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When will the Arctic Extent dip below 1,000,000 Km^2

2018-2019
12 (17.9%)
2020-2025
21 (31.3%)
2026-2030
13 (19.4%)
2031-2040
15 (22.4%)
2041-2060
2 (3%)
2061-2080
0 (0%)
2081-2099
1 (1.5%)
2100-beyond
3 (4.5%)

Total Members Voted: 64

Voting closed: July 27, 2018, 07:46:32 AM

Author Topic: When will the Arctic Go Ice Free?  (Read 187436 times)

wdmn

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Re: When will the Arctic Go Ice Free?
« Reply #1450 on: December 08, 2019, 03:18:47 PM »
@ Stephan
Thanks for the link.

vox_mundi

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Re: When will the Arctic Go Ice Free?
« Reply #1451 on: December 13, 2019, 04:57:03 PM »
Comparison of Climate Simulations with Proxies Suggests Arctic Sea Ice Could Vanish in Summer Sooner than Expected
https://phys.org/news/2019-12-comparison-climate-simulations-proxies-arctic.html

Climate models suggest that at some point in the near future, all of the Arctic sea ice will melt each summer. In this new effort, the researchers suggest that it will be sooner than climate models have been suggesting. The work involved exploring why proxy data shows the planet heating up more during a prior global warming period 6,000 to 8,000 years ago (called the Holocene thermal maximum) than current climate models. Proxies are things such as preserved pollen or ice cores from a given time period that give hints about temperatures during that period—since humans were not able to record temperatures at the time, scientists use these proxies instead.

The work by the researchers in Korea involved running 13 climate models to learn more about the thermal maximum, and then comparing what they showed with proxies. They report that they found that the most up-to-date simulations showed a bigger decline in Arctic sea ice than older models (because the ice would have continued melting into early winter), possibly explaining the discrepancy between proxy data and older simulations. They further suggest that their findings do not bode well for the current warming trend, because it suggests that Arctic sea ice will begin vanishing sooner than older climate models have predicted—and less ice means less energy reflection, contributing to faster global warming.


Fig. 2: Surface temperature and Arctic sea ice responses: (A and B) Zonally averaged, latitude-time Hovmöller plots of surface temperature anomalies in (A) the four warmest models and (B) the four coldest models. The abscissa is time (months) and the ordinate is latitude. Arctic sea ice concentration (SIC; %) anomalies in (C and D) the four warmest models and (E and F) the four coldest models, averaged in (C and E) July to November and (D and F) December to April.

The zonal mean time-latitude Hovmöller plots of surface temperature show that high-latitude (60°N-85°N) warming in summer persists into winter in the four warmest models (Fig. 2A), whereas the summer warming does not persist in the four coldest models (Fig. 2B). These results appear robustly in the case when the second and third warmest/coldest models are chosen for the Hovmöller plots of surface temperature (fig. S4), verifying that the seasonally persistent high-latitude warming is a general feature of warm models rather than an average artifact associated with the extremely warm model, CNRM-CM5. These results indicate that the key difference between the warmest and the coldest models is the magnitude of summer heating and its persistence into winter.

In the warmest models, Arctic sea ice concentration (SIC) in summer-autumn decreases by 30 to 35% over wide areas of the Arctic relative to the preindustrial climate (Fig. 2C), and these SIC anomalies persist into winter and early spring over the marginal ice zone (Fig. 2D), indicative of delayed refreezing and reduced ice growth (28). This autumn-winter sea ice loss is accompanied by increases in heat transfer from the Arctic Ocean to the atmosphere, primarily through turbulent heat fluxes (fig. S5), further contributing to the Arctic amplification via the cloud radiative feedback (28–30). Moreover, the near-surface temperature inversion in the cold season confines the warming to the surface (30), and the associated weakening of temperature inversion can contribute to the Arctic amplification (23).

... The Arctic sea ice cover during the HTM was likely smaller than the preindustrial climate, as shown by proxy records (8, 9), which is consistent with a substantial Arctic warming in the mid-Holocene.

Quote
... this finding has implications for the projection of future climate change. Climate models simulating more Arctic sea ice loss in response to the mid-Holocene insolation generally exhibit higher sensitivities to an increased CO2 concentration (38). Therefore, our results suggest that the projected Arctic sea ice decline will likely to be faster than the multimodel ensemble mean prediction.

Open Access: Hyo-Seok Park et al. Mid-Holocene Northern Hemisphere warming driven by Arctic amplification, Science Advances (2019).

Abstract

The Holocene thermal maximum was characterized by strong summer solar heating that substantially increased the summertime temperature relative to preindustrial climate. However, the summer warming was compensated by weaker winter insolation, and the annual mean temperature of the Holocene thermal maximum remains ambiguous. Using multimodel mid-Holocene simulations, we show that the annual mean Northern Hemisphere temperature is strongly correlated with the degree of Arctic amplification and sea ice loss. Additional model experiments show that the summer Arctic sea ice loss persists into winter and increases the mid- and high-latitude temperatures. These results are evaluated against four proxy datasets to verify that the annual mean northern high-latitude temperature during the mid-Holocene was warmer than the preindustrial climate, because of the seasonally rectified temperature increase driven by the Arctic amplification. This study offers a resolution to the “Holocene temperature conundrum”, a well-known discrepancy between paleo-proxies and climate model simulations of Holocene thermal maximum.
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1452 on: December 15, 2019, 01:15:47 AM »
"When will the Arctic see its first ice-free summer?"
  Nice review by Daisy Dunne at Carbon Brief.
https://interactive.carbonbrief.org/when-will-the-arctic-see-its-first-ice-free-summer/#

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1453 on: December 15, 2019, 08:36:51 AM »
It is time for the monthly update of my extrapolation when the extent [Extent], volume [Volumen], thickness [Dicke] and area [Fläche] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times (valid for volume, area and thickness, not for extent in the winter months). The November value now includes 2019.
Extent, area, volume and thickness for November 2019 lie at or slightly below the long term trend lines. The "BOE numbers" decreased by averaged 2 years (extent and area) and left this number unchanged compared with November 2018 (volume and thickness). This differentiation, already observed in Sep and Oct 2019, seems to continue and could thus merge in many years.
The order (earlier → later BOE) generally is volume < thickness < area < extent.

Please note that this is not a forecast but a trend!
See attached table.
It is too late just to be concerned about Climate Change

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1454 on: December 17, 2019, 04:05:02 AM »
[ Correction to earlier post:  A while back I threw in a comment that when ice thickness gets below 0.5-0.8 meter it becomes susceptible to flash melt, but that I could not remember the source.  Well, I still can't find it, and looking at ASI thickness data, the greatest one month decline in thickness during melt season (thickness values get skewed by refreezing ice in fall-winter) is less than 0.3m.  So I was wrong.  The annual pattern is about 0.8 to 1.0 meter thickness decline across each entire April to September melt season. ]

-------------------
 I came across some interesting tidbits about ASI thickness at https://nsidc.org/cryosphere/sotc/sea_ice.html

"Using data from submarine cruises, Rothrock and collaborators determined that the mean ice draft (the ice extending below the water surface) at the end of the melt season in the Arctic decreased by about 1.3 meters between the 1950s and the 1990s."

"Examining 42 years of submarine records (1958 to 2000), and a five years of ICESat records (2003 to 2008), the authors determined that mean Arctic sea ice thickness declined from 3.64 meters in 1980 to 1.89 meters in 2008—a decline of 1.75 meters."

(between 2003-2008 and 2010-2012)  "...sea ice volume declined by 4,291 cubic kilometers at the end of summer, and 1,479 cubic kilometers at the end of winter (Laxon et al. 2013)."

They include a chart from Kwok and Rothrock 2009 that shows nearly identical thickness declines of ~50% between 1958-76 and 2003-2007 in different Arctic subregions (Chukchi, Beaufort, Canada Basin, North Pole, Nansen Basin, Eastern Arctic.)   No apparent differentiation between North Pole and the others.

A linear trend line of whole-Arctic September Volume shows a decline from 11.1 to 4.2 M Km3 from 2000 to 2019, a 62% decline

For the CAB volume alone, the decline is from 8.4 to 3.8 M km3, a 55% decline.  So the CAB has lost volume at a slightly slower rate, but not much slower. 

I think this argues against the idea that progression towards a largely ice free September (followed by August, October, July) will be stalled because the final ice refuge is at too high a latitude. 

The Sept. ice is not centered around 90N anyway, but is centered south of 90N on the Greenland/Canadian side.  The location of the remaining Sept. ice does not match bathymetry very well.  So I don't see that as a saving grace either.  I think protection by location matters even less when you factor in the increasing mobility of thinning ice, reduction of land fast ice, and increased open water/wind fetch, and storm potential as Arctic water warms.

Based on all that it seems that the straight line trend for volume (e.g. Stephan, Wipneus) is the best predictor.  If so, then there will be a lot of headlines in 2032 to 2035 as September goes to Zero, followed shortly after by August and October.  I say will instead of "would" because with the lag of the effect on global average temperature from CO2 emissions being at least 10 years (for about half the temperature effect, to ca. 30 years for most of it), the fact that the projected zero monthly ASI volume dates are only 12-15 years away indicates that we already committed to those changes even if we finally got serious about reducing emissions starting in 2020 (which nobody thinks is going to happen in 2020).

The science on how ASI reduction affects weather is still unsettled, but regardless of the details, Jennifer Francis' quote makes a lot of sense ~ How could removing so much Arctic ice NOT affect the weather?

July hitting zero before August in Stephan's table must be a mathematical fluke caused by a slightly steeper decline rate being extrapolated into the future.  On the Wipneus graph, July volume lags about 12 years behind August, which does make sense. 
https://sites.google.com/site/arctischepinguin/home/piomas   

« Last Edit: December 18, 2019, 07:28:41 AM by Glen Koehler »

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1455 on: December 17, 2019, 06:22:00 AM »
The Sept. ice is not centered around 90N anyway, but is centered south of 90N on the Greenland/Canadian side.  The location of the remaining Sept. ice does not match bathymetry very well.  So I don't see that as a saving grace either.  I think protection by location matters even less when you factor in the increasing mobility of thinning ice, reduction of land fast ice, and increased open water/wind fetch, and storm potential as Arctic water warms.

Based on all that it seems that the straight line trend for volume (e.g. Stephan, Wipneus) is the best predictor. 

Well argued. A year or two back there was another discussion regarding landfast ice, which got me thinking that the "classic" idea of the last of the ice somehow clutching the Greenland / CAA coasts perhaps didn't hold up.

The linear downward trend in ice volume may well see a precipitous drop because of rapidly increasing moveability - the less ice, the easier it will be for winds to push it around. Given that windiness in the Arctic may be on the increase because of diminishing ice cover, the effect may well become significant.

So I'm thinking that mobility of the ice pack is going to increase non-linearly, i.e. that in the coming years we will see a new behaviour emerge, where the ice pack is suddenly much more moveable and therefore mobile than before.

And a more mobile ice the ice pack is during melt season, the faster it is going to melt in my opinion. So instead of being "protected" at the top of the world, a diminished ice pack is going to be kicked around by winds and weather, and melting much faster than before.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1456 on: December 17, 2019, 09:47:54 PM »
(quote from Glen Koehler) "July hitting zero before August in Stephan's table must be a mathematical fluke caused by a slightly steeper decline rate being extrapolated into the future."

Of course this a mathematical effect and not "real". July's Arctic Ice Volume was very close to December's volume when the measurements started in 1979. Since around 2010 it comes much closer to November's volume. Therefore its slope is much steeper than in any other month, leading to a "slightly earlier" BOE in the extrapolation.
Maybe in the mid 2030s July will be ice free before August - although August would have been ice-free anyway that same year. Let's see what happens...
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Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1457 on: January 05, 2020, 09:21:34 PM »
It is time for the monthly update of my extrapolation when the extent [Extent], volume [Volumen], thickness [Dicke] and area [Fläche] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times (valid for volume, area and thickness, not for extent in the winter months). The December value now includes 2019.
Extent, area and - a bit less - volume for December 2019 lie above the long term trend lines whereas thickness almost matched it. The "BOE numbers" increased by averaged 7 years (extent and area) and left this number unchanged compared with December 2018 (volume and thickness). This differentiation is in contrast to the observation in the previous months, but easily explainable by the higher than average gains in area and extent compared to last year(s).
The order (earlier → later BOE) generally is volume < thickness < area < extent.

Please note that this is not a forecast but a trend!
See attached table. stg = slope.
It is too late just to be concerned about Climate Change

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1458 on: February 02, 2020, 09:43:30 PM »
2019 was 2nd lowest minimum in the satellite record, and freezing was very late.

Did it make much difference ? Out of the cupboard comes my once a year graphs of the number of days when ice area for each sea was less than 15% of total area of each sea (or less than the 1980s maximum for seas bounded by open ocean, e.g. the Bering)

Some seas, e.g. the East Siberian Sea, had record numbers of days of very low or zero ice-free conditions. Others did not. There are 6 graphs, so 2 posts.


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gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1459 on: February 02, 2020, 09:45:09 PM »
Last 2 graphs attached

2019 was 2nd lowest minimum in the satellite record, and freezing was very late.

Did it make much difference ? Out of the cupboard comes my once a year graphs of the number of days when ice area for each sea was less than 15% of total area of each sea (or less than the 1980s maximum for seas bounded by open ocean, e.g. the Bering)

Some seas, e.g. the East Siberian Sea, had record numbers of days of very low or zero ice-free conditions. Others did not. There are 6 graphs, so 2 posts.
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Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1460 on: February 03, 2020, 05:40:12 PM »
Thank you gerontocrat for these impressive graphs.
Funny, how the "wobbling up and down" of almost every single sea smoothes out in the last graph...
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Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1461 on: February 07, 2020, 09:14:55 PM »
It is time for the monthly update of my extrapolation when the extent [Extent], volume [Volumen], thickness [Dicke] and area [Fläche] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times (valid for volume, area and thickness, not for extent in the winter months). The January value now includes 2020.
Extent, area and volume for January 2020 lie well above the long term trend lines whereas thickness is only slightly above it. The "BOE numbers" increased by averaged 8 years (extent) and 2 years (volume) whereas the "BOE number" for thickness has decreased by 3 years compared to January 2019.
The order (earlier → later BOE) generally is volume < thickness < area < extent.

Please note that this is not a forecast but a trend!
See attached table. stg = slope.
It is too late just to be concerned about Climate Change

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1462 on: March 04, 2020, 04:41:24 AM »
FYI:
Interactive: When will the Arctic see its first ice-free summer?
Words by Daisy Dunne. Design by Tom Prater.
https://interactive.carbonbrief.org/when-will-the-arctic-see-its-first-ice-free-summer/
   Article not dated, but must have been written after November 18, 2019, and it includes graphs showing 2019 minimum.

   "For example, in recent years, scientists have observed an increase in the speed at which sea ice grows in the winter. This is partly because “thinner ice can grow much faster than thicker ice”, says Tsamados. “This is a negative feedback – a kind of resilience in the system.”

    "However, the increase in sea-ice growth observed in winter is not enough to counter the rapid rise in melting seen in the summer months, he adds. “We’re putting out so much CO2 that the Arctic just cannot fight back. Right now, the positive feedbacks are winning against the negative feedbacks – and that means that sea ice is going down the drain.”  "

-------
If temperatures rise by 2C
    "...the Arctic has a one-in-five chance of seeing its first ice-free summer in 2035, according to the study. The chances of an ice-free summer in any given year rise to one-in-two by 2045."

-------
   "A landmark report on oceans and ice published this year by the Intergovernmental Panel on Climate Change (IPCC) found that up to half of the observed decline in summer sea ice could be down to natural variability in the Arctic climate."

    "A study published in 2016 calculated that natural variability in the Arctic system amounted to around two decades of uncertainty. This means that any ice-free summer forecast may need to have a 20-year window, just to account for the influence of natural events and processes."

kassy

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Re: When will the Arctic Go Ice Free?
« Reply #1463 on: March 04, 2020, 03:03:12 PM »
So that is 25 years out

CTRL + F this in the article to jump to the graph:
The probability of the Arctic seeing its first ice-free summer from 2020-2100 under a range of future scenarios, including where global temperature rise is limited to 1.5C (yellow), 1.5C with “temperature overshoot” (blue) and 2C (light blue). Scenarios where these temperature targets are exceeded are also shown. This includes a scenario of moderately high emissions (RCP4.5; dark blue) and a scenario of very high emissions (RCP8.5; red). Adapted from Jahn et al. 2018.


1.5C hard max for the whole planet is the only safe option.

This also means the 2C upper limit of the Paris agreement is dangerous.
And that is just what our politicians pledge to and since they often fail to deliver there is a real risk of overshooting that.

Of course following the logic of underdelivery 1C should have been the max...
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Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1464 on: March 11, 2020, 09:11:48 PM »
It is time for the monthly update of my extrapolation when the extent [Extent], volume [Volumen], thickness [Dicke] and area [Fläche] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times (valid for volume and thickness, not for extent and area in the winter months). The February value now includes 2020.
Extent, area and volume for February 2020 lie well above the long term trend lines whereas thickness is only slightly above it. The "BOE numbers" increased by averaged 12 years (extent) and 1 year (volume and thickness) compared to February 2019.
The order (earlier → later BOE) generally is volume < thickness < area < extent.

Please note that this is not a forecast but a trend!
See attached table. stg = slope.
It is too late just to be concerned about Climate Change

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1465 on: April 02, 2020, 05:25:52 PM »
Three Sea Ice Area Graphs attached from NSIDC data...

Total Area - all 14 Seas,
High Arctic - the main ocean - being Chukchi+Beaufort+CAA+Central Arctic Sea+Kara+Laptev+ESS,
The Peripheral Seas- Okhotsk+Bering+Hudson+St Lawrence+Baffin+Greenland+Barents.

I have used the same scale on all 3 graphs to get a better view of the differences.

Note the late melt of the High Arctic and the major reduction in minimum in the last 4 decades.
In the Peripherals melt starts earlier and nearly goes to zero. Ice loss shows in lower maxima and  through earlier melt.

I will be looking at extent, volume & thickness as self-isolation drag on. Maybe something will emerge re a guess at a BOE?
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gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1466 on: April 02, 2020, 06:42:19 PM »
& Now three Sea Ice EXTENT Graphs attached from NSIDC data...

Total EXTENT - all 14 Seas,
High Arctic - the main ocean - being Chukchi+Beaufort+CAA+Central Arctic Sea+Kara+Laptev+ESS,
The Peripheral Seas- Okhotsk+Bering+Hudson+St Lawrence+Baffin+Greenland+Barents.

Again I have used the same scale on all 3 graphs to get a better view of the differences.

Volume & thickness to come as self-isolation drag on. Maybe something will emerge re a guess at a BOE?
« Last Edit: April 02, 2020, 07:56:24 PM by gerontocrat »
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Pmt111500

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Re: When will the Arctic Go Ice Free?
« Reply #1467 on: April 02, 2020, 07:47:28 PM »
Thanks Gerontocrat. If you want to make maximums more to the same, just move Kara and Chukchi to peripherals.
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gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1468 on: April 02, 2020, 08:13:38 PM »
Thanks Gerontocrat. If you want to make maximums more to the same, just move Kara and Chukchi to peripherals.
For this exercise I use Nico Sun's definition of the High Arctic Seas he uses for his AWP models, which I surely hope he produces for this season. (se https://cryospherecomputing.tk/NRTawp ).

Also these 7 seas at maximum are entirely bordered by land and / or sea ice.
The peripheral seas even at maximum are either totally disconnected from the Central Arctic Ocean (e.g. the Okhotsk) or partially exposed to ocean open water even at maximum (e.g. the Bering Sea). They are the peripherals and definitely the expendables.

When looking at the Pacific Gateway the Bering is paired with the Chukchi, and increasingly the Pacific end of the Beaufort and East Siberian Seas. When looking at the Atlantic Front the Greenland Sea is paired with the Barents,, and increasingly the Atlantic end of the Kara and now the Laptev Seas. But that is a different exercise.

The BOE depends on the absence of sea ice in the High Arctic. Trends in earlier ice loss and later ice gain (extent, area, dispersion, volume) give clues to progress to the BOE that might be better extracted from looking at just the High Arctic instead of all the seas.

Horses for courses
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1469 on: April 03, 2020, 02:07:55 AM »
Arctic Sea Ice September Minimum estimates by 1979-2019 trend extrapolations
     The consensus definition of the first “ice free Arctic summer” is when the September minimum EXTENT goes below 1 million km2. 
Volume = Extent x average Thickness
Extent = Volume / average Thickness
-------------
     Terminology key:
     First value is midpoint estimate.  (Low – High) = 95% confidence interval,
i.e. +/- 1.96 standard deviations. 
     Exponential trend = 2nd order polynomial regression model, i.e. simple curve model, for 1979-2019 observations.
     Linear trend = 1st order linear regression, i.e. straight line model, for 1979-2019 observations.
     Standard deviations used for confidence intervals based on annual errors of Linear model vs. 1979-2019 observed values.
     M km2 and M km3 are Millions of squared or cubic kilometers.

EXTENT
a)  Exponential Extent trend
    Rationale - Positive feedbacks from loss of MYI, thin ice physical and biological characteristics (e.g. algal darkening on the underside of thin floes), more open water causes decreased summer albedo, open water effects on wind fetch and ice mobility, increased Atlantification and Pacification of the Arctic, CAA becomes another export gateway, possible halocline breakdown (esp. in the Beaufort), more open water in winter causes more water vapor over the Arctic thus increasing the thermal blanket to moderate winter low temperatures, black carbon forest fires,  permafrost thaw, oops, we never thought about that, continued GHG loading, increasing global average temperature.   
    Opinion - Too aggressive for extrapolation because it ignores compensating negative feedback.

 
2020:  4.0 (3.0 – 5.0) km2 September average Extent.
First Year for <3M km2 = 2028 (2021 – 2034)
First Year for <2M km2 = 2034 (2028 – 2040)
First Year for <1M km2 =  2040 (2034 – 2045)
First Year for 0 km2 = 2045 (2040 – 2050)

---------------------------
b) Gompertz Extent curve - no data

---------------------------
c)  Linear Extent trend
     Rationale – The simplest model is the safest bet.  Occam’s razor.  The extra term in the exponential model was not statistically significant. Allows for both positive and negative feedbacks.

2020:  4.3M (3.3 – 5.3) km2 September average Extent

*** The extrapolated linear September Volume and Extent linear trends are incompatible.  If Volume reaches zero in 2033 (2024 – 2041), there would be no ice to create Extent.***   
First Year for <3M km2 = 2037 (2024 – 2049)
First Year for <2M km2 = 2049 (2037 – 2061)
First Year for <1M km2 = 2061 (2049 – 2073)
First Year for 0 km2 = 2073 (2061 – 2085)

---------------------------
Improved EXTENT prediction accuracy as melt season observations become available.
    R-square for reduction in variability of estimates derived from R values posted by Stephan at https://forum.arctic-sea-ice.net/index.php/topic,2888.msg248300.html#msg248300
 
    Confidence interval reduction for estimated September average Extent with MARCH, APRIL, or MAY observations as predictors: Not much.

---- See NSIDC “Maximum extent is not predictive of minimum extent” https://nsidc.org/arcticseaicenews/2020/03/
“Plotting the de-trended maximum versus minimum extent (Figure 2) shows a near-random distribution.” 
“The seasonal maximum extent and the September minimum extent are not correlated” … “because summer weather conditions strongly shape the September minimum.”

Figure 2. This plot compares de-trended maximum extent (x-axis) with minimum extent (y-axis). The yearly values shown are calculated by subtracting the linear trend value for that year from the total extent.  Credit: W. Meier, NSIDC
-----
     Linear model estimate for 2020 September average Extent before any 2020 observations:  4.3M +/- 1.0 km2, (95% of outcomes expected to be within 3.3 – 5.3M km2,
i.e  +/- 1.0M km2)

     With JUNE Extent observation, confidence interval reduction: 22%
Width of 95% CI with June observation:  +/- 0.8M km2
     
     With  JULY Extent observation, confidence interval reduction: 56%
Width of 95% CI with July observation:  +/- 0.5M km2
     
     With AUGUST Extent observation, conf. interval reduction: 87%
Width of 95% CI with August observation:  +/- 0.14M km2
« Last Edit: April 03, 2020, 03:00:18 AM by Glen Koehler »

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1470 on: April 03, 2020, 02:11:00 AM »
*******************
*******************
VOLUME
a. Exponential Volume trend
     Rationale – There have been rapid climatic shifts in the past. .
2020: 2.5M (0.3 – 4.9) km3 September average Volume.
First Year for <3M km3 = 2020 (2020 – 2024)
First Year for <2M km3 = 2021 (2020 – 2026)
First Year for <1M km3 = 2023 (2020 – 2027)
First Year for 0 km3 = 2025 (2021 – 2029)


---------------------------
b. Gompertz Volume curve (eyeball estimates from Wipneus chart at https://sites.google.com/site/arctischepinguin/home/piomas
     Rationale - Loose proxy for increased negative feedback as declining September minimum ASI results in more fall and winter open water and less Arctic Ocean water insulation and thus greater winter heat loss and more rapid winter refreeze,  i.e. a tip of the hat to the “long slow final decline” hypothesis.
2020:  2.8M (1.0 – 4.5) km3 September average Volume.
First Year for <3M km3 = 2021 (2020 – 2027)
First Year for <2M km3 = 2023 (2020 – ca. 2029)
First Year for <1M km3 = 2027 (2020 – ?)
First Year for 0 km3:  no data.


---------------------------
c. Linear Volume trend
      Rationale – The simplest model is the safest bet.  The extra term in the exponential regression was not statistically significant.
2020:  3.9M (1.2 – 6.6) km3 September average Volume.
First Year for <3M km3 = 2023 (2020 – 2032)
First Year for <2M km3 = 2026 (2020 – 2035)
First Year for <1M km3 = 2030 (2021 – 2038)
First Year for 0 km3 = 2033 (2024 – 2041)

---------------------------
Improved Volume prediction accuracy as melt season observations become available.
      R-square reduction in variability derived from R values posted by Stephan at https://imgur.com/a/O82kzZZ

      Linear model estimate for 2020 September average Volume before any 2020 observations:  3.9M (1.2 – 6.6) km3, (95% of outcomes expected to fall within 1.2 – 6.6M km3,
i.e  +/- 2.7M km3).
   
    With MARCH observation as predictor, confidence interval (CI) reduction for September average Volume estimate: 3.6%.
Width of 95% CI with March observation: +/- 2.6M km3
   
    With APRIL Volume observation, conf. interval reduction: 7.2%
Width of 95% CI with April observation: +/- 2.5M km3

    With MAY Volume observation, confidence interval reduction: 32%
Width of 95% CI with May observation: +/- 1.9M km3

    With JUNE Volume observation, confidence interval reduction: 63%
Width of 95% CI with June observation: +/- 1.0M km3

    With JULY Volume observation, confidence interval reduction: 83%
Width of 95% CI with July observation: +/- 0.5M km3

    With AUGUST Volume observation, conf. interval reduction: 94%
Width of 95% CI with August observation: +/- 0.2M km3
« Last Edit: April 03, 2020, 02:35:07 AM by Glen Koehler »

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1471 on: April 06, 2020, 12:39:39 AM »
Quote
2012 was a shooting star - phut, & it was gone. 2016 was the steady burn that really matters.
But there could be another shooting star in 202X. This will be at least as likely to be the first BOE as is a gradual drop down year by year.
There will be another (at least one) shooting star in 202X, including the first BOE year.
   I don't see a basis for expecting a BOE in 2020.  Granted the system is giving hints of qualitative, functional change (the Beaufort Sea could be the linchpin) but there is still too much ice to get to BOE this year. 

     Stephan - your own regressions say that we are still some years away from a likely BOE, and that end-of-March observations are not very predictive of September for Extent or Volume, so I don't understand your reasoning if I interpret your post as saying a BOE is likely in 2020.

     Are you expecting massive export in 2020 as ASI ice pack loses structural integrity and resistance to currents and wind, and just flushes out the Fram Strait?  That seems to be the only way to reach BOE in 2020.  Even a repeat of 2019's string of warm months was only able to melt the ice down to just above 4M km2.  What's going to cause an unprecedented 3M km2 drop in one year?

    Or did I misinterpret your post?

philopek

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Re: When will the Arctic Go Ice Free?
« Reply #1472 on: April 06, 2020, 01:01:37 AM »
But there could be another shooting star in 202X. This will be at least as likely to be the first BOE as is a gradual drop down year by year.
There will be another (at least one) shooting star in 202X, including the first BOE year.
   I don't see a basis for expecting a BOE in 2020.  Granted the system is giving hints of qualitative, functional change (the Beaufort Sea could be the linchpin) but there is still too much ice to get to BOE this year. 

     Stephan - your own regressions say that we are still some years away from a likely BOE, and that end-of-March observations are not very predictive of September for Extent or Volume, so I don't understand your reasoning if I interpret your post as saying a BOE is likely in 2020.

     Are you expecting massive export in 2020 as ASI ice pack loses structural integrity and resistance to currents and wind, and just flushes out the Fram Strait?  That seems to be the only way to reach BOE in 2020.  Even a repeat of 2019's string of warm months was only able to melt the ice down to just above 4M km2.  What's going to cause an unprecedented 3M km2 drop in one year?

    Or did I misinterpret your post?
[/quote]

202X is as close to exclusion of 2020 as one can get but however it is certainly not meant to say 2020 but anything 202?.

In short, he did not say 2020 but 202X which is not the same

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1473 on: April 06, 2020, 02:12:05 AM »
ooops, so indeed I was misreading it.   Big difference between an X and O! ::)
« Last Edit: April 06, 2020, 02:19:37 AM by Glen Koehler »

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1474 on: April 08, 2020, 02:02:28 PM »
It is time for the monthly update of my extrapolation when the extent [Ausdehnung], volume [Volumen], thickness [Dicke] and area [Fläche] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times (valid for volume and thickness, not for extent and area in the winter months). The March value now includes 2020.
Extent, area and volume for March 2020 lie well above the long term trend lines whereas thickness is only slightly above it. The "BOE numbers" increased by averaged 11 years (extent) and did not change (volume and thickness) compared to March 2019.
The order (earlier → later BOE) generally is volume < thickness < area < extent.

Please note that this is not a forecast but a trend!
See attached table. stg = slope.
« Last Edit: April 08, 2020, 02:29:42 PM by Stephan »
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1475 on: April 09, 2020, 01:57:50 AM »
  The consensus definition of Arctic Ocean BOE is when Extent is below 1 million km2.

   The observed linear trend for decline in Volume is much steeper than the linear trend for decline of Extent.  Ultimately, zero Volume means zero Extent, so the two trends have to meet as Volume approaches zero.

   So instead of using the linear trend for observed Extent, I used the linear trend for Extent as estimated from Volume and Thickness, i.e. E = V/T.  The standard deviation of errors from using that method of estimating Extent from 1979 through 2019 was 0.543 km2.  (Linear trend Volume and linear trend Thickness were used to estimate Extent.  The estimate was compared to the observed Extent for each year to measure the annual estimate error.)
   
    The Volume and Thickness trends were extrapolated into the future and used to estimate future Extent.  The standard deviation for errors using that method and assumption of a normal distribution were used to estimate the probability for how likely Extent in that year would be below 1.0 million km2.  Individual year probabilities for <1 million km2 were used to calculate the cumulative chance for first BOE. 

     Extrapolating linear trends far into the future ignores potential negative suppressive and positive reinforcing feedbacks.  The resulting percentages are fairly consistent with estimates based on trends and correlations described by Notz and Stroeve 2018 and Stroeve and Notz 2018 (https://forum.arctic-sea-ice.net/index.php/topic,2348.msg239574.html#msg239574) but are earlier than inferred from statements in the 2019 IPCC special report on the cryosphere.

    The bottom line is that according to these trends, the first BOE is likely to have occurred by 2029 and very likely by 2031.  Also note that Arctic sea ice variability is so high that is been said (2016 study cited Daisy Dunne in Carbon Brief article, https://forum.arctic-sea-ice.net/index.php/topic,2348.msg239698.html#msg239698) that any such estimate needs to include a +/- 20 year window to account for that variability!  So perhaps a better estimate would be "The next extremely warm melt season combined with Arctic storm activity." 

     The significance of all these numbers is that a critically important component of the Earth's climate system that has been relatively stable for thousands of years is expected to transition to a radically different state very soon.  While scientists are still trying to understand the impact of such a change on climate and on weather, as Jennifer Francis put it “How can it not affect the weather? It’s such a huge loss in the Earth’s system.”

                                       Extent     Number of    Single year   Cum.
          Thickness   Vol.      = V/T     StdDev from  chance Ext.   chance
 Year       (m)     (M km3)  (M km2)    1.0 km2     <1M km2    1st BOE
                                    
2020        1.05      3.92    3.72           5.0              0.0%       0.0%
2021        1.03      3.60    3.50           4.6              0.0%       0.0%
2022        1.00      3.28    3.27           4.2              0.1%       0.1%
2023        0.97      2.95    3.03           3.7              0.2%       0.3%
2024        0.95      2.63    2.78           3.3              0.6%       0.9%
2025        0.92      2.31    2.51           2.8              1.6%       2.5%
2026        0.89      1.99    2.22           2.3              4.1%       6.5%
2027        0.87      1.66    1.92           1.7              9.6%     15.5%
2028        0.84      1.34    1.60           1.1            19.8%     32.3%
2029        0.81      1.02    1.25           0.5            36.0%     56.6%
2030        0.79      0.70    0.89          -0.2            56.4%     81.1%
2031        0.76      0.37    0.49          -0.9            76.4%     95.5%
2032        0.73      0.05    0.07          -1.7            90.6%     99.6%
 
« Last Edit: April 09, 2020, 08:00:43 PM by Glen Koehler »

The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1476 on: April 09, 2020, 02:06:53 AM »
That would be a good analysis, if your premise was correct.  Namely, that extent is a poor representation and volume is an excellent one.  Conversely, you could use extent and thickness, and determine volume in that manner.  Volume will always decrease faster than either of its dimension.  That is a mathematical fact.  Claiming that volume should lead extent and not the other way round is questionable.  Possible, but questionable.

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1477 on: April 09, 2020, 03:22:21 AM »
   I confess to treating the Wipneus straight line PIOMAS September volume trend like gospel. 

    We all agree that when any of the three (Extent, Thickness, Volume) hits zero, that wipes out the other two.  I guess a case can be made that the assumption that Volume drives Extent is just an assumption and no more valid than putting Extent or Thickness in charge.

    If I use the same method to estimate future September Volume from extrapolated linear trends for September Extent and Thickness, here is what results

Year      Ext    Thick   Volume =E*T
2020      4.34   1.05      4.57
2021      4.25   1.03      4.37
2022      4.17   1.00      4.17
2023      4.09   0.97      3.98
2024      4.01   0.95      3.79
2025      3.92   0.92      3.61
2026      3.84   0.89      3.43
2027      3.76   0.87      3.26
2028      3.68   0.84      3.08
2029      3.59   0.81      2.92
2030      3.51   0.79      2.76
2031      3.43   0.76      2.60
2032      3.35   0.73      2.45
2033      3.26   0.70      2.30
2034      3.18   0.68      2.16
2035      3.10   0.65      2.02
2036      3.02   0.62      1.88
2037      2.93   0.60      1.75
2038      2.85   0.57      1.62
2039      2.77   0.54      1.50
2040      2.69   0.52      1.39
2041      2.61   0.49      1.27
2042      2.52   0.46      1.17
2043      2.44   0.44      1.06
2044      2.36   0.41      0.96
2045      2.28   0.38      0.87
2046      2.19   0.35      0.78
2047      2.11   0.33      0.69
2048      2.03   0.30      0.61
2049      1.95   0.27      0.53
2050      1.86   0.25      0.46
2051      1.78   0.22      0.39
2052      1.70   0.19      0.33
2053      1.62   0.17      0.27
2054      1.53   0.14      0.21
2055      1.45   0.11      0.16
2056      1.37   0.08      0.12
2057      1.29   0.06      0.07
2058      1.20   0.03      0.04
2059      1.12   0.00      0.00

   

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1478 on: April 09, 2020, 03:57:05 AM »
Single year and Cumulative probabilities for a ZERO volume year (as estimated in previous post).  Zero volume is unrealistic and the strictest possible definition for a BOE, but we have to have some criterion to estimate a date for BOE.

   Single year      Cum chance of first,
   chance of 0 Vol.     0 Vol. year

2020       3.0%           3.0%
2021       3.6%           6.5%
2022       4.3%         10.5%
2023       5.1%         15.1%
2024       5.9%         20.1%
2025       6.9%         25.6%
2026       7.9%         31.5%
2027       9.0%         37.7%
2028     10.2%         44.1%
2029     11.5%         50.5%
2030     12.8%         56.9%
2031     14.2%         63.0%
2032     15.7%         68.8%
2033     17.2%         74.2%
2034     18.8%         79.0%
2035     20.4%         83.3%
2036     22.0%         87.0%
2037     23.6%         90.0%
2038     25.2%         92.6%
2039     26.8%         94.6%
2040     28.4%         96.1%
« Last Edit: April 09, 2020, 05:02:12 AM by Glen Koehler »

wili

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Re: When will the Arctic Go Ice Free?
« Reply #1479 on: April 09, 2020, 04:05:37 AM »
That seems like a ridiculously extreme standard to set? Do you really think there will be a point anytime in the next century when ice isn't breaking off of GIS or CAA? As long as that is going on, there will be SOME ice in the Arctic Ocean. Right? Am I missing something here?

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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1480 on: April 09, 2020, 04:25:51 AM »
  One more for the road.   Requiring zero volume for an estimate of BOE based on V = E*T estimate seems too demanding. 

   The Extent-based definition of BOE at 1 million km2 is 13.7% of the 1979-1983 5-year average September Extent (7.31 km2).

   Let's use the same ratio for a Volume-based BOE definition.  The average September Volume in 1979-1983 was 14.95 km3. 
0.137 * 14.95 = 2.05 km3.

   Using that as the threshold for a BOE gives the following probabilities.

Year      Single year      Cumulative
            chance for       chance for 1st year
           < 2.05 km3      of < 2.05 km3
2020        15.0%            15.0%
2021        17.0%            29.4%
2022        19.1%            42.9%
2023        21.4%            55.1%
2024        23.7%            65.7%
2025        26.1%            74.7%
2026        28.5%            81.9%
2027        31.0%            87.5%
2028        33.5%            91.7%
2029        36.0%            94.7%
2030        38.6%            96.7%

« Last Edit: April 09, 2020, 04:54:08 AM by Glen Koehler »

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1481 on: April 09, 2020, 04:33:52 AM »
That seems like a ridiculously extreme standard to set? Do you really think there will be a point anytime in the next century when ice isn't breaking off of GIS or CAA? As long as that is going on, there will be SOME ice in the Arctic Ocean. Right? Am I missing something here?

     No, I don't think the Arctic Ocean and surrounding seas will have had a year that is entirely free of sea ice in September by 2030.  I agree that ice will be breaking of the GIS for centuries, thus preventing reaching absolute zero.

     It's not a prediction, it is just a hypothetical mathematical threshold for considering when the Arctic reaches some interpretation of being "effectively ice free". 

     Extrapolation of trends far into the future often results in unrealistic values.  But a straight line trend is less susceptible to this problem than a curved trend.  And in this case, 10 years from now is not that far beyond the 41-years of observations from which the trends were derived.

     Just as the Extent-based threshold for BOE leaves room for small pockets of residual resistant ice, and things like GIS calving, so should a Volume-based definition of BOE.  That's the reason for the follow-up post using a more lenient definition of BOE.

    The specific % and year numbers are not really the point.  They are just a vehicle to convey the fact that continuation of current trends leads to a radically altered Arctic in a very short number of years (actually, it has already been radically altered, but even more extreme change is coming).  The crisis is imminent.  We can stop using 2100 as the benchmark for climate change effects, because 2030 or 2040 will bring plenty of climate change impacts. 

    Anyone looking for a rationale for addressing climate disruption need look no further.  The Arctic alone provides irrefutable and compelling measured evidence that the current trajectory of greenhouse gas loading into the atmosphere will lead to catastrophic consequences much sooner than most people seem to realize.

    As the estimates show, even when there is high probability that a 1st September BOE has occurred, the following years are more likely than not to be above BOE status in September.  And even in the BOE years, there will be ice in August and October (for the early BOE years anyway).  The world won't end with first BOE.  But in terms of disrupting weather patterns, extreme weather, accelerated heating etc.,  Arctic Ocean BOE is a significant marker for the transition away from the climate stability that has allowed human civilization to thrive for the past 8,000 years. 

     Even with all our technological means to insulate ourselves from nature, agriculture and numerous other life support systems rely on a supportive climate foundation.  Food does not come from grocery stores.  Food calories ultimately depend on the right growing conditions defined by temperature, rainfall and other factors.
« Last Edit: April 09, 2020, 07:53:38 PM by Glen Koehler »

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1482 on: April 09, 2020, 02:11:40 PM »
That seems like a ridiculously extreme standard to set? Do you really think there will be a point anytime in the next century when ice isn't breaking off of GIS or CAA? As long as that is going on, there will be SOME ice in the Arctic Ocean. Right? Am I missing something here?
I think that, if we are talking about BOE, we mean sea ice. That is ice that is formed on the Arctic Ocean's surface during (late) autumn, winter and (early) spring. It should be "separated" from fast ice along the coasts (mainly Grønland) and from isolated icebergs that were produced by calving events, which will happen during the next century year-round for sure. Therefore the BOE discussion must exclude persistent fast ice and icebergs.
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The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1483 on: April 09, 2020, 03:01:15 PM »
That seems like a ridiculously extreme standard to set? Do you really think there will be a point anytime in the next century when ice isn't breaking off of GIS or CAA? As long as that is going on, there will be SOME ice in the Arctic Ocean. Right? Am I missing something here?
I think that, if we are talking about BOE, we mean sea ice. That is ice that is formed on the Arctic Ocean's surface during (late) autumn, winter and (early) spring. It should be "separated" from fast ice along the coasts (mainly Grønland) and from isolated icebergs that were produced by calving events, which will happen during the next century year-round for sure. Therefore the BOE discussion must exclude persistent fast ice and icebergs.

That would be a reasonable request in theory.  In practice, how can we separate the fast ice and icebergs from the surface ice?  The satellite data will treat them all equally.  Also, at what point out from land can we separate fast ice from surface ice, and when does a break in the surface ice transition to an iceberg?  When we discuss radiant energy, does not all ice behave similarly?

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Re: When will the Arctic Go Ice Free?
« Reply #1484 on: April 10, 2020, 06:04:28 AM »
That would be a reasonable request in theory.  In practice, how can we separate the fast ice and icebergs from the surface ice?  The satellite data will treat them all equally.  Also, at what point out from land can we separate fast ice from surface ice, and when does a break in the surface ice transition to an iceberg?  When we discuss radiant energy, does not all ice behave similarly?

i don't think the satellites used for sea ice extent would be ble to see most icebergs, (which btw are all produced by glacier calving). Besides most icebergs in the northern hemisphere  have their origins in Greenland glaciers along the east and west coasts and drift southwards,

Fast ice does not break up into icebergs. And true fast ice is very rare in the Arctic, I doubt that there are more than a few hundred km2 in total. Besides, once faced with an open ocean, the remaining fast ice would probably disappear very quickly.
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Pmt111500

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Re: When will the Arctic Go Ice Free?
« Reply #1485 on: April 10, 2020, 07:51:19 AM »
That would be a reasonable request in theory.  In practice, how can we separate the fast ice and icebergs from the surface ice?  The satellite data will treat them all equally.  Also, at what point out from land can we separate fast ice from surface ice, and when does a break in the surface ice transition to an iceberg?  When we discuss radiant energy, does not all ice behave similarly?

i don't think the satellites used for sea ice extent would be ble to see most icebergs, (which btw are all produced by glacier calving). Besides most icebergs in the northern hemisphere  have their origins in Greenland glaciers along the east and west coasts and drift southwards,

Fast ice does not break up into icebergs. And true fast ice is very rare in the Arctic, I doubt that there are more than a few hundred km2 in total. Besides, once faced with an open ocean, the remaining fast ice would probably disappear very quickly.

Yes, fast(ened) ice is almost all gone with the CAA-Greenland Megacrack, there used to be (in the 2000s even) over a million square-km batch of ice that did not move no matter what, but stayed fastened to the CAA and northern Greenland. Openings of Nares strait have emptied the Arctic of most of this, I guess over 5 meter thick ice.

Icebergs have been (and somewhat still are) a bit of a problem in Antarctic measurements, the larger thick ones are rather easily separated from sea ice by their thickness and salt content (there is none) even from orbit. Tracking of icebergs is valuable for science (and not only shipping) as they melt they change the chemistry of the ocean surface... but in the Arctic they don't disturb the yearly growth and waning of sea ice. Well maybe in Baffin Sea.
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Re: When will the Arctic Go Ice Free?
« Reply #1486 on: April 11, 2020, 06:45:20 PM »
I decided to look at whe the Arctic might be really ice free - i.e. near as dammit all year round.
To do that I decided to use volume (data from PIOMAS via Wipneus) and separate the 7 Peripheral Seas from the 7 High Arctic Seas.

The first 2 graphs are the monthly average graphs from 1979 to 2020.
Graph 1 shows that the High Arctic is losing ice substantially at all times of the year, though less in winter /early spring.

Graph 2 shows that the Peripheral Seas are losing ice at maximum, but do not quite completely melt out. In September about 150 km3 is left, compared with the 2010's maximum of around 4,500 km3. If the High Arctic follows that pattern eventually the Gompertz graph must arrive on the scene to make a big long right tail.

the second two graphs look at 365 day trailing average volume, again from 1979 to 2020.

Graph 3 shows Total, High Arctic and Peripheral sea ice volume and trend in '000 Km3.
Graph 4 shows the same data translated into an index, 1979 = 100.

The Peripheral Seas are losing volume more slowly that the High Arctic, simply because there is not a lot of volume left to lose in the late summer months.

But IFF** that linear trend continues, by 2050 85% of the ice is gone, and by 2060 the Arctic would be virtually ice-free apart from some bits and pieces in winter.

I guess inertia and a desire not to frighten the horses keeps most science looking to 2100, even though Calamity might turn up half a century earlier.
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PragmaticAntithesis

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Re: When will the Arctic Go Ice Free?
« Reply #1487 on: April 11, 2020, 07:00:43 PM »
Interesting how there's a lot of volume in the periphery seas for this time of year. Might this make the ice more resilient for the rest of early melt season?
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Re: When will the Arctic Go Ice Free?
« Reply #1488 on: April 11, 2020, 07:21:19 PM »
Interesting how there's a lot of volume in the periphery seas for this time of year. Might this make the ice more resilient for the rest of early melt season?
It may be a result of loads of ice export - including remnants of multi-year thick ice - from the Central Arctic Ocean into the Barents & Greenland Seas. So leaving the main Arctic with thinner ice.

Not so good for the High Arctic?
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Re: When will the Arctic Go Ice Free?
« Reply #1489 on: April 11, 2020, 08:07:21 PM »
I think the current distinction of a two tiered Arctic (Peripheral vs. High Arctic) is somewhat helpful, but not nearly as good as a three-tiered Arctic.

Some of the constraint to better reporting is presented by the way agencies like NSIDC provide the data which is categorized by geographic definition, rather than by likelihood of ice melting out at the September minimum.

If we look at where ice remains at the current September minimum, we see that it is primarily located in places characterized as places with deep water and far from a large heat advecting land mass such as Alaska or Siberia. These are north of 80N. The bulk of this is in the Central Basin.

Locations like the Chukchi, Kara, and areas of the Laptev, ESS and Beaufort which are well south of the 80N line are included in the definition of High Arctic, but actually have much more in common with the Peripheral Seas than the Central Basin from the standpoint of September minimum. Barring something mind boggling, we know those areas will melt out very year.

In the absence of having data available which differentiates according to likelihood of melt, it seems at least the geographic Central Basin should be seen as qualitatively different than the rest of the High Arctic and considered as a separate third tier.
« Last Edit: April 12, 2020, 02:25:23 AM by Phoenix »

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Re: When will the Arctic Go Ice Free?
« Reply #1490 on: April 11, 2020, 08:59:10 PM »
    Thanks Gerontocrat.  That's devastating.  (That's like thanking a cancer doctor for news about a brain tumor.  But better to know the truth than not).

    One wonders what profound and cascading impacts an 85% loss in the 12-month running average Arctic sea ice volume would/will create, such as a decrease in April - August albedo, increase in October - March ocean heat transfer to the atmosphere, increase in Arctic water vapor, altered polar jet stream strength-path-stability, and altered ocean currents.  Individually each is ominous, and even worse when you consider the potential for interactions.

   It will be interesting to see what the CMIP6 models have to say.  The CMIP5 models did not represent ASI loss very well.  New factors have been added and refinements made to existing factors for the new generation of CMIP6 models.  The CMIP6 models are supposed to be operational by August 2020, though reportedly some portion won't make that deadline.  And it will probably take until the next IPCC reports in 2021 to see a comprehensive analysis of output from those supposedly enhanced models. 

     The next batch of IPCC reports are due in 2021 (April - physical science, September - mitigation, October - impacts, vulnerability, & adaptation).  The final synthesis report is due the first half of 2022.  Those reports could be the sink or swim message that finally generates concerted global action.  Maybe the current COVID pandemic provides a valuable lesson that the world can change quickly, that we are interdependent, and that global cooperation is essential.

     
« Last Edit: April 12, 2020, 12:09:05 AM by Glen Koehler »

Hefaistos

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Re: When will the Arctic Go Ice Free?
« Reply #1491 on: April 12, 2020, 01:43:47 AM »
...
But IFF** that linear trend continues, by 2050 85% of the ice is gone, and by 2060 the Arctic would be virtually ice-free apart from some bits and pieces in winter.


Thanks Geron.
You are indulging in making projections based on historic data, that has a trend, and seasonal patterns.
it would be very helpful to also get the standard deviations of your projections revealed!
As it is now, you present one projection but we have no idea what the probability distribution looks like for different future dates. Only that it's bounded below to zero...

It's easy enough in Excel to calculate sd's.

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Re: When will the Arctic Go Ice Free?
« Reply #1492 on: April 12, 2020, 10:14:26 AM »
...
But IFF** that linear trend continues, by 2050 85% of the ice is gone, and by 2060 the Arctic would be virtually ice-free apart from some bits and pieces in winter.

Thanks Geron.
You are indulging in making projections based on historic data, that has a trend, and seasonal patterns.
it would be very helpful to also get the standard deviations of your projections revealed!
As it is now, you present one projection but we have no idea what the probability distribution looks like for different future dates. Only that it's bounded below to zero...

It's easy enough in Excel to calculate sd's.
I could add all sorts of fancy what-ifs, maybes and sensitivity analyses but this would simply distract from the message - which is - this is the road we have traveled on, are travelling on, and will travel on unless something changes not just substantially, but dramatically. If covid-19 results in a long-term Global Recession with CO2 emissions 30% lower than today, atmospheric CO2 ppm will continue to rise - just a bit less fast.

A warmer Arctic means less ice. Less ice means a warmer Arctic.

Nevertheless, I expect I will be digging around trying to find new ways of looking at & in the data for some time to come. Lock-Down Rules, OK!
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Re: When will the Arctic Go Ice Free?
« Reply #1493 on: April 12, 2020, 04:35:00 PM »

But IFF** that linear trend continues, by 2050 85% of the ice is gone, and by 2060 the Arctic would be virtually ice-free apart from some bits and pieces in winter.



Thanks gerontocrat...great post.

I still can't help but think the Arctic Ocean, once ice free in the fall, will behave much like Hudson Bay does now, thin ice forming over much of the ocean only to melt out completely the following year.

Seasonally ice free for a very long time.

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Re: When will the Arctic Go Ice Free?
« Reply #1494 on: April 13, 2020, 04:21:17 AM »
I think the current distinction of a two tiered Arctic (Peripheral vs. High Arctic) is somewhat helpful, but not nearly as good as a three-tiered Arctic.

Some of the constraint to better reporting is presented by the way agencies like NSIDC provide the data which is categorized by geographic definition, rather than by likelihood of ice melting out at the September minimum.

If we look at where ice remains at the current September minimum, we see that it is primarily located in places characterized as places with deep water and far from a large heat advecting land mass such as Alaska or Siberia. These are north of 80N. The bulk of this is in the Central Basin.

Locations like the Chukchi, Kara, and areas of the Laptev, ESS and Beaufort which are well south of the 80N line are included in the definition of High Arctic, but actually have much more in common with the Peripheral Seas than the Central Basin from the standpoint of September minimum. Barring something mind boggling, we know those areas will melt out very year.

In the absence of having data available which differentiates according to likelihood of melt, it seems at least the geographic Central Basin should be seen as qualitatively different than the rest of the High Arctic and considered as a separate third tier.
Very true. Looking at area, extent, volume without separating for regions that behave completely differently is of limited value. Specifically, I have long been bothered by the CAB sector near the Svalbard-FJL line, which I see as belonging to the second tier rather than the third tier. This makes the huge CAB region more noisy than it should. Besides, NSIDC's CAB is much smaller than Wipneus' CAB (based on the definitions of the now-defunct Cryosphere Today). I would love to be able to redraw these regions and calculate volume, area and extent as I see fit.
If I had Wipneus' gridded programming skills and Gerontocrat's ability to doggedly concentrate on the task and produce these wonderful charts and A-Team's/Uniquorn's ability to produce amazing geographic visualizations, I would analyze the Arctic pixel by pixel to produce probabilities of being ice-covered and ice-free at different points of the year, group them in regions by similar behavior, and look at the trends for these regions on the way to a BOE. One can dream...
I expect BOE will happen sooner than my analysis will happen.

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Re: When will the Arctic Go Ice Free?
« Reply #1495 on: April 13, 2020, 06:30:02 AM »

If we look at where ice remains at the current September minimum, we see that it is primarily located in places characterized as places with deep water and far from a large heat advecting land mass such as Alaska or Siberia. These are north of 80N. The bulk of this is in the Central Basin.


.... I have long been bothered by the CAB sector near the Svalbard-FJL line, which I see as belonging to the second tier rather than the third tier. This makes the huge CAB region more noisy than it should. .......


The Arctic bathymetry chart nicely adheres to that section of the CAB that you would like to put in the second tier. That region from 80-82N sits over the shallow Barents Shelf. N of 82N, the shelf hits a clliff and descends into Nansen Basin.

https://www.ngdc.noaa.gov/mgg/bathymetry/arctic/images/ibcaoposter.pdf

Thus, the general rule seems to be that we are in a regime where the remaining ice at year end is in places that are BOTH a) relatively deep and B) far from Alaska and Siberia. The two exceptions are
the CAA (where the limited archipelago circulation offsets the shallow water) and the Greenland Sea where the current keeps a steady supply coming from the CAB.

Should someone choose to take the task on, it wouldn't be overwhelmingly difficult to factor in ocean depth in pixel mapping in coming up with a new definition of the tiers.

My hunch is that it will take longer than most people think for the third tier to melt out and result in BOE. I don't understand the process by which sufficient heat reaches N of 85N to create a BOE. AGW
is certainly moving us in that direction, but the degree of difficulty seems to be much higher for the last 4M km2 of extent.


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Re: When will the Arctic Go Ice Free?
« Reply #1496 on: April 13, 2020, 07:03:09 AM »
My hunch is that it will take longer than most people think for the third tier to melt out and result in BOE. I don't understand the process by which sufficient heat reaches N of 85N to create a BOE. AGW is certainly moving us in that direction, but the degree of difficulty seems to be much higher for the last 4M km2 of extent.

Maybe it will take longer, but a mechanism for transferring the necessary heat already exists in the form of warm water currents. As the ice retreats, the warm currents should follow the ice edge, leading to Atlantification ever further north.

As has been thrashed out, bathymetry is important, and the struggle between the ice and the halocline on the one hand and the warm ocean currents on the other turns very much in favor of the former as the bottom drops away north of 80 parallel, hence the correlation between bathymetry and ice front that is often (but not always) quite good.

But the warm surface currents keep battering the ice front - it is in the nature of warmer ocean waters to float on top, although not as strong as the tendency of the fresh water lense under the ice. But once Atlantification starts removing the fresh water lense, the surface waters should have it easier battering the ice front.

Or not. The mechanism is there (the warm ocean currents), but with support from bathymetry, perhaps the ice will hold out much longer than linear extrapolation would indicate.
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Re: When will the Arctic Go Ice Free?
« Reply #1497 on: April 13, 2020, 01:22:20 PM »
the second two graphs look at 365 day trailing average volume
...
But IFF** that linear trend continues, by 2050 85% of the ice is gone, and by 2060 the Arctic would be virtually ice-free apart from some bits and pieces in winter.

It's meaningless to extrapolate an annual average in that way.

If you do the same analysis for individual monthly data, the September ice volume would reach zero in the year 2033 whereas the April volume would reach zero in the year 2101.

Your annual average extrapolation reaches zero somewhere halfway between, in 2065.  That is because it implicitly assumes that the summer ice volume can drop below zero into negative territory.  The "negative volume" in summer would cancel out the "positive volume" in winter by 2065 in the annual average.  It's clearly meaningless.

There was a commenter called Viddaloo who did the same thing on this forum a few years ago (except that he used quadratic rather than linear extrapolations) and these problems were already pointed out back then, e.g. see here.

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Re: When will the Arctic Go Ice Free?
« Reply #1498 on: April 13, 2020, 02:00:57 PM »

.....But once Atlantification starts removing the fresh water lense.....


Perhaps you can expand on this piece. My understanding is that the fresh water is the surface layer of the Arctic because it is less dense than warmer Atlantic water because the salinity impacts density more than the temperature difference. Incoming Atlantic water does not generally displace the surface layer, it exists beneath it.

The process of removing the fresh water lens that you refer to isn't clear.

Note: Fresh water exits the Arctic all the time via Fram Strait and enters via river runoff. How would "Atlantification" accelerate the departure of fresh water?

Pmt111500

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Re: When will the Arctic Go Ice Free?
« Reply #1499 on: April 13, 2020, 02:24:12 PM »
Increased north-south winds would could should do something to the surface currents. If the weather locks down in one configuration for log enough the fresh water lense is in difficulties.

Note to the other direction: in winter the freshwater lense is likely replenished somewhat by snow falling on open water.
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