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jdallen

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Re: The 2019 melting season
« Reply #1150 on: May 26, 2019, 10:28:35 PM »
Beaufort clouding up somewhat - but not like 2016. To @fishoutofwater's point, These are bringing soggy dynamism from the South to the arctic periphery, wheras back then, they were extending a chilling blanket from the North: Viz:
Concur - very different, and 2019 still seems to be retaining much lower albedo over the region as a whole. 

Seems to me the active circulation from the cyclone at least partially undoes the positive effect of cloudiness screening out insolation.
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FishOutofWater

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Re: The 2019 melting season
« Reply #1151 on: May 26, 2019, 10:45:06 PM »
Nice work Uniquorn - that looks like an area of meltponding very near the pole. It's impressively warm for late May. I don't trust the GFS temperature forecasts over snow or ice so I look at the ECMWF 850 model output to get an idea of whether this high pressure set up will stay warm and it does so for a week in the model. After a week all of the model output looks "proggy" - not real. Both the GFS and ECMWF models show atmospheric pattern circulation shifts might happen but the patterns don't look coherent to me.

Whatever, for this morning's initialization, this was a "hot high" as the image below shows. We saw in 2016 how a very bad start to the melting season can be saved by a cool July. This year we could also have a more ice friendly pattern begin in June. I've looked over the Arctic oscillation patterns for many summers and found much apparently random variability. That certainly makes it interesting.

We should be very skeptical about GFS temperature predictions over snow and ice. The forecast temperature anomalies appear to be unrealistically high to me. Interpreting weather maps in this situation is challenging for someone like me who has been looking at them for decades.

Neven

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Re: The 2019 melting season
« Reply #1152 on: May 26, 2019, 10:54:39 PM »
We should be very skeptical about GFS temperature predictions over snow and ice.

Thanks for the reminder, as I keep forgetting this. Karsten Haustein has comparisons 'of previous model runs for current forecast time step', and they show that GFS forecast mostly run too hot.

For example, last 30 days:
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jdallen

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Re: The 2019 melting season
« Reply #1153 on: May 26, 2019, 10:55:11 PM »
We should be very skeptical about GFS temperature predictions over snow and ice. The forecast temperature anomalies appear to be unrealistically high to me. Interpreting weather maps in this situation is challenging for someone like me who has been looking at them for decades.
Similar kudo's to Uniquorn... and FooW, while not having your expertise or time in grade with meteorology, am beginning to understand your uncertainty.

Regarding the AO index and what it portends... it seems to me the negative AO signals conditions that will tend to make flow in the Arctic less stable, and permit more intrusions of heat and moisture.

The cloudiness would be welcome as it would be a negative feedback.  The heat (via moisture) would not, especially if it actually makes to the pack as rain.
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Glen Koehler

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Re: The 2019 melting season
« Reply #1154 on: May 26, 2019, 11:00:55 PM »
     Bottom melting is a known driver but seems to get little monitoring.

    1)  In addition to temperature, cloud cover, insolation, wind, ice extent/area, ice thickness, ice age, ice condition, melt pond momentum, and land attachment, does the amount and temperature of Atlantic current inflow act as a driving factor for melt? 

    2)  Are there tracking and forecast maps/summaries for Atlantic inflow volume and temperature to use as predictors?  Known historical patterns or correlations with September minimum.
     
    3) Ditto Pacific inflow, but my understanding is that Atlantic inflow is a stronger influence.

    4)  Exploring my ignorance out to its edge, it seems like there might be a trend for cloudier Arctic summer weather with increased open water.   To the extent that there is skill, multi-month June-September Arctic weather outlook would be interesting.
 
PS #1088 JDAllen - interesting point about melt ponds not just changing albedo but also serving to conduct air temperature into ice.  Never heard that before but it makes sense.

Test question "What is causing Arctic Sea Ice loss" - 3 letter acronym.  Stumped me.



   

Glen Koehler

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Re: The 2019 melting season
« Reply #1155 on: May 26, 2019, 11:06:26 PM »
AGW?

<Yup; N.>
« Last Edit: May 26, 2019, 11:13:47 PM by Neven »

slow wing

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Re: The 2019 melting season
« Reply #1156 on: May 26, 2019, 11:13:27 PM »
The whole Siberian side is starting to shred.

Yes, although that has been a common feature through the years at around this date.

As others have already mentioned, the Beaufort is in about the worst shape for any year at this date, with only 2016 comparable.

This is a good web page (from Neven) for at-a-glance comparisons between years at a given date:
https://sites.google.com/site/arcticseaicegraphs/concentration-maps/sic0525

Neven

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Re: The 2019 melting season
« Reply #1157 on: May 26, 2019, 11:16:58 PM »

This is a good web page (from Neven) for at-a-glance comparisons between years at a given date:
https://sites.google.com/site/arcticseaicegraphs/concentration-maps/sic0525

Thanks for the link, SW. It's the part of the ASIG I'm most proud of, as it's one of the most useful pages, IMO.

There's one small problem with those pages, however, and that's that some maps can't be clicked for a larger version. The way I update those pages every year, is by dragging the maps from one table cell to another. But when I do that, the link disappears. I coincidentally found out about that two days ago, and it looks like I will have to adjust all the pages manually. May take a while, sorry.
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jdallen

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Re: The 2019 melting season
« Reply #1158 on: May 26, 2019, 11:26:42 PM »
     Bottom melting is a known driver but seems to get little monitoring.

Very difficult problem, as we don't have a lot of permanent stations for measuring/monitoring it, and it mostly has to be derived from satellite data.  This similarly translates into the uncertainty we have for ice thickness and volume. But to your point, it's actually monitored a lot, but the uncertainty of the measurement is not as low as we'd like.

    1)  In addition to temperature, cloud cover, insolation, wind, ice extent/area, ice thickness, ice age, ice condition, melt pond momentum, and land attachment, does the amount and temperature of Atlantic current inflow act as a driving factor for melt? 
It does, but we're still trying to understand it.  Mostly it's reflected in the increasing volatility of extent in the Barentz - looking at SST's over time, you can see "hot spots" evolving as we see here:

http://ocean.dmi.dk/arctic/satellite/index.uk.php

(sidebar: NOAA used to have very nice arctic view SST anomaly maps - they seem to have disappeared - anyone know what happened to them/have new links?)

    2)  Are there tracking and forecast maps/summaries for Atlantic inflow volume and temperature to use as predictors?  Known historical patterns or correlations with September minimum.     

Not really, or at least not that I'm aware of.  Again, we're still wrestling with a lack of sensor data, and mostly understanding it by inference from other measures, which have similarly limited sensor data such as salinity, SST and sub-surface temperature.

    3) Ditto Pacific inflow, but my understanding is that Atlantic inflow is a stronger influence.


See (2) answer above.  Same dance, different song.


    4)  Exploring my ignorance out to its edge, it seems like there might be a trend for cloudier Arctic summer weather with increased open water.   To the extent that there is skill, multi-month June-September Arctic weather outlook would be interesting.

It would, and there are others in forum who'd be better able to point you in the direction of resources.

A thread was started for that here:

https://forum.arctic-sea-ice.net/index.php/topic,2692.0.html


PS #1088 JDAllen - interesting point about melt ponds not just changing albedo but also serving to conduct air temperature into ice.  Never heard that before but it makes sense.

I was less thinking about transmission of heat from the atmosphere, and more about insolation and long-wave radiation trapped by the water being concentrated and directed to the ice via convection.  Having water on top of the ice transferring atmospheric heat I'm actually not so sure of; I actually think it may be a wash between the two.

Again, I think the major effect of meltponds is better capture of various forms of radiation rather than convective or evaporative heat exchange with atmosphere.


Test question "What is causing Arctic Sea Ice loss" - 3 letter acronym.  Stumped me.
 

Me too.  Context?  ;)
« Last Edit: May 26, 2019, 11:43:56 PM by jdallen »
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uniquorn

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Re: The 2019 melting season
« Reply #1159 on: May 27, 2019, 12:00:20 AM »
- that looks like an area of meltponding very near the pole.
I'll stick with maybe. Cloud covered the same area today so it's difficult to say, roughly 84.3n 150e

johnm33

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Re: The 2019 melting season
« Reply #1160 on: May 27, 2019, 12:18:18 AM »
Glen you could start here http://bulletin.mercator-ocean.fr/en/PSY4/animation it's a model thats quite useful. The 'hole' for instance is close to where the inflow of Atlantic and Pacific waters may be interacting as they cross Lomonosov causing turbulence.

Glen Koehler

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Re: The 2019 melting season
« Reply #1161 on: May 27, 2019, 12:30:56 AM »
RE 1158 JDAllen,
RE 1160 johnm33
Thank you gentleman. 
    Sorry for not noticing the forecast forum.  Good stuff.

FWIW 2019 GISTEMP global surface temp is heading for 1.18C above 1850-1900 average, number 2 all time rank, still has a shot at #1.
  Globally, even though ENSO is waning, due to ENSO lag effect on temperature, no major cooling in sight for second half of the year. 

RE context for 3-letter acronym was question I had to answer in order to post.
"Cause of Arctic sea ice melt (3 letters)" = AGW Anthropogenic Global Warming

uniquorn

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Re: The 2019 melting season
« Reply #1162 on: May 27, 2019, 12:37:21 AM »
'Thickest' ice lifted off ellesmere again today.
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FishOutofWater

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Re: The 2019 melting season
« Reply #1163 on: May 27, 2019, 12:47:50 AM »
There's also clockwise rotation with the lift off N of Ellesmere. Meanwhile on the NW coast of Greenland previously landfast ice is heading for the Nares strait. There's almost no landfast ice anywhere on NW Greenland. There used to be very thick ice there.

uniquorn

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Re: The 2019 melting season
« Reply #1164 on: May 27, 2019, 01:06:24 AM »
north whirlpole then ;)

Rod

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Re: The 2019 melting season
« Reply #1165 on: May 27, 2019, 02:25:48 AM »
NASA Worldview just updated with a clear picture of the Beaufort following the cyclone/low pressure system that moved through yesterday. 

I don't see any evidence of refreeze or fresh snowfall.  It looks like the ice was pushed back towards the shore, explaining the extent numbers, but things still look pretty bad. 

Now we will wait and see if the projections for a new high pressure system verify.  If they do, it looks pretty bad for the Beaufort.

petm

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Re: The 2019 melting season
« Reply #1166 on: May 27, 2019, 03:28:50 AM »
things still look pretty bad
Certainly worse than last year and I'd say compared to 2016 as well (May 26 each of these years shown).

Ice Shieldz

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Re: The 2019 melting season
« Reply #1167 on: May 27, 2019, 04:40:07 AM »
This post continues exploring how 2012 compares to our current melt season. Hopefully this will spur discussion or guidance on creating something more helpful.

I realize that insolation is now a much more important factor than DMI 80N-90N air temps. i'd rather substitute the DMI temps with an insolation graph for the Arctic, but i do not even know if such data exist? Also, a 65N to 90N 925mb temp breakdown, like Neven does, would better capture the heat that affects active melt regions south of 80N.



I can't help but notice an apparent huge discrepancy between what PIOMAS reports as average arctic sea ice thickness and what Navy HYCOM+CICE shows. It seems that these two products are on opposite ends of the spectrum. Perhaps reality is somewhere in the middle?



Edit: i now realize these two products are a bit of an apples to oranges comparison with 2012 average PIOMAS thickness being lower because there is more extent to average the thickness across and some of that added extent is thinner ice.
« Last Edit: May 27, 2019, 06:08:33 AM by Ice Shieldz »

Shared Humanity

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Re: The 2019 melting season
« Reply #1168 on: May 27, 2019, 05:14:13 AM »
What is most striking to me in looking at these images is not the comparison between 5/26/2019 and 5/26/2012. It is between 5/26/2019 and the final condition of the ice at the end of the 2012 melt season. Since the end of the 2012 melt season, the thickest ice has continued to disappear. We are only one severe melt season away from a BOE.

Rich

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Re: The 2019 melting season
« Reply #1169 on: May 27, 2019, 06:17:35 AM »
I'm trying to reconcile some understanding here.

The high pressure seems to be a big concern because it's related to a lot of sunshine over the ice at a time when the sun is out nearly all day.

We also know that ice has generally high albedo which means it reflects sunlight without being absorbed.

I'm assuming that concern would be in the areas w/ much less than perfect albedo due to open water, melt pools and spaces between fractured ice.

Is that right?

Looking at the weather forecast, it looks like the predominant area of warmth (above freezing) are on the Russian side seas. The CAB area has a small positive anomaly, but average doesn't look much above freezing, if at all.


BenB

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Re: The 2019 melting season
« Reply #1170 on: May 27, 2019, 09:47:29 AM »
Rich, yes, I believe the general consensus is that sunny weather is mostly a problem where albedo has been lowered - melt ponds, open water, "wet" ice (i.e. where there has been some surface melt), etc., but this is quite a complex issue, as the angle of incidence, water vapour content of the atmosphere, and various other factors all play a part. Over cold ice with high albedo, cloud cover may in some circumstances be "bad" for the ice, by trapping heat and deflecting incoming solar radiation. There was quite a lot of discussion about this topic a few years back - you may be able to find it. Lots of knowledgeable posters citing a variety of scientific papers came to somewhat conflicting conclusions, depending partly on individual interpretations and partly on assumptions about the parameters. If you can't find that discussion, maybe ask the question somewhere else on the forum, as this isn't about the melting season per se.

As a slight tangent, warm, humid air transported into the Arctic can also cause a lot of melt, because cold air holds less water vapour than warm air, so as the air cools, water vapour condenses into liquid water. This change of state releases large amounts of energy.

oren

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Re: The 2019 melting season
« Reply #1171 on: May 27, 2019, 11:02:52 AM »
Rich, the concern is that with 24 hours of near-peak insolation under clear skies the high-albedo snow on top of the ice quickly turns into low-albedo melt ponds. The same applies for pristine ice surfaces becoming wet. Even with high starting albedo, as the temps near zero and the sun climbs in the Arctic sky the ice will not be able to reflect enough of the radiation to avoid this initial melting and conditioning.

Jim Hunt

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Re: The 2019 melting season
« Reply #1172 on: May 27, 2019, 11:11:13 AM »
I'd rather substitute the DMI temps with an insolation graph for the Arctic, but i do not even know if such data exist?

I'm not sure if I've understood your question correctly. But here's an insolation graph:




Rather more complex is Tealight's work on Arctic "Albedo Warming Potential"

Quote
I can't help but notice an apparent huge discrepancy between what PIOMAS reports as average arctic sea ice thickness and what Navy HYCOM+CICE shows. It seems that these two products are on opposite ends of the spectrum. Perhaps reality is somewhere in the middle?

Edit: i now realize these two products are a bit of an apples to oranges comparison with 2012 average PIOMAS thickness being lower because there is more extent to average the thickness across and some of that added extent is thinner ice.

As I've already mentioned, even comparing the US Navy's HYCOM+CICE thickness for 2012 versus 2019 is apples versus oranges.

By way of example, see ACNFS versus GOFS for May 25th 2016:
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be cause

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Re: The 2019 melting season
« Reply #1173 on: May 27, 2019, 11:28:50 AM »
 quoting Oren .. ' as the sun rises in the Arctic sky ' .. At the pole the sun only rises to a max of 23.5% on 21st June . It impresses me that such low angle sunlight melts the snow at all .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 + 1 =  ' if only we could have seen it coming ' ...

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Re: The 2019 melting season
« Reply #1174 on: May 27, 2019, 12:05:36 PM »
quoting Oren .. ' as the sun rises in the Arctic sky ' .. At the pole the sun only rises to a max of 23.5% on 21st June . It impresses me that such low angle sunlight melts the snow at all .. b.c.
I also remember being surprised that the insolation hitting the surface of the earth at 90 degrees North for these two brief months is higher than anywhere else on the northern hemisphere.  It is 24/7 insolation outweighing more intense but shorter daily periods at lower latitudes.

For the next week the Central Arctic is looking pretty dry, that might mean loads of sunshine, helping to transform Albedo Warming Potential into Albedo Warming Actuality.

« Last Edit: May 27, 2019, 12:21:44 PM by gerontocrat »
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Rich

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Re: The 2019 melting season
« Reply #1175 on: May 27, 2019, 12:16:05 PM »
Rich, the concern is that with 24 hours of near-peak insolation under clear skies the high-albedo snow on top of the ice quickly turns into low-albedo melt ponds. The same applies for pristine ice surfaces becoming wet. Even with high starting albedo, as the temps near zero and the sun climbs in the Arctic sky the ice will not be able to reflect enough of the radiation to avoid this initial melting and conditioning.

Thanks for the explanation. You indicate "as temps near zero".

I'm wondering if there is a temperature threshold which must accompany the solar radiation in order for the snow and ice to melt.

The simple layperson understanding is 0C is the threshold which must be close to the temperature at the water / ice interface.

I get that even below zero, the incoming sunlight is warming poor (water) or imperfect albedo surfaces. I'm just trying to get a feel for the comments on this thread which indicate that the current high pressure is a negative indicator on it's own or whether it must be coupled with a certain amount of warmth to really unleash the potential impact.

Thanks to the group for your patience with the questions.

oren

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Re: The 2019 melting season
« Reply #1176 on: May 27, 2019, 12:30:04 PM »
This is somewhat OT here so I will be brief. The most I have ever learned about melting season processes was from watching the O-Buoy real time telemetry movies back around 2016. The buoy takes a photo every hour and it's sped up for watching the whole sequence, which can span 2 years or more. Watch the effects of the date/season, sun and clouds, melt ponds, breakup due to apparent bottom melt, and more.
Rich and everyone else - I strongly recommend taking the time watching the movie, watch all of them, here's a link to one and from there you can browse the whole site.
http://obuoy.datatransport.org/monitor#buoy14/movie

Rich

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Re: The 2019 melting season
« Reply #1177 on: May 27, 2019, 12:43:48 PM »
Thanks for the link Oren.

Jim Hunt

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Re: The 2019 melting season
« Reply #1178 on: May 27, 2019, 12:48:36 PM »
The simple layperson understanding is 0C is the threshold which must be close to the temperature at the water / ice interface.

Since Arctic sea water is salty that threshold is usually quoted as -1.8 Celsius, though it does of course depend upon salinity. This may require a bit of explaining, but here's an animation by SeaIceSailor of the temperatures throughout a melting ice floe, including the air above and the water below it:

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Rich

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Re: The 2019 melting season
« Reply #1179 on: May 27, 2019, 01:14:55 PM »
Thank you Jim. I did find some explanations on the NSIDC site.

Apparently sea ice covered by snow has an albedo of 90%, so the sunlight is going to have an impact regardless. Sea ice has an albedo of 50-70% and ocean is 6%.

Clearly the SST's that accompany the high pressure are important. I'm guessing that's not easy information to come by out in the wilderness of the Arctic Ocean.

Rich

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Re: The 2019 melting season
« Reply #1180 on: May 27, 2019, 01:36:42 PM »
Another question. It's not absolutely clear to me that the the freezing point of salt water (-1.8C) is the same as the melting point of sea ice.

The freezing process separates the salt from the water molecules, no?

The substance being melted is not the same substance which was originally separated and frozen. It seems like the melting point of the fresh water ice should still be 0C.


oren

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Re: The 2019 melting season
« Reply #1181 on: May 27, 2019, 01:41:56 PM »
First year ice is not really fresh. But this should be discussed in detail in a different thread.

uniquorn

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Re: The 2019 melting season
« Reply #1182 on: May 27, 2019, 02:01:49 PM »
Clearer sky over possible melt pond area at roughly 85.3N 96.5E northern laptev/cab. Shown here using worldview terra modis cr367 and unihamburg amsr2uhh, may 25-27

Also from unihamburg is hudson/baffin, may1-27

FishOutofWater

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Re: The 2019 melting season
« Reply #1183 on: May 27, 2019, 02:30:10 PM »
Water vapor is a gas. Air does not hold water vapor. Water vapor is fully miscible in air.

The vapor pressure of water and ice increase non-linearly with temperature. It is a function of the physical properties of the water molecule, not the air around it. One tricky factor is that a parcel of air may become supersaturated with water vapor. Clouds need nuclei to form.

One other tricky factor is that under high pressure domes this time of year  thin low clouds can form over the ice and radiate heat directly down onto the ice. They can act like a white plastic greenhouse. Clouds can have very different effects on the ice depending on their optical thickness, reflectivity, and height.

Sterks

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Re: The 2019 melting season
« Reply #1184 on: May 27, 2019, 03:01:29 PM »
Thank you Jim. I did find some explanations on the NSIDC site.

Apparently sea ice covered by snow has an albedo of 90%, so the sunlight is going to have an impact regardless. Sea ice has an albedo of 50-70% and ocean is 6%.

Clearly the SST's that accompany the high pressure are important. I'm guessing that's not easy information to come by out in the wilderness of the Arctic Ocean.

The physics of salty water freeze / melt / refreeze are really complicated (which does not mean that all those complications make all the ASI meltout phenomena incomprehensible as a whole). I suggest you move to "Stupid Questions" for this and other questions (like that of solar insolation, cloudiness and onset of surface melt, which to this day has notable members of this forum, as AndreasT and Neven, not fully in agreement, correct me if I'm wrong, since it is not a trivial problem). Do not be fooled by the name "Stupid Questions" of that thread. Many of your questions above are really intelligent, they go to the core of many of the sea ice problems, and they really fit that thread where people better intentioned and much more knowledgeable than me will try to answer you eventually.

Shared Humanity

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Re: The 2019 melting season
« Reply #1185 on: May 27, 2019, 03:21:52 PM »
There is still some speculation on the Nares Strait thread about the possibility of the Nares becoming blocked by some of the large floes entering from the Lincoln Sea. That animation lays to waste this particular idea. Some thick MYI from the Lincoln will continue to exit into the Baffin where it will not last the melting season.

b_lumenkraft

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Re: The 2019 melting season
« Reply #1186 on: May 27, 2019, 03:30:39 PM »
Agreed! I'm watching it closely and i don't see a blockage either.

Will post in the Nares Strait thread later today. There is a minor traffic jam right now. I'm only waiting for it to explode with the next tidal wave.

petm

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Re: The 2019 melting season
« Reply #1187 on: May 27, 2019, 03:31:53 PM »
Clearly the SST's that accompany the high pressure are important. I'm guessing that's not easy information to come by out in the wilderness of the Arctic Ocean.

Here is a useful site to monitor daily SSTs: http://ocean.dmi.dk/arctic/satellite/index.uk.php . (It's based on satellite IR; see: http://ocean.dmi.dk/remote_sensing/index.uk.php.)

Ice Shieldz

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Re: The 2019 melting season
« Reply #1188 on: May 27, 2019, 03:57:23 PM »
Jim, thank you for all your clarification and links.

Indeed i should have been more clear about insolation. I was aware of the standard insolation chart but was hoping there was a way to roughly quantify how much insolation reaches the arctic surface during the individual months of a given year/season. Perhaps that might be derived by subtracting the effects of clouds, i.e. scattering, outgoing longwave radiation, etc.  -> Deriving rough surface insolation is well beyond my abilities, so i was hoping others had blazed that trail. Of course like many complex things in the climate, and especially the arctic, i'm sure the answer is not simple.

As I've already mentioned, even comparing the US Navy's HYCOM+CICE thickness for 2012 versus 2019 is apples versus oranges.
Wow, well i wish i would have seen your post before i got underway with my 2012 comparison. In a better world there'd be big disclaimers in the Navy's archive site about these discrepancies. I'm not necessarily blaming the Navy. This lack of clarification around data seems systemic and part of the academic barrier to entry and research specialization. I guess that is why this forum exists - it takes a village to raise climate awareness. Ok that was cheezey. :D

petm

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Re: The 2019 melting season
« Reply #1189 on: May 27, 2019, 04:10:33 PM »
Clearer sky over possible melt pond area at roughly 85.3N 96.5E northern laptev/cab. Shown here using worldview terra modis cr367 and unihamburg amsr2uhh, may 25-27
Do you think these are really melt ponds?

On the one hand, Terra 3-6-7 does detect liquid vs. frozen water (https://earthdata.nasa.gov/faq/worldview-snapshots-faq#modis-367). But on the other hand, the dark shapes look to me more like some kind of cloud, rather than ice topography. They also seem in places to overlap fractures, which doesn't make sense (but may be illusory) (att). They also don't show up on 7-2-1 (att).

If they are indeed melt ponds, they are very extensive (att).

b_lumenkraft

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Re: The 2019 melting season
« Reply #1190 on: May 27, 2019, 04:25:55 PM »
They also seem in places to overlap fractures, which doesn't make sense

Right. If you have a melt pond and the ice cracks you would expect the pond to drain. I see cracks, but no signs of drainage around them.

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Re: The 2019 melting season
« Reply #1191 on: May 27, 2019, 04:36:52 PM »
Plotted the average skin surface temp from May 1-25 for the last 8 years. Sorry about the resolution, I was trying to save space.  2012 is upper left, 2019 lower right.
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b_lumenkraft

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Re: The 2019 melting season
« Reply #1192 on: May 27, 2019, 05:03:06 PM »
North Northwest Greenland. Ice is moving quite quickly clockwise with the central pack. This is a GIF showing only 8.5 hours, from 27.12. 03:34 to 12:02h UTC.

(Click it, you know.)

FishOutofWater

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Re: The 2019 melting season
« Reply #1193 on: May 27, 2019, 05:08:11 PM »
I looked at one of those dark orange features on consecutive days and it moved with the ice pack in exactly the same location relative to the visible fractures. Note that melt ponding is on a smaller scale than the fracturing. What ever is causing it, it's not a stationary cloud shadow over the ice. The cloud shadows did not persist from one day to the next.

jdallen

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Re: The 2019 melting season
« Reply #1194 on: May 27, 2019, 05:19:51 PM »
They also seem in places to overlap fractures, which doesn't make sense

Right. If you have a melt pond and the ice cracks you would expect the pond to drain. I see cracks, but no signs of drainage around them.
You need to remember you are looking at a map where the smallest resolution objects are 500m across.

The surface of all that ice is also far from regular - with pressure ridges, uneven thickness and every other imaginable imperfection.  There are lots of potential catchements for melt water.  Those cracks won't drain the ice the way a watershed would, by any means.
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Shared Humanity

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Re: The 2019 melting season
« Reply #1195 on: May 27, 2019, 05:21:17 PM »
Plotted the average skin surface temp from May 1-25 for the last 8 years. Sorry about the resolution, I was trying to save space.  2012 is upper left, 2019 lower right.

That doesn't look good.

jdallen

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Re: The 2019 melting season
« Reply #1196 on: May 27, 2019, 05:25:19 PM »
Clearer sky over possible melt pond area at roughly 85.3N 96.5E northern laptev/cab. Shown here using worldview terra modis cr367 and unihamburg amsr2uhh, may 25-27
Do you think these are really melt ponds?

On the one hand, Terra 3-6-7 does detect liquid vs. frozen water (https://earthdata.nasa.gov/faq/worldview-snapshots-faq#modis-367). But on the other hand, the dark shapes look to me more like some kind of cloud, rather than ice topography. They also seem in places to overlap fractures, which doesn't make sense (but may be illusory) (att). They also don't show up on 7-2-1 (att).

If they are indeed melt ponds, they are very extensive (att).
Insolation and surface air temperatures have been plenty high enough to generate melt across the entire region.

Some of it also may be sub-aerial at the base of snow pack on top of the ice.

Also keep in mind, top-surface melting of snow pack concentrates particulates and significantly reduces the albedo of snow.
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b_lumenkraft

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Re: The 2019 melting season
« Reply #1197 on: May 27, 2019, 05:29:37 PM »
You need to remember you are looking at a map where the smallest resolution objects are 500m across.

That's a very good point. Thanks for reminding me.

BenB

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Re: The 2019 melting season
« Reply #1198 on: May 27, 2019, 06:13:48 PM »
Water vapor is a gas. Air does not hold water vapor. Water vapor is fully miscible in air.

I'm sorry if I was being slightly informal in my explanation to Rich. Obviously water vapour is a gas and hence part of the air. But the maximum amount of water vapour in a given parcel of air is dependent on temperature, see e.g.:

https://www.engineeringtoolbox.com/humidity-ratio-air-d_686.htm
https://earthscience.stackexchange.com/questions/13511/how-would-i-use-data-to-find-specific-humidity-and-mixing-ratio

Therefore, in practice, when warm, saturated air cools, some of the water vapor in it condenses, releasing energy. This can and does melt snow and ice, and is something that is often seen in spring melting conditions. I know you know far more about meteorology than I do, so I'm not trying to inform you, but just clarify my point, in case anyone else is interested.

petm

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Re: The 2019 melting season
« Reply #1199 on: May 27, 2019, 06:16:35 PM »
Right. If you have a melt pond and the ice cracks you would expect the pond to drain. I see cracks, but no signs of drainage around them.
This is what I was thinking too.

You need to remember you are looking at a map where the smallest resolution objects are 500m across.
And this is why I said it might be illusory.

I looked at one of those dark orange features on consecutive days and it moved with the ice pack in exactly the same location relative to the visible fractures. Note that melt ponding is on a smaller scale than the fracturing. What ever is causing it, it's not a stationary cloud shadow over the ice. The cloud shadows did not persist from one day to the next.
This is a very good point.

Taken together, personally I'm on the fence but leaning towards real. How unusual or not would it be to have such extensive melt ponding so far into the pack at this time of year?