Support the Arctic Sea Ice Forum and Blog

Author Topic: IJIS  (Read 2445378 times)

magnamentis

  • Guest
Re: IJIS
« Reply #3500 on: December 04, 2016, 08:46:01 PM »
two notable things for today:

a) the 2016 curve passed the 2006 stall (slowdown) in refreezing without even coming close to a touch

b) OT but notable, a tripple century drop in the antarctic

Espen

  • Young ice
  • Posts: 3528
    • View Profile
  • Liked: 378
  • Likes Given: 2
Re: IJIS
« Reply #3501 on: December 05, 2016, 05:02:16 AM »
IJIS:

10,028,237 km2(December 4, 2016)up 30,631 km2 from previous and lowest measured for the date.
Have a ice day!

DavidR

  • Grease ice
  • Posts: 736
    • View Profile
  • Liked: 32
  • Likes Given: 3
Re: IJIS
« Reply #3502 on: December 05, 2016, 06:03:48 AM »
Bill, I  am using  NSIDC daily  data so the rest of my  reply is off topic
« Last Edit: December 05, 2016, 06:39:41 AM by DavidR »
Toto, I've a feeling we're not in Kansas anymore

Gray-Wolf

  • Grease ice
  • Posts: 922
    • View Profile
  • Liked: 126
  • Likes Given: 389
Re: IJIS
« Reply #3503 on: December 05, 2016, 12:25:34 PM »
Looking at the SST anom for Baffin I wonder if we have other 'peripheral' areas, that normally freeze, that will struggle to do so this year?
KOYAANISQATSI

ko.yaa.nis.katsi (from the Hopi language), n. 1. crazy life. 2. life in turmoil. 3. life disintegrating. 4. life out of balance. 5. a state of life that calls for another way of living.
 
VIRESCIT VULNERE VIRTUS

6roucho

  • Frazil ice
  • Posts: 296
  • Finance geek
    • View Profile
  • Liked: 0
  • Likes Given: 1
Re: IJIS
« Reply #3504 on: December 05, 2016, 12:35:49 PM »

... One kilogram of methane is 21x as effective at trapping heat in the earth's atmosphere as a kilogram of carbon dioxide within 100 years ...

My understanding (always very limited) is that a more recent estimate puts the GWP100 value for methane at either 28 or 34, depending whether or not climate carbon feedbacks are considered.
21 -> 28 or 34 is a huge change in physical terms. Every climate risk vector seems to provide OMG adjustments at the moment.

Shared Humanity

  • Guest
Re: IJIS
« Reply #3505 on: December 05, 2016, 03:24:33 PM »
Yikes! Lets hope that is one day of slow gain and not the beginning of another week long stall.

magnamentis

  • Guest
Re: IJIS
« Reply #3506 on: December 05, 2016, 06:55:49 PM »
crossposting with freezing thread, belongs to both:

stall and/or setback seems to be imminent, let's see.


Espen

  • Young ice
  • Posts: 3528
    • View Profile
  • Liked: 378
  • Likes Given: 2
Re: IJIS
« Reply #3507 on: December 06, 2016, 05:22:23 AM »
IJIS:

10,046,572 km2(December 5, 2016)up 18,335 km2 from previous and lowest measured for the date.
Have a ice day!

gregcharles

  • New ice
  • Posts: 95
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: IJIS
« Reply #3508 on: December 06, 2016, 05:29:32 AM »
Damn it. I know one day is insignificant, but I was really hoping for a return to large gains. Well, maybe tomorrow.

Tigertown

  • Nilas ice
  • Posts: 1676
    • View Profile
  • Liked: 21
  • Likes Given: 18
Re: IJIS
« Reply #3509 on: December 06, 2016, 05:35:51 AM »
SST's too high in too many places. Ice doesn't have much room for growth.
"....and the appointed time came for God to bring to ruin those ruining the earth." Revelation 11:18.

Juan C. García

  • Young ice
  • Posts: 2828
    • View Profile
  • Liked: 1173
  • Likes Given: 915
Re: IJIS
« Reply #3510 on: December 06, 2016, 05:38:39 AM »
591,302 km2 between 2016 and 2006 -now second on record- seems a huge difference. Only two days in which 2016 slowed down, while 2006 increased significantly.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Cato

  • New ice
  • Posts: 62
    • View Profile
  • Liked: 2
  • Likes Given: 0
Re: IJIS
« Reply #3511 on: December 06, 2016, 10:43:12 AM »
Agree with Tigertown: a lot of "effort" has been spent by the Arctic to cool up the waters in Barents and Kara, where positive anomalies have been very high, and for very long time.

So far, the relatively cold conditions in that area have just led to a decrease in the anomaly, but no additional ice. This process will be ongoing for the next few days, about one week, before very mild air is conveyed up there by the LP systems developing in the Atlantic and moving NE.

In the next days, though, a significant contribution to ice extension will be provided by Hudson, where conditions will turn extremely cold after the collapse of the polar vortex over North America. There's about 1 million kmq to freeze in Hudson, and they're coming soon.

charles_oil

  • Frazil ice
  • Posts: 337
    • View Profile
  • Liked: 38
  • Likes Given: 74
Re: IJIS
« Reply #3512 on: December 06, 2016, 01:37:02 PM »
Lets hope so - Climate re-analyser still shows a +10deg anomaly in a weeks time from now, so freezing, but not very hard.  I guess when it freezes - it happens fast. 2012 looks like it took about a month - NSIDC Chartic.

http://cci-reanalyzer.org/wxrmaps/#GFS-025deg.ARC-LEA.T2_anom


pauldry600

  • Frazil ice
  • Posts: 240
    • View Profile
    • weathergossip
  • Liked: 24
  • Likes Given: 3
Re: IJIS
« Reply #3513 on: December 06, 2016, 02:36:07 PM »
Hudson may begin to freeze but the Atlantic run along Western Europe is showing very mild for most of December so it wont be freezing here.

Our Winter is over til 2017 here in Ireland IMO.

16c tomorrow after -7.3c in November

Giant high settling over Europe steering mild moist weather over us until Christmas.

Microtom

  • New ice
  • Posts: 1
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: IJIS
« Reply #3514 on: December 06, 2016, 08:04:41 PM »
Look, I added a line to give some more perspective. Oh and hello, first post.

« Last Edit: December 06, 2016, 10:40:37 PM by Microtom »

Csnavywx

  • Grease ice
  • Posts: 557
    • View Profile
  • Liked: 78
  • Likes Given: 2
Re: IJIS
« Reply #3515 on: December 06, 2016, 08:45:24 PM »
With the upcoming -WPO (West Pacific Oscillation) pattern, the primary trop. polar vortex is forecast to be driven into central Canada (over the Husdon). That should cause a rapid freeze-up of the Bay and a closing of the gap (of which the Husdon is a significant component now). However, this will be offset somewhat by strong heat transport into the Pacific side of the Arctic.

charles_oil

  • Frazil ice
  • Posts: 337
    • View Profile
  • Liked: 38
  • Likes Given: 74
Re: IJIS
« Reply #3516 on: December 07, 2016, 12:21:35 AM »
Predicted higher than normal Hudson Bay temps running into late December though...

http://www.aer.com/science-research/climate-weather/arctic-oscillation

Figure 8. Forecasted surface temperature anomalies (°C; shading) from 16 – 20 December 2016. Note the warm temperatures for far Eastern Canada and Northern Europe with cold temperatures in much of Northern Asia and western Canada and the Eastern US.   The forecast is from the 00Z 5 December 2016 GFS ensemble.

Espen

  • Young ice
  • Posts: 3528
    • View Profile
  • Liked: 378
  • Likes Given: 2
Re: IJIS
« Reply #3517 on: December 07, 2016, 05:05:14 AM »
IJIS:

10,084,594 km2(December 6, 2016)up 38,822 km2 from previous and lowest measured for the date.
Have a ice day!

Csnavywx

  • Grease ice
  • Posts: 557
    • View Profile
  • Liked: 78
  • Likes Given: 2
Re: IJIS
« Reply #3518 on: December 07, 2016, 05:34:17 AM »
Predicted higher than normal Hudson Bay temps running into late December though...

http://www.aer.com/science-research/climate-weather/arctic-oscillation

Figure 8. Forecasted surface temperature anomalies (°C; shading) from 16 – 20 December 2016. Note the warm temperatures for far Eastern Canada and Northern Europe with cold temperatures in much of Northern Asia and western Canada and the Eastern US.   The forecast is from the 00Z 5 December 2016 GFS ensemble.

Those +anomalies are due to the lack of ice. The GFS/GEFS takes a snapshot at the beginning of the run (initialization) and doesn't forecast ice cover changes during its run. So it will be biased a bit high for this time frame.

jdallen

  • Young ice
  • Posts: 3297
    • View Profile
  • Liked: 580
  • Likes Given: 217
Re: IJIS
« Reply #3519 on: December 07, 2016, 06:07:53 AM »
Predicted higher than normal Hudson Bay temps running into late December though...

http://www.aer.com/science-research/climate-weather/arctic-oscillation

Figure 8. Forecasted surface temperature anomalies (°C; shading) from 16 – 20 December 2016. Note the warm temperatures for far Eastern Canada and Northern Europe with cold temperatures in much of Northern Asia and western Canada and the Eastern US.   The forecast is from the 00Z 5 December 2016 GFS ensemble.

Those +anomalies are due to the lack of ice. The GFS/GEFS takes a snapshot at the beginning of the run (initialization) and doesn't forecast ice cover changes during its run. So it will be biased a bit high for this time frame.
Yuppers.  Hudson's Bay is a sideshow mostly, except in so far as it can melt early and affect Baffin and the CAA indirectly.  High temps there don't really surprise me, and I'm actually expecting it to freeze up rapidly in a couple of weeks.

With the torquing of the polar vortex, I actually expect the bay to freeze up pretty well.  However, that's not where we need the ice, as it will be pretty much gone by August at the latest.  The real show will be the lack of general thickening, the Bering and the "Atlantic Front".
This space for Rent.

magnamentis

  • Guest
Re: IJIS
« Reply #3520 on: December 08, 2016, 03:17:46 AM »
IJIS:

10,046,572 km2(December 5, 2016)up 18,335 km2 from previous and lowest measured for the date.

that much about the current curve touching earlier years by mid december, simply forget it folks, we'll be lucky if the current curve will ever touch any older one before february 2017 if at all. let's see.

Pmt111500

  • Guest
Re: IJIS
« Reply #3521 on: December 08, 2016, 04:40:03 AM »
Meh. Compaction and possible melt as A-team said. Week or two? Temperatures should drop soon as the main pack gets solid... Or as solid it can get... The winters nowadays are nothing like winters in my youth.

Espen

  • Young ice
  • Posts: 3528
    • View Profile
  • Liked: 378
  • Likes Given: 2
Re: IJIS
« Reply #3522 on: December 08, 2016, 05:22:41 AM »
IJIS:

10,177,212 km2(December 7, 2016)up 92,618 km2 from previous and lowest measured for the date.
Have a ice day!

Bill Fothergill

  • Frazil ice
  • Posts: 278
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: IJIS
« Reply #3523 on: December 08, 2016, 02:36:22 PM »
In certain quarters, there is an ongoing interest in the behaviour of average extent (typically annual average) and the way it is decreasing over time.

I therefore put some numbers together on a simple spreadsheet to produce the charts appended below.

As this is an IJIS thread, I obviously used the data from that source. However, instead of just plotting the moving average for a 12 month window, I also displayed the average over 2, 3, 4 and 5 years.

There are several things worth noting...

1) The one-year average is particularly prone to violent changes in its gradient. At present, the violent downward trajectory is due to the fact that "relatively" high daily values from 2015 are being replaced by record low values in 2016. Such "low hanging fruit" will not continue indefinitely.

2) The 2-year average has dropped below the 10 million sq kms mark. Apart from 2016, the only time this has happened even for a 1-year average was at 2012/13. The current 2-year average is now less than 30k above the lowest 1-year value attained in 2012/13.

3) Although the gradient of the curves can look precipitous on an expanded Y-axis scale, the lower chart puts into perspective how far away things are from approaching an average anywhere near zero.


Cato

  • New ice
  • Posts: 62
    • View Profile
  • Liked: 2
  • Likes Given: 0
Re: IJIS
« Reply #3524 on: December 08, 2016, 03:38:27 PM »
There's no much to say, especially after the latest update from PIOMAS (and the very nice and professional summary by Neven, as usual). On a synoptic level, though, the situation does not appear desperate to me, in perspective. At least with reference to extension.

In the next 7-10 days I expect the complete refreeze of Hudson, which accounts alone for almost 1 million kmq. Moreover, fairly cold conditions will persist over Kara and (partially) Barents, with consequent decrease of positive temperature anomalies, which actually have been decreasing significantly in the last couple of weeks. There's potential for further 0.5 million kmq in the next 7-10 days upd there, IMHO.

With a view to the above, I wouldn't be surprised if 2016  recovered a significant part of the gap with the top years, in the next couple of weeks. Which does not mean, of course, that the patient is gonna be healed, as we all know...

I wanna be optimistic, though, and I'll put my two cents on a recovery of the gap within the 20th of December, however unrealistic this forecast might sound...

Bill Fothergill

  • Frazil ice
  • Posts: 278
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: IJIS
« Reply #3525 on: December 08, 2016, 04:59:13 PM »
In order to put a bit more context around the graphs I recently posted at comment #3524, I should, of course, have provided the following historic data pertaining to annual average extent...

Ave 1980-89 ... 11.957 millions sq kms
Ave 1990-99 ... 11.440 millions sq kms
Ave 2000-09 ... 10.773 millions sq kms

Depending upon which day one measures it, the average annual extent from 2010 until now is around 10.14 (and dropping) million sq kms.

That comes out at a loss rate of roughly -600k sq kms/decade. (For comparison, the equivalent NSIDC value for the period 1979 until now is about -542k sq kms/decade.)

ktonine

  • Frazil ice
  • Posts: 363
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: IJIS
« Reply #3526 on: December 08, 2016, 11:59:16 PM »
In the next 7-10 days I expect the complete refreeze of Hudson ...

Hudson Bay didn't completely freeze over last year until the first week of January.  On December 8th last year it was approximately 60% covered.  This year it's probably closer to 15%.   And let's not forget that Hudson Bay extends all the way to 50N. 

I will be extremely, EXTREMELY surprised if it's completely frozen over this month.

pikaia

  • Frazil ice
  • Posts: 358
    • View Profile
  • Liked: 94
  • Likes Given: 39
Re: IJIS
« Reply #3527 on: December 09, 2016, 12:06:44 AM »
I will be extremely, EXTREMELY surprised if it's completely frozen over this month.
Me too - the temperature forecast for the coming week is for temperatures well above average.

Tigertown

  • Nilas ice
  • Posts: 1676
    • View Profile
  • Liked: 21
  • Likes Given: 18
Re: IJIS
« Reply #3528 on: December 09, 2016, 12:53:27 AM »
I am absolutely no good at distinguishing various shades of a color. Can someone look and tell what the SST is for the lower Hudson Bay? From the 4th of this month, so it's current.
"....and the appointed time came for God to bring to ruin those ruining the earth." Revelation 11:18.

Csnavywx

  • Grease ice
  • Posts: 557
    • View Profile
  • Liked: 78
  • Likes Given: 2
Re: IJIS
« Reply #3529 on: December 09, 2016, 01:03:46 AM »
I will be extremely, EXTREMELY surprised if it's completely frozen over this month.
Me too - the temperature forecast for the coming week is for temperatures well above average.

Yes, but again, that's not due to ambient synoptic conditions, which will be very cold. If you don't believe that, take a look at forecast 850mb temperatures. They'll be in the neighborhood of -20 to -25C, meaning delta-Ts over the Bay of 20-27C, which should produce abundant sea-effect snow and convective plumes. The surface temperature will be well above normal until it freezes, which should be pretty quick with delta values that high. As such, the 10+ day outlooks will be biased high temperature-wise, because again -- NWP models do not forecast ice cover changes during their runs. This typically doesn't matter when you're only talking about a few days (when they're the most useful), but it matters when someone posts a 2-week forecast.

Regardless, the main action is over the Pacific side of the Arctic Ocean, where the -WPO ridge looks to almost outright prevent ice formation for a couple of weeks.

charles_oil

  • Frazil ice
  • Posts: 337
    • View Profile
  • Liked: 38
  • Likes Given: 74
Re: IJIS
« Reply #3530 on: December 09, 2016, 01:04:10 AM »
Bill -
That comes out at a loss rate of roughly -600k sq kms/decade. (For comparison, the equivalent NSIDC value for the period 1979 until now is about -542k sq kms/decade.)

As the last period (drop of 633 sq km in just under 7 years)  - I made it loss rate of around 638k sq kms/decade - and accelerating.  Or have I missed something?

DrTskoul

  • Nilas ice
  • Posts: 1455
    • View Profile
  • Liked: 210
  • Likes Given: 60
Re: IJIS
« Reply #3531 on: December 09, 2016, 01:11:11 AM »
I am absolutely no good at distinguishing various shades of a color. Can someone look and tell what the SST is for the lower Hudson Bay? From the 4th of this month, so it's current.


Above 0oC

Tigertown

  • Nilas ice
  • Posts: 1676
    • View Profile
  • Liked: 21
  • Likes Given: 18
Re: IJIS
« Reply #3532 on: December 09, 2016, 01:25:56 AM »
I should have noticed  this chart, as it actually has temps. on it. It Shows 0oC for the upper region of Hudson Bay and 2oC for the lower.So there is a range between 0 and 2. That may take a while to cool.
"....and the appointed time came for God to bring to ruin those ruining the earth." Revelation 11:18.

TerryM

  • First-year ice
  • Posts: 6002
    • View Profile
  • Liked: 893
  • Likes Given: 5
Re: IJIS
« Reply #3533 on: December 09, 2016, 01:52:05 AM »
TT
Bear in mind that James Bay is much fresher than Hudson Bay & will freeze at a higher temperature.


Terry

Tigertown

  • Nilas ice
  • Posts: 1676
    • View Profile
  • Liked: 21
  • Likes Given: 18
Re: IJIS
« Reply #3534 on: December 09, 2016, 02:04:11 AM »
That is definitely something I didn't know, but I think that the slightly warmer water goes well north of it. It could freeze first, though. It appears that it has frozen in the past ahead of higher Latitudes.
"....and the appointed time came for God to bring to ruin those ruining the earth." Revelation 11:18.

ktonine

  • Frazil ice
  • Posts: 363
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: IJIS
« Reply #3535 on: December 09, 2016, 02:08:30 AM »
It Shows 0oC for the upper region of Hudson Bay and 2oC for the lower.So there is a range between 0 and 2. That may take a while to cool.

Tigertown - I agree it will take some time for the region shown to freeze, but that's not a map of all of Hudson Bay - only the southern 60%.  It looks like 60N is it's boundary.  Rathern than the 'upper region' it's more like the central region.

Compare to the full map of Hudson Bay:


DrTskoul

  • Nilas ice
  • Posts: 1455
    • View Profile
  • Liked: 210
  • Likes Given: 60
Re: IJIS
« Reply #3536 on: December 09, 2016, 02:14:49 AM »
It Shows 0oC for the upper region of Hudson Bay and 2oC for the lower.So there is a range between 0 and 2. That may take a while to cool.

Tigertown - I agree it will take some time for the region shown to freeze, but that's not a map of all of Hudson Bay - only the southern 60%.  It looks like 60N is it's boundary.  Rathern than the 'upper region' it's more like the central region.

Compare to the full map of Hudson Bay:



The original sst map is very distorted due to the projection. I think both are showing the same bay boundary.

Tigertown

  • Nilas ice
  • Posts: 1676
    • View Profile
  • Liked: 21
  • Likes Given: 18
Re: IJIS
« Reply #3537 on: December 09, 2016, 02:15:41 AM »
I desperately tried to find a better one with NOAA  or someone else trustworthy. And with enough detail.
"....and the appointed time came for God to bring to ruin those ruining the earth." Revelation 11:18.

DrTskoul

  • Nilas ice
  • Posts: 1455
    • View Profile
  • Liked: 210
  • Likes Given: 60
Re: IJIS
« Reply #3538 on: December 09, 2016, 02:23:34 AM »
Not better ... Just additional info and forecast/analysis..zoom at hudson bay


« Last Edit: December 09, 2016, 02:35:37 AM by DrTskoul »

Espen

  • Young ice
  • Posts: 3528
    • View Profile
  • Liked: 378
  • Likes Given: 2
Re: IJIS
« Reply #3539 on: December 09, 2016, 05:07:54 AM »
IJIS:

10,249,717 km2(December 8, 2016)up 72,505 km2 from previous and lowest measured for the date.
Have a ice day!

johnm33

  • Guest
Re: IJIS
« Reply #3540 on: December 09, 2016, 03:04:43 PM »
This shows temps about an hour ago, also product dataset and variable

available here http://marine.copernicus.eu/services-portfolio/access-to-products/

Tigertown

  • Nilas ice
  • Posts: 1676
    • View Profile
  • Liked: 21
  • Likes Given: 18
Re: IJIS
« Reply #3541 on: December 09, 2016, 03:52:45 PM »
That is really nice. That's the kind of detail you need.
« Last Edit: December 09, 2016, 03:59:25 PM by Tigertown »
"....and the appointed time came for God to bring to ruin those ruining the earth." Revelation 11:18.

dnem

  • Grease ice
  • Posts: 680
    • View Profile
  • Liked: 310
  • Likes Given: 261
Re: IJIS
« Reply #3542 on: December 09, 2016, 05:23:44 PM »
Been playing with a visualization of the IJIS data.  Will describe if it posts ok.

dnem

  • Grease ice
  • Posts: 680
    • View Profile
  • Liked: 310
  • Likes Given: 261
Re: IJIS
« Reply #3543 on: December 09, 2016, 05:36:29 PM »
Looks OK.  This is an daily extent change anomaly map of all seasons from 1989 to current.  The first thing I did is fill in any data gaps with simple linear interpolation.  Then I expressed each day's extent as the percent change from the previous day's extent.  I then created a "baseline" by averaging the daily change for all years between 1989 and 2005 and smoothed that with a 5-day running average.  Finally, each day in the data set is expressed as the deviation from the baseline.  The color map is from Excel's 3 level Conditional Formatting with the largest positive anomaly Green, no anomaly yellow and the largest negative anomaly Red. 

You can certainly see how the recent big melt years packed on new extent much faster in the fall after the summer, for example.  You can also see how anomalous this years late Sep/early Oct  and mid-November melts are.  This year also featured a strong early extent gain in September compared to other years.  Curious feature in the data set in 1995 in Sep/Oct (big melt followed by fast freeze).

Bill Fothergill

  • Frazil ice
  • Posts: 278
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: IJIS
« Reply #3544 on: December 09, 2016, 09:32:35 PM »
Bill -
That comes out at a loss rate of roughly -600k sq kms/decade. (For comparison, the equivalent NSIDC value for the period 1979 until now is about -542k sq kms/decade.)

As the last period (drop of 633 sq km in just under 7 years)  - I made it loss rate of around 638k sq kms/decade - and accelerating.  Or have I missed something?

Charles, for that "roughly -600k sq kms/decade" figure from the IJIS/JAXA/ADS dataset, I didn't even bother doing any formal calculation. The 1980's average (11.957 million sq kms) was just over 1.8 million sq kms above the 2015 year-end average of 10.111 million sq kms. Those two "end-point" numbers imply that each year - when averaged across the dataset and assuming a linear trend -  the annual average drops by just over 60k sq kms.

The point I was trying to make, but clearly failed to adequately do so, was that the current level of annual average extent (~10,000k) is more than of an order of magnitude in excess of the decadal drop rate (600k). For such a purpose, the difference between 600k and 638k is largely irrelevant. (Although I totally agree that this value is increasing - and will continue to do so.)

I should have been more explicit in placing this in the context of a suggestion that has been made on this thread, namely that the annual average could drop to Zero within 6 or 7 years. For this to happen, the annual drop, averaged over the next 6 or 7 years, would need to become almost as large as the total drop seen thus far.

The point of the first chart (comment #3524) was to show that the trend swings wildly up and down, and that therefore it is something of a folly to say that "this time it's for real, and we can project this particular value of the trend into the future". The huge drop seen in the 1-year rolling annual average in 2007, and the gentler but deeper drops in 2011 and across the 2012/13 periods failed to show any staying power - so why should this time be different?

The purpose of the second chart was to show just how much there is still to go before we get anywhere near a zero annual average.

Had I been aiming to produce a trend value with greater precision (but not necessarily of greater accuracy) I would used my old faithful friend - Excel's SLOPE function. However, when one is working with a mixture of both annual and decadal averages, it becomes necessary to give some consideration to just where along the X-axis the various data points appear. Normally I treat annually averaged data as occurring on the middle of the relevant year. However, for consistency, the decadal average should then be treated as occurring at the boundary of the 5th and 6th year. For example, the 1980's average would be treated as being located at 31st Dec 1984 (or 1st Jan 1985). As the 2015 data point should be tied to the mid-year, it means that there is effectively a 30.5 year range spanning the 1980's average and the 2015 average.

As the data within the .csv file only has decadal values for its early years, I felt that using SLOPE would perforce attach a level of "legitimacy" to any result that the granularity of the early years simply did not justify.

I added the NSIDC figures merely to show that these were pretty similar to the "rough & ready" value I had just obtained using the JAXA/IJIS data.

For the NSIDC figures, I used their monthly dataset from...
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/

To obtain an end-of-year annual average, I simply averaged the 12 relevant monthly values. (I know that's only an approximation, and that February in particular is therefore excessively weighted. However, as this effect applies to each year, it tends to cancel out when one is looking for a trend in annual averages values.) This simple approach was adopted purely for expediency in this case. On another spreadsheet that I use, I have weighted each month according to its actual number of days. However, the difference is pretty marginal.

I then used Excel's SLOPE function on the 1979 - 2016 annual averages thus obtained to derive the drop rate of around 542k sq kms/decade. (NB As 2016 is obviously not over yet, I plugged in a stop-gap value for the most recent 12 months, i.e. Dec 2015 - Nov 2016. As December this year is looking as though it will average out considerably less than Dec 2015, that decadal drop rate figure will probably end up being closer to 548k sq kms.)

crandles

  • Young ice
  • Posts: 3153
    • View Profile
  • Liked: 221
  • Likes Given: 69
Re: IJIS
« Reply #3545 on: December 09, 2016, 10:52:50 PM »

The point I was trying to make, but clearly failed to adequately do so, was that the current level of annual average extent (~10,000k) is more than of an order of magnitude in excess of the decadal drop rate (600k). For such a purpose, the difference between 600k and 638k is largely irrelevant. (Although I totally agree that this value is increasing - and will continue to do so.)

I should have been more explicit in placing this in the context of a suggestion that has been made on this thread, namely that the annual average could drop to Zero within 6 or 7 years. For this to happen, the annual drop, averaged over the next 6 or 7 years, would need to become almost as large as the total drop seen thus far.

The point of the first chart (comment #3524) was to show that the trend swings wildly up and down, and that therefore it is something of a folly to say that "this time it's for real, and we can project this particular value of the trend into the future". The huge drop seen in the 1-year rolling annual average in 2007, and the gentler but deeper drops in 2011 and across the 2012/13 periods failed to show any staying power - so why should this time be different?

The purpose of the second chart was to show just how much there is still to go before we get anywhere near a zero annual average.

For the annual average to be zero the Arctic would need to be ice free in Winter.

Ice free in Sept and ice free in winter are likely to be a good long time apart.

Looking at the annual average seems to me to be unlikely to be a good way to get any feel for when an ice free summer will occur.

I agree with you, if what you are trying to show is that an ice free winter is a lot longer than 7 years off. But you don't seem to be distinguishing between ice free in summer and ice free in winter.


Bill Fothergill

  • Frazil ice
  • Posts: 278
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: IJIS
« Reply #3546 on: December 10, 2016, 12:05:45 AM »

For the annual average to be zero the Arctic would need to be ice free in Winter.

Ice free in Sept and ice free in winter are likely to be a good long time apart.

Looking at the annual average seems to me to be unlikely to be a good way to get any feel for when an ice free summer will occur.

I agree with you, if what you are trying to show is that an ice free winter is a lot longer than 7 years off. But you don't seem to be distinguishing between ice free in summer and ice free in winter.


I do realise that it can be difficult to tie together all the stuff that gets stated on a thread - especially a seriously long thread such as this one.

In answer to your comment, I would merely point out that, about 3 weeks ago, I discussed the fact that the Arctic must perforce exhibit seasonal (i.e. summer/autumn) ice free conditions prior to any possibility of this becoming the year-long normal.

Please see page 68 of this thread at Comment #3376.

The relevant text reads...

"The projection (prediction?) made by viddaloo of a totally ice free Arctic in 2023 does not stand up to any serious scrutiny. Currently, the IJIS/ADS rolling annual average extent is dropping by around 3,000 sq kms each day. That comes about because today's value is approximately 1.1 million sq kms lower that the equivalent day's value in 2015. For as long as the differential between the 2016 extent and the same day's extent last year remains at about 1.1 million sq kms, the daily rate of change in the annual average extent will remain the same - i.e. dropping by about 3,000 sq kms each day.

However, there is absolutely no physical reason to suppose that, for the next 7 years, the daily extent will continue to be clocked up at 1.1 million sq kms below the value recorded on the same day of the previous year.

Even worse, the situation is mathematically impossible. Should, by some miracle, the 1.1 million offset from the previous year continue for the next 45 months, then, by late August 2020, the daily value will hit zero. As it is somewhat difficult to have a negative value for extent, the projection simply cannot continue in an unmodified form beyond that point. It simply does not make mathematical - never mind physical - sense.
"

oren

  • Moderator
  • First-year ice
  • Posts: 8299
    • View Profile
  • Liked: 3219
  • Likes Given: 3309
Re: IJIS
« Reply #3547 on: December 10, 2016, 01:36:38 AM »
For a long time Vidaloo has been touting the use of averages and their extrapolation to predict a year-round ice free arctic a few years down the line, a very wrong approach when averaging numbers that have very different underlying physics, such as winter ice cover and summer ice cover. Looking at average July-September ice cover could give more insights.

Espen

  • Young ice
  • Posts: 3528
    • View Profile
  • Liked: 378
  • Likes Given: 2
Re: IJIS
« Reply #3548 on: December 10, 2016, 09:59:03 AM »
IJIS:

10,365,460 km2(December 9, 2016)up 115,743 km2 from previous and lowest measured for the date.
Have a ice day!

oren

  • Moderator
  • First-year ice
  • Posts: 8299
    • View Profile
  • Liked: 3219
  • Likes Given: 3309
Re: IJIS
« Reply #3549 on: December 10, 2016, 12:59:11 PM »
For a long time Vidaloo has been touting the use of averages and their extrapolation to predict a year-round ice free arctic a few years down the line, a very wrong approach when averaging numbers that have very different underlying physics, such as winter ice cover and summer ice cover. Looking at average July-September ice cover could give more insights.
Because he has a commercial interest on doing it
Really? What is it?