UPDATE: Dr. Walt Meier of NSIDC writes in with some information, seethe end of the article.
I’m getting weary of answering this question in comments, so here it is front page. Note the little bump right about June 1st.
Rick W asks:
Can anyone explain the upward bump in the sea ice extent that seems to occur each June? Apologies if previously covered.
Answer:
This is a seasonal adjustment to compensate for meltwater on top of the ice, which would ordinarily be viewed as “open water”. Right about now, the Arctic sea ice gets melt pools forming on the surface. If these are not compensated for, sea ice extent will read artificially low.
That being said, I wonder why we don’t see the same adjustment at NSIDC:
I don’t know the answer, but it could be in the difference between SSMI and AMSR-E satellite sensors (NSIDC uses SSMI, JAXA uses AMSR-E).
We also don’t see an adjustment at Cryosphere Today, and they also use SSMI:
Nor does NANSEN:
Click for larger images
If anyone knows why JAXA does the adjustment but the others do not, I’m all ears. My theory is that it is sensor related, but we should find out for sure. I’m swamped today, so I’ll leave this puzzle for WUWT readers to solve.
UPDATE
Dr. Walt Meir writes in with this:
Since you mentioned it on your blog, I can fill in at least some info:
You are correct. When the melt season kicks in the surface water changes
the contrast between ice and water. To more accurately measure the
area/extent, you should adjust coefficients to account for this.
This is done for SSM/I. However, because the SSM/I algorithm is
different from the AMSR-E algorithm (and other differences between the
sensors) the adjustment is different. In SSM/I, the adjustment is
smoother and thus there isn’t that “bump”.
You have to remember that AMSR-E is a research sensor and the algorithms
are still being refined. That is one reason we don’t use AMSR-E for the
long-term timeseries (though the more important reason is the
inconsistency between the two sensors and algorithms).
– Walt
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Shawn Whelan (16:11:44) :
Henry Larsen travelled from Halifax to Vancouver in 86 days in 1944 through the Northern route of the NW Passage. Likely impossible this year.
Well that’s an assumption by you Shawn, I think I’ll wait until Aug/Sept to be sure. This year already it’s open from the Atlantic to Resolute with on small tricky patch, and the polynya off Banks is shaping up fairly well.
Which means after 60 plus years of AGW there is more ice in the Arctic now than in 1944.
Even if your prediction held up the logic doesn’t, you’re only focussing on a very small region of the Arctic, for example the St Roche had to struggle past the ice along the Alaskan shore to make the Bering St by Sept 27th 1944. Check out the sea ice last year on Sept 26th, see any of that near-shore ice then?
http://iup.physik.uni-bremen.de:8084/amsredata/asi_daygrid_swath/l1a/n6250/2008/sep/asi-n6250-20080926-v5_nic.png
As you can see on that image the NW Passage was open and 7 yachts sailed through last year, Berrimilla for example left Nome on 24th July and reached Nuuk, Greenland on 27th August, less than half the time the St Roche took.
Tom in Texas (19:11:14) :
RoyFOMR, my sister’s name is Sandra – guess what her nickname is.
Tom, If I guessed Sandra’s nickname she wouldn’t be happy – Am I sooo transparent- she may say!!!!
If, I didn’t guess correctly, would I be accused of ‘not understanding her’
Oh dear, I’m gonna get slaughtered – One day, Tom I’ll learn that the first step of Wisdom begins with the knowledge that although stitching one’s mouth up may be painfull, it’z a breeze when compared to the life-equivalent of responding to the question – does my bum look big in this- with a yes!!
How seriously should we view perturbations in this plot when 16 mil sq km of fractured ice could have the same area as 2.4 mil sq km of solid ice? That’s if I understand the min 15% rule correctly.
DaveE (16:50:31) :
RoyFOMR (16:29:24) :
Not to mention that Amundsun SAILED the NW passage in either 1903 or 05.
Actually both (they didn’t actually sail in 1904 just stayed in Gjoahavn).
It is neither the itch nor the scratch nor even the sashay but the flounce.
As for Arctic ice it cometh and goeth from time to time as it pleases for reasons we wot not of.
As I have said before on this board please wake me up when you find the pot of gold at the end of the rainbow at the north pole.
Kindest Regards
Bill Illis (17:25:14) :
I see what you mean. It’s so small it’s invisible and so early it never arrives.
http://i599.photobucket.com/albums/tt74/MartinGAtkins/Hamburg2.jpg
Thanks for the post Anthony. This is the best blog—not just ‘best science’ blog’—on the internet!! I’m readying my finger to click a vote for WUWT for best science blog 2009!
I’m still betting on fire to destroy Earth but as R. Frost knew either will do.
Some say the world will end in Eccentricity
Some say in Obliquity
But many in my generation
Tend to favor Inclination
So we are left to wonder when
Until our earth returns through dust
And will again
As so it must
jeez (18:58:18) :
Off topic, but I have an itch.
Thanks for the news flash. I’m sure Anthony is making a post for it.
I’ll be paying attention to the ice between Barrow, Alaska and the Laptev Sea. How about you?
itch ok
stupid not ok
Gotcha
Reply: I didn’t clean it up. I approved the whole mess. I suspect Anthony ~ charles the moderator
OT … or not OT? That is the question…
More from Ian Plimer. I ask the non-skeptics, global warm-mongers, whatever you want to call yourselves, to watch all of this talk. This is the first of 5 You Tube videos.
Somebody should mention ice thickness…
In 2007 it was anomalous weather that set the low ice extent record. But this had been made possible by previous years of thinning.
“In terms of total sea ice mass, the old and thick perennial (multi-year) ice dominated the younger and thinner seasonal (one-year) ice that melted away in the summer. Most notably, perennial ice is more likely to survive the summer melt season.”
“In view of Arctic sea ice mass balance, the distribution of perennial and seasonal sea ice in March is particularly important. Sea ice distribution in March represents the transitional condition from winter to spring as the solar heat flux starts to increase and the melt process commences and continues into summer. Besides differences in ice thickness, these major ice classes partition solar energy differently, with the perennial ice having a larger albedo and also transmitting less solar radiation to the ocean. The shift from perennial to seasonal ice thus impacts the ice mass balance and the ice-albedo feedback mechanism.” 2007
2008 was the year of the lowest summer Arctic sea ice volume.
So what?
Kindest Regards
Let’s be fair. Volume is not irrelevant.
But let us also consider that volume can be hard to measure, as has been demonstrated by a recent flyover indicating that first-year ice was around twice as thick as calculated.
Furthermore, ice area is more important than ice volume because ice area, not volume, is what determines albedo.
Certainly OT, but there’s no recent post on global temperatures, so: the GISS anomaly for May 2009 is out. 0.55, which is nothing but the highest anomaly this year and the third highest anomaly for May in their database.
This is consistent with the fact that most of the warming in May was observed at the poles – which are not covered by satellites (UAH, RMSS) that accordingly show relatively small positive anomalies.
Lots of interesting comments. So:
DMSP (SSMI) – rude & crude; counts water, the rest is ice {NSIDC/Cryospher/NANSEN}.
Aqua (AMSR-E) – elegant & sophisticated; counts ice and is so sensitive, surface water masks the ice during summer months, so they adjust.
Bottom line:
We’ll see this year’s ranking come the first week in September. Until then, it’s like halftime and that score doesn’t count. My personal and totally unscientific guesstimate is there will be more ice this year than last. And probably more volume.
And in a couple months, when a new reader asks about that funny bump in June, we can all refer him to this posting and all its comments and enlightenment offered.
Francis (21:32:47) :
2008 was the year of the lowest summer Arctic sea ice volume.
————————–
Link to the data please ??
evanmjones (22:34:43) :
When Arctic Ocean ice is least so is the sun angle. Reflection off water is greater and absorption less than when the sun is higher. This is followed by no sun over much of the region for many weeks. Ice acts as an insulator when it is there and when it is not the water more easily gives up energy and freezes again.
Maybe you could collect the information and run the numbers and tell me how this all works out averaged over 30 years. I’ll have another beer while I await your post. Thanks, John
Re: Michael Jennings (12:02:48)
/// Just for the record, AndyW35 is a troll who also tries to stir up trouble on ClimateAudit and is not the LEAST bit interested in the truth, except for his version of course.///
It is quite interesting that you consider that anybody who points out facts is a troll, whereas all the far more puerile comments and those who need to use cherry picked data like ‘eleven years cooling’ on here are not.
evanmjones (22:34:43) :
Furthermore, ice area is more important than ice volume because ice area, not volume, is what determines albedo.
———————-
With respect Evan, it’s ice volume that is important in the debate which was, purportedly, already over. If sea ice area is a proxy for warming at the poles then, as of around today, there has been no warming at the poles combined since 1979. This is one or two clicks away at Cryosphere Today for any intelligent person, moron, politician or AGWer even.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg
So, in pseudoscienceland, the pseudoelephant in the pseudoroom is ice volume. No one knows what it is exactly (amazingly, given the importance) but, if it tracked with sea ice area imagine the cognitive dissonance induced by data showing clearly that the poles are not warming to the “poles-are-warming” set.
Catlin crew to the rescue. It’s definitely thinner, robust measurements, fits with IPCC models. Ice volume is lower, poles are warming, debate over.
Zzzzzzzzzzz
I am baffled! After all these years people are still trying
to control the climate by adjusting the data. (?)
Certainly OT, but there’s no recent post on global temperatures, so: the GISS anomaly for May 2009 is out. 0.55, which is nothing but the highest anomaly this year and the third highest anomaly for May in their database.
This is consistent with the fact that most of the warming in May was observed at the poles – which are not covered by satellites (UAH, RMSS) that accordingly show relatively small positive anomalies.
But surely there is no warming whatever observed at the the North Pole. In fact, nothing at all is observed at the North Pole. GISS guesstimates their North Polar average mostly from the infamous Siberian Thought Criminals, the Abominable Snowmen, compromised by poor siting and serious UHI.
I cannot speak for the South Pole. There is one station there, but most stations are located on the strongly warming peninsula. If they are gridding their results in a manner reminiscent of Steig, however, their results would be in serious question.
And since the poles are around 5% of the earth’s surface, they would have to be roughly 8 to 9C warmer than average to produce an upward bump of from 0.45 to 0.5C. That’s quite a lot, even for polar regions.
I am baffled! After all these years people are still trying
to control the climate by adjusting the data. (?)
Stick with what works.
those who need to use cherry picked data like ‘eleven years cooling’ on here are not.
I do not regard the 11-year view as a cherrypick: One must include both the 1998 El Nino and the 1999-2000 La Nina that immediately followed, or exclude both. 1999, for example, would be a serious cherrypick.
When one is assessing a warming trend, it makes sense to start the assessment when the warming begins to the point where it ends.
Therefore, I do not object to a 1977 – 1998 view (which shows strong warming). But likewise, when one is examining a cooling trend, it is not “unfair” to begin at the point when the cooling begins.
Ph-in-CA: Irony noted.