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RealityCheck

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Re: Sea Ice Extent around Antarctica
« Reply #1200 on: April 20, 2019, 06:53:14 AM »
Morning G
Think you grabbed the wrong graphs for the last post, maybe?
Thanks for ongoing daily updates, by the way...
RC
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1201 on: April 20, 2019, 07:45:50 AM »
Morning G
Think you grabbed the wrong graphs for the last post, maybe?
Thanks for ongoing daily updates, by the way...
RC
Perhaps I should wake up properly before posting. Insomnia is a bitch.
Thanks for spotting it.
"Para a Causa do Povo a Luta Continua!"
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RealityCheck

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Re: Sea Ice Extent around Antarctica
« Reply #1202 on: April 20, 2019, 10:25:49 PM »
Yeah. The 5am starts get tiresome after a while... 😁
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1203 on: April 23, 2019, 08:52:51 AM »
JAXA ANTARCTIC Sea Ice Extent : 6,144,932 km2(April 22, 2019)

In the last 3 days, extent gain has been below average to the extent that 2019 extent is lowest in the satellite record for the 14th time this year , for the first time since January 14.

- Extent GAIN on this day 46k, 39 k less than the average gain of 85 k on this day.
- Extent is lowest in the satellite record for this day, 31 k less than extent on this day in 2017.
-  Extent gain from minimum is 3.720 million km2, 1,203 3.720 million km2 (24%) less than the average of 4,923 3.720 million km2 by this day,
- 30.0% of average extent gain done, with 147 days to average date of maximum (16 Sept),

The Perils of Projections
Remaining average freeze of last 10 years gives a max of 17.37 million km2, 0.70 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
I will only be posting occasional updates from now on unless something of note occurs.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

RoxTheGeologist

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Re: Sea Ice Extent around Antarctica
« Reply #1204 on: April 23, 2019, 09:39:45 PM »

I guess that means global sea ice must be at an all time low, as both the Arctic and Antarctica are at all time lows.

magnamentis

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Re: Sea Ice Extent around Antarctica
« Reply #1205 on: April 23, 2019, 10:12:50 PM »

I guess that means global sea ice must be at an all time low, as both the Arctic and Antarctica are at all time lows.

it is for the last few days, gap increasing
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1206 on: April 24, 2019, 11:36:17 AM »
JAXA ANTARCTIC Sea Ice Extent : 6,297,153 km2(April 23, 2019)

Large extent gain, 2019 extent back to 2nd lowest in the satellite record by 10k.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1207 on: April 27, 2019, 01:02:29 PM »
JAXA ANTARCTIC Sea Ice Extent : 6,574,331 km2(April 26, 2019)

Extent gain back to below average so 2019 extent is lowest in the satellite record again (for the 17th time this year).
- Extent GAIN on this day 70k, 36 k less than the average gain of 106 k on this day.
- Extent is lowest in the satellite record for this day, 41 k less than extent on this day in 2017.
-  Extent gain from minimum is 4.150 million km2, 1.227 million km2 (22%) less than the average of 5.377 million km2 by this day,
- 32.9% of average extent gain done, with 143 days to average date of maximum (16 Sept),

The Perils of Projections
Remaining average freeze of last 10 years gives a max of 17.33 million km2, 0.73 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
I will only be posting occasional updates from now on unless something of note occurs.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

Darvince

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Re: Sea Ice Extent around Antarctica
« Reply #1208 on: April 28, 2019, 08:53:32 AM »
My theory that belongs to me (and the phrase that belongs to Gerontocrat :P ) that the ice levels in early and mid fall are an inverse of the ice levels in mid and late spring continues to hold with this drop to lowest on record, like the lowest on record time in December and January.

Nikita

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Re: Sea Ice Extent around Antarctica
« Reply #1209 on: May 03, 2019, 01:14:44 PM »
NSIDC Data.


gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1210 on: May 03, 2019, 01:45:11 PM »
JAXA ANTARCTIC Sea Ice Extent :  7,120,792 km2(May 2, 2019)

Extent gain mostly below average in the last few days so 2019 extent stays lowest in the satellite record again (for the 23rd time this year).
- Extent gain on this day 104k, 21 k less than the average gain of 125 k on this day.
- Extent is lowest in the satellite record for this day, 114 k less than extent on this day in 2017.
-  Extent gain from minimum is 4.696 million km2, 1.294 million km2 (22%) less than the average of 5.990 million km2 by this day,
- 36.8% of average extent gain done, with 137 days to average date of maximum (16 Sept),

The Perils of Projections
Remaining average freeze of last 10 years gives a max of 17.24 million km2, 0.82 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
I will only be posting occasional updates from now on unless something of note occurs.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1211 on: May 11, 2019, 11:54:54 AM »
JAXA ANTARCTIC Sea Ice Extent :  8,030,687 km2(May 10, 2019)

Extent gain a mixture of above and  below average in the last week days so 2019 extent stays lowest in the satellite record for the 31st time this year.
- Extent gain on this day 86k, 19 k less than the average gain of 105 k on this day.
- Extent is lowest in the satellite record for this day, 153 k less than extent on this day in 2017.
-  Extent gain from minimum is 4.606 million km2, 1.290 million km2 (19%) less than the average of 6.896 million km2 by this day,
- 42.7% of average extent gain done, with 129 days to average date of maximum (16 Sept),

The Perils of Projections
Remaining average freeze of last 10 years gives a max of 17.22 million km2, 0.84 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
I will only be posting occasional updates from now on unless something of note occurs.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

Rich

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Re: Sea Ice Extent around Antarctica
« Reply #1212 on: May 12, 2019, 03:54:47 AM »
Thanks to those who share this information. Is there any sense as to what is causing the low values in Antarctic sea ice? I've read reports recently that the Ross Ice Shelf is becoming more vulnerable to solar heated surface waters.

Is that the possible root cause across the entire region?

Tealight

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Re: Sea Ice Extent around Antarctica
« Reply #1213 on: May 12, 2019, 06:03:23 PM »
Hi Rich, the current low sea ice extent is caused mostly by the Weddel Sea (see picture below). The Ross Sea is around average. I would say the cause is the current weather pattern. The circumpolar winds are very weak and plenty of mid latitude warmth reaches further south. Somewhere I read that the Antarctic Circumpolar Current is gradually moving south over the last few years, but I can't remember the source.

Rich

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Re: Sea Ice Extent around Antarctica
« Reply #1214 on: May 12, 2019, 08:11:28 PM »
Hi Rich, the current low sea ice extent is caused mostly by the Weddel Sea (see picture below). The Ross Sea is around average. I would say the cause is the current weather pattern. The circumpolar winds are very weak and plenty of mid latitude warmth reaches further south. Somewhere I read that the Antarctic Circumpolar Current is gradually moving south over the last few years, but I can't remember the source.


Thanks for the map. It helps to see a picture to visualize that the shift is primarily regional.

I'm not an expert, but my basic understanding is that Circumpolar Deep Water (CDW) has been increasingly encroaching on Antarctica for decades as a result of a tighter circumpolar circulation pattern and this is causing the increasing ice melt in Antarctica at depth. I picked this up from an Eric Rignot (NASA) presentation on sea level rise.

My understanding is that the warmer CDW remains at depth because it's saltier and denser than the fresh layer at the surface. If the sea ice is slowing down in the Weddel Sea area, it should be a sign of something new going on near the surface.

I'm a relatively new, mostly lurker here and see there is a lot of expertise and discussion on what is going on in the Arctic. This year's Antarctic anomaly is quite large and I imagine a lot of interest will migrate over here if the trend persists.




oren

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Re: Sea Ice Extent around Antarctica
« Reply #1215 on: May 12, 2019, 10:59:48 PM »
Thanks Rich for raising this issue. I hope to present an analysis of the changes in Antarctic sea ice since 2016 by region, if I can find the time to complete it.

Rich

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Re: Sea Ice Extent around Antarctica
« Reply #1216 on: May 12, 2019, 11:37:30 PM »
Thanks Rich for raising this issue. I hope to present an analysis of the changes in Antarctic sea ice since 2016 by region, if I can find the time to complete it.

I look forward to reading it.

oren

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Re: Sea Ice Extent around Antarctica
« Reply #1217 on: May 13, 2019, 05:44:58 AM »
I started with analyzing the higher resolution UH AMSR2 data, despite its short record (only since 2012, with some holes until Apr 2013), charting by region. My goal was to map the "sea change" that happened around 2016 and locate where it occurred.
Note: all data courtesy of Wipneus at ArctischePinguin https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/data

There are 5 regions defined for Antarctica - Weddel Sea, Ross Sea, Bellingshausen & Amundsen Seas, Indian Ocean, West Pacific Ocean. For each region I made a comparative chart of all years, as well as a chart showing cross-sections at various specific days of the year.
It seems there are several factors at play, at various regions and seasons.
I will start with the regions that show what seem to me like random variations with no discernible change: Indian Ocean and Bellingshausen & Amundsen Seas.

oren

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Re: Sea Ice Extent around Antarctica
« Reply #1218 on: May 13, 2019, 06:05:15 AM »
The West Pacific Ocean sector is showing what seems to be like clear trends in spring, summer and fall but not around the max. So I would guess something happened around 2016 that caused a lower minimum and especially a later refreeze.

oren

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Re: Sea Ice Extent around Antarctica
« Reply #1219 on: May 13, 2019, 06:14:10 AM »
In the Ross Sea, there seems to be a change to lower minimums, and especially a marked change of a later refreeze (around day 133) - the years since 2016 are 0.5 million km2 lower than the years up to 2015.

oren

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Re: Sea Ice Extent around Antarctica
« Reply #1220 on: May 13, 2019, 06:28:05 AM »
Finally, the Weddel Sea, the largest sector, shows the most marked signs of change in the period leading up to and around the minimum (days 30, 60, 365). In 2018-2019 we can also see very low extent around day 133, but not sure if this is random variation or a more significant change.

General note: it's obvious that none of these changes are statistically significant. However, as over 3 years have passed with surprisingly low Antarctic sea ice extents, I think it could be useful to point to the locations and periods where the change seems to have occurred, to enable better scrutiny of more physical parameters for these periods and locations - temperatures, winds, currents etc.

oren

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Re: Sea Ice Extent around Antarctica
« Reply #1221 on: May 13, 2019, 06:34:27 AM »
Next, I would like to make the same analysis with NSIDC data, with its much longer record (though at lower resolution). Tomorrow.

Rich

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Re: Sea Ice Extent around Antarctica
« Reply #1222 on: May 15, 2019, 12:23:05 AM »
Next, I would like to make the same analysis with NSIDC data, with its much longer record (though at lower resolution). Tomorrow.

Thanks for providing these. If the trend persists, I hope that some more expertise drifts over to what's happening around Antarctica. We're 1.4M km2 below the decade average for this date. Something is going on.

FishOutofWater

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Re: Sea Ice Extent around Antarctica
« Reply #1223 on: May 15, 2019, 01:32:04 AM »
El Niño years release warm water polewards and Antarctic waters generally see a warming at the end of the El Niño. There was a strong El Niño in 2015-2016. That may explain much of the recent drop in Antarctic sea ice, but other things may be happening, too.

oren

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Re: Sea Ice Extent around Antarctica
« Reply #1224 on: May 15, 2019, 04:18:38 AM »
Getting back to the long term analysis, this time as promised with NSIDC data going back to late 1978. Data as usual supplied by Wipneus.
Looking at the total Antarctic Sea Ice Extent, it can be seen that in general there was an uptrend is ANT SIE over the years, with a reversal to lows since 2016. This phenomenon is more apparent during the melting season (days 365, 30, 60) and early freezing (day 133) leading to record or near-record lows. It is less apparent around the maximum (days 214, 274). So it seems ice suddenly started to melt earlier and refreeze later, after decades of doing the opposite.

oren

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Re: Sea Ice Extent around Antarctica
« Reply #1225 on: May 15, 2019, 04:20:14 AM »
Looking at the Antarctic regions, two of them don't show discernible trends, in line with the UH data - the Indian Ocean and the Bellingshausen & Amundsen Seas sector.

oren

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Re: Sea Ice Extent around Antarctica
« Reply #1226 on: May 15, 2019, 04:30:38 AM »
The Ross Sea sector doesn't seem to show much of an uptrend (especially for days 30,60), but does show a sharp drop since 2016.
OTOH, the West Pacific Ocean shows a quite clear uptrend during the melting season, with the drop since 2016 barely a reversal to mean and certainly not near record low territory.
The Weddel Sea sector seems to have some uptrend though it is very volatile, but saw record lows during the early freezing season in 2018 and 2019.
So it seems the long term behavior is a combination of some sectors being quite random, others building the trend and yet others reversing it. Not a very intuitive result, and one best explained by looking at each sector (especially Ross, Weddel) in detail using other parameters beyond the dry extent numbers.

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1227 on: May 15, 2019, 10:19:39 AM »
JAXA ANTARCTIC Sea Ice Extent :  8,500,344 km2(May 14, 2019)

Extent gain a mixture of above and  below average in the last few days so 2019 extent stays lowest in the satellite record for the 35th day this year.
- Extent gain on this day 98k, 14 k less than the average gain of 112 k on this day.
- Extent is lowest in the satellite record for this day, 153 k less than extent on this day in 2017.
-  Extent gain from minimum is 6.076 million km2, 1.261 million km2 (17%) less than the average of 7.337 million km2 by this day,
- 45.6% of average extent gain done, with 125 days to average date of maximum (16 Sept),

The Perils of Projections
Remaining average freeze of last 10 years gives a max of 17.22 million km2, 0.84 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
I will only be posting occasional updates from now on unless something of note occurs.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

Rich

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Re: Sea Ice Extent around Antarctica
« Reply #1228 on: May 15, 2019, 11:54:54 AM »
Thanks for sharing the spreadsheet data. The drop of > 3M km2 from the 2016 peak at this time of year is pretty staggering. That's an area over 4x the size of the state of Texas.


b_lumenkraft

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Re: Sea Ice Extent around Antarctica
« Reply #1229 on: May 15, 2019, 12:10:42 PM »
TI(disappointedly)L Google can't convert Texas to Saarland.

(Germans will understand)

magnamentis

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Re: Sea Ice Extent around Antarctica
« Reply #1230 on: May 15, 2019, 07:04:54 PM »
TI(disappointedly)L Google can't convert Texas to Saarland.

(Germans will understand)

my thought exactly while i refrained from my reply, it would have come less political correct LOL

BTW i checked OSX calculator that has a huge set of conversions ready, no success, no texas to saarland conversion either ;) ;) ;) ;)

EDIT: who knows, perhaps we're both wrong, after all there must be a reasons why all known aliens are landing in the united states and recently canada (companions) :D :D :D

sorry for the OT but it's so much fun and no, i'm not german but an informed swiss who speaks german without accent haha... (my grandma was a born "keitel" form mainz BTW) old germans will know  8) 8) 8)
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b_lumenkraft

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Re: Sea Ice Extent around Antarctica
« Reply #1231 on: May 15, 2019, 07:26:49 PM »
Sorry Magnamentis, should have said, "DACH people will understand". I bet the Austrians also know that Saarland is the best square measure.

magnamentis

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Re: Sea Ice Extent around Antarctica
« Reply #1232 on: May 15, 2019, 08:22:39 PM »
Sorry Magnamentis, should have said, "DACH people will understand". I bet the Austrians also know that Saarland is the best square measure.

call it ROOF instead of DACH (lost in translation) and confusion's gonna be

END OT / END FUN
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Stephan

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Re: Sea Ice Extent around Antarctica
« Reply #1233 on: May 15, 2019, 10:57:42 PM »
Looking at the Antarctic regions, two of them don't show discernible trends, in line with the UH data - the Indian Ocean and the Bellingshausen & Amundsen Seas sector.
Could there be an influence of the fast melting glaciers in the Amundsen Sector of West Antarctica? Thousands of icebergs calving from Thwaites etc. are released into the ocean. They need a lot of energy to melt. It means increasing ice volume distributed into the sea, and in addition the melting of the ice sheets from below which also requires energy may explain the different behaviour of this sector compared to other seas around Antarcica, protecting it from higher sea surface temperatures.
Just a thought, a guess...

Tealight

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Re: Sea Ice Extent around Antarctica
« Reply #1234 on: May 15, 2019, 11:59:22 PM »
Nice analysis oren. As in my regional snow cover analysis some charts are very hard to read due to the high year to year variability. To me it looks like the Bellinghausen & Amundsen Sea have a downward trend for day 133 and day 365. The highs of the 2010s are the lows of the 1980s. The lines for day 166 to 274 are just to noisy to see anything.

Can make some 365 day charts showing decade averages? They have less noise and melt events don't have to fit into an exact month or specific day.

gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1235 on: May 16, 2019, 08:01:40 PM »
In general, Antarctic SIE very gradually increased over the decades until 2015 - which was a very high max. And then extent crashed from September 2016 and has stayed down. I don't have a clue why. There is an article, but I am still confused..

https://www.nature.com/articles/s41467-018-07865-9
Sustained ocean changes contributed to sudden Antarctic sea ice retreat in late 2016
Quote
Abstract
After nearly three decades of observed increasing trends of Antarctic sea ice extent, in September-October-November 2016, there was a dramatic decrease. Here we document factors that contributed to that decrease. An atmosphere-only model with a specified positive convective heating anomaly in the eastern Indian/western Pacific Ocean, representing the record positive precipitation anomalies there in September-October-November 2016, produces an anomalous atmospheric Rossby wave response with mid- and high latitude surface wind anomalies that contribute to the decrease of Antarctic sea ice extent. The sustained decreases of Antarctic sea ice extent after late 2016 are associated with a warmer upper Southern Ocean. This is the culmination of a negative decadal trend of wind stress curl with positive Southern Annular Mode and negative Interdecadal Pacific Oscillation, Ekman suction that results in warmer water being moved upward in the column closer to the surface, a transition to positive Interdecadal Pacific Oscillation around 2014–2016, and negative Southern Annular Mode in late 2016.

Anyway, this year so far is mostly about the 2 biggest seas - i.e. Weddell Sea low extent, and the Ross Sea lowish extent.
"Para a Causa do Povo a Luta Continua!"
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gerontocrat

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Re: Sea Ice Extent around Antarctica
« Reply #1236 on: May 19, 2019, 10:53:50 AM »
JAXA ANTARCTIC Sea Ice Extent :  9,005,616 km2(May 18, 2019)

Extent gain switched to well above average in the last few days, but 2019 extent stays lowest in the satellite record for the 39th day this year.

- Extent gain on this day 175k, 85 k MORE than the average gain of 90 k on this day.
- Extent is lowest in the satellite record for this day, 280 k less than extent on this day in 2017.
-  Extent gain from minimum is 6.581 million km2, 1.173 million km2 (15%) less than the average of 7.754 million km2 by this day,
- 48.3% of average extent gain done, with 121 days to average date of maximum (16 Sept),

The Perils of Projections
Remaining average freeze of last 10 years gives a max of 17.30 million km2, 0.76 million km2 less than 2017 (the record low maximum year).
______________________________________________________________________
I will only be posting occasional updates from now on unless something of note occurs.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)