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Messages - iceman

Pages: [1] 2 3 ... 6
1
Arctic sea ice / Re: The 2019 melting season
« on: September 20, 2019, 12:34:15 PM »
   .... perhaps the "Slow Transition" thread is the right place to discuss "the decades long transition to a new atmospheric circulation"?

Yes please. Sam's points are worth considering, but will be lost a year from now unless posted in the appropriate thread.

2
Arctic sea ice / Re: The 2019 melting season
« on: September 15, 2019, 04:08:34 PM »
A "low bandwidth" animation of Arctic sea ice age since the 2015 minimum:

Nicely done. If you knew this cycle only from the 1990s, you would be astonished to watch the Beaufort arm getting wiped out at the end of each melt season.
    So the old ice in the ESS arm four years ago becomes nearly the last extant sliver north of the CAA.

3
Arctic sea ice / Re: The 2019 melting season
« on: August 20, 2019, 01:31:39 PM »
update on caa/cab crack, unihamburg amsr2-uhh, may1-aug18

Another good illustration of this year's tradeoff between volume and extent. Development of the crack has allowed more MYI to drift into Beaufort. But it's not the classic "protective arm" of years past, only a withered stump.

4
Arctic sea ice / Re: The 2019 melting season
« on: August 14, 2019, 11:26:20 AM »
Ascat with NSIDC ice age overlaid at 20% transparent, mar21-aug12.
Thanks for your great animations, Uniquorn. Really interesting to see this one and it shows that some of the outlying ice has a multi-year component.
If anyone should study just one animation this season, let it be this one by uniquorn.
   ....

Yes, quite illuminating. Among many other things, it shows that the replenishment of Beaufort from the CAB, which looks good on area/extent maps, is bad for volume - and for the longevity of the main pack.

5
Arctic sea ice / Re: The 2019 melting season
« on: August 03, 2019, 02:37:58 PM »
I enjoy your analysis.  I don’t care where it gets posted, but I hope you continue to post it.  I don’t know why there has been push back.  Lots of people speculate on here and it is fun to look at the guesses and see how they turn out.

Posting location matters for future reference (as well as current streamlining). When we're trying to compare, say, 2023 to 2019, it will be useful to have the 2019 vs. 2012 analysis compiled mostly in one thread.

6
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: July 29, 2019, 11:23:39 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. 
    ....

This is quite significant. For volume, anomaly charts suggest the trend leans opposite. (I haven't scrutinized the data, which appear highly variable by year.) If so, the combination implies a shrinking but resistant end-of-season blob over time.

7
Arctic sea ice / Re: The 2019 melting season
« on: July 29, 2019, 11:05:45 AM »
Some kind of Transpolar movement is back upon us. ....

Net for the pack as a whole, that's the most rotation I've seen all season.

8
Arctic sea ice / Re: The 2019 melting season
« on: July 26, 2019, 11:06:02 AM »
Hot damn! HOT DAMN! Friv, where are you? We need your writer's talents, sir. Seems this one is quite a fitting occasion...

Friv emptied out his hyperbole bin with his latest post.

9
Arctic sea ice / Re: Latest PIOMAS update (July 2019)
« on: July 06, 2019, 03:38:59 PM »
Fram export  was higher than average in June.

Even more so relative to the dwindling amount of ice volume in the near CAB.

10
Arctic sea ice / Re: The 2019 melting season
« on: July 05, 2019, 03:02:58 PM »
Slater's model update:

Expected extent on Aug 24, 2019 : 4,32 M sq km (getting closer to 2012!).
   ....

Thanks for these regular updates, El Cid.

Since lately I've taken an interest in the daily Slater maps and couldn't find an archive of them, I started saving them. Here's a gif of the first 7: June 27 - July 4.
   ....

So, that's two large gaps in succession between the Slater and anomaly models. The red "observed" line will probably thread both, but I wonder whether the next week or two will be a tell on which model proves more accurate for late August.

11
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: June 26, 2019, 11:32:46 AM »
UH AMSR2 data is showing more high latitude sea ice extent and area in the arctic basin, than the highest melt years.


a reminder of this astute point that Oren made in the melting season thread:

CAB area at this time of year is a proxy for the area north of the Barents and the Fram, as the rest of the CAB is still mostly 100% sea ice until the beginning of July. As this year the transpolar drift is back with a vengeance, it is no surprise that CAB area is staying on the high side. As the Chukchi + Beaufort deteriorate, it is expected that the CAB will be hit first by loss of ice from its Pacific side.


12
Arctic sea ice / Re: The 2019 melting season
« on: June 26, 2019, 11:23:43 AM »

Accumulated albedo anomalies are actually almost above 2016 again:


The distribution of the anomaly is bad news, especially for ice volume.

13
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: June 23, 2019, 12:48:58 PM »
That's the plot but CT is long dead, I've yet to find a replacement for it.

I too have lost the plot.

different metric: There's a volume anomaly graph on Wipneus' site that's useful for seasonal comparison across years. Appears to be updated only through March, though.
       https://sites.google.com/site/arctischepinguin/home/piomas

14
Arctic sea ice / Re: The 2019 melting season
« on: June 23, 2019, 12:14:16 PM »
In addition to the plumes of moisture entering from Asia this week, next week may bring an even larger mass from the Pacific.

Forecast still a little wobbly, but if it occurs that would be the first major incursion of heat from the Bering bathtub I've seen in the last few months.

15
Arctic sea ice / Re: The 2019 melting season
« on: June 09, 2019, 10:14:54 PM »
The Albedo Warming Potential daily anomaly of Tealight's been taking a dive ...

That could help a lot at this time of year, yet the distribution is concerning. Much of the lower AWP anomaly area is getting blown farther toward (or into) the Barentsz.

16
Gonna show the thriller as seen on RAMMB even though there are spoilers in the thread..

I'm sitting and staring wide-eyed, mindlessly cramming popcorn into my mouth.

17
Lacking strong conviction (earlier vs. later arguments seem about equally balanced) yet voting anyway - late June -  because this is one of the most noteworthy features of the early melting season.

18
Arctic sea ice / Re: The 2019 melting season
« on: May 26, 2019, 03:52:32 PM »
Removed a couple of comments. If it's difficult to quit, I can help with that. Next step is moderation/ban.

Thank you for pollution remediation.

19
Arctic sea ice / Re: Albedo-Warming Potential
« on: May 18, 2019, 03:55:04 PM »
any analysis of the current impact of albedo forcing due to seasonal sea ice loss during the satellite period should be compared with regional ice loss impacts not arctic basin impacts,  this is due to the variable seasonal solar radiation which maxes at the summer solstice ....

At the Arctic circle (latitude of southern Chukchi), insolation reaches 90% of its peak value around this time of year. Open water, clear skies... not good.

We can expect some rotation of ice from Beaufort into Chukchi, which would confound the regional impact of albedo forcing on a time scale of a melting season.

20
Arctic sea ice / Re: The 2019 melting season
« on: May 14, 2019, 01:57:05 PM »

.... The latest CFS runs predict the high pressure and subsidence over the pole and Greenland will persist ....


That does look serious. Especially if the highs appear where forecast for June, with the Beaufort and Chukchi already in bad shape and absorbing lots of insolation.

21
Arctic sea ice / Re: The 2019 melting season
« on: April 20, 2019, 04:34:37 PM »
.... At this moment in time in 2019 there is in excess of 500,000 km2 of the Arctic that is open water compared with the 2010's average. That's about 12 days ahead of the 2010's average.
....

And the missing ice is disproportionately at lower latitudes: more exposed to insolation a month or two before the solstice. Big question is how much of the excess heat absorbed by open water in the Bering finds its way into the main Arctic basin.

22
Antarctica / Re: Sea Ice Extent around Antarctica
« on: September 16, 2018, 03:50:48 PM »
... a later increase back into already used parts of this graph paper (and thus a higher and later maximum than it seems to be now) is not too unlikely.
   ....

I thought so too. Though the decline (before the recent blip up) is more moderate than from some previous years during the same part of the cycle, it's still remarkable from such a low starting point in August.

23
Arctic sea ice / Re: Latest PIOMAS update (September)
« on: September 09, 2018, 01:37:53 PM »
My AMSR2 derived Volume model is more detailed ....

This model seems useful. Just curious: have you looked into correlations with Fram export?

24
Arctic sea ice / Re: The 2017/2018 freezing season
« on: March 05, 2018, 02:31:15 AM »
  ....
This suggests to me that we are going to start the season in a substantially worse state of preconditioning conducive to melt than last year. 
  ....

I lean toward Daniel B's view, though not necessarily on the same reasoning. Much of the ice-cover deficit is at high latitudes, so the water there will be losing an unusually large amount of heat even after the start of the melting season.

It appears that the vortex split will work to inhibit ice growth during the typically last few weeks of the freezing season.  We may still see a new low in maximum ice.  The corollary to this is that the Eurasian cold may work to stifle any early ice melt.  We will likely see a much flatter curve this year than in the past.

25
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: September 26, 2017, 12:18:17 PM »
Wipneus, thank you again for your wonderful animations (and relentless updates).

My thanks as well, this is a great thread

26
Arctic sea ice / Re: IJIS
« on: September 09, 2017, 03:04:44 PM »
I'll guess the minimum will be on the 16th, following steady compaction on the Atlantic front and a partial reversal of the refreeze in the CAA.

27
Arctic sea ice / Re: The 2017 melting season
« on: August 30, 2017, 02:43:07 PM »
Climate Reanalyzer shows something similar, with lots of rain and warmth on the Atlantic front.  But GFS has not been too reliable beyond forecast day 4-5.  Wait and see for another couple days.

28
Arctic sea ice / Re: The 2017 melting season
« on: August 22, 2017, 04:36:23 PM »
I've been wondering for a while what's up with the ESS bulge that survived thus far in the face of a very early opening of the ESS, and major advances on the Chukchi CAB front recently. My take is that it could soon disappear despite its longevity up to this point.
   ....

It does look vulnerable, though PIOMAS has only the outer fringe in the lowest-thickness band.

   ....
Not much wind lately or in the forecasts, perhaps enough to "pack up things" a little before coldness takes over ...

Concentration in the lobe may be low enough that light southerly winds won't cause much compaction.  Bottom melt is likely to predominate.  So this could be a good test of whether thin ice can hold out in the last month of the melting season, under what might be near-neutral conditions.

29
Arctic sea ice / Re: Latest PIOMAS update (August mid monthly update)
« on: August 21, 2017, 06:00:10 PM »
   ....
A fourth chart shows where 2017 is currently record low after previously lagging behind - the Greenland Sea. The halt in Fram export had some consequences after all.

Looks like you nailed it.  Early in melt season I thought the high Fram export would lead to accelerated ice loss in the nearby CAB.  But that didn't happen, maybe owing to snow cover from those late-winter storms.  Could be a form of negative feedback.

30
Arctic sea ice / Re: The 2017 melting season
« on: August 17, 2017, 07:43:43 PM »
This recent interesting paper, published online yesterday, may help further our understanding of the melting season a bit.

Good find, a few notes:
     "... divergent ice motion in the early melt season triggers large-scale feedback which subsequently amplifies summer sea ice anomalies. The magnitude of divergence controlling the feedback has doubled since 2000 due to a more mobile ice cover..."
     They're talking about normal gyre-and-drift-related motion, not owing to larger or more frequent storms. 
     This divergence doesn't make a big difference in early-season ice concentration, but it's amplified by ice-ocean albedo feedback:
     "...although the direct contribution of doubled divergent ice motion after 2000 to the ice concentration reduction is small, this trigger accelerates ice melt through the enhanced solar heat input over the open water fraction..."
      Is it too big an inferential leap to say that trend risks destabilizing the Arctic regime?
      "... heat input through the open water fraction is the primary driver of seasonal and interannual variations in Arctic sea ice retreat..."

Figure 2 from the paper:

31
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 14, 2017, 08:11:43 PM »
Correct me if I'm wrong but that looks like the ice pointing out towards Wrangel is being cut off...

That also occurred in 2012 and the cut off ice disappeared during the GAC but it occurred about 2 weeks earlier. We could very well have some lonely ice in the CAB near ESS as the melt season ends.

GAC-12 seemed almost surgically precise in how it lopped off a huge expanse of ice.  This year the equivalent weak spot appears to be slightly east of the midpoint between Wrangel and the pole.  GFS forecasts a low in that locale around day 3-4, but likely not deep or persistent enough to cause a complete separation.

32
Arctic sea ice / Re: The 2017 melting season
« on: August 14, 2017, 07:28:21 PM »
... We could even see an ice free Perry Channel within a week....

Watching closely yet reserving judgment.  I recall quite a prolonged warm spell across the CAA a few years back, which I thought would cause a dramatically early opening of the NWP.  In the event, it was only a little early (end July iirc).  It takes a lot of heat to melt all that ice.

33
I'm guessing September's graph will be more V-shaped than usual, and therefore the resulting rank for the month's average could be as low as 6th even if the daily min (other poll) is higher.  So going with 4.25 to 4.75.

34
Anchoring yourself to a previous decision is a bit of a cognitive trap, imho. The only way to improve our decisions and guesses is to review old judgements when we gain the light of new evidence.

Yeah, I feel those jaws on my brain: still seeking reasons that thickness distribution (rather than volume per se) will push extent down.  Came up with: storm-induced dispersion will first slow extent loss, then wave action and bottom melt will prolong it, resulting in a late low.
    That's not overwhelmingly convincing, so going with 3.75 to 4.25 for a podium finish.

35
Arctic sea ice / Re: The 2017 melting season
« on: August 10, 2017, 12:31:03 PM »
GFS 00z operational run is interesting as it depicts a intensive cyclone of equal strength to develop in the region between Frans Josefs land and Severnaya Zemlya in about 5 days....

Any corroboration from other forecast models?  If GFS is correct (low is still 5 days out according to Climate Reanalyzer), winds are likely to blow the higher-concentration ice away from FJL, exposing it to open-ocean wave action for the first time in months.

36
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 03, 2017, 01:40:59 PM »
Seems as though extent (ice edge) did rebound somewhat in the regions most affected by recent southerly winds, only to be overwhelmed by extent drops inside the "pack" (there is no pack, it's mush -- I mean not at the edge). What would happen if we get a real storm, I wonder...

Looks like the short-lived dipoles next several days will undo the localized rebound, after first putting another dent in the higher-concentration ice near Wrangel. 
As for a "real storm," yesterday's ECMWF forecast a brief one: down to 979 hPa on D4, as Neven pointed out.  Today's GFS forecasts another low a few days later moving in on a different track.  The latter has been somewhat unreliable: someone else noted that it is prone to err by merging lows together later in the forecast interval, if I understood correctly.

37
Arctic sea ice / Re: The 2017 melting season
« on: August 02, 2017, 02:18:21 PM »
.... The energy budget for the energy entering the Arctic, including that which comes from lower latitudes has, for a number of reasons, been distributed somewhat more evenly throughout the year....

Sounds like a good overarching explanation, but doesn't directly account for the (presumed) negative feedback of increased snow cover.  That would be a bigger drag during the melt season than reduced heat advection from lower latitudes.
                                                                                                                                       

p.s.

Ryan Maue posted this image recently on twitter.
I know people have mixed feelings about this guy but his visualizations are 2nd to none....

Sorry, can't let this pass.  No one's visualizations on this topic surpass A-Team's, in my estimation.

38
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: July 29, 2017, 01:48:36 PM »
So the Northern Sea Route is open, for any ships willing to dodge those remaining few floes.

Though I don't comment here often, it's a daily go-to page for me.  I greatly appreciate the updates and graphics.

39
Arctic sea ice / Re: The 2017 melting season
« on: July 29, 2017, 01:43:32 PM »
   ....
And both ECMWF and GFS predict, that it will continue with more storms for the next week.
GFS shows the storm over the East Siberian Sea with below 980 hPa, GFS sees it even below 975 hPa.
   ....

GFS shows the later storm intensifying, to bottom out on 5th August.  Any corroboration from other models?
Its track would cause considerable dispersion in an area where the thin ice is vulnerable.  A large separation event is possible, though not likely on the scale of 2012's.

40
Arctic sea ice / Re: Latest PIOMAS update (mid July update)
« on: July 25, 2017, 02:39:07 PM »
   ... It seems 2017 leads in the thicker categories (>1.46, >2.61) but lags in the thinner ones (>0.26, >0.71) which could lead to a higher area/volume ratio at the minimum, making a record area very unlikely based on this data, but a record volume potentially more achievable.
   ....
Not sure I follow your reasoning.  My take on the graph is that (relative to recent years) 2017 has proportionately less area in the thicker places.  If so, wouldn't we expect the area/volume ratio to drop faster than usual between now and the minimum?

41
Arctic sea ice / Re: The 2017 melting season
« on: July 23, 2017, 05:30:30 PM »
   ....
As for the effects on the Beaufort Gyre and Ice.
   ....

Much as I appreciate your thorough analysis and accompanying graphics, I'm having trouble piecing it all together.  Yes, the Arctic is in for considerable heat and moisture advection from the Pacific.  But won't this be mitigated by the lows protecting areas of the central ice pack?

   ....
That which is there will all be flinging itself out through the CAA and down both coasts of Greenland ...

I don't see much indication of this in the next week or so.

42
Arctic sea ice / Re: The 2017 melting season
« on: July 13, 2017, 02:41:51 PM »
   ....
My pixel-count-volume-loss-estimate from the 13th to the 21st: ~1.150km³, that is about 140km³ a day, pretty much the same loss-rate as between 1st and 12th. Forecast for the 15th has remained stable at around 7.350-7.400 km³ (all the big ifs still apply).
Interesting to see the projection of sustained volume melt, in view of Jim Pettit's interannual comparisons on ASIB and elsewhere.  If corroborated by PIOMAS, this would mean a volume anomaly at or near record lows into late July.

   ....
We'll see, all peripheral seas are for sure compromised, but I suspect the progress will slow down when reaching the CAB. ...
Sounds plausible, and underscores the ongoing tension between volume and area/extent measures this season.  Absent some GAC event, bottom melt during August and September will likely tilt the outcome one way or the other.

43
Arctic sea ice / Re: The 2017 melting season
« on: July 08, 2017, 04:47:33 PM »
subgeometer,
Quote
Large areas of the basin are going to see rain over the next 6 days, further conditioning it for destruction, and rendering the outlook from May meltponds irrelevant, in my opinion anyway
I am thinking likewise. The meltponds have made up for lost time.

I am leaning the other way.  iirc Schröder's model heavily weighs the albedo effect of melt ponding, which is why the May-June values have such a good predictive track record.
     I do think his prediction of 5.1 million Sept. mean ice extent is on the high side, but owing more to thickness distribution than the current (post-solstice) rain over ice.  Much of the Atlantic-side relatively thick ice will eventually melt, while the FYI and other thin ice toward the Pacific continues to weaken.

44
Arctic sea ice / Re: The 2017 melting season
« on: July 05, 2017, 01:56:34 PM »
Nice SST animation, sis!
   ....
Those warm spots sometimes fade after a few days, but this time it looks like they will persist for another week or longer.  Because of positioning of lows in the northern Pacific, moderate heat advection through Bering Strait will continue for several more days, then resume about a week out if the forecast verifies.

45
Arctic sea ice / Re: The 2017 melting season
« on: June 28, 2017, 03:49:13 PM »
   ....
Quote
Linear extrapolations of trends don't make much sense when this year's thickness vs area distribution is so different from the last 4 years.
Very important point. The already-meagre tools we have for following the melt season are not being processed by product algorithms adapted to the new conditions of the ice pack, weakening comparisons to the years for which they were developed and vetted.
   ....

Does that mean our intuitions are more valuable than usual?  Mine feel decidedly hazy.  Earlier in the season I guessed wrong on melt ponding, having failied to account for the powerful negative feedback of snow cover.  But thickness distribution has been poor all along, and still indicates a high likelihood of a record minimum.  A near-term lull in Fram export won't help distribution much as the Pacific side continues to weaken.

46
Arctic sea ice / Re: The 2017 melting season
« on: June 22, 2017, 03:53:29 PM »

Does imported warm air from Siberia and ocean mixing count for more than the significant reduction in insolation during the peak week for sunlight?

I don't think so, especially near the solstice.  But these are only two factors in a system of fascinating complexity.  Among the others: rain will strip away much of the remaining snow cover over areas of higher-than-normal albedo, and the position of the cyclone means winds will push some thicker ice closer to the Fram exit.

47
Arctic sea ice / Re: The 2017 melting season
« on: June 21, 2017, 03:35:40 PM »
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.
Absolutely, the biggest difference probably being surface air temperatures. 2013 was very anomalously cold. This year isn't a scorcher, but it's not exactly cool either.

Minor lows positioned near the Aleutians next week will send warm, moist air towards the Arctic cyclones, which might partly explain their longevity.  This is the first substantial advection of excess heat from the Bering that I've noticed since early in the season.

Storms in June do bring a cooler, cloudier central Arctic and help preserve sea ice but be careful with the 850mb temperatures. There's a very different atmospheric sounding under an upper level low than under an upper level high. There's subsidence, and often an inversion under the high.
   ....

I recall some earlier discussion on the Forum about "cold-core" vs. "warm-core" cyclones.  Not sure whether this pertains to FooW's point, but the one approaching ESS looks like the latter to my layman's eye.

On the whole, my impression is that that the near-term weather will be good for extent (owing mainly to dispersion and cooler central temperatures) but eventually bad for volume, for reasons others have noted.  If that's the case, we're still on thin ice this year.

48
A lot of posts in this thread are fairly equivocal, but I'm willing to go out on a limb- The volume gap will almost certainly shrink.
      ....

Normally I would side with the reasoning of anomaly reversion: a shrinking volume gap.  This time I will instead join the equivocating crowd.  The gap will widen during July, then narrow during August.
     First because of the distribution of volume.  At least according to PIOMAS, a disproportionate amount of volume is either already in the Atlantic melt zone or heading towards it.  And the wide swath of thinner ice toward the Siberian side of CAB looks vulnerable to any sustained dipole setup: either by melt ponding under sunny skies (admittedly doesn't look like an unusual amount so far) or heat advection from the open waters in Chukchi and elsewhere, which would be an indirect albedo effect.
    Second - the narrowing stage - because the GAC-2012 was apparently an outsize contributor to that year's record minimum volume.  Even though big cyclones fed by anomalous heat in the northern Pacific seem more likely than usual this year, there is no particular reason to expect an outlier like 2012's - which also took a track that did severe damage to the remaining ice.
    Which bucket to choose, then?  I'll go with "gap will shrink..." which still admits to the possibility of a new record low this year.  Another form of equivocation.

49
Arctic sea ice / Re: Latest PIOMAS update (June)
« on: June 03, 2017, 05:28:55 PM »
@ A-Team - I'm sure i won't be the last to chime in, it's wonderful to see you posting again, you were missed!

+1

   ....
Initially, Arctic amplification (resulting in late season open water with high absorbance) is a poor match with the timing of solar energy peak input, but the overlap will improve in coming years. However open water in Sep-Oct-Nov is already important to irrevocable de-stratification and heat transfer from ocean to atmosphere.
   ....

While the "blue water" advance toward higher-insolation season might be slow, there has already been a rapid - if inconsistent - increase in the amount of first-year ice susceptible to melt ponding.  Its effect is harder to gauge, of course, because of interaction with weather conditions.

50
Arctic sea ice / Re: Latest PIOMAS update (June)
« on: June 03, 2017, 04:07:07 PM »
The gridded thickness animation of May 2017. The situation in the Fram is crazy.

And note the 4m stretch to the north of Greenland. Near the end of the animation you can see it start to disappear as it prepares to be flushed down Nares.

Apart from these two critical locations, overall distribution of thickness became even worse during May.  Near-term there may be some respite in Fram and Nares export, but the weakening in the central pack is likely to ramify for the rest of the melt season.

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