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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1250 on: June 19, 2019, 08:33:01 AM »
JAXA ANTARCTIC Sea Ice Extent : 12,367,006 km2(June 18, 2019)

Extent gains more below than above average in the last week.
2019 remains lowest in the satellite record for the 68th day this year, extent now 296 k below 2017.

- Extent gain on this day 125k, 18 k more than the average gain of 107 k on this day.
- Extent gain from minimum is 9.942 million km2, 1.075 million km2 (10%) less than the average of 11.018 million km2 by this day,
- 68.9% of average extent gain done, with 90 days to average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of last 10 years gives a max of 17.36 million km2, 0.71 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
I will only be posting occasional updates from now on unless something of note occurs.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1251 on: June 22, 2019, 11:25:50 AM »
JAXA ANTARCTIC Sea Ice Extent :  12,763,937  km2(June 21, 2019)

Extent gains suddenly increased strongly in the last 3 days .
However, 2019 remains lowest in the satellite record (for 71 days this year), extent now just 74 k below 2017 and 675k below 2018.

- Extent gain on this day 154k, 54 k more than the average gain of 100 k on this day.
- Extent gain from minimum is 10.339 million km2, 0.950 million km2 (8.4%) less than the average of 11.289 million km2 by this day,
- 70.6% of average extent gain done, with 87 days to the average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 17.48 million km2, 0.58 million km2 less than 2017 (the record low maximum year).
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1252 on: June 22, 2019, 01:01:49 PM »
The Sea Ice Predictions Network June report https://www.arcus.org/sipn/sea-ice-outlook/2019/june has a bit about the Antarctic maximum. It looks like my "heuristic" estimate for the September maximum is closest to the UK METOFFICE prediction.

Quote
Antarctic Discussion
As was the case last year, there were several submissions for Antarctic ice extent. This year, six outlooks of September mean sea-ice extent were received (compared to 12 for last year). The six forecasts span a range of 17.0–20.9 million square kilometers (Figure 18), which largely surpasses the range in the observed satellite record. This is a remarkable range compared to the Arctic submissions.

From the (small) ensemble available, it can be surmised that the prediction systems taken together will probably not outperform a climatological or a persistence-based forecast. The next set of submissions (July and August) may be telling in this regard. Caution should be exercised in interpretation of the results as the circumpolar sea-ice extent is a diagnostic with little physical relevance.

The sister project of SIPN2, the Sea Ice Prediction Network South (SIPN South, http://acecrc.org.au/sipn-south/) aims at analyzing in more detail the (summer) Antarctic sea ice forecasts, understand the regional expressions of forecast biases, and deliver information that is more tailored to end users.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1253 on: June 27, 2019, 09:23:49 AM »
JAXA ANTARCTIC Sea Ice Extent :  13,431,387 km2(June 26, 2019)

A big change in the last week.

Extent gains suddenly increasing strongly in the last week, has knocked extent off its perch in pole position. 2019 now 2nd lowest in the satellite record, 131 k above 2017 and 553k below 2018.

- Extent gain on this day 186k, 93 k more than the average gain of 93 k on this day.
- Extent gain from minimum is 11.007 million km2, 0.716 million km2 (6.1%) less than the average of 11.723 million km2 by this day,
- 73.4% of average extent gain done, with 82 days to the average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 17.70 million km2, 0.36 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1254 on: July 01, 2019, 11:40:12 AM »
JAXA ANTARCTIC Sea Ice Extent :  13,717,589 km2(June 30, 2019)

The last week started with very high extent gains and finished with - very low extent gains. 2019 is now 2nd lowest in the satellite record, 85 k above 2017 and 668 k below 2018.

- Extent gain on this day 40 k, 46 k less than the average gain of 86 k on this day.
- Extent gain from minimum is 11.293 million km2, 0.731 million km2 (6.1%) less than the average of 12.024 million km2 by this day,
- 75.5% of average extent gain done, with 78 days to the average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 17.65 million km2, 0.41 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
"Para a Causa do Povo a Luta Continua!"
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Bugalugs

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Re: Sea Ice Extent around Antarctica
« Reply #1255 on: July 02, 2019, 12:57:41 AM »
Layman's view  ;D ... looks like 2017, 2018 and 2019 mark a major shift, unless strange things happen in threes at the South Pole.


gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1256 on: July 02, 2019, 03:43:40 PM »
Layman's view  ;D ... looks like 2017, 2018 and 2019 mark a major shift, unless strange things happen in threes at the South Pole.
Reached a max in 2014, collapsed in 2016, and has stayed low. What next?
A new lower but stable state?
More loss to come?
Sea ice to recover?

Meanwhile, NASA & The US National Academy of Sciences have brought it to our attention (like we hadn't noticed?)

https://www.theguardian.com/world/2019/jul/01/precipitous-fall-in-antarctic-sea-ice-revealed
'Precipitous' fall in Antarctic sea ice since 2014 revealed
Plunge is far faster than in Arctic and may lead to more global heating, say scientists


Link to article
https://www.pnas.org/content/early/2019/06/25/1906556116
A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic

There have been papers trying to explain this big change. This paper seems to accept that the climate system, especially connections across the globe, is not fully understood.


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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1257 on: July 07, 2019, 09:10:27 AM »
JAXA ANTARCTIC Sea Ice Extent :  14,330,778 km2(July 6, 2019)

The last week a mixture of low and high extent gains. 2019 is now 2nd lowest in the satellite record, 42 k above 2017 and 577 k below 2018.

- Extent gain on this day 114 k, 14 k more than the average gain of 100 k on this day.
- Extent gain from minimum is 11.906 million km2, 0.605 million km2 (4.8%) less than the average of 12.511 million km2 by this day,
- 78.6% of average extent gain done, with 72 days to the average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 17.77 million km2, 0.29 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
"Para a Causa do Povo a Luta Continua!"
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prokaryotes

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Re: Sea Ice Extent around Antarctica
« Reply #1258 on: July 09, 2019, 12:27:33 AM »


Made this video on recent Parkinson et al. PNAS paper, feedback is welcome. Though the more extended version posted here https://climatestate.uscreen.io/programs/the-mystery-of-the-antarctic-sea-ice-puzzle goes into more details with the ozone hole, and includes a brief segment from this 2018 talk https://climatestate.uscreen.io/programs/the-circulation-of-the-antarctic-margins-in-a-changing-climate by NASA's Andy Thompson, who elaborates on grounding line - slope vortexes, eddies, models, and SAM.

The main take-away from Parkinson et al, for me is, that the Amundsen current feeds into the WAIS region, while sea-ice there also most extensively in decline.
CLIMATE STATE WEBSITE | YOUTUBE | USCREEN

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1259 on: July 14, 2019, 09:52:31 AM »
JAXA ANTARCTIC Sea Ice Extent :  15,077,869 km2(July 13, 2019)

July so far has seen a run of high extent gains. 2019 is now 2nd lowest in the satellite record, 216 k above 2017 and 364 k below 2018.

- Extent gain on this day 79 k, 11 k more than the average gain of 68 k on this day.
- Extent gain from minimum is 12.653 million km2, 0.387 million km2 (3.0%) less than the average of 13.040 million km2 by this day,
- 82.0% of average extent gain done, with 65 days to the average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 17.97 million km2, 0.09 million km2 less than 2017 (the record low maximum year).

This is a significant upwards change in extent from the end of June.
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"Para a Causa do Povo a Luta Continua!"
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1260 on: July 16, 2019, 06:03:49 AM »
JAXA ANTARCTIC Sea Ice Extent :  15,408,430 km2(July 15, 2019)

July so far has seen a run of high to extreme extent gains. 2019 is now 2nd lowest in the satellite record, 435 k above 2017 and 113 k below 2018.

- Extent gain on this day 188 k, 149 k more than the average gain of 39 k on this day.
- Extent gain from minimum is 12.984 million km2, 0.147 million km2 (1.1%) less than the average of 13.130 million km2 by this day,
- 82.4% of average extent gain done, with 63 days to the average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 18.23 million km2, 3rd lowest in the satellie record, and 0.17 million km2 greater than 2017 (the record low maximum year).

This is a significant upwards change in extent from the end of June.
______________________________________________________________________
"Para a Causa do Povo a Luta Continua!"
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Darvince

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Re: Sea Ice Extent around Antarctica
« Reply #1261 on: July 16, 2019, 03:25:03 PM »
It's 3rd now, additionally above 2002. If there is a gain of at least ~180,000 km2 for the 16th, it could become 7th.

Stephan

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Re: Sea Ice Extent around Antarctica
« Reply #1262 on: July 16, 2019, 07:19:06 PM »
If you look at Climate Reanalyzer, for weeks now the SST anomaly around the sea ice edge is below zero almost around the globe. This should help ice to grow a little faster than usual (→ higher gains than average) IMO.

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1263 on: July 20, 2019, 10:34:36 AM »
JAXA ANTARCTIC Sea Ice Extent :  15,408,430 km2(July 15, 2019)

July so far saw a run of high to extreme extent gains. And in the last 2 days crashed to an extent loss. This happens, not often, but it does happen. 2019 is now 2nd lowest in the satellite record, 290 k above 2017 and 73 k below 2018.

- Extent loss on this day 46 k, a variation of 112 k from the average gain of 66 k on this day.
- Extent gain from minimum is 13.252 million km2, 0.124 million km2 (0.9%) less than the average of 13.375 million km2 by this day,
- 83.9% of average extent gain done, with 59 days to the average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 18.25 million km2, 3rd lowest in the satellite record, and 0.19 million km2 greater than 2017 (the record low maximum year).

This is a significant upwards change in extent from the end of June.  Still a large chance of significant change - either way. ______________________________________________________________________
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1264 on: July 21, 2019, 11:08:59 AM »
JAXA ANTARCTIC Sea Ice Extent :  15,628,582 km2(July 20, 2019)

July so far saw a run of high to extreme extent gains. And in the last 3 days crashed to an extent loss for 2 days in a row. This happens, not often, but it does happen. It happens more frequently as maximum ice approaches, probably due to the violent weather** and storms that can shift large amounts of thin ice at the fringes about.

2019 is now 2nd lowest in the satellite record, just 49 k above 2017 and 187 k below 2018.

- Extent loss on this day 48 k, a variation of 123 k from the average gain of 75 k on this day.
- Extent gain from minimum is 13.204 million km2, 0.250 million km2 (1.9%) less than the average of 13.454 million km2 by this day,
- 84.4% of average extent gain done, with 58 days to the average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 18.13 million km2, 3rd lowest in the satellite record, and 0.07 million km2 greater than 2017 (the record low maximum year).

Despite the last 3 days, this is still a significant upwards change in extent from the end of June.  Still a large chance of significant change - either way. ______________________________________________________________________
** apparently weather is not a forbidden word on this thread (yet).
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1265 on: July 22, 2019, 08:18:15 AM »
JAXA ANTARCTIC Sea Ice Extent :  15,656,849 km2(July 21, 2019)

2019 is now lowest in the satellite record, just 30 k below 2017.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1266 on: July 27, 2019, 02:34:44 PM »
JAXA ANTARCTIC Sea Ice Extent :   16,064,379  km2(July 26, 2019)

In the last week massively below average extent gains (including 2 days of estent loss) followed by modestly above extent gains. It seems to happen more frequently as maximum ice extent approaches, probably due to the perpetually violent weather** and storms that can shift large amounts of thin ice at the fringes about.

2019 is now lowest in the satellite record for the 81st day this year.
Extent is , just 62 k below 2017 and 174 k below 2018.

- Extent gain on this day 64 k, a variation of 41 k from the average gain of 104 k on this day.
- Extent gain from minimum is 13.640 million km2, 0.216 million km2 (1.6%) less than the average of 13.855 million km2 by this day,
- 87.3% of average extent gain done, with 52 days to the average date of maximum (16 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 18.10 million km2, 2nd lowest in the satellite record, and 0.04 million km2 greater than 2017 (the record low maximum year).

This is still a significant upwards change in extent from the end of June.  Still a large chance of significant change - either way. ______________________________________________________________________
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1267 on: July 29, 2019, 11:55:07 AM »
Big extent increase July 28.

From late August 2016 becomes interesting.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1268 on: August 01, 2019, 08:51:56 AM »
JAXA ANTARCTIC Sea Ice Extent :   16,415,838 km2(July 31, 2019)

In the last week extent gains mainly above average.
2019 now lowest in the satellite record for the 84 days this year.
Extent is just 35 k below 2017 and 284 k below 2018.

- Extent gain on this day 27 k, a variation of 34 k from the average gain of 61 k on this day.
- Extent gain from minimum is 13.991 million km2, 0.210 million km2 (1.5%) less than the average of 14.201 million km2 by this day,
- 89.3% of average extent gain done, with 50 days to the average date of maximum (19 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 18.14 million km2, 2nd lowest in the satellite record, and 0.08 million km2 greater than 2017 (the record low maximum year).

There was a small error on the 10 year average date for the maximum - I had not adjusted the average to include 2018 and drop 2008. Hence the average date for the maximum has changed from 16 September to 19 September.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1269 on: August 06, 2019, 08:27:40 AM »
JAXA ANTARCTIC Sea Ice Extent :   16,712,919 km2(August 5, 2019)

In the last week extent gains mainly above average.
2019 now 2nd lowest in the satellite record (was lowest for 84 days this year).
Extent is 241 k above 2017 and 142 k below 2018.

- Extent gain on this day 39 k, a variation of 12 k from the average gain of 51 k on this day.
- Extent gain from minimum is 14.228 million km2, 0.190 million km2 (1.3%) less than the average of 14.478 million km2 by this day,
- 91.0% of average extent gain done, with 45 days to the average date of maximum (19 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 18.16 million km2, 2nd lowest in the satellite record, and 0.10 million km2 greater than 2017 (the record low maximum year).
"Para a Causa do Povo a Luta Continua!"
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1270 on: August 11, 2019, 10:01:27 AM »
JAXA ANTARCTIC 17,102,131 km2(August 10, 2019)

Until this day, in the last week extent gains mainly very much above average.
As a result 2019 is now 3rd lowest in the satellite record (was lowest for 84 days this year).
Extent is 284 k above 2017 and 88 k above 2018.

- Extent LOSS on this day 12 k, a variation of 57 k from the average gain of 45 k on this day.
- Extent gain from minimum is 14.677 million km2, 0.079 million km2 (0.5%) less than the average of 14.757 million km2 by this day,
- 92.6% of average extent gain done, with 40 days to the average date of maximum (19 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 18.29 million km2, 3rd lowest in the satellite record, and 0.23 million km2 greater than 2017 (the record low maximum year).
"Para a Causa do Povo a Luta Continua!"
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1271 on: August 18, 2019, 08:08:04 AM »
JAXA ANTARCTIC SEA ICE EXTENT :- 17,394,633 km2(August 17, 2019)

In the last week extent gains below average and above almost equally .
As a result 2019 is now 4th lowest in the satellite record (was lowest for 84 days this year).
Extent is 266 k above 2017, 13 k above 2018 and 55 k above 2007. (After this date 2007 very soon gained extent strongly).

- Extent gain on this day 37 k, a variation of 2 k from the average gain of 35 k on this day.
- Extent gain from minimum is 14.970 million km2, 0.048 million km2 (0.3%) less than the average of 15.018 million km2 by this day,
- 94.3% of average extent gain done, with 33 days to the average date of maximum (19 Sept).

The Perils of Projections
Remaining average freeze of the last 10 years gives a max of 18.30 million km2, 4th lowest in the satellite record (above 2017, 2018 and 2008**), 0.24 million km2 greater than 2017 (the record low maximum year).
__________________________________________
** 2008 was an outlier low maximum extent year.
In contrast, it looks likely 2019 will be the 4th year of a stabilised low Antarctic maximum of between 18 and 18.5 million km2.
« Last Edit: August 18, 2019, 10:21:55 AM by gerontocrat »
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charles_oil

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Re: Sea Ice Extent around Antarctica
« Reply #1272 on: August 18, 2019, 09:03:29 AM »
- Extent LOSS on this day 37 k, a variation of 2 k from the average gain of 35 k on this day.


Is that GAIN, 72k or loss ?


Thanks

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1273 on: August 18, 2019, 10:22:38 AM »
- Extent LOSS on this day 37 k, a variation of 2 k from the average gain of 35 k on this day.


Is that GAIN, 72k or loss ?


Thanks
Whoops. Corrected
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1274 on: August 24, 2019, 12:59:41 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 17,626,202 km2(August 23, 2019)

Things are changing - slowly but persistently

- In the last week extent gains mostly above average.
- As a result 2019 is now 6th lowest in the satellite record (was lowest for 84 days this year).
- Extent is above 2018, 2017, 2008, 2007, and 2003, and all by small amounts. See Table Ant3),
- Extent gain on this day 68 k, a variation of 29 k from the average gain of 39 k on this day,
- Extent gain from minimum is 14.201 million km2, 0.007 million km2 (0.0%) MORE than the average of 15.194 million km2 by this day,
- 95.6% of average extent gain done, with 27 days to the average date of maximum (19 Sept).

The Perils of Projections

From this date to maximum both 2003 and 2007 gained extent far above average.

Remaining average freeze of the last 10 years gives a max of 18.32 million km2, 4th lowest in the satellite record (above 2017, 2018 and 2008), 0.24 million km2 greater than 2017 (the record low maximum year).
__________________________________________
** 2008 was an outlier low maximum extent year.
In contrast, it looks likely 2019 will be the 4th year of a stabilised low Antarctic maximum of between 18 and 18.5 million km2. Or will it?

Speculation..
On another thread, there is a posting about an unusual warming event expected in early September in part of the Antarctic Stratosphere. Could this cause a change in the troposphere temperatures affecting sea ice formation or melting in the Antarctic Spring?
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Pipster

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Re: Sea Ice Extent around Antarctica
« Reply #1275 on: August 25, 2019, 04:43:23 AM »
I emailed NIWA to ask about projected effect on Antarctic ice extent from the SSW event but got a big "I don't know".
This article tasks about SSW events in the northern hemisphere and the effects on Arctic ice extent. It seems a safe bet judging from this article, that heating in the stratosphere will negatively impact Antarctic ice extent over the coming months. 
https:// journals.ametsoc.org/doi/full/10.1175/JCLI-D-17-0495.1

oren

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Re: Sea Ice Extent around Antarctica
« Reply #1276 on: August 26, 2019, 03:33:14 AM »
Welcome to the forum pipster.

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Re: Sea Ice Extent around Antarctica
« Reply #1277 on: August 27, 2019, 10:20:48 PM »
Welcome to the forum pipster.

Thank you :)

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1278 on: August 31, 2019, 12:37:05 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 17,954,213 km2(August 30, 2019)

Things are changing - slowly but persistently, moving sea ice extent from the current period of record low extents (from 2016 to 2018) back to the the early 2000's higher extents.

- In the last 2 weeks extent gains mostly above average.
- As a result 2019 is now 4th lowest in the satellite record since 2002, and 7th lowest going back as far as 1990.
- Extent is above 2018, 2017, and 2003,
- Extent gain on this day 21 k, 9 k less than the average gain of 30 k on this day,
- Extent gain from minimum is 15.529 million km2, 0.130 million km2 (0.8%) MORE than the average of 15.399 million km2 by this day,
- 96.8% of average extent gain done, with 20 days to the average date of maximum (19 Sept).

The Perils of Projections

From this date to maximum both 2003 and 2007 gained extent far above average.

Remaining average freeze of the last 10 years gives a max of 18.47 million km2, 4th lowest in the satellite record (above 2017, 2018 and 2008), 0.41 million km2 greater than 2017 (the record low maximum year).
__________________________________________

In contrast, it looks likely 2019 will be the 4th year of a stabilised low Antarctic maximum of between 18 and 18.5 million km2. Or will remaining extent gain see it drift upwards to more like the early 2000's ?

Speculation..
On another thread, there is a posting about an unusual warming event expected in early September in part of the Antarctic Stratosphere. Could this cause a change in the troposphere temperatures affecting sea ice formation or melting in the Antarctic Spring that is now almost upon us?
[/quote]
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steve s

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Re: Sea Ice Extent around Antarctica
« Reply #1279 on: September 01, 2019, 04:03:34 AM »
I follow these reports closely, so thanks Gerontocrat. But due to my ignorance I can't help wondering ...

Without an ice volume comparison, or even a concentration weighting, I do not know how to interpret the significance of extent. Are the 3 measures highly correlated? When and where do they diverge? How have their correlations changed over time? Has the mean salinity of fresh Antarctic sea ice changed in some areas differently from in other areas, perhaps leading to freezing occurring at higher temperatures?

Please educate me.

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Re: Sea Ice Extent around Antarctica
« Reply #1280 on: September 01, 2019, 01:17:19 PM »
I follow these reports closely, so thanks Gerontocrat. But due to my ignorance I can't help wondering ...

Without an ice volume comparison, or even a concentration weighting, I do not know how to interpret the significance of extent. Are the 3 measures highly correlated? When and where do they diverge? How have their correlations changed over time? Has the mean salinity of fresh Antarctic sea ice changed in some areas differently from in other areas, perhaps leading to freezing occurring at higher temperatures?

Please educate me.
You have to browse - on the ASIF and elsewhere - and follow leads and you will find out that.

Antarctica is the place on which we need to know the most and know the least.

A cold continent surrounded by ocean, and a polar vortex of wind and sea that once was assumed to more or less insulate Antarctica from climate change, and with the ozone hole perhaps more important.

- Salinity etc - above my pay grade.
- For science stuff go to AbruptSLR's postings on the thread:-  Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video) and browse and follow links if you think they might help.
- And just Google - I found this page https://www.noaa.gov/topic-tags/antarctica and some articles  might help.
Forget volume. Nearly all sea ice in Antarctica is first year ice - i.e forms and melts every year.

Extent is the measure used for historical comparisons, and until the major change in 2015-2016 sea ice extent was not considered significant. The question at the moment is whether that big reduction in sea ice extent maximum was temporary or permanent.

I will be posting data about the various ocean regions of Antarctica after the maximum. Go back in the thread to around March this year and you will see some data posted. Look for posts by Tealight on this thread.

Take your time. The subject is vast. I deliberately limit myself almost entirely to the simple measure of extent.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1281 on: September 01, 2019, 01:21:43 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 17,962,653 km2(August 31, 2019)

Nothing to add to yesterday's post of significance. So here is the data.
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steve s

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Re: Sea Ice Extent around Antarctica
« Reply #1282 on: September 03, 2019, 09:36:18 AM »
Gerontocrat, consider that extent will increase with the same surface coverage if winds lower concentration; that an earlier and deeper freeze would lead to a later melt with the same extent, other things equal; that greater rafting with thinner newer ice between the rafts would melt out in a different pattern -- likely an earlier breakup -- than the same volume evenly distributed. I eagerly follow your graphs, and appreciate observing each year's ebb and flow of extent. But extent is only extent -- one dimension.

I certainly do not mean to criticize your work, but I do want to understand the changes better and perhaps among the many knowledgeable followers of this thread there will be one or two able to offer insight. Perhaps someone watching winds or temperature anomalies closely, and seeing a correlation with a specific change in extent or concentration.

December 29th of last year I noted that the 2016 drop in sea ice "began with a pretty dramatic step function, downward, when sea ice should have been growing." In reply 702 of this thread Tigertown posted a graph showing the dramatic drop in extent. Were winds increasing concentration with no change in volume during that interval? Was there a change in the roaring forties? Or was the step due to something else? A correlation with another phenomenon might illuminate other patterns in sea ice development or it might not, but either way it would be interesting.   


gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1283 on: September 03, 2019, 02:21:04 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,091,538 km2(September 2, 2019)

Things have continued to change - persistently, currently moving sea ice extent from the current period of record low extents (from 2016 to 2018) towards the the early 2000's higher extents.

- In the last 2 weeks extent gains mostly above average.
- As a result 2019 is now 5th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2003 and 2005,
- Extent is now 29k above the record low maximum in 2017,
- Extent gain on this day 47 k, 27 k MORE than the average gain of 20 k on this day,
- Extent gain from minimum is 15.667 million km2, 0.235 million km2 (1.5%) MORE than the average of 15.432 million km2 by this day,
- 97.0% of average extent gain done, with 18 days to the average date of maximum (20 Sept).

The Perils of Projections

Remaining average freeze of the last 10 years gives a max of 18.57 million km2, 5th lowest in the satellite record, 0.51 million km2 greater than 2017 (the record low maximum year).
__________________________________________

Speculation..
On the "what's new in the Antarctic"  thread, there are postings about an unusual warming event expected in early September in part of the Antarctic Stratosphere. Could this cause a change in the troposphere temperatures affecting sea ice formation or melting in the Antarctic Spring that is now almost upon us?
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1284 on: September 07, 2019, 12:44:49 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,218,030 km2(September 6, 2019)

Until this day, things continued to change - persistently, currently moving sea ice extent from the current period of record low extents (from 2016 to 2018) towards the the early 2000's higher extents. But on this day extent dropped by 49k

- Until this day, in the last 2 weeks extent gains mostly above average.
- 2019 is now 5th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2003 and 2008,
- Extent LOSS on this day 49 k, 75 k different from the average gain of 20 k on this day,
- Extent gain from minimum is 15.793 million km2, 0.227 million km2 (1.5%) MORE than the average of 15.566 million km2 by this day,
- 97.8% of average extent gain done, with 14 days to the average date of maximum (20 Sept).

The Perils of Projections

Remaining average freeze of the last 10 years gives a max of 18.57 million km2, 5th lowest in the satellite record, 0.51 million km2 greater than 2017 (the record low maximum year).
__________________________________________
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1285 on: September 07, 2019, 12:55:52 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,218,030 km2(September 6, 2019)|- MORE STUFF


I attach the plume of possible outcomes from the previous 10 years remaining extent gains and losses

Note that the average is well below the average quoted on table JAXA-Ant1 in the previous post.
This is because the average in the attached graph includes large extent losses in some years in the next few days. The average outcome in the table only looks t years with extent gains from now.

I still don't know whether to include extent losses from now in the table. But the end of season is so wobbly that any projections really only show the range pf possibilities, which are so great as regards recent years in the Antarctic.

I also attach a table of the final result if extent gain stopped at the current maximum of 5th September. 2019 would be 4th lowest - but note this is already higher (just) than the maximum of 2008.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1286 on: September 12, 2019, 08:38:25 AM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,149,860 km2(September 11, 2019)

Until about a week ago, sea ice extent was persistently increasing from the current period of record low extents (from 2016 to 2018) towards the the early 2000's higher extents. But since the 5th September extent has dropped from 18.27 to 18.15 million km2. Temporary?   

- In the last week overall extent has dropped, not increased,
- 2019 is now 6th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2016, 2008 and 2003,
- Extent LOSS on this day 10 k, 28 k different from the average gain of 18 k on this day,
- Extent gain from minimum is 15.725 million km2, 0.091 million km2 (0.6%) MORE than the average of 15.634 million km2 by this day,
- 98.4% of average extent gain done, with 9 days to the average date of maximum (20 Sept).

The Perils of Projections

Remaining average freeze of the last 10 years gives a max of 18.40 million km2, 5th lowest in the satellite record, 0.34 million km2 greater than 2017 (the record low maximum year).
__________________________________________
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1287 on: September 15, 2019, 11:01:25 AM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,149,860 km2(September 11, 2019)

Until about a week ago, sea ice extent was persistently increasing from the current period of record low extents (from 2016 to 2018) towards the the early 2000's higher extents. But since the 5th September extent dropped from 18.27 to 18.15 million km2. And now is back on the rise. 

- 2019 is now 6th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2016, 2015 & 2008,
- Extent increase on this day 22 k, 27 k different from the average loss of 5 k on this day,
- Extent gain from minimum is 15.769 million km2, 0.111 million km2 (0.7%) MORE than the average of 15.658 million km2 by this day,
- 98.8% of average extent gain done, with 6 days to the average date of maximum (20 Sept).

The Perils of Projections

Remaining average freeze of the last 10 years gives a max of 18.39 million km2, 5th lowest in the satellite record, 0.33 million km2 greater than 2017 (the record low maximum year).
__________________________________________
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1288 on: September 19, 2019, 04:21:00 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,212,548 km2(September 18, 2019)

Extent on this day is 74k below the current maximum on 16 Sept 

- 2019 is now 6th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2016, 2015 & 2008,
- Extent decrease on this day 53 k, 66 k different from the average gain of 13 k on this day,
- Extent gain from minimum is 15.788 million km2, 0.118 million km2 (0.7%) MORE than the average of 15.670 million km2 by this day,
- 99.2% of average extent gain done, with just 2 days to the average date of maximum (20 Sept).

The Perils of Projections

Remaining average freeze of the last 10 years gives a max of 18.35 million km2, 5th lowest in the satellite record, 0.28 million km2 greater than 2017 (the record low maximum year).

It is possible the maximum has passed.
__________________________________________
NOTE: On graph Ant2 2017 daily change has been replaced with 2016, which from about Oct 5 started its spectacular daily extent losses.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1289 on: September 20, 2019, 11:46:56 AM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,139,287 km2(September 19, 2019)

Extent on this day is 137k below the current maximum on 16 Sept 

- 2019 is now 5th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2016, & 2008,
- Extent decrease on this day 73 k, 69 k different from the average gloss of 4 k on this day,

The Perils of Projections

It is very possible the maximum has passed.
__________________________________________
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1290 on: September 25, 2019, 09:07:44 AM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,262,156 km2(September 24, 2019)

Extent on this day is 15k below the current maximum on 16 Sept 

- 2019 is now 6th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2016, 2015 & 2008,
- Extent increase on this day 73 k, 90 k different from the average loss of 34 k on this day,

The Perils of Projections

Only 2 years had a date of maximum later than this day. But........
__________________________________________
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Re: Sea Ice Extent around Antarctica
« Reply #1291 on: September 25, 2019, 10:07:45 PM »

- Extent increase on this day 73 k, 90 k different from the average loss of 34 k on this day,


A high increase (instead of a slight decrease) is needed to make up for the low Arctic sea ice extent to prevent global sea ice extent to become lowest again since records began.

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1292 on: September 29, 2019, 12:37:37 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,309,834 km2(September 28, 2019)

Extent on this day is 38k below the current maximum on 27 Sept 

- 2019 is now 5th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2016, & 2008,
- Extent decrease on this day 38 k, 45 k different from the average gain of 7 k on this day,

The Perils of Projections

Only 2 years had a date of maximum later than the 27th Sept. So given a nearly 40k drop on this day maybe 18.35 million km2 will be the maximum.  But........
__________________________________________
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1293 on: October 01, 2019, 01:32:48 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,324,387 km2(September 30, 2019)

Extent on this day is 23k below the current maximum on 27 Sept 

- 2019 is now 5th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2016, & 2008,
- Extent increase on this day 12 k, 17 k different from the average loss of 5 k on this day,

The Perils of Projections

Only 2 years had a date of maximum later than the 30th Sept. So maybe 18.35 million km2 will be the maximum.  None show a projected 2019 maximum greater than the 27th Sept 2019 value. But........
__________________________________________
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Re: Sea Ice Extent around Antarctica
« Reply #1294 on: October 02, 2019, 06:02:03 AM »
For Oct. 1st, looks like JAXA is showing a close to 50k loss in sea ice around Antarctica. Do you think we have our maximum for the season and now extent will only decline? (It's about that time) It will be interesting to watch the global extent as well to see how the two sie's total up day after day.

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Re: Sea Ice Extent around Antarctica
« Reply #1295 on: October 02, 2019, 08:40:16 AM »
For Oct. 1st, looks like JAXA is showing a close to 50k loss in sea ice around Antarctica. Do you think we have our maximum for the season and now extent will only decline? (It's about that time) It will be interesting to watch the global extent as well to see how the two sie's total up day after day.
I analysed the individual years and extracted those years, in which a significant increase in Antarctic Sea Ice Extent occurred after Oct 1 (sorted from highest to lowest increase):
2017  0,27 M km²
1992  0,23 M km²
2002  0,20 M km²
2008  0,19 M km²
2010  0,13 M km²
1997  0,13 M km²
1989  0,12 M km²
2006  0,08 M km²
1998  0,07 M km²
1988  0,07 M km²
2003  0,06 M km²
1993  0,03 M km²
With a needed increase of 0,09 M km² to reach the annual maximum in 2019 only 7 out of 40 years made it at this time of the year, the probability for this event is 17,5%.

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1296 on: October 02, 2019, 09:52:29 AM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,270,937 km2(October 1, 2019)

Extent on this day is 77k below the current maximum on 27 Sept 

- 2019 is still 5th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2016, & 2008,
- Extent decrease on this day 53 k, 44 k different from the average loss (last 10 years) of 9 k on this day,

The Perils of Projections

Only 1 year in the last 10 had a date of maximum later than the 30th Sept. I am plumping for 27th Sept, 18.35 million km2 as the 2019 maximum.. But........ (see post above)
__________________________________________
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1297 on: October 03, 2019, 02:43:04 PM »
JAXA ANTARCTIC SEA ICE EXTENT :- 18,226,222 km2(October 2, 2019)

Extent on this day is 121k below the current maximum on 27 Sept. 
I think we are pass the maximum. So the first table attached assumes we are in the melting season down South.


- 2019 is still 5th lowest in the satellite record since 2002,
- Extent is above 2018, 2017, 2016, & 2008,
- Extent decrease on this day 45 k, 30 k more than the average extent loss (last 10 years) of 15 k on this day,
- Extent loss to date 0.12 million km2, 0.14 million (58%) less than the 10 year average of 0.26 million km2 by this day. This is due mostly to the relatively late day of the maximum.
- 1.6% of the season done, with on average 141 days to the average minimum date of 20 Feb.

The Perils of Projections

Average melt from this date would produce a minimum of 2.41 million km2, 5th lowest since 2002.
__________________________________________
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Re: Sea Ice Extent around Antarctica
« Reply #1298 on: October 04, 2019, 07:25:20 AM »
Only 2 years had a date of maximum later than the 30th Sept. So maybe 18.35 million km2 will be the maximum. 
I analysed again the JAXA extent of all years. 2019 needs an increase of more than 0.13 M km² to achieve a new maximum. Out of the 40 years of data only three years showed an increase of above 0.13 M km² after Oct 3:
2017 + 0.23 M km²
1992 + 0.20 M km²
2002 + 0.16 M km²
From this a probability of 7.5 % for a maximum higher than 18.35 M km² can be estimated. So gerontocrat should be correct. :)

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Re: Sea Ice Extent around Antarctica
« Reply #1299 on: October 06, 2019, 11:25:30 AM »
For Oct 05 still three years showed increases after this date that are higher than needed to achieve a new maximum for this year:
1992 + 0.15 M km²
2008 + 0.18 M km²*
2007 + 0.24 M km²*
* later increases {from Oct 10-14 (2008), Oct 12-16 (2007)}
So the probability that Sep 27 had the annual maximum is still 92.5%.