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Messages - slow wing

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Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 17, 2019, 05:38:59 PM »
Mercator has made multiple "improvements" of their model and their data sets over the years. Every time they make an improvement the older images are removed from public access. I find it frustrating when it becomes impossible to go back more than a year or 2 to make comparisons.

Some very important things are happening in the Beaufort and other Arctic seas, but we are almost blind to what's happening because of the paucity of buoys and ships monitoring the Arctic. It's crazy that there isn't better monitoring of the Arctic.

Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 17, 2019, 04:53:35 PM »
I make a quick map to compare 2019 on the 26th of August (forecast from Mercator) to mean from 2016, 2017, 2018. I don't know why, I was not able to download data for prior years, I don't know why... Excepted for the Barents sea which is cooler than over the 3 previous years (also the case for SSTs with a true base period), everywhere the warmth is showing, and even in the central basin there is streams of abnormally warm temperature.

Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 16, 2019, 04:54:21 PM »
And now ITP 110 has hoisted the white flag and surrender. No news since two weeks. Too bad, as Mercator is showing extreme warmth in Beaufort. It should have been interesting to see what really happens here. The build up of heat shown at 30m and 100m is like nothing ever seen. Will this have an influence on refreeze season ? And Mercator was shown to be warming not enough compared to ITP 100. Depite this, in part of the Beaufort Sea, the big mess is going on and on, with a loosening of the stratification and a build up of energy wich is beyond superlatives and the "spot the difference" game ... Where now the Pacific layer and the halocline ? Where is the freshening and the cooling ? I don't know where we are going at this pace, but here we go.

P.S. : There is no special reason for a comparison with 2016, it was only to give a point of reference for a year wich was in its own quite bad for Arctic.

Arctic sea ice / Re: The 2019 melting season
« on: August 14, 2019, 08:01:13 PM »
I suspect it makes zero difference and the email itself no longer goes to an actual person, but I emailed the address for the Barrow Sea Ice Webcam stating that it has been down for almost 1/2 the month. Hopefully it gets repaired because I really enjoy looking at it.

Arctic sea ice / Re: The 2019 melting season
« on: August 13, 2019, 08:34:41 PM »
Ascat with NSIDC ice age overlaid at 20% transparent, mar21-aug12. Not the cleanest animation but here attempting to highlight Oren's comment about first year ice upthread.
The ice age product is weekly and has been duplicated so that the dates should match (edit: except for this week). When this week's ice age map is released I'll try an overlay with amsr2 which should be cleaner.
ice age colours are altered slightly by the transparency

Arctic sea ice / Re: Arctic Image of the Day
« on: August 12, 2019, 11:38:49 AM »
Actually,  after looking at the original more closely, that dark colour might be all melt ponds, and a low sun angle on wet snow/ice. I think only the pressure ridges are showing up white here, maybe because they stick up into the sunlight?

I've attached a crop of the original to try to show some of the detail.

Edit: in any case, there is no way a Russian research team is setting up a research station on that ice! Yikes.

Arctic sea ice / Re: Arctic Image of the Day
« on: August 12, 2019, 07:51:15 AM »
Here are a couple of photos I got while flying over the Arctic, from Toronto to Hong Kong on August 1st. (yes, I feel bad about flying due to emissions, but it's not a vacation, we've moved to Jakarta for my wife's work. we will also buy some offsets to try to compensate a bit.)

We were trying to sleep through the 15 hour overnight flight, but I managed to some how wake myself up at the right time to open the window blind and blind myself with the glare.

Again, taken on Aug. 1st, somewhere between Greenland and the North Pole. It seems like a lot of water visible in the leads for this area, even for this time of year. Maybe it's normal recently, but I can't imagine it would've been normal when this area used to be dominated by multiyear ice.

If you want to see the full size images, DM me and I'll email them to you.


Arctic sea ice / Re: The 2019 melting season
« on: August 08, 2019, 10:16:22 PM »
'cold air has been flowing persistently to northern Finland from the Arctic ocean'
and doing its best to take the ice with it. Not that it gets far into atlantic waters.

Today looking at mercator 0m sea temperature with unihamburg amsr2-uhh overlay at 60% transparency this time to allow some of the mercator model's higher coastal SST's beneath the ice to show through. I didn't notice that before doing this overlay. That would explain the rapid melt of ESS/Laptev fast ice. amsr2 0% concentration (open water) has been set to fully transparent, jun1-aug7.
Attention is unsurprisingly mostly on the Chukchi/Beaufort and Laptev at the moment but note also the heat building up to the east of the Fram Strait.
The CAB beginning to resemble a ripe stilton

Arctic sea ice / Re: The 2019 melting season
« on: August 08, 2019, 06:00:52 AM »
7 August is another date where Neven has a year-to-year comparison of the U. Bremen AMSR2 sea ice concentration maps.

See figure below. The latest 2019 map is bottom right. It can be compared by eye to some of the previous worst years for sea ice minimum extent. Other recent years are available for comparison on the web page.

2019 looks worse to me on this date than any of the previous years other than 2012 and 2007. (2016 caught up later in the month - see the web page.) Even so, it's still to be determined how much of this year's lowered-concentration regions -- particularly in the Laptev sector, and north of the CAA -- will melt out by the minimum.

Keep in mind, most of that "thick" ice, if not all of it, along the CAA border, is an artefact (an error).

Might have something to do with part of the gulf stream being pulled into that system, cloud cover, not really sure, it happens sometimes with AMRS2 though.

The ice thickness there is probably at a lower level than it's been in any of those years. More pressure + heat over the CAA for a while too.

Arctic sea ice / Re: The 2019 melting season
« on: August 08, 2019, 12:49:27 AM »
Bit of a peek through only thin cloud over part of the Beaufort today. Some big holes have developed.

Arctic sea ice / Re: Arctic Image of the Day
« on: August 07, 2019, 05:31:44 PM »
The National Oceanic and Atmospheric Administration (NOAA) has been tracking the melt season with aircraft flights over the ice north of Utqiagvik, Alaska, as part of its Arctic Heat program. While onboard some of these flights in mid-July, Kevin Woods of the NOAA Pacific Marine Environmental Lab in Seattle, Washington took several photos of the sea ice (Figure 5c). The ice appeared to be highly decayed with deep melt ponds, many melted completely through the ice. In other areas, the ice was sparse with isolated floes surrounded by open water. Much of this is likely to melt out completely by the end of the summer.

Figure 5c. In this photo taken during a NOAA flight north of Utqiagvik, Alaska, sea ice appears to be highly decayed with deep melt ponds.

Arctic sea ice / Re: The 2019 melting season
« on: August 07, 2019, 05:15:09 PM »
NSIDC posted their July summary:

Nice SST map, among other useful information.

Figure 4b. This map of the Arctic Ocean shows sea surface temperature in degrees Celsius for July 31, 2019. Data are from the University of Washington Polar Science Center UpTempO buoys and satellite-derived values from the National Oceanic and Atmospheric Association (NOAA).

Arctic sea ice / Re: Latest PIOMAS update (August 2019)
« on: August 06, 2019, 03:42:08 PM »
That highly anomalous steepening of the volume curve in mid-August 2012 is best explained, in my opinion, by Ekman pumping of heat from the Atlantic water layer into the surface ocean. Normal storms can't do this because they don't persist long enough to break up the strong density inversions. The GAC lasted ten days and was very intense at its peak. It was strong and persistent enough to break down the layering in a large volume of the Arctic ocean.

The buoy profiles were stunning. Ekman pumping by persistent high pressure areas has caused multiple episodes of upwelling along the continental shelf in the Beaufort sea, but I'm not aware of any storm other than the GAC causing a upwelling of mid-ocean water in the central Arctic ocean. There was a very large amount of energy involved in the rapid melting of ice in mid-August 2012. Because there were not large amounts of heat advected by the atmosphere, it must have come from the ocean.

This melting season atmospheric heat advection may be larger than it was in 2012, but so far storms are not persisting like the GAC, so we should perhaps expect less bottom melt from ocean heat than took place in August 2012. However, sea surface temperatures in the Arctic are very high this summer so there is a lot of ocean heat in the upper layers. Moreover, strong atmospheric heat advection has been persisting in the Arctic for months. We are going to get a chance to compare the effects of different processes on the melt minimum by comparing 2012 and 2019. The sea ice volume curves are a most important aspect of that comparison because they are a function of system enthalpy (heat).

Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 05, 2019, 07:11:59 PM »
itp buoys updating again today. Here is whoi itp110 day 210-217
click to run

Arctic sea ice / Re: The 2019 melting season
« on: August 05, 2019, 06:13:26 PM »
Things keep changing fast, the central pack is not as solid as it looked one week ago, the periphery vanishes.

Arctic sea ice / Re: "Stupid" Questions :o
« on: August 05, 2019, 03:20:06 AM »
Last one.

A nice thesis:

The impact of near-inertial waves on the Arctic halocline

And very educational course slides:

Ocean Dynamics

Arctic sea ice / Re: "Stupid" Questions :o
« on: August 05, 2019, 01:42:57 AM »

Why did CO2 go up during the interglacials over the last 800,000 years?

In previous warm periods, it was not a CO₂ spike that kickstarted the warming, but small and predictable wobbles in Earth’s rotation and orbit around the Sun. CO₂ played a big role as a natural amplifier of the small climate shifts initiated by these wobbles. As the planet began to cool, more CO₂ dissolved into the oceans, reducing the greenhouse effect and causing more cooling. Similarly, CO₂ was released from the oceans to the atmosphere when the planet warmed, driving further warming.

The speed at which CO₂ is rising now has no comparison in the recorded past. The fastest natural shifts out of ice ages saw CO₂ levels increase by around 35 parts per million (ppm) in 1,000 years.Humans have emitted the equivalent amount in just the last 17 years.

Arctic sea ice / Re: "Stupid" Questions :o
« on: August 05, 2019, 12:43:12 AM »
Q. Can it? My response to this statement on the 2019 Melting Thread.

There is more than enough heat in the deep water to melt the ice and keep the arctic ice free year round. 

However, the heat can not move upwards through the halocline. 

The halocline is 50 meters thick (at least) and is very difficult to breach.  If it ever happens, look out!   The arctic will be a completely different place.

I've often wondered if/why the thermal conductivity of seawater is insufficient for significant melting of the ice just by thermal conduction, when the halocline is stable.

So let's see...

Consider the year-round loss of ice thickness due to thermal conduction from a 1-degree-C-warmer layer at a 50 meter depth.



Upwards heat flux = (temperature gradient) x (thermal conductivity) = 2e-2 K/m x 0.6W/mK = 1.2e-2 W/m^2

Thermal energy added to ice in 1 year = (Upwards heat flux) x (time in 1 year) = 1.2e-2 W/m^2  x 3.1e7 s = 3.7e5 J/m^2; multiply by 1e-4 m^2/cm^2 = 37 J/cm^2

Depth of ice melted = thermal energy added / (heat of melting x density)
= 37 J/cm^2 / (334 J/g x 0.9 g/cm^3) = 0.12 cm depth


So the thickness of ice melted over a year in the above scenario is only of order a millimeter.

Indeed, the thermal conductivity of seawater is insufficient to provide significant melting from deep layers of warmer, saltier water below the ice.

The layer down to the halocline is typically mixed as the ice freezes. Cold briny water is formed from expulsion, sinks and the upper layer becomes mixed.

The strong stratification in the melt season is unlikely to allow much heat to propagate by conduction. I'd expected much more heat to be transferred as ice freezes, and to stop it thickening as quickly throughout the freeze.

Arctic sea ice / Re: 2019 vs 2012
« on: August 04, 2019, 02:48:11 PM »
2019 warmer overall than 2012 during July, much warmer on Atlantic, slightly more warming on Pacific, cooler on Siberian, much cooler on Canadian:

Arctic sea ice / Re: Latest PIOMAS update (August 2019)
« on: August 04, 2019, 09:22:53 AM »
2019-0-31 thickness map, a comparison with previous years and their differences (need clicks for the true size).

Arctic sea ice / Re: Latest PIOMAS update (August 2019)
« on: August 04, 2019, 09:12:40 AM »
Updated volume and volume-anomaly graphs.

Arctic sea ice / Re: Latest PIOMAS update (August 2019)
« on: August 04, 2019, 08:52:00 AM »
PIOMAS gridded thickness data was updated. I calculate volume from the thickness data, gives 6.46 [1000km3] on 2019-07-31. Lowest for the day with a small margin with 2012 (6.68 [1000km3]).

Here is the animation.

Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 04, 2019, 08:26:23 AM »
Total extent drop -93.6k, it is eating into the CAB now as well (-38.2k). Here is a diff with the previous day.

Bright red/blue: loss/gain of extent (crossing the 15% concentration limit). Light red/blue:  concentration change more than 7%. 

Click for the hi-res picture.

Arctic sea ice / Re: Slater's thread
« on: August 03, 2019, 09:17:22 AM »
What do you mean by "Slater" and what by "thread" ???   :o :o

Arctic sea ice / Re: The 2019 melting season
« on: August 02, 2019, 04:17:35 PM »
2019 definitely appears to be one of the worst years on this date. How bad will this melt season end up compared to previous worst years? Too early to tell?
Yes, too early. I see that unusually large amount of ice is now in the state which allows quick and massive melt under GAC-like conditions, by either low thickness, high fragmentation or both. In the same time i see large amounts of ice which are just barely enough thickness to survive if it'll be not too much wind and not too much insolation. I.e., the season arrived to the point where weather decides unusually much. And since "usual" is already pretty much - yep, too early to tell.

Arctic sea ice / Re: 2019 sea ice area and extent data
« on: August 02, 2019, 02:34:22 PM »
While at it, a near double century extent drop today. Here is the latest diff map to answer the question "where?".

Arctic sea ice / Re: The 2019 melting season
« on: August 02, 2019, 02:13:02 AM »
Well, this system is not particularly large, but the forecast for Barrow is quite windy for the next few days - today certainly looks the part. I just added a small screenshot from windy dot com to show what's driving the waves:

Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 01, 2019, 10:52:34 PM »
mercator salinity 34m with unihamburg amsr2-uhh overlay, mar21-jul30

Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 01, 2019, 10:51:19 PM »
noaa bathymetry with unihamburg amsr2-uhh overlay, mar21-jul29

Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 01, 2019, 10:47:18 PM »
Reposting these for reference.
noaa bathymetry with unihamburg amsr2-uhh overlay, september minimums 2012-2018

Arctic sea ice / Re: 2019 sea ice area and extent data
« on: August 01, 2019, 08:10:53 PM »
Central Arctic Sea area graph attached.

Makes one think.
Makes one think that the only difference is the extra ice near Svalbard, ice that does not have CAB characteristics and is relatively easy to melt.

Gerontocrat was talking about area, not extent.  It's not just the extra ice near Svalbard.  Most of the CAB looks "whiter" in 2019 than in years like 2012 or 2016 for the NSIDC sea ice concentration images.  Comparison 2019 vs. 2012:

Arctic sea ice / Re: Slater's thread
« on: July 29, 2019, 01:38:03 PM »
it doesn't do them 50 days in advance. It does them on the same day, different amounts in advance. e.g. on Aug 1st 31 days ahead for Sept 1st, 32 days ahead for Sept 2nd etc.

It does??

I don't think so. Could be wrong, but I don't think he implemented anything other than the 50-day projection. The SIPNs I checked for June and July are labelled "Slater - Persistence", which I assume is just anomaly persistence (the other line on the graph) not the model we are discussing. Only August SIPNs have the model prediction, at least the year I checked.

From the executive summary of the latest submission.

"Forecasts issued on July 1 for September have lead times spanning 62 to 91 days."

Looking through the history it seems this is an innovation of Barrett and Slater did indeed use multiple starting days at the same lead time while Barrett uses the Slater model with one starting day at multiple lead times.

Arctic sea ice / Re: 2019 sea ice area and extent data
« on: July 29, 2019, 09:35:55 AM »
Attached is a graph showing cumulative losses from August 1st to the minimum.

Despite starting with a lower extent each decade, the area lost is increasing each decade.  2012 shows up as a real outlier with the difference between 2nd placed 2016 (2.30M) and 2012 (2.90M) almost  matching the difference between 2016  and the 1980's average (1.58 M).

Note that  2008 lost 2.46M so 2016 is actually third, but I'd left  the noughties out  of the graph.

Arctic sea ice / Re: Slater's thread
« on: July 28, 2019, 02:23:25 PM »
If the Slater model instead used today's data for the 1 September prediction then it would have more skill than the point shown on the plot because it would be a 36-day prediction rather than a 50-day prediction.

Almost certainly true. That would be a model refinement. Slater even insinuates that he was thinking about doing that at some point:

Each day is forecast independently of all other days i.e. I currently do not forecast for days 1 to 49.
[Emphasis added.]

But this has to do with accuracy, not interpretation.

So the model hasn't really been optimized for finding the extent minimum - that's not its purpose.

Good point. Eyeballing at the results over different years in the poster (linked above), the model is often not that great in predicting the timing nor exact value of the single-day minimum. Presumably that why he presents a comparison of Sept. averages instead.

Arctic sea ice / Re: 2019 vs 2012
« on: July 28, 2019, 03:41:39 AM »
Screenshots from
"Arctic Sea Ice Score Card: Extent, Area, Concentration, Volume, & Thickness - 2019 vs. 2012"
17-page PDF at
(but that server is misbehaving 7/27/2019, should be fixed by Monday).

2012vs2019 NSIDC concentration images

Arctic sea ice / Re: Slater's thread
« on: July 28, 2019, 12:00:41 AM »
The model does not project the minimum but a point in time 50 days ahead.
It also does not project the path to that point.
Both these assumptions were made on the melting season thread today. I think this is what ticked RR off.
You can guess the path from now to t+50. If point t+55 suddenly goes up 5 days from now, you can assume the whole imaginary path from t+5 to t+55 has moved upwards.

Arctic sea ice / Re: Arctic Image of the Day
« on: July 27, 2019, 03:50:32 PM »
One of my Facebook friends commented on this picture which is how I got to see it - I've no idea where it is or who took the picture, but somewhere in Greenland seems most likely. Iceland or Norway do not have glaciers calving into the sea, but I think Alaska has ... anybody able to throw more light on this?

It's in Svalbard

Older Image is from March 1928

Arctic sea ice / Re: Arctic Image of the Day
« on: July 27, 2019, 03:01:20 PM »
One of my Facebook friends commented on this picture which is how I got to see it - I've no idea where it is or who took the picture, but somewhere in Greenland seems most likely. Iceland or Norway do not have glaciers calving into the sea, but I think Alaska has ... anybody able to throw more light on this?

Arctic sea ice / Re: 2019 sea ice area and extent data
« on: July 27, 2019, 02:13:57 PM »
Today NSIDC's diff map (dark blue/red shows ice extent in/decreases. Light blue/red where ice concentration increased/decreased more than 7%) shows the ice pack retreating along the Beaufort/Chukchi/ESS ice edge.

Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: July 27, 2019, 11:26:34 AM »
whoi itp110 almost certainly in open water looking at today's lovely clear worldview image. itp103 rough location is also circled. Buoy temperature settling down to 2-3C. PAR on the sami still very high.
@Bruce Steele do you think the internal buoy temperature is a reasonable indication of SST now that most of the buoy is sitting in water.

Arctic sea ice / Re: The 2019 melting season
« on: July 27, 2019, 12:50:42 AM »
And the High has set in motion CAB ice towards the Beaufort again. I can’t explain how loose the Beaufort-CAB must be after so much export since May.
It is a fact all this ice has been melting completely, I can’t see a serious increase of ice over Beaufort.
So from a “macroscopic” point of view we know the huge floes end up being water since Beaufort extent and area are going down (lately faster)
From a “microscopic” point of view I suspect alternating heat and storm mechanical energy provides the cascade of churning into smaller floes in self-similar fashion and final melting of the smallest floes in a matter of one month, as s.i.s. illustrated.

The similarity with turbulence is striking: the big floes are the big eddies, the floes are broken into smaller floes without melt playing a primary role but rather mechanical forces just as the big eddies break into smaller eddies without viscosity playing a primary role, and finally the smallest floes are dominated by melt and are finished quickly, just as the Kolmogorov-scale eddies are small dominated by viscosity and rapidly dissipated.

What is the “Kolmogorov scale” of these Beaufort polynya? It’s a floe size that takes similar time in breaking mechanically than going away by top bottom and lateral melt. PhD material.
What is the self similar exponent in a log(1/size) vs log(1/Number)? PhD stuff

Arctic sea ice / Re: The 2019 melting season
« on: July 26, 2019, 10:29:40 PM »
Take your pick. dmi, hycom jul3-25 and piomas jul3-15
click to run

Arctic background / Re: Arctic Maps
« on: July 26, 2019, 09:59:51 PM »
I talk a lot about the northern parts of the CAA. Here's my effort at assembling a more comprehensive map. I've... probably overlooked some names, and didn't bother with most of the minor islands. But this should suffice. Sorry that the numbers aren't in much of any order. Islands are in red, named water features in dark green.

Islands of the northern CAA
1 Prince Patrick Island
2 Eglinton Island
3 Melville Island
4 Brock Island
5 Emerald Isle
6 Mackenzie King Island
7 Borden Island
8 Ellef Ringnes Island
9 Meighen Island
10 Axel Heiberg Island
11 Ellesmere Island
12 Amund Ringnes Island
13 Lougheed Island
14 King Christian Island
15 Cornwall Island
16 Graham Island
17 Bathurst Island
18 Little Cornwallis Island
19 Cornwallis Island
20 Devon Island
21 Byam Martin Island
22 Banks Island
23 Victoria Island
24 Stefansson Island
25 Prince of Wales Island
26 Somerset Island
27 Baffin Island
28 Greenland

Water of the northern CAA
1 Arctic Ocean
2 M'Clure Strait. Part of the Parry Channel.
3 Crozier Channel
4 Kellett Strait
5 Fitzwilliam Strait
6 Ballantyne Strait
7 Wilkins Strait
8 Prince Gustav Adolf Sea
9 Peary Channel
10 Sverdrup Channel
11 Massey Sound
12 Kane Basin. Nares Strait is just north of here.
13 Baffin Bay
14 Norwegian Bay
15 Hassel Sound
16 Danish Strait
17 Maclean Strait
18 Hazen Strait
19 Hecla and Griper Bay
20 Byam Martin Channel
21 Desbarats Strait
22 Belcher Channel
23 Jones Sound
24 Glacier Strait
25 Lady Ann Strait
26 Lancaster Sound. Part of the Parry Channel.
27 Barrow Strait. Part of the Parry Channel.
28 Wellington Channel
29 Penny Strait
30 Austin Channel
31 Byam Channel
32 Viscount Melville Sound. Part of the Parry Channel.
33 Liddon Gulf
34 Beaufort Sea
35 Prince of Wales Strait
36 M'Clintock Channel
37 Peel Sound
38 Prince Regent Inlet
39 Admiralty Inlet
40 McDougall Sound
41 Nansen Sound
42 Greely Fjord
43 Eureka Sound

Arctic sea ice / Re: The 2019 melting season
« on: July 26, 2019, 09:24:53 PM »
@jdallen, Yeah definitely. Bottom melt gradually ramping-up , all that mess over Beaufort ESS and even Laptev has time to melt out. August + 3 weeks ahead, and bottom melt doesn’t stop until end of october for the warmest ocean areas.
BTW water warmed by radiation can mix with water beneath the ice. A slow process enhanced with movement. Why people think now it’s like oil on water? In the Beaufort certainly the salinity differences are relatively small.
And even part of Chukchi water can mix while in the shelf before sinking. We see those fingers that the currents form causing eddies engulfing half the warm water and half the pack. After mixing, which takes time in those structures , density stratification is less prone to happen and water temperature beneath the ice must increase.
I don’t believe that the fast edge retreats we observe in late years is not directly enhanced by warm currents from Pacific.

It's been well observed that the ice edge tracks bathymetry. The Barents continental slope often delimits the edge of the sea ice between the Barents Sea and the Arctic. This season the ice  pretty much tracks the continental slope of the Canadian Basin, except in the most southerly regions, the Beaufort. The reason is that the typically saline ocean waters cool and sink as they meet the ice edge, and that water can only sink when it reaches the continental slope.

Water temperature beneath the ice in the basins does increase at depth, but it doesn't mix with surface waters. Ice melts from the edges for a good reason. If the central pack is to melt, it isn't going to be from mixing with warm water from adjacent seas unless the ice gets spread out and deeper waters are mixed by a GAC. The Atlantic water under the Nansen basin already contains enough heat to melt all the ice. The pack will melt because it's thin and from the weather, insolation and air that is extra warm and wet because the peripheral seas have little ice.

Ice melts from the bottom, because the salinity means that it can melt at lower temperatures. if the surface of the ice is at 0°C and the base -1.8°C, any heat input into the system will melt the base at equilibrium, and not the surface. It's a balance between the conductivity of the ice, it's thickness, and how much energy is being put into the surface.

Arctic sea ice / Re: The 2019 melting season
« on: July 26, 2019, 08:24:54 PM »
So my major doubts are with the US Navy's HYCOM gifs.
Jokes aside, sure, doubt is for every model, some more, some less. But there is one thing unique about US Navy's Arctic Ice matherials - which is, those guys actually go there all the time. They can and certainly do verify their model's results with actual measurements. This among other things is also military matter: certain subs have certain limits about how thick ice they can push through, and thus it's important to know where both sides' subs can possibly appear and fire away.

Arctic sea ice / Re: The 2019 melting season
« on: July 26, 2019, 02:56:01 AM »
July 10-24, 3 day lagging median.

Pacific side retreat accelerated considerably in the last few days. Beaufort retreating despite continued import. ESS hanging on by the skin of its teeth. Huge area north of Laptev flashing on and off, maybe on the verge of staying "yellow" (<80% concentration). Southern CAA purple (>90%) to green (<70%) in less than a week.

Click to animate.

Arctic sea ice / Re: The 2019 melting season
« on: July 25, 2019, 10:14:50 PM »
After a period of relative immobility, impressive ice movement today.

Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: July 25, 2019, 03:21:33 PM »
In this particular case, what are we looking for in a temperature vs salinity chart? I ask because it may be a more efficient way of diplaying the profiles.

Salinity is usually used as a marker for layers of water. Usually, S between 31 and 33 is thought to be the Pacific Warm Water but a freshening of warm waters is ongoing and should increase instability of the water column, as S is around 28 near surface, with the risk that this warmth make surface by mixing. At greater depth, the max at around S=35 is Atlantic water. In Summer, water are fresher (sea ice melt, water runoff) and warmer, with a positive trend due to warming (water source from Chukchi sea is fresher and fresher, warmer and warmer). This is showing in the Beaufort Gyre, with a higher max in temperature at lower salinity for the Pacific Water Layer. There was even some ITP profiles with a Tmax with salinity near 30, and a Tmin with salinity near 28... of course freshening of Pacific Water must reach a limit, and in the same time, as said by Bruce Steele, the warming of Chukchi Sea will shut down the donwelling. I am not sure where we are going, but here we go. And the Ocean is definitively heavily disturbed, there is way too much heat which was accumulated this season, and it is not over.

Inspired by your salinity movies, uniquorn, the illustration below is a suggestion for displaying the actual physical data they are based upon.

It would give a 'traffic light' of salinity at e.g. 0m, 30m, and 100m at the location of each recording device on that date - whether from a tethered buoy, drifting buoy or a ship.

My main immediate motivation in suggesting this is that it would allow a movie that extends back before the June 2017 start of the mercator display movie that uniquorn posted here on the 2019 melting season thread. That would give us a longer term view of how the salinity has changed.

I realize that it would probably be a lot of work to make this, but I think to could be a useful visualization tool. The picture is just an illustrative cartoon - I'm hoping someone will be kind enough and interested enough to produce such a display, or similar, using the actual data. (It's beyond my own personal skills at the moment, unfortunately.)

This said also, Mercator is not seeing the warming and freshening of Pacific Water... The profile is for the model where the ITP buoy made the 601th profile, on the 19th July of this year (cf. above). Quite a difference. And the same on the 19th still, over northern Chukchi sea. For making a movie, I think I don't have the time, nor the motivation, nor the bandwith :s

Arctic sea ice / Re: The 2019 melting season
« on: July 25, 2019, 07:14:55 AM »
Slow Wing, here's a simple line from this page, which is about actual measurements of insolation at Barrow (which is quite far from the Pole, but still should be good enough to solve your doubts about how much reaches the surface):

"... maximum daily incident solar radiation (330-360 W m-2) at the surface".

P.S. And just to be safe, note that monthly mean insolation for July at Barrow, given on the same page - is appropriately low 120-130 W/m2 at the surface, as it includes all the cloudy days, which for July at Barrow is ~75% days of the month (source). This also well demonstrates how dramatic is the difference between clear skies and clouds in terms of insolation.

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