2018 sea ice area and extent data

[Pmt111500]

Éh, that question of different averages (noting the 80s to 90s difference isn't the only one present) is so old even I would need to check the answer from historical sources.    . Possibly it's a question of including/excluding Black Sea and Caspian (possibly also Great Lakes) to the Arctic numbers, which is somewhat silly, but JCGarcias explanation applies as well. I don't know the correct answer.

[Steven]

My question was about the diffrence between the JAXA end the NSIDC. But i explained myself pretty bad. With the JAXA you see a clear trend , the 1990 average is half a million below the 1980 average. And if you look at the NSIDC , at some days the 1990 average is above the 1980 average.

The 1980s average in Jim Pettit's graph for NSIDC extent is wrong.  In the official NSIDC Charctic graph, the 1980s average is always higher than the 1990s average.

[oren]

Maybe it's the pole hole?

[Juan C. García]

The 1980s average in Jim Pettit's graph for NSIDC extent is wrong.  In the official NSIDC Charctic graph, the 1980s average is always higher than the 1990s average.

The difference with Jim Pettit’s graph and NSIDC Charctic graph is that NSIDC includes 1979 and maybe Jim Pettit is also excluding 1980 (on the 80's average). So, there is a reason to have a different average.

Maybe it's the pole hole?

I don’t believe that it is the North Pole hole. The pole hole can make a difference on area, because in some cases the pole hole area is taken by ocean, no ice, and this hole has been shrinking. The normal status of the pole hole, and specially before 2000, is that it was ice. In extent it is taken as ice, so no problem there.

Edit:

maybe Jim Pettit is also excluding 1980

What I mean is that 80's average sometimes means 1980-89 and sometimes means 1981-90. So I am not sure what average is Jim making. On the other hand, the NSIDC 80's average has 12 years, because they explicit put it as 1979-1990 (it should included 79,80 and 90).

[gerontocrat]

I do check my spreadsheets and graphs before daring to post them on ASIF. But several times there have been errors. Perhaps there is an error in the extract of data for the graph in Jim's database ?

To err is human, to forgive divine. (Yesterday I found another error in one of my spreadsheets - fortunately not significant and fortunately no-one has spotted it yet).

[Jim Pettit]

Thanks, folks! The comments of several forum users led me to look into a small number of my graphs, and that in turn allowed me to hunt down and snuff out a data error that's gone undetected for several months.

For the record, it was indeed a legitimate screw-up on my part, a recently-introduced calculation error on a single range of cells on a spreadsheet that contains tens of thousands of them. More precisely, I'd previously been pulling older NSIDC extent data from one web-based source, but changed that last summer when I became aware of an easier-to-access, and more frequently-updated, source. In doing so, I inadvertently--and erroneously--neglected to update a formula in that range of cells that referenced the previous data; hence the incorrect 1980s average. Luckily, that cell was only reflected on a total of three graphs. And, luckily, that column and those graphs have now been updated. (And I've added +/-2 standard deviation shading to the graph in question.)

I maintain dozens of graphs, each of them based on one or more spreadsheets, with each spreadsheet itself based on sometimes multiple data sources. Complicating matters, those data sources change: different baselines, enhanced algorithms, anti-biasing tweaks, and so on, and so forth. The result is that keeping on top of all those changes can be a frustrating task for graph creators--and that can lead to obvious frustration by those who use those graphs. So for that, I apologize. Mea maxima culpa. (That's Latin for "my bad".)

For what it's worth, in the future, a direct message or an email (my address is right on the graphs) will almost always get a quicker response, as I don't monitor this forum 24 hours a day. However, if you're the type of person who prefers jumping up, pointing your finger, and publicly shouting, "You're wrong!!!", by all means knock yourself out; I'll respond to those eventually, too.

Thanks again.

[DoomInTheUK]

Jim, Allow me to jump up and down, point a finger and shout "It's him, he does all the hard work so we don't have to".

Thanks for all your efforts. Spreadsheets are a breeding ground for bugs and you seem to be doing a great job of keeping the little buggers under control.

[Juan C. García]

For the record, it was indeed a legitimate screw-up on my part...

The one who does nothing, makes no mistakes, but he does nothing!
So, thank you Jim and others, for doing all that you are doing. The Forum is what it is, thanks to all your work! 

[Hautbois]

Some first quarter of 2018 extent graphs, for what they're worth.

- 2018 compared to the daily range for each date (maxima now removed).

- 2018 compared to 5 year averages for each date. I quite like 5 year averages in climate-related graphs - especially effective for plotting surface temperature.

- For selected years, the accumulating number of days in the current bottom 3 for each respective day. I've left out any year that rack up only 1-20 days in their respective bottom 3 - and there are only three years in that group.

PS Many thanks Neven for putting my maxima graph in your blogpost - I was very gratified.

[Juan C. García]

JAXA April 8^th, 2018: 13,343,374 km². A drop of -15,098 km².
2018 continues to be second lowest on record, 105,662 km2 above 2016.

[Cid_Yama]

Thanks, folks! The comments of several forum users led me to look into a small number of my graphs, and that in turn allowed me to hunt down and snuff out a data error that's gone undetected for several months.

For the record, it was indeed a legitimate screw-up on my part, a recently-introduced calculation error on a single range of cells on a spreadsheet that contains tens of thousands of them. More precisely, I'd previously been pulling older NSIDC extent data from one web-based source, but changed that last summer when I became aware of an easier-to-access, and more frequently-updated, source. In doing so, I inadvertently--and erroneously--neglected to update a formula in that range of cells that referenced the previous data; hence the incorrect 1980s average. Luckily, that cell was only reflected on a total of three graphs. And, luckily, that column and those graphs have now been updated. (And I've added +/-2 standard deviation shading to the graph in question.)

I maintain dozens of graphs, each of them based on one or more spreadsheets, with each spreadsheet itself based on sometimes multiple data sources. Complicating matters, those data sources change: different baselines, enhanced algorithms, anti-biasing tweaks, and so on, and so forth. The result is that keeping on top of all those changes can be a frustrating task for graph creators--and that can lead to obvious frustration by those who use those graphs. So for that, I apologize. Mea maxima culpa. (That's Latin for "my bad".)

For what it's worth, in the future, a direct message or an email (my address is right on the graphs) will almost always get a quicker response, as I don't monitor this forum 24 hours a day. However, if you're the type of person who prefers jumping up, pointing your finger, and publicly shouting, "You're wrong!!!", by all means knock yourself out; I'll respond to those eventually, too.

Thanks again.

Hey, Jim.  Everything you do here, we all make mistakes.

 

[gerontocrat]

Herewith some more JAXA data as at 8th April.

[gerontocrat]

And now for some NSIDC Data, but not the usual.

I thought it was time to have a look at area, and with NSIDC having produced the March Monthly Averages for 2018, I looked at that. I was somewhat surprised at what I found.

According to the NSIDC data, while extent has gone down by about 2 million km2 since 1979, area has only gone down by about 0.5 million km2.

So the answer must be
- I've got the data all wrong, OR
- the data on area is so unreliable as to be unusable, OR
- the positive feedback from ice turning into open ocean is far less than the extent loss indicates

or a mixture of the above
I've had a quick scan of June and September and it is sort of the same.

[oren]

I had the same problem with area recently and it turned out to be the pole hole. Make sure your data compensates for it.

[gerontocrat]

The pole hole is assumed 100% covered in ice (extent and area)? If so, it has no effect on that the data shows that extent is reducing far more than area? Especially as it is March averages in the table below.

The data is from the NSIDC spreadsheet - I will have to look at the documentation.

[Juan C. García]

The pole hole is assumed 100% covered in ice (extent and area)?

I have not follow area since Cryosphere Today stopped publishing. A shame, because I like area more than extent.

I recommend read all this subject:

4.2.3 Arctic Pole Hole
4.2.3.1 Relevance of the Arctic Pole Hole to Ice Extent and Ice Area Values
...
The holes are significant because, in calculating Northern Hemisphere ice extent, it is assumed that the entire region under the Arctic pole hole is covered by ice at greater than 15 percent concentration. In calculating Northern Hemisphere ice area, however, the region under the Arctic pole hole is not included.

http://nsidc.org/data/G02135
[Page 37]

Wipneus knows a lot about area. I hope he can help us with that. Wipneus also follows one or more sources of area data. By example, download the following file:

https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/data/nsidc_arc_nt_main.txt?attredirects=0

[oren]

So indeed the area and extent numbers in the NSIDC spreadsheet are not consistent. If you add the following values to the area numbers you should be fine:
http://nsidc.org/data/G02135?qt-data_set_tabs=2#qt-data_set_tabs
Page 37 in the user guide.

Table 8. Arctic Pole Hole Mask Sizes and Dates
Arctic pole hole Area (million km2)
SSMIS Arctic Pole Hole Mask, 0.029, January 2008 to present
SSM/I Arctic pole hole Mask, 0.31, July 1987 through December 2007
SMMR Arctic pole hole Mask, 1.19, November 1978 through June 1987

[Wipneus]

The pole hole is assumed 100% covered in ice (extent and area)?

I have not follow area since Cryosphere Today stopped publishing. A shame, because I like area more than extent.

I was asked to clarify.

Normal practice in calculating extent is assuming concentration within the pole hole is everywhere above the threshold (usually 15%), so counted as 100%.
I have looked into this and I find it a very reasonable assumption in the past, but the errors will get bigger when open water appears near the pole in the, perhaps near, future.

For area the calculations differ. NSIDC monthly area does not include the pole hole. It is causing "steps" with different instruments. That is not good for long term analysis.

Cryosphere Today's area used to estimate concentration inside the pole hole from the concentration in a ring around the hole. My own calculations are similar. For the reasons mentioned above, I hope that makes these data much better for climatic purposes.

Things are of course simpler in the Antarctic.

 

[gerontocrat]

Thanks all for the info. No wonder amateurs like me fall into (polar) bear traps.

Methinks at the moment I will be looking at the perpheral seas and Hudson Bay. No pole holes to fall in for the unwary explorer.

But the Arctic no doubt has more surprises up its sleeve.

Cheers.

[TerryM]

Thanks to both Jim & Steve we now have access to the correct data. This is how it's supposed to work!


Congrats & thanks to both.
Terry

[Juan C. García]

I was asked to clarify.

Thank you Wipneus!


JAXA April 9^th, 2018: 13,321,482 km², a drop of -21,892 km².
2018 is 3^rd lowest on record:
     169,803 km² above 2016
         7,114 km² above 2006

[gerontocrat]

Hullo Oren, hullo Wipneus.

Sorry to nag but just one bit more of clarification, please, pretty please.

A quick look at NSIDC regional data and the map suggests the pole hole is entirely contained within the Central Arctic Ocean. Is that correct?

Interesting, if off-topic, that that is the only bit of the Arctic Ocean outside the 200 mile economic zone of any of the surrounding countries ? Though Russia is, I think still after extending its economic zone as far as the North Pole.

[oren]

A quick look at NSIDC regional data and the map suggests the pole hole is entirely contained within the Central Arctic Ocean. Is that correct?

Yes.

[Juan C. García]

JAXA April 10^th, 2018:   13,281,980 km², a drop of -39,502 km².
2018 is second lowest on record again:
     2018 is 175,869 km² above 2016.
     2018 is   25,144 km² below 2006.

[gerontocrat]

Herewith JAXA DATA AS AT 10 APRIL 2018. to add to Juan's post

2018 extent is also below 2017 by 36,924 km2.
Extent loss from maximum to date is just 20k more than average.

if remaining loss was average, the minimum would be just under 4 million km2.
But:-
- on average only 6 percent of the melting is done,
- excluding the 2012 outlier, remaining melt would result in a minimum of about 4.2 million km2.

[gerontocrat]

So indeed the area and extent numbers in the NSIDC spreadsheet are not consistent. If you add the following values to the area numbers you should be fine:

Table 8. Arctic Pole Hole Mask Sizes and Dates
Arctic pole hole Area (million km2)
SSMIS Arctic Pole Hole Mask, 0.029, January 2008 to present
SSM/I Arctic pole hole Mask, 0.31, July 1987 through December 2007
SMMR Arctic pole hole Mask, 1.19, November 1978 through June 1987

Thanks, so I did. Results below. For most purposes it would seem extent is a good proxy for area when looking at trends. I am sure purists will be howling in utter fury at such a remark.

[gerontocrat]

In the above post I should have said "For most purposes it would seem extent is a good proxy for area when looking at OVERALL trends".

Below are 2 tables from NSIDC Regional Sea data as at 10 April (peripheral seas)
The first is extent, the second is area. Differences, especially in percentage terms, are very large.

[Juan C. García]

JAXA, April 11^th, 2018:  13,254,107 km², a drop of -27,873 km².
2018 is now the third lowest on record.

Interesting, on April 11^th, the three lowest years are the last ones.
2018 is 135,226 km² above 2016.
2018 is  3,623 km² above 2017.

2018 could become the lowest on record on the following 5 days.
Afterwards, 2016 starts a deep downward trend.

[Alexander555]

We are waiting.

[Juan C. García]

We are waiting.

ADS NIPR (JAXA) has not updated the data... 

https://ads.nipr.ac.jp/vishop/#/extent

[Alexander555]

Gerontocrat's graph from NSIDC shows a drop of 91 000 km2 for the 12th. And on your last graph it looks like 2016 is moving up a little.

[gerontocrat]

JAXA DATA AS AT 13 APRIL 2018  13,255,427 km2

JAXA says extent has stalled in the last 2 days. (Somewhat different from NSIDC data) As a result extent is third lowest, 100k above 2017 and 76 k above 2016. With on average 7% of melting done, extent loss is 50k below average, leading to a minimum of 3.98 million km2.

[Neven]

JAXA says extent has stalled in the last 2 days.

Are we about to see a century break in the next few days?

[gerontocrat]

JAXA says extent has stalled in the last 2 days.

Are we about to see a century break in the next few days?

Perhaps not but on the other hand warmth entering from the Bering sea (images below)

( Does this make me a doubting Thomas ? )

[Daniel B.]

That is finally a more typical temperature pattern; although slightly colder in the central U.S., and warmer in eastern Europe.

[bbr2314]

That is finally a more typical temperature pattern; although slightly colder in the central U.S., and warmer in eastern Europe.

Those are high temps across the US/Canada... this is not a typical pattern. We are still at record continental SWE and it is 4/13.

[Daniel B.]

I thought that was a time stamp plot with the current temperatures measured at the time posted.

[bbr2314]

I thought that was a time stamp plot with the current temperatures measured at the time posted.

It is, but 18z is 2PM EST which is normally when the highs occur. I would also recommend avoiding the GFS for anything but short-range forecasts in parts of the Lower 48 removed from any sensible substantial snowcover.

[gerontocrat]

JAXA ARCTIC EXTENT 13,125,342 km2（April 15, 2018） down 72k and 58k over the last two days.

Extent is 6k above 2017 and 8k below 2016. Extent loss to date totally average.

[Neven]

Not a century break, but more or less what I expected after the short lull.

[Wipneus]

Within the Arctic Basin the way down has not been started, yet.

[gerontocrat]

Hullo Wipneus,

By coincidence, I got around to looking at AREA in the seas that tend to melt later than the seas in the periphery. (Note:- not adjusted for the pole hole)

When looking at extent (1st table below) the answer is - no change, nothing happening.
When looking at area (2nd table below) the answer is - things are moving all over the place even if the net effect is very small.

Another indication of ice mobility? Worth posting every week or so?

Sorry about the size of the tables. When I reduce them to 700 pixels they become more or less unreadable. Click on them and they should display properly.

[Juan C. García]

JAXA April 16th, 2018:  13,052,208 km2. An interesting drop of -73,134 km2, after doing drops of -71,918 and -58,167 km2 the days immediately before.

So, 2018 is the lowest on record again.   

Tomorrow, 2016 starts to have important drops every day. (295K km2 in the following 5 days).
Will 2018 follow 2016? From my point of view, it is bad enough if 2018 stays as second lowest on record, for a couple of months…

[gerontocrat]

NSIDC Regional Sea Ice Data (5 day trailing average) as at 16 April

Extent
The decline continues in the periphery - Decline in extent especially in the Okhotsk.
Extent loss in other seas minimal or zero.

Area
In the periphery following extent decline.
In other seas (e.g. Chukchi, Kara, Laptev) decline in area seems to have commenced.

NSIDC Arctic total  (one-day) as at 16 April
Lowest. Down 96k to 13.686 million km2, just 18k less than 2017 and just 36k less than 2007.

[Juan C. García]

JAXA April 17^th, 2018: 12,985,833 km2. A drop of -66,375 km².
2018 is the JAXA ASI extent lowest on record.

2016 [2^nd lowest] is 73,303 km² above 2018.

[bbr2314]

JAXA April 17^th, 2018: 12,985,833 km2. A drop of -66,375 km².
2018 is the JAXA ASI extent lowest on record.

2016 [2^nd lowest] is 73,303 km² above 2018.

2018 is going to hemorrhage in Okhotsk, Baffin, Bering, Beaufort, and Chukchi over the next thirty days. I would not be surprised to see its lead expanded. 2016 had significantly more volume in the way of the Pacific -- 2018 is in very dire straits, especially ^.

The ATL side in Barentz may actually mask losses as melt is matched by import. But this will probably end by 6/1, at latest.

I do anticipate Hudson Bay will hold up phenomenally well this year, with some ice possibly even making it through summer. But that is still unlikely, and will probably lead to sustained drops in the very late season (late July/August instead of May/June).

[jdallen]

JAXA April 17^th, 2018: 12,985,833 km2. A drop of -66,375 km².
2018 is the JAXA ASI extent lowest on record.

2016 [2^nd lowest] is 73,303 km² above 2018.

2018 is going to hemorrhage in Okhotsk, Baffin, Bering, Beaufort, and Chukchi over the next thirty days. I would not be surprised to see its lead expanded. 2016 had significantly more volume in the way of the Pacific -- 2018 is in very dire straits, especially ^.

The ATL side in Barentz may actually mask losses as melt is matched by import. But this will probably end by 6/1, at latest.

I do anticipate Hudson Bay will hold up phenomenally well this year, with some ice possibly even making it through summer. But that is still unlikely, and will probably lead to sustained drops in the very late season (late July/August instead of May/June).

I wouldn't bet too heavily on Hudson Bay.  Most of that ice is well under 2 meters, and what isn't is still going to be acutely vulnerable.  Late season cold won't be enough to strengthen it against the coming melt.

[bbr2314]

JAXA April 17^th, 2018: 12,985,833 km2. A drop of -66,375 km².
2018 is the JAXA ASI extent lowest on record.

2016 [2^nd lowest] is 73,303 km² above 2018.

2018 is going to hemorrhage in Okhotsk, Baffin, Bering, Beaufort, and Chukchi over the next thirty days. I would not be surprised to see its lead expanded. 2016 had significantly more volume in the way of the Pacific -- 2018 is in very dire straits, especially ^.

The ATL side in Barentz may actually mask losses as melt is matched by import. But this will probably end by 6/1, at latest.

I do anticipate Hudson Bay will hold up phenomenally well this year, with some ice possibly even making it through summer. But that is still unlikely, and will probably lead to sustained drops in the very late season (late July/August instead of May/June).

I wouldn't bet too heavily on Hudson Bay.  Most of that ice is well under 2 meters, and what isn't is still going to be acutely vulnerable.  Late season cold won't be enough to strengthen it against the coming melt.

I think the extraordinary snow amounts across the Canadian Shield will serve to buffer HB against melt for the foreseeable future, as incoming heat loses potency/deposits as snow across either Quebec or Ontario. This will likely change by mid-May or early June at the latest, but I think it will be sufficient to postpone melt-out of HB by a similar duration of the postponement of Canadian snow melt (on the order of 1.5-2 months).

[oren]

I think the extraordinary snow amounts across the Canadian Shield will serve to buffer HB against melt for the foreseeable future, as incoming heat loses potency/deposits as snow across either Quebec or Ontario. This will likely change by mid-May or early June at the latest, but I think it will be sufficient to postpone melt-out of HB by a similar duration of the postponement of Canadian snow melt (on the order of 1.5-2 months).

Your "sense of snow" is generating very strange predictions, but I like it that they are presented clearly. I feel bad about it but I will again take the other side of your bet. HB has been extremely predictable these last few years - most of the melt occurs between mid-June and mid-July, as shown on Wipneus' graph. There is simply no way that melt-out of HB will be postponed by 1.5-2 months, and I predict it will arrive like clockwork on the same schedule, give or take a couple of weeks.

[Sailaway]

Any chance of leaving one thread for data. It is getting a little to much marching through "snow drifts" on every thread. Thanks