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ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #550 on: June 07, 2019, 07:08:00 PM »
Nevertheless, worth a recap or two on the Antarctic Sea Ice thread since it was it happening there that is causing a scientist or three to scratch their heads.

Analysis of the latest archived data from the first meteorological satellites also says that the ice in Antarctica is decreasing:

https://diablobanquisa.wordpress.com/2018/09/13/antarctic_sea_ice_1960s_2018/




ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #551 on: June 07, 2019, 07:10:38 PM »
In addition, there are estimates from the first Antarctic researchers, who also speak of much more sea ice off the coast of Antarctica in the 19th century:


diablobanquisa

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Re: Global sea ice area and extent data
« Reply #552 on: June 07, 2019, 09:39:13 PM »
Nevertheless, worth a recap or two on the Antarctic Sea Ice thread since it was it happening there that is causing a scientist or three to scratch their heads.

Analysis of the latest archived data from the first meteorological satellites also says that the ice in Antarctica is decreasing:

https://diablobanquisa.wordpress.com/2018/09/13/antarctic_sea_ice_1960s_2018/





Thank you for linking to my blog post about Antarctic sea ice since the 1960s. Glad to see it is helpful!

I think that, although the almost flat trend for late November SIE during the multi-channel passive microwave satellite record becomes a slight negative trend when data from 1967 onward are incorporated to the record, this trend should be taken with caution due to the wider error margins in the earlier part of the record.
Overall, perhaps it would be safer to say that the trend in winter and spring Antarctic SIE during the last 50 years looks almost flat.



In addition, there are estimates from the first Antarctic researchers, who also speak of much more sea ice off the coast of Antarctica in the 19th century:

https://tamino.files.wordpress.com/2010/10/shem140.jpg

However, according to more recent estimates from the ship logbooks of explorers during 1897–1917 it seems that "summer sea ice edge was between 1.0 and 1.7° further north in the Weddell Sea during this period but that ice conditions were surprisingly comparable to the present day in other sectors."  https://www.the-cryosphere.net/10/2721/2016/ T. Edinburgh and J. J. Day: Estimating the extent of Antarctic summer sea ice during the Heroic Age of Antarctic Exploration


Figure 4.The estimated DJFM Antarctic sea ice extent climatology for  the  period  1897–1917,  with  and  without  the  inclusion  of  the Worby and Comiso offset, is plotted alongside time series of DJFMmean sea ice extent calculated from HadISST2.2, NASA Team and NASA PM Bootstrap sea ice concentration datasets.


A closer comparison against the satellite era:

It seems that the most consistent values to be compared against the satellite era are those labelled as "with Worby&Comiso offset". Anyway, data from the early XXth century suggest a surprinsingly flat trend again. Perhaps the five decades without observations (1920-1970) could be hiding some multidecadal variability, who knows.



« Last Edit: June 07, 2019, 10:18:53 PM by diablobanquisa »

ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #553 on: June 08, 2019, 03:48:39 AM »
Anyway, data from the early XXth century suggest a surprinsingly flat trend again.

Where do you see the flat trend?

Episodic data from the beginning of the 20th century and the 60s show that there was as much ice in Antarctica as in the record year 2014.



For comparison, the Nimbus-1 worked only 25 days:

https://en.wikipedia.org/wiki/Nimbus_1
Quote
Nimbus 1 was launched on August 28, 1964, by a Thor-Agena rocket from Vandenberg Air Force Base, California, United States. The spacecraft functioned nominally until 22 September 1964.

That is, occasional first satellite observations in 1964 observed an almost record high ice area in Antarctica (compared to continuous near 40 year after 1979).

In this regard, the probability of a flat trend in Antarctica is almost zero. At 95%, the 100-year trend is associated with a decrease in ice area.
« Last Edit: June 08, 2019, 05:44:41 AM by ArcticMelt2 »

ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #554 on: June 08, 2019, 05:05:16 AM »
Perhaps the five decades without observations (1920-1970) could be hiding some multidecadal variability, who knows.

In the Internet you can find data for the mid-20th century from whalers.

http://www-das.uwyo.edu/~geerts/cwx/notes/chap11/sea_ice.html
Quote
Whalers' logbooks dating from as early as the early 20th century provide anecdotal evidence. At southern whaling stations the ice cover has decreased by about 25% between 1950 and 1975, i.e. -10% per decade (2).

https://www.comnap.aq/SiteAssets/SitePages/SeaIceWorkshop/Public_Worby.pdf
The graph from this presentation from 22 pages is especially visual.
« Last Edit: June 08, 2019, 06:24:08 AM by ArcticMelt2 »

ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #555 on: June 08, 2019, 05:22:38 AM »
Taking into account data on the Arctic.

In general, the global ice area over the past 100 years has decreased by about 20%. The lion's share of this reduction occurred in recent decades.

ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #556 on: June 08, 2019, 10:41:03 AM »
Which data are you using to get to the 6% decline in global sea ice from the 80's to 10's?
I am only calculating on the stats used on this site.

The latest post showed:
1980's 24,033,325
2010's 23,331...

3%.

You misjudge. It is important to consider Area, not Extent.

I have now downloaded the latest data from here.
https://sites.google.com/site/arctischepinguin/home/global-sea-ice
https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/data/nsidc_global_nt_final_and_nrt.txt.gz?attredirects=0

And got the following values for decades:

80s 19,00
90s 18,81
00s 18,34
10s 17,72

So in reality, the fall in the last 40 years is 7%.

Approximately the same amount of lost snow cover is estimated.
https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg1-chapter4-1.pdf

Quote
Over the longer 1922 to 2005 period (updated from Brown, 2000), the linear trend in March and April NH SCA (Figure 4.2) is a statistically significant reduction of 2.7 ± 1.5 × 10^6  km2 or 7.5 ± 3.5%.

This means the planet receives a huge amount of additional heat.
« Last Edit: June 08, 2019, 10:46:15 AM by ArcticMelt2 »

diablobanquisa

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Re: Global sea ice area and extent data
« Reply #557 on: June 08, 2019, 10:57:06 AM »
That is, occasional first satellite observations in 1964 observed an almost record high ice area in Antarctica (compared to continuous near 40 year after 1979).

"However, in August 1966 the maximum sea ice extent fell to 15.9x10km± 0.3x10km. This is more than 1.5x10km below the passive microwave record of 17.5x10km set in September of 1986."

Gallaher & Garret Campbell, https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140017193.pdf

That is, occasional first satellite observations observed an almost record high in 1964, but a record low in 1966. Both should be taken into account.



https://www.comnap.aq/SiteAssets/SitePages/SeaIceWorkshop/Public_Worby.pdf
The graph from this presentation from 22 pages is especially visual.

That graph shows data from De la Mare 1997.
However, regarding De la Mare data, Ackley et al. stated: "Our work showed a consistent summer offset (November‐December), with the ship‐observed ice edge 1 ‐ 1.5° north of the satellite‐derived ice edge. We further reexamine the use of whale catch as an ice edge proxy where agreement was claimed between the satellite ice edge (1973‐1987) and the ship whale catch positions. This examination shows that, while there may be a linear correlation between ice edge position and whale catch data, the slope of the line deviates from unity and the ice edge is also further north in the whale catch data than in the satellite data for most latitudes. We compare the historical (direct) record and modern satellite maps of ice edge position accounting for these differences in ship and satellite observations. This comparison shows that only regional perturbations took place earlier, without significant deviations in the mean ice extents, from the pre‐1950s to the post‐1970s. This conclusion contradicts that previously stated from the analysis of whale catch data that indicated Antarctic sea ice extent changes were circumpolar rather than regional in nature between the two periods."
Ackley et al. 2003 https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1751-8369.2003.tb00091.x

Worby&Comiso 2004 (https://www.sciencedirect.com/science/article/abs/pii/S0034425704001415) describe the offset between ship observed sea ice edge and the sea ice edge derived from passive microwave data too. This offset must be taken into account when comparing ship observations with passive microwave satellite observations. That is the reason why Edinburgh and Day (https://www.the-cryosphere.net/10/2721/2016/) present their data with the "Worby&Comiso" offset. If you compare the ship observations from 1897-1917 (taking into account the offset) with the passive microwave satellite observations from 1973 onward, results are rather similar (despite regional variations, i.e. more ice at the Weddell Sea one century ago).

« Last Edit: June 08, 2019, 11:03:56 AM by diablobanquisa »

ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #558 on: June 08, 2019, 11:29:39 AM »
regional perturbations took place earlier, without significant deviations in the mean ice extents, from the pre‐1950s to the post‐1970s

Naturally, this data is not as accurate as satellite. But they are the most accurate of the pre-satellite era.

The number of whaling expeditions many times exceeds the number of scientific expeditions of the beginning of the 20 century. Compare:

https://www.the-cryosphere.net/10/2721/2016/tc-10-2721-2016.pdf

Quote
Data from 185 whaling expeditions (mostly Norwegian but some from English whaling logbooks) were used as its basis (H. Titchner, personal communication, 2016).

1931 to 1987 - 56 years old

against the data of only 11 scientific expeditions for only 20 years old (1897-1917).

16124  records about ice edge against 191 (84 times difference).

In general, data on the secular decrease in the area of ice around Antarctica is much more than on the zero trend. This is a trivial statistic.

It is likely that the authors of the last work added an epithet ("heroic times") to somehow diminish this comparison (the authors wanted a sensation that the ice does not melt because of AGW?). Although James Cook experienced much greater hardship at the end of the 18th century, when he could not get through to the shores of Antarctica at all.

That is, occasional first satellite observations observed an almost record high in 1964, but a record low in 1966. Both should be taken into account.

I think there are no big contradictions. Probably between 1964 and 1966, there was a major decrease in the ice area. This is similar to the difference between 2014 and 2016 in Antarctica or the difference between 2012 and 2013 in the Arctic.

ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #559 on: June 08, 2019, 12:35:17 PM »
An additional advantage of whaler's observations is the fact that they ply along the edge of the ice, where whales like to rest. And scientific expeditions, on the contrary, quickly cross the ice edge.

In this regard, there are data for Svalbard even for 400 years:

https://link.springer.com/article/10.1007/s00300-014-1482-1
Quote
The position of the ice edge (the gray vertical bars) in August between Svalbard and Franz Josef Land for the period 1553–2012, given as the mean latitude within the sector 20–45°E (modified after Vinje 1999 and updated to summer 2012).



These data confirm that the most severe iсe conditions were around 1780. Unhappy James Cook found himself at the wrong time, in the wrong place. He could not pass the northwest passage (he did not even reach Barrow), nor make his way to the shores of Antarctica.

Just imagine what a crazy amount of ice we have lost in the last 200 years due to anthropocentric global warming!

And of course you can imagine what will happen to the whales when all sea ice melts (this will happen very soon). They can cool more, and are likely to become extinct like polar bears despite protective measures in recent decades.

ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #560 on: June 08, 2019, 12:51:54 PM »
(he did not even reach Barrow)

Research ships were able to break through the ice to Cape Barrow only after 40 years!

https://en.wikipedia.org/wiki/Frederick_William_Beechey

Quote
In 1825, Beechey was appointed to command HMS Blossom. His task was to explore the Bering Strait in concert with Franklin and Parry operating from the east. In the summer of 1826, he passed the strait and a barge from his ship reached 71°23'31" N., and 156°21'30" W. near Point Barrow which he named, a point only 146 miles west of that reached by Franklin's expedition from the Mackenzie River.

Exactly in the same decade, the first ships were able to break through the ice to the shores of Antarctica! Now this sounds surprising due to the fact that most of the coast of Antarctica in summer are freed from sea ice.


gerontocrat

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Re: Global sea ice area and extent data
« Reply #561 on: June 08, 2019, 01:00:05 PM »
JAXA Global Sea Ice Extent as at 7 June 2019 :    21,168,865  km2

Back to what's happening this year

In the last week Arctic extent loss was more above average than below, but most days saw high Antarctic extent gain. But extent has remained lowest, now for 59 days this year, 53 days in a row.

Extent is 744 k below 2017, 599 k below 2018.

- extent gain on this day 93 k,37 k more than the the average gain of 56k on this day,
- extent gain from minimum to date is 5.39 million km2, 1.46 million km2 (21%) less than the average gain of 6.85 milllion km2 by this day,
-on average 75.9% of extent gain done and 150 days to maximum, but before that there is a false maximum (in July) and a false minimum (in September) before the (usually) true maximum around the 4th of November.

The Perils of Projections
- last 10 years average remaining extent gain would give a maximum of 23.81 million km2,  173k more than the record low maximum in 2016 and 2nd lowest in the satellite record.

Being a combination of two separate pieces of data volatility is often very high. Confidence in any projection is even lower than normal.
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FishOutofWater

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Re: Global sea ice area and extent data
« Reply #562 on: June 08, 2019, 10:31:35 PM »
Roger, you might consider taking your own advice:

"Leaving aside all the snide comments, & responses to unasked questions- such as why the arctic decreases are quite large whereas the antarctic increases ( decadally) are also quite large - this still seems a small ( ish ) figure, without context of previous comparable measurements.

The comments that the picture has changed in the last 4 years seem remarkably silly.
"

I don't care about your opinion about what the changes in the Antarctic over the last 4 years. You have demonstrated no competence in analyzing what the sudden loss of large quantities of sea ice means. I suspect that few other people care about your opinion.

If you presented a cogent analysis of what has changed and what has not over the past 4 years in Antarctic waters your opinion might be more interesting. If you cited papers about why the sea ice extent expanded for several decades before the sudden reversal, you opinion might be based on something more than an assertion. But it's not, perhaps because you aren't interested in the science. You appear to have a political agenda.

When a natural system makes a sudden unexpected shift, most scientists want to know why. Thre's nothing silly about the sudden drop in sea ice around Antarctica.
« Last Edit: June 08, 2019, 11:14:56 PM by FishOutofWater »

Shared Humanity

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Re: Global sea ice area and extent data
« Reply #563 on: June 08, 2019, 11:00:43 PM »
JAXA Global Sea Ice Extent as at 7 June 2019 :    21,168,865  km2

Back to what's happening this year


Awww.... I was beginning to enjoy those graphs with no data points.  ;)

ArcticMelt2

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Re: Global sea ice area and extent data
« Reply #564 on: June 09, 2019, 06:30:58 AM »
I don't care about your opinion about what the changes in the Antarctic over the last 4 years. You have demonstrated no competence in analyzing what the sudden loss of large quantities of sea ice means. I suspect that few other people care about your opinion.

By the way, I yesterday looked at trends in the monthly NSDIC data. In November, the trend has already become zero. Such a stupid 4 years.

gerontocrat

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Re: Global sea ice area and extent data
« Reply #565 on: June 09, 2019, 11:53:08 AM »
JAXA Global Sea Ice Extent as at 7 June 2019 :    21,168,865  km2
Back to what's happening this year

Awww.... I was beginning to enjoy those graphs with no data points.  ;)
Ok, just for you this what I wrote about Antarctic sea ice on the Antarctic sea ice thread
___________________________________________________________________
So here is a reprise of the story of Antarctic sea ice in the satellite record that I have gleaned mainly from the ASIF and links provided by it.

From 1979 to to about 2010 the general trend of Antarctic Ice was to increase very very slowly - a glacial pace indeed.
Then until the maximum maximum of 2014 and maximum minimum of 2013 the sea ice seemed to be increasing faster. The minimum grew at an even faster pace in percentage terms  than the max.
WHY?
Scientists, including Hansen noted that the GRACE project showed that Antarctic Mass Loss (due to ice sheet loss) was increasing at an ever increasing rate. The result - a growing flood in the Southern summer of very cold FRESH water spreading out over the surrounding Southern Ocean, sitting as a layer on top of warmer but denser salt water. The freezing point of freshwater is higher than of salt water - hence sea ice growing.

BUT
From 2014 to 2018 the sea ice maximum dropped by 10%.
From 2013 to 2018 the sea ice minimum dropped by 40%.

It is possible that in 2019 the maximum will drop by another 4 %

What's going on?
The paper quoted below talks about 2016 and 2017. The change happened earlier and seems to be still happening. So since our knowledge of what's going on in Antarctica and why is inversely proportional to the size of the place under examination, the answer that belongs to me is a resounding - don't know.

We do know the air is heating,
We do know the oceans are heating,
We do know the Antarctic Ice Sheet , glaciers and ice shelves are melting.

And the area covered by sea ice is shrinking.

And that is definitely, absolutely all I'm going to say about that.
___________________________________________________
https://www.nature.com/articles/s41467-018-07865-9
Quote
Discussion
The evidence indicates that the rapid decrease in Antarctic sea ice
extent in late 2016 and the significant changes in the upper
Southern Ocean were likely caused by three factors. First, record
SST, precipitation, and convective heating anomalies in the
eastern tropical Indian and far-western Pacific Oceans produced
an anomalous Rossby wave response in the mid- and high
southern latitudes in SON 2016. The consequent teleconnection
pattern around Antarctica was characterized by a record negative
phase of the SAM, and a preponderance of warm, moist southward
surface winds that drove sea ice southwards and produced
decreased sea ice extent. Second, the anomalous surface winds
associated with this teleconnection pattern were also associated
with positive wind stress curl anomalies, southward Ekman
transport, and warmer surface water transported southward.
Third, a decadal timescale trend of negative wind stress curl
anomalies over the 2000s, associated with the positive trend of the
SAM and the negative phase of the IPO, moved warmer subsurface
water in the Southern Ocean upward in the column (part
of the so-called two-timescale response22–24). Then in late 2016,
the negative SAM contributed to producing anomalously warm
SSTs such that the entire upper 600m (over many areas of the
Southern Ocean) then was characterized by positive temperature
anomalies. These warmer ocean temperatures, combined with
the direct effects of surface wind forcing on the sea ice, produced
the rapid decrease of Antarctic sea ice extent. These conditions
were maintained through 2017, with reduced sea ice extent
compared to the average of the 2000s through JJA 2018.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
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roger white

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Re: Global sea ice area and extent data
« Reply #566 on: June 10, 2019, 08:38:37 AM »
Thanks for all the comments. Of course all phenomena merit investigating, even 4 years of shrinking antarctic sea ice. Though surely this is too short a period for anyone to jump to conclucions.
Indeed the satellite record is very short surely when measuring the planet's climate.
My main point though remains. On it's own the decrease in global sea ice totals reported on this forum is.. ( 3% day to day -7% on other measures as pointed out ) from the 80's to the 2010's.
I'm now clear on that.

<snip, you're lagging again, the Hiatus BS is no longer a serious climate risk denier argument; N.>
« Last Edit: June 10, 2019, 12:10:39 PM by Neven »

Pmt111500

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Re: Global sea ice area and extent data
« Reply #567 on: June 10, 2019, 04:43:36 PM »
Here are the current (20190609) graphs of Global Ice Area and Extent. The about 1,5Mkm2 losses on both measures equates to a bit smaller loss than area of Alaska or 2,5 Texases. If the ice lost was ~4 inches thicc the energy required for the melt would be quite a lot. The calculation of the exact amount is left as an excersice to those who think pouring steaming water on growing crops is a good idea.
« Last Edit: June 10, 2019, 04:52:25 PM by Pmt111500 »
Cooling the outside by heat pump.

Tony Mcleod

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Re: Global sea ice area and extent data
« Reply #568 on: June 12, 2019, 09:38:38 PM »
Ok, I'm calling it: we've reached the max, maybe for the year, maybe longer. :o

« Last Edit: June 12, 2019, 09:46:35 PM by Tony Mcleod »

gerontocrat

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Re: Global sea ice area and extent data
« Reply #569 on: June 13, 2019, 06:56:47 AM »
JAXA Global Sea Ice Extent as at 12 June 2019 :     22,003,693  km2

In the last week Arctic extent loss was below average, and most days saw high Antarctic extent gain. But extent has remained lowest, now for 64 days this year, 58 days in a row.

Extent is 440 k below 2017, 931 k below 2018.

- extent gain on this day 69 k,30 k more than the the average gain of 39 k on this day,
- extent gain from minimum to date is 5.75 million km2, 1.35 million km2 (19%) less than the average gain of 7.11 milllion km2 by this day,
-on average 78.8% of extent gain done and 145 days to maximum, but before that there is a false maximum (in July) and a false minimum (in September) before the (usually) true maximum around the 4th of November.

The Perils of Projections
- last 10 years average remaining extent gain would give a maximum of 23.92 million km2,  282 k more than the record low maximum in 2016 and 2nd lowest in the satellite record.

Being a combination of two separate pieces of data volatility is often very high. Confidence in any projection is even lower than normal. In contrast with JAXA extent data, NSIDC Global Arctic Area in contrast shows a sharp drop, but I think it is premature to call the false maximum this early as in the previous post. We will see how the data develops over the next few days.
"Para a Causa do Povo a Luta Continua!"
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"Damn, I wanted to see what happened next" (Epitaph)

grixm

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Re: Global sea ice area and extent data
« Reply #570 on: June 13, 2019, 03:37:54 PM »
Hi, first post on this forum. I think I might get addicted.

Not sure if it has been posted before, but I saw that yesterday the NSIDC sea ice extents on both the arctic and antarctic individually were the lowest in the satellite era on this date.

https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/

Rod

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Re: Global sea ice area and extent data
« Reply #571 on: June 13, 2019, 05:40:58 PM »
This is area, not extent, but I thought these tweets from Kevin Pluck over the last four days pretty much sum up where we are right now. 

be cause

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Re: Global sea ice area and extent data
« Reply #572 on: June 13, 2019, 06:12:49 PM »
tomorrow .. OMFG !!! ? B.C.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

oren

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Re: Global sea ice area and extent data
« Reply #573 on: June 13, 2019, 07:17:13 PM »
Hello and welcome, grixm. And yes, you are correct.

Tony Mcleod

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Re: Global sea ice area and extent data
« Reply #574 on: June 14, 2019, 06:08:10 AM »
it is premature to call the false maximum this early as in the previous post. We will see how the data develops over the next few days.

I remember watching with morbid fascination as 2016 drifted on lower and lower into uncharted σ territory. That year's "false maximum" was the maximum. I thought at the time this is exactly the kind of 'flutter' you'd see as a system flips towards a new attractor and if that is what is happening, it is such a titanic system (see what I did there), there is no way its flipping back anytime soon.

Weird is the new normal so I won't be surprised if 2019 is a repeat of 2016 or even a new low. Thats a big June fall to climb back out of.

gerontocrat

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Re: Global sea ice area and extent data
« Reply #575 on: June 14, 2019, 08:15:44 AM »
While NSIDC Area shows a collapse in total area, JAXA extent numbers show well above average daily increases in extent. Quite a disconnect and growing.
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Tony Mcleod

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Re: Global sea ice area and extent data
« Reply #576 on: June 14, 2019, 08:36:25 AM »
Any ideas about the disconnect? The two seem at odds.

RikW

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Re: Global sea ice area and extent data
« Reply #577 on: June 14, 2019, 11:44:30 AM »
I'd say it's because of ice breaking up in smaller floes and spreading increases so more parts of the grid that have at least 15% ice cover, thus higher extent.

At the short time that creates a gap between extent and area, because there are more parts with some ice while in the longer term it will be disastrous for the ice, many small parts is more open sea, so more heat that can be trapped and more ice that is probably easy to melt, because of the smaller parts.

Do I guess we will see a cliff in extent in the near future because those small parts will probably disappear

gerontocrat

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Re: Global sea ice area and extent data
« Reply #578 on: June 14, 2019, 12:12:34 PM »
Any ideas about the disconnect? The two seem at odds.

From reading the Arctic melting thread recently and in years past, this variation may also be partly because of strong melt ponding in some parts of the Arctic. It seems this confuses the sensors to assume open water though the ice is still there. The JAXA sensor uses much finer resolution than the older NSIDC sensor, and is much newer technology. Perhaps the JAXA sensor is less likely to be fooled by this ponding and in smaller areas.

However, normally such discrepancies tend to iron out somewhat over a longer period. So perhaps as regards the NSIDC data, one swallow does not make a summer? (or the JAXA data is behind the curve).

patiencia, calma...
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Re: Global sea ice area and extent data
« Reply #579 on: June 15, 2019, 12:42:23 PM »
tomorrow .. OMFG !!! ? B.C.

really...




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Re: Global sea ice area and extent data
« Reply #580 on: June 16, 2019, 10:42:43 AM »
patiencia, calma...

Hmm i don't think humans are ever going to see 18m sq km of seaice area again.

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Re: Global sea ice area and extent data
« Reply #581 on: June 16, 2019, 04:03:18 PM »
No JAXA data, so here is the NSIDC Global daily (NOT 5 day) extent.

Note the 1980's wobbles, caused by NSIDC only posting data once every 2 days until the late 1980's. Even using a cleverer average formula (combining sum and countif) will not fix it. Never mind, the message is still clear.

I am not writing off more than 18 million km2 area as a late October / early November maximum, though each day seems to make a really low maximum more probable on both measures.
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Re: Global sea ice area and extent data
« Reply #582 on: June 16, 2019, 04:38:55 PM »
First, you fill in the 1980s missing data days by averaging the previous day and the next day's data. Then the way is clear.

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Re: Global sea ice area and extent data
« Reply #583 on: June 16, 2019, 04:51:43 PM »
First, you fill in the 1980s missing data days by averaging the previous day and the next day's data. Then the way is clear.

Linear interpolation is the way to go in CO2 missing days as well, they've become rather sparse normally, but still there might be some missing weeks..
Cooling the outside by heat pump.

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Re: Global sea ice area and extent data
« Reply #584 on: June 16, 2019, 05:44:11 PM »
I wrote a script in vba for excel to clean up the data. It wouldn't be acceptable for a formal research paper but for our purposes it works.

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Re: Global sea ice area and extent data
« Reply #585 on: June 16, 2019, 08:00:31 PM »
First, you fill in the 1980s missing data days by averaging the previous day and the next day's data. Then the way is clear.

Linear interpolation is the way to go in CO2 missing days as well, they've become rather sparse normally, but still there might be some missing weeks..
The penny dropped on how to do it almost all at once instead of plonking in the formula empty cell by empty cell .

make a copy of the data sheet.
In the copy look at each cell of the original data.
   If zero or blank, do the interpolation.
   If there is data, copy that into the copy.
Clean up any odd bits.
Then copy your copy sheet back into the original sheet as numbers (not with formulas).

- and the wobbles have gone
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Re: Global sea ice area and extent data
« Reply #586 on: June 17, 2019, 03:48:33 AM »
Happy to help 8)

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Re: Global sea ice area and extent data
« Reply #587 on: June 17, 2019, 12:51:35 PM »
patiencia, calma...

Hmm i don't think humans are ever going to see 18m sq km of seaice area again.
This is a bit silly.  Apart from one exceptional year, the Nov peak is always higher than the June peak, and the June peak was over 18m.

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Re: Global sea ice area and extent data
« Reply #588 on: June 17, 2019, 01:47:11 PM »
patiencia, calma...

Hmm i don't think humans are ever going to see 18m sq km of seaice area again.
This is a bit silly.  Apart from one exceptional year, the Nov peak is always higher than the June peak, and the June peak was over 18m.

I think it is silly to assume we are only going to see one exceptional year.

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Re: Global sea ice area and extent data
« Reply #589 on: June 17, 2019, 09:03:41 PM »
patiencia, calma...

Hmm i don't think humans are ever going to see 18m sq km of seaice area again.
This is a bit silly.  Apart from one exceptional year, the Nov peak is always higher than the June peak, and the June peak was over 18m.
I think it is silly to assume we are only going to see one exceptional year.
True, but for your "never again" to be true, you're expecting every year from now on to be exceptional....

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Re: Global sea ice area and extent data
« Reply #590 on: June 18, 2019, 06:43:51 AM »
patiencia, calma...

Hmm i don't think humans are ever going to see 18m sq km of seaice area again.
This is a bit silly.  Apart from one exceptional year, the Nov peak is always higher than the June peak, and the June peak was over 18m.
I think it is silly to assume we are only going to see one exceptional year.
True, but for your "never again" to be true, you're expecting every year from now on to be exceptional....


Is it "silly" to be expecting a BOE this year? I don't think so. I agree that is not the most likely outcome for this NH summer, but also not impossible. The year after? The year after that? Many here would be happy if we can kick the BOE can down the road for that long. After a BOE would I contend every year from then on would "be exceptional".

Just taking another look at the graph I would say it is 50/50 as to whether 18m km will be topped again this year and if that were the outcome then next year the odds would be even longer.
Yes, all idle speculation.

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Re: Global sea ice area and extent data
« Reply #591 on: June 19, 2019, 08:59:34 AM »
JAXA Global Sea Ice Extent as at 18 June 2019 :      22,403,886 km2

In the last 2 weeks Arctic extent loss was well below average, and while Antarctic extent gain was up and down around the average. Extent has remained lowest, now for 70 days this year, 64 days in a row.

Extent is 242 k below 2017, 730 k below 2018.

- extent gain on this day 56 k, 7 k more than the the average gain of 49 k on this day,
- extent gain from minimum to date is 6.15 million km2, 1.24 million km2 (17%) less than the average gain of 7.11 milllion km2 by this day,
-on average 81.9% of extent gain done and 139 days to maximum, but before that there is a false maximum (in July) and a false minimum (in September) before the (usually) true maximum around the 4th of November.

The Perils of Projections
The last 10 years average remaining extent gain would give a maximum of 24.04 million km2,  402 k more than the record low maximum in 2016 and 2nd lowest in the satellite record.

Being a combination of two separate pieces of data volatility is often very high. Confidence in any projection is even lower than normal. However, the JAXA extent data so far does not point to a change to the usual pattern of a false maximum in July, a false min in Aug/Sep and a final max in early November.
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gerontocrat

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Re: Global sea ice area and extent data
« Reply #592 on: June 22, 2019, 07:19:52 AM »
JAXA Global Sea Ice Extent as at 21 June 2019 :  22,578,517 km2

In the last 2 weeks Arctic extent loss was well below average, and while Antarctic extent gain was up and down around the average. Extent remained lowest, now for 72 days this year, 66 days in a row.

But the last 3 days saw very high Antarctic Sea Ice gain, while in 2017 for those 3 days global extent dropped. As a result Global extent is now in 2nd place, 12 k above 2017, but 849 k below 2018.

- extent gain on this day 56 k, 26 k more than the the average gain of 30 k on this day,
- extent gain from minimum to date is 6.33 million km2, 1.13 million km2 (15%) less than the average gain of 7.46 milllion km2 by this day,
-on average 82,7% of extent gain done and 136 days to maximum, but before that there is a false maximum (in July) and a false minimum (in September) before the (usually) true maximum around the 4th of November.

The Perils of Projections
The last 10 years average remaining extent gain would give a maximum of 24.14 million km2,  0.5 million km2 more than the record low maximum in 2016 and 2nd lowest in the satellite record.

Being a combination of two separate pieces of data volatility is often very high. Confidence in any projection is even lower than normal. However, the JAXA extent data so far does not point to a change to the usual pattern of a false maximum in July, a false min in Aug/Sep and a final max in early November.
"Para a Causa do Povo a Luta Continua!"
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Re: Global sea ice area and extent data
« Reply #593 on: June 23, 2019, 05:42:07 PM »
patiencia, calma...

Hmm i don't think humans are ever going to see 18m sq km of seaice area again.

back over 18 million km^2 we go!
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Re: Global sea ice area and extent data
« Reply #594 on: June 24, 2019, 10:39:09 PM »
patiencia, calma...

Hmm i don't think humans are ever going to see 18m sq km of seaice area again.

I'm pretty certain we'll see 19 again, and would be surprised if we don't see 20 again.  Neither the arctic nor the antarctic trend is smooth enough to predict steady loss year on year from here onwards.

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Re: Global sea ice area and extent data
« Reply #595 on: June 26, 2019, 12:36:46 PM »
patiencia, calma...

Hmm i don't think humans are ever going to see 18m sq km of seaice area again.

back over 18 million km^2 we go!

and definitely the last time this time.

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Re: Global sea ice area and extent data
« Reply #596 on: June 26, 2019, 01:18:40 PM »
JAXA Global Sea Ice Extent as at 25 June 2019 :   22,749,877 km2

In the last few days Arctic extent loss was mostly below average, and while Antarctic extent gain was much above the average. However, extent went back to lowest simply because 2017 extent ticked up, but only just, now for 75 days this year.

Global extent is now 13 k below 2017, and 801 k below 2018.

- extent gain on this day 48 k, 32 k more than the the average gain of 16 k on this day,
- extent gain from minimum to date is 6.50 million km2, 1.02 million km2 (13.5%) less than the average gain of 7.52 milllion km2 by this day,
-on average 83.3% of extent gain done and 136 days to maximum, but before that there is a false maximum (in July) and a false minimum (in September) before the (usually) true maximum around the 4th of November.

The Perils of Projections
The last 10 years average remaining extent gain would give a maximum of 24.26 million km2,  0.62 million km2 more than the record low maximum in 2016 and 2nd lowest in the satellite record.

Being a combination of two separate pieces of data volatility is often very high. Confidence in any projection is even lower than normal. However, the JAXA extent data so far does not point to a change to the usual pattern of a false maximum in July, a false min in Aug/Sep and a final max in early November.
"Para a Causa do Povo a Luta Continua!"
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gerontocrat

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Re: Global sea ice area and extent data
« Reply #597 on: June 27, 2019, 11:17:13 AM »
JAXA Global Sea Ice Extent as at 26 June 2019 :    22,872,881 km2

On this day Arctic extent loss was below average, and Antarctic extent gain was double  the average. So extent has slumped to 2nd lowest especially because 2017 extent reduced a lot on this day.

Global extent is now 163 k above 2017, and 740 k below 2018.

- extent gain on this day 123k, 108 k more than the the average gain of 15 k on this day,
- extent gain from minimum to date is 6.62 million km2, 0.91 million km2 (12.1%) less than the average gain of 7.53 milllion km2 by this day,
-on average 83.5% of extent gain done and 131 days to maximum, but before that there is a false maximum (in July) and a false minimum (in September) before the (usually) true maximum around the 4th of November.

The Perils of Projections
The last 10 years average remaining extent gain would give a maximum of 24.36 million km2,  0.73 million km2 more than the record low maximum in 2016 and 2nd lowest in the satellite record.

Being a combination of two separate pieces of data volatility is often very high. Confidence in any projection is even lower than normal. However, the JAXA extent data so far does not point to a change to the usual pattern of a false maximum in July, a false min in Aug/Sep and a final max in early November.
"Para a Causa do Povo a Luta Continua!"
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gerontocrat

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Re: Global sea ice area and extent data
« Reply #598 on: June 29, 2019, 09:01:35 AM »
VOLATILITY

What a difference 2 days makes.

   Arctic sea ice loss was low,
   Antarctic sea ice gain was high.
Global extent quickly rising.

2 days later,
   Arctic sea ice loss is high,
  Antarctic sea ice gain is low.
Global extent slumps.

Will the change persist? On Monday an overall look at June.
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gerontocrat

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Re: Global sea ice area and extent data
« Reply #599 on: July 01, 2019, 12:11:05 PM »
JAXA Global Sea Ice Extent as at 30 June 2019 :  22,754,070 km2

This week was a mixture of very high extent gain and then a run of extent losses.

Global extent in 2nd place, 90 k above 2017, and 993 k below 2018.

- extent loss on this day 18k, 21k different from the the average gain of 3 k on this day,
- extent gain from minimum to date is 6.50 million km2, 1.01 million km2 (13.4%) less than the average gain of 7.51 milllion km2 by this day,
-on average 83.3% of extent gain done and 127 days to maximum in early November.
 
But before the maximum, there is firstly a false maximum (in July). Indeed the average for the 2010's has this false max in the last week in June. For the next 2 and a bit months extent should fall until the false minimum (in early September),  before rising to the (usually) true maximum around the 4th of November.

The Perils of Projections
The last 10 years average remaining extent gain would give a maximum of 24.26 million km2,  0.63 million km2 more than the record low maximum in 2016 and 2nd lowest in the satellite record.

Being a combination of two separate pieces of data volatility is very high. The last table shows how remaining freeze varied from the average from  plus 80% to minus 99%.
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