Support the Arctic Sea Ice Forum and Blog

Author Topic: The 2020 melting season  (Read 608311 times)

wili

  • Young ice
  • Posts: 3206
    • View Profile
  • Liked: 577
  • Likes Given: 387
Re: The 2020 melting season
« Reply #5750 on: September 03, 2020, 06:35:56 AM »
Thanks, binntho. Everything I know I learned from Wiki!  ;D

" The temperature of the air depends on the temperature in the source region and the amount of descent. In the case of the Santa Ana, for example, the wind can (but does not always) become hot by the time it reaches sea level. In Antarctica [and presumably also GIS], by contrast, the wind is still intensely cold. "
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

slow wing

  • Grease ice
  • Posts: 819
    • View Profile
  • Liked: 156
  • Likes Given: 498
Re: The 2020 melting season
« Reply #5751 on: September 03, 2020, 07:57:14 AM »
August 29 - September 2.

The tail is melting quite fast!

aslan

  • Frazil ice
  • Posts: 200
    • View Profile
  • Liked: 156
  • Likes Given: 0
Re: The 2020 melting season
« Reply #5752 on: September 03, 2020, 08:38:23 AM »
August 29 - September 2.

The tail is melting quite fast!

And it is not over yet.

Again, about the GAC during the month of August 2012, the minimum pressure was quite low, but environmental pressure also. And winds are function of pressure gradient, not pressure. The IFS this morning is going down to 974 hPa. But, there is an anticyclone over the coast, with pressure up to almost 1025 hPa. In 2012, pressure along the coast were around 1010 hPa. Going from 1010 to 965 hPa is about the same (45 hPa of difference) than going from 1025 to 980 hPa (45 hPa of difference). Admittedly, total kinetic energy was greater in 2012 than what is forecasted for Monday, but overall a 980 hPa low embedded in a 1020 hPa high is able to do a lot of damages also. To illustrate, the wind in meters per second analyzed by GFS at 00Z the seventh of August 2012. Maximum winds are around 30 kts (15 m/s), which is also maximum winds forecasted by models on Monday. Again, the GAC of 2012 was probably worst with a greater total kinetic energy, but overall the absolute minimum pressure of a low is quite not the full story. This is going to be a really rough ride and it is really bad, even though we are more than 10 hPa away of the lowest pressure of the GAC 2012.

P.S. : Did not see that at first glance, but IFS 00Z is pushing above 40 kts at surface on Monday 12Z O.o ouch...

Glenn_Tamblyn

  • New ice
  • Posts: 11
    • View Profile
  • Liked: 10
  • Likes Given: 0
Re: The 2020 melting season
« Reply #5753 on: September 03, 2020, 09:01:03 AM »
mdoliner

"Melt ponds cannot drain. nine tenths of the floe is below sea level."

Imagine a floe 2 meters thick, 20 cm above water level. A melt pond forms in the middle of it, 40 cm deep, but not in contact with the ocean below. Then cracking allows it to drain. Previously the ice below the pond had the weight of 40 cm of water sitting on top of it. Now it only has 20 cm above it as the pond drains to sea level. It is essentially not balanced buoyantly. So it will try to rise.

As it rises, further water drains from the pond, until a new balance is reached. Since the remainder of the ice under the pond is 1.6 meters thick, that balance means the ex pond becomes 16 cm of ice above the water line, 1.44 meters below the water line.

If it is able to rise at all! But that requires that the connection to the ice around the pond adjusts and is put under strain. Thus possibly cracking. If the connections to the surrounding ice are strong enough to prevent the rise, then the ice is under tensile stresses at some points. Not good for a crystalline material where cracks can grow due to melting.


aslan

  • Frazil ice
  • Posts: 200
    • View Profile
  • Liked: 156
  • Likes Given: 0
Re: The 2020 melting season
« Reply #5754 on: September 03, 2020, 09:22:42 AM »
Also, new daily record for Ostrov Vize this morning, at +4.6°C at least (final value at 12Z) for the third of September. Old record, +4.0°C in 2016. This is the 21th daily record in a row, almost a month of continuous daily record...

http://www.pogodaiklimat.ru/monitor.php?id=20069

http://www.pogodaiklimat.ru/monitor.php?id=20069&month=8&year=2020

be cause

  • Nilas ice
  • Posts: 1399
    • View Profile
  • Liked: 605
  • Likes Given: 464
Re: The 2020 melting season
« Reply #5755 on: September 03, 2020, 10:40:41 AM »
https://sites.uci.edu/zlabe/files/2020/09/925T_70N_rank.png

^^ .. Zack Labe's updated monthly temp ranking puts August top of the lot (42 years ). Quite a summer up there .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 + 1 =  ' if only we could have seen it coming ' ...

peterlvmeng

  • Frazil ice
  • Posts: 127
    • View Profile
  • Liked: 33
  • Likes Given: 9
Re: The 2020 melting season
« Reply #5756 on: September 03, 2020, 10:41:37 AM »
August 29 - September 2.

The tail is melting quite fast!

And it is not over yet.

Again, about the GAC during the month of August 2012, the minimum pressure was quite low, but environmental pressure also. And winds are function of pressure gradient, not pressure. The IFS this morning is going down to 974 hPa. But, there is an anticyclone over the coast, with pressure up to almost 1025 hPa. In 2012, pressure along the coast were around 1010 hPa. Going from 1010 to 965 hPa is about the same (45 hPa of difference) than going from 1025 to 980 hPa (45 hPa of difference). Admittedly, total kinetic energy was greater in 2012 than what is forecasted for Monday, but overall a 980 hPa low embedded in a 1020 hPa high is able to do a lot of damages also. To illustrate, the wind in meters per second analyzed by GFS at 00Z the seventh of August 2012. Maximum winds are around 30 kts (15 m/s), which is also maximum winds forecasted by models on Monday. Again, the GAC of 2012 was probably worst with a greater total kinetic energy, but overall the absolute minimum pressure of a low is quite not the full story. This is going to be a really rough ride and it is really bad, even though we are more than 10 hPa away of the lowest pressure of the GAC 2012.

P.S. : Did not see that at first glance, but IFS 00Z is pushing above 40 kts at surface on Monday 12Z O.o ouch...

maybe 50hpa pressure difference predicted by EC and GFS. Last chance to break the record?
« Last Edit: September 03, 2020, 12:00:31 PM by peterlvmeng »

be cause

  • Nilas ice
  • Posts: 1399
    • View Profile
  • Liked: 605
  • Likes Given: 464
Re: The 2020 melting season
« Reply #5757 on: September 03, 2020, 10:58:29 AM »
I suppose we could break the trend .. perhaps a day 5 forecast will be realized for the 1'st time in over a month . I said at the end of July that what the Arctic needed for August was 'no weather' .. compared to the day 5 forecasts , it really had none , as storm after storm faded from forecasts . August continued with the heat ; will September bring the 'weather' ? b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 + 1 =  ' if only we could have seen it coming ' ...

gandul

  • Grease ice
  • Posts: 717
    • View Profile
  • Liked: 167
  • Likes Given: 10
Re: The 2020 melting season
« Reply #5758 on: September 03, 2020, 11:01:44 AM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Large GiF!

Ay Caramba...  ???
Caramba indeed, the beating over Laptev bite is gonna be antológico.
Perhaps extent losses will be softened with first signs of refreeze at the ice edge, because temps at the ESS tip are really sinking now.
Then the cold centered low from day 5 should end the extent losses for now. Right?

Bottom melt is in the driver seat this time of year. Until SST's drop below 2C, we won't see any substantial freeze.
I am talking about extent, read above. And I think you are absolutely wrong anyway. Bottom melt is driving ice Volume losses, but extent can start to grow anytime now due to divergence of the pack or real ocean surface refreeze in cold regions of the ice edge. Understand: an ice block can be bottom-melting while the adjacent ocean water has started refreezing. The satellite is going to see the surface refreeze, and not the bottom melt.

BornFromTheVoid

  • Nilas ice
  • Posts: 1224
    • View Profile
  • Liked: 551
  • Likes Given: 177
Re: The 2020 melting season
« Reply #5759 on: September 03, 2020, 12:07:49 PM »
Latest images and animation.
(Larger, higher res version of the animation on twitter as usual)

I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Général de GuerreLasse

  • New ice
  • Posts: 50
    • View Profile
  • Liked: 31
  • Likes Given: 23
Re: The 2020 melting season
« Reply #5760 on: September 03, 2020, 12:44:57 PM »
https://sites.uci.edu/zlabe/files/2020/09/925T_70N_rank.png

^^ .. Zack Labe's updated monthly temp ranking puts August top of the lot (42 years ). Quite a summer up there .. b.c.

It's a good thing it was a cold winter, otherwise what would be left of the ice now?
La cravate est un accessoire permettant d'indiquer la direction du cerveau de l'homme.
Un petit croquis en dit plus qu'un grand discours, mais beaucoup moins qu'un gros chèque.
Pierre DAC

Freegrass

  • Nilas ice
  • Posts: 1618
  • Emancipate yourself from mental slavery
    • View Profile
  • Liked: 516
  • Likes Given: 761
Re: The 2020 melting season
« Reply #5761 on: September 03, 2020, 01:11:19 PM »
Latest Five Day Forecast
Wind @ Surface
Wind + Temp @ 850hPa
Wind @ 250hPa
Large GiFS!

Can anyone confirm if this fat lady that's about to hit and destroy the stage is named Laura?
If every 8 year old in the world is taught meditation, we will eliminate violence from the world within one generation.
-The Dalai Lama

stjuuv

  • New ice
  • Posts: 29
    • View Profile
  • Liked: 25
  • Likes Given: 37
Re: The 2020 melting season
« Reply #5762 on: September 03, 2020, 01:36:26 PM »
Can anyone confirm if this fat lady that's about to hit and destroy the stage is named Laura?
Not an expert by any means, but Laura looks to end up over here perhaps?

Tor Bejnar

  • Young ice
  • Posts: 3651
    • View Profile
  • Liked: 635
  • Likes Given: 409
Re: The 2020 melting season
« Reply #5763 on: September 03, 2020, 01:43:03 PM »
With the North Pole region 50% covered by melt ponds, and with one MOSAiC photograph looking into what might be one of them, I imagine (my conjecture is) all of those melt ponds have 'punched through' and the 'fresh' water in the ponds has a connection to the ocean water below, although movement one way or the other is minimal.
Arctic ice is healthy for children and other living things.

bbr2315

  • Frazil ice
  • Posts: 446
    • View Profile
  • Liked: 140
  • Likes Given: 64
Re: The 2020 melting season
« Reply #5764 on: September 03, 2020, 02:19:20 PM »
The Siberian fire soot is evidently making its way into the CAB again per today's shot from EOSDIS. I wonder if the effects of black carbon become "protective" when sun angle is lower? I.E., when it is sufficiently seasonally limited, black carbon acts to reflect insolation vs absorb and trap heat?

Greenbelt

  • Frazil ice
  • Posts: 167
    • View Profile
  • Liked: 39
  • Likes Given: 24
Re: The 2020 melting season
« Reply #5765 on: September 03, 2020, 02:19:54 PM »
I realize there have been some false alarms for storms developing from the Atlantic side over the last several weeks, but this is only Day 4 and is very similar on GFS and ECMWF. A little weaker on the Canadian forecast model. That would be a important late season stirring if it happens. My hunch is there is still a lot of melt potential.

Paul

  • Frazil ice
  • Posts: 217
    • View Profile
  • Liked: 44
  • Likes Given: 3
Re: The 2020 melting season
« Reply #5766 on: September 03, 2020, 02:56:58 PM »
https://sites.uci.edu/zlabe/files/2020/09/925T_70N_rank.png

^^ .. Zack Labe's updated monthly temp ranking puts August top of the lot (42 years ). Quite a summer up there .. b.c.

It's a good thing it was a cold winter, otherwise what would be left of the ice now?

I guess we will never know for certain the answers but one thing the 'cold' winter did do was to make the Siberian ice thinner than average(there was alot of blue on the PIOMAS in the ESS and Laptev regions and compared to other years, not alot of fast ice developed either) and coupled with record snow cover melt, this region was vulnable to early ice loss and that most certainly did happen especially in the Laptev sea. This was further exasperated by the 2 to 3 weeks of persistent high pressure in July which bought southerly winds into the ESS and Laptev seas which meant the ice edge was heading northwards. Now, was this a factor why the CAB ice in general was more compact in comparison to years like 2010, 13, 16 and 17 or was it the fact the CAB had a winter more nearer to average or even a bit of both? I suspect it's more due to a lack of cyclones in the CAB this summer which is why I'm a little reluctant to always think high pressure is bad for the ice and low is good for the ice as I don't think it's quite that simple. That said, with Laptev so low on ice, it did rise SSTS significantly and maybe we have seen the affects of this in the 2nd half of the melt season. Of course winds blowing from the south has no doubt helped the ice edge reaching 85 degrees north but high SSTS more than likely has played a role also.

I suppose we can only speculate but the facts are, we seen record snow cover retreat in Siberia this spring, record Siberian melt and we are comfortably finishing 2nd lowest. And unfortunately we will probably going too see record lows in the coming months as there is alot of heat to release before sea ice forms.


BornFromTheVoid

  • Nilas ice
  • Posts: 1224
    • View Profile
  • Liked: 551
  • Likes Given: 177
Re: The 2020 melting season
« Reply #5767 on: September 03, 2020, 03:04:39 PM »
I realize there have been some false alarms for storms developing from the Atlantic side over the last several weeks, but this is only Day 4 and is very similar on GFS and ECMWF. A little weaker on the Canadian forecast model. That would be a important late season stirring if it happens. My hunch is there is still a lot of melt potential.


Yep, I've been keeping an eye on these storms, some quite powerful, but was reluctant to say much until they move a bit closer. Definitely concerning now that they are in the day 4 range
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Général de GuerreLasse

  • New ice
  • Posts: 50
    • View Profile
  • Liked: 31
  • Likes Given: 23
Re: The 2020 melting season
« Reply #5768 on: September 03, 2020, 03:43:14 PM »
https://sites.uci.edu/zlabe/files/2020/09/925T_70N_rank.png

^^ .. Zack Labe's updated monthly temp ranking puts August top of the lot (42 years ). Quite a summer up there .. b.c.

It's a good thing it was a cold winter, otherwise what would be left of the ice now?

I guess we will never know for certain the answers but one thing the 'cold' winter did do was to make the Siberian ice thinner than average(there was alot of blue on the PIOMAS in the ESS and Laptev regions and compared to other years, not alot of fast ice developed either) and coupled with record snow cover melt, this region was vulnable to early ice loss and that most certainly did happen especially in the Laptev sea. This was further exasperated by the 2 to 3 weeks of persistent high pressure in July which bought southerly winds into the ESS and Laptev seas which meant the ice edge was heading northwards. Now, was this a factor why the CAB ice in general was more compact in comparison to years like 2010, 13, 16 and 17 or was it the fact the CAB had a winter more nearer to average or even a bit of both? I suspect it's more due to a lack of cyclones in the CAB this summer which is why I'm a little reluctant to always think high pressure is bad for the ice and low is good for the ice as I don't think it's quite that simple. That said, with Laptev so low on ice, it did rise SSTS significantly and maybe we have seen the affects of this in the 2nd half of the melt season. Of course winds blowing from the south has no doubt helped the ice edge reaching 85 degrees north but high SSTS more than likely has played a role also.

I suppose we can only speculate but the facts are, we seen record snow cover retreat in Siberia this spring, record Siberian melt and we are comfortably finishing 2nd lowest. And unfortunately we will probably going too see record lows in the coming months as there is alot of heat to release before sea ice forms.

Yes Paul, look at Zack's chart as well as this Gerontocrat chart (PIOMAS figures) and Nico Sun's graph.  Yes definitely yes the winter was colder than the average winter of the years 2010. What more can you expect?
La cravate est un accessoire permettant d'indiquer la direction du cerveau de l'homme.
Un petit croquis en dit plus qu'un grand discours, mais beaucoup moins qu'un gros chèque.
Pierre DAC

Shared Humanity

  • Frazil ice
  • Posts: 192
    • View Profile
  • Liked: 124
  • Likes Given: 6
Re: The 2020 melting season
« Reply #5769 on: September 03, 2020, 03:50:16 PM »
Latest Five Day Forecast
Wind + Temp @ Surface
Large GiF!

Can we still break the record if this really happens?

Impressive low. Might actually disperse a highly fragmented ice pack and expand SIE briefly. Is there enough heat in the ocean to melt this ice that migrates outward?

Paul

  • Frazil ice
  • Posts: 217
    • View Profile
  • Liked: 44
  • Likes Given: 3
Re: The 2020 melting season
« Reply #5770 on: September 03, 2020, 04:11:02 PM »
https://sites.uci.edu/zlabe/files/2020/09/925T_70N_rank.png

^^ .. Zack Labe's updated monthly temp ranking puts August top of the lot (42 years ). Quite a summer up there .. b.c.

It's a good thing it was a cold winter, otherwise what would be left of the ice now?

I guess we will never know for certain the answers but one thing the 'cold' winter did do was to make the Siberian ice thinner than average(there was alot of blue on the PIOMAS in the ESS and Laptev regions and compared to other years, not alot of fast ice developed either) and coupled with record snow cover melt, this region was vulnable to early ice loss and that most certainly did happen especially in the Laptev sea. This was further exasperated by the 2 to 3 weeks of persistent high pressure in July which bought southerly winds into the ESS and Laptev seas which meant the ice edge was heading northwards. Now, was this a factor why the CAB ice in general was more compact in comparison to years like 2010, 13, 16 and 17 or was it the fact the CAB had a winter more nearer to average or even a bit of both? I suspect it's more due to a lack of cyclones in the CAB this summer which is why I'm a little reluctant to always think high pressure is bad for the ice and low is good for the ice as I don't think it's quite that simple. That said, with Laptev so low on ice, it did rise SSTS significantly and maybe we have seen the affects of this in the 2nd half of the melt season. Of course winds blowing from the south has no doubt helped the ice edge reaching 85 degrees north but high SSTS more than likely has played a role also.

I suppose we can only speculate but the facts are, we seen record snow cover retreat in Siberia this spring, record Siberian melt and we are comfortably finishing 2nd lowest. And unfortunately we will probably going too see record lows in the coming months as there is alot of heat to release before sea ice forms.

Yes Paul, look at Zack's chart as well as this Gerontocrat chart (PIOMAS figures) and Nico Sun's graph.  Yes definitely yes the winter was colder than the average winter of the years 2010. What more can you expect?

I'm not sure what you mean in terms of what more can  I expect but we do know a positive AO does mean colder weather but more fram export and less thickening in the Siberian seas as winds are keep coming off the land masses hence why the ice in the Siberian parts of the basin looked vulnable this year.

Now whether the winter coldness in the CAB helped to presserve more ice  or not we will never know but it certainly did not help to gain ice thicknesses in other parts of the basin.

binntho

  • Nilas ice
  • Posts: 1519
    • View Profile
  • Liked: 528
  • Likes Given: 119
Re: The 2020 melting season
« Reply #5771 on: September 03, 2020, 04:13:04 PM »
mdoliner

"Melt ponds cannot drain. nine tenths of the floe is below sea level."

Imagine a floe 2 meters thick, 20 cm above water level. A melt pond forms in the middle of it, 40 cm deep, but not in contact with the ocean below. Then cracking allows it to drain.
I'm not sure if that could happen. If the ice cracks, seawater from below will push it's way into the cracks until it reaches the meltpond, at which point the surface of the meltpond will fall down to sea level. The weight balance of the ice floe would change slighly, but the melt and cracking needed to connect the meltpond to the underlying seawater would probably involve a much greater disturbance.

But the water in the meltpond cannot "drain" down through 1.6m of ice to somehow pour out into the surrounding ocean at a depth of 1.8 meters (in your example) - what force would compel it to take on such a journey? Not gravity, that's for sure.

In fact, talking about meltponds "draining" is probably meaningless. If the ice that seperates the meltpond from the underlying seawater melts or cracks, the water level of the meltpond will change to match the level of the surrounding ocean by mixing with the intruding seawater. But this slight change in the weight balance of the floe is much smaller than the changes required to enable the pond to communicate with the underlying seawater.

Sorry for the tautological posting.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

Freegrass

  • Nilas ice
  • Posts: 1618
  • Emancipate yourself from mental slavery
    • View Profile
  • Liked: 516
  • Likes Given: 761
Re: The 2020 melting season
« Reply #5772 on: September 03, 2020, 04:17:55 PM »
Latest Five Day Forecast
Wind + Temp @ Surface
Large GiF!

Can we still break the record if this really happens?

Impressive low. Might actually disperse a highly fragmented ice pack and expand SIE briefly. Is there enough heat in the ocean to melt this ice that migrates outward?
I think a storm like this will stir up the ocean and bring up a lot of saltier warm water from the deep. This will probably extent the melting season a little and give the ice some more time to melt out in all that newly delivered salty warm water.
If every 8 year old in the world is taught meditation, we will eliminate violence from the world within one generation.
-The Dalai Lama

UCMiami

  • Frazil ice
  • Posts: 128
    • View Profile
  • Liked: 92
  • Likes Given: 111
Re: The 2020 melting season
« Reply #5773 on: September 03, 2020, 04:20:56 PM »
While the weather forecasts for storms entering the arctic have been incorrect or overly optimistic, what is impressive to me is the current weather history of strong winds blowing north from the laptev/kara shores over the ice (and the fact that these were present in the forecasts 5 days out for the last 10 days at least. That length of time for a consistent 20-30+km/hr wind over the very open arctic ocean and into the ice edge has built up significant wave height that must be propagating some distance into the ice.

The only source I know of that provides an actual indication of wave close to the ice edge indicates 5-6 ft with 5-6 second period - not long swell so not as destructive to the ice behind the edge.

The forecast continues this wind through the next 4 days.

UCMiami

  • Frazil ice
  • Posts: 128
    • View Profile
  • Liked: 92
  • Likes Given: 111
Re: The 2020 melting season
« Reply #5774 on: September 03, 2020, 04:33:54 PM »
On the strong divergence between area and extent numbers over the last few days in the CAB, I wonder if this is specifically due to all those melt ponds the Polarstern photos uncovered starting to freeze over and possibly increased snow events? Area detection has always had some issue with melt pond vs. ocean, and the noticeable increases in area do not seem to be reflected in the actual disappearance of open leads - the CAB hasn't been visibly dispersed and the edge encroachment on the Atlantic and most of the Asian side should be decreasing area as well as extent.

(Or has the N. Greenland opening started to close up? The sensors seem to still indicate it is there, but cloud has obscured the WV images.)

Glen Koehler

  • Frazil ice
  • Posts: 356
    • View Profile
  • Liked: 349
  • Likes Given: 771
Re: The 2020 melting season
« Reply #5775 on: September 03, 2020, 04:45:48 PM »
     I had the same question about CAB area increasing.  Understandable that concentration ratio increases as Extent declines and Area remains the same.  But sea surface temperature in the CAB does not look low enough to begin refreezing, so why would Area be increasing?  Given the difficulty in consistently estimating Area (which is why NSIDC, JAXA, and others use the less precise Extent, because while less informative than Area, the daily change in estimating Extent is less and thus gives more consistent values to compare across time periods), I wonder if the recent increase in Area is a measurement anomaly not a real increase.

Freegrass

  • Nilas ice
  • Posts: 1618
  • Emancipate yourself from mental slavery
    • View Profile
  • Liked: 516
  • Likes Given: 761
Re: The 2020 melting season
« Reply #5776 on: September 03, 2020, 04:53:38 PM »
mdoliner

"Melt ponds cannot drain. nine tenths of the floe is below sea level."

Imagine a floe 2 meters thick, 20 cm above water level. A melt pond forms in the middle of it, 40 cm deep, but not in contact with the ocean below. Then cracking allows it to drain.
I'm not sure if that could happen. If the ice cracks, seawater from below will push it's way into the cracks until it reaches the meltpond, at which point the surface of the meltpond will fall down to sea level. The weight balance of the ice floe would change slighly, but the melt and cracking needed to connect the meltpond to the underlying seawater would probably involve a much greater disturbance.

But the water in the meltpond cannot "drain" down through 1.6m of ice to somehow pour out into the surrounding ocean at a depth of 1.8 meters (in your example) - what force would compel it to take on such a journey? Not gravity, that's for sure.

In fact, talking about meltponds "draining" is probably meaningless. If the ice that seperates the meltpond from the underlying seawater melts or cracks, the water level of the meltpond will change to match the level of the surrounding ocean by mixing with the intruding seawater. But this slight change in the weight balance of the floe is much smaller than the changes required to enable the pond to communicate with the underlying seawater.

Sorry for the tautological posting.
I opened up a new thread to discuss melt ponds further, because This is interesting and we better not clog up this thread with it. My question is if the fresh water wouldn't drain until it reaches the level of the fresh water/salt water boundary?

Let's discuss it here.
https://forum.arctic-sea-ice.net/index.php/topic,427.msg284825.html#msg284825
« Last Edit: September 03, 2020, 05:49:21 PM by Freegrass »
If every 8 year old in the world is taught meditation, we will eliminate violence from the world within one generation.
-The Dalai Lama

mdoliner

  • New ice
  • Posts: 22
    • View Profile
  • Liked: 5
  • Likes Given: 0
Re: The 2020 melting season
« Reply #5777 on: September 03, 2020, 05:17:29 PM »
Glen Tamblyn re pond draining.

If there is a hole in the bottom of the pond the ice is the same as a floating doughnut. the water in the hole will rise to sea level. i agree that the water in the pond that is above sea level will drain, but that is only one tenth of the depth of the pond.  And yes the floe will be lighter by the amount that drains, but the pond, since it is draining, has the depth of the whole floe. nine-tenths of its depth will remain. Of course if the pond is very shallow and yet punches through in one deep place so that all the water is above sea level yes it will drain, but ponds warm faster than ice because of albedo, so why would that happen?

Sarat

  • New ice
  • Posts: 41
    • View Profile
  • Liked: 15
  • Likes Given: 113
Re: The 2020 melting season
« Reply #5778 on: September 03, 2020, 05:34:59 PM »
The Beaufort Scorpion Tail, is thinning out.... wonder if it will make it to the refreeze.

Général de GuerreLasse

  • New ice
  • Posts: 50
    • View Profile
  • Liked: 31
  • Likes Given: 23
Re: The 2020 melting season
« Reply #5779 on: September 03, 2020, 05:45:12 PM »
I'm not sure what you mean in terms of what more can  I expect but we do know a positive AO does mean colder weather but more fram export and less thickening in the Siberian seas as winds are keep coming off the land masses hence why the ice in the Siberian parts of the basin looked vulnable this year.

Now whether the winter coldness in the CAB helped to presserve more ice  or not we will never know but it certainly did not help to gain ice thicknesses in other parts of the basin.
[/quote]

If you don't see the relationship between cold and ice ... then I give up.
La cravate est un accessoire permettant d'indiquer la direction du cerveau de l'homme.
Un petit croquis en dit plus qu'un grand discours, mais beaucoup moins qu'un gros chèque.
Pierre DAC

oren

  • Moderator
  • First-year ice
  • Posts: 6312
    • View Profile
  • Liked: 2319
  • Likes Given: 1963
Re: The 2020 melting season
« Reply #5780 on: September 03, 2020, 05:51:44 PM »
     I had the same question about CAB area increasing.  Understandable that concentration ratio increases as Extent declines and Area remains the same.  But sea surface temperature in the CAB does not look low enough to begin refreezing, so why would Area be increasing?  Given the difficulty in consistently estimating Area (which is why NSIDC, JAXA, and others use the less precise Extent, because while less informative than Area, the daily change in estimating Extent is less and thus gives more consistent values to compare across time periods), I wonder if the recent increase in Area is a measurement anomaly not a real increase.
I am quite sure there is no refreeze of surface ocean water just yet, even near the North Pole. This could come a week or two from now. However, melt ponds should have iced over by now in many parts, especially where it snowed. In addition, I think clouds are fooling with the sensors a bit.

wili

  • Young ice
  • Posts: 3206
    • View Profile
  • Liked: 577
  • Likes Given: 387
Re: The 2020 melting season
« Reply #5781 on: September 03, 2020, 05:56:22 PM »
Would wind hasten such freezing, due to evaporative cooling?
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

gandul

  • Grease ice
  • Posts: 717
    • View Profile
  • Liked: 167
  • Likes Given: 10
Re: The 2020 melting season
« Reply #5782 on: September 03, 2020, 06:01:44 PM »
     I had the same question about CAB area increasing.  Understandable that concentration ratio increases as Extent declines and Area remains the same.  But sea surface temperature in the CAB does not look low enough to begin refreezing, so why would Area be increasing?  Given the difficulty in consistently estimating Area (which is why NSIDC, JAXA, and others use the less precise Extent, because while less informative than Area, the daily change in estimating Extent is less and thus gives more consistent values to compare across time periods), I wonder if the recent increase in Area is a measurement anomaly not a real increase.
I am quite sure there is no refreeze of surface ocean water just yet, even near the North Pole. This could come a week or two from now. However, melt ponds should have iced over by now in many parts, especially where it snowed. In addition, I think clouds are fooling with the sensors a bit.
Early next week to be more precise.

oren

  • Moderator
  • First-year ice
  • Posts: 6312
    • View Profile
  • Liked: 2319
  • Likes Given: 1963
Re: The 2020 melting season
« Reply #5783 on: September 03, 2020, 06:17:48 PM »
2016 which had open water patches near the pole saw initial refreeze on Sep 9th. OTOH 2012 which was more compacted saw initial refreeze on Sep 17th. I expect 2020 to fall within this range, weather dependent of course, with good reasons why it should be early and good reasons why it should be late.

Glen Koehler

  • Frazil ice
  • Posts: 356
    • View Profile
  • Liked: 349
  • Likes Given: 771
Re: The 2020 melting season
« Reply #5784 on: September 03, 2020, 07:23:54 PM »
    Thanks Oren, your explanatoin makes sense to me, and restores peaceful harmony to my cognitive dissonance, at least the part of it due to Arctic sea ice Area stats.

Shared Humanity

  • Frazil ice
  • Posts: 192
    • View Profile
  • Liked: 124
  • Likes Given: 6
Re: The 2020 melting season
« Reply #5785 on: September 03, 2020, 07:33:47 PM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Large GiF!

Ay Caramba...  ???
Caramba indeed, the beating over Laptev bite is gonna be antológico.
Perhaps extent losses will be softened with first signs of refreeze at the ice edge, because temps at the ESS tip are really sinking now.
Then the cold centered low from day 5 should end the extent losses for now. Right?

Bottom melt is in the driver seat this time of year. Until SST's drop below 2C, we won't see any substantial freeze.
I am talking about extent, read above. And I think you are absolutely wrong anyway. Bottom melt is driving ice Volume losses, but extent can start to grow anytime now due to divergence of the pack or real ocean surface refreeze in cold regions of the ice edge. Understand: an ice block can be bottom-melting while the adjacent ocean water has started refreezing. The satellite is going to see the surface refreeze, and not the bottom melt.

I could very well be absolutely wrong. Will not be the first or last time. Some here have stated in the past that sea water will not begin to freeze until it reaches -2C. I was merely repeating what I have read. While very cold air temperatures will begin to draw heat from the water, the water will not freeze until it has reached -2C. I'm not certain what the SST's are right now along the perimeter of the ice so it may very well start freezing.

ArcticMelt2

  • Grease ice
  • Posts: 929
    • View Profile
  • Liked: 192
  • Likes Given: 37
Re: The 2020 melting season
« Reply #5786 on: September 03, 2020, 07:40:52 PM »
Today, the open sea area north of latitude 85 has increased even more.

oren

  • Moderator
  • First-year ice
  • Posts: 6312
    • View Profile
  • Liked: 2319
  • Likes Given: 1963
Re: The 2020 melting season
« Reply #5787 on: September 03, 2020, 07:41:08 PM »
The rule of thumb I recall is that air temps of -10C will initialize the refreeze. Such temps will manage to cool the sea surface fast enough to freeze the top, before the cooled and heavy water has a chance to sink and be replaced by warmer water from below.
This of course depends on sea surface temps and salinity, the time elapsed with negative air temps, and other factors.

Tor Bejnar

  • Young ice
  • Posts: 3651
    • View Profile
  • Liked: 635
  • Likes Given: 409
Re: The 2020 melting season
« Reply #5788 on: September 03, 2020, 07:41:31 PM »
The Beaufort Scorpion Tail, is thinning out.... wonder if it will make it to the refreeze.
That's what I though it was - more menacing than a mere tail!  :)
Arctic ice is healthy for children and other living things.

Lord M Vader

  • Nilas ice
  • Posts: 1330
    • View Profile
  • Liked: 46
  • Likes Given: 29
Re: The 2020 melting season
« Reply #5789 on: September 03, 2020, 07:46:47 PM »
Oren, have you read NSIDC latest post wrt SIE in August. An interesting note there wrt Atlantification and a new study.

oren

  • Moderator
  • First-year ice
  • Posts: 6312
    • View Profile
  • Liked: 2319
  • Likes Given: 1963
Re: The 2020 melting season
« Reply #5790 on: September 03, 2020, 08:15:27 PM »
Haven't had the chance LMV. Feel free to post relevant excerpts.

Greenbelt

  • Frazil ice
  • Posts: 167
    • View Profile
  • Liked: 39
  • Likes Given: 24
Re: The 2020 melting season
« Reply #5791 on: September 03, 2020, 08:45:18 PM »
Latest ECMWF has continued flow from Laptev and Barents Seas arcing toward the pole for a couple more days, followed by a sub 980mb storm entering from the Atlantic. Consistent with prior runs and with GFS. Should be strong winds across quite a lot of the central ice by Day 3.

gandul

  • Grease ice
  • Posts: 717
    • View Profile
  • Liked: 167
  • Likes Given: 10
Re: The 2020 melting season
« Reply #5792 on: September 03, 2020, 09:03:30 PM »
Quote
Bottom melt is in the driver seat this time of year. Until SST's drop below 2C, we won't see any substantial freeze.
I am talking about extent, read above. And I think you are absolutely wrong anyway. Bottom melt is driving ice Volume losses, but extent can start to grow anytime now due to divergence of the pack or real ocean surface refreeze in cold regions of the ice edge. Understand: an ice block can be bottom-melting while the adjacent ocean water has started refreezing. The satellite is going to see the surface refreeze, and not the bottom melt.

I could very well be absolutely wrong. Will not be the first or last time. Some here have stated in the past that sea water will not begin to freeze until it reaches -2C. I was merely repeating what I have read. While very cold air temperatures will begin to draw heat from the water, the water will not freeze until it has reached -2C. I'm not certain what the SST's are right now along the perimeter of the ice so it may very well start freezing.
Below the max and min temps for today (GFS). Actually the CAB region north of ESS has been under zero for at least a couple of days, with much lower temperatures during night. And it’s been quiet there, with the anticyclone winds around but not over that region. And the low next week is bringing a nice blow of colder ice so expect the ice edge there to start to blossom soon.

What I wanted to convey is that bottom melt is maintained until october because the ice isolates the bottom from the colder temperatures outside while a thin layer top of the ocean will lose its heat quickly especially if the ocean is calm and heat flux is limited. It will start to form small crystals as soon as it loses enough heat and you only need quiet sea, open skies, and temps almost continuously below freezing. Bottom melt doesn’t govern a thing with respect to extent anyway, it’s too late, in any case it contributes to reducing ice volume but extent now? I don’t think so.
Really getting there in places.
« Last Edit: September 03, 2020, 09:09:01 PM by gandul »

gerontocrat

  • First-year ice
  • Posts: 9363
    • View Profile
  • Liked: 3746
  • Likes Given: 28
Re: The 2020 melting season
« Reply #5793 on: September 03, 2020, 09:04:44 PM »
Haven't had the chance LMV. Feel free to post relevant excerpts.
Here is an irrelevant(?) excerpt from the posting at https://nsidc.org/arcticseaicenews/

Quote
The United States’ medium-duty icebreaker Healy did not fare as well—a fire broke out in the engine compartment, and although it was quickly extinguished, the damage is extensive, and with the ship temporarily out of commission, a planned expedition to the Chukchi and Beaufort Seas has been cancelled.

How about a simple poll.
The US navy will get a new icebreaker before or after the first BOE. Yes or No.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

aslan

  • Frazil ice
  • Posts: 200
    • View Profile
  • Liked: 156
  • Likes Given: 0
Re: The 2020 melting season
« Reply #5794 on: September 03, 2020, 09:14:40 PM »
While the weather forecasts for storms entering the arctic have been incorrect or overly optimistic, what is impressive to me is the current weather history of strong winds blowing north from the laptev/kara shores over the ice (and the fact that these were present in the forecasts 5 days out for the last 10 days at least. That length of time for a consistent 20-30+km/hr wind over the very open arctic ocean and into the ice edge has built up significant wave height that must be propagating some distance into the ice.

The only source I know of that provides an actual indication of wave close to the ice edge indicates 5-6 ft with 5-6 second period - not long swell so not as destructive to the ice behind the edge.

The forecast continues this wind through the next 4 days.

It is the Arctic Ocean here, not Hawaii. Even though I understand what you mean, even a 6 second period is quite significant for the Arctic. I think I have never seen a wave period greater than 10 seconds in the Arctic basin proper, even in 2012 or in 2016 (not counting the Kara sea were some long swells from Atlantic can be worst, of course). On top of that, wave period is probably going to be higher. I am not sure where you draw your values, but for now the forecast is for a wave period of at least 6 to 8 seconds. The strongest winds are likely to be over ice, but even in this case the fetch will probably be quite enough for this kind of value.

P.S : For ones who like esoteric diagramm...
« Last Edit: September 03, 2020, 09:23:35 PM by aslan »

Freegrass

  • Nilas ice
  • Posts: 1618
  • Emancipate yourself from mental slavery
    • View Profile
  • Liked: 516
  • Likes Given: 761
Re: The 2020 melting season
« Reply #5795 on: September 03, 2020, 09:19:22 PM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Large GiF!

Almost forgot...  :-[
If every 8 year old in the world is taught meditation, we will eliminate violence from the world within one generation.
-The Dalai Lama

uniquorn

  • Young ice
  • Posts: 2757
    • View Profile
  • Liked: 1248
  • Likes Given: 247
Re: The 2020 melting season
« Reply #5796 on: September 03, 2020, 09:26:30 PM »
Recent drift of buoys on or near the mosaic floe show what may be a small tidal component that looks quite insignificant



Today's follow mosaic picture and text is timely, showing a picture of a refrozen lead and stating that 'the ice is quite dynamic with some leads and ridges developing during the tidal cycle'
Note that we are never sure on which day a photo was taken but it is almost certainly near the new mosaic floe.

edit: Or maybe that's a melt pond and tides had nothing to do with it...
« Last Edit: September 03, 2020, 09:45:09 PM by uniquorn »

ArcticMelt2

  • Grease ice
  • Posts: 929
    • View Profile
  • Liked: 192
  • Likes Given: 37
Re: The 2020 melting season
« Reply #5797 on: September 03, 2020, 09:37:54 PM »
https://twitter.com/Pat_wx/status/1301514635884011521

Quote
Almost all of Canada was warmer than normal this August. Iqaluit even recorded its warmest August on record, beating 2010 by 0.14°C. #climate #WxTwitter


ArcticMelt2

  • Grease ice
  • Posts: 929
    • View Profile
  • Liked: 192
  • Likes Given: 37
Re: The 2020 melting season
« Reply #5798 on: September 03, 2020, 09:43:15 PM »

Lord M Vader

  • Nilas ice
  • Posts: 1330
    • View Profile
  • Liked: 46
  • Likes Given: 29
Re: The 2020 melting season
« Reply #5799 on: September 03, 2020, 09:50:32 PM »
From NSIDC most recent post wrt Arctic sea ice and Atlantification: "Atlantification continues
As discussed in a recent paper in the Journal of Climate led by colleague Igor Polyakov of the University of Alaska, the process of “Atlantification” of the Arctic Ocean, first noted in the Barents Sea, is continuing, with significant effects on the sea ice cover during the winter season in the Eastern Eurasian Basin. The relatively fresh surface layer of the Arctic Ocean is underlain by warm, salty water that is imported from the northern Atlantic Ocean. The cold fresh surface layer, because of its lower density, largely prevents the warm, salty Atlantic waters from mixing upwards. However, the underlying Atlantic water appears to have moved closer to the surface in recent years, reducing the density contrast with the water above it. Recent observations show this warm water “blob,” usually found at about 150 meters (492 feet) below the surface, has shifted within 80 meters (263 feet) of the surface. This has resulted in an increase in the upward winter ocean heat flow to the underside of the ice from typical values of 3 to 4 watts per square meter in 2007 to 2008 to greater than 10 watts per square meter from 2016 to 2018. Polyakov estimates that this is equivalent to a two-fold reduction in winter ice growth."

Further reading: Polyakov, I. V., et al. 2020. Weakening of Cold Halocline Layer Exposes Sea Ice to Oceanic Heat in the Eastern Arctic Ocean. Journal of Climate, 33, 8107–8123, doi:10.1175/JCLI-D-19-0976.1.