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Dharma Rupa

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Re: The 2018 melting season
« Reply #3150 on: August 28, 2018, 07:57:10 PM »
DMI 80N continues to drop rapidly.

???  I don't see how you can say anything about how DMI 80N is doing at the moment, and certainly not that it is dropping rapidly.  There is a slight indication that the Winter Cold will be somewhat delayed once again, but it is way too soon to say so.

Phil.

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Re: The 2018 melting season
« Reply #3151 on: August 28, 2018, 08:17:31 PM »
DMI 80N continues to drop rapidly.

???  I don't see how you can say anything about how DMI 80N is doing at the moment, and certainly not that it is dropping rapidly.  There is a slight indication that the Winter Cold will be somewhat delayed once again, but it is way too soon to say so.

Indeed, still above the average for today and above the freezing point for salt water. 

NeilT

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Re: The 2018 melting season
« Reply #3152 on: August 28, 2018, 10:22:20 PM »
???  I don't see how you can say anything about how DMI 80N is doing at the moment, and certainly not that it is dropping rapidly.

I think 2C in a few days is fairly rapid.

Also DMI 80N is a "mean" temperature.  See all that open water, inside 80N on the Atlantic side. That's WAY over 0C.

So in order for the "mean" to be negative, it means that a rather large chunk of the CAB is way below 0C.

The temperature may be way above water freezing point, but that is not the point.  It is now way below the point at which ice, on the surface, stops melting.

Temperatures are starting to go south.  Extent loss, at least, is starting to pause.

It is not very hard to see what is happening.  Even with a storm, if the local temp is well below 0C, then any precipitation will hit the ground as snow.

I'll be happy to stand corrected if the whole area starts to melt rapidly.  But the trend is not that way and it is, in the end, the trend which will determine the final result.
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gerontocrat

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Re: The 2018 melting season
« Reply #3153 on: August 28, 2018, 10:38:55 PM »
Air and Ocean Temps.

Air first 2 images
Air Temps North of 80 are getting colder quickly . Area north of 80 is a small fraction of the total Arctic. The Arctic is getting colder but temps are on average around 1 to 1.5 degrees celsius above average with large variations across the Arctic.

Sea Images 3 and 4
SST anomalies have risen sharply in the Arctic. Image 3 is 27 August ; cf Image 4 - 16 July.

So we have the classic end of season contrast - will wind, waves, and currents cause bottom melt to be greater than surface freeze for some time to come.
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oren

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Re: The 2018 melting season
« Reply #3154 on: August 28, 2018, 11:29:51 PM »
DMI N of 80 is not a true average, it is weighted by degrees not by area which makes it skewed hard for the north pole. So don't jump to too many conclusions when the number drops below 0c or even -1.8c. Melting season is almost done, but not quite yet.

Michael Hauber

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Re: The 2018 melting season
« Reply #3155 on: August 29, 2018, 12:02:07 AM »
MODIS 3-6-7 channel shows nearly total cloud cover of the Arctic, but what shows in between the clouds suggests that the surface is mostly frozen and that the surface melting season is mostly over.

A thought on the current cyclone, forecast to continue for the forseeable future.  SSTs are close to their seasonal max now, mixing and winds will cool them faster (but clouds keep the heat in).  But mixing may also push some of the heat below the surface to impact the start of the freeze season.  In contrast if the heat is left undisturbed near the surface in calm conditions it might be lost much quicker as Arctic night falls.  Ekman pumping will produce upwelling mostly in the central ice pack and presumably this will need to be balanced by downwelling somewhere in the Arctic fringes which might also push heat below the surface.
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uniquorn

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Re: The 2018 melting season
« Reply #3156 on: August 29, 2018, 01:25:00 AM »
As the melting season is nearly over, for 'fun' I present some cherry picking on windy. The daily post will confirm or confound.

Eco-Author

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Re: The 2018 melting season
« Reply #3157 on: August 29, 2018, 01:40:16 AM »
When these storms come through, interesting to see how it breaks up the ice... one might expect bigger ice burgs for a given thickness so if it really is like slush... it should show more like Beaufort looked late july. We can only assume we are at an early start to above average 80-N temps bound to spike just as much as spring... If there is a next area to begin to go ice free a large portion of the winter like Bering and Svalvard… Laptev has an open crack most of the year too... and now this.  adding some late season stirring by two or three storms in a row to start only to continue at least once a month all winter long on average it seems.   
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magnamentis

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Re: The 2018 melting season
« Reply #3158 on: August 29, 2018, 03:39:58 AM »
When these storms come through, interesting to see how it breaks up the ice... one might expect bigger ice burgs for a given thickness so if it really is like slush... it should show more like Beaufort looked late july. We can only assume we are at an early start to above average 80-N temps bound to spike just as much as spring... If there is a next area to begin to go ice free a large portion of the winter like Bering and Svalvard… Laptev has an open crack most of the year too... and now this.  adding some late season stirring by two or three storms in a row to start only to continue at least once a month all winter long on average it seems.

to be honest, i expected a much higher impact of the recent wave and wind action, especially when it comes to the arm that extents into ESS and basically not much happened recently, not even the reminder in the beaufort has gone, hence i don't expect much out of the ordinary for the rest of the melting season, but then i might again be wrong, watching with interest.

magnamentis

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Re: The 2018 melting season
« Reply #3159 on: August 29, 2018, 04:09:10 AM »
I think 2C in a few days is fairly rapid.

if we want to know if it's rapid we have to define to what we compare.

since the recent drop is more or less parallel to the average curve but still significantly above that curve i consider the recent drop as normal and no matter if that is rapid or not, even if it is rapid, it's normally rapid but higher, hence not worth a mention that makes the impression that something out of the ordinary is happening.

looking at the attached image i'd say it's very very warm in the arctic and way above average in general, everything else is noise IMO.

slow wing

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Re: The 2018 melting season
« Reply #3160 on: August 29, 2018, 05:53:30 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-08-28...

bbr2314

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Re: The 2018 melting season
« Reply #3161 on: August 29, 2018, 05:57:35 AM »
The impending doom in Laptev is legit. Clouds are masking Bremen severely IMO. But wow! The front is going to be worse than any other year across almost the entirely NATL including Laptev instead of just N/NE of Greenland, imminently.

NeilT

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Re: The 2018 melting season
« Reply #3162 on: August 29, 2018, 11:01:53 AM »
if we want to know if it's rapid we have to define to what we compare.

since the recent drop is more or less parallel to the average curve but still significantly above that curve i consider the recent drop as normal

I think the average heat drop is fairly rapid at this time of the year.  The CAB usually switches form melting to freezing, the periphery, warmed for much of the summer, is warm, but starts to cool.

I was saying the trend is now towards cooling.  Of course any change like this will change the weather and may bring in storms and a drop in both heat and pressure may suck in heat.

But the point is the heat source is going out for the year and the environment is reacting to it.  Therefore, if the trend is the norm, we'll be heading towards the end of the season in the next two weeks or so.

Whilst the ESS may be breaking down a bit more, the Beaufort side of the CAB is firming up.  More melt to go on the Atlantic side/Laptev, for a bit, but even there the ice into the CAB is not quite disintegrating despite the heat.

Likely to be as interesting an Autumn as it was a Spring, as has already been said.
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Re: The 2018 melting season
« Reply #3163 on: August 29, 2018, 12:02:53 PM »
What this, another GAC-less year, can bury is the 2012 fallacy of "it would have melted anyway". Errr not so sure.

uniquorn

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Re: The 2018 melting season
« Reply #3164 on: August 29, 2018, 01:59:09 PM »
A comparison of aug27 from 2012-2018 using amsr2-uhh (890kB).
Today's wave and temps from windy.
edit:ESS, aug1-28, amsr2-uhh (1.6MB,15th missing)
« Last Edit: August 29, 2018, 04:53:54 PM by uniquorn »

bbr2314

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Re: The 2018 melting season
« Reply #3165 on: August 29, 2018, 06:09:11 PM »
What this, another GAC-less year, can bury is the 2012 fallacy of "it would have melted anyway". Errr not so sure.
I don't think it is fair to say this year was GAC-less, the June event was about as impressive as 2012, it just happened far earlier in the melt season.

FishOutofWater

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Re: The 2018 melting season
« Reply #3166 on: August 29, 2018, 06:40:09 PM »
He was correct to say there was no GAC. Moreover, storms in June and July block insolation, cooling the central Arctic. The relatively high sea ice extent this late August compared to 2012 is directly related to the weather of summer 2012 and the GAC versus this summer's weather. Moreover, the GAC lasted long enough to pull up ocean heat from well below the ocean surface and melt more ice than we've seen in years with weaker and less persistent storms. However, the ocean heat loss and low ice extent may have increased radiation of heat to space, helping to lead to a partial ice recovery in 2013 and 2014.

magnamentis

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Re: The 2018 melting season
« Reply #3167 on: August 29, 2018, 08:18:41 PM »
He was correct to say there was no GAC. Moreover, storms in June and July block insolation, cooling the central Arctic. The relatively high sea ice extent this late August compared to 2012 is directly related to the weather of summer 2012 and the GAC versus this summer's weather. Moreover, the GAC lasted long enough to pull up ocean heat from well below the ocean surface and melt more ice than we've seen in years with weaker and less persistent storms. However, the ocean heat loss and low ice extent may have increased radiation of heat to space, helping to lead to a partial ice recovery in 2013 and 2014.

that about sums it up, especially but not exclusively the last part.

ael

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Re: The 2018 melting season
« Reply #3168 on: August 29, 2018, 08:25:11 PM »
The Independent says:

A warm region of water trapped deep below the surface of the Arctic seas north of Canada has the potential to leave the entire area devoid of ice.  Scientists have discovered warmer water that originated hundreds of miles away has penetrated deep below the ice pack’s surface.


https://www.independent.co.uk/environment/arctic-sea-ice-melting-warm-water-trapped-polar-canada-yale-university-perfect-a8513176.html

vox_mundi

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Re: The 2018 melting season
« Reply #3169 on: August 29, 2018, 08:30:47 PM »
Archived' heat has reached deep into the Arctic interior, researchers say

Quote


 Arctic sea ice isn't just threatened by the melting of ice around its edges, a new study has found: Warmer water that originated hundreds of miles away has penetrated deep into the interior of the Arctic.

That "archived" heat, currently trapped below the surface, has the potential to melt the region's entire sea-ice pack if it reaches the surface, researchers say.

The study appears online Aug. 29 in the journal Science Advances.

"We document a striking ocean warming in one of the main basins of the interior Arctic Ocean, the Canadian Basin," said lead author Mary-Louise Timmermans, a professor of geology and geophysics at Yale University.

The upper ocean in the Canadian Basin has seen a two-fold increase in heat content over the past 30 years, the researchers said. They traced the source to waters hundreds of miles to the south, where reduced sea ice has left the surface ocean more exposed to summer solar warming. In turn, Arctic winds are driving the warmer water north, but below the surface waters.

"This means the effects of sea-ice loss are not limited to the ice-free regions themselves, but also lead to increased heat accumulation in the interior of the Arctic Ocean that can have climate effects well beyond the summer season," Timmermans said. "Presently this heat is trapped below the surface layer. Should it be mixed up to the surface, there is enough heat to entirely melt the sea-ice pack that covers this region for most of the year."
  "Warming of the interior Arctic Ocean linked to sea ice losses at the basin margins" Science Advances (2018)
http://advances.sciencemag.org/content/4/8/eaat6773

Sorry if this was already posted (or it's in the wrong thread)
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afwhitaker

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Re: The 2018 melting season
« Reply #3170 on: August 29, 2018, 08:51:37 PM »
The independant says.

"Using data collected over the past 30 years, researchers at Yale University and Woods Hole Oceanographic Institution saw the “heat content” of the area had doubled during this period."

 That statement is suspect.

FishOutofWater

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Re: The 2018 melting season
« Reply #3171 on: August 29, 2018, 08:59:07 PM »
What happens in the Chukchi doesn't stay in the Chukchi. The heat from insolation on the increasingly ice free region north of the Bering strait makes its way from the Chukchi sea to the CAA. The moderately salty modified Pacific water heats in the summer, then sinks in the fall, carrying heat below the pycnocline. That water eventually is transported towards the Canadian Arctic and the passages of the CAA. We can see the effects of the heat in the Mercator Ocean animations of the 100m layer.

http://advances.sciencemag.org/content/4/8/eaat6773



Abstract


Arctic Ocean measurements reveal a near doubling of ocean heat content relative to the freezing temperature in the Beaufort Gyre halocline over the past three decades (1987–2017). This warming is linked to anomalous solar heating of surface waters in the northern Chukchi Sea, a main entryway for halocline waters to join the interior Beaufort Gyre. Summer solar heat absorption by the surface waters has increased fivefold over the same time period, chiefly because of reduced sea ice coverage. It is shown that the solar heating, considered together with subduction rates of surface water in this region, is sufficient to account for the observed halocline warming. Heat absorption at the basin margins and its subsequent accumulation in the ocean interior, therefore, have consequences for Beaufort Gyre sea ice beyond the summer season.


The effect of this heat may be profound because it may open up the passages of the CAA for longer periods of time each year, increasing the amount of transport of Arctic ocean ice and water through the passages of the CAA into the Labrador Sea. That may be happening as we speak.
« Last Edit: August 29, 2018, 09:22:10 PM by FishOutofWater »

GoSouthYoungins

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Re: The 2018 melting season
« Reply #3172 on: August 29, 2018, 09:06:34 PM »
The Independent says:

A warm region of water trapped deep below the surface of the Arctic seas north of Canada has the potential to leave the entire area devoid of ice.  Scientists have discovered warmer water that originated hundreds of miles away has penetrated deep below the ice pack’s surface.


https://www.independent.co.uk/environment/arctic-sea-ice-melting-warm-water-trapped-polar-canada-yale-university-perfect-a8513176.html

Interesting article. Nothing directly to do with 2018 (looking at changes from 1987-2017). However, extrapolating the article's findings to the past year is very interesting. The summary of the article is that as the Chukchi Sea has absorbed summer sunlight, the heat as been pulled into the Beaufort Gyre but remains stratified under a colder and less salty layer. Since this year had a uniquely early retreat in the Bering Sea, it is likely that the trend of heating has increased. If so, Beaufort might join, Chucki, Bering, Laptev, Barents, and Greenland seas in a historically terrible freezing season. Only ESS looks reasonable.  :(


Actual paper being reference:

http://advances.sciencemag.org/content/4/8/eaat6773

big time oops

FishOutofWater

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Re: The 2018 melting season
« Reply #3173 on: August 29, 2018, 09:51:35 PM »
The original article does an excellent job of explaining how the heat from the Chuckchi gets buried below the surface layers in the Beaufort gyre.

The source of the increased halocline heat content can be understood by first considering how the BG halocline is ventilated. The northern Chukchi Sea (NCS) region exerts major influence on the interior structure of the halocline; here, water masses with the salinity range of the warm halocline outcrop at the surface (11). In this region, which we define to be within 70°N to 75°N and 150°W to 170°W, and south of the 300-m isobath (Fig. 2E), water is pumped down from the surface (via the Ekman transport convergence as a result of the prevailing anticyclonic wind stress gradients) and transported laterally by the BG geostrophic flow into the interior gyre (9, 11). Observations suggest that the NCS is characterized by the strongest time-mean Ekman downwelling in the entire Canada Basin, with downwelling rates averaging around 20 m year−1, which corresponds to a vertical Ekman flux of around 0.05 Sv (1 Sv = 106 m3 s−1) for the region (12). This strong downwelling, associated with the region of maximum strength of the prevailing easterlies, takes place year-round with some interannual variability, but no significant trend over 2003–2014 [see Figs. 4 to 6 in (12)].

Note that heat has been building up for decades and has expanded through the Beaufort gyre towards the CAA for many years. The heat is only slowly diffused back towards the surface water layer (according to the diffusion equation also known as the heat equation). However, the continental shelf margins have physical upwelling due to Ekman divergence. Heat may well back up at the continental shelf of the CAA. (This last issue is my interpretation, not in the paper.)

While vertical heat fluxes from the warm halocline are inhibited by the halocline stratification (that is, diapycnal diffusion is weak), reasonable estimates for heat lost vertically from the warm halocline may be obtained by considering the range of turbulent diffusivities estimated from observations in the central Canada Basin halocline: ~10−7 to 10−6 m2 s−1 (20). Heat loss is only considered across the top boundary of the layer. The range of diffusivities acting on the vertical temperature gradient centered around S = 31 (the top of the warm halocline) gives rise to upward heat fluxes in the range of 0.03 to 0.3 W m−2. Taking the heat content in the layer to be ~4 × 108 J m−2, these fluxes suggest a time scale for diffusive removal of the anomalous layer heat of between 40 and 400 years. Therefore, we cannot rule out that some fraction of the subducted summer heat is lost from the layer by vertical diffusion. Note that eddy fluxes may also be responsible for transporting heat laterally out of the BG region in a dynamical response to the wind-energy input (21).
« Last Edit: August 29, 2018, 10:11:03 PM by FishOutofWater »

bluesky

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Re: The 2018 melting season
« Reply #3174 on: August 29, 2018, 10:08:13 PM »
interesting hard data regarding the impact of doubled heat content in the halocline over 30 years, on sea ice melt, adding 0.8m in thickness of melting:

"Over the period 1987–2017, total warm halocline heat
content integrated horizontally over a region encompassing the BG has
nearly doubled (Fig. 3A). It is instructive to set the resulting heat content
increases in context alongside sea ice. The capacity for sea ice melt of the
additional heat content (the increase of ~2 × 108 J m−2 over 30 years)
equates to a change of about 0.8 m in thickness, taking the latent heat of
melting to be 2.67 × 105 J kg−1 and the density of sea ice to be 900 kgm−3."

Michael Hauber

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Re: The 2018 melting season
« Reply #3175 on: August 29, 2018, 11:01:54 PM »

I don't think it is fair to say this year was GAC-less, the June event was about as impressive as 2012, it just happened far earlier in the melt season.

The June event was close when considering minimum pressure.  Not very close when considering size of circulation, or duration.
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Shared Humanity

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Re: The 2018 melting season
« Reply #3176 on: August 29, 2018, 11:35:52 PM »
The independant says.

"Using data collected over the past 30 years, researchers at Yale University and Woods Hole Oceanographic Institution saw the “heat content” of the area had doubled during this period."

 That statement is suspect.

With two posts on this site, don't take it personal but so are you. It would help your case if you would explain your reasoning.

gerontocrat

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Re: The 2018 melting season
« Reply #3177 on: August 29, 2018, 11:36:19 PM »
interesting hard data regarding the impact of doubled heat content in the halocline over 30 years, on sea ice melt, adding 0.8m in thickness of melting:

"Over the period 1987–2017, total warm halocline heat
content integrated horizontally over a region encompassing the BG has
nearly doubled (Fig. 3A). It is instructive to set the resulting heat content
increases in context alongside sea ice. The capacity for sea ice melt of the
additional heat content (the increase of ~2 × 108 J m−2 over 30 years)
equates to a change of about 0.8 m in thickness, taking the latent heat of
melting to be 2.67 × 105 J kg−1 and the density of sea ice to be 900 kgm−3."
That is 80 cms from accumulated additional heat stored at depth over 30 years, i.e. equivalent to  the energy required to melt just under 3 cms of the BG area each year ? And this is just from solar absorption from additional open water in the Chukchi Sea. Goodness knows how much heat being stored at depth from the Atlantic and solar absorption from additional open water in seas on the Atlantic side.

But this is not likely to affect this end of season fortnight. I attach 3 images from GFS on 5 day outlook averages. 3 days, 5 days, 10 days all look the same. High pressure around the Arctic, low pressure in the Arctic. A lot of southerly winds and moisture from the N Atlantic. Arctic warmer than average.
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Wherestheice

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Re: The 2018 melting season
« Reply #3178 on: August 29, 2018, 11:36:57 PM »
I heard somewhere that two cyclones were in the Arctic rn, is that true?
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FishOutofWater

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Re: The 2018 melting season
« Reply #3179 on: August 30, 2018, 12:19:10 AM »
There are 2 lows in the Arctic now and there will be 3 in 48 hours. Melting will continue in the ESS and at the ice pack edge near the Laptev sea.

afwhitaker

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Re: The 2018 melting season
« Reply #3180 on: August 30, 2018, 02:03:59 AM »
The independant says.

"Using data collected over the past 30 years, researchers at Yale University and Woods Hole Oceanographic Institution saw the “heat content” of the area had doubled during this period."

 That statement is suspect.

With two posts on this site, don't take it personal but so are you. It would help your case if you would explain your reasoning.

You are correct, more information would have helped.  That said Fish out of Water addressed the observation soon after I posted.   The observation was twice the heat compared to what, which ended up being relative to freezing point of water.  Thanks for the feedback not taken personally.

slow wing

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Re: The 2018 melting season
« Reply #3181 on: August 30, 2018, 05:19:35 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-08-29...

Aluminium

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Re: The 2018 melting season
« Reply #3182 on: August 30, 2018, 07:17:26 AM »
August 25-29.

Niall Dollard

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Re: The 2018 melting season
« Reply #3183 on: August 30, 2018, 09:36:00 AM »
Could extend the melt season and leave more year-round open areas (as seen with Nares last winter).


Is that a quotation from a previous article, Thomas ? What winter are you referring to as the Nares strait was not open between March and end June this year.
 

gerontocrat

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Re: The 2018 melting season
« Reply #3184 on: August 30, 2018, 11:04:40 AM »

"Presently this heat is trapped below the surface layer. Should it be mixed up to the surface, there is enough heat to entirely melt the sea-ice pack that covers this region for most of the year."
-- Mary-Louise Timmermans, professor of geology and geophysics at Yale University.
https://www.sciencedaily.com/releases/2018/08/180829143836.htm


The heat is trapped below the surface layer. So this study (which is fascinating) is about how heat has accumulated over the last 30 years at depth due to ice loss in the Chukchi, and is about what may happen in the future if that heat starts travelling up to the surface, and is not about the two or three weeks left of the 2018 melting season.

Indeed, JAXA sea ice extent loss this year is about 0.5 million km2 less than the average for the previous 10 years ,and is really slow at the moment.

Methinks all the postings about this study are in the wrong thread.
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meddoc

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Re: The 2018 melting season
« Reply #3185 on: August 30, 2018, 11:19:51 AM »
I think instead of 15% concentration Extent we should focus on assessing 50% concentration Extent. 15% takes a lot of areas that are basically 85% ice- free into account.

Will be exciting to see the latest PIOMAS graph 1979- 2018 what the Trendline has been doing lately.

FishOutofWater

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Re: The 2018 melting season
« Reply #3186 on: August 30, 2018, 12:35:25 PM »
For most of the past year anomalous heat has entered the Arctic ocean from the Pacific ocean. The melting season started with record low sea ice in the Bering sea. Excess heat and salt have been pouring into the Arctic for many months this melting season. The process described in that paper has gone into overdrive this year and this melting season.

Yet the horse race this melting season is being lost to cool stormy weather in June and July compared to other years. What's really interesting to me about this melting season is how the heat has been pouring in from both the Atlantic and Pacific while sea ice and cold water are flowing out rapidly through the main channel of the CAA. The horse race aspect of the melting season has been pretty boring because of the cloudy weather over the pole in June and July.

http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20170531/20180829/11/1

uniquorn

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Re: The 2018 melting season
« Reply #3187 on: August 30, 2018, 02:02:29 PM »
Today's waves and temps from Windy and Hycom sea surface salinity for this melting season, mar21-aug29 (every 4th day, 3.1MB)
edit: incorrect windy file
« Last Edit: August 30, 2018, 04:04:22 PM by uniquorn »

FishOutofWater

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Re: The 2018 melting season
« Reply #3188 on: August 30, 2018, 03:32:33 PM »
Thanks Uniquorn for the animation. Mercator's animation of SST's shows warm water entering the Arctic at the surface from the Pacific through the Bering Strait for the longest fall season anyone has ever seen. Little Diomede island had surf in late December from a storm that moved from the Pacific into the Arctic. The pattern of subduction of Pacific water in the Chukchi sea described in that paper continued later in the year than has been seen since records began.

However, in summer the storminess shifted from the Pacific side to the Atlantic side and now we're seeing the deepest push towards the pole of Atlantic water (at the surface) on record. We are seeing the lowest extent, area and volume of sea ice in the Greenland sea. Warm, salty, Atlantic water has eddied around the northeastern tip of Greenland onto the northern shores of Greenland. The Lincoln sea is covered with slush and pulverized ice, not the thick floes we saw 3 years ago before it began to flush out through the Nares strait and the CAA's "garlic press".

But the warm salty water that entered from the Pacific is still working its way into the Beaufort sea. It's still adding heat to this summer's melt season. It will be covered by fresh waters that flowed into the Arctic from Siberian rivers, and it will be hidden below the surface, but it will take years before it is flushed from the Arctic.

The weak "horse race" this melting season obscures the simultaneous push of warm salty waters from both the Atlantic and Pacific this summer that are setting the stage for sea ice collapse in coming years. Don't let the cool cloudy weather fool us. The past year has been disastrous for the long-term preservation of Arctic sea ice.

oren

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Re: The 2018 melting season
« Reply #3189 on: August 30, 2018, 05:10:43 PM »
This melting season convinced me that one of the biggest factors of area and extent loss is the prevailing export direction. This year had a pacific-wise export both in winter (the string of thick old ice) and during the melting season.
The Atlantic/Barents/Fram has an endless capacity to melt anything exported into it. Baffin/Nares is the same but the export rate is low. Baffin/CAA is the same but the export channels are usually clogged until very late in the season.
But the Beaufort does not have an endless capacity. It starts opening up and warming rather late, and the heat it imports from the Mackenzie and from the Bering/Alaskan Coastal Current seems to be not enough to kill very large amounts of ice. As evidence, the "blob" which was pushed against the coast is still surviving even after melting in situ for months and then drifting away into warm open water for several days. And this after the lowest ever Bering ice cover this winter, and the latest Chukchi refreeze ever. My expectation was for a very early pacific-side crash, but the opposite happened.
So my conclusion is that in years where there is a prevailing drift towards the Atlantic it is easier to get to low are/extent numbers, compared to years like 2018 where a lot of the export was movement towards the pacific side.
I also suspect that the resilience of the CAA is related to this general drift direction. The "garlic press" has an endless ice supply to feed it.
I am quite certain this "prevailing export/drift" can be quantified and compared across the years, though I am not able to do that myself.
What I wonder about is what factors affect this prevailing direction, or if it is just a random "luck of the season".

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Re: The 2018 melting season
« Reply #3190 on: August 30, 2018, 05:24:48 PM »
I have another analysis :). It was a relatively cold season, until second half of July. But since the state of the ice is what it is since 2007, and since past winter was warm, the pack will end up being an average 2010s thing.
Extremely anomalous is the advance of the Atlantic front. But maybe the anomaly was the absence of ice transport toward the Atlantic which allowed the Atlantified waters to advance so much melting ice beyond what we ve seen other recent years
 
« Last Edit: August 30, 2018, 05:35:32 PM by Sterks »

FishOutofWater

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Re: The 2018 melting season
« Reply #3191 on: August 30, 2018, 05:56:35 PM »
What's so anomalous is that most of the flow out of the Arctic is not through the Fram strait, the Nares strait or the Bering strait. The channels of the CAA are where most of the water and ice is exiting the Arctic ocean. This is literally a sea change.

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Re: The 2018 melting season
« Reply #3192 on: August 30, 2018, 06:33:10 PM »
I am not a meteorologist (half the time I can't even spell the word), but..

The first image is the latest GFS 10 day sea level pressure map. It has been more or less like this since the beginning of June, and gave that very long heatwave in Europe. It also sent a continuous stream of weather systems from the south into the North Atlantic and the Arctic, week after week, month after month.

Compare that with similar maps for August 2016 and 2017. That high is there, but much farther south.  (Same for all the summer months). Those weather fronts therefore tended to hit Western and NW Europe instead of the Arctic.

So "my speculation that belongs to me" is that this has much to do with the Atlantic Front retreating sideways and export down the Fram being blocked..
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Re: The 2018 melting season
« Reply #3193 on: August 30, 2018, 06:43:13 PM »
The latest WaveWatch III forecast for tomorrow evening UTC:

http://GreatWhiteCon.info/2018/08/the-great-arctic-cyclone-of-2018/#Aug-30

Not as ridiculous as 3 days ago, but still very "significant"!
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

uniquorn

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Re: The 2018 melting season
« Reply #3194 on: August 30, 2018, 06:49:56 PM »
I think the volume of ice melted has been quite high. Despite heavy cloud cover, allegedly anomalously thick ice in Laptev and much of ESS has gone, Fram export melted before it got there, the Atlantic front retreated, Beaufort melted the string of MYI and thick ice in the Lincoln Sea has largely gone and as FOoW said, the circulation would appear to have changed, maybe temporarily.
Extent is quite high, so I think, once again, the ice is thinner.

Hycom SST mar21-aug29 (8bit, every4 days, 2.4MB)
 

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Re: The 2018 melting season
« Reply #3195 on: August 30, 2018, 07:03:17 PM »
I think instead of 15% concentration Extent we should focus on assessing 50% concentration Extent. 15% takes a lot of areas that are basically 85% ice- free into account.

People suggest that kind of thing pretty often, with various other thresholds.  One month ago I went back and reanalyzed all the NSIDC data using a 30% cutoff rather than 15%.  The effect was pretty much negligible -- it reduces the extent somewhat, but there's no long-term trend over time.

In other words, it makes it look like there's less ice across the board, but not that the ice is disappearing any faster.

See this post and following ones (the top of the next page includes a .csv file with the results):

https://forum.arctic-sea-ice.net/index.php/topic,2223.msg164660.html#msg164660

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Re: The 2018 melting season
« Reply #3196 on: August 30, 2018, 07:08:49 PM »
It has been more or less like this since the beginning of June, and gave that very long heatwave in Europe.

Finally the Brits and Swedes got to experience real summer! 8)
My friend in Scotland kept whining all summer about the unbearable 25 C temps :)

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Re: The 2018 melting season
« Reply #3197 on: August 30, 2018, 07:09:04 PM »
According to the Canuck's maps, the melt season is probably coming to a close most everywhere in CAA. Snows are now falling, even the blob of ice off AK is now covered. Will wave action result in continual melting for some spots? Yes. But how much more? Outside of the ATL front, probably not too much IMO (and ESS as well).

It is also interesting to note that the recent major storm over Hudson Bay has resulted in very cold SSTs overtaking its entirety. The weather forecast shows persistent -500MB anomalies and cold temperatures here as well. I wonder how early refreeze will begin, especially with a decent amount of ice still lingering in Foxe Basin?

https://weather.gc.ca/saisons/animation_e.html?id=month&bc=sea


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Re: The 2018 melting season
« Reply #3199 on: August 30, 2018, 07:52:40 PM »
Not a lot of ice left in the Foxe Basin, actually.  As of the 29th:

https://gibs.earthdata.nasa.gov/image-download?TIME=2018241&extent=-1682109.5630005335,-2331994.407965242,-1052411.7651436455,-1713271.7351254674&epsg=3413&layers=MODIS_Terra_CorrectedReflectance_TrueColor,Coastlines&opacities=1,1&worldfile=false&format=image/jpeg&width=615&height=604
Not a lot, but it is thick, and it is far more than any other year. 2015 had a clump in the SW corner but in 2018 it is distributed fairly evenly around the periphery.