Support the Arctic Sea Ice Forum and Blog

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - Hopen Times

Pages: [1]
1
Arctic sea ice / Re: The 2020 melting season
« on: August 20, 2020, 08:28:32 PM »
Latest tomorrow a few guys and pals here have to read back a few weeks and re-consider their approach/attitude for the years to come, just one more drop like this while I think there will be many ( a few ) more to come.
All please remember that:
* It is ok to be wrong, it doesn't mean one is a denier or evil or stupid.
* A prediction that failed was not necessarily wrong. Random weather plays a big hand in the Arctic, it could be in retrospect that luck was what decided it.
* The season is not over until it is over, premature celebrations of being right can go wrong later.

Personally I've thought since the crazy July that this season had a good shot at records regardless of later weather, but it doesn't mean I don't respect those who thought otherwise, and I recommend all to do the same. (I don't mean the one or two cherry-pickers, I mean those who post in good faith).

2
Arctic sea ice / Re: The 2020 melting season
« on: July 02, 2020, 06:34:20 PM »
In case anyone is interested in an on-the-ground perspective on this year's melting season, I put together a time-lapse video using still images from the observatory's webcam here in Alert.  The video covers 12 days from June 18-30, which includes the record-breaking June high temperature of 18.6°C recorded on the 28th.


3
Arctic sea ice / Re: The 2020 melting season
« on: June 20, 2020, 10:13:57 AM »
There is a large area near Svalbard and in the Fram.  This ice is toast.  Guaranteed to vanish regardless of the sun and temps because its going into the Atlantic.


Atlantic is also going to look like shit before long. Big injection of warmth, Kara temps going up in 24 hours + winds are going to toast that block of ice, severnaya crack getting wedged open. Mosaic team likely going to be sitting in melt ponds. Atlantic CAB could see melt ponds too

I do feel we need some perspective in posts sometimes. "big injection of warmth" - I don't see that, yes there is a southerly flow but it's quite light and we are hardly talking about Siberian heat here, it's a bog standard set up really and one that favours the ice because of the lack of fram export.

I feel unless we get very strong southerlies hitting that area, I expect that ice around Svalbard to last most of the melt season like last year but then potentially start to retreat northwards as it did then as SSTS and winds take over the ice.

4
Arctic sea ice / Re: The 2020 melting season
« on: May 11, 2020, 11:53:30 AM »
The 850 hPa temperature is somewhere away from the ice. I'm not sure of the altitude, maybe someone with more knowledge than me can provide that.

But it is the temperature adjacent to the ice that is going to impact the ice, not the temperature 1,000 feet above sea level. For the benefit of the lurkers who are reading the thread, I think it's useful to kick the tires and questions some assumptions about the magnitude of the current events.

The heat coming into the Chukchi and ESS and the high winds pushing ice through Fram is quite significant and easily understandable and acceptable. No problem.

Maintaining heat over ice for a very long distance over ice and delivering it to the surface of much of the CAB where it can impact the ice in May is a completely differently animal. Skepticism of this is healthy from a scientific perspective.

Surface air temperatures over the ice are held close to a 0C maximum due to the latent heat of fusion of ice. This is quite apparent each year on the DMI 80N temperatures. For that reason, using something like the 850hPa temperature (or the less common, 925hPa value) is useful for assessing the relative heat mass over the ice. It's far from perfect, and temperature inversions, fog and such will add more complications, but much of the time in summer, 850hPa temperatures are more useful than surface temperatures.

5
Arctic sea ice / Re: The 2020 melting season
« on: May 09, 2020, 01:13:18 AM »
Quote
Please note, i am not asking to explain every little detail in this topic. I ask to use non-contradicting terms. Like, instead of "melt ponds confuse sensors" - say, for example, "technology limitations disallow reliable total Arctic ice volume measurement after mid-April based on those sensors". Like, instead of "SMOS stopped" say "SMOS measurements stop being used for calculating total ice volume mid-spring due to growing measurement errors which currently we're unable to remove". Etc.

If we'd be failing to avoid "contradicting per common sense of a non-scientist" statements here - even when such contradictions are in error de-facto - then what exactly this topic is for?
Thank you for the better description of SMOS cutoff for Cryosat, and other SMOS limitations. This is what should have been posted in the first place if you find the original poster was not accurate enough. Clarify, explain, bring more info, make better wording. And do not hint the cutoff is to hide something or that somebody was lying because they used inaccurate terminology.

Back to what this topic is for - bringing information, data, analysis and commentary about the Arctic sea ice melting season that is just beginning in earnest.

6
Arctic sea ice / Re: The 2020 melting season
« on: April 28, 2020, 04:50:24 AM »
The new moderator's long-winded stream-of-consciousness position about this thread is:
* Off-Topic comments, jokes and other "nonsense" are always welcome on the forum in appropriate threads, but not on the melting season thread, one of the highest-rating threads that is home to many lurker readers.
* Personally-charged comments and slights of honor should be avoided (even when justified...), as they necessarily create back and forth posts and increase clutter. And are of course impolite.
* Comments about comments, i.e. meta-discussion, should be minimized. Not necessarily avoided, but reduced and used with care. Use "report to moderator" or PM me about posts that you believe should be dealt with, but be aware that I am monitoring this thread continuously.
* General long term predictions about the season ("I think a BOE is impossible this year") are better off in a separate thread, and I am happy that such a one was recently opened. The exception is extrapolations of current data and situations ("I think the high CAB thickness precludes a meltout, based on average melting patterns").
* Deep discussions about scientific issues, which certainly could impact the melting season, should be held in separate threads. For example, contrails and their effects on sea ice, aerosols or lack thereof, La Nina, the Blob, soot from China or the fires soon to be in Siberia, etc., while a few comments on each such issue are welcome on this thread. Once it becomes heavy and arguments are flying around, or various papers posted, move it elsewhere. Here it will be lost and will disrupt the news flow.
* This thread is mainly about actual developments happening during the melting season, and comparisons with previous melting seasons.
* Comments about the data posted by JCG and Gero in the data thread should be posted in this thread, rather than in the data thread itself.
* Posters wishing to thank others for exceptional contributions (of which we happily have many) should consider using the Like button for most occasions.
* The moderator will use moderation in moderating, so as to avoid creating dissent and hurt feelings, and in consideration of his inexperience in such matters, but will act as necessary to ensure smooth and fruitful discussion.
* Often sporadic or borderline comments will not be dealt with to avoid disruption by the moderator, but similar comments might get the edit later when something becomes a repeated phenomenon.
* Should you undergo a moderation edit, please don't take this as a personal attack or as a hint that your contributions are unwelcome (unless specifically stated.....)
* If you are a lurker and are afraid or hesitant to post because of all these rules, be aware that new posters are treated more gently and are very welcome in their initial posting efforts. Bear in mind there is a "stupid" questions thread where you can ask most anything.

7
Arctic sea ice / Re: Arctic Image of the Day
« on: April 18, 2020, 12:23:30 AM »
The Polar Vortex Looks Happy...

8
Arctic sea ice / Re: Arctic Image of the Day
« on: April 09, 2020, 01:57:00 AM »
Midnight looking north over the frozen harbour at Longyearbyen, Svalbard.

The orange glow shows that it's only 10 days before the sun will be up all day there (April 19th !).

9
Arctic sea ice / Re: Tides
« on: April 08, 2020, 01:39:30 AM »
Tidal currents in the Arctic Ocean are small (< 5 cm/s) and this applies to Fram Strait as well. Furthermore, these tidal currents are largely linear which means that the water going into the Arctic during the "flood" is the same that comes out of the Arctic on the ebb. For linear wave motions the average velocity over a wave period is zero. Sinusoidal (linear) waves do not transport mass or matter such as ice or water, they transport energy. (A tsunami is a very good analogy for this.)

Only if the wave amplitude is similar to the water depth does a wave transport matter and energy. This (nonlinear) process closely relates to wave breaking.

Tides have a negligible effect on the flux of sea ice into or out of Fram Strait.

P.S.: Tidal currents are strong in Nares Strait (~ 1 m/s), but as in Fram Strait the tidal currents move ice back and forth only with a net displacement (during an entire tidal cycle for the tidal current) is close to zero.

10
Arctic sea ice / Re: Tides
« on: April 07, 2020, 10:49:20 AM »
To be honest, I think the effect of tides is cumulative and not necessarily driven by a specific tide. But perhaps a period of higher tides (king tides, spring tides) could have some non-negligible effect, as sometimes happens with iceberg calving.
I don't pretend to know if the effect is strong or very weak, but I am sure it is not zero, which for me was the original debate about tides and ice.

11
Arctic sea ice / Re: Tides
« on: April 07, 2020, 10:45:05 AM »
"If the question is" My suggestion is that tidal forces, which have always operated, are now pushing more A.W. deeper into the Arctic via the Barentz shelf and these surges/pulses are beginning to become detectable. The surges create turbulence and I'm guessing some internal waves as they reach the basins, they force temporary currents some of which persist a while and may become permanent. These temporary currents themselves ease the influx of more A.W. and since the Arctic sea level remains self similar there has to be an increased outflow and it seems to me that this is below the shear level of the water held steady by the chaotic underside of the ice. The surges happen at speed the actual water trails far behind probably best judged by late +temp. anomolies in Kara/Laptev.
The full moon is upon us, and the biggest tides of the year so either the flow will be contained in the Norwegian/Greenland seas and thus halt the outflow or it will penetrate into Barents accelerating outflow. A possible proxy is the anomoly by Svalbard, here the flow of A.W. has moved directly north gaining about 16mph pero relative to its position and moving towards the rotational axis has also gained/lost[?] +/-angular momentum such that if it builds up both forms of kinetic energy will be expressed there as heat, both here and Barentz by the white sea anomolies are rising at the moment. Todays mslp suggests more contained tomorrows suggests not.

12
Arctic sea ice / Re: Tides
« on: April 06, 2020, 11:48:30 AM »
<>Ghanges in gravity cause changes in pressure, which causes the water column to expand and contract. Changes in atmospheric pressure also cause changes in pressure within the water column, causing the water column to expand and contract. Hence the two phenomena are linked, and they are also of a similar magnitude.<>
A bold claim which should be easy to verify with a volume vs time chart or a scientific paper. A quick search didn't find one. Nevertheless, that search did lead me to the video attached, which is similarly challenging. Thank you.



Quote
Although each drop of water on Earth is indeed pulled by the moon's gravity, the effect isn't noticeable on a molecular level since the Earth's inward pull is overpowering.

The key, however, is that ocean water covers about 71% of Earth's surface and is connected as one liquid body. This allows the small force on each water molecule to collectively add up to "a pretty decent increase in water pressure," Perez-Giz says.

Molecules of water near Earth's poles are pulled mostly straight down toward the planet's center of gravity (near its core), and the molecules closest to the moon (at Earth's equator) experience the strongest pull toward the moon. Water molecules that are farthest from the moon, meanwhile, feel the weakest gravitational acceleration.

Since water molecules can easily move and bump into one another, these countless tiny nudges add up and "squeeze" seawater away from the poles. This global water pressure works against Earth's gravity to form two bulges: the high tides.

"The ocean isn't being lifted or stretched," Perez-Giz says. "The ocean is bulging along the Earth-moon line in the same way that a blister or pimple will bulge up if you start to squeeze it from the side."
https://www.nsf.gov/od/oia/activities/aaasfellows/bios/perez-giz.pdf

13
Arctic sea ice / Re: Tides
« on: April 04, 2020, 07:20:36 PM »
     If the question is "Does Fram export vary with tidal forces", then getting the daily values used to create the Wipneus Fram export chart and checking for correlation with the lunar cycle would provide evidence to address the question.
https://forum.arctic-sea-ice.net/index.php/topic,119.msg258236.html#msg258236

14
Antarctica / Re: PIG has calved
« on: April 04, 2020, 04:34:14 PM »
No, it's not to announce that the Cork2 has left the ice shelf...  ;) ;D

It is only to communicate a small observation, really small, but one that may be useful in our future observations:

Today there was a strong SE wind and in the image you can see the ice trails.
But in places protected from the wind we can see ice trails pushed only by the current and therefore having another direction.

15
Arctic sea ice / Re: Tides
« on: April 03, 2020, 04:13:48 PM »
  FWIW - It seems that the two sides in this debate are focused on different questions. 
     
     One side documents that tides affect the Arctic Ocean waters, ice, mixing, temperature gradients etc., and thus condition of the ASI. The other is focusing only on Fram Strait export, and saying the because tidal movement alternates, the movement of water south on an outgoing tide is matched by tidal movement north on the incoming tide, so in terms of Fram Export it has zero net effect.

     Maybe it's time for a real expert to address the original question directly:  Do changes in tidal forces across the lunar cycle influence the net amount of ASI export through the Fram Strait? 

     At least I think that is the question.  I don't know enough to have an opinion, just trying to clarify the discussion.  All I do know is that my friend retired from 30+ year career at National Weather Service said that tidal mathematics is really complicated!

16
Arctic sea ice / Re: Tides
« on: April 02, 2020, 09:16:16 AM »
waves on the ocean are not pressure waves.
Pressure waves travel through the medium not on top of it. Sound is a pressure wave.
The wave motion on a body of water is not a tide. The motion of water on the surface is a displacement wave. The displacement wave moves water up and down but does not move water towards the shore or away from the shore.


waves are a transference of energy not matter. Yes the move the matter locally but not very far and the net affect is not motion.


Tides flow in increasing the local water depth. This is not a wave it is a large increase in the amount of water in a region. It is caused by gravity but it is the moons gravity that causes a bulge in the ocean on the side closest to the moon and a deficit elsewhere.


This disagreement can be summed up as


1.wave does not equal tide


2.wave is movement of energy


3.tide is movement of water.


17
Arctic sea ice / Re: Tides
« on: April 02, 2020, 07:56:04 AM »
Moving on from my last post: Of course, as any pedant can point out, the long-term tidal effects are due to the fluctuating nature of the tides.

But in the large scale of things, these fluctuations have almost no impact per se. It is the cumulative impact that is real, but the impact of indivual tidal movement is purely local and temporal, with any movement being almost exclusively up-and-down and back-and-forth, so the net effect is usually zero.

Some people have the pet ideas that they can somehow predict (or explain) daily, weekly or monthly changes in the large scale behaviour of Arctic sea ice by referring to the phases of the moon. Every such claim is unsubtantiated by both basic science and current scientific research.

18
Arctic sea ice / Re: Tides
« on: April 01, 2020, 02:35:46 PM »

19
Arctic sea ice / Re: The 2020 melting season
« on: March 19, 2020, 08:21:03 PM »
Greetings from Midway Georgia,
 I've been lurking here for years, but after some 26 tears online, this the very 1st forum that I have ever joined.  This is my 5th attempt to make a post, so bear with me as i learn the ropes :)
 I've been alarmed by the huge export through Farm and subsequent melting signified by the foam left over from the melting ice in the GS as illustrated by the attached image.
 Also included in the image of some beautiful cloud vortices.  It's too bad that they overlay a field of death for ice

https://worldview.earthdata.nasa.gov/?v=348385.3212968977,-1205274.273347458,1466593.3212968977,-680986.2733474581&p=arctic&t=2020-03-18-T19%3A13%3A07Z

td

think good thoughts, do good deeds, enjoy good results


20
Arctic sea ice / Re: The 2019/2020 freezing season
« on: February 26, 2020, 03:25:18 PM »
hi.
I live on 60N in Scandinavia and this has been the 'new normal'  winter for a decade at least. Our winters are getting much shorter as a result.

But there is no punch at all in the sun at these latitudes in Feb., and March. It's not gonna bring in "massive extra heat" as you write. In April insolation is strong, but by then snow is mostly gone anyway.

A few remarks:

- you may not feel the punch in cold air-masses and the frequent inversions where the air at ground level and close to it is colder than at some higher altitudes.

- nevertheless the energy that can be measured, even at low sun-angles IS SIGNIFICANT.
. In fact, compared to zero it's even huge while not TOP-Level of course.

- Said energy, meeting darker surfaces, makes a "HUGE" difference. Not only in absorbing
. energy but also by quicker melting of the remaining and/or existing snow cover.

- 60N is slightly north of  Oslo and goes through St. Petersburg to name just 2 of the largeer and
. better known places. That's "NOT" very far north, it's around the northernmost tip of the UK.

Whatever the details, the impact on darker surfaces, compared to white surfaces, is significant at "ANY" sun angle. Even though our thickly dressed protected skin does not feel that way, last but no least due to wind and humidity as 2 of several key factors. More humid air in winter often sticks to the ground with an impact as described above.

There is more to it but then I only wanted to +1 F.T.,
I found his description, in all briefness, kind of spot on.

Thing is that if we write long/much, it's frowned upon. If we write short, those with a tendency to find a hair in every soup would easily find their "angle of attack" while the original meaning
was quite accurate and mostly well meant.


21
Antarctica / Re: PIG has calved
« on: February 25, 2020, 09:57:58 AM »
Just a pretty picture of the cork.

22
Antarctica / Crosson and Dotson Ice Shelves Discussion
« on: February 13, 2020, 07:18:19 PM »
PIIS has pulled all attention in the last weeks, but a few 100 km west another ice shelf had a major calving event.
Between Feb 1 and Feb 11 a part of the Dotson Ice Shelf lost a 25*3 km piece of ice. The days in-between were too cloudy for an evaluation in EOSDIS, so a more exact dating is not possible.

See attached image.

23
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: February 04, 2020, 01:43:49 PM »
In other words, the 17 years with lowest sea ice extent for the date are among the first 20 years of the 21st Century. A clear perspective of long-term trend of global warming, thanks weatherdude.

Take into account that this is all based on data from 1979 and on. There is no real data from before ( there are some very bad satellite pictures from 1975'ish). Before that there is reported anecdotal data from explorers and locals that in some cases point to low arctic ice.

You might want to look at this 1947 report from DMI on the state of the Arctic Sea Ice.

As you probably know, 1947 was at close height of the mid-19th century warm peak. The August extent in the DMI report is of a similar magnitude to what the winter extent is likely to be this year, so between 2 and 3 times more than this decade.

So any anectodal evidence for low sea ice extent from before 1979 will have to be taken with a ton of salt. Or rather, tied to a rock and thrown overboard. Any and all documentation from before 1979 shows greater sea ice extent than what we are seeing this last decade.

This paper from 2001 shows an estimate for the 20th century. August minimum in 1947 would have been around 12 million km2.

And another paper for 2009 seems to agree roughly, taking the estimate back to 1880, which may well have been the maximum sea ice extent since the last ice age.

Having said that, apparently we have to go at least back to around 1200 CE to see extent similar to what we have been seeing in the last decade.

24
Arctic sea ice / Re: Arctic Image of the Day
« on: January 11, 2020, 12:17:47 PM »


Polar stratospheric clouds.

http://www.atoptics.co.uk/fza196.htm

25
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: November 09, 2019, 10:16:49 AM »
JAXA ARCTIC SEA ICE EXTENT :- 8,461,408 km2(November 8, 2019)

- Extent gain on this day 98 k, 39 k more than the average gain of 59 k,
- Extent gain in this freezing season to date is 4,497 k, 99 k (2.2%) MORE than the average gain to date of 4,398 k.
- Extent is 3rd lowest in the satellite record below 2016 (532 k lower) and 2012 (104 k lower),
- Extent is 332k less than 2018
- Extent is 329 k (3.7%)  less than the 2010's average,
- on average 44.7% of extent gain for the the season done, 124 days on average to go.

Projections.

Average remaining extent gain in the last 10 years from this date produces a maximum of 13.89 million km2, above the lowest in the satellite record by 0.02 million km2.
____________________________________________________________
Ice Gain Outlook??

Extent gains show further signs of moderating, though still very much above average

Diminishing +ve SST anomalies.
GFS says Arctic temperature anomalies increasing from  +1.2  to +2.1 celsius over the next 5 days, - basically a tale of 2 halves - Pacific half warm, Atlantic half cold.
 
Or will daily gains ever return to the average or even below?
__________________________________________________

26
Antarctica / Re: Thwaites Glacier Discussion
« on: October 19, 2019, 08:09:34 AM »
A quick update.  I was able to fairly easily (details below) add the grounding lines through late November 2017 (2017.91 in decimal years) as a very faint (30% opacity) overlay.  It's a very busy diagram, but I hope at some point to be able to mask out the extraneous details and increase the opacity.

In general, I was quite surprised at the size of the ground line retreat.  Seeing it laid on top of the satellite images I have grown quite familiar with was a bit of a shock.  Also, at first glance, it would appear that there has been some additional grounding line retreat in the last two years.  In particular, the West side of the "Butterfly" looks like it is no longer grounded, although it should probably be compared to older satellite images to see if it is a new feature or not.

Edit: Added an annotated version.

This is Figure 1(B) from Milillo 2019 "Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica"
https://advances.sciencemag.org/content/5/1/eaau3433

The only way I found to obtain a high resolution image of the figure was to click on the "View this article with LENS" button, then click on "Figures" and click on Figure 1.  I cropped and masked the figure to just get the bathymetry, then rotated it clockwise 70 degrees and scaled it down 4% (0.96 scaling.)  The 1996 grounding lines then lined up quite nicely, yellow in Milillo and Red in Millan.

27
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 19, 2019, 07:23:13 AM »
A GIF showing the freezing of the fjords northwest Greenland, taken from DMI Lincon crop.

The freezing starts around the 17th of September here.

From 06.08, many many frames, big file, click to play.


28
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: September 18, 2019, 04:09:25 AM »
Asking for a friend about analysing ice cores:
"Just wandering if there have been years when it was so warm so the layers of some years now are missing. Would we know that and how would we find the temperature of these years? I mean we would not find the temperatures of 2012 in Greenland ice core 200 years from now. Have there been similar periods in the past?"

Occasional (and ever more frequent) melting events on the high glacier come nowhere near to being able to melt away the previous winter's accumulated snowfall. So 2012's snow is still very much up there.

If summer melting ever manages to melt all the new snow from the top of the Greenland glacier it would be because 1) Temps have gone up tens of degrees Centigrade, or more likely, that ongoing negative ice balance has so reduced the height of the central glacier that it has fallen below the (by then significantly raised) equilibrium line below which all accumulated snow melts.

Once that happens, total disappearance of the ice sheet will be within a few tens of years.

29
Arctic sea ice / Re: The Rammb Slider Thread
« on: September 16, 2019, 10:56:42 PM »
Very pretty tidal wave today in Lincoln at Nares entrance.

Note how it spreads out east and west.

30
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: September 16, 2019, 10:32:49 PM »
So the last melt was 1209, back in the Medieval Warm Spell?

The MWP had more than one greenland surface melt episode:

The extreme melt across the Greenland ice sheet in 2012
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2012GL053611

"From the same core, Alley and Anandakrishnan [1995]studied melt layers from the upper 1565 m of the GISP2 core over a time period of 10,000 years. However, the frequency of melt occurrence varies widely in time as identified by ice layers in ice cores. Prior to the 19th‐century event, another significant melt event occurred about 680 years earlier [Meese et al., 1994] preceded by several events in the Medieval Warm Period (a.k.a. the Medieval Climatic Anomaly). Melt occurred once in about 250 years from 1000 to 4000 BP (referenced to 1950) and once in about 82 years from 5000 BP to 8500 BP according to Alley and Anandakrishnan [1995]. These significant melt events are widely sporadic in different periods of the Holocene, clearly exhibiting their non‐stationary behavior. Thus, a single average value of melt frequency is not necessarily applicable to represent climate change at a given time period in the past, the present, or the future."

Earlier in the paper, the distinctive appearance of melt episodes in the ice core is described.

31
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: September 16, 2019, 09:07:54 PM »
Asking for a friend about analysing ice cores:
"Just wandering if there have been years when it was so warm so the layers of some years now are missing. Would we know that and how would we find the temperature of these years? I mean we would not find the temperatures of 2012 in Greenland ice core 200 years from now. Have there been similar periods in the past?"

Melting events don't just disappear a layer or two of the ice cores, they leave distinctive melt layers.  Thus,

"Furthermore, this melting event on July 30 also sets the record for the preceding century. Prior to 2012, melt layers at summit have been absent since 1889, and only appear again 680 years earlier."

See:
At summit: The highest temperatures in the past 12 years
http://nsidc.org/greenland-today/


32
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: September 16, 2019, 08:56:09 PM »
You can see gaps in the core when you compare it to other cores.

Meaning, you might not see 2012 in a Greenland core, but you see it in a Himalayan or Antarctic core. And then the gap itself becomes a data point. You know this year was a melting year in Greenland but not in Alpine areas for example.

Not a scientist though, just a laymen's explanation.

33
Arctic sea ice / Re: Nullschool Animations
« on: September 14, 2019, 02:11:18 AM »
This is probably better for large file sizes. And I can tweet these...  ;D

34
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: September 11, 2019, 01:47:32 PM »
It has nothing to do with Greenland temperatures!!!!!!!!

I am not sure if the University of Copenhagen agrees with you:

As I understand University of Copenhagen, Greenland ice cores reflects both the temperature in the the areas from which the moisture source originates and the temperature the vapour experienced on its way travelling, over both sea and ice. 

This is not my field, so I am very open for that there is something I am missing here.

You are right, I was way to categorical in my denials above. This is what happens when you think you remember things correctly ("Never trust memory" I was taught in High School, and I usually try not to ...)

And the plot deepens, I found this:

Quote from: https://www.clim-past.net/9/2525/2013/cp-9-2525-2013.pdf
To sum up, all the results derived either from borehole paleothermometry or from isotopic anomalies significantly underestimate temperature changes in central Greenland, thus seriously challenging the conventional isotopic approach.

where the point was that the traditional oxygen isotope approach showed what seemed to be way too large fluctuations, but a closer look showed that they were in fact bigger than they seemed! And amazingly enough, the difference between LGM and present is a full 25 degrees centigrades (but where? At the top of the ice shield it seems)

But I think I can definitely claim the following: This is not what happens to global temperatures, and thus the value of the Greenland cores as a proxy for global changes becomes somewhat doubtful.

So Jim Hunt : I didn't know the answer when I tried the first time, I know even less now!

But back to the original point: Everyone can go and look at graphs of estimated global temperatures between the last glacial and the Holocene and see that the difference on a global scale is around 6 - 8 degrees Centigrade. And according to Greenland ice cores there is a very fast rise at the end of the Younger Dryas / beginning of the Holocene, near vertical at 10 degrees.

But ice cores from Vostok do not show the Younger Dryas event! They show a change in temperatures of perhaps 10 degrees from the LGM at ~26,0000 ky to the the Holocene proper at ~14,000, in two distinct steps, the later of which was pretty steep at 4 degrees in perhaps 1200 years, or a surprisingly rapid 0.3 degrees / century.



Deep sea sediments from the Pacific and Indian oceans (i.e. mid latitude) show a much smaller difference between LMG and Holocene, perhaps as little as 2 or 3 degrees, and no Younger Dryas event.



After some searching I managed to find a paper on a subject that I find quite interesting, i.e. the Holocene temperature conundrum which has a very good graph of the warming at the end of the last ice age:



This graph shows a max difference of 5 degrees and even if it misses out on the LGM, the real warming only began at the ~17,000 ka so no harm done. And from this graph I am unable to maintain that temps might have risen at anywhere close to our current rate of 1.2 degrees per century. The fastest seems to be just over 1 degree in just under 1000 years, or at least 10 times slower than today.

35
Arctic sea ice / Nullschool Forecasts
« on: September 09, 2019, 03:12:29 PM »
I will be posting my Nullschool animations here from now on.
I hope you Like Them! And don't be shy to post your own!

Wind @ Surface Forecast

2019-09-09 09:00 UTC
2019-09-14 06:00 UTC

36
Arctic sea ice / Re: The 2019 melting season
« on: September 07, 2019, 02:19:49 PM »
Perhaps a new poll - Which Will Happen First: BOE or FFA?

(FFA: Full Forum Agreement)

37
Arctic sea ice / Re: The 2019 melting season
« on: September 01, 2019, 08:23:54 AM »
August 27-31.

2018.

Additionally: August 1-31 (fast).

38
Arctic sea ice / Re: The 2019 melting season
« on: August 26, 2019, 10:03:45 PM »
How many days of increase in a row count as a freezing season?? ;)

Also the 5-day average is lower than today's number.

I think we once all came to terms that we can use the best available but nevertheless debatable numbers for the sake of comparing apples with apples.

Nevertheless I suggest that you won't further insist that the melting season has ended 3 days ago because in that case I would suggest to label those numbers as misleading and rely on those with a higher resolution that show a drop in the range of the average for the day of the year.

On the other hand some may find it interesting to question and discuss everything but the propose that you open a separate thread to keep this one on track.

Neither temperatures nor forecasts nor events imply that a refreeze could happen except perhaps surface water (melt ponds) with fresh water but that would only ad to "Area" which apparently indeed happens.

Philopek, i was joking.  ::)

39
Arctic sea ice / Re: The 2019 melting season
« on: August 25, 2019, 03:37:15 AM »
It's way too late in the season to have an effect on the minimum of this year
I tend to agree with this statement, although using windsurf to evaluate Arctic ocean winds does not make sense. Some 30-40 knot winds is the (almost) everyday trade winds of the Canaries, but it’s exceptional in the Arctic Summer.
Also, I would wait until Wednesday to assess broader effects.

I was just kidding and it was obviously a joke. interesting how people catch every straw to falsify what they don't like.

I mean it was a long post with much reasoning and even though one does not have to agree, the usual nitpicking and picking one or two words out that SEEM wrong or don't fit one's bias and discard the entire rest is ridiculous IMO and it happens regularly and all over the place.

that surf joke was to say that those wind speeds are the lower end of having fun and certainly nothing like a killer storm and that's how i wrote it.

The other guy who call it ridiculous should look where the weak ice is, look at the charts, look at the forecasted wind and weather patterns and then tell me how the only remaining weak ice of significance and amount should melt out.

Further 2012 does not stop toda, it continues on his trajectory almost to the end and how should we make up 500k + at the same time keep further up with 2012 without a real killer event.

I also said it won't happen without such an event, I NEVER SAID IT CAN'T OR WONT' HAPPEN.

Hence there we can see the bias of a few, discarding dozens of lines, picking out  a few words and taking them out of context and launch ad-hominem attacks so that everything fits their bias until proven otherwise.

I really can't tell for sure (as i wrote earlier) but chances to catch and pass 2012 are now less than 10% and that is not ridiculous, it's reasonable and taking the risk i say I'll be right, even though i normally give a ..... to be right but with such kind of trump-like narcissists around i cant' resist to go out on this limb.

Watch my words and the only thing that is left to interesting is whether those kind of guys will ever admit and apologize. Probably not.

In contrast, Gerontocrat's reply is a valid point of few, an own opinion based on an other viewing angle and brought to our attention without further side-kicks. That's something that is widening the horizon, worth to consider and a positive feedback, no matter that the verdict is different, simply interesting.


40
Way above, in post #2332, I posted a stupid question on the relationship of 'specific heat' to warming. I fear that it has become lost among all the discussion here about how stupid, or not, subsequent "stupid" questions were. Anyone available to provide an answer?

41
Arctic sea ice / Re: The 2019 melting season
« on: July 29, 2019, 04:43:04 PM »
This post started from the ice-drift map (latest attached) and a stray image in my mind. Wind will have very little traction blowing over a flat 100% concentration ice pack (until it hits a pressure ridge). But on a load of ice rubble?

So in an attempt to do something about my total ignorance I googled and found two papers produced in 2014 from a National Science Foundation project..

https://www.arcus.org/witness-the-arctic/2014/3/article/22794
Arctic Ocean Sea Ice Loss: Modeling the effect on Wind-to-Ocean Momentum Transfer
&
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2013JC009425%4010.1002/%28ISSN%292169-9291.FAMOS1
Seasonality and long-term trend of Arctic Ocean surface stress in a model

Most of the remarks below are from the first - written so even I could understand (most) of it.
Quote
The momentum flux from the atmosphere into the ocean (also known as ocean surface stress) depends on various factors such as wind speed, surface layer stability, surface roughness, and sea ice conditions. Roughness changes in response to changing ocean surface waves and variations in the geometry of ice floes and ridges. Three regimes characterize how sea ice moderates momentum transfer into the Arctic Ocean:

    1. At very high ice concentrations, near 100%, the pack ice is so compact that it barely responds to the wind forcing and hence also shields the ocean from the wind.

    2. Slightly lower ice concentrations, about 80-90%, allow the ice to drift freely with the wind as pressure within the ice pack is reduced to a minimum, while floe edges and ridges provide high drag (See Figure 1). We refer to this as an "optimal ice concentration", because ocean surface stress is maximal in this case -- as illustrated in the graph of ocean surface stress as a function of sea ice concentration derived from Pan-Arctic Ice Ocean Modeling and Assimilation System1 (PIOMAS) output (See Figure 2).

    3. For still lower ice concentrations, stresses decline because open water—even with surface waves—is generally smoother than pack ice.
graph attached
This suggests to me that when looking at the ice drift map the effect of winds will be highest in the high concentration (but less than 100%) areas


Quote
a shrinking summer sea ice extent means less momentum flux into the ocean in this season. How is that? In the 1980s and 1990s most of the Arctic Ocean featured high ice concentrations, even in summer, with an average close to the 80-90% optimum.

In recent years however, vast areas of open water have reduced the mean ice concentration below this optimum, which results in an overall ocean stress decrease at a small but significant rate in summer.

What does the future hold? The area of high momentum flux (See green in Figure 3a) is shrinking toward Greenland as sea ice continues to retreat. Further, an expanding summer season with increasingly less ice coverage might steepen the negative ocean stress trend and eventually even reverse the positive trends in spring and fall. But this assumes that wind forcing and ocean surface waves do not grow, an assumption that might prove incorrect in a changing climate. This illustrates the fascinating interplay between opposing forces that will determine the magnitude of Arctic Ocean currents in the future.
image attached


The second paper shows show how while in summer ocean stress trend is falling, in spring and especially autumn (period of highest winds is in October) ocean stress is increasing as concentrations in much of the remaining ice have fallen to below 100%.
See last image, and here is their conclusion (edited)
Quote
Our analysis indicates that sea ice in free-drift amplifies the momentum transfer from the atmosphere into the ocean, which contradicts the general perception that sea ice damps the atmosphere-ocean exchange.

On annual average, most momentum is transferred at an ice concentration of 85%.

On the seasonal scale, sea ice conditions are optimal for maximal momentum flux into the ocean twice a year, in spring and fall. However, wind speeds are much higher in fall

What do I take from this?
- when looking at a sea-ice drift / wind speed map, have the Bremen ice concentration map to hand to see where he biggest impact will be on ice mobility (green and purple not good, yellow and red good?,
- October is the month when winds can have the maximum effect on a weakened ice pack (also Spring?),
- the data goes to 2012. Were there follow-up projects?   I hope so.
___________________________________________________________
I think this is relevant to the end of season prognosis.
I await being shot down with interest.

42
Arctic sea ice / Re: The 2019 melting season
« on: July 29, 2019, 04:26:39 PM »
unihamburg amsr2-uhh, jul28 overlaid onto more detailed bathymetry
Outstanding. Nothing like a picture to demonstrate the correlation between ocean depth and ice retention.
Thanks for the compliment (if it is one) but I don't agree with your interpretation. Both beaufort and laptev/cab (laptev bite) have had large areas of open water over deep ocean in recent years. It's highly likely the laptev bite will open up significantly over the next month.
Last year some of the ess arm never melted out over shallow water.
Please do more research, less posting.

43
Bintho
To clarify it is not that earlier temperature data lacks value but due to regional and time gaps it is less complete and precise.
Earlier in the thread the original question is how much warming has occured because of CO2 emmissions and ranges were given with numbers well below 1C and I didn't agree.
Shared Humanity
 I generally agree with you my main point is that warming exceeds 1 C. The numbers some were suggesting were as low as 0.6. Anyone who suggests it is below 1C is in my opinion misinformed or lying. Personally From what I have read I think we are at about 1.4C.

OK. I agree. Warming over preindustrial is a minimum of 1.4C but I would not rule out 1.6C.

44
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: July 27, 2019, 09:00:20 AM »
Rich, I am normally quite tolerant, and even more so towards new members. But I have been convinced there is a problem with some of your posts, and it's not about their content but about their tone. When you keep on arguing to the point of derailment due to overconfidence, when you relate to other posters as cult members, when you paint yourself as a martyr, and other examples too numerous to count, you piss people off and create dissension. I have no problem with claims of low or high momentum, this or that end if season forecast, and so on. In fact I often agree with your core content. But I still get pissed off, reading page after page of dissension which somehow involves you.

I think some humility would help fix things. It's not about you, it's about the science. Chill off. Don't take everything so personal. When you say something and are immediately told you are wrong by multiple posters, you probably are wrong. Take it to lightweight threads, go read source material (Wikipedia is often strong on the basic science but simple enough to.understand), rather than fight it out in high-rating threads. When given insults, ignore and move on, rather than insulting back. And avoid general attacks such as "cult" and so on. Humility and hard science are the proper tools here.

45
Arctic sea ice / Re: The 2019 melting season
« on: July 24, 2019, 07:08:07 PM »
Thanks Hopen Times for the correction concerning the icebreaker.

Open water is showing up on the north and east sides of the Parry channel now and ice movement can be seen on RAMMB slider. Ice in the southern channels is melting and ice from further north is getting compacted into the southern channels. I wasn't able to tell if the whole Parry channel had moving ice, but the ice is in very bad shape now.

And yes, this has been a very bad year for multiyear ice. The Nares strait was open all year. The brief arch in the Lincoln sea was maintained for a month by winds that sent ice towards the Fram strait, not the Nares. That did not help maintain thick ice. When high pressure returned in May the Beaufort became a thick ice killing zone. I expect a record minimum volume in September with little thick ice remaining.

46
Arctic sea ice / Re: The 2019 melting season
« on: July 21, 2019, 09:58:08 PM »
It was meant as a genuine question. As far as I understand it, there is controversy about whether storms or sun are worse for the ice in the late season. There seems to be good reason to suspect that the 2012 GAC had a lot to do with that year's enhanced late-season melt. Well, I guess if we do end up with widespread high pressure instead of big storms this year, we can test that hypothesis (as Neven hopes), since so far this year's setup is arguably close to as bad if not worse than 2012.

But in any case, yes, I've moved it to Stupid Questions: https://forum.arctic-sea-ice.net/index.php/topic,143.msg214841.html#msg214841 .

Thanks.

47
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: July 20, 2019, 04:15:50 PM »
NSIDC Total Area as at 19 July 2019 (5 day trailing average)  4,885,824 km2

Area loss remaining a bit below average.
                        
Total Area         
 4,885,824    km2      
-553,535    km2   <   2010's average.
-622,906    km2   <   2018
-1,308,286    km2   <   2000's average.
         
Total Area Change   -82    k   loss
Peripheral Seas   -17    k   loss
Central Seas__   -54    k   loss
Other Seas___   -11    k   loss
         
Peripheral Seas         
Bering _______   -0    k   loss
Baffin  Bay____   -4    k   loss
Greenland____   -10    k   loss
Barents ______   -3    k   loss
         
CAB Seas         
Beaufort_____   -7    k   loss
CAA_________   -7    k   loss
East Siberian__   -16    k   loss
Central Arctic_   -9    k   loss
         
Kara_________   -11    k   loss
Laptev_______    1    k   gain
Chukchi______   -5    k   loss
         
Other Seas         
Okhotsk______   -0    k   loss
St Lawrence___   -0    k   loss
Hudson Bay___   -11    k   loss

- Area loss 82 k, 12 k LESS than the 2010's average loss of 94 k on this day.
- Total area Lowest, 304 k LESS than 2016, and 6 k LESS than 2012.

Area loss remains below average, difference with 2012 narrowing, with 2016 widening.

Other Stuff
Weather Due to unforeseen circumstances....
_______________________________________________________
Weather
by
Ambrose Bierce

Once I dipt into the future far as human eye could see,
And I saw the Chief Forecaster, dead as any one can be--
Dead and damned and shut in Hades as a liar from his birth,
With a record of unreason seldome paralleled on earth.

While I looked he reared him solemnly, that incandescent youth,
From the coals that he'd preferred to the advantages of truth.
He cast his eyes about him and above him; then he wrote
On a slab of thin asbestos what I venture here to quote--
For I read it in the rose-light of the everlasting glow:
'Cloudy; variable winds, with local showers; cooler; snow.'
_________________________________________________

What all this means for melt is.... ?

Oulook
We are in the period of maximum daily area loss that lasts until late July, but is already gently sliding down. Overall, Area losses in July to date above average, but currently trending downwards.

It definitely was a steep downward slope that has now eased.

NSIDC 5 day Area could/would/should/will/will-not continue in pole position for about one week/two weeks/the rest of July/the entire remaining melt season (delete as applicable).
________________________________________________________________________

48
Greenland and Arctic Circle / Re: Greenland 2019 Melt Season
« on: July 20, 2019, 11:40:49 AM »
http://polarportal.dk/en/greenland/surface-conditions/ as at 19 July 2019

Melt quite a bit above average. Again concentrated in the West and the South. I am sure the persistence of this strong melt is unusual, as normally we just see short-term spikes.

Precipitation in central west coast, and as a result SMB (Surface Mass Balance) loss was only just above average.

GFS Precipitation is looking a bit weird. Over the next 2 to 3 days a ltlle atmospheric river comes out of Hudson Bay, crosses Ellesmere Island and Baffin Bay and splats pecipitation on the central West coast. On Monday night it stops, and outlook for the next 5 days and more looking   very dry over all Greenland.

Melt. Temperatures above freezing around most of the coast in the next week. The SST anomalies in Baffin Bay can only increase as the final scraps of sea ice melt out is completed.. High pressure has been, is, and will be stuck over Greenland until ....? This is likely to keep most of Greenland dry (apart from the West coastal fringe until Monday), and maybe sunny? This should help to maintain melt.

SMB mass change is a matter of which prevails, precipitation or melt. The 19th July was a classic demo of how although melt was well above average at the peak of the melting season, a bit of precipitation on just one part of the West coast sent SMB loss back to average.

It still looks likely the SMB graph will show above average SMB loss over the next few days after Monday due to low precipitation or perhaps rainfall at lower elevations along the West coast..

It seems clear (to me at least) that precipitation, or the lack of it, may determine the overall SMB loss during the melting season at least as much as melt. My speculation (now) hypothesis remains that in 2012, even though melt was spectacularly high, lack of precipitation was as or more important than melt in the unprecedented SMB loss that year.

At the moment 2019 is giving 2012 a run for its money (as it is for Arctic Sea Ice). How linked are they? If this melt declines to average will Arctic Sea Ice melt reduce as well (or vice-versa)?
_____________________________________________________
Note from DMI
When comparing melt with the surface mass balance under ”Daily change”, note that melting can occur without surface mass loss since the meltwater can refreeze in the underlying snow. Likewise, surface mass loss can occur without melting due to sublimation.

The map illustrates how the surface of the Greenland Ice Sheet gains and loses mass on a daily basis. This is known as the surface mass balance. It does not include the mass that is lost when glaciers calve off icebergs and melt as they come into contact with warm seawater.


49
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: July 07, 2019, 10:00:18 PM »
Smooth, Aperson!  ;)

(Not Nares but floes floeing around)


50
Arctic sea ice / Re: Latest PIOMAS update (July 2019)
« on: July 06, 2019, 07:27:02 AM »
Updated volume and volume-anomaly graphs.

Click for larger pictures, helps reading the tiny fonts.

Pages: [1]