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Michael Hauber

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Re: The 2018 melting season
« Reply #3350 on: September 13, 2018, 03:31:24 AM »
I've had a look at the area I thought may have been new ice a few days ago.  Hard to tell due to cloudiness, but it seems that the area filled with ice over the last few days, but it is large floes clearly not newly formed, and there is no sign of fresh thin ice between the floes.  If any new ice had formed I think it melted again.

Having a bit more of a hunt around today I'm reasonably confident that I've found a large crack north of Ellesmere Island that has partially filled with freshly frozen new ice.  here.

Freezing season has begun, although I'd say there is still far more melting than freezing at this moment.
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slow wing

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Re: The 2018 melting season
« Reply #3351 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...

oren

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Re: The 2018 melting season
« Reply #3352 on: September 13, 2018, 06:46:55 AM »
Freezing season has begun, although I'd say there is still far more melting than freezing at this moment.
I think now comes into play the high compactness of this year's ice around the pole, making it less susceptible to early refreeze, similar to 2012 and very different from the situation in Sep 2016. So while the ESS  and the Chukchi-facing CAB continue melting, a significant extent increase due to refreeze could be delayed for some days. An interesting race against time.

Wherestheice

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binntho

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Re: The 2018 melting season
« Reply #3354 on: September 13, 2018, 08:35:19 AM »
https://www.cbc.ca/news/canada/north/dust-arctic-warming-satellites-1.4819753

Interesting article, reminded me of this one (Beyond Milankovich) which makes a fairly good case for an increase in dust being the secondary trigger that causes interglacials (yes, Milankovich also of course, but insolation peaks do not always cause interglacials).

The article is on Judith Curry's website, and I'm not sure if everybody here is very fond of her, and I'm not sure if the author is a fully qualified scientist, but the case made seems quite strong.

Although whether the dust is now increasing over the arctic, or whether this hypothetical increase will make any significant difference, is beyond my ken.
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oren

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Re: The 2018 melting season
« Reply #3355 on: September 13, 2018, 08:36:52 AM »
May I remind that not everything ice-related belongs in the melting season thread...

Niall Dollard

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Re: The 2018 melting season
« Reply #3356 on: September 13, 2018, 11:24:05 AM »
I've had a look at the area I thought may have been new ice a few days ago.  Hard to tell due to cloudiness, but it seems that the area filled with ice over the last few days, but it is large floes clearly not newly formed, and there is no sign of fresh thin ice between the floes.  If any new ice had formed I think it melted again.


Freezing season has begun, although I'd say there is still far more melting than freezing at this moment.

Yes there are plenty of examples now of freezing. Here is one from the north of Greenland. A few days ago a large block moved westwards from the coast. As it separated, much of the area between has re-frozen.

Images also from sentinel showing the stages of freezing. 9th, 10th and 12th

johnm33

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Re: The 2018 melting season
« Reply #3357 on: September 13, 2018, 03:24:42 PM »
The ice seems surprisingly more mobile than previous years, perhaps these posts of W.D. explain it.
http://eh2r.blogspot.com/2018/09/late-season-melting-examples.html
http://eh2r.blogspot.com/2018/09/differing-resolutions-confusions.html
ice being separated from the pack to melt out, and the drawback of the 15% rule giving 100% readings when the generality is way below that.

uniquorn

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Re: The 2018 melting season
« Reply #3358 on: September 13, 2018, 04:02:32 PM »
Today's ecmwf waves and temps from windy

Niall Dollard

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Re: The 2018 melting season
« Reply #3359 on: September 13, 2018, 11:37:23 PM »
Sentinel image today of the remaining bits of ice in the ESS nearest the Russian Coast. The land area to the SE of the image is Ayon, which is at the left entrance to the large Chaunaskaya Bay.

The ice bits are close to 25km or so from the land. Large tracts of the ESS are like this. I wonder would any of this make the NSIDC 15% ice extent threshold ?   

slow wing

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Re: The 2018 melting season
« Reply #3360 on: September 14, 2018, 05:22:16 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-13...

Aluminium

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Re: The 2018 melting season
« Reply #3361 on: September 14, 2018, 07:37:00 AM »
September 9-13.

jdallen

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Re: The 2018 melting season
« Reply #3362 on: September 14, 2018, 09:46:11 AM »
Sentinel image today of the remaining bits of ice in the ESS nearest the Russian Coast. The land area to the SE of the image is Ayon, which is at the left entrance to the large Chaunaskaya Bay.

The ice bits are close to 25km or so from the land. Large tracts of the ESS are like this. I wonder would any of this make the NSIDC 15% ice extent threshold ?
Its been pretty amazing to watch.  All the extent within that rather diaphanous area of ice would be considered "ice covered".  That said, i'd be surprised if there was much more than 15% coverage across it.  I wonder how much of the current extent looks like that?
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uniquorn

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Re: The 2018 melting season
« Reply #3363 on: September 14, 2018, 02:20:43 PM »
There is less interference recently on ascat over cooler areas. Here is the 'CAA sieve' trying to unclog itself, aug27-sep13. (3MB)

Today's ecmwf waves and temps from windy.

Shared Humanity

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Re: The 2018 melting season
« Reply #3364 on: September 14, 2018, 02:48:08 PM »
Sentinel image today of the remaining bits of ice in the ESS nearest the Russian Coast. The land area to the SE of the image is Ayon, which is at the left entrance to the large Chaunaskaya Bay.

The ice bits are close to 25km or so from the land. Large tracts of the ESS are like this. I wonder would any of this make the NSIDC 15% ice extent threshold ?

If you look at the false color animation, I doubt it.

Sterks

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Re: The 2018 melting season
« Reply #3365 on: September 14, 2018, 02:58:31 PM »
There may be another few days of extent losses given the high that is taking over the pacific side, pulling warmer air from the Pacific, and compacting the remainders of the ESS. The CAA in turn getting much colder.

Ned W

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Re: The 2018 melting season
« Reply #3366 on: September 14, 2018, 03:29:46 PM »
Sentinel image today of the remaining bits of ice in the ESS nearest the Russian Coast. The land area to the SE of the image is Ayon, which is at the left entrance to the large Chaunaskaya Bay.

The ice bits are close to 25km or so from the land. Large tracts of the ESS are like this. I wonder would any of this make the NSIDC 15% ice extent threshold ?

No, in the NSIDC concentration map for 13 September that entire area is 0% concentration.  The "ice edge" of 15% concentration is about 250 km further north.

In the image below, white is "ice" (over 15% concentration).  Blue is under 15%, and actually is 0% for most of this area.  The small dark rectangle at bottom is your Sentinel-2 image.


For comparison, here's the map of extent directly from NSIDC, for the same date:


Its been pretty amazing to watch.  All the extent within that rather diaphanous area of ice would be considered "ice covered". 

Actually, none of the extent within that diaphanous area would be considered "ice covered".  In this case, NSIDC is underestimating the ice concentration, not overestimating it.

slow wing

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Re: The 2018 melting season
« Reply #3367 on: September 15, 2018, 07:30:49 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-14...

oren

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Re: The 2018 melting season
« Reply #3368 on: September 15, 2018, 09:39:18 AM »
Ice in the ESS has reappeared in the last couple of days. Probably it got wet and then dry, clinging at the edge of existence, but could it be refreeze? Can anyone post the temps there? (I am traveling so my sources are limited)

slow wing

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Re: The 2018 melting season
« Reply #3369 on: September 15, 2018, 12:49:18 PM »
Oren, it's around zero degrees and windy in the ESS at the moment and that is predicted to continue over at least the next couple of days. So freeze-up looks unlikely just yet in the ESS.

oren

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Re: The 2018 melting season
« Reply #3370 on: September 15, 2018, 12:50:32 PM »
Thanks slow wing for your response as well as the daily animations. I guess it's just the ice winking in and out.

uniquorn

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Re: The 2018 melting season
« Reply #3371 on: September 15, 2018, 03:40:48 PM »
Some clearer skies over the ice remnants in the Beaufort yesterday allow a rough estimate of sea temperatures there using viirs brightness temperature band15,day on Worldview. These broadly agree with nullschool at~-1.3C yesterday. Does that mean it is quite salty in that open water? Noted that light cloud may influence estimated surface temperature.
edit: added urls.  https://tinyurl.com/yb923unt   and  https://tinyurl.com/y7ww55ga

light blue ~-1.8C
purple ~-1.2
yellow ~-0.6

Todays ecmwf waves and temps from windy.
« Last Edit: September 15, 2018, 03:47:32 PM by uniquorn »

uniquorn

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Re: The 2018 melting season
« Reply #3372 on: September 15, 2018, 10:10:56 PM »
amsr2-uhh, jul3-sep14 put through A-Team's interferometer. There's no mask but Greenland and CAA are defined pretty well by the ice movement. The pole hole is left in for reference.
It appears to show the 'nth Greenland surge' travelling all the way along the CAA and down the Mclure Strait, though it may just be weather effects.

added ascat
« Last Edit: September 16, 2018, 04:55:07 PM by uniquorn »

slow wing

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Re: The 2018 melting season
« Reply #3373 on: September 16, 2018, 03:06:44 AM »
Worldview captured a clear view of the remaining sea ice off the Alaskan coast.

There's not much left of the persistent ice patch that originated from ice piling up against the coast during the freezing season.

Archimid

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Re: The 2018 melting season
« Reply #3374 on: September 16, 2018, 03:12:30 AM »
Stupid question:

Any theories as to why the floating patch of ice remains? Was the piling up creating thicker ice? Was the ice thicker ice exported from the CAB by the gyre? Is it an artifact of the puffing of the middle before the edge?

Will it last until refreeze? Will it trigger very fast refreeze?
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GoSouthYoungins

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Re: The 2018 melting season
« Reply #3375 on: September 16, 2018, 04:42:25 AM »
Will it last until refreeze? Will it trigger very fast refreeze?

Probably not. No.
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slow wing

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Re: The 2018 melting season
« Reply #3376 on: September 16, 2018, 05:10:47 AM »
Any theories as to why the floating patch of ice remains? Was the piling up creating thicker ice?
Yes.

slow wing

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Re: The 2018 melting season
« Reply #3377 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...

slow wing

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Re: The 2018 melting season
« Reply #3378 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?
« Last Edit: September 16, 2018, 07:34:32 AM by slow wing »

oren

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Re: The 2018 melting season
« Reply #3379 on: September 16, 2018, 08:26:22 AM »
I do hope precise height measurements can give a better volume estimate. Re PIOMAS, it is a model not a measurement, though grounded by NSIDC concentration measurement and calibrated to ice thickness measurements.

Aluminium

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Re: The 2018 melting season
« Reply #3380 on: September 16, 2018, 08:35:38 AM »
September 11-15.

gerontocrat

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Re: The 2018 melting season
« Reply #3381 on: September 16, 2018, 01:11:48 PM »
DMI North of 80, DMI SST anomalies, and GFS Arctic Temperature Anomalies all suggest that, if nothing else, re-freeze may be slow, especially on  the Russian side and the Pacific gateway.

ps: Does WACC mean Warm Arctic, Cold CANADA ?
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Dharma Rupa

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Re: The 2018 melting season
« Reply #3382 on: September 16, 2018, 02:41:17 PM »
ps: Does WACC mean Warm Arctic, Cold CANADA ?

I'm pretty sure Siberia will get cold too.

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Re: The 2018 melting season
« Reply #3383 on: September 16, 2018, 03:11:43 PM »
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.


This image is beautiful and demonstrates clearly the limitations of the false color maps in capturing the wondrous nature of the Arctic ice. The field of low concentration fragmented ice dwarfs the area showing up as ice on the false color animation.

Thank you for this.

oren

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Re: The 2018 melting season
« Reply #3384 on: September 16, 2018, 04:14:41 PM »
I get the feeling that a couple more sunny instead of cloudy weeks back around June, and this whole Beaufort/ESS stuff would have been gone already. As it is, the rate of melt and the lateness of the date tell me that is ice will last the season. So 2018 did dodge some kind of bullet.

Phil.

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Re: The 2018 melting season
« Reply #3385 on: September 16, 2018, 06:26:19 PM »
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.


Satellite was launched yesterday I put a link to it on the images page.
Latest info

"NASA’s ICESat-2 spacecraft deployed its four solar panels and is drawing power, indicating it is healthy upon its arrival in orbit. The spacecraft launched on the final flight of the United Launch Alliance Delta II rocket, lifting off from Space Launch Complex-2 at California’s Vandenberg Air Force Base at 6:02 a.m. PDT (9:02 a.m. EDT).

Ground stations in Svalbard, Norway, have acquired signals from the spacecraft. It is performing as expected and orbiting the globe, pole to pole, at 17,069 mph from an average altitude of 290 miles."

Stephan

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Re: The 2018 melting season
« Reply #3386 on: September 16, 2018, 09:31:54 PM »
That is good news. I hope it'll work fine for many years delivering valuable information about the ice in much higher quality than we have been used to. I wonder whether and when we will switch from the actual sources to this ICESat-2 and how this will affect the long-running data sets we all have collected for some decades.
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NeilT

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Re: The 2018 melting season
« Reply #3387 on: September 17, 2018, 12:10:03 AM »
DMI North of 80, DMI SST anomalies, and GFS Arctic Temperature Anomalies all suggest that, if nothing else, re-freeze may be slow, especially on  the Russian side and the Pacific gateway.

As this is the mean temp from 80N to 90N, I would have thought it was mainly to do with the Atlantic side open water and the open water of the Laptev bite which is driving this anomaly.

I would assume that this anomaly will continue, whilst the temperatures also continue to drop, until those areas of open water are, again, under ice.

This is somewhat analogous to the melting of ice keeping the temp ~0C-1C so long as there is ice to melt.  Namely that so long as there is open water to give back heat, this mean will be above the long term average and that it requires that water to be covered with ice again to begin to address it.

Witness the fact that the vast majority of years, post 2005, have anomalously warm re-freeze in the 80N+ mean temp.  Although 2016 and 2017 are outstanding in these anomalies.
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oren

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Re: The 2018 melting season
« Reply #3388 on: September 17, 2018, 12:15:59 AM »
Quote
As this is the mean temp from 80N to 90N, I would have thought it was mainly to do with the Atlantic side open water and the open water of the Laptev bite which is driving this anomaly.
It is not a straight mean, rather it gives the area between 89-90 the same weight as the much larger area between 80-81, IIRC.

Phil.

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Re: The 2018 melting season
« Reply #3389 on: September 17, 2018, 12:41:52 AM »
Quote
As this is the mean temp from 80N to 90N, I would have thought it was mainly to do with the Atlantic side open water and the open water of the Laptev bite which is driving this anomaly.
It is not a straight mean, rather it gives the area between 89-90 the same weight as the much larger area between 80-81, IIRC.

Yes biased towards the pole.  From the DMI website:
"However, since the model is gridded in a regular 0.5 degree grid, the mean temperature values are strongly biased towards the temperature in the most northern part of the Arctic! Therefore, do NOT use this measure as an actual physical mean temperature of the arctic. The 'plus 80 North mean temperature' graphs can be used for comparing one year to an other."

slow wing

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Re: The 2018 melting season
« Reply #3390 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...

uniquorn

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Re: The 2018 melting season
« Reply #3391 on: September 17, 2018, 03:02:05 PM »
Update on Mercator 0m salinity and 0m sea temperature, mar21-sep16, every 4th day.(click to run)
http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20180321/20180916/2/1

Today's ecmwf waves and temps from windy

harpy

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Re: The 2018 melting season
« Reply #3392 on: September 17, 2018, 06:53:12 PM »
How much longer will the arctic circle continue to get sunlight? 

Aluminium

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Re: The 2018 melting season
« Reply #3393 on: September 17, 2018, 07:33:56 PM »
Every day.

harpy

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Re: The 2018 melting season
« Reply #3394 on: September 17, 2018, 07:39:48 PM »
What location does that graph refer to? 

12 hours of sunlight in March?

This is wrong.

ghoti

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Re: The 2018 melting season
« Reply #3395 on: September 17, 2018, 07:42:45 PM »
The Equinox has 12 hour days everywhere.
To quote Google:
Quote
On the equinox, night and day are nearly the same length – 12 hours – all over the world. This is the reason it's called an “equinox”, derived from Latin, meaning “equal night.” However, in reality, equinoxes don't have exactly 12 hours of daylight.

charles_oil

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Re: The 2018 melting season
« Reply #3396 on: September 17, 2018, 07:43:07 PM »
Or if you want to know how solar radiation with latitude changes with date see:


   https://www.itacanet.org/the-sun-as-a-source-of-energy/part-2-solar-energy-reaching-the-earths-surface/


Others have posted similar ones - but as arctic circle is at ca 66deg north - this graph illustrates when incoming energy to the arctic drops to nothing.



Aluminium

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Re: The 2018 melting season
« Reply #3397 on: September 17, 2018, 07:46:32 PM »
What location does that graph refer to? 
66.5°N. Salekhard, for example.

Dharma Rupa

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Re: The 2018 melting season
« Reply #3398 on: September 17, 2018, 08:16:49 PM »
Every day.

That response was mean!  heheheheheh

I suppose that at the Arctic Circle there will be part of the shortest day which is not during the solstice, and therefore will have sunlight.

You being so...um...how far north of the Arctic Circle do you have to be before 1) you have no sunlight at least one day of the year, 2) you have no civil twilight at least one day of the year, and 3) it is dark all year?

charles_oil

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Re: The 2018 melting season
« Reply #3399 on: September 17, 2018, 08:24:25 PM »
Some definitions here:  +/- 6 deg defines "civil" twilight  +/- 6-12 deg for "nautical" & +/- 12-18 deg for "astronomical" so take your pick !


https://www.timeanddate.com/astronomy/different-types-twilight.html