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Wipneus

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Re: 2016 sea ice area and extent data
« Reply #300 on: May 27, 2016, 05:51:24 PM »
Shadow CT-area report:

day  CT-date       NH               SH                Global
Thu 2016.3945 -119.5  9.777306  +47.7  8.608370   -71.8 18.385676
Fri 2016.3973  -63.8  9.713496  +71.0  8.679335    +7.2 18.392831
Sat 2016.4000  -66.6  9.646929  +27.5  8.706805   -39.1 18.353734
Sun 2016.4027 -100.8  9.546090  +83.4  8.790235   -17.4 18.336325

The main supporters of the century are the CAB (-40k) and Kara (-22k). Greenland Sea, Hudson and Chukchi  contribute -12k each. ESS went up by +27k.

Shadow NSIDC extent is 11.3607 a drop of "only" -18.5k.

Area dropping faster than extent, means compactness of the ice is going down. That is, if sustained, an indication that surface melting is setting in. See for instance the compactness graph:
https://sites.google.com/site/arctischepinguin/home/amsr2/grf/amsr2-compact-compare.png

The attached delta map gives an overview.

Jim Pettit

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Re: 2016 sea ice area and extent data
« Reply #301 on: May 27, 2016, 06:40:18 PM »
If the remainder of the 2016 melt season were to follow the trajectory of two other years in the satellite era, a new record minimum in Arctic sea ice area would be set (if not altogether shattered):

YEAR   MINIMUM    DAYS BELOW THE PREVIOUS RECORD
-------------------------------------------------------------
2007    1.97 M        43
2012    1.56 M        45



Thanks, as always, Wipneus.
« Last Edit: May 27, 2016, 06:45:55 PM by Jim Pettit »

Richard Rathbone

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Re: 2016 sea ice area and extent data
« Reply #302 on: May 27, 2016, 06:56:05 PM »

..., will there be the June drop due the melt ponds this year too, now that CT is having issues? Is it seen in the Wipneus' numbers of area?

Shadow CT will show it if the new satellite calibration is aligned by then. Home brew shows a much smaller melt pond effect.

Pmt111500

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Re: 2016 sea ice area and extent data
« Reply #303 on: May 27, 2016, 09:16:06 PM »

..., will there be the June drop due the melt ponds this year too, now that CT is having issues? Is it seen in the Wipneus' numbers of area?

Shadow CT will show it if the new satellite calibration is aligned by then. Home brew shows a much smaller melt pond effect.


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Rob Dekker

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Re: 2016 sea ice area and extent data
« Reply #304 on: May 28, 2016, 06:54:21 AM »
Thank you much, Wipneus, for your continued updates on area and extent.
One quick question : In your daily maps, there are signs of losses and gains in areas that clearly do not have any more ice. Like in the Baltic, St. Lawrence, [edit] the great lakes and around Sakhalin Island.

Are these artifacts of the methods used, and do they affect the area and extent estimates you report ?
« Last Edit: May 28, 2016, 08:45:59 AM by Rob Dekker »
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Wipneus

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Re: 2016 sea ice area and extent data
« Reply #305 on: May 28, 2016, 09:06:36 AM »
Thank you much, Wipneus, for your continued updates on area and extent.
One quick question : In your daily maps, there are signs of losses and gains in areas that clearly do not have any more ice. Like in the Baltic, St. Lawrence, and around [edit] Sakhalin Island.

Are these artifacts of the methods used, and do they affect the area and extent estimates you report ?

They are the consequence of the land-spill-over effect. The footprint of the microwave antenna has no sharp cut-off at the 25km gridcell boundaries and will overlap land regions. There is compensation for it, but as you see not 100% effective.

And yes they affect the area and extent numbers.

Note 1: There is always "ice" in the (great) lakes. Lake ice is never included in NSIDC extent, so that does not matter. Is IS calculated in the CT-area numbers, contributing lots of noise in the summer numbers.

Note 2: NSIDC applies ocean masks to exclude ice over regions that are guaranteed not to be covered (at the time of year) which will reduce the amount of false ice. These masks are monthly and change at the first of the month. A noticeable jump can occur at those dates, the first of June is the biggest. Wait for it, on the second we will report a century, probably double one. Since CT uses NSIDC sea ice concentration, this is also true for the first-of-the-month CT-area number yet smaller since the false ice is always low concentration.

Note 3: The NSIDC SIC data are of near-real-time quality (not to mention uncalibrated F18 satellites). After a year or so, "final" quality checked data is released (this week the final data was updated up to 2015/12/31). Some false ice will be removed in the process. Mostly not the false coastal ice, but false ice in the middle of the ocean that appears as the result of strong storms.


Andreas T

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Re: 2016 sea ice area and extent data
« Reply #306 on: May 28, 2016, 03:14:25 PM »
A while back seaice.de linked to this paper, which I was able to read in a borrowed hardcopy.
Correct, you may have a look at this one
http://www.sciencedirect.com/science/article/pii/S003442571200017X

Tying this to the observations in the posts above, it is very likely that some changes in the microwave signal as the burst of warm, moist air passed through were temporary, some persisted. What they actually represent on the ground is probably impossible to say with certainty.
edit: sorry put my own ords in the quote box!
It compares the performance of different algorithms in dealing with changes in surface conditions such as wet and crusted snow or salinity of the ice surface.
Since the measurements of microwave emission were made at ground level weather effects were not part of that research but the paper mentions that precipitation over open water is something that needs to be filtered out because it gives the impression of ice in microwave data.

It looks like you might find this paper interesting, do you have comments on it?
« Last Edit: May 28, 2016, 04:48:02 PM by Andreas T »

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #307 on: May 28, 2016, 04:24:07 PM »
Shadow CT-area report:

day  CT-date       NH               SH                Global
Fri 2016.3973  -63.8  9.713496  +71.0  8.679335    +7.2 18.392831
Sat 2016.4000  -66.6  9.646929  +27.5  8.706805   -39.1 18.353734
Sun 2016.4027 -100.9  9.546027  +83.4  8.790166   -17.5 18.336193
Mon 2016.4055  -19.3  9.526709  +37.7  8.827913   +18.4 18.354622

A relatively small drop in area overall. Regionally there are interesting differences. The CAB dropped -34k with Hudson at -19k  second. But Laptev and ESS went up by +15k and +12k.

Shadow NSIDC is now 11.2849  (-76.4k). Barents (-24k), CAB (-18k), StLawrence (-15k) and Greenland Sea (-14k) did contribute. The uptick in Hudson (+22k) contrasts with the simultaneous drop in area.

The attached delta map shows where the changes are taking place actually.



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Re: 2016 sea ice area and extent data
« Reply #308 on: May 28, 2016, 06:05:32 PM »
Looking at this image and from a completely uninformed point of view, it seems to suggest that a large portion of the Atlantic side of the CAB is moving towards the Fram.

Laurent

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Re: 2016 sea ice area and extent data
« Reply #309 on: May 28, 2016, 07:01:56 PM »
The exit to Fram doesn't seem to be too fast for the moment :
http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticicespddrf_nowcast_anim30d.gif

It is easier to see with the thickness map :
http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif

Eli81

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Re: 2016 sea ice area and extent data
« Reply #310 on: May 28, 2016, 10:19:17 PM »
The exit to Fram doesn't seem to be too fast for the moment :

It is easier to see with the thickness map :
http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif
If anything it looks almost completely stalled, especially the last week or so... It's just sitting in the straight, melting...

Is that a good thing, or a bad thing?

Laurent

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Re: 2016 sea ice area and extent data
« Reply #311 on: May 28, 2016, 11:18:40 PM »
It is normal, the Beaufort gyre is attracting the whole Arctic ice, that does happen in cycle, some release, some stall (depends of the winds also). if we want the ice to be preserved, it'd better stay there, once passed the Fram, it is chao bye bye the ice... well that was before when the Atlantic wasn't in the Arctic. Now that it is in, I think the melting is going on, we are not seeing it yet clearly at Svalbard level but it is. Let's look at it !
« Last Edit: May 28, 2016, 11:34:27 PM by Laurent »

timallard

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Re: 2016 sea ice area and extent data
« Reply #312 on: May 29, 2016, 04:05:00 PM »
It is normal, the Beaufort gyre is attracting the whole Arctic ice, that does happen in cycle, some release, some stall (depends of the winds also). if we want the ice to be preserved, it'd better stay there, once passed the Fram, it is chao bye bye the ice... well that was before when the Atlantic wasn't in the Arctic. Now that it is in, I think the melting is going on, we are not seeing it yet clearly at Svalbard level but it is. Let's look at it !
A bit off topic, the Atlantic flow circulation is abetted by having Bering Strait open.

The bathtub test: You have a hose, the Pacific is adding water and if you place the hose off center it causes a circulation. Turn off the hose, the circulation fades to nothing.

That's the analog, 1-sverdrup of current causes more inflow by the Atlantic from the circulation it causes thus to deal with the Atlantic water upwelling consider this.
-tom

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #313 on: May 29, 2016, 04:21:13 PM »
The shadow CT-area report:

day  CT-date       NH               SH                Global
Sat 2016.4000  -66.6  9.646929  +27.5  8.706805   -39.1 18.353734
Sun 2016.4027 -100.9  9.546027  +83.4  8.790166   -17.5 18.336193
Mon 2016.4055  -19.3  9.526734  +37.5  8.827632   +18.2 18.354366
Tue 2016.4082  -25.6  9.501168  -45.2  8.782450   -70.7 18.283618

Like yesterday, regions differ greatly. CAB dropped -39k while Greenland Sea (+23k) and Hudson (+13) went up.

Shadow NSIDC was 11.2665, dropping just  -18.4k. CAB (-18k) Okhotsk (-14) and Hudson (-13k) went down. Little plusses in many other regions.

Attached delta map visualizes the numbers.

BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #314 on: May 30, 2016, 10:35:17 AM »
Update for the week to May 28th

The current 5 day trailing average is on 11,338,000km2 while the 1 day extent is at 11,267,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -1,514,000km2, an increase from -1,481,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -1,021,000km2, a decrease from -1,035,000km2 last week. We're currently the lowest on record, the same as last week.



The average daily change over the last 7 days was -46.7k/day, compared to the long term average of -42.1k/day, and the 07, 11 and 12 average of -48.7k/day.
The average long term change over the next week is -55.8k/day, with the 07, 11, and 12 average being -56.0k/day.



The extent drop so far this May is the 2nd largest on record. To achieve the largest monthly loss, a drop of at least 110.0k/day is required (requiring >218k/day with with daily values), while the smallest loss requires an increase of at least 323.6k/day (>865k/day with single day values) and an average loss requires a increase of 115.3k/day (>345k/day with single day values).

I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #315 on: May 30, 2016, 04:11:49 PM »
Shadow CT-area report:

day  CT-date       NH               SH                Global
Sun 2016.4027 -100.9  9.546027  +27.5  8.706805   -73.4 18.252832
Mon 2016.4055  -19.3  9.526734  +83.4  8.790166   +64.1 18.316900
Tue 2016.4082  -25.6  9.501086  +37.5  8.827632   +11.8 18.328718
Wed 2016.4110  -70.5  9.430610  -45.2  8.782450  -115.7 18.213060

Find the strongest declines in the ESS (-30k) and  Chukchi (-16k). Greenland Sea dropped -14k.

Shadow NSIDC is now 11.2092  a drop of -56.8k. In extent Baffin (-21) and StLawrence (-14k) lead the pack.

The attached delta map shows in detail where the largest changes are.

Tor Bejnar

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Re: 2016 sea ice area and extent data
« Reply #316 on: May 30, 2016, 06:09:36 PM »
BFTV's "Melt Season 7 Day Extent Loss" graph (posted earlier today) shows that 2012 extent loss, starting in about a week, set a significant record for loss.  2012 also set a new record (for the day-of year) for about a week in August.  Interestingly, 2016, despite it being so far ahead of all other years in having the lowest extent for-the-day, has set the record fast extent loss for-the-day-of-year (since April 1) for only a few days in mid-May, and only just barely so.
Arctic ice is healthy for children and other living things.

seaicesailor

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Re: 2016 sea ice area and extent data
« Reply #317 on: May 30, 2016, 07:39:18 PM »
Update for the week to May 28th
... while the smallest loss requires an increase of at least 323.6k/day (>865k/day with single day values) ...

According to CFSv2 this is the most probable scenario

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Re: 2016 sea ice area and extent data
« Reply #318 on: May 30, 2016, 07:51:18 PM »
The extent drop so far this May is the 2nd largest on record. To achieve the largest monthly loss, a drop of at least 110.0k/day is required (requiring >218k/day with with daily values) . . .

BFTV - This new specificity regarding the 5-day averages vs. the daily values definitely helps me understand which values you are providing - thanks!

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #319 on: May 31, 2016, 04:17:27 PM »
Shadow CT-area report (based on uncalibrated F18 NSIDC sea ice concentration data):

day  CT-date       NH               SH                Global
Mon 2016.4055  -19.3  9.526734  +83.4  8.790166   +64.1 18.316900
Tue 2016.4082  -25.6  9.501086  +37.5  8.827632   +11.8 18.328718
Wed 2016.4110  -70.0  9.431054  -45.2  8.782425  -115.2 18.213479
Thu 2016.4137  -77.4  9.353630  +90.8  8.873200   +13.4 18.226830

That would have been a century if the CT alculation did not in clude ice on the lakes as "sea ice", lake ice went up by +24k. Laptev suddenly got active (-32k), followed by Kara (-18k), Baffin (-17k), Greenland Sea (-13k) and Chukchi (-12k). ESS bumped +15k.

Shadow NSIDC is now at 11.1573  (-51.9k). No regions are noteworthy. No lake ice in the NSIDC index fortunately.

The attached delta map shows the details.

BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #320 on: May 31, 2016, 04:31:31 PM »
With the 5 day trailing average, the latest value is now 1.224 million km2 below 2012. This is the largest gap to 2012 this year.
However, we're approaching the June 2012 cliff where it dropped over 2 million in 20 days, so it's unlikely that we'll still be more than 1 million below 2012 by the end of the first week of June.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Jim Pettit

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Re: 2016 sea ice area and extent data
« Reply #321 on: June 01, 2016, 03:58:10 PM »

CT Area:
9,353,630 km2 (01 June [Day 0.4137])
Down 3,567,728 km2 (27.61%) from 2016 maximum of 12,921,358 km2 on 29 March [Day 0.2384].
7,119,621 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Down 77,424 km2 (-.82%) from previous day.
Down 423,676 km2 (-4.36%) over past seven days (daily average: -60,525 km2).
Down 77,424 km2 (-.7%) for June (daily average: -77,424 km2).
1,056,625 km2 below 2000s average for this date.
678,820 km2 below 2010s average for this date.
687,360 km2 below 2015 value for this date.
586,594 km2 below 2012 value for this date.
Lowest value for the date.
NOTE: due to the prolonged absence of official CT sea ice area data, I'm instead using Wipneus' calculated area numbers in places. The official numbers will be inserted if/when available. In the meantime, thanks, Wipneus!

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #322 on: June 01, 2016, 04:23:20 PM »
Shadow CT-area report (based on uncalibrated F18 NSIDC sea ice concentration data):

day  CT-date       NH               SH                Global
Tue 2016.4082  -25.6  9.501086  -45.2  8.782425   -70.9 18.283511
Wed 2016.4110  -70.0  9.431054  +90.9  8.873280   +20.8 18.304334
Thu 2016.4137  -76.8  9.354228 +137.7  9.010970   +60.9 18.365198
Fri 2016.4164  -31.8  9.322383 +187.7  9.198683  +155.9 18.521066

While the CAB had a big "recovery" of +38k, Laptev dropped almost as much -36k. Further only Kara can be noted at -14k.

Shadow NSIDC extent is now 11.0969  dropping -60.4k. Baffin, Kara and okhotsk are the biggest contributors: -22k, -18k and -15k. Greenland Sea went up by +22k.

Tomorrow I expect to report the first of the month numbers, in June this guarantees big drops as lots of false ice will be masked out. Looking at the numbers I expect 80-150k of extra extent loss.

The attached delta map shows the details.

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Re: 2016 sea ice area and extent data
« Reply #323 on: June 01, 2016, 09:25:34 PM »
Tomorrow I expect to report the first of the month numbers, in June this guarantees big drops as lots of false ice will be masked out. Looking at the numbers I expect 80-150k of extra extent loss.

I assume the extra 80-150k all comes in the June 1 number, or is it phased in?

BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #324 on: June 01, 2016, 09:47:48 PM »
The average daily drop from May 31st to June 1st is 138k. These range from small 24k drop in 1987 to a max drop of 244k in 1990.
Only one drop in the last 27 years was small enough to prevent 2016 from being below 11 million km2 on June 1st.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

abbottisgone

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Re: 2016 sea ice area and extent data
« Reply #325 on: June 02, 2016, 07:52:22 AM »
The average daily drop from May 31st to June 1st is 138k. These range from small 24k drop in 1987 to a max drop of 244k in 1990.
Only one drop in the last 27 years was small enough to prevent 2016 from being below 11 million km2 on June 1st.
I think the number given in espens thread for june 1 was very low: sub 30k.

The preceding few days were circa 50k so I suppose this is almost typical pause-like behaviour which seems to be normal at this exact time as seen by my grossly amatuer involvement thus far!
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Wipneus

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Re: 2016 sea ice area and extent data
« Reply #326 on: June 02, 2016, 08:41:08 AM »

I think the number given in espens thread for june 1 was very low: sub 30k.

The preceding few days were circa 50k so I suppose this is almost typical pause-like behaviour which seems to be normal at this exact time as seen by my grossly amatuer involvement thus far!

It is probably nothing to do with the ice. On 1st of June Jaxa changes the tie points of the Bootstrap algorithm from "dry ice" to "wet ice" (some wrongly interpret this as melt pond compensation).
The change takes a few days, so expect some more slow days.

You can observe this on my AMSR2 extent graph.  Until today, Jaxa and UH (black and purple lines) follow each other closely. Between 1 June and 15 October expect Jaxa extent to stay above Uni Hamburg extent.

Edit: To be extra clear, this is an ADS-Jaxa SIC thing, no such effect in data from other sources.



LINK
« Last Edit: June 02, 2016, 08:50:15 AM by Wipneus »

Jim Pettit

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Re: 2016 sea ice area and extent data
« Reply #327 on: June 02, 2016, 02:03:56 PM »
ADS-NIPR Extent:
10,405,086 km2 (01 June)
Down 3,537,421 km2 (25.37%) from 2016 maximum of 13,942,507 km2 on 29 February.
7,227,631 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Down 21,958 km2 (-.21%) from previous day.
Down 299,867 km2  (-2.8%) over past seven days (daily average: -42,838 km2).
Down 21,958 km2  (-.18%) for June (daily average: -21,958 km2).
1,218,364 km2 below 2000s average for this date.
717,414 km2 below 2010s average for this date.
440,699 km2 below 2015 value for this date.
1,038,112 km2 below 2012 value for this date.
Lowest year-to-date (01 January - 01 June) average.
Lowest value for the date.
98 days this year (64.47% year-to-date) have recorded the lowest daily extent.
27 days (17.76%) have recorded the second lowest.
14 days (9.21%) have recorded the third lowest.
139 days in total (91.45%) have been among the lowest three on record.


CT Area:
9,322,383 km2 (02 June [Day 0.4164])
Down 3,598,975 km2 (27.85%) from 2016 maximum of 12,921,358 km2 on 29 March [Day 0.2384].
7,088,374 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Down 31,845 km2 (-.34%) from previous day.
Down 391,113 km2 (-4.05%) over past seven days (daily average: -55,873 km2).
Down 108,671 km2 (-.98%) for June (daily average: -54,335 km2).
1,032,736 km2 below 2000s average for this date.
643,823 km2 below 2010s average for this date.
750,309 km2 below 2015 value for this date.
556,003 km2 below 2012 value for this date.
Lowest value for the date.
* - NOTE: due to the prolonged absence of official CT sea ice area data, I've incorporated Wipneus' area numbers as calculated from NSIDC data. The official numbers will be inserted if/when available. In the meantime, thanks, Wipneus!




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Re: 2016 sea ice area and extent data
« Reply #328 on: June 02, 2016, 05:02:55 PM »
Shadow CT-area report (based on uncalibrated F18 NSIDC sea ice concentration data):

day  CT-date       NH               SH                Global
Wed 2016.4110  -70.0  9.431054  +90.9  8.873280   +20.8 18.304334
Thu 2016.4137  -76.8  9.354228 +137.7  9.010970   +60.9 18.365198
Fri 2016.4164  -32.1  9.322127 +187.9  9.198832  +155.8 18.520959
Sat 2016.4192  -21.9  9.300189 +160.8  9.359640  +138.9 18.659829

Increases in Laptev(+18k) and Baffin (+15). Area dropped in St-Lawrence (-11) and in regions not one of the 14 well known ones (-20k).

Shadow NSIDC extent is 10.9977  (-98.2k) . Here the drops in St-Lawrence and Other Regions are much bigger: -32k and -40k.

As explained yesterday, those drops are caused by the first of the month effect. Without it we would have had a very small decrease in extent an perhaps a positive change in area.

The attached delta map shows the details.

Tor Bejnar

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Re: 2016 sea ice area and extent data
« Reply #329 on: June 02, 2016, 08:28:49 PM »
"those drops are caused by the first of the month effect."
How can there be any blue on the Great Lakes - that is, ice growth between May 31 and June 1 if a mask now prevents false ice showing up there.  Just to make sure - there is no ice on the Great Lakes now, right?  (I know there was some ice on Lake Superior until June 5 or 6, 2014.)
Arctic ice is healthy for children and other living things.

LRC1962

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Re: 2016 sea ice area and extent data
« Reply #330 on: June 02, 2016, 08:39:50 PM »
Based on this:
Do not think possible. Highly unlikely for some time.
Edit: Based on animation: http://www.glerl.noaa.gov/res/glcfs/anim.php?lake=l&param=glsea&type=n
May the 4th was last day of ice.
« Last Edit: June 02, 2016, 08:51:13 PM by LRC1962 »
"All truth passes through three stages: First, it is ridiculed; Second,  it is violently opposed; and Third, it is accepted as self-evident."
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Magma.

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Re: 2016 sea ice area and extent data
« Reply #331 on: June 02, 2016, 09:53:40 PM »
"those drops are caused by the first of the month effect."
How can there be any blue on the Great Lakes - that is, ice growth between May 31 and June 1 if a mask now prevents false ice showing up there.  Just to make sure - there is no ice on the Great Lakes now, right?  (I know there was some ice on Lake Superior until June 5 or 6, 2014.)

According to regional charts, the last scraps of ice in sheltered bays on the central north Canadian side of Lake Superior melted out just after May 6.

BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #332 on: June 02, 2016, 10:46:32 PM »
Despite what was only the 3rd sub 100k drop for June 1st since 1990, NSIDC daily extent is now below 11 million km2. This is 10 days earlier than the previous record holders 2012 and 2010, which both reached dropped below 11 million km2 on June 11th.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

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Re: 2016 sea ice area and extent data
« Reply #333 on: June 03, 2016, 01:27:19 AM »
"those drops are caused by the first of the month effect."
How can there be any blue on the Great Lakes - that is, ice growth between May 31 and June 1 if a mask now prevents false ice showing up there.  Just to make sure - there is no ice on the Great Lakes now, right?  (I know there was some ice on Lake Superior until June 5 or 6, 2014.)

Yazzur

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Re: 2016 sea ice area and extent data
« Reply #334 on: June 03, 2016, 01:32:22 AM »
There is no ice on the Great Lakes as of last weekend, and it is well above freezing.
« Last Edit: June 03, 2016, 02:04:03 AM by Yazzur »

ktonine

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Re: 2016 sea ice area and extent data
« Reply #335 on: June 03, 2016, 03:43:19 AM »
A few years back I investigated some of the coastal anomalies in SIE -- patches of ice where there hadn't been any for days or weeks that just popped up out of nowhere for no apparent reason.

Checking many of these with MODIS I found that many of them were sandy coastal stretches.  I think sunlight on wet sand was confusing the sensors.  Not sure if a similar effect is happening on the Great Lakes, but regardless, sensors aren't perfect and there are numerous conditions that might give very similar reflections.  It's one of the reasons why SIE has such a large uncertainty.  It's nothing more than a curiosity.

ghoti

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Re: 2016 sea ice area and extent data
« Reply #336 on: June 03, 2016, 03:53:39 AM »
Great Lakes really should be masked out because it is absurd to even consider the possibility of ice in the spring/summer/fall now.

Look at the lake temperatures...

http://www.mlive.com/weather/index.ssf/2016/05/all_great_lakes_warmer_than_la.html


S.Pansa

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Re: 2016 sea ice area and extent data
« Reply #337 on: June 03, 2016, 07:02:40 AM »
Ad great lakes. I don't think that they are included, at least not in the NSIDC numbers. To quote Wipneus himself from last years thread:
Quote
A repeat seems in order about lake ice.

CT-area and NSIDC extent are based on the same data, available as NSIDC gridded sea ice concentration data.

NSIDC does not include in its calculation ice detected in lakes, so there is no need to filter that says "No lake ice in July". In the ocean it _is_ filtered, so there will be "No ice in St. Lawrence" for example.

CT-area does include lake ice and also does not filter anything unless NSIDC has filtered it already.

This is only one of the deficiencies (my judgement) of the CT-area figures. But is a popular measure so I add some additional information about it. That is report it timely, summarize the regional deviations and note obvious "false" changes, like (dis)appearance of "lake ice".

By the way: Thanks Wipneus for all the infos you provide day by day! Much aprecciated.

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #338 on: June 03, 2016, 07:46:40 AM »
Thank you, S.Pansa, your post saves me repeating myself again.

Just this:

- There are ocean masks, that do not mask lakes because (I think) lakes are not oceans; There are 12 ocean masks, one for each month;
- There is a lake mask, NSIDC pays attention, CT does not. There is only one for the whole year;
- The NSIDC ocean masks are used by other sources of sea ice concentration. Uni Hamburgs ice concentration and from OSI-SAF are known to me. Impact on UH area and extent (home brew thread) is small, as there is far less false ice due to the higher resolution of the used satellite microwave measurements.

Tor Bejnar

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Re: 2016 sea ice area and extent data
« Reply #339 on: June 03, 2016, 05:19:05 PM »
Thanks.  Is the following correct?
NSIDC: always a lake mask (regardless of what the blue/red change maps show)  Seashore masks change each month (but you don't know what they are by looking at the blue/red change maps)
CT: never a lake or sea mask (therefore responsive to data that shows up on the blue/red change maps)
Arctic ice is healthy for children and other living things.

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #340 on: June 03, 2016, 05:57:39 PM »
Thanks.  Is the following correct?
NSIDC: always a lake mask (regardless of what the blue/red change maps show)  Seashore masks change each month (but you don't know what they are by looking at the blue/red change maps)
CT: never a lake or sea mask (therefore responsive to data that shows up on the blue/red change maps)

"seashore maks" are called ocean masks. The effect they have is not just on the coastal ice but also on the open ocean (e.g. due to high waves from storms). They are applied to the gridded sea ice concentration data before they are distributed. So all users of that data used the masked values, including CT.

NSIDC did choose not to mask out any lake ice in their gridded sea ice concentration product. So it depends on the user of the data to do with the "lake ice". There is a mask though that says, this is land or ocean or lake. That can be used to include only grid cells that cover ocean. CT did choose to use grid cells that cover ocean or lake. 


Wipneus

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Re: 2016 sea ice area and extent data
« Reply #341 on: June 03, 2016, 06:06:57 PM »
No new data from NSIDC yet. What they have done is to remove the F18_uncalibrated directory and mixed the F18 data files in the normal place with F17 files (upto 2016/03/31).
So I hope that calibration is soon a fact.

Not bad. I updated my computer with new processor, mother board and memory today. Bad thing is that my high resolution screen (2048x1152) is not recognized and I have to work on a far too small thing. Software install is another thing, that may take days before everything is OK again.

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #342 on: June 03, 2016, 07:00:50 PM »
NSIDC gridded SIC data is in.
Shadow CT-area report (based on F18 NSIDC sea ice concentration data, we don't know if it is calibrated):

day  CT-date       NH               SH                Global
Thu 2016.4137  -76.8  9.354228 +137.7  9.010970   +60.9 18.365198
Fri 2016.4164  -32.1  9.322127 +187.9  9.198832  +155.8 18.520959
Sat 2016.4192  -22.0  9.300101 +160.8  9.359640  +138.8 18.659741
Sun 2016.4219 -156.7  9.143387 +100.4  9.460078   -56.3 18.603465

One century and a half, big drops in CAB (-62k), Laptev (-39k), Baffin (-17k) and ESS (-16k). 

Shadow NSIDC extent is now 10.9823  (-15.4k). Baffin did a big drop of -44k, and had some help from Laptev (-16k). Spoilers are CAB (+26k) and Barents (+16k).

The delta map is rather spectacular today.

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Re: 2016 sea ice area and extent data
« Reply #343 on: June 04, 2016, 07:08:44 AM »
Wipneus,
Is the F18 data available for last year?
if so you could get a feel for how accurate is by running last years data through your algorithm, and comparing the the F17 data previously used.

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Re: 2016 sea ice area and extent data
« Reply #344 on: June 04, 2016, 08:45:05 AM »
Wipneus,
Is the F18 data available for last year?
if so you could get a feel for how accurate is by running last years data through your algorithm, and comparing the the F17 data previously used.

No. The only dates for which I have parallel measurements are from 1st of April to the beginning of May. During most of that time the F17 was broken. IIRC during 1-4 April the F17 was still OK, that data could be checked.

ktonine

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Re: 2016 sea ice area and extent data
« Reply #345 on: June 04, 2016, 02:27:55 PM »
Wipneus,
Is the F18 data available for last year?
No. The only dates for which I have parallel measurements are from 1st of April to the beginning of

You could ask Robert Grumbine over on his blog -- More Grumbine Science -- if it's available.  He has to work with the data as part of his day job.

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Re: 2016 sea ice area and extent data
« Reply #346 on: June 04, 2016, 04:16:50 PM »
Shadow CT-area report (based on F18 NSIDC sea ice concentration data, we don't know if it is calibrated):

day  CT-date       NH               SH                Global
Fri 2016.4164  -32.1  9.322127 +187.9  9.198832  +155.8 18.520959
Sat 2016.4192  -22.0  9.300101 +160.8  9.359640  +138.8 18.659741
Sun 2016.4219 -156.5  9.143601 +100.7  9.460318   -55.8 18.603919
Mon 2016.4247  -97.3  9.046261 +199.7  9.660023  +102.4 18.706284

The near century show another big drop in the ESS (-46k), with Hudson (-19k),  CAA (-25k), Baffin and Kara (both -12k).

Shadow NSIDC extent 10.9997, up by  +17.4k. Very mixed results, Hudson, Greenland Sea, Barents and Bering went up. Okhotsk, Baffin and Kara lost extent.

The attached delta map shows the concentration drop in ESS, CAA and CAB, and increase in Laptev and (elsewhere) in the CAB.

Jim Pettit

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Re: 2016 sea ice area and extent data
« Reply #347 on: June 05, 2016, 04:25:07 PM »
ADS-NIPR Extent:
10,354,257 km2 (04 June)
Down 3,588,250 km2 (25.74%) from 2016 maximum of 13,942,507 km2 on 29 February.
7,176,802 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Up 3,537 km2 (.03%) from previous day.
Down 223,174 km2  (-2.11%) over past seven days (daily average: -31,882 km2).
Down 72,787 km2  (-.59%) for June (daily average: -18,197 km2).
1,129,707 km2 below 2000s average for this date.
646,031 km2 below 2010s average for this date.
334,711 km2 below 2015 value for this date.
998,455 km2 below 2012 value for this date.
Lowest year-to-date (01 January - 04 June) average.
Lowest June to-date average.
Lowest value for the date.
101 days this year (65.16% year-to-date) have recorded the lowest daily extent.
27 days (17.42%) have recorded the second lowest.
14 days (9.03%) have recorded the third lowest.
142 days in total (91.61%) have been among the lowest three on record.


CT Area:
9,046,261 km2 (05 June [Day 0.4247])
Down 3,875,097 km2 (29.99%) from 2016 maximum of 12,921,358 km2 on 29 March [Day 0.2384].
6,812,252 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Down 97,340 km2 (-1.06%) from previous day.
Down 480,473 km2 (-5.06%) over past seven days (daily average: -68,639 km2).
Down 384,793 km2 (-3.45%) for June (daily average: -76,959 km2).
1,044,391 km2 below 2000s average for this date.
644,823 km2 below 2010s average for this date.
765,090 km2 below 2015 value for this date.
709,884 km2 below 2012 value for this date.
Lowest value for the date.
* - NOTE: due to the prolonged absence of official CT sea ice area data, I've incorporated Wipneus' area numbers as calculated from NSIDC data. The official numbers will be inserted if/when available. In the meantime, thanks, Wipneus!



Wipneus

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Re: 2016 sea ice area and extent data
« Reply #348 on: June 05, 2016, 04:40:13 PM »
Shadow CT-area report (based on F18 NSIDC sea ice concentration data, we don't know if it is calibrated):

day  CT-date       NH               SH                Global
Sat 2016.4192  -22.0  9.300101 +160.8  9.359640  +138.8 18.659741
Sun 2016.4219 -156.5  9.143601 +100.7  9.460318   -55.8 18.603919
Mon 2016.4247  -97.3  9.046325 +199.8  9.660105  +102.5 18.706430
Tue 2016.4274  -71.5  8.974781  +51.3  9.711412   -20.2 18.686193

A rather large total extent drop, but the regional ones are huge! The ESS dropped now -78k while the CAB's restoration countered by +57k. Baffin, Beaufort and Lakes are much more modest, each about -11k.

Shadow NSIDC extent was 10.9802 ( -19.5k). Here Hudson (+25k) and Chukchi (+20k), went up, where Okhotsk (-17k) , Baffin (-16k ) and Barents (-13k)  came down in extent.

In the attached delta map there is still the patterns over Chukchi/ESS/Laptev and CAB. In the CAA the serious melt in the south can be seen (where in the north the concentration restored).

Jim Pettit

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Re: 2016 sea ice area and extent data
« Reply #349 on: June 05, 2016, 05:14:09 PM »
Shadow CT-area report (based on F18 NSIDC sea ice concentration data, we don't know if it is calibrated):

day  CT-date       NH               SH                Global
Sat 2016.4192  -22.0  9.300101 +160.8  9.359640  +138.8 18.659741
Sun 2016.4219 -156.5  9.143601 +100.7  9.460318   -55.8 18.603919
Mon 2016.4247  -97.3  9.046325 +199.8  9.660105  +102.5 18.706430
Tue 2016.4274  -71.5  8.974781  +51.3  9.711412   -20.2 18.686193

Thanks. That's now the earliest SIA has been below 9 million km2. But by just five days; I predict that 2016's area will drop (rise?) to second place behind 2012 within the next two weeks (say, June 20).