The 2020/2021 freezing season

[uniquorn]

SIMB3 443910 is paired with whoi itp120 in the beaufort.
Ice+snow appear to have thickened during the freezing season by 64cm to 1.716m

SIMB3 344910 is paired with whoi itp121 in the beaufort.
Ice+snow appear to have thickened by 65cm to 2.753m



More details on the buoy thread

<>Meanwhile JAXA extent is flatlining<>

Just a touch of refreeze in Okhotsk so far. amsr2-uhh, feb1-22

edit: added Wipneus UH_AMSR2_3.125km extent, Okhotsk

[uniquorn]

NERSC CMEMS ice concentration forecast, atlantic side, feb22-mar2

[passenger66]

https://news.yahoo.com/russian-tanker-cuts-previously-impossible-153300350.html
"The deepest ice encountered by the ships was about 5 feet thick. The vessels encountered no multi-year buildup of old ice on the route, however, and meteorologist and journalist Eric Holthaus called that a clear indicator of "a climate emergency.""
Will they update the models with ice thickness data from commercial shipping in the future.

[Jim Hunt]

The NSIDC extent metric seems to be back in business:

https://GreatWhiteCon.info/2021/02/the-2021-maximum-arctic-sea-ice-extent/#Feb-23

No new data on Charctic just yet though.

[Cook]

So, has the melting season started?

[Thomas Barlow]

So, has the melting season started?

Unlikely, but not impossible.

[oren]

Likelihood is increasing daily but the jury is still out. Stephan's stats are a great help in determining probability.

[Stephan]

I evaluated the JAXA data of all freezing seasons from Feb 19 to the individual maximum to find out how often an increase of 0.23 M km² has happened after Feb 19. This is the value needed to be higher than the actual maximum from Feb 16 (13.98 M km²). I grouped these evaluations into the different decades. The evaluation has three outcomes:
A - an increase higher than 0.24 M km² has happened in x years (Pass), which means the maximum has not been reached
B - an increase of 0.23 ± 0.01 M km² has happened in y years (Intermediate), which means the maximum may have been reached, but maybe not
C - an increase of less than 0.22 M km² has happened in z years (Fail), which means the maximum has already been reached and we can start the melting season thread.

                     A       B      C
1979-1989:    5       2      4
1990-1999:    1       0      9
2000-2009:    5       1      4
2010-2020:    8       0      3
sum:             19      3     20

Summary: If we assume that the current situation of the ice and its distribution is more like the 2010-2020 years than e.g. the 1990s then it is more likely than not that the maximum of 2021 has not been reached yet.

Update for Feb. 22, 2020. Threshold back to 0.23 M km², "in between" 0.22-0.24 M km²

                     A       B       C
1979-1989:    2       1       8
1990-1999:    1       0       9
2000-2009:    3       0       7
2010-2020:    6       0       5
sum:            12       1     29

The probability that 2021's maximum has already passed, increases slightly.

Update for Feb 23, 2021. Same threshold values.

                     A       B       C
1979-1989:    0       2       9
1990-1999:    1       0       9
2000-2009:    3       0       7
2010-2020:    6       1       4
sum:            10       3     29

Are we already in the melting season?

[BornFromTheVoid]

For the NSIDC extent data to the 22nd, the peripheral seas are now lowest on record.

It's basically just the Barents sea that's preventing the overall sea ice extent from being lowest

[Jim Hunt]

Likelihood is increasing daily but the jury is still out.

Another slight decline today. A comparison with some other low max years:

[Iain]

Chartic is back, but a different profile from Jaxa. As if they drew a straight line from last known good to present.

[BornFromTheVoid]

The daily data leaves out the 20th and 21st. I assume they'll be added back at some point.

[Thomas Barlow]

Likelihood is increasing daily but the jury is still out.

Another slight decline today. A comparison with some other low max years:

According to this, the earliest turn-around I can see was in the last century, about Feb. 24 (1996) and Feb. 27 (1987 and '98).
Does anyone know why those turned around early on, and yet nowhere near the summer-lows of this current era?

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

[Stephan]

The annual extent maxima moved to later times and lower values in the last 30 years:
                  JAXA                        Charctic
1980s Feb 27, 15.60 M km² | Feb 27, 16.00 M km²
1990s Feb 23, 15.07 M km² | Feb 24, 15.54 M km²
2000s Mar 08, 14.67 M km² | Mar 10, 15.14 M km²
2010s Mar 15, 14.16 M km² | Mar 16, 14.69 M km²
(please note that the covered years are not exactly the same)

A larger extent in the 80s and 90s must have been further south in the so called peripheral seas as the central basin is almost full of ice by this time of the year. These more southern ice floes are more susceptible to earlier melting or to destructive wave actions in only partly ice-covered seas. Therefore the later maximum in the latest decade seems to be logical as it usually is much too cold for melting events in the inner Arctic basin.
An annual maximum in mid February 2021 would be exceptional, but not impossible.

[oren]

[ADS NIPR VISHOP (JAXA)] Arctic Sea Ice Extent.

February 24^th, 2021:
     13,701,350 km², a drop of -47,203 km².
     2021 is now 2^nd lowest on record.
     In the graph are today's 15 lowest years.
     Highlighted 2010's average, 2021 and the 5 years with daily lowest minimum:
          (2012, 2020, 2019, 2016 & 2007)

P.S. 277K km² lost since Feb 16th.
      Is it time to declare the start of 2021 melting season? 

It seems it might be time already, though surprises are possible. Stephan - another update of your historical analysis would be most helpful.

[Stephan]

Here it is.
New threshold value 0.28 ± 0.01 M km²

                     A       B       C
1979-1989:    1       1       9
1990-1999:    1       0       9
2000-2009:    3       0       7
2010-2020:    4       0       7
sum:              9       1     32

[Killian]

I used JAXA to do an eyeball analysis and no other year in their record has a pre-peak decline this long or this deep, at least not in the same rough time frame. Several have fairly deep declines, but no more than about 2/3 as deep, but none has a decline this long; they are all around half as long or shorter.

Interesting or just an anomaly?

Regardless, with the AO possibly going positive +3 through mid-March, the chance of a higher peak is still pretty good.

Another slight decline today. A comparison with some other low max years:

[Iain]

A slight down tick on the Jaxa graph

[oren]

Thanks to all. I'll give it at least another day.

[BornFromTheVoid]

Big loss coming from Barents Sea, under the influence of southerly winds.
Could continue for another few days too.
(click to play)

[Jim Hunt]

Regardless, with the AO possibly going positive +3 through mid-March, the chance of a higher peak is still pretty good.

Would you expect that to affect the low hanging fruit in the Barents?

Data to 23rd:

[Niall Dollard]

Over on the Pacific side, here is a comparison of extents for the date Feb 24th.

Compared with the 2004-2020 average, the Bering Sea this Feb 24th is at 87%.

Finally another thickness update has come through from the Tanana River deep in the interior of Alaska where the annual Nenena Ice Classic takes place.

The late Feb measurement was a quite substantial 43 inches

Compared with late Feb (circa) measurements of more recent years:

2020  31.5
2019  23.5 (very low)
2018  34
2017  31.5

This year is thickest since 2013.

[Jim Hunt]

An interesting forecast from Thomas Lavergne via Twitter:

https://twitter.com/lavergnetho/status/1364929047227211779

[Iain]

I don't see any pre-peak downticks of as great a magnitude as 2021 in the last 10 years.

[Shared Humanity]

Big loss coming from Barents Sea, under the influence of southerly winds.
Could continue for another few days too.
(click to play)

Not just compaction. There's a whole lot of melt going on.

[Thomas Barlow]

http://polarportal.dk/en/sea-ice-and-icebergs/sea-ice-extent0/#c8091

[Killian]

I used JAXA to do an eyeball analysis and no other year in their record has a pre-peak decline this long or this deep, at least not in the same rough time frame. Several have fairly deep declines, but no more than about 2/3 as deep, but none has a decline this long; they are all around half as long or shorter.

Interesting or just an anomaly?

Regardless, with the AO possibly going positive +3 through mid-March, the chance of a higher peak is still pretty good.

Another slight decline today. A comparison with some other low max years:

OK, so I just went through comparing 2021 with every other year head-to-head. Turns out there were a couple I underestimated, but the central fact is still true: None equal this year. Significantly, just two years ago there was a 280 sq km pre-peak decline.

We now stand at roughly 310 for JAXA.

I think we are seeing a form of "wobbling" (re chaos) in the climate system.

[Killian]

Regardless, with the AO possibly going positive +3 through mid-March, the chance of a higher peak is still pretty good.

Would you expect that to affect the low hanging fruit in the Barents?

Data to 23rd:

I have no opinion on that. That sort of narrowly focused question is for the numbers folk, not me, a systems/trends guy.

[gerontocrat]

It is tempting to declare a 2021 maximum, given extent today at 13.67 million is 0.31 million km2 below the current maximum of 13.98 million km2 on 16th Feb.

However, the plume showing projection of future extent from previous years' extent change shows 3 out of the previous 10 years produce a new maximum.

[Stephan]

A further loss increased the threshold value to 0.31 ± 0.01 M km².
The evaluation is:

                     A       B       C
1979-1989:    2       1       8
1990-1999:    1       0       9
2000-2009:    1       1       8
2010-2020:    4       0       7       (2010, 2012, 2014, 2020 result in "A")
sum:              8       2     32

From my opinion it is more likely than not that the 2021 maximum has already passed.

[oren]

Unless there is some rebound (or an additional crash), we will change over to a melting season thread on March 1st.

[interstitial]

the ice is still thickening and does so for a short time after peak on the other hand it is close to calling it and with some fresh arctic weather headed to washington state this freezing season looks about done.

[RikW]

So or there is an increase like 2012/2020 - the 2 worst melting seasons we have had, or the start is with such a 'headstart' that a bad melting season won't be unlikely...

[Jim Hunt]

Still no "rebound". Still second lowest.

Plus the GOFS forecast. Click to animate.

Watch the Bering Sea for example. A rebound in prospect?

[pauldry600]

Watching with interest

I think it will rebound. It will be close.

[Jim Hunt]

http://polarportal.dk/en/sea-ice-and-icebergs/sea-ice-extent0/#c8091

Not much to quote in your post Thomas!

FYI:

[Jim Hunt]

I have no opinion on that.

It seems to me that a strong polar vortex for what remains of winter might increase central ice thickness slightly.

It's less clear that it would increase extent on the periphery.

[Freegrass]

Latest Five Day Forecast
Wind + Temp @ Surface
Large GiF!

The weather in the coming days looks very favorable for a Barents and Bering Sea ice increase, and a return of Fram export. A.k.a. normal arctic weather...

[Iain]

F' What?!

[Iain]

So not only do I not see a comparable downtick in the last 10 years, nor do I see a comparable uptick to take 2021 back to 14.542 (Feb 15th)

More likely than not the 2021 peak has passed

[be cause]

I do find it strange that while we all agree that volume is the best measure , we ignore what it says about where we are in the freeze/melt cycle . Peak volume is probably 2 or 3 months away , at which time melt finally exceeds freeze .. Neither melt or freeze are seasonal in that both are always ongoing , unless we have passed the point where that is true , yet twice a year excitement builds . Are the Inuit and the polar bears awaiting the news with bated breath ? AS IF ! b.c.

[oren]

Total volume peaks in early April, and CAB volume can peak in early May. However, the melting season in the peripheral seas begins when extent reaches the annual maximum, and the forum traditionally switches over to the melting season thread at this time.

[Freegrass]

I've seen many spaghetti graphs here for the last few days, but none tell the story like this one...

Is this right? Or still data error?

[gerontocrat]

I've seen many spaghetti graphs here for the last few days, but none tell the story like this one...

Is this right? Or still data error?

Data error.

Just looked at the latest data files from NSIDC. Area data now only to 23rd Feb with big differences with previous downloads. So recent previous posts of NSIDC data on the data thread may be junk. Extent data for 25 Feb an outlier with missing data for previous 2 days.

NSIDC have a problem. Still hoping its just a problem down here on the ground and not up there with the satellite(s).

[Freegrass]

I've seen many spaghetti graphs here for the last few days, but none tell the story like this one...

Is this right? Or still data error?

Data error.

Just looked at the latest data files from NSIDC. Area data now only to 23rd Feb with big differences with previous downloads. So recent previous posts of NSIDC data on the data thread may be junk. Extent data for 25 Feb an outlier with missing data for previous 2 days.

NSIDC have a problem. Still hoping its just a problem down here on the ground and not up there with the satellite(s).

Thanks Gerontocrat. That graph was pure horror...

If there's one thing the new Cryosat satellite should be good at, it's finding the ice edge, and calculating extent. So why are Americans still using and posting corrupted old satellite data? What does the new Cryosat have to say about extend? Is there a website like the NSIDC one with similar graphs from the new Cryosat extend data?

It looks like Americans are better with websites, and Europeans better with data... 

[Jim Hunt]

So why are Americans still using and posting corrupted old satellite data?

I can't speak to the "posting corrupted" part, but they're "using old satellite data" for long term consistency.

See:

https://GreatWhiteCon.info/2016/02/dmi-masie-and-the-sea-ice-index-an-interview-with-walt-meier/

The Sea Ice Index was designed to use a consistent methodology over a long period of time using a single type of sensor. 100% automatically processed passive microwave data is the “gold standard” when it comes to determining sea ice trends. It is subject to some biases and thus is not necessarily as accurate on a given day as MASIE. However, the biases are consistent over time, so the time series will be consistent over time. This means that year-to-year comparisons and trend estimates will be more accurate in the passive microwave data than in MASIE.

[Freegrass]

The Sea Ice Index was designed to use a consistent methodology over a long period of time.....It is subject to some biases and thus is not necessarily as accurate on a given day as MASIE. However, the biases are consistent over time...

WTF? Our data is wrong, but it's consistently wrong... So don't worry about it... Just don't tell anyone that my penis is actually 3 inches shorter than what we're telling you... 

And then people ask me why I call them Americannots?

How hard can it be to find the error, calculate it, and then recalculate and correct historical data?

Edit: It's probably not that easy, but don't they have historical visuals of the ice that computers can recalculate? Or find an average error coefficient, and use that to correct historical data?

[gerontocrat]

The Sea Ice Index was designed to use a consistent methodology over a long period of time.....It is subject to some biases and thus is not necessarily as accurate on a given day as MASIE. However, the biases are consistent over time...

WTF? Our data is wrong, but it's consistently wrong... So don't worry about it... Just don't tell anyone that my penis is actually 3 inches shorter than what we're telling you... 

And then people ask me why I call them Americannots?

How hard can it be to find the error, calculate it, and then recalculate and correct historical data?

If it was that easy then either they or someone else would have done it.

Even JAXA for their long-term series do not use the full resolution capability of their latest onboard instruments to ensure that current measurements are consistent with the older measurements.

Sooner or later something will have to be done because the satellites in question are years and years beyond their design life, and at the moment there is nothing up there that can replicate the data in a manner consistent with the historical record. At which point I get my redundancy notice.

EDIT
NSIDC posted another update about an hour ago. Still no joy. I will wait until tomorrow and then ask them what goes on. is it the satellites? Is it the ground receiving stations ? If it is the satellites......

[Freegrass]

They always have the option to post the consistently wrong data, and the new corrected one side by side...

Isn't that what HYCOM is doing? Continuously updating their model so it becomes more accurate? I remember something about someone saying that you can't compare historical HYCOM data with the current one, because it differs. I completely understand this now...

[gerontocrat]

They always have the option to post the consistently wrong data, and the new corrected one side by side...

Isn't that what HYCOM is doing? Continuously updating their model so it becomes more accurate? I remember something about someone saying that you can't compare historical HYCOM data with the current one, because it differs. I completely understand this now...

Continuously updating the data processing so it becomes more accurate, and then you can't compare historical HYCOM data with the current one data, because it differs.

So no meaningful comparisons can be made so the analysis actvivity is redundant.