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Messages - sark

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1
I have been more or less obsessed with feedbacks since I first understood their significance. These are a good start for this region. For now, I'll just also point out that more open water in the Arctic allows for bigger waves to form, which in turn can more easily churn up whatever ice (or slush) is left.

The larger amplitude waves may also lead to churning of that lower strata of warmer, saltier water up toward the surface. Both of these processes of course melt more ice, creating more open water, allowing for bigger and bigger waves...

We are probably mostly now past this stage, but I suspect that a few years ago, a 'flash melt' event we had was exacerbated by the fact that some old ice as it broke up formed icebergs, some of which went down to considerable depths. When high winds hit the top of these, their much deeper and bigger sub-sea bodies would sway back and forth, churning that deeper, warmer strata up toward the surface.

This is just my theory, and we now will see very little of this, except from icebergs calved from glaciers, since nearly all of the thick old ice is now gone.

2
    I just read about yet another feedback mechanism I was not previously aware of:
      ' Freshly melted ice ... creates a layer of cold water that protects sea ice above from more melting.   "It isolates the ice from the hot devil water sitting at the bottom waiting to come up" Wagner explains.  Less sea ice means there will be less of that protective cold layer, leading to even more melting. '
https://www.cnn.com/2019/06/08/world/arctic-beneath-ice-intl/index.html

     Which got me thinking it would be useful to have an inventory of all the significant reinforcing ("positive") and suppressive ("negative") feedbacks that affect Arctic sea ice.

    I did not find any forum title where this would fit, but this section seems to be the most closely related topic.  It could require its own thread, similar to the Glossary.

Here is the kind of list I have in mind:

Reinforcing feedbacks:
1. Melted ice creates cold layer that insulates remaining ice from warmer subsurface water.  Less ice to melt reduces this insulating layer.  Which leads to even less insulating cold layer water.

2. Less ice leaves darker ocean water with lower albedo, thus energy from solar radiation is absorbed into water instead of reflected.  Warmer water leads to less ice.

3.  Overall, fractured ice is more mobile and thus more susceptible to being exported via Fram Strait or Nares Strait.  There is chance of an ice bridge to block export via Nares Strait with fractured, reduced ice cover.  Increased export results in less multi-year thick ice, and more mobile young ice the next year.

4.  Fractured or thin sea ice floes have more surface area per unit volume and therefore melt at lower temperatures than thicker ice, or larger ice floes.  This leads to less surviving ice the summer to become thicker multi-year ice.

5.  Fractured vs. contiguous ice allows more wave action that interferes with freezing of ice and allows wave action to break ice into smaller pieces less resistant to melt.  Resulting in more fracturing of the remaining ice and even more wave action.

6.  Albedo reduction by replacing ice with dark water leads to warmer water and more energy in the Arctic Ocean system.  That in turn increases frequency, intensity, or both, of cyclones causing wave action that break up ice. Which reduces albedo even further.

7.  Weakening of the Polar Cell results in more frequent occurrence of Arctic Dipole, that increases export of ice out of the Arctic, which lowers Arctic sea ice, which leads to warm Arctic Ocean water, which leads to further weakening of the Polar Cell.  (whew, that's a long chain)

8.  Loss of ice cover weakens the polar cell which in turn allows more incursion of of warm moist air masses from the south into the Arctic, which leads to more weakening of the polar cell.

9.  Weakening of the polar cell allows more cyclonic systems to move into the Arctic.  Those cyclones disrupt the Arctic sea ice, and in doing so further weaken the polar cell.

10.  Younger, thinner ice has higher salt content and thus lower melt temperature.  Therefore it has less chance of surviving the summer melt to become more resistant, thicker multi-year ice.

11.  Reduced snow cover allows earlier spring warm up of Arctic land mass, which results in warmer air flowing onto the Arctic Ocean. This warms the system as a whole, leading to reduced snow cover and earlier snow loss the following year. 

12.  More open ocean leads to higher humidity and more extensive or thicker cloud cover over the Arctic Ocean in the fall and winter.  More extensive or thicker cloud cover in fall and winter reduces heat loss thus reduces winter refreezing.

13.  Earlier spring warm up of Arctic land mass, results in increased permafrost and land ice thaw, resulting in earlier and more melt water flowing from land into the Arctic Ocean. The meltwater warms the Arctic Ocean and reduces Arctic sea ice.  Which leads to more open water with lower albedo to absorb solar radiation in the summer, increasing summer heat content of the system  More open water allows this heat to escape to moderate winter air temperatures and earlier spring warm up.

14.  Reduction of Arctic sea ice allows increased flow of warmer Pacific or Atlantic water into the Arctic, leading to further decline of Arctic sea ice, leading to more Pacification and Atlantification of the Arctic Ocean.

***
Compensatory or Suppressive feedbacks:
1.  Ice cover insulates the Arctic Ocean in winter.  With less sea ice cover there is faster energy loss and winter cooling, and thus faster winter ice increase after a lower September minimum extent.

2.  Thin ice grows much faster than thick ice.  Thus faster winter ice increase compensates for thinner ice after a strong melt season. 

3.  More open ocean leads to higher humidity and more extensive or thicker cloud cover over the Arctic Ocean in the summer.  More extensive or thicker cloud cover in summer reflects more solar radiation and thus reduces summer ice melt.

*****************************

     My wording is no doubt less than perfect for many of these.  Some may be just plain wrong.  Some I just made up!  Maybe I should just find a good book or review article with such a list.  Any suggestions?

   If you think a proposed feedback is incorrect or wrongly stated, it would helpful to have that noted.  But I'm not looking to start multiple debates about which feedbacks are most important. 

      I don't get a commission for each new proposed feedback, so there's no need to get heated.  The planet is hot enough as it is.  These are just suggested entries.  There must be suppressive feedbacks missing from the list.

   I just thought a list would be interesting because I keep finding out about feedbacks I had not previously been aware of. 





3
'983mb' .. does my LAC become a GAC ? or is our new GFS as wild on deepening lows as the old was at overheating the Arctic ? .
  I do wish TTb's maps ( and Windys ) came with fewer isobars .. Highs look like lows and lows look like hurricanes to those who grew up with 4 isobar spacings .. b.c.

4
Arctic sea ice / Re: The 2019 melting season
« on: June 07, 2019, 08:00:03 AM »
June 2-6.

Sea ice area in the Beaufort. There is huge albedo warming potential and clear sky now.

5
Arctic sea ice / Re: The 2019 melting season
« on: June 07, 2019, 01:35:14 AM »
  Darvince's post reminds me of one I made earlier ..

  Sequence ?  .. 2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...  b.c.

6
Arctic sea ice / Re: The 2019 melting season
« on: June 04, 2019, 07:59:07 AM »
I know there is a lot of excitement on this board that this could be the year everyone's been waiting for: the "Armageddon" mentioned by Gerontocrat in the sea ice extent/area thread. It will be like the "second coming" if and when it happens.

You're not paying attention. The 'Armageddon' has already started, regardless of whether this melting season breaks any records or not. And it makes perfect sense for people who are worried about AGW, who take its potential consequences seriously (unlike you), to 'hope' for even more spectacular images of Arctic sea ice loss, so that maybe enough people wake up to start doing something about it, even though we should have started 30 years ago.

7
Someone just posted this on Twitter. Frost and freeze warning around the Great Lakes tonight. I'm not sure if this is the right place for it.

8
Policy and solutions / Re: Removing CO2
« on: June 02, 2019, 07:53:05 AM »
Mankind isn't even able to put less CO2 into the atmosphere, but there are still people who think we could manage to pull CO2 out of the air.

This kind of stupid hybris hurts my brain! Every time i hear the word geo-engineering my head starts to spin.

It's just not logical to pull it out of the air when around the corner a coal plant is putting it there. Why not turn off the god damn plant?? This is running in circles. We have technologies to produce power without emitting CO2 for literally hundreds of years! These days they are even cheaper than the fucking coal in the first place. And they are easier to build and deploy even.

On the other hand, if you build machinery to pull CO2 out of the air, YOU FUCKING PRODUCE CO2 to build this machinery! Why not use these resources to build machinery that gives us CO2 free power??

You can view it from every angle, but it just makes no fucking sense.

/rant


9
Arctic sea ice / Re: The 2019 melting season
« on: May 27, 2019, 05:14:13 AM »
What is most striking to me in looking at these images is not the comparison between 5/26/2019 and 5/26/2012. It is between 5/26/2019 and the final condition of the ice at the end of the 2012 melt season. Since the end of the 2012 melt season, the thickest ice has continued to disappear. We are only one severe melt season away from a BOE.

10
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: May 27, 2019, 02:29:25 AM »
My guess is it disintegrates.

11
I made my guesses at beyond June 10th below
Brilliant work in both posts, Sark!

Thank you for condensing, presenting in imagery and describing what I've been wondering about.

I tend to agree - the GFS has been improving on predicting general regional conditions further out, if not the exact details to their distribution and intensity.

I think we've all been seeing the general pattern of HLHL around the pole, if not fully comprehending it. Though at times I've thought I've seen it divided out even further - HLHLHL or even HLHLHLHL; the overall takeaway is, the Polar cell has been blown to tatters, and circulation is becoming nearly as chaotic as water on the boil.

12
Developers Corner / Re: Test space
« on: May 25, 2019, 06:09:18 PM »
Here I am testing another double-masking of Ascat, this time with U Bremen SMOS-SMAP new thinness product instead of UHH AMSR2 low sea ice concentration and open water. This product is provided at a very generous scale of 1173 x 2170 png, a big improvement in resolution (if it is real and not just a rescale). It comes with a satisfactory land mask too.

https://seaice.uni-bremen.de/data/smos_smap/png/north/2019/ png archive back to 31 Mar 2015

Because thinness and concentration are fairly similar in location in that edges of the ice pack have thinner ice as well as lower ice concentrations, it isn't feasible to triple-masking because of the extensive overlap in areas affected.

This combination of two satellites seemed to have extended the season well past the previous SMOS-by-itself terminal date of May 1st. However farther along in the season as melt ponds and liquid clouds become important, both the SMOS-SMAP thinness and Ascat products will likely deteriorate (or the former not even be archived).

The mp4 shows 53 days from April 1st to May 23 of 2019. A larger view is needed because ice thinness in peripheral seas such as Bering, Barents and Kara is more important than in the central Arctic Ocean this time of year. Both SMOS-SMAP and Ascat have a few missing days or partial images which I replaced by adjacent complete ones; this happens as well with UHH AMSR2 but less frequently.

The May 23rd looks like it has a blob of weather in the northern western Beaufort interfering with proper thinness determination. Ice thinness doesn't change as rapidly as weather or melt or and persists from frame to frame. These artifacts could be edited out manually or by AI per the criteria stated.

On scaling, SMOS-SMAP needs an enlargement of 104.414 to fit the smaller AMSR2uhh whereas Ascat needs 228.084 so to match SMOS-SMAP to Ascat requires 228.084/104.414 = 218.442 magnification of Ascat. I measure from the Aleutians to southern Sweden to get the largest pixel lengths to compare as this reduces percent error in the scaling ratio.

The AMSR2 masking shown a couple of posts back covered 30 different days so I am not reposting it here. "30 days of Ascat land and water masked to 24 May 2019.mp4"

Quote
Combined SMAP–SMOS thin sea ice thickness retrieval
C. Patilea et al U Bremen AWI 28 Feb 2019
https://www.the-cryosphere.net/13/675/2019/ free full text

Consistent Combination of Brightness Temperatures from SMOS and SMAP over Polar Oceans for Sea Ice Applications
AU Schmitt, L Kaleschke April 2018
https://www.mdpi.com/2072-4292/10/4/553/htm free full text

https://seaice.uni-bremen.de/data/smos_smap/png/north/2019/ where to get the pngs

The passive microwave sensors Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) provide brightness temperature data at 1.4 GHz. At this low frequency the atmosphere is nearly transparent and in polar regions the thickness of thin sea ice can be determined up to 0.5m for an extended period into the spring.

The thickness of ice partly determines the resistance against the deforming forces of wind and ocean currents. Even a thin layer of sea ice inhibits evaporation, reduces heat and gas exchange between ocean and atmosphere and increases the albedo. Sea ice — even if thin — also provides a solid surface for snow to deposit on, which further reduces heat exchange and increases albedo.

SMOS has been developed for retrieving soil moisture by inferring the surface emissivity which is correlated with the moisture content and sea surface salinity and link measured brightness temperatures with sea salinity through the dielectric constant of the water in the first few centimeters [[to which upwardly extruded brine or melt ponds might contribute]].

Quote
Effects of decimetre-scale surface roughness on L-band Brightness Temperature of Sea Ice
M Miernecki, L Kaleschke et al  03 Jun 2019
https://www.the-cryosphere-discuss.net/tc-2019-110/tc-2019-110.pdf free full text

Sea ice thickness measurements with L-band radiometry is a technique which allows daily, weather-independent monitoring of the polar sea ice cover. The sea-ice thickness retrieval algorithms relay on the sensitivity of the L-band brightness temperature to sea-ice thickness. In this work, we investigate the decimeter-scale surface roughness as a factor influencing the L-band emissions from sea ice.

Most affected by surface roughness is the vertical polarization around Brewster's angle, where the decrease in brightness temperature can reach 8 K. The vertical polarization for the same configuration exhibits a 4 K increase. The near-nadir angles are little affected, up to 2.6 K decrease for the most deformed ice. Overall the effects of large-scale surface roughness can be expressed as a superposition of two factors: the change in intensity and the polarization mixing. The first factor depends on surface permittivity, second shows little dependence on it.

13
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: May 20, 2019, 06:15:12 AM »
Thank you for your comments. And thanks wdmn for taking care of the posts.  :)
I should make a post on "places less livable".  :'(

[ADS NIPR VISHOP (JAXA)] Arctic Sea Ice Extent.

May 19th, 2019:
     11,323,094 km2, a drop of -51,767 km2.
     2019 is 2nd lowest on record.
     (2012 highlighted).


14
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: May 19, 2019, 05:47:08 AM »
May 18th, 2019:
     11,374,861 km2, a drop of -46,238 km2.
     2019 is 2nd lowest on record.

15
Long-term weather starts to get into tele-connections ...

Hot Arctic and a Chill in the Northeast: What’s Behind the Gloomy Spring Weather?
https://blog.ucsusa.org/brenda-ekwurzel/hot-arctic-and-a-chill-in-the-northeast-whats-behind-the-gloomy-spring-weather

... It may seem counter-intuitive, but the story of the strange weather unfolding this spring in the US is related in part to snow last October in Eurasia. This indicator—the Eurasian October snow cover extent indicator—is proving to be worthy of additional attention by US weather geeks. The good news is that the scientists who were paying attention to the Eurasia snow extent behavior during October, along with a host of other indicators, gave advanced warning of the emerging US winter and spring weather pattern for 2018/2019. 

... I encourage those who want to know, to spend some time clicking on the links here or links in earlier blogs that point to even more information (see here, here, here, and here). These describe the details regarding how Arctic sea ice decline, particularly in the Barents-Kara sea ice, north of Scandinavia and Russia, contributes to ocean and atmosphere behavior. Which contributes to Eurasian snow cover extent behavior. And ultimately a wavy jet stream with episodic cold outbreaks over winter and spring in the Northern Hemisphere, including the US.

... Here is an example of the science as Judah Cohen explains, “There is a growing consensus that it is Barents-Kara sea ice in the late fall and early winter that has the greatest impact across Eurasia.  Therefore, low Barents-Kara sea ice in November for example, favors a strengthened Siberian high, increased poleward heat flux, a weak stratospheric Polar Vortex and finally a negative Arctic Oscillation. An important point regarding the Siberian high is that it strengthens or expands northwest of the climatological center.  For low snow cover and/or high sea ice the opposite occurs.”  Translation, a weakened polar vortex means more cold outbreaks deep into US territory like this past winter and spring. ...

North Atlantic Warming Hole Impacts Jet Stream
https://phys.org/news/2019-04-north-atlantic-hole-impacts-jet.html

The North Atlantic warming hole (NAWH), a region of reduced warming located in the North Atlantic Ocean, significantly affects the North Atlantic jet stream in climate simulations of the future, according to a team of researchers.

... To investigate how the development of the NAWH impacts the jet stream, the team conducted a series of large-ensemble, atmospheric model experiments in the CESM with prescribed SST and sea ice levels over three different time periods.

Their results indicate that the NAWH plays an important role in midlatitude atmospheric circulation changes in the model's future climate simulations.

"We found that it's really quite important for that region," said Gervais. "The NAWH seems to be elongating the jet even further and shifting it a little bit north. Instead of just thinking about how the tropics and arctic amplification are influencing the jet, we now also need to think about how this warming hole is going to influence the jet. These local changes in the North Atlantic jet are of a similar magnitude to the full climate-change response in the region, indicating that the North Atlantic warming hole could be an important additional factor in the tug of war on midlatitude circulation, that has received little attention."

Melissa Gervais et al, Impacts of the North Atlantic Warming Hole in Future Climate Projections: Mean Atmospheric Circulation and the North Atlantic jet, Journal of Climate (2019)
https://journals.ametsoc.org/doi/10.1175/JCLI-D-18-0647.1

16
I wrote about what's happening over at a fading political blog the other day. Intense end warmings in the stratosphere have consequences. The sudden warming of the region from 60N to the pole from the surface to the top of the stratosphere is what I was referring to by the description "atmospheric convulsion." There's likely to be a horrific tornado outbreak on Monday and Tuesday as the storm that's now giving California a very late soaking reforms on the east side of the rocky mountains.

Zach Labe understands the physics of this situation better than I do - he's studying it for an advanced degree. I doubt he's reading this but I wouldn't mind being corrected if I made a mistake.

https://www.dailykos.com/stories/2019/5/15/1857911/-Atmospheric-Convulsion-Will-Cause-Historic-Disasters-of-Arctic-Melt-U-S-Storms-Next-Week

17
Arctic sea ice / Re: The 2019 melting season
« on: May 10, 2019, 03:45:50 PM »
Why do I keep getting the impression that the entire basin of ice is rotating clockwise?

High pressure.  it's all anticyclonic from space to surface.

https://earth.nullschool.net/#current/wind/isobaric/10hPa/orthographic=-84.79,85.32,419
Add that North Atlantic Drift isn't what it used to be so little to no opposite forces.

18
Arctic sea ice / Re: The 2019 melting season
« on: May 05, 2019, 12:10:48 AM »
What apparently is happening is that greenhouse gases are speeding up the Brewer Dobson circulation - the flow of air from the troposphere to the stratosphere and back. In this case is is causing subsidence over Greenland, the Beaufort sea and the high Arctic. This is why, barring the lucky occurrence of cool cloudy stormy July, I think we are likely to see a new record sea ice minimum this September.

https://acomstaff.acom.ucar.edu/randel/Garcia_Randel_JAS.pdf

As Cohen wrote in his blog post, this subsidence tends to persist. A very warm sunny May maximizes the input of solar heat early, potentially allowing for a high amount of feedback due to reduced albedo in response to low early snow and sea ice extents.

These stratospheric processes may have a large impact on September sea ice extent, area and volume. Depending on the index, Greenland has had the 2nd earliest or earliest early melting and the western side of Greenland had little snow in the winter so it will rapidly darken when the west side has surface melting.

The stratospheric events of the past 6 months have been a real shocker. I think the high pressure over Greenland and the western Arctic will likely continue into June.

Below is an earth.nullschool.net image of the lower stratospheric temperature and circulation at 17Z 4May19. It shows warm air sinking over the pole. That subsidence continues into the troposphere.

19
Arctic sea ice / Re: The 2019 melting season
« on: May 01, 2019, 11:10:52 AM »
This image is based on yesterday's Modis image with bands 7-2-1 overlayed with the daytime ice surface temperature using a compressed palette. Yellow has been calibrated to around 273 K (with orange-red being warmer), so the idea is to an alternative indication of where surface melt is likely:


.. does deep purple mean smoke on the water ? :) .. b.c.

 seriously though .. this is a useful image .. and gerontocat may appreciate another way of seeing Greenland burn ..

20
Arctic sea ice / Re: The 2019 melting season
« on: April 25, 2019, 08:33:41 PM »
JAXA RGB, jan1-apr24.

21
Chicago has a chance of seeing its largest post 4/25 snowstorm on record. I think the city will only see a little bit but the suburbs are now shown receiving up to 10" by the 00z modeling suite and the trend has been colder. That this is preceding the Arctic heat wave is no coincidence IMO, as the Arctic is spilling its guts into the mid-latitudes.


22
Arctic sea ice / Re: The 2019 melting season
« on: April 25, 2019, 02:21:24 AM »
Slightly off topic but yet another sign of arctic warming - the break up of ice on the Yukon yesterday was the second earliest ever recorded and only 8 hours behind  the earliest breakup on the same date in 2016
Technically this was indeed the second earliest break up, but while the indicator ( a post is placed out on the river ice connected to a clock, when the ice moves, the post pulls a pin from the clock, which stops and records the official time of break up) showed break up, in actual fact almost all the ice is still intact. Photos of the river condition are regularly posted on the site yukonriverbreakup.com. This morning's pic shows the open water at the top left, where the "tripod" was. We should have another pic in an hour or so!
Of course April 23rd this year was the 113th day of the year, while April 23rd 2016 was the 114th day of the year. But who is counting, its still early.

23
Arctic sea ice / Re: The 2019 melting season
« on: April 24, 2019, 10:11:07 PM »
once again a -nao modeled days 6-10 is turning into pacific centered blocking. this has been happening since 2013. click to animate

24
Arctic sea ice / Re: The 2019 melting season
« on: April 24, 2019, 05:23:45 PM »
o boy


The anomaly is very strong.  however, it is also paired with a huuuuuuge inflow of atmospheric water vapor which will suppress solar heating and will also produce large snow on CAB.
That's the question, isn't it? We have been dealing with these dueling feedbacks since 2012 it seems. However, I suspect that it will not produce large snows, but rather, rain, at least over Beaufort / Chukchi / ESS (IMO, could easily be wrong).

FWIW I started documenting these kinds of blocking pattern/Arctic heat and WVx inflows through the Bearing Strait in March of 2014.  See thread here:  https://forum.arctic-sea-ice.net/index.php/topic,784.msg22395.html#msg22395

25
Arctic sea ice / Re: The 2019 melting season
« on: April 22, 2019, 11:06:49 AM »
Two more charts about the reliability of forecasts if you don't mind:

1.500hpa geopotential is quite reliable for 6-7 days:

"The plot shows for each month the range at which the month mean (blue line) or 12-month mean centred on that month (red line) of forecast anomaly correlation dropped below 80%. The score for the northern hemisphere extra-tropics is a primary headline score of the ECMWF HRES.

Anomaly correlation scores are spatial correlation between the forecast anomaly and the verifying analysis anomaly; anomalies are computed with respect to ERA-Interim-based climate. Verification follows updated WMO/CBS guidelines as specified in the Manual on the GDPFS, Volume 1, Part II, Attachment II.7, Table F, (2010 Edition - Updated in 2012)."

2. 850 hpa temps are somewhat reliable until day8/9:

"The plot shows for each month the range at which the 3-month mean (blue line) or 12-month mean (red line) centred on that month of the continuous ranked probability skill score of the 850hPa temperature ENS dropped below 25%. This is a primary headline score for the ECMWF ENS.

The continuous ranked probability score (CRPS) compares the probability distribution of the quantity forecasted by ENS to its analysed value. Both forecast and analysis are expressed by cumulative distribution functions. The CRPS skill score then compares CRPS of the verified forecast to a reference unskilled forecast. As a reference forecast the re-analysis-based climatology is used."


26
Arctic sea ice / Re: The 2019 melting season
« on: April 22, 2019, 10:49:29 AM »
This is from the ECMWF site:

https://confluence.ecmwf.int//display/FUG/4.1+Forecast+Error+Growth

"Small baroclinic systems or fronts are currently well forecast to around Day2, cyclonic systems to around Day4 and the long planetary waves defining weather regimes to around Day8.  As models improve over time these limits are expected to advance further ahead of the data time.  Features that are coupled to the orography (e.g. lee-troughs), or to the underlying surface (e.g. heat lows), are rather less consistently well forecast."

In this sense brr is right: although the details will change, but major weather-systems - according to ecmwf - are USUALLY forecastable for 8 days.

To check the standard deviation between the ensemble members, ie. to see how reliable the forecast is, ECMWF shows this as well with colours:

https://www.ecmwf.int/en/forecasts/charts/catalogue/plot_ensm_essential?facets=Range,Medium%20(15%20days)&time=2019042112,120,2019042612&parameter=MSLP&area=Northern%20Hemisphere


27
Policy and solutions / Re: What type of transportation do you use?
« on: April 14, 2019, 05:47:11 AM »
I use a bike almost all the time, although my wife has a car to get to and from work (10km each way) and I am trying to talk her into an electric bike.
Sometimes I catch the train for longer trips or if the weather is not conductive to ride far, but even then, it is 2km each to the train station.

I use a tandem with a kid trolley on the back since I have two home school kids who need to get to events and tutors.

28
META:

please could someone correct the misspelling in the title ?

sidd

29
Arctic sea ice / Re: The 2019 melting season
« on: March 07, 2019, 09:21:27 AM »
High resolution AMSR2 area and extent both declined today.

Long distance swells are already reaching the Bering Sea, with much more to come.

30
Arctic sea ice / Re: Latest PIOMAS update (October)
« on: October 06, 2018, 06:12:05 PM »
So extrapolating data up to 2010, it was 5 years ahead and extrapolating data up to 2018, it was 6 years ahead

Indeed, the exponential extrapolation for the September PIOMAS minimum has been basically stuck at "ice free in (approximately) 5 years".  Gompertz follows a similar path but is a bit further in the future.  And the end date for the linear extrapolation decreased in the 2000s but didn't change much in the 2010s.



31
Arctic sea ice / Re: The 2018/2019 freezing season
« on: September 26, 2018, 04:03:42 PM »
Given the unprecedented event taking shape I cant believe this forum is dead.

We might see extent losses im early October.

I cant find anything like this in the archives.

I mean not even close.


32
Arctic sea ice / Re: The 2018 melting season
« on: September 21, 2018, 11:33:12 AM »
JAXA has dipped below the previous preliminary minimum again, so this baby stays open.  ;D

33
Arctic sea ice / Re: The 2018-2019 freezing season
« on: September 19, 2018, 03:34:20 PM »
In the freezer it goes, and I'll pull it out again once JAXA goes 25K above the preliminary minimum reached yesterday. Traditions are there to be respected.  ;)

34
Consequences / Re: Global Surface Air Temperatures
« on: September 13, 2018, 09:46:09 PM »
In other words, they're basically polar opposites!  ;D

35
Arctic sea ice / Re: The 2018 melting season
« on: September 09, 2018, 09:03:46 PM »
Looking at the same area back on Worldview, just over 10 years ago the ice had lifted away from both the north tip of Greenland and Ellesmere.


36
Arctic sea ice / Re: Holy Sh!t: Year-Round Arctic BOE Imminent
« on: September 05, 2018, 02:51:47 PM »
I just don't know how to expect the arctic to refreeze after a few BOE in late summer.  How do you propose the cold upper halocline layer of the Arctic will be maintained, after weeks and months of no ice cover?

Salty sea water freezes when the temperatures drop low enough. The Hudson is ice free every summer and freezes every winter with temperatures far higher than what we see in the central Arctic.

37
Arctic sea ice / Re: Holy Sh!t: Year-Round Arctic BOE Imminent
« on: September 05, 2018, 02:10:54 AM »
which is why there is not much more to say hence the rest is chatter and noise about something nobody can predict except the fact that year-round is not imminent.

Yes, well, that's pretty much it.  Despite the thread title, a year-round BOE is not imminent, so we fall back on speculating about when the Arctic might become ice-free in the summer.  And you're right that this has already been the topic of many threads, sometimes multiple ones simultaneously.

Will you qualify "imminent?"  what about 2035?

Whether 2035 is "imminent" is a matter of opinion, obviously.  But that's more of a realistic date for an ice-free September, not an ice-free year, surely.

Models suggest that when the ice extent becomes low enough there's a fairly rapid shift to a seasonally ice free Arctic (meaning a large chunk of the summer, not just a few days). But that doesn't then tip into a perennially ice free Arctic.  Bringing that about is a lot harder.  I would say "not this century" and therefore "not imminent" but YMMV.

https://www.sciencedirect.com/science/article/pii/S0277379113004162

38
Arctic sea ice / Re: Holy Sh!t: Year-Round Arctic BOE Imminent
« on: September 05, 2018, 01:50:10 AM »
It's a good question how long to go before you can establish a trend, in this case. In most cases for climate you need decades. This certainly does not meet that standard.
*Exactly*,  and thank uou.

Decades is about establishing a reliable number for a trend i.e. a number. Steepening or flattening is a binary choice. That is a different ball game. 2^11 = 2048. No, I agree that doesn't really work, I believe there is much more than a 1 in 2048 chance of the trend now steepening. However, maybe that is about the future which is hard whereas this is about observations to date.

If there were only 6 years after inflection point, I would believe that the process of fitting the curve was essentially data mining the residuals for an overfit of the data. So it appears to me to be more like 2^(11-6)=32 and 31/32 is more than a 95% confidence level but only a little more.

Perhaps better than guessing that number 6 used above, instead model a linear downward trend with noise to match the data 200 times. What would the 10 5 percentile model that is best at showing a slowdown in the rate look like? Would it be more or less convincing than my graph?

Waiting 20 or 30 years data before declaring whether the trend is flattening appears to me to be misuse of the valid reason for wanting that much data to get a reliable trend rate number.

(Edit: I meant 5 percentile or 10th most flattening data set)

39
Arctic sea ice / Re: The 2018 melting season
« on: September 04, 2018, 11:33:26 PM »
Not sure if this is the correct thread; forgive me if it is not!

What happened to the predictions of a GAC from the last week of so?

There is still a pretty decent cyclone going on around Laptev/Barents.  Not far off the intensity forecast a while back.  Pretty large system getting up towards the GAC 2012 size, but a fair gap in intensity.

The forecast Friv and I commented about just a day or so ago of a huge heat influx has moderated.  The forecast had a perfect alignment of strong high and low plunging a strong warm front in between directly into the Arctic.  The alignment has shifted a bit and the warm front now strikes a fairly glancing blow.  Until the next model run....

40
Arctic sea ice / Re: Holy Sh!t: Year-Round Arctic BOE Imminent
« on: September 04, 2018, 03:40:27 PM »
And of course the deeper and more important questions are: if there is a 'flattening,' what is causing it? 

One possible answer, from my comment a few minutes earlier:
Quote
perhaps from the loss of multi-year ice and the switch to a first-year-ice-dominated Arctic.  It's certainly possible that this represents a brake on the rate of volume loss that will help reconcile the seemingly different blue-ocean dates that are projected using volume vs extent.

In other words, the rapid downward trend prior to 2005 was due to the loss of multi-year ice.  First/second year ice, which now dominates the Arctic, keeps re-forming itself every winter, so the rate of decline has slowed.

Quote
and what are likely to be the main forces driving extent and volume numbers over the next decade?

Continued warming, internal variability, and feedbacks both positive and negative.  That covers everything, right?   ;D

41
Arctic sea ice / Re: The 2018 melting season
« on: September 01, 2018, 09:56:28 PM »
From the very first post in this thread, way back in March:

Personally, I think we will end up somewhere around 4,5 Mn km2 by the middle of September.

FWIW, it's now September and the current projected JAXA minimum (rounded to one decimal place) is in fact 4.5 million km2.  Not bad!

42
Arctic sea ice / Re: The 2018 melting season
« on: September 01, 2018, 01:19:12 AM »
It's that time of year again, when we see that extent hasn't dropped as low as we feel it ought to have, and so we try to change the definition...

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.

[... snip ... Discussion of posts where Ned W compares the standard extent data to what it would look like with a 30% threshold instead of 15% ...]

further, while it is great that you calculated that, perhaps you'd post the math behind it for verification and then nobody ever said that it must be 30%, perhaps the critical percentage is not 30% but another threshold. to follow this up it would take a few runs with different threshold to compare and the numbers to verify, after all, where are 30% numbers available, i did not find them which is why i was not able to do my own calculations?

[...] if we have a huge area  of 50% ice and 50% water no-one can tell that the result do not differ by at least the 35% that are usually counted and now are not, after al 35% is about a third, hence cannot be insignificant to my understanding

Personally, I think basic logic dictates that if an area is more water than ice, then it should be considered water. 15% as an arbitrary threshold is bizarre. If you look at my map prediction for Sep 1, a 50% threshold will be almost exactly as I predicted.

This comes up every year.  15% is what the community uses, all of the data (except older DMI) are based on it.  If we start making predictions about a 30 or 40 or 50% threshold, all it does is ensure that it will be prohibitively difficult to compare them to anything else, quantitively.

If this year's "50%-extent" is X million km2 ... Is that low, high, or average?  Nobody will know!  Because for every previous year, we have "15%-extent" data.

However ... As noted above, I did go back and reprocess all the NSIDC concentration maps to calculate a "30%-extent", and posted the results in the other thread here:

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

On the next page following that one there's a post by me with a csv file with the results.

Magnamentis wants that redone for other thresholds, and wants me to post "the math" for verification purposes.  The "math" involved is merely (a) reprojecting all the ice concentration maps into an equal-area projection, and then (b) counting up the number of grid cells that exceed whatever threshold you want.  (A further complication is the "pole hole" whose size changes...) If there's a lot of interest I'd be willing to rerun the processor for different thresholds.

The thing is, though, so far at least it doesn't have any non-trivial effect on the long-term trend in extent.  As Neven predicted...   So the payoff for doing it is pretty small.


43
Arctic sea ice / Re: The 2018 melting season
« on: August 31, 2018, 06:58:19 PM »
Looking at the extent trend for the last 6 days, 2018 is looking at 7th or 8th place.

6th, 7th or 8th place to me.
Odds of various ranks, per the predict-o-matic:

6th place: 61%
8th place: 23%
7th place: 12%
9th place: 2%
4th place: 1%
Everything else: negligible

Predicted minimum, 4.444 million km2 (yep, that's a lot of 4's)

44
Arctic sea ice / Re: The 2018 melting season
« on: August 28, 2018, 02:38:00 AM »
!gerontocrat is not allowing for the freezing thread to open!

What a cuck! Trying to fry humanity so he can make an extra buck. The worst of the worst. It is obvious that if gerontocrat was not a Big Oil Shill he would have opened the freezing thread.

Edit: how do you sleep lying on those piles on cash, while the world burns?

Unfortunately for me - control over the freezing thread is a power denied to me. I have to get my kicks in other ways, grinding the faces of the poor into the dirt, dinner with the Koch Bros, a burger and a beautiful chocolate cake at Mar-el-Largo while Trumpy lets me push the button to launch some cruise missiles at some innocents somewhere.

All that oil money gets to be a problem. Having to bribe both Republicans and Democrats gets to be a bit expensive - I mean Judas only cost 30 pieces of silver. Those were the good old days.

The trials and tribulations of the 1 percent - you don't know how lucky you poor people are.

45
Arctic sea ice / Re: The 2018 melting season
« on: August 17, 2018, 09:26:57 PM »
The early southerly dislocation of the cryosphere is going to prove increasingly impactful if the recent models are to be believed.

D4:



D7:



D10:



If this keeps up, Hudson Bay could begin refreezing before much of the High Arctic. Combined with the freshwater discharge from Beaufort, we could be looking at an even worse refreezing season for the Pacific and ATL fronts, as the early establishment of the cryosphere over NRN Canada is going to scoop enormous amounts of heat north into the ATL. The lack of freshwater / active typhoon season will do the same to the NPAC.

I am attaching the below not as a segue into continental snow, but as an illustration of what the 12z EURO is now showing across northern Canada. Snows are beginning to fall in a prolific way across higher elevations of the northern mid-latitudes, and just about everywhere further north.

While weak ice may be moving through the CAA, I do not think much melt will occur -- the CAA and the southern CAB should be the first regions to begin refreeze this year, and it may begin happening as soon as next week.

46
Arctic sea ice / Re: 2018 sea ice area and extent data
« on: August 16, 2018, 07:33:07 AM »
JAXA ARCTIC EXTENT 5,333,478 km2(August 15, 2018)

Back again and now within the last month of the melting season (on average).

Just to add to Juan's post...

- Extent losses above and below average in the last 4 days,
- Extent is now 69 k km2  (1.3 %) below the 2010's average extent on this date,
- and 130 k (2.4%) above 2017 (which is about to start a series of below average extent losses) ,
- Extent loss to date is now 305 km2 (3.4 %) below the 2008-2017 average, with 89 % of the average melting season done.

Resulting minimum from average remaining melt is  4.23 million km2, (excluding 2012 from the average gives 4.26 million km2 - an insignificant difference). Range of results from last ten years remaining melt is 3.96 to 4.60 million km2 - also a narrowing range. For a minimum at 2nd lowest remaining melt needs to be about 15% above average. For a new record low remaining melt would need to be 2.16 million km2 as opposed to the average remaining melt of 1.10 million km2, i.e 1.06 million (96 %) above the average. Not feasible.

Of interest (?) is that in 2012 melt from this point was just 0.27 million (25%) above the average remaining melt.

That 2017 feeling wanes and waxes- extent losses are only slowly (or not at all) catching up on the slow melt to date and NSIDC Area losses have slowed significantly. There is, on average, just 11% (28 days) of further extent loss to go. Could the melting season last a bit longer than that - Yes.  On the other hand, could extent loss sharply reduce? Yes.

A September minimum in the range of 4.00 to 4.50 million km2 seems probable, with the result of least drama at 0.2 million km2 above 2nd place and about 1 million km2 above the 2012 outlier.

47
Arctic sea ice / Re: The 2018 melting season
« on: August 14, 2018, 05:07:46 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-08-13...

48

Lets assume that trend is linear.


But perhaps let us not ?

49
Arctic sea ice / Re: 2018 sea ice area and extent data
« on: August 08, 2018, 08:03:16 AM »
The compactness mystery has something to do with the differences between NSIDC and AMSR2 due to differences in sensors and algorithms. AMSR2 compactness is more middle-of-the-road, while NSIDC and is rather high. Wipneus as usual comes to the rescue. Click images for better resolution. Bookmark the links.

https://sites.google.com/site/arctischepinguin/home/amsr2/grf/amsr2-compact-compare.png?attredirects=0

https://sites.google.com/site/arctischepinguin/home/amsr2/grf/amsr2-area-all-cmpare.png?attredirects=0

https://sites.google.com/site/arctischepinguin/home/amsr2/grf/amsr2-extent-all-cmpare.png

50
Arctic sea ice / Re: "Stupid" Questions :o
« on: August 08, 2018, 01:37:01 AM »
One thing that bothers me deeply is the lack of discussion regarding the entirety of GHGs' current effects. Typically only CO2 is discussed, and methane is mentioned as some sort of slight addition and a possible problem if permafrost rapidly thaws.

When methane is discussed it is almost never done with reference to the current forcing from CH4 levels. The 20, 50, and 100 year effective warming potentials are very important, but that is not what effects climate this year or next year or the year after. Methane's lifespan is like a decade, so even 20 year effect drastically understates the warming relative to the current effect.
...

This is something that also bugs me and I look forward to seeing an answer.  I suspect a proper analysis will include the earth's spectral radiation plot as measured from space, a la : https://www.giss.nasa.gov/research/briefs/schmidt_05/

https://link.springer.com/article/10.1007/s40641-016-0039-5



I would like to see a proper answer too.

What I take from the following image:



is that one of the CO2 peaks falls in a H2O trough and thus is highly effective. Whereas the methane peaks are somewhat covered by H2O.

Also the methane peaks seem rather sharp so does this mean that widening those peaks doesn't have much effect, whereas broadening CO2 peaks which are wider has larger effect?

So while some methane has some effect, adding more doesn't have much extra effect whereas for CO2 adding more does have more sizeable effect.

Perhaps all this is built into the GW potential numbers and doesn't affect the calculations you are doing.

I am not expert enough to know.

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