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Neven

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Is Antarctic sea ice really expanding?
« on: January 14, 2014, 06:14:12 PM »
New paper in The Cryosphere:

Quote
A spurious jump in the satellite record: is Antarctic sea ice really expanding?
I. Eisenman1, W. N. Meier2, and J. R. Norris1
1Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA, USA
2NASA Goddard Space Flight Center, Greenbelt, MD, USA

Abstract. Recent estimates indicate that the Antarctic sea ice cover is expanding at a statistically significant rate with a magnitude one third as large as the rapid rate of sea ice retreat in the Arctic. However, during the mid-2000s, with several fewer years in the observational record, the trend in Antarctic sea ice extent was reported to be considerably smaller and statistically indistinguishable from zero. Here, we show that the increase in the reported trend occurred primarily due to the effect of a previously undocumented change in the way the satellite sea ice observations are processed for the widely-used Bootstrap algorithm dataset, rather than a physical increase in the rate of ice advance. Although our analysis does not definitively identify whether this undocumented change introduced an error or removed one, the resulting difference in the trends suggests that a substantial error exists in either the current dataset or the version that was used prior to the mid-2000s, and numerous studies that have relied on these observations should be reexamined to determine the sensitivity of their results to this change in the dataset. Furthermore, a number of recent studies have investigated physical mechanisms for the observed expansion of the Antarctic sea ice cover. The results of this analysis raise the possibility that this expansion may be a spurious artifact of an error in the satellite observations, and that the actual Antarctic sea ice cover may not be expanding at all.

Citation: Eisenman, I., Meier, W. N., and Norris, J. R.: A spurious jump in the satellite record: is Antarctic sea ice really expanding?, The Cryosphere Discuss., 8, 273-288, doi:10.5194/tcd-8-273-2014, 2014.

Very interesting stuff.
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crandles

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Re: Is Antarctic sea ice really expanding?
« Reply #1 on: January 15, 2014, 02:42:08 AM »
Paper claims there is a very large change in the trend caused by an apparently undocumented change in bootstrap algorithm for estimating sea ice concentrations from passive microwave
satellite measurements of brightness temperatures at multiple frequencies
and polarizations.


(the “Bootstrap” algorithm, is based on interpolation between clusters of points in scatter plots of brightness temperatures (Comiso, 1986) (note that it does not involve the statistical bootstrapping technique).)

“NASA Team” algorithm, is based on difference ratios between brightness temperatures (Cavalieri et al., 1984).

Presumably NASA Team algorithm is not affected.

A change in the Bootstrap algorithm was documented in Comiso and Nishio (2008),
who made an adjustment for consistency between instruments on different satellites and reported the change to have a negligible effect

There is a clear transition in December 1991, which coincides with a satellite sensor change.

Next sensors after 1991 begin in 1995 then 2008.

While erroneous calibration following sensor change is suggested to be consistent with what is seen, the paper isn't sure which version of bootstrap is right. So the paper seems to be identification that there is a problem but investigating what changed, why and which is right is yet to occur.

I don't want to blame anyone without evidence so please view this as a question out of curiosity not as an accusation nor as a hint or suggestion of what will happen. Could new data from introduction of 2008 sensor cause a recalibration resulting in such large changes? For example, if Comiso and Nishio (2008) should have said something like the effect of change in the algorithm is negligible but large differences between sensors readings have caused a large recalibration resulting in a significant change in the trend, would this be consistent with what is shown in the paper? i.e. there wasn't ever an error just new information?
« Last Edit: January 15, 2014, 04:12:31 AM by crandles »

Wipneus

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Re: Is Antarctic sea ice really expanding?
« Reply #2 on: January 15, 2014, 11:17:38 AM »
Very interesting indeed. The (discussion) document is freely available:
http://www.the-cryosphere-discuss.net/8/273/2014/tcd-8-273-2014.pdf

but don't forget to read the supplementary document for much background information, adding sea ice area in the discussion and more graphs:
http://www.the-cryosphere-discuss.net/8/273/2014/tcd-8-273-2014-supplement.pdf

The question was bothering me slightly already, but there are so many other issues that have my attention that I did not investigate. Here is the difference between the Bootstrap derived monthly extent with "NASA Team", both hosted on NSIDC site.



Note the big positive anomaly of the first SSM/I instrument and the negative anomaly during the SSMIS period. The change is 1992 is noted in this paper, those in 1987 and 2007 not.

The picture in the Arctic is different:



Here first SSM/I instrument does not stand out (negatively) at all. The post 2007 period is also all negative.

NASA Team algorithm is known to have a negative bias during melt periods, so the post 2007 period might be explained by the large melt that has occurred during that time.

These graphs are also in fig's S2 and S4 of the supplementary paper, but not looking quite the same. So something else may also play a confusing role:
The scientists seem to derive the extent and area from the gridded ice concentration data published by the NSIDC. That means the differences in extent may also be influenced by little details of grid calculation, arctic "north hole" filling, removal of false ice caused by land spillover and averse weather conditions causing rough sea surfaces and water vapor.

crandles

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Re: Is Antarctic sea ice really expanding?
« Reply #3 on: January 15, 2014, 11:34:04 AM »
Note the big positive anomaly of the first SSM/I instrument and the negative anomaly during the SSMIS period. The change is 1992 is noted in this paper, those in 1987 and 2007 not.

Just for clarity, fig 2 in the paper has text which says

Quote
Transitions between satellite sensors are indicated by vertical dotted lines.

So the change in 1992 is noted in the text of this paper, the change in sensors in 1987 and 2007 is not mentioned in the text of the paper and only indicated by the vertical dotted lines in fig 2 of the paper, in the supplement text and on several figures in the supplement.

Neven

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Re: Is Antarctic sea ice really expanding?
« Reply #4 on: January 15, 2014, 11:39:34 AM »
Tamino weighs in: Southern Discomfort.
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Wipneus

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Re: Is Antarctic sea ice really expanding?
« Reply #5 on: January 15, 2014, 11:50:14 AM »
Note the big positive anomaly of the first SSM/I instrument and the negative anomaly during the SSMIS period. The change is 1992 is noted in this paper, those in 1987 and 2007 not.

Just for clarity, fig 2 in the paper has text which says

Quote
Transitions between satellite sensors are indicated by vertical dotted lines.

So the change in 1992 is noted in the text of this paper, the change in sensors in 1987 and 2007 is not mentioned in the text of the paper and only indicated by the vertical dotted lines in fig 2 of the paper, in the supplement text and on several figures in the supplement.

The are mentioned in the supplementary document.

Aug 1, 1987 is when the SSM/I takes over from SMMR. This is potentially the largest change, the frequency bands are slightly different, antenna's are different, sampling is different (from one measurement per two days to one each day) the orbits are different and as a consequence the north pole hole is different (which might also explain something why nothing is visible in the Arctic).


AbruptSLR

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Re: Is Antarctic sea ice really expanding?
« Reply #6 on: January 16, 2014, 10:35:01 AM »
Personally, I like Tamino's assessment, and I support his conclusions.
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Re: Is Antarctic sea ice really expanding?
« Reply #7 on: July 22, 2014, 07:30:33 PM »
New paper in The Cryosphere:

A spurious jump in the satellite record: is Antarctic sea ice really expanding?

I. Eisenman1, W. N. Meier2, and J. R. Norris1

The paper is published today.  The press release of the European Geosciences Union can be found here, or at phys.org:

http://phys.org/news/2014-07-antarctic-sea-ice-expansion-overestimated.html

Quote
This implies that the Antarctic sea ice trends reported in the IPCC's AR4 and AR5 can't both be correct: our findings show that the data used in one of the reports contains a significant error. But we have not yet been able to identify which one contains the error," says lead-author Ian Eisenman

Steven

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Re: Is Antarctic sea ice really expanding?
« Reply #8 on: July 22, 2014, 08:55:06 PM »
There's also an article about this on LiveScience.com.  That article quotes NASA scientist Josefino Comiso, who seems to disagree with some of the findings in the new Eisenman et al. paper:

http://www.livescience.com/46914-antarctica-sea-ice-expansion-controversy.html

Quote
Comiso agrees that a change in the Bootstrap algorithm introduced bias into the data. However, he contests the new findings, which are published today (July 22) in the journal The Cryosphere. The changes made in 2007 improved the algorithm and corrected problems, he told Live Science. The satellite data, updated using this  correction, shows large increases in Antarctic sea ice, and other groups who have examined the data using different techniques have come up with similar findings, he said. In other words, Comiso believes that version two of the dataset, adjusted after 2007, is correct, reflecting a real increase in Antarctic ice, and that the error was in version one.
« Last Edit: July 22, 2014, 09:07:49 PM by Steven »

Gray-Wolf

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Re: Is Antarctic sea ice really expanding?
« Reply #9 on: February 04, 2015, 11:11:55 AM »
Just a bump as I can't find a 'sea ice' thread for Antarctica?

Sea ice levels are currently dropping back into the pack of previous years data and , as melt season winds up, the pattern of melt is approaching that which I became used too when I first started watching Antarctica?

Has part of the increase in Sea ice been purely a response to global Natural drivers being in a negative phase? Are the changes to those drivers , that appear to be occurring, now starting to show impact in this years melt season?

With Ross all but gone and the Weddell polynia open it has more a pattern of the late 90's than what we have become used to through the noughties?

I'm not saying that the 2% per decade gains that surface freshening/Ozone loss and strengthened wind patterns have ended but that we may well be entering a period where the constant denier clamour about 'record ice levels' will die back? This past year may well prove to be the 98' Nino for sea ice?
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Jim Hunt

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Re: Is Antarctic sea ice really expanding?
« Reply #10 on: February 04, 2015, 01:13:16 PM »
I can't find a 'sea ice' thread for Antarctica?

See also:

"Increasing Antarctic Albedo?"

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Michael Hauber

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Re: Is Antarctic sea ice really expanding?
« Reply #11 on: February 05, 2015, 08:33:22 AM »
Worth noting is that SSTs for the southern ocean not covered by sea ice appear to be cooling over the same period that Antarctic sea ice is measured as increasing.  GISS temp has a http://data.giss.nasa.gov/gistemp/maps/]nice tool for creating trend maps.  I would reccommend settings:

Land: none
Ocean: either of the two options, the default has more cooling in the Southern Ocean.
Map Type: Trend to see trend over time instead of anomaly
Mean Period:  Annual
Time Interval:  1979 to 2014 to match the Cryosphere today record.

A smoothing radius of 250km will show where station drop outs affect land temperature records, but do not seem to show any drop outs for SSTs, presumably because GISS gets the SST data from someone else.  SSTs should be reasonably reliable from 1980 due to satellite records.  Longer time periods show less area of cooling and more area of warming, but I'm not sure how reliable the records are.  There is also some hint in whaling records that Antarctic sea ice was much greater in the past, although I saw a paper a good while back which seemed to say that the likely error range of these records was within range of today's Antarctic ice extent.  Still it seems possible to me that regional multi-decade variations or unique Antarctic polar vortex effects associated with CFCs may have caused a temporary cooling from the late 20th century which corresponds to a temporary increase in Antarctic sea ice, while the overall trend since 1900 may be warming and decreasing sea ice.
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johnm33

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Re: Is Antarctic sea ice really expanding?
« Reply #12 on: February 05, 2015, 11:29:43 AM »
 It'd be interesting to see a salinity map eqivalent over the same timespan, using recommended settings i went for polar orthographic projection.  http://data.giss.nasa.gov/gistemp/maps/

Stephen

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Re: Is Antarctic sea ice really expanding?
« Reply #13 on: August 07, 2015, 12:04:17 PM »
Bumpity bump bump

It's looking like it could be a low max down south this year.

The ice was here, the ice was there,   
The ice was all around:
It crack'd and growl'd, and roar'd and howl'd,   
Like noises in a swound!
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plinius

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Re: Is Antarctic sea ice really expanding?
« Reply #14 on: August 07, 2015, 12:13:24 PM »
doesn't change the mild uptrend though.

Stephen

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Re: Is Antarctic sea ice really expanding?
« Reply #15 on: August 07, 2015, 12:28:25 PM »
doesn't change the mild uptrend though.

No,not yet, but if that kind of flattening of the curve happened to the Arctic Sea Ice graphs then the interwebs would meltdown with commentary.

Maybe Antarctic sea ice is feeling like the unloved sibling not getting enough attention, so has decided to throw a tantrum of it's own?  ;D
The ice was here, the ice was there,   
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Buddy

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Re: Is Antarctic sea ice really expanding?
« Reply #16 on: August 07, 2015, 02:57:06 PM »
Quote
The results of this analysis raise the possibility that this expansion may be a spurious artifact of an error in the satellite observations, and that the actual Antarctic sea ice cover may not be expanding at all.

Fascinating.  Now....what WILL Anthony (Watts), Joe (Bastardi), and Christopher Monckton do for a living now that have yet one MORE arrow removed from the quiver?

Of course....we all KNEW it was never an issue, since the VOLUME of the ice was declining.  I think I hear Joe Bastardi crying now.....:)
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AbruptSLR

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Re: Is Antarctic sea ice really expanding?
« Reply #17 on: August 07, 2015, 03:59:28 PM »
For those who haven't looked around the forum very much, the following link leads to a thread about the recent Hansen et al 2015 paper that demonstrates not only that ice mass loss from Antarctica is freshening the surface of the Southern Ocean thereby somewhat promoting the growth of Antarctic sea ice, but also that both the greater extend of Antarctic sea ice and the ocean water stratification due to the freshening of the surface water, act as a positivity feedback mechanism by protecting the warm circumpolar deep water, CDW, from the cooling effects of the cold Antarctic atmosphere; thereby allowing the warm CDW to melt still more Antarctic glacial ice mass; that starts the freshening cycle all over again.  Therefore, any long-term trend of increasing Antarctic sea ice extent is clearly a validation of global warming projections.

http://forum.arctic-sea-ice.net/index.php/topic,1327.0.html
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AbruptSLR

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Re: Is Antarctic sea ice really expanding?
« Reply #18 on: August 08, 2015, 06:03:19 PM »
While I tend to agree with Hansen et al 2015's argument that the recent freshening of the Southern Ocean surface waters due to ice meltwater is contributing to the recent trend for increasing Antarctic Sea Ice Extent; nevertheless, the following linked reference draws attention to the key role played by the ASL on sea ice formation in the Ross Sea Sector; and that the currently observed trending of increasing Antarctic Sea Ice Extent may fall within the range of natural variability:


John Turner, J. Scott Hosking, Thomas J. Bracegirdle, Gareth J. Marshall, Tony Phillips (July 2015), "Recent changes in Antarctic Sea Ice", Philosophical Transactions A, Volume: 373 Issue: 2045, DOI: 10.1098/rsta.2014.0163


http://rsta.royalsocietypublishing.org/content/373/2045/20140163


Abstract: "In contrast to the Arctic, total sea ice extent (SIE) across the Southern Ocean has increased since the late 1970s, with the annual mean increasing at a rate of 186×103 km2 per decade (1.5% per decade; p<0.01) for 1979–2013. However, this overall increase masks larger regional variations, most notably an increase (decrease) over the Ross (Amundsen–Bellingshausen) Sea. Sea ice variability results from changes in atmospheric and oceanic conditions, although the former is thought to be more significant, since there is a high correlation between anomalies in the ice concentration and the near-surface wind field. The Southern Ocean SIE trend is dominated by the increase in the Ross Sea sector, where the SIE is significantly correlated with the depth of the Amundsen Sea Low (ASL), which has deepened since 1979. The depth of the ASL is influenced by a number of external factors, including tropical sea surface temperatures, but the low also has a large locally driven intrinsic variability, suggesting that SIE in these areas is especially variable. Many of the current generation of coupled climate models have difficulty in simulating sea ice. However, output from the better-performing IPCC CMIP5 models suggests that the recent increase in Antarctic SIE may be within the bounds of intrinsic/internal variability."
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Gray-Wolf

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Re: Is Antarctic sea ice really expanding?
« Reply #19 on: August 08, 2015, 11:04:23 PM »
Bumpity bump bump

It's looking like it could be a low max down south this year.



And area keeps on dropping ! I imagine it is the uptick in storms that nino is forcing ( or is it???) but we now sit 100,000 above average??? Where is the deniers 'see saw' now? Another big storm into Ross or Weddell and we see below average ice there ( whilst the Arctic sits over 1.5 million below average!!!)

If PDO has now flipped back positive what if we find we'd been Globally sat under a negative forcing since the early 80's ( when Antarctic ice first rebounded from its losses?) and that the north reacted slower to the 'cool down'  due to land mass distribution/pollution levels etc.?)??? Now that would be very bad seeing as our fastest warming rates , to date, were within that 'cooling' period???
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AbruptSLR

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Re: Is Antarctic sea ice really expanding?
« Reply #20 on: August 08, 2015, 11:16:34 PM »
Bumpity bump bump

It's looking like it could be a low max down south this year.

And area keeps on dropping ! I imagine it is the uptick in storms that nino is forcing ( or is it???) but we now sit 100,000 above average??? Where is the deniers 'see saw' now? Another big storm into Ross or Weddell and we see below average ice there ( whilst the Arctic sits over 1.5 million below average!!!)

If PDO has now flipped back positive what if we find we'd been Globally sat under a negative forcing since the early 80's ( when Antarctic ice first rebounded from its losses?) and that the north reacted slower to the 'cool down'  due to land mass distribution/pollution levels etc.?)??? Now that would be very bad seeing as our fastest warming rates , to date, were within that 'cooling' period???

Gray-Wolf,

I concur with your concern that the climate response has been muted (masked) for at least several decades; and that we are about to experience a near "perfect storm" of exaggerated response that could kick the mean global surface temperature up to 2C above pre-industrial circa 2030 to 2035.

Best,
ASLR
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crandles

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Re: Is Antarctic sea ice really expanding?
« Reply #21 on: August 09, 2015, 11:33:46 AM »
CT area

2015.5945   0.1144868  14.1661358

lowest anomaly since
2012.8274   0.1090555  14.0070963

so lowest for 2.75 years.

Only 5 k above that - get below that and it is
2012.6548   0.0283696  14.8321457
2012.6576   0.1053960  14.9610529

which are close to 3 years ago.

Buddy

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Re: Is Antarctic sea ice really expanding?
« Reply #22 on: August 09, 2015, 11:42:29 AM »
Probably no accident that 2012 was the last time this occurred.  Will be interesting to see how low it goes.  With total sea ice approaching the levels of 2012.....that obviously sets the table for oceans to soak up even more heat from the sun.  NOT GOOD......
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crandles

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Re: Is Antarctic sea ice really expanding?
« Reply #23 on: August 09, 2015, 12:21:05 PM »
Probably no accident that 2012 was the last time this occurred. 

It is a long way from arctic sea ice to antarctic sea ice if that was what you were implying. What possible mechanism could there be? Wouldn't it be more prudent to look for (and find) correlation in other years before suggesting this is 'no accident'?

crandles

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Re: Is Antarctic sea ice really expanding?
« Reply #24 on: August 09, 2015, 12:29:12 PM »
that obviously sets the table for oceans to soak up even more heat from the sun.  NOT GOOD......

possibly but there isn't much sun shining in the south at the moment and 2015 has had some of the highest positive anomalies on record while there was sun shining strongly there.

Maybe the low positive anomalies will continue but if the anomalies have swung so far so fast who is tt say they won't swing back again?

Paddy

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Re: Is Antarctic sea ice really expanding?
« Reply #25 on: August 09, 2015, 12:46:56 PM »
Indeed, it's only been a month or so with the extent curve (and area curve) flattening off.  Let's not get ahead of ourselves here. 

Especially as the global sea ice area has only registered a brief blip below the average line so far, which is nothing unprecedented:


Gray-Wolf

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Re: Is Antarctic sea ice really expanding?
« Reply #26 on: August 09, 2015, 12:49:10 PM »
If the areas that the ice factory were expanding into are becoming more perturbed this year then no matter how much ice floats out that way the ocean will gobble it up!

One of the elements of the expansion of the antarctic pack was stronger winds off the continent so maybe we are also seeing impacts there from the ENSO configuration?

 
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Paddy

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Re: Is Antarctic sea ice really expanding?
« Reply #27 on: August 09, 2015, 01:37:21 PM »
The August 5th publication of Arctic Sea Ice News has a bit of discussion about the slowdown up to that date, incidentally.  They don't make any explicit forecasts about future trends, but note the final statement in bold:

Quote
Relatively warm conditions prevailed for much of the month in the two regions of ice edge retreat, the northern Weddell Sea and northwestern Ross Sea, with average air temperatures at the 925 hPa level (3,000 feet above sea level) at approximately 4 degrees Celsius (7 degrees Fahrenheit) above average. However, sea surface temperatures just north of the ice edge were 0.5 to 1 degree Celsius (1 to 2 degrees Fahrenheit) cooler than average, raising the potential for rapid ice growth through the remainder of the winter season.


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Re: Is Antarctic sea ice really expanding?
« Reply #28 on: August 09, 2015, 02:26:07 PM »
Quote
It is a long way from arctic sea ice to antarctic sea ice if that was what you were implying. What possible mechanism could there be?

Yes it is a long way.  But EVERYTHING on the planet is affected to some degree by EVERYTHING else.....especially when they are connected by the same oceans.

We now have TWO RECENT occasions where an extremely low Arctic ice sheet being "accompanied" by a relatively low Antarctic sea ice (relatively low over the last 10 years).  Could it be just a "chance" happening?  Sure...it COULD.

I know that the "science types" (probably like yourself) are "conservative" in their approach.  And I understand that.....although I think there has been TOO MUCH conservatism by the science community as a whole regarding global warming (Anthropogenic Climate Change).

The oceans have continued to warm up....and we are CONTINUING to lose ice volume on all 3 major ice sheets....QUICKLY.  I don't see that it is LIKELY a "coincidence" that the Arctic ice sheet is near an all time low.....at the same time that the Antarctic sea ice is at levels not seen since 2012.

I happen to be in the camp (and have been for several years) that thinks we will have a MOSTLY MELTED Arctic ice sheet in September of 2016 (mostly melted EXCEPT for a few hundred mile wide stretch of ice off shore from the Canadian Archipelago to northeast Greenland).  I also "expect" that atmospheric temperatures will begin to rise more quickly than the past 30 or so years (no....not "Al Gore" quickly....but more quickly than before).  In fact....that rise may already be happening.

I think the time for "conservatism" from some of the science community has gone on for too long.  That does NOT mean that you (scientists) "throw out" your standards.  But it DOES mean that scientists take a harder look at reality....and also understand that there are people and organizations that are USING THE CONSERVATIVE APPROACH by some scientists, to lengthen the time we keep pouring CO2 into the atmosphere.


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crandles

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Re: Is Antarctic sea ice really expanding?
« Reply #29 on: August 09, 2015, 03:20:42 PM »
Sorry but I think we will just have to agree to disagree.

We know trend in Antarctic sea ice is upwards and we know major causes of this include ozone loss moving atmospheric cells and strengthened winds from Antarctica. These do not play any significant role in arctic sea ice. Different driving causes makes coincidence more likely and some unknown link much less likely.

A new recent low from reduction in Katabatic winds sounds quite plausible as does more perturbed ocean. To me these seem more likely to be coincidental with 2012 Arctic sea ice low. Certainly more likely than wanting to make me jump to a conclusion of some unknown link.

If there was some connection, particularly if oceans involved, wouldn't a time lag be likely? Therefore isn't it happening at the wrong time to suggest some unknown connection via oceans?


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Re: Is Antarctic sea ice really expanding?
« Reply #30 on: August 09, 2015, 04:19:26 PM »
Assuming the Hansen research is correct and the Antarctic ice is growing (the shift in measurement making it seem that it is growing faster than it actually is), there has to be an upper limit as this  expanding ice pushes further north into the southern ocean. At some point this expanded sea ice will fluctuate rapidly as it becomes more dependent on the vagaries of the weather.

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Re: Is Antarctic sea ice really expanding?
« Reply #31 on: August 09, 2015, 05:18:48 PM »
2015.5973   0.0790655  14.1893225

so lowest anomaly for 2.94 years since

2012.6548   0.0283696  14.8321457

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Re: Is Antarctic sea ice really expanding?
« Reply #32 on: August 09, 2015, 05:34:16 PM »
Quote
Sorry but I think we will just have to agree to disagree.

That's OK.  Disagreement is HEALTHY for science (even from NON Scientists such as myself:).  As long as it is constructive....I certainly have NO PROBLEM with that.  And you are CERTAINLY CONSTRUCTIVE....and I appreciate that.

Quote
If there was some connection, particularly if oceans involved, wouldn't a time lag be likely? Therefore isn't it happening at the wrong time to suggest some unknown connection via oceans?

I think there IS a connection.  Certainly for MANY MONTHS...the equatorial Pacific has been warm as El Nino has strengthened...and SOME of that water has been making its way down south.  As well....the warm "blob" off the west coast of the US has been steadfast and no doubt affecting the Arctic. The Pacific Ocean IN GENERAL is toasty (just ask Japan with their own "warm blob" off of their coast).

The next 13 months will be fascinating (I think even more fascinating than the past 5 years).  Remember....we are only really at the "beginning" of changes that will be more rapid as the Arctic has more and more "dark ocean".....for longer and longer periods of time.  Just think what things will be like 10 years from now.

The "direction" of where we are headed is CLEAR....how FAST we go in that direction is somewhat muddled.....but I believe the SPEED of that change is going to be kicked up a notch from where we have been.

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Re: Is Antarctic sea ice really expanding?
« Reply #33 on: August 10, 2015, 01:37:46 PM »
As I tried to explain in Reply #18, I believe that the current downward fluctuation in Antarctic Sea Ice Extent if likely associated with the influence of our currently strong El Nino on the average location of the Amundsen Bellingshausen Sea Low, ABSL.

As discussed in both the reference in Reply #18 & the immediate following linked reference, during the satellite era the ABSL has largely been more westward (i.e. it is now more frequently centered nearer the eastern side of the Ross Sea where it more frequently promotes sea ice production) than its historic mean local (which is historically nearer to the ASE).  Thus as we have now entered a positive PDO cycle, we can expect the ABSL to more frequently reposition eastward (back towards the Amundsen & Bellingshausen Seas). Indeed, during La Nina the ABSL is on average moved more westward closer to 140W, while during El Nino's the ABSL is on average moved more eastward closer to about 115W.  The attached figure from Bertler et al 2006 (see reference at bottom of this post), which shows pictorially the relationship between the location of the Amundsen Sea Low (or Amundsen Bellingshausen Sea Low), ASL (or ABSL) and either a La Nina or an El Nino event.

Nerilie J. Abram, Robert Mulvaney, Françoise Vimeux, Steven J. Phipps, John Turner and Matthew H. England, (2014), "Evolution of the Southern Annular Mode during the past millennium", Nature Clim. Change (2014); doi:10.1038/nclimate2235

http://www.nature.com/nclimate/journal/v4/n7/full/nclimate2235.html

Abstract: "The Southern Annular Mode (SAM) is the primary pattern of climate variability in the Southern Hemisphere, influencing latitudinal rainfall distribution and temperatures from the subtropics to Antarctica. The positive summer trend in the SAM over recent decades is widely attributed to stratospheric ozone depletion; however, the brevity of observational records from Antarctica—one of the core zones that defines SAM variability—limits our understanding of long-term SAM behaviour. Here we reconstruct annual mean changes in the SAM since AD 1000 using, for the first time, proxy records that encompass the full mid-latitude to polar domain across the Drake Passage sector. We find that the SAM has undergone a progressive shift towards its positive phase since the 15th century, causing cooling of the main Antarctic continent at the same time that the Antarctic Peninsula has warmed. The positive trend in the SAM since ~AD 1940 is reproduced by multimodel climate simulations forced with rising greenhouse gas levels and later ozone depletion, and the long-term average SAM index is now at its highest level for at least the past 1,000 years. Reconstructed SAM trends before the 20th century are more prominent than those in radiative-forcing climate experiments and may be associated with a teleconnected response to tropical Pacific climate. Our findings imply that predictions of further greenhouse-driven increases in the SAM over the coming century also need to account for the possibility of opposing effects from tropical Pacific climate changes."




Bertler, N.A., Naish, T.T., Mayewski, P.A. and Barrett, P.J., (2006), "Opposing oceanic and atmospheric ENSO influences on the Ross Sea Region, Antarctica", Advances in Geosciences, 6, pp 83-88, SRef-ID: 1680-7359/adgeo/2006-6-83.
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Re: Is Antarctic sea ice really expanding?
« Reply #34 on: August 11, 2015, 12:24:14 AM »
The attached plot issued today by The Cryosphere Today compares the Antarctic Sea Ice Extent this year ( Yellow Line to August 10 2015) as compare to the last super El Nino years of 1997-98; showing that they are currently in-line with each other.
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Re: Is Antarctic sea ice really expanding?
« Reply #35 on: August 11, 2015, 02:46:19 PM »
Anomaly keeps falling.

2015.6028  -0.0573669  14.1879416

First negative anomaly since
2011.8932  -0.1083351  11.2528648

(so lowest anomaly for 3.7 years)

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Re: Is Antarctic sea ice really expanding?
« Reply #36 on: August 14, 2015, 01:09:43 PM »
Quote
Anomaly keeps falling.

And here I was ready to "hibernate" for the winter and enjoy college football....but now it looks like we might have some interesting things happening in Antarctica over the next several months....

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Re: Is Antarctic sea ice really expanding?
« Reply #37 on: August 14, 2015, 02:52:33 PM »
From day 192
2015.5260   1.2492539  13.8355932
2nd highest on record

to
day 223
2015.6110  -0.2790617  14.0633211
6th lowest on record

gain of only 228k in 31 days. That is less than 7.5k gain a day on average.

(2014 went from 13.413 to 15.635 a gain of 1.222 or 5.36 times the amount of gain.)

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Re: Is Antarctic sea ice really expanding?
« Reply #38 on: August 15, 2015, 01:27:37 PM »
Casual speculation: the normal maximum is in a little under 40 days and would be about 15 million, right?  (Based on eyeballing the Cryosphere graph).  Which means that if the antarctic ice area stays flat at about 14 million for the next 30 or 40 days (big if), we could end up with a negative anomaly of about 1 million.  Potentially larger if it starts dropping earlier than usual.

But then, I've no idea what it's likely to do next, or if there's anything to stop the Antarctic ice area going back up as fast as it went down.

EDIT: Meanwhile, it looks like the global sea ice anomaly is down to nearly -2 million sq km already:

« Last Edit: August 16, 2015, 03:20:20 PM by Paddy »

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Re: Is Antarctic sea ice really expanding?
« Reply #39 on: August 16, 2015, 05:55:52 PM »
The beat goes on.  Antarctic sea ice extent continues to level off.....

Anyone know when the last time the Antarctic sea ice was below 2 standard deviations?

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Re: Is Antarctic sea ice really expanding?
« Reply #40 on: August 16, 2015, 06:48:59 PM »
The beat goes on.  Antarctic sea ice extent continues to level off.....

Anyone know when the last time the Antarctic sea ice was below 2 standard deviations?

2011 was second lowest for CT area for the date on a few dates. That is less than 5% of years below it, so probably then. (I haven't done any calculations to confirm this and it may not be the case particularly if the values are spread out over the range rather than being bunched in the middle.)

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Re: Is Antarctic sea ice really expanding?
« Reply #41 on: August 17, 2015, 01:54:51 PM »
Here is a Cryosphere Today graphic.  It shows that 2002 and 1986 were the "record lows" since 1979.  We are currently only about 300,000 2km above that record low.

http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html

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crandles

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Re: Is Antarctic sea ice really expanding?
« Reply #42 on: August 23, 2015, 01:37:36 PM »
2015.6356  -0.5839444  14.0029554

Now lowest anomaly since

2011.5397  -0.6641924  12.3286848
(i.e. over 4years)

Also it is second lowest for day after 2002 and unless more than 74k is gained in next day, could become lowest for date.

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Re: Is Antarctic sea ice really expanding?
« Reply #43 on: August 23, 2015, 02:28:09 PM »
Here is a chart by "sunshinehours.wordpress.com".  It is the FIFTH graphic down on the following page:

http://climatechangegraphs.blogspot.com/2012/08/arctic-sea-ice-volume-extent-charts_30.html

Or if you want to go directly to his charts....here is his link (second chart down on his page):

https://sunshinehours.wordpress.com/

He is a couple days behind....it looks like he must take the weekend off:).  But his chart(s) clearly show that the Antarctic sea ice has "stalled".

There are going to be some mighty worried climate scientists if the Antarctic sea ice keeps in a "stall"....and begins to fall below the - 2 standard deviation line soon (not that they aren't ALREADY WORRIED).....



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Re: Is Antarctic sea ice really expanding?
« Reply #44 on: August 23, 2015, 02:36:55 PM »
2015.6356  -0.5839444  14.0029554

Now lowest anomaly since

2011.5397  -0.6641924  12.3286848
(i.e. over 4years)

Also it is second lowest for day after 2002 and unless more than 74k is gained in next day, could become lowest for date.

This volatility is simply insane. Why on Earth do climate risk deniers use Antarctic sea ice as an argument for anything?

Speaking of which: Buddy, I believe that sunshinehours blog is run by a climate risk denier. Doesn't mean his graphs are worth- or useless, but beware when linking.
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Re: Is Antarctic sea ice really expanding?
« Reply #45 on: August 23, 2015, 02:57:29 PM »
Quote
Speaking of which: Buddy, I believe that sunshinehours blog is run by a climate risk denier. Doesn't mean his graphs are worth- or useless, but beware when linking.

Thanks....and duly noted.  This could be fun ;D
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Re: Is Antarctic sea ice really expanding?
« Reply #46 on: August 23, 2015, 04:36:43 PM »
I haven't read all the posts, but I'm pretty sure (and I've heard Antarctic scientists say the same) the ice melting off of the icesheet, sits on top of the sea, and being fresh water, less dense, spreads out on top in a cold layer of water, and re-freezes in a cold snap as thin ice, making it look like more area. Therefore, when you see a lot of melt off the ice sheet, but bigger area, that's a bad sign, not a good sign.

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Re: Is Antarctic sea ice really expanding?
« Reply #47 on: August 23, 2015, 06:04:40 PM »
but bigger area, that's a bad sign, not a good sign.

and when we see low area like now, is that a good sign, also a bad sign, or a worse sign?

With a strong El Nino being likely, how low will the next minimum be?

Under 1m Km^2 ?
Under 0.5m Km^2 ?


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Re: Is Antarctic sea ice really expanding?
« Reply #48 on: August 23, 2015, 06:32:39 PM »
but bigger area, that's a bad sign, not a good sign.

and when we see low area like now, is that a good sign, also a bad sign, or a worse sign?

With a strong El Nino being likely, how low will the next minimum be?

Under 1m Km^2 ?
Under 0.5m Km^2 ?

Science offers a third option besides simply talking about short-term variability versus long-term trends.  Science says that both can be happening at the same time, with the ENSO cycle being one of the stronger short-term variables, and with glacial ice meltwater being one of the stronger long-term factors.  For example, the recent long-term trend for increasing Antarctic sea ice extent has characteristically included abnormally large extents of sea ice in the Ross Sea area due to the ASL typically being positioned to blow sea ice northward so as to make room for more sea ice to form behind it.  However, during a strong El Nino the ASL characteristically shifts eastward resulting in an abnormally low amount of sea ice in the Ross Sea (see first attached image) and stronger winds pushing more warm CDW into the ASE to accelerate glacial ice melting.

Thus by this line of logic, science offers us the probability that our current condition of an El Nino induced low in Antarctic sea ice extent is "very bad" for human society as it is likely destabilizing the ASE marine glaciers and accelerating the freshening of the Southern Ocean and may likely be followed by a La Nina event in the austral spring of 2016 that could have record high levels of Antarctic sea ice extent that could: (a) promote higher than average snowfall on the sea ice and an associated low snowfall on land; and (b) could promote a further slowdown of the AMOC which would trap abnormally high amounts of heat in the ocean (as the sea ice would reduce venting of heat from the Southern Ocean into space).
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Re: Is Antarctic sea ice really expanding?
« Reply #49 on: August 24, 2015, 01:06:20 AM »
crandles
and when we see low area like now, is that a good sign, also a bad sign, or a worse sign?
A low winter minimum is obviously a bad sign, but in order for the ice to expand in area, you need it to melt first, then refreeze on the sea surface later. It is not warm enough yet to melt yet this year. So towards the end of the melting season, if melting of icesheet continues as expected, and when re-freeze begins, I presume you would get more thin ice frozen on top of the sea.
Let me ask you this:
Does fresh water float on top of salt water?
Is fresh water, recently melted, colder than the sea upon which it lands?
Does it being cold, make it more susceptible to re-freeze?
Does fresh water freeze at a higher temperature than salt water?

It is a mainstream theory: http://www.latimes.com/science/la-sci-antarctic-sea-ice-20140830-story.html

crandles
Quote
With a strong El Nino being likely, how low will the next minimum be?
El Nino will not be as strong as being predicted, and will not slow melting in the Antarctic.

crandles
Quote
Under 1m Km^2 ?
Under 0.5m Km^2 ?
I have no clue.
« Last Edit: August 24, 2015, 01:49:09 PM by Gonzo »