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jdallen

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Re: The 2016 melting season
« Reply #3550 on: July 21, 2016, 08:00:16 PM »
The current DMI 80ºN suggests high latitude cooling of late - not good for supporting the continuation of the unprecedented early CAB ice loss.
High latitude cooling could also be a sign of more open, -1.8C water, rather than a reduction in heat transfer.
Ahh, thanks jdallen.  I basically thought there could be more than one reasonable explanation when I first wrote, so didn't then mention the previous idea that had crossed my mind.  In reality, of course, there will be multiple influences for the reported temperature drop (yes, Quantum, if it means much in the first place) and overlapping influences for the reported SIA loss.  Thanks for y'all's sharing.  (I've lived in the U.S.A's South too long, but in too many other places to just say "the South".)
Just so; the reason I suggested only struck *me* because I'd just finished mulling over A-Team and other folks posts and animations looking at the dispersal and increased fragmentation across most of the remaining ice.

Ice doesn't transfer heat all that well, and in effect at this time of year to some degree insulates the *air* from the heat sink that is the top layers of the arctic ocean.  Seemed to me, less ice means more heat uptake, and as by comparison the net enthalpy of atmosphere is so puny compared to that of water, lower 80N temps seem from that seem like a slam dunk.

It seems most likely as well for other reasons. The storms we've had have transferred a *lot* of heat north from lower latitudes, both sensible and implied by moisture content.  I've not gotten a sense of it being as cloudy or foggy as things were in 2013/2014 by any stretch, so at a qualitative level looking at things systemically, I'm not seeing a good alternative explanation as to where the heat might be going instead.  Caveat: the atmosphere is far more sensitive to modest changes in heat movement than the ice or water, so I could easily be missing something.

Another two weeks and the radiative balance will start decaying geometrically, and this will no longer be the case for sure.
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Jim Hunt

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Re: The 2016 melting season
« Reply #3551 on: July 21, 2016, 08:37:24 PM »
Surely you never really thought you had proven anything?

Anybody who bothered to click my link to Worldview on the morning I posted it and then 24 hours later could have proved to themselves that the displayed image had changed.
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seaicesailor

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Re: The 2016 melting season
« Reply #3552 on: July 21, 2016, 08:55:20 PM »
... Without that, declines in area and extent rely on bottom melt, which even with the extra heat retained by the anemic refreeze last winter, I do not think will be severe enough to seriously impact the CAB.  ...

I disagree on that. Apart from compaction, bottom melting is not going to cease until Fall November at least around most of the Arctic ocean, and from this other in-situ witness, it may get its 'bloody satisfaction'.
2015F has been located in an area where nothing but coldness happened until end of June. No broken ice, no surface melting. I attach the thickness profiles and the location marked in today's worldview images, terra modis (7-2-1).
Bottom melting is running wild now. I think it is not because of the recent effect of storm since it already started earlier. It is because a generous number of days passed with temperatures around 0C.
If this buoy, in this relatively protected area, is seeing this bottom melt at this 83N of latitude, imagine what to expect south of 80N. Caveat, it is just one location.
What about bottom melt in all these low concentration areas within in CAB after all? mmm We'll see.
This sudden melt rate is really surprising to me.
Edit: could it be that the buoy is located very close to a recent fracture? Otherwise I don't see how bottom melting rate can go off suddenly like that
« Last Edit: July 21, 2016, 09:43:46 PM by seaicesailor »

RoxTheGeologist

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Re: The 2016 melting season
« Reply #3553 on: July 21, 2016, 08:59:46 PM »

Just so; the reason I suggested only struck *me* because I'd just finished mulling over A-Team and other folks posts and animations looking at the dispersal and increased fragmentation across most of the remaining ice.

Ice doesn't transfer heat all that well, and in effect at this time of year to some degree insulates the *air* from the heat sink that is the top layers of the arctic ocean.  Seemed to me, less ice means more heat uptake, and as by comparison the net enthalpy of atmosphere is so puny compared to that of water, lower 80N temps seem from that seem like a slam dunk.

It seems most likely as well for other reasons. The storms we've had have transferred a *lot* of heat north from lower latitudes, both sensible and implied by moisture content.  I've not gotten a sense of it being as cloudy or foggy as things were in 2013/2014 by any stretch, so at a qualitative level looking at things systemically, I'm not seeing a good alternative explanation as to where the heat might be going instead.  Caveat: the atmosphere is far more sensitive to modest changes in heat movement than the ice or water, so I could easily be missing something.

Another two weeks and the radiative balance will start decaying geometrically, and this will no longer be the case for sure.

I have a question. It came about really because of A-Team noticing the coincidence of the Continental slope and the ice boundary in the Atlantic/Arctic.

From my (limited) reading, one of the driving mechanisms of the Arctic is the flow of saline warm Atlantic waters into the Arctic. They flow to form a layer below the cold fresh waters on the surface. That produces a stable halocline across the Arctic.

However, with little winter ice in the Barents, the Atlantic Waters layer is likely to be both warmer and less salty than usual. Wouldn't that reduce the depth of the Halocline, and make it easier for heat to diffuse (or be mixed) into the stable upper fresher but much colder water? My hypothesis is that it would produce basin wide changes over the long term, as it takes a while for Atlantic Water to circulate all the way to the Beaufort.

I was looking at this model:
http://journals.ametsoc.org/doi/full/10.1175/JPO-D-13-079.1

Michael Hauber

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Re: The 2016 melting season
« Reply #3554 on: July 21, 2016, 09:31:37 PM »
Despite the recent storm activity, overall 925 hp temps have been running quite warm.  While this heat wave is not as extreme as 2011 or as long running as 2007 or 2015, its turning into one of the more significant heatwaves that have been experienced.  And at the same time we've had some significant storm activity.  Perhaps even though 925hp temps have been high, increased cloud may have made the melting conditions less severe.  Otherwise I'd say this would count as one of the most extreme melting weather set ups in recent years.
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epiphyte

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Re: The 2016 melting season
« Reply #3555 on: July 21, 2016, 09:48:04 PM »
Despite the recent storm activity, overall 925 hp temps have been running quite warm.  While this heat wave is not as extreme as 2011 or as long running as 2007 or 2015, its turning into one of the more significant heatwaves that have been experienced.  And at the same time we've had some significant storm activity.  Perhaps even though 925hp temps have been high, increased cloud may have made the melting conditions less severe.  Otherwise I'd say this would count as one of the most extreme melting weather set ups in recent years.

Concur - viz the 850mb temp animations on nullschool are showing well above freezing over much of laptev/kara right now - and forecast the same for the next few days. Subjectively, from catching the odd glimpse of what's going on underneath the clouds in that area, the ice isn't looking all that good a bet to survive through the minimum.

jdallen

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Re: The 2016 melting season
« Reply #3556 on: July 21, 2016, 09:54:00 PM »

<snippage>

From my (limited) reading, one of the driving mechanisms of the Arctic is the flow of saline warm Atlantic waters into the Arctic. They flow to form a layer below the cold fresh waters on the surface. That produces a stable halocline across the Arctic.

However, with little winter ice in the Barents, the Atlantic Waters layer is likely to be both warmer and less salty than usual. Wouldn't that reduce the depth of the Halocline, and make it easier for heat to diffuse (or be mixed) into the stable upper fresher but much colder water? My hypothesis is that it would produce basin wide changes over the long term, as it takes a while for Atlantic Water to circulate all the way to the Beaufort.


The article unfortunately didn't open, but I'll speculate a bit at a high level.

First off, I'd say this: 
Quote
... Atlantic Waters layer is likely to be both warmer and less salty than usual...

... doesn't necessarily follow the premise condition.

If you look at HYCOM's SSS map (admittedly a model, but good for illustration), salinity in the Barents really hasn't changed that dramatically over time.

http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticsss_nowcast_anim365d.gif

... so by extention, I don't think salinity changes will produce much in the way of change in the water column generally.
 
Add to that, most of the energy being transported from the Atlantic to the arctic via current actually comes from much further south in the tropics and mid latitudes - which also generally determines the salinity of the water moving northward.  This has been and still remains far saltier than arctic water, and is more likely to be come more rather than less salty (increased evaporation due to heat), so even the initial premise is probably flawed.

What does disrupt the water column really is weather and wind applied to the surface, which results in Ekman pumping that causes circulation from depth potentially disrupting halo and thermoclines.

With a more mobile, fractured pack that most certainly is much more of a factor than salinity.

This whole discussion causes me to lament even more the loss of active buoys that's taken place over the last two seasons.  I feel like we're blind.
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jdallen

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Re: The 2016 melting season
« Reply #3557 on: July 21, 2016, 09:59:06 PM »
Despite the recent storm activity, overall 925 hp temps have been running quite warm.  While this heat wave is not as extreme as 2011 or as long running as 2007 or 2015, its turning into one of the more significant heatwaves that have been experienced.  And at the same time we've had some significant storm activity.  Perhaps even though 925hp temps have been high, increased cloud may have made the melting conditions less severe.  Otherwise I'd say this would count as one of the most extreme melting weather set ups in recent years.

Concur - viz the 850mb temp animations on nullschool are showing well above freezing over much of laptev/kara right now - and forecast the same for the next few days. Subjectively, from catching the odd glimpse of what's going on underneath the clouds in that area, the ice isn't looking all that good a bet to survive through the minimum.
I'm keen to see better glimpses of the Laptev (and ESS...) as well.  There's been some tanalizing partial images showing conditions that remind me of what happens in the Bering and southern Chukchi in May - progressive disintegration of ice into smaller and smaller floes with progressive browning/graying of the ice as more surface melt and algae growth takes hold, followed by a 3-5 day period of prompt melt turning the whole mess into a network of thin streamers of slash ice.

If it happens, it may overthrow my current conservative take on where the melt season is headed.
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slow wing

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Re: The 2016 melting season
« Reply #3558 on: July 21, 2016, 10:09:02 PM »
If the skies were sunny, that energy source would be obvious.

Glancing at Worldview images, we are getting pretty good looks at the ice (such as it is) lately.
The Sun must be getting similar looks . . .
Yep, this is a good point. If we can see the ice then the sun can as well. Thin clouds can also be effective in blocking upward thermal radiation while also allowing in much of the sunlight. So I consider it uncertain whether this year's cloud cover is more beneficial than usual for preserving the ice.

As to whether the ice is too cold this year, Wipneus' plot of melt pond fraction shows this year has as big a fraction of melt ponds as in the previous years covered, namely 2013-15.

So the evidence is not convincing to me that this year is collecting significantly less heat from the sun than in previous years.
« Last Edit: July 21, 2016, 10:24:34 PM by slow wing »

Tigertown

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Re: The 2016 melting season
« Reply #3559 on: July 21, 2016, 11:37:15 PM »
When you see that blue tint in the Beaufort or elsewhere, it means insolation is cranking in high gear. The water absorbs the other wave lengths easier than the blue.
« Last Edit: July 21, 2016, 11:50:04 PM by Tigertown »

magnamentis

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Re: The 2016 melting season
« Reply #3560 on: July 22, 2016, 12:20:35 AM »
The current DMI 80ºN suggests high latitude cooling of late - not good for supporting the continuation of the unprecedented early CAB ice loss.

yes, but then the other source shows another picture and in case of doubt i first doubt DMI, just got that feeling over time that accuracy is not at max there.

« Last Edit: July 22, 2016, 12:26:01 AM by magnamentis »

Michael Hauber

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Re: The 2016 melting season
« Reply #3561 on: July 22, 2016, 12:45:24 AM »
2016 vs 2012

Looks like similar wide spread dispersal of ice.  The two views are roughly aligned with the Laptev/Kara boundary in the top right.  The left side is tilted more towards Siberia in 2012, and more towards Canada in 2016.  Its yesterday's view as a clearer day in 2012 allows a better comparison.  The weak ice is closer to the pole this year, which in my opinion means it is less likely to melt out (consider 2013, although it is definitely warmer this year than 2013).  Also the Laptev/Kara area is an area that 2016 is seriously lagging behind.  A good view of fairly solid looking ice in that region this year, but hard to see under the clouds in 2012.  The view on the 24th Jul 2012 gives a pretty good hint.

Comparing ADS views for same date to 2008 suggests that the Siberian tongue may find it hard to survive, melt in the Beaufort and Laptev is well advanced on 2008 and the Siberian tongue was close to totally melted out that year.  Comparing to same date in 2007 we seem to have about the same amount of ice near the Laptev/Kara boundary as 2007.  In 2007 we saw ice persist right until minimum keeping the NE passage closed.  I'm not sure we'll see a repeat of a blocked NE passage this year, but I think whatever opening we manage will be late and narrow.
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Re: The 2016 melting season
« Reply #3562 on: July 22, 2016, 12:54:11 AM »
This is probably too basic for most of you here but since there was talk of salinity before I thought it might help someone else as it helped me.  There is a pretty cool interactive animation of ice and water molecules and the effect of salt.

http://antoine.frostburg.edu/chem/senese/101/solutions/faq/why-salt-melts-ice.shtml
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JayW

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Re: The 2016 melting season
« Reply #3563 on: July 22, 2016, 12:58:08 AM »
Edit: my only commentary is that I find the "flow" to the north/northeast of Wrangel island fun. :)

~54 hour loop, July 19-21, the big storm can be seen exiting in the Iower right corner.  Alaska at the bottom as usual.

Images courtesy of the university of Alaska at fairbanks.
http://feeder.gina.alaska.edu/search?utf8=✓&search%5Bsensors%5D%5B4%5D=1&search%5Bsensors%5D%5B3%5D=1&search%5Bfeeds%5D%5B5%5D=1&search%5Bstart%5D=&search%5Bend%5D=&commit=Search
« Last Edit: July 22, 2016, 01:11:19 AM by JayW »
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Rob Dekker

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Re: The 2016 melting season
« Reply #3564 on: July 22, 2016, 08:42:17 AM »
Bottom melting is running wild now. I think it is not because of the recent effect of storm since it already started earlier. It is because a generous number of days passed with temperatures around 0C.
If this buoy, in this relatively protected area, is seeing this bottom melt at this 83N of latitude, imagine what to expect south of 80N. Caveat, it is just one location.
What about bottom melt in all these low concentration areas within in CAB after all? mmm We'll see.
This sudden melt rate is really surprising to me.
Edit: could it be that the buoy is located very close to a recent fracture? Otherwise I don't see how bottom melting rate can go off suddenly like that

Thanks for bringing up this issue of bottom melt on buoy 2015F, seaicesailor.
For reference, this is the profile you presented :



I mentioned before that 2015F is an excellent source to investigate the less common forms of bottom-melt : heat conduction and sunlight shining through the ice.

For many such issues, I like to get a ballpark estimate by using basic physics.

For that, let us make a rough estimate about how much heat is causing bottom-melt on that buoy right now. The thickness data on the buoy is a bit erratic, but I would say that over the past 14 days, 20 cm of bottom-melt happened (please correct me if you think otherwise).

20cm bottom-melt over 14 days is 1.4 cm/day which suggests that somehow some 50 W/m^2 of heat reached the bottom (50 W/m^2 *3600*24/330000 = 13 kg/m^2/day = 1.3 cm/day).

Heat conduction through the ice (with surface at 0C and bottom at -1.8C) is negligible : with ice heat conduction of 2 W/m/K, through 1 meter ice gives 4 W/m^2. Less for this 1.8 m thick floe. So that's not it.

What is more likely is that the sunlight is shining THROUGH the ice, and causing bottom-melt that way. At this time, insolation is still high (some 400 W/m^2 for open skies, 200 W/m^2 average) and thus if 25% of the sunlight goes through the ice, we could explain 2015F's bottom melt.

Note that this bottom melt rate started to occur only after the snow melted. That suggests this effect of sunlight through the ice is indeed contributing to the bottom melt rate observed, but I must admit that the melt rate is still a bit steep. After all, sunlight that goes through the ice (even if it is 25 % of incident insolation) will also warm the water well below the ice, and thus not all of that light energy immediately goes to bottom melt, but instead some of that will cause bottom-melt much later (all the way into fall).

So even though "light shining through the ice" appears to be a serious candidate in explaining 2015F's bottom-melt, there may be a third mechanism at play. Maybe there are some leads around this floe. Or some upwelling that just started happening recently.

Let me know your thoughts, and either way, let us keep a close eye on this buoy and the bottom melt it is recording.

[edit] On second thought, since the snow on this floe melted, it will have an albedo of about 0.4 or 0.5 at best, so it will absorb half of insolation (which will be about 100 W/m^2 for average weather). If half of that goes to top-melt and half to bottom-melt it would explain the melt rate of this buoy quite nicely.
« Last Edit: July 22, 2016, 09:06:43 AM by Rob Dekker »
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Tigertown

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Re: The 2016 melting season
« Reply #3565 on: July 22, 2016, 08:59:48 AM »
Just a completely wild theory, but with other oceans seeing record, unprecedented temperatures, maybe currents are transporting some fraction of that energy to the Arctic. Might not be much by itself, but combined with more local insolation, it could add up.

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Re: The 2016 melting season
« Reply #3566 on: July 22, 2016, 09:11:19 AM »
Rob, light transmission is a significant source of energy for bottom  melt, in some places the dominant one as your figures show.
The AWI has done much work on this, here is an example: http://epic.awi.de/38685/1/katlein_2015_JGR_ice_thickness_and_surface_properties.pdf
The start of bottom melt as snow cover goes is a feature seen in many IMB measurements, there is a data archive for buoys which are no longer active.

Rob Dekker

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Re: The 2016 melting season
« Reply #3567 on: July 22, 2016, 09:11:29 AM »
Could be, Tigertown, and we sure see the effect of that on the Atlantic front.
But for this particular floe at 83N, in the middle of the Arctic Basin, ocean heat input is probably negligible. Either way, it would be a remarkable coincidence that ocean heat transport started to be significant for buoy 2015F exactly when the snow cover melted out at the top of the ice at that buoy location.
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Rob Dekker

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Re: The 2016 melting season
« Reply #3568 on: July 22, 2016, 09:18:55 AM »
Rob, light transmission is a significant source of energy for bottom  melt, in some places the dominant one as your figures show.
The AWI has done much work on this, here is an example: http://epic.awi.de/38685/1/katlein_2015_JGR_ice_thickness_and_surface_properties.pdf
The start of bottom melt as snow cover goes is a feature seen in many IMB measurements, there is a data archive for buoys which are no longer active.

Thanks Andreas !
I'll read that article in more detail, specifically to see if they can confirm (or deny) that some 25-50% of sunlight goes through the ice. If not, then we still have to look for other mechanisms by which 2015F obtains its bottom melting rate.
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Tigertown

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Re: The 2016 melting season
« Reply #3569 on: July 22, 2016, 09:41:27 AM »
Could be, Tigertown, and we sure see the effect of that on the Atlantic front.
But for this particular floe at 83N, in the middle of the Arctic Basin, ocean heat input is probably negligible. Either way, it would be a remarkable coincidence that ocean heat transport started to be significant for buoy 2015F exactly when the snow cover melted out at the top of the ice at that buoy location.
 
Most likely insolation combined with freshly stirred waters,therefore. There are spots near that area showing up a fraction of a degree higher than normal in recent days, at least anomaly wise. Some of these spots are close, maybe not dead on. This is a few days old as I could not find anything with this much detail that was newer. This at least shows insolation is taking place in the deep Arctic. I have read so many articles lately to the end that clouds are changing altitude wise and not blocking the sun as effectively as well.Just Google Scripps cloud studies.
« Last Edit: July 22, 2016, 09:55:20 AM by Tigertown »

Rob Dekker

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Re: The 2016 melting season
« Reply #3570 on: July 22, 2016, 10:04:40 AM »
OK. I read Andreas reference to Katlein et al 2015.
For the relevance of "sunlight through the ice" I read :
Quote
Light transmittance was between 0.02 and 0.10
along the transect:
and their fig 3 sustains that.
Note that their floe is 1.6 meter thick, which is comparable to the floe that 2015F is installed on.

Noting that not all of that heat goes to bottom-melt, 2-10% of incoming light is not enough to explain the bottom melt rate in buoy 2015F.

So either I did not estimate 2015F's melting rate correctly, or the cause of bottom-melt in 2015F is not predominantly "light through the ice" or the measurements of Katlein et al are not representative of the situation around buoy 2015F or there is another source of heat not accounted for.

Again, let us keep an eye on 2015F and see what bottom melt is doing there over the next week or so.
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Rob Dekker

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Re: The 2016 melting season
« Reply #3571 on: July 22, 2016, 10:20:23 AM »
Katlein et al also states :
Quote
Extracted albedo values lie between 0.3 and 0.6.
which (with transmittance through the ice at less that 10%) suggests that most of heat gets absorbed into the ice.
How that leads to significant bottom-melt compared to top-melt is still a question that remains unanswered...
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Jim Hunt

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Re: The 2016 melting season
« Reply #3572 on: July 22, 2016, 10:25:54 AM »
If not, then we still have to look for other mechanisms by which 2015F obtains its bottom melting rate.

Here are the latest temperature profiles for 2015F:

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/summer-2016-imbs/#2015F-Temp

Bear in mind that the buoy is one of the new style "seasonal" ice mass balance buoys (SIMB for short). At this time of year they have a tendency to create their own "mini melt ponds", so the sensor readings perhaps need to be taken with a pinch of salt. SIMBs seem to "melt out" of their installation hole long before the floe on which they're installed finally melts away.

The July 21st profile seems to me to reveal melt water already descending down 2015F's installation hole.

« Last Edit: July 22, 2016, 10:32:42 AM by Jim Hunt »
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Rob Dekker

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Re: The 2016 melting season
« Reply #3573 on: July 22, 2016, 10:33:09 AM »
Thanks Jim,
Yes, I noticed that "installation melting pond hole" also in some of the Obuoy's from 2011 and 2012.
So I agree that is a factor to be considered.
But with that effect, the albedo of the surface will be on the lower end (0.2 - 0.3 or so) and transmittance through the ice will be at the higher end (0.1 or so).
That still would suggest that top melt would be 2-3x larger than bottom-melt, which seems NOT to be the case for 2015F. Quite the opposite, actually.
« Last Edit: July 22, 2016, 10:38:23 AM by Rob Dekker »
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Jim Hunt

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Re: The 2016 melting season
« Reply #3574 on: July 22, 2016, 10:37:26 AM »
That still would suggest that top melt would be 2-3x larger than bottom-melt, which seems NOT to be the case for 2015F. Quite the opposite, actually.

Bear in mind that by now the "ice surface sensor" will probably be acting as a "water surface sensor" instead.
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Rob Dekker

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Re: The 2016 melting season
« Reply #3575 on: July 22, 2016, 10:44:01 AM »
That still would suggest that top melt would be 2-3x larger than bottom-melt, which seems NOT to be the case for 2015F. Quite the opposite, actually.

Bear in mind that by now the "ice surface sensor" will probably be acting as a "water surface sensor" instead.

Good point.
Looking at the 2015F thermistor profile you presented above, it seems that up till thermistor 8 or 9 is above freshwater melting point of 0C. Suggesting it is sitting in a melting pond indeed.
Do you know how far these thermistors are separated on that buoy ?
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Re: The 2016 melting season
« Reply #3576 on: July 22, 2016, 10:55:45 AM »
Bear in mind that the buoy is one of the new style "seasonal" ice mass balance buoys (SIMB for short). At this time of year they have a tendency to create their own "mini melt ponds"...

Is it possible that some of the melt water leaks through the buoy hole and melts ice directly next to it? When I look at the sketch than the acoustic sounder measures the ice thickness exactly in that spot.



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Re: The 2016 melting season
« Reply #3577 on: July 22, 2016, 12:24:58 PM »
Yes, clearly discarded heat conduction which is what I thought first; that is responsible only of the gradual start and increase of bottom melting from second half of June. Also the up-welling or a underneath current given how simultaneous is the removal of snow with the shooting up.
I would also discard a crack or lead nearby. What are the chances? From the Healy images, the chances would be small even in the broken area of Chukchi since the floes are typically tens of meters wide.
Jim, the profiles are very revealing. There is also a rocketing of temperatures toward 0C throughout the entire thickness from Jul 1 to Jul 11. If most of the sunlight heat gets absorbed by the ice, maybe that could be it.
I don't want to believe the cause is surface water, buoy installation related... just because it would be a real pity (to lose this buoy I mean)

Jim Hunt

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Re: The 2016 melting season
« Reply #3578 on: July 22, 2016, 12:37:14 PM »
Do you know how far these thermistors are separated on that buoy ?

Actually Tealight has now answered that! 10 cm.

Some close-ups of SIMBs in situ:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA532414
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Jim Hunt

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Re: The 2016 melting season
« Reply #3579 on: July 22, 2016, 12:45:46 PM »
There is also a rocketing of temperatures toward 0C throughout the entire thickness from Jul 1 to Jul 11. If most of the sunlight heat gets absorbed by the ice, maybe that could be it.

Bottom melt is conspicuous largely by its absence until the floe has warmed to above the temperature of the water it is floating on. Once that has happened and there's a melt pond on the surface the ice can disappear comparatively quickly. By way of example, here's the world famous 2006C:
« Last Edit: July 22, 2016, 12:51:15 PM by Jim Hunt »
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Mark Tough

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Re: The 2016 melting season
« Reply #3580 on: July 22, 2016, 01:56:36 PM »
Hi Everyone,

I know off topic - but please point me to the right direction to post this.

https://www.sciencedaily.com/releases/2016/07/160721164201.htm

It's an interesting paper that I've seen the bones of here so many times before but basically the historic record has been skewed by 20% on the downside. It really says the models are spot on! Well to date that is - what feedbacks and unknowns we have to look forward to are why we keep coming here :)

Have fun boys and girls!

Andreas T

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Re: The 2016 melting season
« Reply #3581 on: July 22, 2016, 02:15:01 PM »
Katlein et al also states :
Quote
Extracted albedo values lie between 0.3 and 0.6.
which (with transmittance through the ice at less that 10%) suggests that most of heat gets absorbed into the ice.
How that leads to significant bottom-melt compared to top-melt is still a question that remains unanswered...
There is another paper showing data from Aug 2011 which gives a value of 0.22 for transmission under meltponds and 0.53 for absorption for average meltponded ice. The irradiance values are surprisingly small, but this is August.
http://epic.awi.de/31931/1/nicolaus-2012-grl_2012GL053738.pdf
Stefan Hendricks has commented here in the past maybe he could help us with more information or pointers to accessible publications?

Your comment about bottom/ surface melt overlooks that the surface is where longwave IR is emitted. So if shortwave is absorbed gradually throughout the ice your source terms for input are distributed but net outgoing balance is coming from the surface. So an net input of SW will, near  the surface,  make up a net output of IR while near the bottom all incoming energy is available for melt. There is also the question of melt throughout the ice and flushing of water through brine channel from top to bottom which would make heat flux down wards stronger than upwards for the same temperature gradient.
These are guesses based on my understanding of the physics.

Quantum

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Re: The 2016 melting season
« Reply #3582 on: July 22, 2016, 02:41:40 PM »
Its quite amazing that in late june the ice looked like it was going to pull away from the north American coast. Yet here we are on the 22nd of July and there are still some ice flows on the coast near barrow. Truly astounding and something I don't think any of us would have predicted.

NeilT

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Re: The 2016 melting season
« Reply #3583 on: July 22, 2016, 05:15:54 PM »
I don't think any of us would have predicted.

Back on May 27th I predicted that we were following 2006 and that we would have weak June melt.

On June 30th I predicted it would follow the 2006 event with stronger but still not strong forcing for melt but that the actual melt would be much greater than we saw in 2006 due to the state of the ice.

Nearly a month later I predict we'll finish in, or very close to, the top 3 because of the incredibly weak state of the ice and the fact that the storms are tearing it up in the heart of the CAB where we would not have expected open water before and, if it continues to follow the 2006 general trend, there will be good melting weather in August to take advantage of it.

It's not scientific but it is somewhat accurate this year so far.

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Neven

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Re: The 2016 melting season
« Reply #3584 on: July 22, 2016, 05:27:02 PM »
Yup, you've had a good feel for this melting season so far, Neil. Well done.
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Re: The 2016 melting season
« Reply #3585 on: July 22, 2016, 05:36:58 PM »
Its quite amazing that in late june the ice looked like it was going to pull away from the north American coast. Yet here we are on the 22nd of July and there are still some ice flows on the coast near barrow. Truly astounding and something I don't think any of us would have predicted.

We should continue to remember that this year some of the ice area from the Central Arctic Basin has likely been pushed out into the peripheral regions (see the attached plot).
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Re: The 2016 melting season
« Reply #3586 on: July 22, 2016, 05:45:22 PM »
Its quite amazing that in late june the ice looked like it was going to pull away from the north American coast. Yet here we are on the 22nd of July and there are still some ice flows on the coast near barrow. Truly astounding and something I don't think any of us would have predicted.

After breakout it's cleared a couple of time only to have more ice fragments being blown back inshore.  Not good for the ice though since it's entering warmer areas so will melt away.  The ice blown up on the shore today is exposed to an air temperature of 43ºF.

jai mitchell

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Re: The 2016 melting season
« Reply #3587 on: July 22, 2016, 06:04:17 PM »
Mark,

I put the article under "Consequences" in the thread, "Conservative Scientists and its Consequences"

good find!
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Nightvid Cole

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Re: The 2016 melting season
« Reply #3588 on: July 22, 2016, 09:05:25 PM »
The ice looks like Swiss cheese on the Siberian side, to quite deep into the interior of the ice pack.

https://ads.nipr.ac.jp/vishop/#/monitor

Choose the RGB option under "product selection", and select July 21, 2016. Note that you can compare to other years on this date. Usually the Swiss cheese-ice at this time of year will be gone in mid-September. If this year follows that rule, it will end up much like 2012, maybe even a little worse. Time will tell...
« Last Edit: July 22, 2016, 09:24:56 PM by Nightvid Cole »

JayW

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Re: The 2016 melting season
« Reply #3589 on: July 22, 2016, 10:45:49 PM »
Relatively clear skies north of Alaska, so I tacked on another 24 hours to the animation in post #3563.

July 19-22
http://feeder.gina.alaska.edu/search?utf8=✓&search%5Bsensors%5D%5B4%5D=1&search%5Bsensors%5D%5B3%5D=1&search%5Bfeeds%5D%5B5%5D=1&search%5Bstart%5D=&search%5Bend%5D=&commit=Search

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magnamentis

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Re: The 2016 melting season
« Reply #3590 on: July 22, 2016, 11:22:33 PM »
Its quite amazing that in late june the ice looked like it was going to pull away from the north American coast. Yet here we are on the 22nd of July and there are still some ice flows on the coast near barrow. Truly astounding and something I don't think any of us would have predicted.

that's totally depending on the wind patterns, that coast was ice free and the current small floes were blown in by the winds and are going to melt within a few days at current temps. however, each bit of ice that shows up there has been taken from somewhere else, hence is "missing" elsewhere :-) ( so to say )

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Re: The 2016 melting season
« Reply #3591 on: July 23, 2016, 12:43:25 AM »
Warmer waters of Baffin Bay waiting for the doors to open:

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Re: The 2016 melting season
« Reply #3592 on: July 23, 2016, 09:04:52 AM »
There is another paper showing data from Aug 2011 which gives a value of 0.22 for transmission under meltponds and 0.53 for absorption for average meltponded ice. The irradiance values are surprisingly small, but this is August.
http://epic.awi.de/31931/1/nicolaus-2012-grl_2012GL053738.pdf
Stefan Hendricks has commented here in the past maybe he could help us with more information or pointers to accessible publications?

Thanks Andreas. That number (0.22) for short-wave transmittance through melting ponds is much closer to the (0.25) transmittance I calculated from the 2015F bottom melt rate.
That is another indication that 2015F is sitting in a melting pond (maybe a self-created melting pond as Jim Hunt suggested).

The previous number (0.11) appeared to be for the average for FYI floes, as is confirmed by your new paper (Nicolaus et al) :

Quote
. Our results show that transmittance through first-year ice (FYI, 0.11) was almost three times larger than through multi-year ice (MYI, 0.04), and that
this is mostly caused by the larger melt-pond coverage of FYI (42 vs. 23%).

All this said, we can now make an educated estimate for top and bottom melt at 2015F :
- insolation 200 W/m^2 for average weather, with 0.53 (100 W/^2) absorption and 0.22 (44 W/m^2) transmission.
That suggests top-melt rate of 2.6 cm/day and bottom-melt rate of 1.2 cm/day.
Over the 14 days that 2015F has been without snow, that results in 36 cm top melt and 16.8 cm bottom melt.

The actual thermistor profile from 2015F suggests 80 cm top melt and the sounder suggests 20 cm bottom melt. To explain the large top-melt, maybe the absorption was more than 0.53 for this melting pond. Or maybe insolation at 2015F was higher than the 200 W/m^2 that I assumed.

Yet, pretty cool that the observed melt rates are in the right ballpark with basic physics calculations :) isn't it ?

Quote
Your comment about bottom/ surface melt overlooks that the surface is where longwave IR is emitted. So if shortwave is absorbed gradually throughout the ice your source terms for input are distributed but net outgoing balance is coming from the surface. So an net input of SW will, near  the surface,  make up a net output of IR while near the bottom all incoming energy is available for melt. There is also the question of melt throughout the ice and flushing of water through brine channel from top to bottom which would make heat flux down wards stronger than upwards for the same temperature gradient.
These are guesses based on my understanding of the physics.

Yes, you are right that for accurate top-melt calculations we need to take IR emission/absorption into consideration.
But since around this time, the atmosphere is warmer than the surface (check the 925mb temps) I would suggest that IR may be close to being in 'balance' (incoming and radiated amounts will be approximately the same).
« Last Edit: July 23, 2016, 09:12:45 AM by Rob Dekker »
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Re: The 2016 melting season
« Reply #3593 on: July 23, 2016, 09:32:02 AM »
The high pressure area that was predicted to hit the Arctic appears to be taking place, and it makes for pretty pictures. Here is Obuoy14 in the Beaufort :



This buoy is located at 77 N / 140 W, which is close to the melting edge.
It will be interesting to see if the sun still has enough strength to cause some notable top-melt, since temperatures in the Beaufort have been below average all through June and July, suggesting that bottom-melt has done most of the heavy lifting so far.

Let's see if top-melt will do some damage at this location over the next couple of days.
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Jim Hunt

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Re: The 2016 melting season
« Reply #3594 on: July 23, 2016, 11:03:36 AM »
The July SIPN report is out:

https://www.arcus.org/sipn/sea-ice-outlook/2016/july

Quote
This month the median pan-Arctic extent Outlook for September 2016 sea ice extent is 4.3 million square kilometers (essentially unchanged from June) with quartiles of 4.1 and 4.6 million square kilometers (See Figure 1 in the full report, below). If the median Outlook should agree with the observed estimate come September, this year would be the third lowest September in the satellite record. The spread in the Outlook contributions narrowed slightly from June to July, with an overall range this month of 3.6 to 5.2 million square kilometers.



Meanwhile Andrew Slater's current prediction looks like this:
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Andreas T

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Re: The 2016 melting season
« Reply #3595 on: July 23, 2016, 01:28:50 PM »
...
...

All this said, we can now make an educated estimate for top and bottom melt at 2015F :
- insolation 200 W/m^2 for average weather, with 0.53 (100 W/^2) absorption and 0.22 (44 W/m^2) transmission.
That suggests top-melt rate of 2.6 cm/day and bottom-melt rate of 1.2 cm/day.
Over the 14 days that 2015F has been without snow, that results in 36 cm top melt and 16.8 cm bottom melt.

The actual thermistor profile from 2015F suggests 80 cm top melt and the sounder suggests 20 cm bottom melt. To explain the large top-melt, maybe the absorption was more than 0.53 for this melting pond. Or maybe insolation at 2015F was higher than the 200 W/m^2 that I assumed.

Yet, pretty cool that the observed melt rates are in the right ballpark with basic physics calculations :) isn't it ?

Quote
Your comment about bottom/ surface melt overlooks that the surface is where longwave IR is emitted. So if shortwave is absorbed gradually throughout the ice your source terms for input are distributed but net outgoing balance is coming from the surface. So an net input of SW will, near  the surface,  make up a net output of IR while near the bottom all incoming energy is available for melt. There is also the question of melt throughout the ice and flushing of water through brine channel from top to bottom which would make heat flux down wards stronger than upwards for the same temperature gradient.
These are guesses based on my understanding of the physics.

Yes, you are right that for accurate top-melt calculations we need to take IR emission/absorption into consideration.
But since around this time, the atmosphere is warmer than the surface (check the 925mb temps) I would suggest that IR may be close to being in 'balance' (incoming and radiated amounts will be approximately the same).
you seem to ignore my comment about allocation of energy input to top and bottom melt. I doubt that the transmitted light immediately goes into bottom melt. I most likely warms the water below the ice (the temperature rise is seen in the IMB data as shown in the 2006 plot Jim posted) which then keeps bottom melt going into September when radiation balance starts to become negative. The 53% absorption has to split between top and bottom melt where the ratio is probably impossible to figure out from first principles alone. It also produces the "rotten ice" enlarged brine channels, i.e. there is some melt in the bulk of the ice.
Looking at numbers (I am using the CERES plots we discussed earlier https://ceres-tool.larc.nasa.gov/ord-tool/srbavg)  I agree with your 200W/m2 for all sky July average if July was a little cloudier than 2015. Net surface IR is probably -20 (reading it out of the colour scale) for all sky, so not completely balanced, you are right if the cloud base is as warm or warmer than the ground but air is a poor emitter and clear skies make the IR balance more negative, -70 W/m2 in the CERES plot. SW input becomes more like 320W/m2 under clear sky but we have to distribute that (after taking away reflected 37%) in the ice so the top surface does not gain much (melt power) from clear sky I think.
edit: this is supported by the low air temperatures at Obuoy14 under clear sky seen again today.

 It isn't easy to see how much surface melt occurs from Obuoy images, we have seen the AOFB drop to the lowered surface earlier. The 36cm you quote for IMB2015F is mostly snow, which although is probably quite dense from being drifted about will be less dense than ice. The 80cm is as Jim explains probably a narrow gap along the buoy body taking energy from melt water or higher absorption by the buoy.
« Last Edit: July 23, 2016, 01:51:54 PM by Andreas T »

Tor Bejnar

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Re: The 2016 melting season
« Reply #3596 on: July 23, 2016, 02:34:09 PM »
Pretty clear skies where the Healy is (near 77oN  163oW - from previous webcam image)

Screen shots from here and here.  More Healy info available through USCGC Healy thread.
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Re: The 2016 melting season
« Reply #3597 on: July 23, 2016, 02:59:58 PM »
30 of the last 72 pics (last three days) show direct sunlight, 10 more possibly too, but not out of doubt. The rest either cloudy or foggy. Some of the cloudy ones show the ice well illuminated though.

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Re: The 2016 melting season
« Reply #3598 on: July 23, 2016, 03:40:23 PM »
Doesn't someone do a vector map of the distances each bit of ice has moved over a timescale of (from memory) 1 month, rather than daily?

Is this the sort of thing you're after?

https://nsidc.org/data/docs/daac/nsidc0116_icemotion.gd.html

Quote
This data set provides daily sea ice motion vectors derived from a wide variety of sensors in both gridded and non-gridded (raw) files. For the gridded data, weekly and monthly mean fields are also provided for the entire time series—from November 1978 through May 2015. Browse images of these mean fields are also available.



It's not Near Real Time though.
Thanks for the resource Jim. Yes that would be helpful if they would only update it.

The plot I would really like to see is a map of the Arctic Basin for each month with colour coding over the ice-covered area showing total distance drifted over the month.

Then we could see how much the ice has been shifting and at least get some idea of how that correlates with bottom melt and future loss of the ice.

People who do the detailed ice modelling should have the information to do such a plot? (E.g. US Navy's HYCOM model.)

Presumably that information would also be available, including bottom melt data, for the specific locations of the monitoring buoys.

Andreas T

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Re: The 2016 melting season
« Reply #3599 on: July 23, 2016, 04:40:55 PM »
this has data from beginning of june 2016, not real time either but more recent.
ftp://ftp.ifremer.fr/ifremer/cersat/products/gridded/psi-drift/data/arctic/amsr2-merged/6-daily/ascii/
I haven't looked into it further but a google search showed Neven used IFREMER data a few years ago and NSIDC has this in March http://nsidc.org/arcticseaicenews/2016/03/february-continues-streak-of-record-low-arctic-sea-ice-extent/