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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 157942 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?
"Para a Causa do Povo a Luta Continua!"
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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
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     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 »
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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)


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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.


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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)

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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 »