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Author Topic: Antarctic Sea Ice Extent and Area  (Read 979850 times)

Wipneus

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Re: Sea Ice Extent around Antarctica
« Reply #750 on: October 27, 2017, 08:29:06 AM »
Updating NSIDC NT extent and area: the way down has not really been found yet.

Unfortunately posting any graph gives:

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Wipneus

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Re: Sea Ice Extent around Antarctica
« Reply #751 on: October 27, 2017, 03:13:51 PM »
Well, today both graphs seem to be accepted. Same comment: no on the way down yet.

steve s

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Re: Sea Ice Extent around Antarctica
« Reply #752 on: October 27, 2017, 11:24:53 PM »
Is there any time series tracking ice thickness or volume?

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Re: Sea Ice Extent around Antarctica
« Reply #753 on: October 28, 2017, 02:58:20 PM »
Is there any time series tracking ice thickness or volume?
I have not found one. Perhaps 'tis because most Antarctic sea ice is First year, i.e. melts every year.

JAXA DATA

So far the story this year (to 27th October) is of very low extent loss since maximum, being 0.61 million km2 as opposed to the 10 year average of 1.19 million km2. This is the opposite of 2016, which had an extent loss of 1.8 million km2 by this date.
Only 2008-09 had a lower extent loss (0.47 million km2) at this date.
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Re: Sea Ice Extent around Antarctica
« Reply #754 on: October 31, 2017, 03:36:47 PM »
Has the Antarctic melting season got properly underway at last?
We are almost at the point when 2016 melting went doo-lally. What will happen this year?
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #755 on: November 05, 2017, 03:20:17 PM »
JAXA DATA

the Antarctic melting season HAS got properly underway at last, but whether it will match 2016 is very much an open question.
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Re: Sea Ice Extent around Antarctica
« Reply #756 on: November 06, 2017, 12:49:13 PM »
JAXA DATA

On this date one year ago Antarctic sea ice extent became the lowest in the satellite record. At the moment this is not being repeated.

On 6th October 2017 extent exceeded 2016 extent by 51,815 km2. That difference has increased to 707,854 km2 (4.4%). (5th November extent is 16,696,169 km2).
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Wipneus

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Re: Sea Ice Extent around Antarctica
« Reply #757 on: November 06, 2017, 04:45:09 PM »
Update of the NSIDC NT extent and area graphs. The way down has been found, area is among the lowest years again.

Pavel

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Re: Sea Ice Extent around Antarctica
« Reply #758 on: November 10, 2017, 08:40:56 AM »
Hycom thickness product is now available for Antarctica

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #759 on: November 10, 2017, 01:28:35 PM »
Hycom thickness product is now available for Antarctica
Gosh - that is rather good - thick ice and strong northward drift  along Larsen C and then North East out of the Weddel Sea? Due to Weddell Sea Gyre posted by AbruptSLR?
Meanwhile:-
JAXA DATA

Average extent loss per day 125K km2 for the last 6 days. But not as much as 2016.

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Re: Sea Ice Extent around Antarctica
« Reply #760 on: November 14, 2017, 02:10:23 PM »
JAXA DATA

Antarctic sea ice extent continues to decline at well above average but below that of 2016. The table below shows the variation compared with the previous 3 years. Extent at  15,510,324 km2 is some 270,000 less than the low year of 2002, but to put this in perspective, this is about 2 days average extent loss at this time of year.
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Wipneus

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Re: Sea Ice Extent around Antarctica
« Reply #761 on: November 14, 2017, 05:03:59 PM »
Updating the NSIDC NT extent and area graphs. Both are second lowest for the day of year (but far above 2016 still).

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Re: Sea Ice Extent around Antarctica
« Reply #762 on: November 20, 2017, 03:32:58 PM »
JAXA DATA as at 19 Nov 2017

Extent loss is still proceeding at well above average, but less than in 2016, which was just under 1.1 million km2 less at this date.
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Re: Sea Ice Extent around Antarctica
« Reply #763 on: November 20, 2017, 03:44:41 PM »
Tough to catch up to 2016's very early start.  But angle of descent is now equal to or even slightly greater than 2016.  PDS (pretty damn steep)....😳
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Re: Sea Ice Extent around Antarctica
« Reply #764 on: November 23, 2017, 01:26:15 PM »
JAXA DATA Antarctic Sea Ice Extent as at 22 Nov 2017.

Extent loss continues above average. The table below suggests a very low extent minimum is possible. However, on average extent loss is only 22% complete.

Note also (Jaxa image below) that the large polynya in the Weddell Sea is about to disappear. Will it reappear in the 2018 freezing season?
« Last Edit: November 23, 2017, 01:32:24 PM by gerontocrat »
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Re: Sea Ice Extent around Antarctica
« Reply #765 on: November 25, 2017, 06:29:12 PM »
So the last couple of years, sea ice progressively gets worse. What could this mean for glaciers? Are we seeing the beginning of a ramp up of ice retreat in Antarctica?

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Re: Sea Ice Extent around Antarctica
« Reply #766 on: December 02, 2017, 03:45:04 PM »
So the last couple of years, sea ice progressively gets worse. What could this mean for glaciers? Are we seeing the beginning of a ramp up of ice retreat in Antarctica?
JAXA DATA as at 30 Nov

With sea ice extent loss only about 30 percent done the outcome is anybody's guess. Hence the fascination. However, we are at maximum insolation in the southern hemisphere, so with extent at 2nd or 3rd lowest some additional warming of surface water is possible - BUT on the other hand apparently this additional open water may also allow upwelling of warmer water from depth to the surface thus reducing melt of the ice shelves and glaciers from underneath.
« Last Edit: December 02, 2017, 03:50:05 PM by gerontocrat »
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Re: Sea Ice Extent around Antarctica
« Reply #767 on: December 03, 2017, 02:12:14 PM »
Image is from NSIDC at 2 Dec.

Weddell sea polynya about to become open sea.
Most of lower than average extent confined to eastern part of Weddell Sea.
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Re: Sea Ice Extent around Antarctica
« Reply #768 on: December 04, 2017, 01:21:33 AM »
Image is from NSIDC at 2 Dec.

Weddell sea polynya about to become open sea.
Most of lower than average extent confined to eastern part of Weddell Sea.

I note that the indicated Antarctic sea ice extent pattern would not be surprising if recent (in the past few years) ice mass loss from Greenland were causing a cold spot in the North Atlantic to cause the MOC to convey more ocean heat to the Weddell Sea region due to the bipolar seesaw mechanism.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #769 on: December 07, 2017, 03:27:38 PM »
JAXA DATA as at 6 Dec 2017

On average just under 40% of extent loss is done (compared with 66% of arctic sea ice gain done).
The table below indicates that if history was a judge (!?) another very low minimum is on the cards.

However the graph below shows how individual years can vary and do vary wildly from the average.

The image from NSIDC also shows the disintegration of the sea ice as maximum melt gets underway, and that extent loss above average  is still mainly confined to the Eastern half of the Weddell Sea.

NOTE:- NSIDC seems to have moved the daily images to http://nsidc.org/arcticseaicenews/2012/05/daily-image/

strange but true.
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Paddy

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Re: Sea Ice Extent around Antarctica
« Reply #770 on: December 11, 2017, 08:49:21 AM »
What was the JAXA 2017 minimum? I'm looking at doing another poll.

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #771 on: December 14, 2017, 10:42:20 PM »
What was the JAXA 2017 minimum? I'm looking at doing another poll.

2,147,345 km2 on 01-Mar

JAXA DATA as at 13 Dec 2017

On average 47% of extent loss is done (compared with 71% of arctic sea ice gain done).

The table below indicates that if history was a judge (!?) another very low minimum is on the cards, but melt is still less than 50% done.

However the graph below shows how individual years can vary and do vary wildly from the average. E.g .in 2016 at this date extent loss was 2 million km2 greater than this year. But then remaining extent loss was 2 million LESS than the average.

The image from NSIDC also shows the continuing rapid disintegration of the sea ice as maximum melt gets underway, and that extent loss above average  is still mainly confined to the Eastern half of the Weddell Sea.
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Re: Sea Ice Extent around Antarctica
« Reply #772 on: December 16, 2017, 02:38:06 AM »
Thank you!
« Last Edit: December 16, 2017, 07:18:26 AM by Paddy »

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #773 on: December 18, 2017, 11:59:40 AM »
JAXA DATA at 17 Dec + NSIDC image at 16 Dec.

On average, extent loss 52 % done.
As the days go by, resulting minimum extent if average remaining melt occurs gradually declines.
All the above average melt is in the Eastern portion of the Weddell Sea (up-welling that created the polynya?) This could mean extent loss slows as Eastern Weddell Sea becomes ice free.
« Last Edit: December 18, 2017, 05:12:56 PM by gerontocrat »
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Lord M Vader

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Re: Sea Ice Extent around Antarctica
« Reply #774 on: December 18, 2017, 05:47:40 PM »
A triple century break today is not happening everyday... Down 340K is not too bad, right? ;)

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Re: Sea Ice Extent around Antarctica
« Reply #775 on: December 19, 2017, 05:31:36 AM »
   .    .    but if the Eastern Weddell Sea is more open it could absorb more solar radiation and warm? - and the ice that "usually" melts is still available to melt and reduce area/extent to new records?

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #776 on: December 20, 2017, 02:24:40 PM »
   .    .    but if the Eastern Weddell Sea is more open it could absorb more solar radiation and warm? - and the ice that "usually" melts is still available to melt and reduce area/extent to new records?
Lower than average sea-ice extent is obviously a positive feedback for global warming as open water absorbs most solar radiation while sea ice reflects most solar radiation.This is especially true at this time of year in the S Hemisphere as insolation is at maximum.

But this does not necessarily increase melt in other parts of the Antarctic Ocean. Also the less sea ice there is the less remains to melt and maybe in colder parts of the ocean. This was especially marked from this time last year until the minimum in early 2017. (See the 2016-17 line in the graph below.) One watches and waits.

« Last Edit: December 20, 2017, 04:42:08 PM by gerontocrat »
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Re: Sea Ice Extent around Antarctica
« Reply #777 on: December 27, 2017, 01:36:02 PM »
JAXA DATA as at 26 December + NSIDC image

Extent loss on average 64 percent done.
History still favours a new record low (BUT......)
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #778 on: December 31, 2017, 06:00:18 PM »
JAXA DATA as at 30 Dec 2017

Extent loss 70 percent done.
The second table is just a reminder that although extent is nearly 1 million km2 above 2016, the trend is still very much down.
The graph shows that there is only about 50 days to go.
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Re: Sea Ice Extent around Antarctica
« Reply #779 on: January 06, 2018, 08:08:54 PM »
JAXA Images are up-to-date, but JAXA still not showing the graphs and the data for 2018, so I had a look at the NSIDC daily data spreadsheet.

Extent loss still pretty much on course.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #780 on: January 09, 2018, 06:29:59 PM »
Herewith an image from NSIDC. Impressive extent and concentration loss. Temperature anomalies over the sea ice have not been much and often negative, so something is happening in the oceans?

Note that obstinate lump of ice in the SW Weddell Sea that Hycom says is thick ice.
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Nikita

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Re: Sea Ice Extent around Antarctica
« Reply #781 on: January 10, 2018, 06:39:32 AM »
...
« Last Edit: January 10, 2018, 06:55:00 AM by Nikita »

FredBear

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Re: Sea Ice Extent around Antarctica
« Reply #782 on: January 10, 2018, 11:34:15 AM »
You can see a line of four "large' icebergs drifting slowly away from the tip of the Antarctic Peninsular towards South Georgia in the previous picture!

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #783 on: January 10, 2018, 01:44:48 PM »
JAXA DATA AS AT 9 JAN 2018.   Like General MacArthur, it has returned.

Extent loss on average is 80% done. There is a lot of low concentration ice that should disappear but also lumps of thick ice,the biggest in the SW of the Weddell Sea.

Historical data does point to a record low, and last year remaining melt was below average.
But .....there is a but.
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #784 on: January 13, 2018, 12:28:52 PM »
JAXA DATA AS AT 12 JAN 2018.

 
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #785 on: January 15, 2018, 05:03:09 PM »
The Antarctic animations from HYCOM are worth a look. (Arctic animations are not up to date)

https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/antarcictn_nowcast_anim30d.gif

The animation is for 30 days to the 12th January and shows well the disintegration of sea ice, and where the remaining thick ice is.

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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #786 on: January 19, 2018, 10:23:40 AM »
JAXA DATA AS AT 18 JAN

Extent loss on average is 88% done, but the table shows that historically the range of the final result is high. However, remaining ice is mostly relatively thick ice, the main lump still in the SW of the Weddell Sea, and not a lot of weather and drift to break it up. (Larsen C is, of course, in the middle of that).

Nevertheless, data points more to a record low than a result greater than 2017, even though currently extent is 0.5 million km2 more.
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oren

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Re: Sea Ice Extent around Antarctica
« Reply #787 on: January 19, 2018, 10:41:38 AM »
JAXA DATA AS AT 18 JAN
Nevertheless, data points more to a record low than a result greater than 2017, even though currently extent is 0.5 million km2 more.
The average loss to minimum can be misleading, as the less ice remains the less ice there is to lose. When a sub-region gets to zero, it can't continue along the historical average trajectory. So I doubt that the true probability leans more towards a record minimum. Of course, this requires a much more detailed analysis so these are just general musings.
BTW, thank you for your consistent JAXA updates.

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #788 on: January 19, 2018, 11:27:08 AM »
JAXA DATA AS AT 18 JAN
Nevertheless, data points more to a record low than a result greater than 2017, even though currently extent is 0.5 million km2 more.
The average loss to minimum can be misleading, as the less ice remains the less ice there is to lose. When a sub-region gets to zero, it can't continue along the historical average trajectory. So I doubt that the true probability leans more towards a record minimum.

HYCOM shows it well in its 30 day animation, especially the the main lump of thick ice still in the SW of the Weddell Sea, with not a lot of weather and drift to break it up.

(https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/antarc.html)

Click on image to make it work.
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Re: Sea Ice Extent around Antarctica
« Reply #789 on: January 20, 2018, 03:31:51 PM »
so I guess/ fear that except for Weddel sea almost all other sea ice will probably be gone at the end of melting season...

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Re: Sea Ice Extent around Antarctica
« Reply #790 on: January 20, 2018, 07:28:15 PM »
RikW,
That is almost always true.  Most Antarctic sea ice is first year ice (FYI).
From the ASI Graphs page.
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

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Re: Sea Ice Extent around Antarctica
« Reply #791 on: January 20, 2018, 09:36:58 PM »
I think that a new record is possible.

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Re: Sea Ice Extent around Antarctica
« Reply #792 on: January 20, 2018, 10:47:42 PM »
Nikita, it should depend upon how much of the remaining ice melts out in Ross Sea and the adjacent area. If all that ice melts out a new record low minimum is certainly possible. The ice that lingers west of the Antarctic peninsula is quite thick and should survive this melting season too.

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Re: Sea Ice Extent around Antarctica
« Reply #793 on: January 22, 2018, 05:40:21 PM »
Sea ice extent around Antarctica continues to be second lowest for the date. As of January 21, the SIE was 3,595 Mn km2. That also means that we are now ahead of the minimums in 2013, 2008 and 2003 with about a month or so remaining of the melting season.

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Re: Sea Ice Extent around Antarctica
« Reply #794 on: January 22, 2018, 07:46:42 PM »
JAXA DATA paints an even more impressive picture. At 21 Jan SIE lower than the minima for 2003, 2008, 2013, 2014, and 2015. On average  1.5 million km2 additional extent loss to come (but.....)
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Re: Sea Ice Extent around Antarctica
« Reply #795 on: January 22, 2018, 10:00:33 PM »
No model, no glory, Sleepy.  ;D
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Re: Sea Ice Extent around Antarctica
« Reply #796 on: January 23, 2018, 02:19:47 PM »
JAXA DATA AS AT 21 JAN

Extent loss on average is 91% done, with just with on average 1.4 million km2 of extent loss and 30 days to go, (a maximum extent loss of 2 million (2014-15) and a minimum of 0.8 million (2016-17) ).   So the range of the minimum final result is high, the average being just under 2 million km2, which would be a second record low in a row. 2018 extent is still 0.4 million greater than 2017 on this date.

Remaining ice is mostly relatively thick ice, the main lump still in the SW of the Weddell Sea, and not a lot of weather and drift to break it up. (Larsen C is, of course, in the middle of that). Perhaps this indicates a lower than average remaining extent loss - perhaps not.

Air temperatures have been and are still below zero in the melt areas, but this has not stopped melting. But what are ocean temperatures at depth up to ? (NO DATA ?)
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Adam Ash

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Re: Sea Ice Extent around Antarctica
« Reply #797 on: January 24, 2018, 12:44:33 AM »
Record high sea temperatures in the Tasman Sea, and also record air temps.  Invercargill (46 South) has been hotter than Jakarta recently!

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #798 on: January 24, 2018, 01:26:46 PM »
Record high sea temperatures in the Tasman Sea, and also record air temps.  Invercargill (46 South) has been hotter than Jakarta recently!
The Antarctic circumpolar winds stop warm air getting close to the Antarctic shore?
If that polar vortex collapsed (as in the Arctic) would that be a complete game changer?
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Sleepy

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Re: Sea Ice Extent around Antarctica
« Reply #799 on: January 24, 2018, 02:05:03 PM »
Yes but there are some huge differences compared to the Arctic. No mountain ranges that aid stratospheric warmings through planetary waves like in the NH. The Antarctic circumpolar current (the largest on the planet) effectively isolates Antarctica, and there's still some ice down there, even if it has started to move rather disturbingly in recent years. The Antarctic polar vortex is less disturbed, colder and persists longer and will hopefully continue to do so for a very long time.
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