedly add 1 foot to sea level = 305 mm.

The volume of the Vavilov ice cap is 570 km^3
Ref. Massive destabilization of an Arctic ice cap, Michael J. Willis et al, Earth and Planetary Science Letters Volume 502, 15 November 2018, Pages 146-155
[This appears to be the study causing all the alarm.]


Total area of the Earth's Oceans is 360 million km^2
The density of ice is ~0.92 of the density of water.

So sea level rise if the Vavilov ice cap melted out entirely = 0.92 x 5.7e2 km^3 / 3.6e8 km^2
= 1.5e-6 km
= 1.5 mm.

So the sea level rise would be 1.5 mm.

28
Arctic sea ice / Re: Latest PIOMAS update (February)
« on: February 12, 2019, 06:28:22 AM »
If someone knows a source with optimum distinguishing colors for a line-style graphic with 20 or so lines...
Wipneus, using the colours in going around a 'colour wheel' provides a partial solution, at least for graphs with up to 12 colours.

Interpolating to intermediate colours in an attempt to increase the number of colours doesn't work as the shades become too difficult to distinguish.

However, you can reasonably double the number of colours by also including a corresponding wheel of darker colours, where the colour values have been reduced in approximate proportion from those in the original colour wheel.

Attached is my suggestion for RGB colour values when doing graphs with up to 24 colours.

29
Arctic sea ice / Re: The 2018/2019 freezing season
« on: October 09, 2018, 09:45:56 PM »
U. Hamburg has stopped updating their daily false colour ice concentration maps, so I have been unable to make and post the gifs showing changes through the week. Presuming the satellite coverage is not good enough to make them now, moving into the dark season.

Currently 59 mb of MSLP difference Across the Arctic Basin, with a 968 storm towards the Atlantic side and 1027 mb on the Pacific side. So it will be quite windy at the moment.

30
Arctic sea ice / Re: The 2018/2019 freezing season
« on: October 04, 2018, 06:52:58 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-10-03...

31
Arctic sea ice / Re: The 2018/2019 freezing season
« on: October 03, 2018, 06:53:43 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-10-02...

32
Arctic sea ice / Re: The 2018/2019 freezing season
« on: September 28, 2018, 11:15:31 AM »
0z EURO says this thread is fake news and the melt season is far from over. DMI confirms imminent rapid Laptev retreat and very substantial front movement elsewhere as well.

Fake news!!!
<snip>

Agree it's at least possible.

Most of the extent gain appears to have come from some of the slush regions on the Pacific side - more specifically, north of the Bering & Chukchi seas - that is now registering as ice.

It hasn't even been that cold there - just -3 or -4 degrees C - nor that still. If the wind picks up there then much of that new ice could flash back to registering as sea and the extent could potentially drop again. Conceivably even to a new minimum!

Observe the candy floss (cotton candy) that is now registering as partly ice, e.g. around 180 degrees longitude, 77N latitude:

33
Arctic sea ice / Re: The 2018/2019 freezing season
« on: September 27, 2018, 05:45:33 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-26...

34
Arctic sea ice / Re: The 2018/2019 freezing season
« on: September 25, 2018, 06:21:21 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-24...

35
Arctic sea ice / Re: The 2018 melting season
« on: September 22, 2018, 05:40:18 AM »
Interesting to see, even after the equinox, this storm predicted to bring +1.3 degrees C all the way to the North Pole.

Presumably won't be melting much. With storms at this time of year I wonder mostly about the potential effects of waves and mixing of the fresh water layer from the recently melted ice with the more saline water underneath.

It's hard to speculate on the significance without seeing the physical data or even a plausible model. Could there be significant retardation of the refreeze? And even if so, could that have significant consequences for the ice pack at the end of the freeze season? Does retardation necessarily mean thinner ice? And saltier ice so less resistant in the melt season? Or, instead, is more heat radiated out into space before the ice cover arrives and might that lead to thicker ice eventually?

The system is just too complicated and unconstrained by data. As far as I can tell, it evades simple understanding on these questions.

36
Arctic sea ice / Re: The 2018 melting season
« on: September 21, 2018, 05:22:38 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-20...

37
Arctic sea ice / Re: The 2018 melting season
« on: September 17, 2018, 05:12:33 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-16...

38
Arctic sea ice / Re: The 2018 melting season
« on: September 16, 2018, 05:39:50 AM »
Oren, yes, I think it is just the ice winking in and out.

There's a large region of slush around the ESS that must be at the edge of being called ice.

Some musing on measurements & definitions...

Presumably the definitions for extent and area won't be of any fundamental physical significance. Instead, there's an algorithm processing the input data & it has a threshold for whether to include each area element. Whether e.g. a region of wet slush is counted depends on the instruments and on the algorithm in a way that is not physically simple. That's fine, presuming the answer obtained is somewhat reasonable, and the answer is consistently applied for each new day. It then gives a somewhat reasonable measure for how the extent and area are progressing.

In contrast, it should be possible to define volume in a more physical way. For example, it could be defined in proportion to the weight of water (typically ice and snow) that extends above the water level for liquid water. The total volume is then obtained by summing up the weight-per-unit-area over the defined Arctic region. That gives a simple physical understanding. The measured value would of course still be an experimentally extracted approximation to that simple physical definition.

  With this wonderful new satellite they are about to put up, which gives very accurate height measurements, a very simple physical definition would be a sum/integral of the heights above local sea level - then converting to a volume of ice using either a single constant for ice density or else using locally estimated densities after attempting to estimate the ice/snow/melt pond mix.
Again, that's a physically simple approach to measuring the ice volume/mass.


This is not my field though. Is that fair comment? Is that how e.g. the PIOMAS definition of volume is extracted in practice?

39
Arctic sea ice / Re: The 2018 melting season
« on: September 16, 2018, 05:11:50 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-15...

40
Arctic sea ice / Re: The 2018 melting season
« on: September 13, 2018, 06:25:07 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-12...

41
Arctic sea ice / Re: The 2018 melting season
« on: September 12, 2018, 05:18:47 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-11...

42
Arctic sea ice / Re: The 2018 melting season
« on: September 11, 2018, 05:23:06 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-10...

43
Arctic sea ice / Re: The 2018 melting season
« on: September 09, 2018, 07:47:12 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-08...

44
Arctic sea ice / Re: The 2018 melting season
« on: September 08, 2018, 06:09:42 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-07...

45
Arctic sea ice / Re: The 2018 melting season
« on: September 07, 2018, 05:18:46 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-06...

46
Arctic sea ice / Re: The 2018 melting season
« on: September 06, 2018, 07:07:08 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-05...

47
Arctic sea ice / Re: The 2018 melting season
« on: September 04, 2018, 06:49:54 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-03...

48
Arctic sea ice / Re: The 2018 melting season
« on: August 30, 2018, 05:19:35 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-08-29...

49
Arctic sea ice / Re: The 2018 melting season
« on: August 29, 2018, 05:53:30 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-08-28...

50
Arctic sea ice / Re: The 2018 melting season
« on: August 28, 2018, 05:24:01 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-08-27...

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