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Kevin McKinney

Well, it's not boring, now, is it?

One constant has remained during all these up and downs of melt rates, though, and that is the prevalence of comparatively low ice concentrations. Cryosat will add a lot of clarity on that score, I think. I hope that summaries of that data will be available to the public on a timely basis as things get organized.

Neven

Yeah, I was wondering about this too. Who is going to inform us? NASA? NSIDC? Or only through science papers that I will not understand?

I want daily updated graphs!

Neven

There are a couple of high pressure areas in the central Arctic according to the Cologne weather maps at the moment. If I'm interpreting the ECMWF forecast map correctly we can expect a weak positive ADA the coming 5 days with some heavy lows forming over the Siberian Seas. This might mean century breaks, also because CT sea ice area anomaly has dropped again today.

Lord Soth

If we get back the arctic Dipole anomally, and it stays back for the month of August, we still stand a good chance to beat the 2007 record. If it does this off again on again thing, then we are never going to see the compaction of the pack.

From my calculations based on PIOMAS we are close to being in a tie here in late July with the 2007 september minimun sea ice volume (yes volume; not extent)

A good component of the September 2007 minimun was compression of the ice mass, due to the winds constantly blowing from the south all summer due to the seasonal persistant Dipole anomally.

August could be an interesting month.

Artful Dodger

Ice is not lost by compaction; it is preserved. Compaction is how multi-year ice is created, when stacked up ice is able to survive the annual melt.

Any forces that tend to spread the multi-year pack ice also increase it's loss. It is the spreading, thinning, and fragmentation of the pack that will finally destroy it. Measuring ice loss based on Extend is misleading until the very end, as we saw last week in Siberia. The pack weakens, spreads, mixes with larger volumes of liquid sea water, then melts.

For years scientists predicted the Canadian Archipelago would be the last bastion of the Arctic Ice Cap. We saw this Spring that thick landfast ice come unglued, and move with the Beaufort Gyre into the Central Basin. Watch the Central Basin, everything else is a sideshow.

Notice in the NSIDC graph from April 2010 how the multi-year ice that survived 2009 has moved with the Gyre into the Beaufort and Chukchi seas. This is the ice now being steadily eaten away in this year's melt, since most of the first year ice has already melted. When the last of the multi-year ice is gone, it's all over. No recovery.

http://nsidc.org/images/arcticseaicenews/20100406_Figure6.png

Kevin McKinney

Yes, that is one of the striking things in the concentration map--how the central Archipelago has--I'm struggling for the right verb here--thinned? Opened up? Deteriorated?

Some of the highest concentrations are in the southern portion, and it's hard (for me at least) to imagine that they will survive this season all that well.

Neven

Reported melt of 72,657 square km, an improvement over yesterday, but the revisions have been big lately. We might get a bigger melt reported tomorrow. Off to bed now.

Artful Dodger

Kevin said: "--I'm struggling for the right verb here--thinned? Opened up? Deteriorated?"

Barber-ed?

Steve Bloom

Ha! :)

Anu

I like to download some of these graphs and zoom in on sections of interest:
http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Area.png

It seems like every single year is parallel from now until about the third or fourth day in August (a few minor wiggles, yes).

Then we see the curves diverge and determine their ultimate minimums, for instance, 2006 veering sharply into a shallow minimum, 2009 veering off to a deeper minimum, then 2005 veering off, then 2002, 2004 and 2003.

2008 and 2007 kept up their parallel declines until about the third week in August, and 2007 started to bottom out earlier, but had started from a lower position than 2008.

I don't know why this stretch of time has been so consistent for Arctic sea ice area decline, but it might mean 2010 continues on its present path until at least August 3rd, regardless of how "extent" is playing out with winds and currents.
This would bring it close to the level of 2005 minimum area, and not much above 2009.
In early August.

Just an observation...

Artful Dodger

Nature.com news: Arctic Ocean full up with carbon dioxide

"Loss of sea ice is unlikely to enable Arctic waters to mop up more carbon dioxide from the atmosphere.

... research published in Science today suggests that part of the Arctic Ocean has already mopped up so much CO2 that it could have almost reached its limit."

dorlomin

Kevin said: "--I'm struggling for the right verb here--thinned? Opened up? Deteriorated?"

Barber-ed?
=============
Ungoddarded?

Artful Dodger

Un-Roald !

Lord Soth

When I was mentioning compaction in 2007, it was mostly an end game event. After all things mentioned that encourage melt all summer, the ice was very thin and rotten in the arctic pack. I remember one ice breaker crusing at 7 knots near the north pole in rotten ice. It could have been the PolarStern.

Towards the end of the 2007 melt season, the trend was towards compression of the ice. If this did not happen, the 2007 ice melt would have been in the high 4's.

Phil263

I don't know whether you are familiar with this graph from the Danish Centre for Ocean & ice:
http://ocean.dmi.dk/arctic/icecover.uk.php

It shows the SI extent for 30% concentration. As you can see the line in this case has already sharply veered off to the right and it seems that it has crossed 2009 and about to cross 2008. I wonder if this is sign of things to come for the Jaxa gauge since we are looking at 30% concentration?

Kevin McKinney

In the Great Verb Contest I seem to have inadvertently launched, I suppose we could have tweaked the original response a bit, and gone with "trimmed"--that would have made us work for that sly Barber connection.

I don't think that the 30% dmi graph necessarily has prognosticative value (now I seem to be playing with adjectives!) That's because what the disjunction shows is that trends at different concentration levels can be uncoupled from one another. It doesn't show which one "leads," or even that one necessarily does lead.

Or so it seems to me.

Lord Soth

Or say it with statistics.

There is very little linear dependence (correlation) between the DMI 30% extent and the IJIS 15% extent

or if you want a terse qualitative assessment:

In regard to the DMI and IJIS plots, the Pearson product-moment correlation coefficient sucks !

Neven

Finally a clear picture of the NWP. Looks quite navigable.

Kevin McKinney

I think you could probably take an icebreaker through, all right. We've been seeing this coming for a while now.

dorlomin

Steady on compadre, not to a ship yet, week or two though.

andrewt

Lovely whites floes near Cornwallis Island - multi-year ice pushed down from the North of the archipelago?

Anu

I think dying sea ice:
http://rapidfire.sci.gsfc.nasa.gov/subsets/?subset=Arctic_r02c03.2010204.aqua

looks like ink in water:
http://tinyurl.com/3yp2m7m

Or maybe a jellyfish:
http://tinyurl.com/35slyox

Thinning, thinning, swirly pattern, gone.

Anu

79,843 sq. km. lost yesterday (July 23) (before any correction).

By way of comparison, Banks Island, in the Canadian Archipelago, is 70,028 sq km in area:
http://www.geographicguide.net/pictures/arctic/arctic-map.gif

Imagine Banks Island squeezed into a long, thin area, and fitted to the sea ice coasts in the Beaufort Sea, East Siberian Sea, Laptev Sea, Kara Sea, Greenland Sea, Baffin Bay, and some left over for the ice between the Canadian islands.

Day after day after day, the big mass of sea ice will shrink inwards, eaten away at the margins. A thousand km of sea ice coast, melting just 70 km (just 250 pixels by 17.5 pixels in those 4km per pixel Rapidfire images) is 70,000 sq km lost that day:
http://rapidfire.sci.gsfc.nasa.gov/subsets/?mosaic=Arctic.2010204.aqua.4km

I wonder if the ice will melt through in the interior ? There are some big areas of low concentration ice starting to open up, with open water 6 km * 6 km in places:
http://rapidfire.sci.gsfc.nasa.gov/subsets/?subset=Arctic_r04c03.2010204.aqua

David Klein

On my spreadsheet I decided to do a comparison between 2010 and 2009 checking how long it took to melt the 1st, 2nd etc melt of a million Sq Km in terms of days. It came out as follows; in brackets 2009.
1st million; 2010 26 days (48)
2nd million; 2010 13 days (23)
3rd million; 2010 15 days (16)
4th million; 2010 15 days (16)
5th million; 2010 15 days (14)
6th million; 2010 13 days (14)
7th million; 2010 16 days (9)
The comparison shows, in my view, that 2010 encountered a lot of 1st year ice which melted rapidly. When it had to melt the 7th million, two factors came into play (1) having to attack ice volume rather than extent and (2) an extended period of unfavourable weather. Over the remaining 2009 melt season 23 July to 13 September, the ice extent reduced by 2.31 million Sq Km at a rate of 44,500 per day. By comparison 2008 melted 3.06 million Sq Km over 48 days at a rate of 64,000 Sq Km/day. If 2010 were to melt at an inbetween rate of 54,000 Sq Km/day over say 52 days (2,800,000 million Sq Km), 2010 would end up to have a minimum extent of 4.86 million Sq KM's. If the melt rate acellerates, we could still come close to 2007. Whichever way, it is clear that the arctic sea ice extent is not fully recovering from 2007. While 2010 has slowed on the extent side, I am convinced that it is doing huge damage to the volume. In that context it will be interesting to see how 2011 pans out. I predict that it may leave a lot of people gasping. Can't wait for Cryosat 2 to make the volume less of a guessing game. PS 2009 and 2010 drew level today with just 1 day difference.

Artful Dodger

Anu: Now that the U.S. Senate has fumbled the Clean Energy Bill, it may be best to tell your 6-yr old daughter that Santa is moving to the South Pole. The ice their will probably last 300+ years :^(

Neven

Wasn't it Lord Soth who had a 6-old daughter? Perhaps Anu has one as well. I know I have. Luckily I never told her of the non-existence of Santa Claus. ;-)

I wonder if the ice will melt through in the interior ?

That's a very good question. I wouldn't mind those adverse weather conditions to stay as they are, just to see what happens if it holds up long enough. But I don't mind weather conditions to fully reverse again either.

Artful Dodger

Did you Know? The predominant wind direction over the Arctic Ocean rotates the surface water in a large circle, called the Beaufort Gyre, which makes the polar ice move slowly in the same direction, too. Sea ice that lies close to the centre of the gyre can complete a full 360° circle in a matter of 2 years, but that which is furthest from the centre requires 7-8 years to complete the same circle.

In addition to the Beaufort Gyre, the surface circulation in the Arctic Ocean is dominated by the Transpolar Drift, which consists of wind and ocean currents that cross the entire ocean from Siberia to exit through the Fram Strait.

Fridtjof Nansen discovered this drift and proved its existence by allowing his ship, the 'Fram', to freeze into the ice off Siberia. It escaped the grip north of Svalbard 3 years later (1893-1896). In 2006, the schooner, 'Tara', did the same, but because the wind systems have changed and the sea ice has become thinner the journey took only half the time, 16 months.

Artful Dodger

Apologies to 6-yr olds everywhere... What will we tell them when they ask why we didn't act?

I don't think it matters if the ice melts through. Now that its broken up and mobile, it'll just be advected south through Fram Strait over the next 2 years or so. Unfortunately, this occurs during Fall and early Winter as much as now, which we consider the melt season.

Nick Barnes

Well, it's a good theory Artful Dodger. Unfortunately the Gyre and the Drift haven't been operating normally for months. Hardly any ice has been exported. If ice movement had been normal, we would have lost a lot more ice.

Artful Dodger

Nick, don't confuse 'weather' with 'climate'. What we've seen with the tepid gyre since June 26 is 'weather'. The gyre will return to normal. And now that the Central basin pack is broken up, it's fragments will be advected over time. The end game has started, and the results are not in doubt, whether it takes 2 years or 8.

Phil263

"Unfortunately the Gyre and the Drift haven't been operating normally for months..."

The Gyre and Drift were operating in June ( NSIDC report 5 July), It hasn't been operating since early July, that's probably why the melt in July is at a record low. As Artdul Dodger says, it's weather not climate. It will take many years before we can confirm that the weather pattern has changed, just as it will take many years before we can say that 2007 was a marker of climate change in the arctic basin, rather than a once-off anomaly.

Nick Barnes

Well, I commented on this blog many weeks ago - certainly not in July, maybe not even in June - that the ice to the north-east of Greenland was not moving in the appropriate direction (i.e. it was moving NW, not SE towards the Fram Strait). I was told that this was normal, the action of the Gyre (which in fact doesn't usually reach that far east). I've also been watching the ice north of Svalbard since some time in May, and have watched it drift aimlessly around throughout that time. In other years, the Drift takes it decisively south and out.

Yes, the change in the Gyre and Drift are recent. But not that recent.

What was that paper predicting changes to the motions of the central pack?

Artful Dodger

Hi, Nick. I think the 60 Day Drift Track from the Arctic Buoy Program shows the sea ice motion tendency quite well, as well as recent meandering.

Gas Glo

How frequent is it for Banks Island to be circumnavigable (or whatever the appropriate word/phase is) ?

Is there a record of dates when this has opened up?

Lord Soth

The revised sea ice loss is 84,375 sq Km. With an increased loss, we stand a good chance of a century loss tomight.

Greg Wellman

The NWP may not yet be navigable to a fiberglass hull, but if Henry Larsen was around today, he'd take the St. Roch through that rubble in a heartbeat.

On extent vs volume - I've started to refer to the central basin as "the great northern slushie"

Lord Soth

The gap is opening at the North Pole Web Cam Site #2, and a new gap may be forming.

http://www.arctic.noaa.gov/latest/noaa2.jpg

We may lose camera 2 soon.

Anu

Wasn't it Lord Soth who had a 6-old daughter? Perhaps Anu has one as well. I know I have. Luckily I never told her of the non-existence of Santa Claus. ;-)

No, just a 2 year old daughter.
Santa, Homer Simpson, Nemo, Mulan, Mickey Mouse, Senator Inhofe - she's not too worried if someone 'exists" or not, at this age.

I wonder if the ice will melt through in the interior ?

That's a very good question. .
http://arctic.atmos.uiuc.edu/cryosphere/NEWIMAGES/arctic.seaice.color.000.png

If that big mass of green/blue melts through (how thick are those ice floes ? 1 meter ? 50 cm ?), that becomes black water which heats up and becomes the source for a spreading zone of melting. It could send this summers minimum zooming past 2007, and also have repercussions for next year (preconditioning - less ice volume to melt).

I don't think that has happened before in Arctic summer melting - I think the melting has always been on the fringes of the Arctic Basin, melting inwards. I wouldn't be surprised if one summer soon things get very weird, though - and this might be that summer.

Neven

With an increased loss, we stand a good chance of a century loss tomight.

I agree, CT sea ice area anomaly has gone down again, the PIPS ice displacement forecast is showing arrows pointing towards the pole, reflected by the fast sea ice area drop in the East Siberian Sea, there's high over Greenland and a low between Kara and Laptev, etc.

Neven

I can't imagine real holes forming in the centre of the ice pack. With all that mobile ice, wouldn't the holes just be filled up by other floes, irrespective of where the winds are coming from?

It could only happen if, around this phase of the melting season, winds stop blowing for a week or so, and warm currents, sunshine and air do their thing. But I'm sure that's contradictory, meteorologically speaking.

It would look amazing though.

Charles Wilson

Actually areas-- called Leads, ALWAYS open up, even in Mid-Winter -- especially with lots of Wind. As the the flat Ice sheets pile on top of each other, you get double, triple, etc. thicknesses. When it is Cold, they quickly freeze over -- most "First Year Ice" is generated this way, and even though brief, it is WHY Warm Ocean Currents keep the Arctic 60+ degrees (F) warmer than the Antarctic in Winter.

But you may refer to the hints in the July 20 update at NSIDC & some maps, that the Arctic Ice is THIN ENOUGH to just collapse, rather than melt in from the edges. Well, the New SIberian Island Polynnya (or open Water) has formed & done that in both 2007 & 2010, in 2007 opening half-way to the Pole in the 6 days AFTER August 25, and absorbing a little "pond" at that point.

Can it happen - - look at the PIOMAS chart -- the update of July 17 from june 18 showed only 100 cubic km drop in "anomaly" (from -10,700 to -10,600, with -14,200 corresponding to a ZERO Ice Minimum & 2007 being -9250 -- by the Icesat reading of 6000 in Novenber 2007, less PIOMAS's Spt-Nov. Change) -- in other words, I don't know for sure, but if Wayne Davidson is right, at some point the Stationary Clear Skies return for Months, due to the La Nina. They are already climbing up the West Pacific above Japan - - but is it days, weeks, 2 months ?? - - every Day the Sunlight is decreasing. Yes, I do feel it will "cascade" into a MASSIVE hole in the middle, from the Taimyr area, but I drop my fears of an Ocean Current Shutdown with every Passing day.

Artful Dodger

Charles, welcome to the forum! I appreciated your courageous prediction for the 2010 Arctic Sea Ice Minimum. I believe you've correctly characterized the final disposition of the sea ice. Whether it occurs this year, or 3 years from now isn't important. The die is cast.

Artful Dodger

Anu asked "how thick are those ice floes ? 1 meter ? 50 cm ?"

If we take July 17 PIOMAS volume as ~3600 km^3 and IJIS sea ice AREA as ~6.48 km^2, then AVERAGE sea ice thickness of all Arctic Sea Ice is about 0.56 m, or 56 cm.

Of course, there is no indicator of variability in thickness in this estimate.

Note that about 1 meter of Sea Ice thickness is trimmed during an average melt season. So yes, we may see local collapse in many places. Watch for the holes!

Neven

Welcome from me too, Charles. Even though your predictions make me slightly nervous, I hope you'll comment here and there as we enter this melting season's final weeks.

Anu

@Artful Dodger | July 25, 2010 at 00:24

Good point, we can figure out the average thickness - I had forgotten about this graph:
http://psc.apl.washington.edu/ArcticSeaiceVolume/images/PIOMAS_daily_mean.png
I downloaded it and examined it in some detail, and got 15,100 km^3 as the average for July 23.
Since the anomaly for this date (July 17, I assume it hasn't changed much in 6 days) is about -10,600 km^3:
http://psc.apl.washington.edu/ArcticSeaiceVolume/images/BPIOMASIceVolumeAnomalyCurrent.png

I get 4,500 km^3 for the Arctic sea ice volume for July 23 (I'm not sure where you get 3600 km^3 for July 17).

Again, downloading and examining precisely this graph:
http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Area.png
I get 6.18 million sq km for July 23.

Since 6.18 million sq km * 1 meter = 6,180 km^3, 4500 km^3 means 0.73 meters thick sea ice (73 cm) - pretty close to your 56 cm.

And agreed, this is average thickness for all remaining sea ice - some will be much thicker, some much thinner. Maybe those slush areas in the Arctic Basin are large ice floes 30 or 40 cm thick - people will be very surprised if 1000's of sq km just melts away in late August, at the height of the bottom melt season.

Anu

Note: look at that PIOMAS_daily_mean graph again:
http://psc.apl.washington.edu/ArcticSeaiceVolume/images/PIOMAS_daily_mean.png

The annual minimum ice volume average is in late August (starting about August 20), not in mid September.
That's interesting. The sea ice extent and area continue to fall into mid September, as the volume is beginning to grow again. Compaction ? Ocean heat inertia of fringe melt, as the center of the Arctic Basin begins to freeze thicker from the bottom because of less and less sunlight ?

I had assumed, before, that September minimum sea ice area corresponded with minimum sea ice volume.

Jon Torrance

Anu,

Perhaps minimum sea ice area and minimum sea ice volume do coincide but the date of minimum sea ice area has been later recently compared to early in the 1979 to 2009 period that graph is based on. Though I can't recall anyone ever claiming that the Arctic sea ice used to typically happen as early as mid to late August so I'm by no means confident I've guessed a correct explanation for the apparent contradiction.

Artful Dodger

Hi, Anu. I just used C.W.'s figure of 3600 km^3 from his post earlier today. Looking at the PIOMAS "Daily Averaged" graph myself, I estimate the mean sea ice volume for Jul 17 at 16000 km^3 (Charles seems to have used 14200 km^3 for average ice volume).

If the volume anomaly for this year is 10.6, then the total volume is 16.0 - 10.6 = 5.4 x 10^3 km^3. This changes the average thickness estimate for July 17 to 0.83 m or 83 cm. Significant, but still notably less than an average year's total melt.

I find it problematic that UWash is only releasing graphs to the public, but no numerical results that can be used for further analysis. I based my Area figure on July 17, to match the PIOMAS volume estimate.

Jon Torrance

Anu,

Also, looking at that chart, can we be absolutely certain the tick marks on the x axis mark the beginning of the month in question and not the middle of the month? If they mark the beginning, why is there data before the circle over the January tick mark?

Anu

@Jon Torrance | July 25, 2010 at 05:10

I hadn't considered that - if minimum volume/area do always coincide, can the graph be explained as smaller and smaller minimum volumes since 2002 or so coming later in the year, but not carrying enough weight in the "average" to shift the curve minimum later ?
http://psc.apl.washington.edu/ArcticSeaiceVolume/images/PIOMAS_daily_mean.png

I know the melt season has been getting longer and longer since 1979:
http://earthobservatory.nasa.gov/IOTD/view.php?id=42456&src=eoa-iotd
by some 25 days, but I don't remember seeing dates for the minimums back in 1979 or the early 1980's...

http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php
September Ice Volume was lowest in 2009 at 5,800 km^3 or 67% below its 1979 maximum.
And the average minimum is about 13,300 km^3.

I'd have to think about this, but you might be on the right track - maybe it explains half of the graph, and fringe melting/center thickening explains the other half, something like that...
Thanks for the insight.

Anu

@Artful Dodger | July 25, 2010 at 05:15

Haven't checked your math, but I'll assume it's correct, for now :-)
That means the average Arctic sea ice thickness went from 83 cm to 73 cm in 6 days.

That sounds pretty significant - 10 cm of melt, on average. If there are large sections of "thni" Arctic Basin ice, say 40 cm thick (because an average of 73 cm can have 3 meter thick ice in some places, 40 cm in others), then at this melt rate, those sections would melt in 24 days. Then we get to see if holes in the ice pack are filled in with drifting floes from the surrounding ice, or if the hole would just lazily drift with the surrounding pack.

Anu

@Jon Torrance | July 25, 2010 at 05:36

Hmm, another good point. If the month marks are the middle of the month, then my volume calculations are off (too low), and the annual minimums line up much better with mid-month September.

But in this graph,
http://psc.apl.washington.edu/ArcticSeaiceVolume/images/BPIOMASIceVolumeAnomalyCurrent.png
the years seem to be marked at the beginning of the year, not the middle.

Not that both graphs have to be consistent...

Perhaps someone will have to read those References to find out definitively:
http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php

p.s.
102,500 sq km melt today:
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

Artful Dodger

Anu: Yeah, and the weird thing about averages/distributions is that a single 100 km^2 floe of 3 m thick ice, means there must be a corresponding thin area to maintain the average of .83 m thickness. Even if the thinned area is 360 km^2 it would be just 60 cm thick. So, a potential hole, and a place for the sea ice to be un-roald by the end of the season.

Artful Dodger

At Jon Torrance | July 25, 2010 at 05:10 >i>"Perhaps minimum sea ice area and minimum sea ice volume do coincide but ..."

Loss of Ice volume occurs roughly when total solar insolation equals heat lost to the atmosphere at night. This balance point depends on latitude, but is a fairly flat curve in August.

Loss of total Ice Extent continues into September as winds and currents continue to compact the ice. For example, 2007 saw the minimum extent on Sep 24.

Ice Extent finally starts to grow when the rate of freezing outpaces the rate of compaction.

siili

The interpretation of the average graph with the dots showing middle of the month data makes more sence, and making a very rough estimate for today using a Cryosphere Today area of 5 and a reading from piomas of 6 gives an average thickness of 1.2 meters.

This also seems to be in accordence with the Piomas forecast movie for today where about a third of the interior area has a thickness of 1.5 meters and the mean thickness for the rest evenly diveded above and below 1 meter.

The coverage of the Piomass forecast also seems to be in very good accordance with the actual bremen data especially considering that the model was only "realigned" with the measured extent on July first, and since then has been driven with mean forcings for the last 10 years.

Considering Zhengs forecast of 4.8 minimum and the rather thick remaining ice on the Russian side in the model, this may turn out to be an overestimate if the rest of the melt follows the plan.

Neven

I was expecting a bit more than a 102,500 square km melt. We'll see if it survives the revision. The number has been revised downwards twice so far.

Artful Dodger

@Jon Torrance | July 25, 2010 at 05:36

"can we be absolutely certain the tick marks on the x axis mark the beginning of the month in question and not the middle of the month?"

Yes, the ticks on the X-axis of the PIOMAS Daily Mean graph mark the beginning of each month.

The width (in pixels) of the monthly boundaries corresponds to the number of days in that Month.

Jon Torrance

Artful Dodger,

I don't really have a dog in this fight (or rather, thankfully, civilized discussion) but commenter #52 on the new Real Climate thread expresses equal certainty to the contrary - see http://www.realclimate.org/index.php/archives/2010/07/an-icy-retreat/comment-page-2/#comment-182345. Absent a clear explanation one way of the other from the PIOMAS crew, I'm still left having a hard time believing the tick mark at the beginning of the month interpretation is correct and they're showing the data for the latter part of December to the left of the January data rather than at the extreme right hand side of the graph next to the rest of December.

Charles Wilson

3600 and 14,200 were meant to apply to the September Minimum -- Charles Wilson.
... I see you all got into the Wonderful World of Bottom-feeding, when after getting the Data Right, Professors give a Grad Student the task of feeding the Public with a Graph. Since the 3 Graphs -- Mean, Icesat vs Piomas & BPIOMAS (BIG Piomas) -- fail to share a common scale, and disagree on the Sept-Nov 2007 Anomaly number, I did my best, relying on the ICESAT number of 6000 km3 as my basis (Lasers make for Very narrow tracks, so they build up a pic over a month, then a 2nd, lest they have a month's difference between 1 reading & another. Then they can extrapolate midpoints for each location & give it out as " November 1". No idea whether the Mean 's Dots are Monthly means or that day.

Artful Dodger

@Jon Torrance | July 26, 2010 at 22:03

The commenter you referred presented no evidence, so not sure why you've referred.

Did ya actually count the Monthly width in Pixels for yourself? Wish i had time to hold your hand!

Jon Torrance

@AD

I didn't even try to count pixels - no reason to think you didn't do it accurately. Plus I'm not sure I find the pixel argument convincing. If someone's relationship to graphical conventions is so loose they can present an annual graph starting in the middle of December without putting up the equivalent of a giant billboard announcing that's what they did, I wouldn't put it past them to have the tick marks not even be in the right place with respect to the data.

As to the Real Climate comment, I've no reason to think the commenter is an authority but, to the extent there's something to the wisdom of crowds, the fact that no other commenter has seen fit to defend Joe Romm's honour by offering a correction is suggestive. RC readers/commenters are generally a pretty knowledgeable lot.

It's not important except inasmuch as people are trying to do back of the envelope calculations with numbers derived from the charts.

Jon Torrance

I've now satisfied myself that the tick marks indicate the middle of each month by consulting the PIOMAS web site - http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php - which says:

" PIOMAS calculates that the monthly average Arctic Sea Ice Volume for May 2010 was 19,000 km^3, the lowest May volume over the 1979–2010 period, 42% below the 1979 maximum and 32% below the 1979–2009 May average."

Based on that, the May average ought to me about 27,941 km^3, which pretty much matches the circle directly over the May tick mark. Since the average volume drops steeply from there to about 25,000 by the June tick mark, the May average would have to be around 26,500 if the tick marks indicated the beginning of each month.

Evilreductionist.blogspot.com

It looks to me as though the average volume loss between mid-July and September is 4,000 cubic kilometres. Given that it seems as though we were less than 8,000 cubic kilometres mid-July, we are looking at a very low volume by the end of this melt season - and that is assuming that it melts at an *average* rate over the next 6 to 7 weeks.

Peter Ellis

AD: The fact that the width of the months is correct (in pixels) doesn't mean the ticks are on the 1st of the month, it just means they're on a fixed day of each month. It's plausible that (for example) they mark the 15th of each month. That would reconcile your observations with JT's.

Artful Dodger


@Gas Glo | July 24, 2010 at 17:20

"How frequent is it for Banks Island to be circumnavigable? Is there a record of dates when this has opened up?"

The wreck of the HMS Investigator has been found. She was a British ship lost to the sea ice in 1853 after circumnavigating Banks Island in search of Franklin. Her crew is credited with discovering the Northwest Passage.

The article says "The clear Arctic water makes it possible to glimpse the outline of the ship's outer deck, which is only eight meters below the surface. Three graves were also found Tuesday. They are undoubtedly the remains of British sailors who succumbed to disease in the final months of the ship's three-year Arctic ordeal."

Neven

The wreck of the HMS Investigator has been found.

My, that was quick. I wrote only a few days ago that they were going to start looking for it.

Gas Glo

Thank you for the reply AD

Artful Dodger

Neven wrote July 24, 2010 at 21:51

I can't imagine real holes forming in the centre of the ice pack. With all that mobile ice, wouldn't the holes just be filled up by other floes, irrespective of where the winds are coming from?

It could only happen if, around this phase of the melting season, winds stop blowing for a week or so, and warm currents, sunshine and air do their thing. But I'm sure that's contradictory, meteorologically speaking.

It would look amazing though.

Why yes. Yes, it does. ;^)

My how the world has changed in just 3 short years!

Cheers,
Lodger

Neven

Thanks for reminding me of this, Lodger. :-)

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