NSIDC 2013 Arctic SIE September minimum: August poll

[ChrisReynolds]

Anyone know where I can get a full series of daily extent from 1978 onwards?

[Wipneus]

Anyone know where I can get a full series of daily extent from 1978 onwards?

What is wrong with the NSIDC data, ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/north/daily/data

Jaxa has series, require registration and have some data restrictions:
http://kuroshio.eorc.jaxa.jp/JASMES/climate/index.html

Requesting full data from 1978 restricts the data and algorithms to those suited for even the oldest satellite that have been used to monitor Sea Ice (Nimbus-7 IIRC).

[Wipneus]

NSIDC updated: 6.15771 down -64k7

I calculated the details:
Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -10.6                   -16.1                    14.2
               Kara Sea             Barents Sea           Greenland Sea
                   11.2                   -26.3                     0.0
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   10.6                     0.0                   -68.1
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   49.3                   -28.4                    -0.6
             Bering Sea          Sea of Okhotsk            Total Extent
                    0.0                     0.0                   -64.7

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                    4.2                   -10.0                     1.3
               Kara Sea             Barents Sea           Greenland Sea
                    1.9                    -6.9                    -0.6
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                    3.4                     0.0                   -15.7
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   18.5                    -5.7                    -4.0
             Bering Sea          Sea of Okhotsk              Total Area
                    0.0                     0.0                   -13.5


Barentsz and Hudson are now back to normal, cannot be said of CAA.

I am beginning to understand why nobody made daily regional data available.   :-)

[Ned W]

I am beginning to understand why nobody made daily regional data available.   :-)

Yes, the advantage of aggregating it is that some of the errors may cancel out...

[Wipneus]

I am beginning to understand why nobody made daily regional data available.   :-)

Yes, the advantage of aggregating it is that some of the errors may cancel out...

Regional data shows that large swings originate from regions that are ice free.

[Ned W]

Yes.  Of course, that's where it's easiest to see the error... Presumably there are similar problems in the non-ice-free regions but we tend to interpret them as real day-to-day changes rather than "noise".  Right? 

I am not being critical of the passive microwave sea ice products or the groups that produce them -- I think these data are great.

[Vergent]

I like the phantom ice in the Aral Sea(10 o'clock at the border). When it occasionally vanishes and Jaxa takes a big drop, and people pontificate on the the accelerating melt. It is a hoot! Please look at the ice before interpenetrating numbers from a data robot. Observation is is the first step in science.



Vergent

[Wipneus]

Yes.  Of course, that's where it's easiest to see the error... Presumably there are similar problems in the non-ice-free regions but we tend to interpret them as real day-to-day changes rather than "noise".  Right? 

Yes, with a few but's:

The CAB has no coast, so this particular error will not show there; It will hit hard in the CAA;
Some errors are caused by water vapor. There is more water vapor with higher temperature: that is with lower latitudes;
Where ice concentration is near 100%, such errors are invisible as all concentrations above 100% are capped;

[Wipneus]

I like the phantom ice in the Aral Sea(10 o'clock at the border). When it occasionally vanishes and Jaxa takes a big drop, and people pontificate on the the accelerating melt

- Current Jaxa/IJIS extent graph is from WindSat;
- Jaxa/IJIS extent graph domain is ocean only, lakes are excluded.

Read the design documents. The Jaxa/IJIS/NASA engneers that are working on the second generation ASMR2 sea ice concentration algorithms are not the fools that would include Aral ice.

[Frivolousz21]

I like the phantom ice in the Aral Sea(10 o'clock at the border). When it occasionally vanishes and Jaxa takes a big drop, and people pontificate on the the accelerating melt

- Current Jaxa/IJIS extent graph is from WindSat;
- Jaxa/IJIS extent graph domain is ocean only, lakes are excluded.

Read the design documents. The Jaxa/IJIS/NASA engneers that are working on the second generation ASMR2 sea ice concentration algorithms are not the fools that would include Aral ice.

I have looked everywhere for something confirming they are using Windsat.

[Frivolousz21]

NM.  I get what you mean now.  I mis-read.

[Wipneus]

I have looked everywhere for something confirming they are using Windsat.

In the first place because they say so:

SICs are derived from various satellite-borne passive microwave radiometer (PMR) sensors using the algorithm developed and provided by Dr. Comiso of NASA GSFC through a cooperative relationship between NASA and JAXA. The following sensor's data were used;

    •   Jan. 1980 - Jul. 1987   :   SMMR
    •   Jul. 1987 - Jun 2002   :   SSM/I
    •   Jun. 2002 - Oct. 2011   :   AMSR-E
    •   Oct. 2011 - the present   :   WindSat

It seems that you have doubts, you don't say why and what you think they might be using in stead.
Assuming you think it is the AMSR2, I think it is unbelievable they would have kept that quit:

The AMSR2 is the most sophisticated instrument of its kind in orbit. The people for Jaxa are rightly proud of it and are determined to make sure that the data processing will match the sophistication of the measurements.
That means verification, and verification of an sea ice concentration algorithm means comparing with surface based observations in all seasons. That cannot be done in a day.

Perhaps you still are not convinced and think that Jaxa is quietly distributing AMSR2 data without telling. May be we can look at the sources and compare with the results.

This is IJIS/Jaxa ice extent on 2013/2/12 : -9999. That means "not available".

This is AMSR2 Descending for that day:

Ice concentration is available.
Now compare with Windsat for that same day:



Then we have IJIS/Jaxa extent on 2013/05/14: 12104688. So data seems available.

Yet, AMSR2 shows big gap:


Jaxa has an missing data list which includes:

2013/05/10    20:49:58    2013/05/14    21:14:39    5784

5784 is the time in minutes that the satellite data was not available.

At the same time, Windsat:


Convinced?

[Wipneus]

NSIDC updated to 6.08991 down -67.8

Regional details of my calculation:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -0.6                   -14.6                   -16.0
               Kara Sea             Barents Sea           Greenland Sea
                  -15.1                    -2.0                     3.3
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                    1.8                     0.0                    22.3
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -89.0                    53.1                   -10.8
             Bering Sea          Sea of Okhotsk            Total Extent
                    0.0                     0.0                   -67.8

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -32.7                    -8.9                    -4.9
               Kara Sea             Barents Sea           Greenland Sea
                   -2.5                     0.0                    -0.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                    1.5                     0.0                     4.3
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -35.8                    -4.1                    -3.8
             Bering Sea          Sea of Okhotsk              Total Area
                    0.0                     0.0                   -87.6


CAA back to normal, passes the madness to Beaufort.

[Vergent]

Convinced?

Wipneus,

Yes, thanks for clearing that up.

http://www.eorc.jaxa.jp/en/imgdata/topics/2012/tp120825.html

This article convinced me that they had switched over. After all the article topic was a new record, 4.21M, and no mention of the source of that number if it was WindSat. Also, in the concentration map the Aral Sea has been cleaned up, but if you go to the Monitor for that date the Aral is "ice" covered, so, they were well aware of the Aral problem.

I think the intent was to switch over, but the end of the three month verification period was over and they had not fixed the Aral problem. They took the line of least resistance and continued with windsat for continuity of data.

All they have to do to fix the problem is edit the land/sea grid. Maybe the source for this grid is outside their control? At any rate that concentration map is like fingernails on a chalk board to me.

WindSat is long past it's design lifetime, it will be interesting to see what happens when it goes dark.

Vergent

[Wipneus]

I don't think there is an "Aral" problem. Sea Ice concentration algorithms by their nature only work on grid cells that are partly ice partly water. When calculated over (part) land or over 100% water, the raw calculation will give false results.
From day one, these algorithms must handle this and there fore this make use of:
- land masks;
- weather filters;
- ocean masks;
- numerous other "features" to include only "real" ice.

Fixing Aral is just too easy: just don't include Aral in the proper mask

WindSat is long past it's design lifetime, it will be interesting to see what happens when it goes dark.

I do not know how ready they are at the moment. But they recently celebrated a full year in operation, it should not have to take much longer.

[Frivolousz21]

Most of the website has not been updated in years.

On top of that what are they going to do when there is open water in that huge hole windsat has no data in?

Did they count the open water as ice last year?

[Wipneus]

NSIDC update: 6.12271 , an uptick of +32k8

My regional split:
Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -25.7                    -7.5                    -3.2
               Kara Sea             Barents Sea           Greenland Sea
                    1.7                     0.7                     3.3
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   10.0                     0.0                    -3.5
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   71.7                    -2.6                   -12.1
             Bering Sea          Sea of Okhotsk            Total Extent
                    0.0                     0.0                    32.8

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   20.4                   -11.9                    -3.3
               Kara Sea             Barents Sea           Greenland Sea
                   -5.4                    -1.6                     0.9
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                    0.3                     0.0                    -0.7
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   23.3                    -1.5                    -3.4
             Bering Sea          Sea of Okhotsk              Total Area
                    0.0                     0.0                    17.2


Remarkable difference in outcome of the CAA, compared with Uni Hamburgs AMSR2 data.

[BornFromTheVoid]

With that increase of 32.8k, we're now 1.46 million km2 above 2012.

The 7 day loss rate remains well below the long term average too.



With a very strong reverse dipole taking shape, the ice may well get pushed out toward Beaufort and Chukchi, slowing down the overall extent loss. We could struggle to get below 5 million km2 at this rate...

[BornFromTheVoid]

Interesting to note that MASIE is only 180k behind 2012. IMS, which has only updated to the 7th, had us behind 2012 by 446k, compared to 1.03 million on NSIDC for the same date.

[Patrick]

Wipneus,

may I ask, which dataset you are using for your calculations? Is it the same NSIDC uses for its daily extent images?

[Wipneus]

Wipneus,

may I ask, which dataset you are using for your calculations? Is it the same NSIDC uses for its daily extent images?

That is the one Patrick.

If there are other NSIDC data sets that have daily "near real time" updates, I am interested.

[Vergent]

NSIDC SIE = 6.12 Mkm^2

CT       SIA = 4.22 Mkm^2

CAPIE        = 0.70(70% average concentration)

There is 1.90 Mkm^2 of open water among the ice extent. That is bigger than the state of Alaska(1.7 Mkm^2)! There is a lot of air in the extent balloon. That is conservative because CT is 3 days behind NSIDC(thanks Wipneus for figuring that out).

Vergent

[Bob Wallace]

If area is scored as "ice" if the cell is at least 15% frozen wouldn't that mean that a CAPIE of 70% would be a 'high end of the range' number?

The actual amount of open water in the "frozen cell" could be from 0% to 85% but it's getting counted as 0%.

[Ned W]

CAPIE        = 0.70(70% average concentration)

There is 1.90 Mkm^2 of open water among the ice extent. That is bigger than the state of Alaska(1.7 Mkm^2)! There is a lot of air in the extent balloon.

Well, that's not at all unusual for this time of year:



Blue dots are Area/Extent from 1979-present, red dots are this year. 
Today's concentration is essentially identical to the long-term average.

[jdallen]

CAPIE        = 0.70(70% average concentration)

There is 1.90 Mkm^2 of open water among the ice extent. That is bigger than the state of Alaska(1.7 Mkm^2)! There is a lot of air in the extent balloon.

Well, that's not at all unusual for this time of year:

*snippage*

Blue dots are Area/Extent from 1979-present, red dots are this year. 
Today's concentration is essentially identical to the long-term average.

"Average" is a very risky statistic to apply to this ice, especially as pertains to concentration.  There are far more voids, and they are smaller.  Ice covers more area, but it is in far smaller floes, and may be much thinner. We may still end up with about the same volume, perhaps even less than last year.

[Ned W]

There are far more voids, and they are smaller.  Ice covers more area, but it is in far smaller floes, and may be much thinner. We may still end up with about the same volume, perhaps even less than last year.

(1) How do you know there are "far more voids, and they are smaller"?  Can you quantify that?

(2) Assuming that's true, are you suggesting that CAPIE is wrong as an indicator of concentration because it's missing all these small voids (i.e., CAPIE ought to be significantly lower than 0.70)?  Or do you mean that it's correct, but that an ice pack with 30% open water will behave substantially differently if the 30% is in lots of small voids versus fewer bigger gaps?

(3) For now, PIOMAS is above all three previous years (2010, 2011, 2012).  It's currently about 20% above last year, I think.  If the rest of this year follows the pattern of 2008 we could end up below 2012, but if it follows the pattern of most other years PIOMAS won't break any records this time.

[Ned W]

OK, I see you were just addressing some of that in the other thread (on CT area predictions).  But it all sounds very subjective and un-verifiable. 

Others may prefer to assume that this year's CT/NSIDC products can be fairly compared to previous years unless proven otherwise.  If you're right that there's a difference, and if you're right that it matters, then I guess we'll find out at some point when the difference manifests itself in some quantifiable way (a sudden increase in the melt rate, a sudden drop in PIOMAS, or whatever).

[Patrick]

Wipneus,

may I ask, which dataset you are using for your calculations? Is it the same NSIDC uses for its daily extent images?

That is the one Patrick.

If there are other NSIDC data sets that have daily "near real time" updates, I am interested.

Ok, thanks. I also don't know of any other "realtime" data set, I just wanted to confirm that it is this one and that I didn't miss anything on the NSIDC page.

So, looking at the daily extent image, the indicated ice in Coronation Gulf and the surrounding areas caught my eye. Thus I did a quick crosschecking with NASA Worldview and sure enough a clear view on Wednesday showed open ocean with no ice, whereas yesterday clouds were covering this region.

 Interestingly the pattern of these clouds somehow seems to vaguely match that of the sea ice extent, at least in Coronation Gulf.

So to me it looks like the algorithm has a little bit of a problem with those clouds and consequently I'm expecting a revision for that data.

[ChrisReynolds]

Anyone know where I can get a full series of daily extent from 1978 onwards?

What is wrong with the NSIDC data, ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/north/daily/data

Jaxa has series, require registration and have some data restrictions:
http://kuroshio.eorc.jaxa.jp/JASMES/climate/index.html

Requesting full data from 1978 restricts the data and algorithms to those suited for even the oldest satellite that have been used to monitor Sea Ice (Nimbus-7 IIRC).

Thanks Wipneus,

I didn't know NSIDC had full daily data, I've only ever had the monthly.

[Wipneus]

Anyone know where I can get a full series of daily extent from 1978 onwards?

What is wrong with the NSIDC data, ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/north/daily/data

Jaxa has series, require registration and have some data restrictions:
http://kuroshio.eorc.jaxa.jp/JASMES/climate/index.html

Requesting full data from 1978 restricts the data and algorithms to those suited for even the oldest satellite that have been used to monitor Sea Ice (Nimbus-7 IIRC).

Thanks Wipneus,

I didn't know NSIDC had full daily data, I've only ever had the monthly.

That link has been for years on the top of Neven's Arctic Sea Ice Graphics page.

[Wipneus]

So to me it looks like the algorithm has a little bit of a problem with those clouds and consequently I'm expecting a revision for that data.

The biggest problem is resolution. The  SSMIS instrument on the DMSP-F17 satellite has a field of view of 74x45km for the 19GHZ channel (and 45x28km for 37GHZ).
Considering that the nominal grid cell size is 25x25km, there is considerable overlap. In the Canadian Archipelago channels that means with land which have totally different emissions.
That is why the AMSR-E and AMSR2  are such beautiful instruments, AMSR2 at 89GHz has a footprint of 3x5km, IIRC.

[Frivolousz21]

So to me it looks like the algorithm has a little bit of a problem with those clouds and consequently I'm expecting a revision for that data.

The biggest problem is resolution. The  SSMIS instrument on the DMSP-F17 satellite has a field of view of 74x45km for the 19GHZ channel (and 45x28km for 37GHZ).
Considering that the nominal grid cell size is 25x25km, there is considerable overlap. In the Canadian Archipelago channels that means with land which have totally different emissions.
That is why the AMSR-E and AMSR2  are such beautiful instruments, AMSR2 at 89GHz has a footprint of 3x5km, IIRC.

Doesn't NSIDC use channel 91GHZ?

[Wipneus]

Doesn't NSIDC use channel 91GHZ?

Not in this series. NSIDC values the homogeneity of their series very high, so must use channels that have been on board of the first satellites that were used (SMMR on Nimbus-7).
Also Jaxa/IJIS  is NOT using the highest frequencies for their ice concentration/extent products.

It is absolutely the selling point of the ASI algorithm (Uni's Bremen and Hamburg) that the ~90GHZ channels are at the core of the algorithm.

[Frivolousz21]

Doesn't NSIDC use channel 91GHZ?

Not in this series. NSIDC values the homogeneity of their series very high, so must use channels that have been on board of the first satellites that were used (SMMR on Nimbus-7).
Also Jaxa/IJIS  is NOT using the highest frequencies for their ice concentration/extent products.

It is absolutely the selling point of the ASI algorithm (Uni's Bremen and Hamburg) that the ~90GHZ channels are at the core of the algorithm.

Does Bremens ASI algorithm also incorporate channel 36GHZ and 18GHZ on AMSR2?


I was surprised to learn back in 2011 that Cosimo's algorithm for Jaxa doesn't use channel 89GHZ.


However unlike SSMIS.  AMSRE and AMSR2 have pretty high resolution for those channel as well as wind-sat.

[Wipneus]

NSIDC at 5.98667 down -136k0

My calculation gives -137.4, that is two "pixels" more.

The regional details:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -11.1                   -24.0                    -9.8
               Kara Sea             Barents Sea           Greenland Sea
                  -11.4                    -2.6                   -17.0
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   20.3                     0.0                   -22.6
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -20.9                   -20.2                   -18.0
             Bering Sea          Sea of Okhotsk            Total Extent
                    0.0                     0.0                  -137.4

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -5.0                    -9.4                    -6.1
               Kara Sea             Barents Sea           Greenland Sea
                   -7.4                    -0.7                    -4.9
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                    6.6                     0.0                    -7.1
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -6.9                    -3.4                    -5.1
             Bering Sea          Sea of Okhotsk              Total Area
                    0.0                     0.0                   -49.4

[Wipneus]

It is absolutely the selling point of the ASI algorithm (Uni's Bremen and Hamburg) that the ~90GHZ channels are at the core of the algorithm.

Does Bremens ASI algorithm also incorporate channel 36GHZ and 18GHZ on AMSR2?

Yes, it uses the lower frequencies to offset some of the disadvantages of the ~90GHZ channels, the sensitivity for atmospheric conditions.

I was surprised to learn back in 2011 that Cosimo's algorithm for Jaxa doesn't use channel 89GHZ.

The name is Comiso.
Yes, his algorithm is also rooted in the SMMR time.
AMSR2 will also support the NASA TEAM 2 algorithm, that includes the 89GHZ channels and probably the most advanced algorithm of them all.

However unlike SSMIS.  AMSRE and AMSR2 have pretty high resolution for those channel as well as wind-sat.

Yes, at least for the AMSR-E and AMSR2.

[ChrisReynolds]

That link has been for years on the top of Neven's Arctic Sea Ice Graphics page.

I can't recall ever having been there.

[Neven]

That link has been for years on the top of Neven's Arctic Sea Ice Graphics page.

I can't recall ever having been there.

You've never been on the ASIG? Shame on you, Chris. Shame on you. 

[ChrisReynolds]

Nothing personal Neven,
 
I'm just busy and have a routine of data sources.

[Neven]

Ah, so you were serious? Shame on you, Chris! 

[ChrisReynolds]

  

[Wipneus]

NSIDC 5.94823, down -38k4

I get an unusual different value -43k0, a 7 "pixels" disagreement.

The details:
Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -10.5                   -12.5                     3.3
               Kara Sea             Barents Sea           Greenland Sea
                    4.8                    -0.6                     4.7
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -29.6                     0.0                    -0.4
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -9.9                    10.1                    -2.4
             Bering Sea          Sea of Okhotsk            Total Extent
                    0.0                     0.0                   -43.0

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                 -111.0                   -14.3                    -0.2
               Kara Sea             Barents Sea           Greenland Sea
                    1.8                     0.5                     0.7
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   -6.0                     0.0                     1.1
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    3.5                    15.4                    -0.3
             Bering Sea          Sea of Okhotsk              Total Area
                    0.0                     0.0                  -108.7

[BornFromTheVoid]

Update for the week to August 17th

The current 1 day extent is 5,948,230km2, while the 5 day mean is on 6,061,046km2
 
The daily anomaly (compared to 79-11) is at -1,127,280km2, a decrease from -1,133,920km2 last week. The anomaly compared to the 07, 11 and 12 average has increased from +795,420km2 to +897,450km2 this week. We're currently 6th lowest on record, the same as last week.
 
The average daily loss over the last 7 days was 52.6k/day, compared to the long term average of 53.7k/day, and the average of the last 5 years of 67.2k/day.

The average long term loss over the next week is 46.7k/day, with the average of the last 5 years being 72.1k/day.

The loss so far this August is the 15th largest on record, at -1,148,200km2. We need to average a loss of 112.1k/day for the remainder of the month to record the largest August extent drop on record.

The daily minimum extent so far this year is below the annual daily minima of 22 out of 34 previous years, and within 1 million km2 of another 7.

[Wipneus]

NSIDC 5.94401 down -4k2

My calculations indicate a plus: +1k7,  that is +9 "pixels" different. Can probably discounted from yesterdays -7 pixels.

The regional split:
Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                    2.7                     8.0                    11.5
               Kara Sea             Barents Sea           Greenland Sea
                   -3.2                     2.5                    -1.4
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   -2.3                     0.0                    -6.6
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -16.9                    -5.7                    11.8
             Bering Sea          Sea of Okhotsk            Total Extent
                    1.2                     0.0                     1.7

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -32.8                   -10.8                     0.0
               Kara Sea             Barents Sea           Greenland Sea
                   -2.1                    -1.1                    -5.7
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   -0.5                     0.0                    -1.7
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    1.7                     4.7                     3.4
             Bering Sea          Sea of Okhotsk              Total Area
                    0.2                     0.0                   -44.6


No report from me the next two days. Be back Thursday.

[Ned W]

Hard to believe how things have transpired over the past few weeks since this poll was created. 

Here's the current NSIDC compared to previous years, with each year's daily minimum highlighted.  We seem to be very consistently tracking somewhere between 2008, 2009, and 2010:



Here's a graph showing the actual September monthly minima 2000 through 2012 (left, in colors) and the projected 2013 monthly minimum if it follows the pattern of each of those previous years for the rest of this season:



Most probable outcome is now somewhere around 5.15.  A monthly minimum below 4.75 now seems highly unlikely; it would require a sudden change to ice loss far faster than any previous year.

In other words, the only question is whether 2013 will end up in the topmost or next-to-topmost box of the 21 boxes in the poll ... the lower 19 boxes are pretty much out of the running.  Or so it would seem ...

Anyone still think a Sept. mean below 4.5 is likely?

I still can't shake the (subjective, maybe irrational) feeling that the ice loss rate has to pick up at some point, so I'd give it a 50/50 chance of ending below 5.0 ... even though my own projection says it's more like a 10% chance.

Of course, prior to 2007 any of these possibilities would have looked low!  But now we think of over 5.0 as "high". 

[BornFromTheVoid]

A drop of 118.2k yesterday, puts us within 100k of 2010, and just over 200k off 2008.

[Wipneus]

NSIDC 5.75302 a drop of -67k6

Exactly what I calculated. Here is the regional split and area's:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -22.3                    -5.0                    -3.9
               Kara Sea             Barents Sea           Greenland Sea
                   -0.6                    -6.5                    -4.1
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   -5.9                     0.0                    16.3
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -31.0                     2.5                    -7.7
             Bering Sea          Sea of Okhotsk            Total Extent
                    0.6                     0.0                   -67.6

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -18.2                   -11.1                    -2.7
               Kara Sea             Barents Sea           Greenland Sea
                   -0.9                    -0.9                    -3.0
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                    0.3                     0.0                     4.8
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -17.4                    -6.3                    -2.3
             Bering Sea          Sea of Okhotsk              Total Area
                    0.1                     0.0                   -57.6

[Wipneus]

NSIDC 5.66510 a drop of -87k9

I calculate a drop of 91k2, differ by 5 "pixels"

The regional extent and area split:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -23.1                   -14.6                    -5.2
               Kara Sea             Barents Sea           Greenland Sea
                   -5.1                     1.7                    -1.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                    0.0                     0.0                   -28.8
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -12.8                   -10.8                    10.0
             Bering Sea          Sea of Okhotsk            Total Extent
                   -0.6                     0.0                   -91.2

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                    9.1                    -8.5                     5.9
               Kara Sea             Barents Sea           Greenland Sea
                   -3.0                     0.1                     4.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   -2.0                     0.0                    -9.1
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -7.2                     2.0                     1.9
             Bering Sea          Sea of Okhotsk              Total Area
                   -0.1                     0.0                    -6.1

[BornFromTheVoid]

Here's where we stand with regard to previous years minima



Closest 3 minima are 2002 (-40,540km2), 2005 (-346,780km2) and 2009 (-610,220km2)

[Wipneus]

Here is an extent change graph based on the NSIDC data.
We can see that the polar polynya has appeared on NSIDC, probably for the first time.
Further this illustrates that the noise from supposed "ice free" coasts in Hudson, Baffin and the Siberia shoes is considerable.
As far as I know, NSIDC does not count in this month the ice in the Great and other lakes. Crysosphere Today does.

(attached image log in to see)