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Messages - slow wing

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Arctic sea ice / Re: The 2017/2018 freezing season
« on: March 15, 2018, 02:21:36 AM »
As a scenario for this year, suppose open water North of the Bering Strait & of Svalbard comprise an area of 10% of the Arctic basin by around the Summer solstice.

Can winds then fill up those regions with ice while - to conserve ice area - leaving leads throughout the Arctic basin?

Because open water absorbs sunlight much more efficiently than ice does, those leads could then seed wider gaps in the ice, reinforcing the effect.

Could the Arctic ice melt out that way rather than predominantly getting eaten away at the edges?

Could the ice go like that given sufficient open water to start with at the edges of the Arctic basin? Or is the wind movement too slow to spread the effect through the Arctic basin in a melt season. (Doubtful. I think it's fast enough.) Or, instead, does the ice mainly hold together and most of the open water areas remain at the periphery? Or, as a fourth model, does the ice spread out as it shifts around and any leads are more transitory?

Which of the four is the most appropriate mechanical model for the Arctic sea ice?

Arctic sea ice / Re: Updating the ASIG
« on: March 08, 2018, 12:51:13 AM »
Thanks Neven! The graphic comparison is very helpful for getting an impression of year-to-year variations.

Arctic sea ice / Re: AMSR2 Sea Ice Volume/Thickness
« on: March 05, 2018, 04:14:37 AM »
Very nice Tealight!

Arctic sea ice / Re: The 2017/2018 freezing season
« on: October 05, 2017, 05:19:34 AM »
...More buoys could be deployed, 1000x of what is planned for 2018, for a tiny fraction of submarine or surface ship charter costs.
Yes, true and important. The graphical display of the models is getting so much better but the models have insufficient calibration data from the water. A 1000x bigger deployment of buoys was discussed in last year's freezing season thread, 11 months ago - e.g. #481 - with links to further discussion. A major scale-up of buoy deployment really deserves a thread of its own.

Arctic sea ice / Re: The 2017/2018 freezing season
« on: September 28, 2017, 01:22:38 AM »
  A-Team, thanks for your (typically) wonderful graphics above #118 concerning the persistent hole observed this year in the ice north of the Laptev Sea.

  You conclude "Happenstance with no deeper meaning is the null hypothesis" and say there is no reason to reject it.

  Your graphics show, as you say "polynyas developed at a similar (but not identical) location in some but not all years" from 2012 onwards. In my view that would be surprising under the null hypothesis. The persistence of the 2017 hole was already surprising to me.

  While I agree the null hypothesis cannot yet be rejected, in my view there are other hypotheses that are reasonable and worth exploring further.

  In particular, the polynya was over the Gakkel Ridge - a prominent baryometric feature and with known geothermal vents.

  An issue that needs to be addressed here is that underwater volcanism has been abused by some as a counter to climate change concerns. Here is an example where a polynya was observed over the Gakkel Ridge and all sorts of non sequiturs were drawn from that:

  The intuition of some climate scientists has been that the volcanism probably doesn't have much affect on the sea ice:

  However, that seems somewhat equivocal. The argument is that the heat certainly effects the local ocean depths but is diluted before it gets to the surface.

  The amount of volcanic heat averaged over the Arctic basin is said to be of order 0.1 W/m^2. As it takes around 334 kJ/ kg to melt ice, that is about enough to melt around 3 mm of ice over 4 months (10^7 seconds), averaged over the Arctic basin.

   But what if much of the heat from the Gakkel Ridge volcanoes effectively reaches the surface over the much smaller region where the polynya formed? That much heat over ~1/300th of the Arctic Basin (say 20,000 km^2 which, eye-balling, looks of order the size of the polynya) could melt of order an extra metre of ice rather than just 3 mm and so could punch a polynya in the ice.

  To me the polynya was a notable and recurring feature and some sort of mechanism for getting volcanic vent heat to the surface to cause that is not ruled out as far as I know.

   Are there measured temperature and salinity profiles in that region? (I seem to recall there being a string of Russian tethered buoys but that may be closer to shore.)

UPDATE: there is some instrumentation, see

Again imho, the best 1-parameter indicator of a 'weak freezing season' is the ice volume gain over the Arctic basin. We do have estimates for that from previous years.

What beyond that would make one characterize a freezing season as 'weak'? It could be said to be weak in some regions. An ice thickness gain map could therefore be of interest - up to and ignoring ice position displacements. A freezing season could be said to be weak if it left the Arctic vulnerable to a melt-out in the following melt season. Parameters such as the ice temperature and the quality of the ice (e.g. "rotten ice") could be considered.

But imo the ice volume gain captures much of what we might call a 'weak freezing season'.

There is no coverage of previous years so what best provides historical context for a 'weak freezing season'?
Imho a map over the Arctic Basin of freezing-degree-days should show which freezing seasons are relatively weak, and in which regions. That data exists for previous years as we have their temperature maps.

Arctic sea ice / Re: Latest PIOMAS update (mid July update)
« on: September 19, 2017, 12:01:35 AM »
Thanks Wipneus, always interesting!

So the current ice thickness contours are fairly simple in shape: nearly triangular at 1.75m, 1.50m, 1.25m and weighted to the Atlantic side; and with the Pacific side filled out to form more of a trapezoid at the 1.00m contour.

At this time of year, would we expect it to melt out to around the 1.25m triangular contour?

If so then the Pacific side is going to look very blue come September, as in the past years 2007, 2012 and 2016.

Just eye-balling it, call the 1.25m triangle as having a 2600 km base and 2000 km height, so half-base-times-height would be an end-of-melt-season extent of roughly 2.6 million square kilometers. That is somewhere close to the 2012 record of 3.18 in those units if we add in some extra bits e.g. in the CAA. (Very rough estimate only! It just says it's plausible we could have another low year - perhaps a record or close to a record. Whether that happens or not is still up to the weather and the ocean currents.)
Nope! Looking back 2 months, not the 1.25m contour but instead the 1.00m contour back then was a very good predictor of the melt region perimeter at minimum.

Thanks Wipneus, very interesting!

So this season must have had one of the lowest melt volumes for a while then?

Just eye-balling the graph, it appears that 2014 was the most recent year with a similarly small volume loss, then we need to go back to 2006 for another such year.

Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: September 10, 2017, 10:38:02 PM »
...The ice facing the Laptev looks a bit strange to me, it looks like two packs separated by a crack that opens and closes again. How can the cohesion be expalined?
Striking how closely the shape of the ice appears to match the bathymetry. The ice edge appears to correlate with the termination of the deep water.

Concerning the crack, the bathymetry map shows the deep water is split almost evenly into two basins - the Amundsen Basin on the Pacific side and the Nansen Basin on the Atlantic side - separated by the Nansen-Gakkol Ridge.

Could the edge of the ice be determined in large part by the edge of the deep water? Further, could the crack in the ice, along with its terminating lead (is that a manifestation of the frequently appearing "Laptev Bite"?), correlate with the Nansen-Gakkol Ridge?

Image source:

Arctic sea ice / Re: What the Buoys are telling
« on: August 14, 2017, 10:01:36 PM »
Fantastic movie! The action in the last 30 seconds reminds me of the climax to the old movie Straw Dogs, it's that dramatic  :o

Based on the movie I'm guessing that the edge of the ice floe has been progressively eaten away until it reached the buoy, which had hitherto faced away from the open water but was then released and swiveled around to view it.

I missed the close as wanted to see what the storm would do  :-\

Would have chosen 3.0-3.5 million square kilometres.

Arctic sea ice / Re: What the Buoys are telling
« on: August 10, 2017, 08:51:26 AM »
The halocline has all but collapsed.

Perhaps you could highlight on that ITP 95 T&S plot what you consider to be evidence for your assertion?
Had just been musing on the potential benefit of having a third profile contour plot to go with the temperature and salinity ones, namely, the water density profile. (Or could instead plot the gradient of the density.)

That should be easily derived from the information already in the other two and would show more directly where the density gradient was small i.e. 'halocline all but collapsed'.

Is that third profile contour ever plotted along with the other two?

Arctic sea ice / Re: The 2017 melting season
« on: August 08, 2017, 12:03:44 PM »
At, NAVGEM as well has the storm strengthening - down to 973 hPa in the 48h prediction.

With weaker ice than in 2012, we may well be looking at storm damage to the ice comparable to that from the 2012 GAC (Great Arctic Cyclone).

From memory, Neven records the GAC as bottoming out at 966 hPa and lasting 13 days. For comparison, NAVGEM records the current storm as having already dropped to 985 hPa at 12z back on 5 August, waxing and waning through the present and still at 986 hPa at their final, 180h prediction, 10 days later at 12z on 15 August.

While that final prediction is expected to be too far out to be reliable, the point is that the NAVGEM predictions show no sign of the storm dying out in the foreseeable future.

So for how much of August will it rotate around the Arctic Basin, sometimes weaker, sometimes stronger, but bringing significant winds all the while to potentially damage the ice pack?

Arctic sea ice / Re: IJIS
« on: August 08, 2017, 11:32:40 AM »
 ;D this discussion has already taken place.

The outcome was that Espen is mightier than the N word.  :P

Arctic sea ice / Re: The 2017 melting season
« on: August 08, 2017, 02:54:03 AM »
A-Team, I was thinking the 'Beaufort Finger' was this feature?

Arctic sea ice / Re: The 2017 melting season
« on: August 08, 2017, 01:31:24 AM »
Interesting sequence Thomas.

The thing that catches the eye about the 2017 plot is a 'channel' of thinner ice running from the Fram strait towards the Beaufort sea.

What is it?
If I recall correctly, it was a band of ice that piled up against the coast and then was blown out to sea.

Arctic sea ice / Re: Arctic Image of the Day
« on: August 06, 2017, 05:26:44 AM »
Adam, yes the ship is going backwards!

It is a double acting ship:

"The propulsion system of the new gas carrier consists of Azipod type propulsion units. They provide a very high degree of manoeuvrability, and allow use of the stern-first motion (Double Acting Tanker, DAT function) principle, which is necessary to overcome hummocks and heavy ice fields. Uniquely Christophe de Margerie has three Azipods – this is the first time so many of these propulsion units have been installed on an Arctic ice class vessel."

In thick ice, it is faster when going backwards!

"The stern section is designed to enable navigation in severe ice conditions.
The double-acting tanker capability allows the vessel to break heavy ice in both bow and astern manuoevres.
The vessel proved her capability to move stern-first in 1.5 metres thick ice at a speed of 7.2 knots (target figure was 5 knots) and head-on at a speed of 2.5 knots (target figure was 2 knots)"

Arctic sea ice / Re: The 2017 melting season
« on: August 06, 2017, 05:11:24 AM »
Adam, thanks for your comment.
That is true - the initial wave and wind damage will be largely on metre-scale floes - although it could also break up larger floes.
Even so, I still don't see any regions where more water is showing.
Q1. There will presumably be some regions composed of lots of metre-scale floes?
Q2. Wouldn't such regions darken in this gif if the small floes are decomposing?

Arctic sea ice / Re: The 2017 melting season
« on: August 06, 2017, 12:56:20 AM »
July 31-Aug 4, high speed loop to allow the eye to see through the clouds.

Wrangel island in lower left, Beaufort lower right.
Thanks Jay, this is very helpful to my understanding of what is going on under these storms.
Yes, the ice is moved around, but is there any melt or breaking up of the floes?
I just can't see any, even in the regions where the ice is already degraded.
This gif has caused me to think the storms are having less impact than I had previously thought.

Arctic sea ice / Re: The 2017 melting season
« on: August 04, 2017, 02:58:14 AM »
Sorry, if I'm interrupting the current discussion. Just posting an animation of the last two weeks with some slowmotion. In my opinion now you can see very well, what are clouds and what is SI. If the trend we see continues, the next two weeks could definitely wreck the ice.
Building on the last frame of TT's concentration map, I overlaid 48hrs of Euro forecasted surface winds via WindyTV. GFS is in good general agreement, although the euro has higher winds - up to 64KM.

Just loving these graphics, thank you! They provide excellent visual aids to understand what is going on with the ice.

(Probably way too much to even suggest but I would bookmark these if it happened they could be done daily and put on Neven's graphics page.)

Arctic sea ice / Re: Determining ocean heat content and salinity
« on: July 29, 2017, 03:40:54 AM »
Thanks Ice Shieldz, this is an important topic!

The Arctic sea ice is going to be blown around from now until the end of the melt season and how much melts out is going to be largely determined by how much heat in the water is available to it.

My impression is that we can't answer that question with any degree of accuracy because we don't have anywhere enough instrumentation in the water to tell us.

True or false?

If true then it's a travesty given the importance of the Arctic sea ice and given that deploying sufficient arrays of buoys should only cost in the ballpark of tens of millions of dollars - chickenfeed in today's global economy.

Is there a summary map somewhere showing locations of all the buoys in the Arctic basin with strings of temperature and salinity sensors?

Arctic sea ice / Re: Northwest Passage thread
« on: July 26, 2017, 10:18:55 PM »
Really nice pics! Thanks Jim.

Arctic sea ice / Re: The 2017 melting season
« on: July 22, 2017, 07:20:24 AM »
People keep hoping that all the clouds will preserve the ice. Its faster to boil a potato than to bake it. And faster to steam it than boil it. Water vapour at or below boiling point is a very effective heat transfer vehicle to colder objects.
  Hyperion, I read your analyses with great interest. Not so sure about your potato-cooking analogy of the bolded bit though.

  Baking a potato relies on thermal convection and conduction through the air in the oven. The Arctic ice melt process that best corresponds to is not to direct insolation but instead to the different heating mechanism of warm winds blowing across the ice.

  About the fastest way to cook a potato is to microwave it and that might provide the best analogy for direct solar insolation into the ice.

  With direct insolation, the sun's energy (which of course is ultimately responsible for the other heating processes you discuss as well) is deposited directly into the interior of the ice (or melt-pond water) - which is how microwave ovens work as well, just using a different part of the electromagnetic spectrum.

  So my gut feeling is that this heat transfer by vapour condensation must need a lot of vapour (as you point out, this is the situation at the moment) and be reasonably efficient in order to be comparably effective to direct solar insolation.

  I'm skeptical because to the extent that it's falling as rain at a few degrees C then that part of the 10 cubic kilometres per day of incoming total atmospheric water that you mention is only going to melt a fraction of one cubic kilometre of ice per day (compare water's 334 J/g heat of fusion with a few times 4.2 J/g-degrees C). The only really efficient mechanism will be direct contact of the water vapour with the ice.

  That also accords with experience from observing the melt season in past years: generally the best atmospheric conditions for melting ice near mid-Summer appears to have been clear skies.

  I do appreciate your point that there is an anomalously large amount of incoming water at the moment so it will anyway be interesting to see how much melt there has been on the Pacific side when the clouds clear.

Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: July 21, 2017, 03:30:45 AM »
Thanks again Wipneus for your amazingly informative plots - most recently the comparison between last year and this year of melting until the currrent date in the Beaufort Sea.

I agree, Shared Humanity, the large amount of dispersion last year in the Beaufort Sea was fatal for its sea ice. Indeed, it essentially melted out by the end of July! As far as I know this was earlier than any other year in the satellite record: see year comparison maps for Arctic sea ice at 1 August.

That won't happen this year but, as seaicesailor points out, there will still be a further month-and-a-half for the Beaufort ice to melt out and I expect that to happen.

Arctic sea ice / Re: Latest PIOMAS update (mid July update)
« on: July 18, 2017, 03:26:40 PM »
Thanks Wipneus, always interesting!

So the current ice thickness contours are fairly simple in shape: nearly triangular at 1.75m, 1.50m, 1.25m and weighted to the Atlantic side; and with the Pacific side filled out to form more of a trapezoid at the 1.00m contour.

At this time of year, would we expect it to melt out to around the 1.25m triangular contour?

If so then the Pacific side is going to look very blue come September, as in the past years 2007, 2012 and 2016.

Just eye-balling it, call the 1.25m triangle as having a 2600 km base and 2000 km height, so half-base-times-height would be an end-of-melt-season extent of roughly 2.6 million square kilometers. That is somewhere close to the 2012 record of 3.18 in those units if we add in some extra bits e.g. in the CAA. (Very rough estimate only! It just says it's plausible we could have another low year - perhaps a record or close to a record. Whether that happens or not is still up to the weather and the ocean currents.)

Arctic sea ice / Re: What the Buoys are telling
« on: July 12, 2017, 05:45:47 AM »
Would a simple explanation be that the pond on the right doesn't drain because it doesn't happen to have a drainage channel open to lower levels?

PS I enjoy reading this thread and seeing the pictures and data - thanks to those contributing.

I voted 3.0-3.5 million square kilometres.

I think the day minimum has more physical significance than the monthly one (what is the physical significance of a month?  ;) ) so I just added 0.5 to my prediction in the day poll, where I explained my reasoning/guessing.

Voted between 2.50 and 3.00 (units of million square kilometres), so predicting a new record by a small or moderate margin, beating the old record of 3.18 set in 2012.

A lot still depends on the weather. The answer could go as low as 1 or as high as 5.

 July is probably the most critical melt month as the Arctic receives plenty of sun and the ice pack has begun to degrade so the sun can find water in the Central Arctic Basin rather than being predominantly reflected back by snow or ice.

  I liked an analogy Neven made with a Mike Tyson combination if the Arctic got two strong storms with a period of sunny weather sandwiched in between.

  It's the combination that matters (although full time sun would also destroy the ice). To melt, the Arctic ice pack needs heat as well as a way for the ice to receive the heat.

  June already had a storm that dispersed the ice and presumably broke it up and made it more mobile.

   I'll disagree with most by saying the dipole configuration that followed was actually favourable for preserving the ice. The reason is that it compacted the ice, thus removing the holes in the interior that could otherwise have absorbed heat from the sun.

   Compaction during late June and early July generally helps preserve the ice, dispersion hurts it.

  Now we are getting another dipole with a high pressure system heading down the Pacific side.

  After that, who knows? The weather forecasts don't extend far enough in the future to give much guidance on the course of the melt season.

  There is evidence that storms in the melt season are becoming more frequent and stronger. There may even be a 'hurricane alley' developing with storms arriving from the Russian side down into the Laptev Sea and then heading deeper into the Arctic Basin. If so then that is going to move the remaining ice around in August and pick up any accessible heat in the water.

  By region in the Central Arctic then:

The Russian side (Laptev, Chukchi and Bering Seas), which already had thinner ice than usual, is getting worked over with lots of wind and some sun.  Prediction: that ice will melt out early.

The Beaufort: primarily first year ice but it has been piled up in thickness by winds blowing predominantly from the Russian side. Even so, it is receiving the combination blows discussed above. Prediction: the Pacific side is going to melt right out, probably to an extent that is visually striking.

The Canadian Arctic Archipelago (CAA). Is there a trend in most recent years for the islands to lose their snow cover earlier and heat up in the sun? The CAA is going to continue the trend (if I'm remembering correctly) and melt out by a record or near record amount.

The Central Arctic basin. This is the ice sanctuary. It will lose some thick ice through the Nares Strait and what Neven has dubbed the CAA 'garlic press' but next to the Canadian coast and Greenland will almost certainly retain much of the surviving ice.

 The Atlantic side. The big question mark for me. It depends on the weather! Also there is uncertainty on the thickness of the ice. Compared to the Pacific side, it has been cooler and hasn't received as much sun. I do think the ice is thin and vulnerable first year ice in the Russian-Atlantic quadrant and probably this will largely melt out anyway. On the other hand, a lot of ice will likely remain between Svalbard and the North Pole, extending down into the Fram Strait.

 So I predict that the remaining sea ice will be more skewed to the Atlantic side than in most years.

 That's my thinking in voting between 2.50 and 3.00 million square kilometres. Due mainly to record low volume heading into the melt season, I think a record or near record is likely.

Arctic sea ice / Re: Latest PIOMAS update (July)
« on: July 03, 2017, 11:16:10 AM »
As discussed previously - not sure if it was this thread or another - the 1.5 metre thickness line could be considered a proxy for predicting the extent at the end of the melt season.

So the predicted minimum extent for this year might look something like shown below.

As shown, the shape might be reasonably similar to last year, 2016, with a minimum extent that might also be similar to last year's extent.

Arctic sea ice / Re: The 2017 melting season
« on: July 01, 2017, 06:27:43 AM »
Yes, it would be better to have a temperature average over the whole Arctic Basin than just over greater than 80 degrees N.

Looking back through the years in the archive, at, several recent years have low T80 Summer temperatures, including the strong melt year 2010.

So it will relate to the specific weather pattern for the year and not necessarily with melt potential.

Personally I don't find the T80 graph to be of much analytical use over the Summer as we can look at the daily temperature maps from, for example, Nullschool, and see the actual temperature distribution over the entire Arctic.

Anyway, attached are the graphs for 2009, 2010, 2013 and 2014 - which all have low T80 Summer temperatures.

Arctic sea ice / Re: The 2017 melting season
« on: July 01, 2017, 12:41:04 AM »
Wow! NAVGEM is showing a really settled Arctic Basin by day 7. There's hardly any gradient at all! The highest pressure over most of the Basin is 1014 and the lowest is 1004!

Of course, 7 days is a long way away so we will have to see if this verifies.

Arctic sea ice / Re: The 2017 melting season
« on: June 27, 2017, 03:00:42 PM »
A NEW storm has arrived in the Laptev Sea just as the persistent storm began to weaken.

It is already at 983 hPa, which is predicted to be its lowest pressure, so it is also a strong storm for June.

The ice in the Laptev Sea is already a mess so this storm will likely cause carnage there.

Has the 'cyclone alley' of last year - Western Siberia down into the Laptev Sea - started up earlier and stronger this year??

Arctic sea ice / Re: The 2017 melting season
« on: June 27, 2017, 02:50:31 PM »
According to the model analyses on, the cyclone bottomed out at 982 hPa on last Sunday and Monday, 25 and 26 June 2017.

So it was still a strong and persistent storm, only 2 hPa above the June record for the Arctic Basin in the satellite era of 980 hPa, set in 2013.

Arctic sea ice / Re: The 2017 melting season
« on: June 26, 2017, 01:22:03 PM »
EOSDIS Worldview shows the 'low concentration' regions on the Atlantic side of the U Bremen AMSR2 map as genuine gaps in the ice rather than melt ponds.

  As can be seen by comparing the figures below, the boundary of first year sea ice seems to also roughly bound the main region of low concentration within the Arctic Basin proper. That is, the first year ice in that region already has gaps whereas the second year ice next to it is generally in better shape.

  To guide the eye, I've drawn a boundary line on each of the the three maps - but only roughly - the 3 lines will coincide only approximately.

  This lower concentration first year ice will struggle to survive the melt season, especially if July is sunny on the Atlantic side.

   It's going to be interesting to see how near this year's melt out will come to the North Pole.

Arctic sea ice / Re: The 2017 melting season
« on: June 26, 2017, 05:38:55 AM »
University of Bremen's AMSR2 Arctic sea ice concentration map has updated, now on 25 June, which is one of the dates of Neven's year-to-year comparison graphic:

At bottom right, 2017 has more blue showing around the edge of the Arctic Basin than in previous years. This is in agreement with Wipneus' extent calculation for the restricted central regions of the Arctic Basin that has 2017 as the year with the lowest extent.

Some melt ponds are showing in the interior by now, catching up with the other years. Note again that the palette has changed: 2017 doesn't show the white flecks at just below 100% concentration that the other years do.

Still early days in the melt season.

Arctic sea ice / Re: The 2017 melting season
« on: June 24, 2017, 10:19:11 PM »
  The persistent storm in the CAB is currently at around 985 hPa.

  As shown below, the models (& have added the ensembles) are backing off on how much it will strengthen over the next couple of days. They now predict it to bottom out at around, or a bit below, the 2013 record for June of 980 hPa.

Arctic sea ice / Re: The 2017 melting season
« on: June 24, 2017, 02:59:12 AM »
The weather models on are now all predicting the storm pressure to bottom out in about 3 days' time.

 They all predict it to beat the previous record in the satellite era for low sea level pressure in the Arctic Basin in June, of 980 hPa in 2013, and by a fair margin.

As shown below, the predictions range from 966 hPa up to 974 hPa.

Arctic sea ice / Re: Arctic Image of the Day
« on: June 24, 2017, 02:26:49 AM »

Arctic sea ice / Re: Stupid Questions :o
« on: June 23, 2017, 03:07:13 AM »
Kate, was it ASI graphs?

It's actually linked at the top of this page, immediately below the graphic, but the link isn't underlined so it isn't obvious.

Arctic sea ice / Re: The 2017 melting season
« on: June 23, 2017, 12:42:35 AM »
Neven, Re your #2218, yes ECMWF has backed off on the strength of the predicted 'weather bomb' storm and also pushed it later.

  The same is true of 3 other models on that previously predicted it. (The exception is CMC, which still shows it at the same time and strength.)

  NAVGEM is now at 976 hPa on their 12z run - close to their 978 hPa prediction from 12 hours earlier - so they were the only model not predicting 970 hPa or lower.

The updated predictions are attached. They can be compared with the predictions from 12 hours ago shown in my post #2198.

  So it looks more likely that there won't be a 960s weather bomb after all in the next few days.

  The persistent storm does look like it will re-strengthen though over that timeframe, perhaps down to the mid- or high- 970s. That would still be a strong storm and as far as I know a record low pressure for June in the satellite era (beating 980 hPa, in 2013).

  The ice appears to be mobile this year so this persistent storm will likely, by its end, have displaced ice by up to hundreds of kilometers over much of the Arctic Basin.

  As Romett1 notes above at #2202, HYCOM predicts this as well. The main effect will likely be a lot of ice pushed over towards the Barents Sea and Fram Strait, along with gaps opening up in the interior of the pack.

Arctic sea ice / Re: The 2017 melting season
« on: June 22, 2017, 12:35:46 PM »
On viewing the model predictions at, the models all agree on a strong pressure minimum on or around 00z Monday, June 26 2017.

NAVGEM shows the 'weakest' storm prediction: already relatively strong at 978 hPa.
CMC has the strongest storm, bottoming out at 961 hPa.

The current predictions of the various models for pressure minima are summarised in the attached table.

Arctic sea ice / Re: The 2017 melting season
« on: June 21, 2017, 02:45:45 AM »
  19 June is one of the dates displayed in Neven's excellent year-to-year comparison of U. Bremen's AMSR2 sea ice concentration maps:

  I mainly look at the ice pack in the Arctic Basin as that is what mainly determines what sea ice is left at the end of the melt season.

  This year's Arctic Basin at 19 June shows the melt at the pack edge is advanced this year inside the Bering Strait and relatively advanced in the Beaufort Sea and on the Russian side.

   However, the pack itself looks generally darker than in previous years.

   What should be pointed out as at least a partial explanation is that THE COLOUR PALETTE CHANGED THIS YEAR.

There is no longer a light concentration band near 100% that can produce light flecks all over the ice pack.

Shown below is the 19 June map comparison as well as the colour palettes for 2016 and 2017 with the change circled.

Arctic sea ice / Re: The 2017 melting season
« on: June 20, 2017, 05:48:03 AM »
Neven, thanks for Reply #2121 and its links, informing that in 2013 the Arctic Basin also had a strong and persistent low pressure system in June.

That's mildly comforting given that 2013 was a recovery year from the carnage of 2012.

There are differences from this year though that may make comparisons unsafe.

Firstly, the 2013 system was earlier in the melt season, beginning towards the end of May.

The CAB ice pack has already opened up more than was the case in 2013 and is starting to melt out more, particularly on the Russian side.

  In both years, the melt will be retarded by increased cloud cover.

  I'm wondering if this year there may be a stronger competing effect from ice movement induced by the storm winds generated.

  The ice is thin and may be more likely to move around than was the case in 2013.

  Also, the winds North of Greenland will be from West to East, so pushing the ice in the direction of the Atlantic and the Fram Strait 'ice sink'. This year's thick ice is already biased over towards that side and so we may lose thicker ice.

  Also, that displaced ice will likely produce leads and other gaps in its wake. Right at the Summer solstice now, those areas of open water will then heat up and seed melt in the adjacent ice.

  Quantitatively? If those winds persist for 1-2 weeks then the thicker ice will likely move a couple of hundred kilometres towards the Atlantic. (To set the scale, the Fram Strait is 450 km wide, so perhaps half of that.)

  If the ice front is of order 1000 km long then the total displacement towards the Atlantic might be of order 200 km x 1000 km ~ 200,000 km^2.

   Given that the Fram Strait and Atlantic are 'death zones' in recent years, that 200,000 km^2 might be considered extra ice lost.

   Correspondingly, the leads opened up in the pack behind might also have a total area of 200,000 km^2. That would be significant in seeding melt in the adjacent ice.

  This is all speculative and back-of-the-envelope, but it will be interesting to see how much the thicker ice is pushed East to the Atlantic and also to see if any visible leads are opened up.

  Then there will be Ekman pumping as well, which might melt some more ice.

  Having said that, the cloud cover afforded from the 24 hour a day sunlight is a big loss of melting potential to compensate for.

  So, in summary, this storm might be steering us towards a weaker melt season, like in 2013, but there are compensating effects so it might not.

Arctic sea ice / Re: The 2017 melting season
« on: June 20, 2017, 01:38:31 AM »
ECMWF 12z op:  967 hpa bomb cyclone at +144h

GFS 12z op run: 967 hpa bomb cyclone at +126h

The fact that both models put the cyclone down to sub 970 hpa is really ominous. ...

You've only looked at those two models though. I checked with two other models on and they don't show the same level of 'weather bomb'.

Viewing CMC instead, the 12z 19 June run only drops to 977 hPa (is at 150h).

At 126h - when GFS has its 'bomb' - CMC has gone in the other direction with that system, to 992 hPa.

Viewing NAVGEM 12z 19 June run, the lowest that drops to is 976 hPa, at 136h.

The models sometimes generate very low pressure predictions out beyond 5 days that don't come to pass. So in my view this one is still too uncertain to be concerned about just yet.

Arctic sea ice / Re: The 2017 melting season
« on: June 18, 2017, 09:46:37 PM »
The current and forecast weather provides more evidence that the Arctic has become more windy over the past couple of years (could pick December 2015 storm as starting point), even during the melt season.

  Currently a large cyclone of 985 hPa sits in the Arctic basin, fairly central and towards the Atlantic side. That is already unusual for June and perhaps almost unprecedented in the satellite record. (Does anyone remember similar or lower in June?)

  All of ECMWF, GFS, CMC, NAVGEM and JMA expect it to stay there and even intensify down into the high or mid 970s in around six days from now.

  I presume that such persistent and strong low pressure over the Arctic Basin is new territory over the satellite record for June.

  It is unclear to me that this helps to preserve the ice for this melt season, as some above appear to be suggesting. To the contrary, it generates a lot of wind to carry heat and moisture in from the land and to fracture and push the ice around.

  I view it as concerning both for this melt season and also as a sign of changes in the Arctic climate occurring within timescales of only a few years.

   Shown below is the furthest forecast displayed by Nullschool, about 5 days from now. It uses GFS forecasting and the predicted MSLP at the cyclone's core, currently at 985 hPa, has dropped by then to 980 hPa.

Arctic sea ice / Re: The 2017 melting season
« on: June 16, 2017, 02:29:49 AM »
Wipneus posted a fascinating and potentially alarming gif on his Home Brew thread.

The state of the ice north of Greenland catches the eye. Wipneus cranks up the contrast for those gifs in order to pick out features, so how bad and/or unusual is the situation there?

Looking on Worldview, I was surprised to see the amount of year-to-year variation in that area.

Hoping this 7.7 Mb gif loads so you can see what I mean.

The year is displayed in the top right hand corner.

I score it:
2014 worst
2013 second worst
2012 ~ 2017
2015 and 2016 the ice looks in good shape.

In any event, 2017 doesn't stand out as anomalous. Apparently there are 'good years' and 'bad years' for the sea ice at this particular date and area.

What do more experienced ice watchers than me have to say on the gif?

Arctic sea ice / Re: Accuracy of poll predictions
« on: June 16, 2017, 01:42:49 AM »
X would be an estimate of the bias only and probably not a very good one as it's only 4 years of data and Mother Nature has had a big say.

  The actual bias could be defined as the difference between what the forum votes and what some idealised observer with essentially perfect knowledge of the physics would vote.

  The trouble is, the weather fluctuates away from the climate mean so the idealised observer also won't predict the exact answer each year. (It's a chaotic system so the fluctuation is not predictable even with essentially perfect knowledge of the physics.)

  2013 was a rebound year. Was that mostly physics or fluctuation? Given the resumption of the downward trend culminating in the record low maximum volume this year, I suspect the latter. So even the idealised observer would have voted high[EDIT]low - perhaps in all 6 polls for 2013.

  For the other 3 years, its a more difficult question whether the fluctuation was upwards or downwards.

  In my view we can't even rule out that the idealised observer would have voted high[EDIT]low on the other 3 years as well - and maybe in 23 out of the 24 polls. In that case, there would be no evidence whatsoever for bias in the forum.

  It's a shame we don't have polls from 2012 as well. I suspect 2012 was a downwards fluctuation and so the idealised observer would have voted high in 2012, maybe in all 6 polls.

  Maybe the forum would have voted high as well in most or all of the 6 hypothetical polls for 2012. That would have given a very different look to the graphs in the opening post. Does anyone remember if the forum was generally thinking higher or lower than the final numbers for 2012?
  In summary, it's easy to over-interpret the graphs in the opening post and difficult to establish bias from only 4 years data in a complicated and chaotic system.

Arctic sea ice / Re: The 2017 melting season
« on: June 13, 2017, 01:51:51 PM »
More widespread melt ponds might be expected to appear once much of the Arctic Basin has surface air temperatures rising above freezing.

Nullschool shows this happening around 5 days out - admittedly at the limit of any sort of predictive power for GFS forecasting.

The forecast for 0600 UTC on 18 June shows a fair amount of wind over the Arctic Basin and with nearly all of it above freezing.

Arctic sea ice / Re: The 2017 melting season
« on: June 13, 2017, 06:37:12 AM »
Tigertown, the Worldview image doesn't confirm a hole there, looking around (165W, 77N) - maybe a bit of grey showing surface melting.

Nullschool confirms that was a hotspot yesterday, at above +1 degree Celsius, near the centre of a high pressure system.

So the hole in that U. Bremen reconstruction of AMSR2 might well be modified for their 13 June map. It's still above freezing around there so the melt pond hole might possibly even get bigger and/or track the centre of the high pressure system heading northwards.

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