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When will we next see a new lowest 365 day trailing average extent?

2019
0 (0%)
Within the first three months of 2020
10 (62.5%)
Within months 4 to 6 of 2020
2 (12.5%)
Later in 2020
2 (12.5%)
2021
0 (0%)
2022 or later
2 (12.5%)

Total Members Voted: 14

Voting closed: September 26, 2019, 11:37:24 AM

Author Topic: 365 day average extent poll  (Read 5068 times)

Paddy

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365 day average extent poll
« on: September 12, 2019, 11:37:24 AM »
Based on Gerontocrat's 365 day Arctic sea ice trailing average extent graphs. When would you next expect to see a new record low 365 day trailing average?

Currently the average is about 160k above the record in 2016 (eyeball estimate from said graph, so please take with a pinch of salt).

EDIT: As pointed out by Gerontocrat, please note that we're talking about JAXA extent here.
« Last Edit: September 12, 2019, 05:01:04 PM by Paddy »

blumenkraft

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Re: 365 day average extent poll
« Reply #1 on: September 12, 2019, 11:42:33 AM »
Good poll!

I went with early 2020.

crandles

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Re: 365 day average extent poll
« Reply #2 on: September 12, 2019, 12:33:47 PM »
2019 below 2018 by 460k so if this gap maintained, average declines at a little over 1k per day. This isn't enough to do it in 2019. Also lines tend to be spread out most at minimum, group together much more in November and 2018 stayed rather low into early October.

So I have to conclude 2019 is looking rather unlikely.

Early 2020 seems plausible and is my guess but little chance of earlier and much more chance of being later, possibly quite a bit later.

Paddy

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Re: 365 day average extent poll
« Reply #3 on: September 12, 2019, 01:40:49 PM »
I went for "within the first 3 months of 2020", since we had a long period at or near record minimum between the end of March and August this year, which might well contribute to an overall average 365 day minimum if extent stays pretty low for the next 6 months or so; but from late October last year to March of this year the extent was relatively high, so we'd need much of that period to no longer be part of the trailing average to make a new record. 

Time will tell, though.

gerontocrat

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Re: 365 day average extent poll
« Reply #4 on: September 12, 2019, 02:29:45 PM »
Based on Gerontocrat's 365 day Arctic sea ice trailing average extent graphs. When would you next expect to see a new record low 365 day trailing average?

Currently the average is about 160k above the record in 2016 (eyeball estimate from said graph, so please take with a pinch of salt).
Thanks, Paddy (maybe)

Need to emphasis it is JAXA** Extent.

Here is a table of the current position I was using for casual use by myself.

As noted above, it all depends on how quickly 2019 re-freezes compared with 2018.

_______________________________________________
**I have similar 365 day graphs for NSIDC Area & Extent - area especially tells a somewhat different story.

I will post them after today's NSIDC data has been swallowed by my machine.
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gerontocrat

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Re: 365 day average extent poll
« Reply #5 on: September 12, 2019, 04:25:23 PM »
The NSIDC Extent and AREA graphs & tables attached.

NSIDC 365 day Extent follows JAXA Extent trends very closely, the NSIDC extent always a bit abve JXA extent.

NSIDC 365 day Area is much further behind the record minimum than extent, and the daily area difference with 218 is diminishing fast, slowing the daily drop in 365 day area.

This is likely to be replicated in the extent data, simply because usually the winter extents get much closer together.
« Last Edit: September 12, 2019, 04:42:12 PM by gerontocrat »
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Stephan

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Re: 365 day average extent poll
« Reply #6 on: September 12, 2019, 08:34:09 PM »
I do not see a 365-trailing average below the 2016 minimum in 2019. But it is likely to happen somewhen between Feb-Mar 2020, as already indicated by gerontocrat some weeks ago. Unless a very rapid and sustaining refreeze will occur Nov-Dec 2019 I see no other "right" bin than Jan-March 2020.
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gerontocrat

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Re: 365 day average extent poll
« Reply #7 on: October 15, 2019, 09:04:50 PM »
Things have changed.

The difference in JAXA Extent 2019 from 2018 reduced from 545k on the 14 September to just 243k on 2nd October. This pushed the date of a straight line projection of a new 365 day average record low from early January 2020 to early May 2020.

But since that date the very low extent 2019 extent gains has increased the difference with 2018 to 597k by the 14th October. So the date of a new record low is back to early January.

There is 136 k to go to a new record 365 day low, (9,683,735 km2), with the daily change on 14th October at 1,589 k.

Outlook- from this date 2018 daily gain was fairly high to very high in the next month.
IFF (if & only if) 2019 extent gains are generally at or below average, we could see a record 365 day average low late in this year.

Data table & graphs attached
_________________________________________
ps: If what is happening with extent this month had happened last month - there would have been many headlines
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Paddy

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Re: 365 day average extent poll
« Reply #8 on: October 19, 2019, 07:13:57 PM »
.
IF (if & only if) 2019 extent gains are generally at or below average, we could see a record 365 day average low late in this year.

That would be a pretty shocking outcome.

gerontocrat

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Re: 365 day average extent poll
« Reply #9 on: October 21, 2019, 12:14:10 PM »
A new record low 365 day average extent in 2019 (JAXA Extent data as at 20th October 2019)

On the 20th October 2018 extent is 510 k greater than 2019.

There is 127 k to go to a new record 365 day low, (9,683,735 km2), with the daily reduction in the 365 day average on 20th October at 1,400 k. So the date of a new record low is back to late January.

But if you look at the plume of daily gains from now to end November (attached), you will see that 2018 gains were far above average, indeed the highest in the last 10 years.

IFF (if & only if) 2019 extent gains are generally at average, this will increase the difference between 2018 and 2019 extent substantially, which would increase the daily reduction in the 365 day average substantially. Just maybe we could see a record 365 day average low very late in this year. However, there are only 72 days to 31st December.

Data table & graphs attached
_________________________________________
ps: If what is happening with extent this month had happened last month - there would have been many headlines
[/quote]
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gerontocrat

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Re: 365 day average extent poll
« Reply #10 on: October 28, 2019, 12:47:11 PM »
A new record low 365 day average extent in 2019 ?
(JAXA Extent data as at 27th October 2019)


On the 27th October 2018 extent is 556 k greater than 2019.

There is 116 k to go to a new record 365 day low, (9,683,735 km2), with the daily reduction in the 365 day average on 27th October at  just over 1,400 k. So the date of a new record low is currently circa mid January.

But if you look at the plume of daily gains from now to mid Decvember (attached), you will see that 2018 gains were far above average, indeed for much of the time the highest in the last 10 years. On the other hand, recent Arctic extent gains have been extremely high.

IFF (if & only if) 2019 extent gains are generally at average, this will increase the difference between 2018 and 2019 extent substantially, which would increase the daily reduction in the 365 day average substantially. Just maybe we could see a record 365 day average low very late in this year. However, there are only 65 days to 31st December.

On the other hand, if extent gains stay high and above those in 2018, one could see a new record low delayed or even put out of reach once 2019 extent is greater than 2018.

I still plump for an early 2020 record low - (Jan to April)

Data table & graphs attached
_________________________________________
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gerontocrat

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Re: 365 day average extent poll
« Reply #11 on: November 03, 2019, 01:41:12 PM »
A new record low 365 day average extent in 2019 looking much less likely
First 3 months in 2020 seems a more likely time-frame.

JAXA Extent data as at 2nd November 2019


On the 2nd November 2018 extent is a (reduced) 418 k greater than 2019.

There is 110 k to go to a new record 365 day low, (9,683,735 km2), with the daily reduction in the 365 day average on 2 November at  just under 1,150 k. So the date of a new record low is currently early February.

But if you look at the plume of 2018 daily gains for the rest  December (attached), you will see that 2018 gains were above average. On the other hand, recent Arctic extent gains have been extremely high, though starting to moderate.

IFF (if & only if) 2019 extent gains are generally at average, this will increase the difference between 2018 and 2019 extent substantially, which would increase the daily reduction in the 365 day average substantially. Just maybe we could see a record 365 day average low very late in this year. However, there are only 59 days to 31st December.

On the other hand, if extent gains stay high and above those in 2018, one could see a new record low delayed or even put out of reach once 2019 extent is greater than 2018.

I still plump for an early 2020 record low - (Jan to March)

Data table & graphs attached
_________________________________________
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gerontocrat

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Re: 365 day average extent poll
« Reply #12 on: November 12, 2019, 07:15:45 AM »
A new record low 365 day average extent in 2019 looking much less likely
First 3 months in 2020 seems a more likely time-frame.

JAXA Extent data as at 11 November 2019


On the 2nd November 2018 extent is a (slightly reduced) 393 k greater than 2019.

There is 100 k to go to a new record 365 day low, (9,683,735 km2), with the daily reduction in the 365 day average on 2 November at  just under 1,100 k. So the date of a new record low is currently early February.

But if you look at the plume of 2018 daily gains (attached) for the rest of November, you will see that 2018 gains were above average. In December, 2018 gains were below average.

There are only 50 days to 31st December. What will 2019 extent gains be?

I still plump for an early 2020 record low - (Jan to March)

Data table & graphs attached
_________________________________________
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gerontocrat

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Re: 365 day average extent poll
« Reply #13 on: November 17, 2019, 12:17:23 PM »
A new record low 365 day average extent in 2019 looking very unlikely
First 3 months in 2020 seems a more likely time-frame.

JAXA Arctic Sea Ice Extent data as at 16 November 2019


On the 16th November 2018 extent is 443 k greater than 2019.

There is 95 k to go to a new record 365 day low, (9,683,735 km2), with the daily reduction in the 365 day average on 16 November at  just over 1,200 km2. So the date of a new record low is currently February 2020.

But if you look at the plume of 2018 daily gains (attached) for the rest of November, you will see that 2018 gains were above average. In December, 2018 gains were below average.

There are only 45 days to 31st December. What will 2019 extent gains be?

I still plump for an early 2020 record low - (Jan to March)

Data table & graphs attached
_________________________________________
« Last Edit: November 17, 2019, 06:13:01 PM by gerontocrat »
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Phil.

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Re: 365 day average extent poll
« Reply #14 on: November 17, 2019, 03:22:14 PM »
There is 95 k to go to a new record 365 day low, (9,683,735 km2), with the daily reduction in the 365 day average on 16 November at  just over 1,200 k. So the date of a new record low is currently February 2020.

Should be 1,200 i.e. not k.

gerontocrat

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Re: 365 day average extent poll
« Reply #15 on: November 25, 2019, 12:15:23 PM »
A new record low 365 day average extent in 2019 is highly unlikely to impossible
First 3 months in 2020 seems a more likely time-frame.

JAXA Arctic Sea Ice Extent data as at 24 November 2019


On the 24th November 2018 extent is 647 k greater than 2019.

There is 82 k to go to a new record 365 day low, (9,683,735 km2), with the daily reduction in the 365 day average on 16 November at  just over 1,750 km2. So the date of a new record low is currently January 2020.

But if you look at the plume of 2018 daily gains (attached) for the rest of the year, you will see that 2018 gains are mostly below average from now to the end of the year. So if 2019 extent gains are at average or above, the difference in extent between 2019 and 2018 could quickly reduce. Also, in general, variations in extent between years reduce as winter progresses. This will reduce the daily reduction in the 365 daily average and thus lengthen the time to reach a record low - or even prevent that record low from happening.

There are only 37 days to 31st December. What will 2019 extent gains be?

I still plump for an early 2020 record low - (Jan to March)

Data table & graphs attached
_________________________________________
« Last Edit: November 25, 2019, 12:28:54 PM by gerontocrat »
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binntho

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Re: 365 day average extent poll
« Reply #16 on: November 25, 2019, 01:02:36 PM »
Gerontocrat, your graph starts in 1990 as far as I can see. Is there any reason for that? A longer period would be interesting.
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gerontocrat

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Re: 365 day average extent poll
« Reply #17 on: November 28, 2019, 12:43:56 PM »
Gerontocrat, your graph starts in 1990 as far as I can see. Is there any reason for that? A longer period would be interesting.
JAXA extent data in the earlier years was posted into their tables only on each 2nd day.There are also many gaps of several days. So average 365 day data is not a simple calculation. I am gradually filling in these gaps with interpolations but then there will always be a caveat in the results. It is also a pain in the arse getting several extra thousand lines of data into the averages sheet even though I use a nice little algorithm  to do it. Patiencia.

Meanwhile......
Here are the graphs & table again.

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gerontocrat

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Re: 365 day average extent poll
« Reply #18 on: December 01, 2019, 02:16:55 PM »
A new record low 365 day average extent in 2019 is in the range of highly unlikely to impossible
First 3 months in 2020 or even later seems a more likely time-frame.


JAXA Arctic Sea Ice Extent data as at 30 November 2019

There is 72 k to go to a new record 365 day low, (9,683,735 km2), with the daily reduction in the 365 day average down to just under 1,400 km2. So the date of a new record low is currently late January 2020.

On the 30th November 2019 the extent difference with 2018 has reduced to 499 k less  than 2018. The effect is a continuous reduction in the daily loss in the 365 day average, which in turn made the date for a new record low 365-day-average later. (See table attached).

And if you look at the plume of 2018 daily gains (attached) for the rest of the year, you will see that 2018 gains are mostly below average from now to the end of the year. So if 2019 extent gains are at average or above, the difference in extent between 2019 and 2018 could quickly reduce. Also, in general, variations in extent between years reduce as winter progresses. This will reduce the daily reduction in the 365 daily average and thus lengthen the time to reach a record low - or even prevent that record low from happening.

I still plump for an early 2020 record low - (Jan to March), but have no scientific basis for that guess

Data table & graphs attached
_________________________________________
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gerontocrat

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Re: 365 day average extent poll
« Reply #19 on: December 09, 2019, 08:15:03 AM »
5 days of extreme sea ice extent gains has put the cat amongst the pigeons.
A new record low 365 day average extent in 2019 is in the range of impossible to infinitely impossible

A week ago I wrote....
 
Quote
So if 2019 extent gains are at average or above, the difference in extent between 2019 and 2018 could quickly reduce. Also, in general, variations in extent between years reduce as winter progresses. This will reduce the daily reduction in the 365 daily average and thus lengthen the time to reach a record low - or even prevent that record low from happening.
And on the 7th December 2019 extent became greater than 2018 - so the date for a new record low is currently The 12th of Never and that's a long, long time.

So what will happen from now? Will 2019 extent stay above 2018 or will extent gains from now become below average?

In defiance of probability I still plump for an early 2020 record low - (Jan to March), but have no scientific basis whatsoever for that guess

Data table & graphs attached
_________________________________________
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gerontocrat

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Re: 365 day average extent poll
« Reply #20 on: December 15, 2019, 07:06:41 PM »
As at 14 December 2019 reductions in the 365 day average have stalled.
A new record low 365 day average extent in 2019 is in the range of impossible to infinitely impossible

2 weeks ago I wrote....
 
Quote
So if 2019 extent gains are at average or above, the difference in extent between 2019 and 2018 could quickly reduce. Also, in general, variations in extent between years reduce as winter progresses. This will reduce the daily reduction in the 365 daily average and thus lengthen the time to reach a record low - or even prevent that record low from happening.
And on the 7th December 2019 extent became greater than 2018 - so the date for a new record low is currently The 12th of Never and that's a long, long time.

So what will happen from now? Will 2019 extent stay above 2018 or will extent gains from now become below average?

In defiance of probability I still plump for an early 2020 record low - (Jan to March), but have no scientific basis whatsoever for that guess

Data table & graphs attached
_________________________________________
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gerontocrat

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Re: 365 day average extent poll
« Reply #21 on: December 29, 2019, 10:21:25 AM »
As at 28 December 2019 reductions in the 365 day average have stalled and reversed to increases. A new record low 365 day average extent in 2019 is in the range of impossible to infinitely impossible

2019 daily extent gains have been well above 2018 for most of December, so 2019 sea ice extent is well above 2018. The date for a new record low is currently "The 12th of Never and that's a long, long time".

So what will happen from now? In the New Year, if 2020 daily extent gains are at average, 2020 extent will fairly rapidly become lower than 2019 extent, and thus progress to a new record low 365 day trailing average. However, by late March 2019 started its rapid extent losses towards a 2nd lowest extent minimum.

Logic suggests that a new record low could happen by late March 2020, but after that would require very strong early melt even greater than that of 2019

Data table & graphs attached
_________________________________________
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gerontocrat

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Re: 365 day average extent poll
« Reply #22 on: January 04, 2020, 12:03:09 PM »
As at 3 January 2020

i]As reductions in the 365 day average stalled and reversed to increases a new record low 365 day average extent in 2019 did not happen[/i]

The date for a new record low is currently "The 12th of Never and that's a long, long time". However, recent low extent gains means that 2020 extent is now only 3 k above 2019.

So what will happen from now?  2020 daily extent gains have to be below average for the 365 day average to start falling again, and that is in the lap of the weather gods.

Data table & graphs attached
_________________________________________
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Paddy

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Re: 365 day average extent poll
« Reply #23 on: January 19, 2020, 07:40:49 AM »
I'm going to call it - the majority of us, myself included, were probably wrong. I think there's too much ground to make up in the next two months with recent gains.

jdallen

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Re: 365 day average extent poll
« Reply #24 on: January 23, 2020, 12:07:01 AM »
I'm going to call it - the majority of us, myself included, were probably wrong. I think there's too much ground to make up in the next two months with recent gains.
Now the actual fun starts - dissecting why, and what additional factors we should be examining in making our predictions.
This space for Rent.

gerontocrat

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Re: 365 day average extent poll
« Reply #25 on: January 27, 2020, 01:56:19 PM »
As at 26 January 2020

Sea ice extent has continued its strong recovery and is well above last year.

2019 was second lowest extent at minimum. 2020 extent loss would have to be huuuge to get below 2019.

Therefore the probability must be that in 2020 the 365 day average will increase, not decrease.

The date for a new record low is currently "The 12th of Never and that's a long, long time". ________________________________________________________
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Re: 365 day average extent poll
« Reply #26 on: January 28, 2020, 10:33:56 PM »
As at 26 January 2020

2019 was second lowest extent at minimum. 2020 extent loss would have to be huuuge to get below 2019.


doesn't that depend on this year's sea-ice maximum as well or solely even ?

i mean who says that extend growth doesn't end prematurely this season ?

peripheries have been and still are very warm as compared to other years that will have an impact on ocean temps and snow cover as well as ice thickness and that again could well make this freezing season end surprisingly early, of course, as always, depending on the wether in a bout a months time. +/- 2 weeks.

just something to consider, i have no specific opinion about this because it has shown to be in vain to try to predict what will be the situation in 8 months from now.

Paddy

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Re: 365 day average extent poll
« Reply #27 on: July 17, 2020, 06:55:16 AM »
How is this metric looking at present, gerontocrat? Seems like the last six months will have been very up and down.

oren

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Re: 365 day average extent poll
« Reply #28 on: July 17, 2020, 07:08:13 AM »
I think that to get a new record low in 365-day extent will require a poor refreeze season (as we had in 2016/17). It will not be enough to have a low Sep minimum, as 2020 was rather high during winter, though I haven't run the numbers to back this up.

Paddy

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Re: 365 day average extent poll
« Reply #29 on: July 17, 2020, 10:02:15 AM »
I think that to get a new record low in 365-day extent will require a poor refreeze season (as we had in 2016/17). It will not be enough to have a low Sep minimum, as 2020 was rather high during winter, though I haven't run the numbers to back this up.

You're probably right.  Right now, for each day that extent stays 600k km2 lower than the same date in 2019, the 365 day average will be dropping by over 1600 km2, and 2020 has been somewhat below 2019 since late May.  However, the 365 day average would have been climbing slowly from January to May, when 2020 was either tied with 2019 or above it, so we won't be down to the mini-trough in annual average in December 2019 yet, never mind getting anywhere close to threatening the record.

oren

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Re: 365 day average extent poll
« Reply #30 on: July 17, 2020, 10:12:58 AM »
It occurs to me Gero did an update of this recently in the data thread.

JAXA Sea Ice Extent - 365 Day Averages

Around this time last year it looked as if 2019 extent would be low enough to make a new record low 365 day trailing average extent. But came late autumn and winter 2019-20 and extent rebounded.

So here we are again, 2020 extent so far below 2019 extent as to possibly make a new record 365 day low later this year. It's all about whether 2020 extent will stay below 2019 extent and by how much.

Extent on this day is already 113k below the 1980's average with about 60 days to minimum. The table attached shows extent must reduce by 564k before it is below the highest minimum in the current century.




gerontocrat

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Re: 365 day average extent poll
« Reply #31 on: July 17, 2020, 11:55:11 AM »
I think that to get a new record low in 365-day extent will require a poor refreeze season (as we had in 2016/17). It will not be enough to have a low Sep minimum, as 2020 was rather high during winter, though I haven't run the numbers to back this up.
Not running the numbers was a mistake...

IFF 2020 extent continues below 2019 by the same amount as on the 16th July, the new record low would occur on the 29th September 2020.

Also to remember is that 2019 refreeze, once it got going (late) was really fast and ended up with a maximum of 10th lowest in the satellite record.. As long as extent is below that of a year ago the 365 day average will continue to decline.

So I reckon there is a good chance of a new record low in 2020 and may even decline further through the 2020-2021 winter.
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Re: 365 day average extent poll
« Reply #32 on: July 18, 2020, 04:53:24 PM »
Quote from: gerontocrat
IFF 2020 extent continues below 2019 by the same amount as on the 16th July, the new record low would occur on the 29th September 2020.
[/quote

Great analysis and figures as always, even if this does seem like a pretty big IF.

I'd personally reckon a new 365-day low may be most likely in early 2021, now (when 2020 ice cover was high). But obviously there's a lot that can change between now and then.

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Re: 365 day average extent poll
« Reply #33 on: July 21, 2020, 12:02:50 PM »
JAXA Arctic Sea Ice Extent - 365 day trailing Average
Data as 20 July


The current high daily extent losses maintain the possibility of a record 365-day low in September.
For a record low in 2020, the average daily reduction has to be 709 km2, i.e. 2020 extent needs to be on average at least 259 k below 2019 extent.

On this day, the 20th July, 2020 is 642k less than 2019. So there is currently considerable leeway for a record low this year. But........
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Re: 365 day average extent poll
« Reply #34 on: July 30, 2020, 01:55:15 PM »
JAXA Arctic Sea Ice Extent - 365 day trailing Average
Data as 20 July


The current high daily extent losses maintain the possibility of a record 365-day low in September.
For a record low in 2020, the average daily reduction has to be 709 km2, i.e. 2020 extent needs to be on average at least 259 k below 2019 extent.

On this day, the 20th July, 2020 is 642k less than 2019. So there is currently considerable leeway for a record low this year. But........

With the gap between 2019 and 2020 having shrunk to just 245k, I suppose this looks a tad more touch and go now... although of course we're getting to the point in the year when 2019's own sea ice loss slowed down.  Everything's still to play for.

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Re: 365 day average extent poll
« Reply #35 on: August 01, 2020, 11:29:50 AM »
One week's stall in daily extent losses has reduced the 365 day daily losses. At the current rate it would be Feb 2021.

I make no predictions, whereupon I make one. This year could end up a washout or havoc could be unleashed on the ice, or it could be just average from now on..
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Re: 365 day average extent poll
« Reply #36 on: September 02, 2020, 08:46:42 AM »
Suddenly there is a chance of a new record minimum 365 day average this year, except for one thing.

Last year, 2019 stunned me in October. The refreeze was so slow in happening that the 2019 October Monthly average was 700k below the linear trend, and 50k bnelow 2012, i.e. the record low October monthly minimum.

Maybe 2020 will match or come close to that low refreeze. If not, no record low 365 day  minimum this year.

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Re: 365 day average extent poll
« Reply #37 on: September 10, 2020, 10:44:14 AM »
In the last week the chance of a new record minimum 365 day average this year has increased, although October may still delay it again..

Last year the refreeze was so slow in happening that the 2019 October Monthly average was 700k below the linear trend, and 50k below 2012, i.e. the record low October monthly minimum.

If 2020 will match or come close to that slow refreeze, a new 365 daty average low is likely. If not, no record low 365 day minimum this year. (I attach the October monthly average graph, with the 2020 value assuming average extent gains.)
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Re: 365 day average extent poll
« Reply #38 on: September 11, 2020, 07:53:35 AM »
Should we repeat the original poll, but with new bins, maybe? Although we'd probably be guessing mainly about the October refreeze question if we did... and also about whether we'll repeat the relatively high Jan to March extents seen these last two years.

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Re: 365 day average extent poll
« Reply #39 on: September 11, 2020, 07:23:42 PM »
maybe a rotating pole about what the average will be in 3 months?

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Re: 365 day average extent poll
« Reply #40 on: September 12, 2020, 03:37:39 AM »
Perhaps just a sweepstake in this thread on month and year? In which case, I pick January 2021.

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Re: 365 day average extent poll
« Reply #41 on: September 12, 2020, 07:41:54 AM »
We need a poll about poll. :)

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Re: 365 day average extent poll
« Reply #42 on: September 12, 2020, 08:50:53 PM »
Here is a bit of JAXA & DMI info on the subject.

The Plume shows that if 2020 freezes at an average rate then it won't take long for 2020 extent to exceed 2019 extent, simply because freeze was delayed a month in 2019.

Indeed the October 2019 monthly average was a record low - lower than 2012 by 150k and 690k below the trend value. But towards the end of October 2019 played catch up and in November and December extent gain was at or above average.  (Monthly graph attached)

So if 2020 is still below 2019 extent at the end of October the bet is still on for a 2020 record low 365 day average.

What about prospects for the October to December freeze - I attach two Arctic Ocean SST anomaly images - Sep 20 2019 and Sep 11 2020.
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Re: 365 day average extent poll
« Reply #43 on: September 12, 2020, 09:03:28 PM »
And here is the current situation.....

but the dog doesn't give a damn.
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Re: 365 day average extent poll
« Reply #44 on: September 18, 2020, 10:41:57 AM »
The expected(?) slow refreeze became a fast refreeze. At this rate a new record low 365 day average heads over the horizon.
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Re: 365 day average extent poll
« Reply #45 on: September 21, 2020, 10:42:57 AM »
Interesting. I think a new 365-day record will happen somewhere in winter, as long as 2020/21 avoids the strong refreeze 2019/20 had. I think last winter had a strong freezing from about November onwards, moving gradually well down the order to 10th position or thereabouts. So this is where the window of opportunity for a new record opens up.

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Re: 365 day average extent poll
« Reply #46 on: September 21, 2020, 11:41:49 AM »
And a 22k extent loss followed by a zero extent change puts 2020 in the frame again.

For a record low 365 day average in 2020 2020 extent has to be on average 275k less than 2019. On this day it is 330k.

The key for a record low 365 is for 2020 to match the slow refreeze from now to late October in 2019. From late October the 2019 refreeze accelerated. See the daily change graph Sept to Dec attached - (daily change smoothed into the 7 day trailing average).

If 2020 matches 2019 in a rapid refreeze from late October (or earlier) all bets are off.
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Re: 365 day average extent poll
« Reply #47 on: September 21, 2020, 05:00:59 PM »
Slightly off-topic given the explicit 365 day period in the title of this thread, but I was wondering what period of time ending today *would* constitute a record.  Surely, for example, the ten-year period ending today has lower average extent than any other 10-year period for which we have data.  I'd bet that's true for five years, too, but it's less sure.  What about two years? 1.5?

Of course, it's entirely possible that 2020 extent will stay low enough to cross under 2012 in some weeks or months, at which point the answer collapses suddenly to one day.     
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Re: 365 day average extent poll
« Reply #48 on: September 21, 2020, 05:22:52 PM »
Slightly off-topic given the explicit 365 day period in the title of this thread, but I was wondering what period of time ending today *would* constitute a record.  Surely, for example, the ten-year period ending today has lower average extent than any other 10-year period for which we have data.  I'd bet that's true for five years, too, but it's less sure.  What about two years? 1.5?

Of course, it's entirely possible that 2020 extent will stay low enough to cross under 2012 in some weeks or months, at which point the answer collapses suddenly to one day.   
Look again at the graphs. You will see that the record low 365 day average was reached around the 1st April 2017. 2012 confuses the issue. Yes, in 2012 a record low in August & September, but March 2016 to March 2017 were lower than 2012 for most months.

Last year I thought at one time a new record low would happen in late 2019, simply because of the October monthly average being a record low. But then refreeze kicked in strongly. All 2020 extent has to do is to continue to stay below the 2019 extent, and then maybe in early 2021 to stay below the early 2021 extent for a new record low.

To answer your question (sort of). At the moment it looks as of it will be nearly 4 years since the last record low for a new record low. Before that it was about 4 years from the record low in about April 2013 to the record low on 1 April 2017.

What happens next? Not a clue.

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Re: 365 day average extent poll
« Reply #49 on: September 26, 2020, 01:53:52 PM »
The current rapid refreeze has reduced substantially the amount 2020 sea ice extent is below 2019.
As a result a new record low in 2020 looks less likely, especially as 2019 extent gains were well below average from now to mid-October.
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