Are we getting used to this? After the persistent cyclone in May and June, and the spiffy, but short-lived cyclone of two weeks ago, the Arctic is visited by yet another intense storm that goes below 980 hPa. In fact, according to Environment Canada it is currently at 976 hPa, which is lower than the lowest pressure of the previous storm (click for a larger version):
Do also note the high pressure over the Beaufort Sea, Canadian Archipelago and Greenland. Yesterday's DMI SLP map also shows the storm developing:
According to the ECMWF weather forecast the storm will stay intense today and tomorrow, and then wind down again, albeit more slowly than the last one, and accompanied by more high pressure on the American side of the Arctic (click for a larger version):
I don't know what this will do to the ice pack. The storm is pretty fierce, but still doesn't come close to the intensity and duration of last year's GAC-2012. It still isn't clear what damage the two previous storms did either, as cyclones also bring in cold and clouds.
I also don't know how unusual it is to have three of these cyclones in one single melting season. I've only been watching the ice as intently as I do now since starting the blog in 2010. There was a big, but short-lived storm in late August in 2011 and we all remember last year's Great Arctic Cyclone. It almost feels like this year the atmosphere 'wants' to do a repeat, but doesn't quite succeed because there's more ice.
But feeling isn't knowing or even speculating, so I'll leave it at that for the time being. This post will be updated if anything interesting happens.
Erimaasa,
Did you use the August 9 or August 10 AMSR2 map for calculating your numbers?
Posted by: Jenny E. Ross | August 11, 2013 at 19:09
Henry, if you truly don't understand why the 'cooling since 2002' meme is deeply wrong, I would be glad to discuss it offline, and that's all I have to say on that topic in this forum.
Posted by: Kevin McKinney | August 11, 2013 at 19:13
Sorry, Erimaassa -- I was so focused on the numbers that I didn't notice the date you put at the beginning!
Posted by: Jenny E. Ross | August 11, 2013 at 19:14
"...moshpit of gnosticide..."
Delicious phrase about a not-so-delicious reality.
Posted by: Kevin McKinney | August 11, 2013 at 19:16
@wayne,
Please note how sea ice area and sea ice extent are defined:
http://arctic-roos.org/observations/satellite-data/sea-ice/ice-area-and-extent-in-arctic
It is possible that SIE numbers are being increasingly overestimated as you mention, but area should not have this problem.
Posted by: John Christensen | August 11, 2013 at 19:23
For reasons similar to yours I prefer following the SIA numbers, but scientists tend to prefer extent numbers, I believe due to estimation errors related to melt ponds that impact area numbers more, but not entirely sure.
Posted by: John Christensen | August 11, 2013 at 19:26
Thanks for the off-topic Gish Gallops, Henry, but I'm the janitor of this blog, not the policeman. So have fun at WUWT celebrating the fact that Arctic sea ice records aren't broken every melting season.
I hate blocking people, but I really don't have time for that same-old, same-old.
Posted by: Neven | August 11, 2013 at 19:38
"""It is possible that SIE numbers are being increasingly overestimated as you mention, but area should not have this problem."""
I think so, I have a feeling we have a lot of 15.something % cells all over the Arctic Sea.
Posted by: Espen Olsen | August 11, 2013 at 20:45
Thanks John,
NSIDC link I gave shows otherwise :
"Area takes the percentages of sea ice within data cells and adds them up to report how much of the Arctic is covered by ice; area typically uses a threshold of 15%"
this explanation may need some refinement.
Posted by: wayne | August 11, 2013 at 21:03
Espen, A-Team did a nice post over on Update 6, but if you look at his favorite microwave channel in Aug 2012 http://www.ijis.iarc.uaf.edu/seaice/data/INDEX/201208/AM2SI20120810IDX_high.png and again this year http://www.ijis.iarc.uaf.edu/seaice/data/INDEX/201308/AM2SI20130811IDX_high.png your 15 something is more than a feeling, I think. This year is so different.
Posted by: Doug Lofland | August 11, 2013 at 21:09
The Drift !
The full-Text-Version of the Dissertation !
http://ediss.sub.uni-hamburg.de/volltexte/2011/5257/pdf/Dissertation.pdf
--
A fundamental difference from winter storms to summer storms is the deviation of the drift. In winter storms, the ice drift differs by about 5 ° to the right. In summer, it differs by 18 ° to the right.
These are for guidance only. The SST is just only one
Semester and no ST. The SST rather shows us the
Air temperature directly on the water surface.
In August, the sun was casting long shadows.
But because it penetrates under the clouds.
If the reflected short-wave radiation of ice (and water) to the top. Be absorbed by the clouds and scattered than longer waves diffuse. The air and the water take on it. The ice itself can to the rim, which acts rather wedge-shaped, reflect sunlight directly into the water. These are situations that can have very different effects that we only understand when the storm is over and the wind strikes an opposite direction. A not to be underestimated is the effect of salt to raise the water to the small ice floes. Even fresh snow can not prevent a basal melt. and
Deviation of 18 ° to the right makes the ice closer to the coasts., The Laptev Sea and the ESS are very flat. That is, sunken water with a temperature of 4 ° is not very deep down. It mixes quickly back up. But, we'll see what happens.
Posted by: Gerhard Trausner | August 11, 2013 at 22:13
...
In recent years we have had not a single "El Nino" year. There were consistently "La Nina".
You can see the SST anomaly at the equator in the eastern-Pacific. This does not mean that the sea has become colder. Only at the surface. It is very difficult to determine the average overall temperature of the sea. The ocean stores a large amount of energy that only comes to the surface again when the salinity of the deeper waters to equalize again in the salinity of the upper water. Then the flow behavior will change. A "ElNino" year can not be predicted. Not yet. A strong and pronounced "El Nino", the large-scale freeze the Bering prevent what a much earlier melting of the Chukchi sea can bring. What does this mean for the thin ice, as you can imagine. At the last "El Nino" was very much thicker the ice. however
even the many years in which we only had "la Nina", the melt of the ice could not prevent.
Posted by: Gerhard Trausner | August 11, 2013 at 22:58
@wayne,
That is ood. I find this at NSIDC:
http://nsidc.org/cryosphere/seaice/data/terminology.html
"Area
When we use this term, we mean the region covered by sea ice, typically given in square kilometers. For a grid cell, it is the area of the portion of the cell covered by ice. For an entire hemisphere, it is the total area covered by ice, which corresponds to sum of the area of each cell multiplied by the fractional concentration for that cell."
"Extent
Extent defines a region as either "ice-covered" or "not ice-covered." For each data cell, it is a binary term; either the cell has ice (usually a value of "1") or the cell has no ice (usually a value of "0"). A threshold determines this labeling. A typical threshold is 15 percent, meaning that if the data cell has greater than 15 percent ice concentration, the cell is labeled as "ice-covered." The Sea Ice Index products have a threshold of 15 percent. A threshold can also be as high as 30 percent."
Posted by: John Christensen | August 11, 2013 at 23:24
I thought my account was hacked for a minute. But apparently that is another "Henry".
Posted by: Henry1 | August 12, 2013 at 00:29
Personally I have always thought the 15% or more standard is a bit odd, I would think 45% is a much more logical place to pick for rounding up or down than 15%!!!
If you went back through all the gridded data for the last 34 years of the satellite record and calculated everything from a 45% standard I bet things would look even worse than they do today. It made some sense early on because a grid area with 15% ice meant a ship passing through had to navigate a little cautiously to avoid risking damage. Today I don't think that is a major concern when so much of the area is down right open water but obviously the major research organizations do not agree with me.
Using the 15% standard the entire Arctic ocean could be a giant slushy with 20% ice per grid point and it would show on the records as 100% ice/extent--area. Then a few days later it could drop 6 % to 14% average and suddenly it would be classified as ice free. This makes no sense to me.
Posted by: Allen W. McDonnell | August 12, 2013 at 02:17
John, look up:
http://nsidc.org/arcticseaicenews/faq/#area_extent
"What is the difference between sea ice area and extent?"...................
Area takes the percentages of sea ice within data cells and adds them up to report how much of the Arctic is covered by ice; area typically uses a threshold of 15%. So in the same example, with three 25 km x 25 km (16 miles x 16 miles) grid cells of 16% ice, 2% ice, and 90% ice, multiply the grid cell areas that are over the 15% threshold by the percent of sea ice in those grid cells, and add it up. You would have a total area of 662 square km (255.8 square miles).
Posted by: wayne | August 12, 2013 at 05:29
Gerhard:
I presume you mean to say that these are the clockwise deflections of the ice motion from cyclonic. I find this surprising.
The clockwise Coriolis deviation of the drift direction from the forcing wind direction should depend only on the time friction would take to stop the ice, and should be larger for longer times. The ice and entrained water should be deeper in winter, so it should have a larger deviation.
The only good explanation I can think of is that the storms would be larger in winter, which would increase the speed of drift, increase friction, and result in a smaller deviation.
Have you tried comparing the deviation with storms of identical strengths in winter and in summer? Can you see it changing with time, as the ice gets thinner?
Posted by: Blaine | August 12, 2013 at 10:03
Blaine,
Coriolis force dictated that the acceleration (in clockwise direction) depends on the speed of the moving ice.
Therefor, it should not be surprising that in summer, when the ice is thinner, the acceleration is large and thus the angle of deflection is also larger.
Posted by: Rob Dekker | August 12, 2013 at 10:30
More evidence for decreasing ice thickness as a cause for the increasing difference between ice drift and wind speed in this paper :
http://onlinelibrary.wiley.com/doi/10.1029/2011GL048970/abstract
which explicitly writes :
Thus it seems that the drift speed of Arctic sea ice is increasing while wind speed is not increasing significantly. The conclusion reflects that ice thinning is the cause :
which also explains the increased angle of deflection during summer, compared to winter.
Posted by: Rob Dekker | August 12, 2013 at 10:49
@wayne,
Yes, just read the text you inserted, and you should understand.
Area is looking at concentration.
Extent will consider a cell filled, if it passes 15%.
Both area and extent calculations disregard any grid cell with less than 15% ice concentration.
Posted by: John Christensen | August 12, 2013 at 11:03
notice that the Navy CICE models hindcasts have been properly adjusted, at least for ice movement ...at least to the extent possible
Posted by: Fairfax Climate Watch | August 12, 2013 at 11:11
Rob:
Yes, but the momentum is also proportional to the speed, so the angular rate of rotation has the velocity term cancel out. This of course makes sense because the Coriolis force isn't a force at all but the Earth turning and making the velocity appear to turn in its reference frame, and the Earth's rotation speed does not depend on the velocity of the object.
The only terms which actually enter into the calculation of the angle are the ratio of drag to the applied force and the latitude.
Posted by: Blaine | August 12, 2013 at 12:34
@Allen,
For the reasons you stated most institutions calculate both extent and area.
It also gives you meaningful information to compare development in both numbers for any given portion of the Arctic Ocean or seas.
Posted by: John Christensen | August 12, 2013 at 18:20
@Neven,
off-topic Gish Gallops
i like to think of a big bag full of a gish-gallop of bafflegab.
a "gish-gafflebag" if you will.
Posted by: Charles Craver | August 12, 2013 at 20:38
Blaine
The 5 ° in winter and 18 degrees in summer
Values at the same strong storms.
This information I have from the dissertation
by Arne Kriegsmann
Posted by: Gerhard Trausner | August 13, 2013 at 05:27
Blaine
The link to the dissertation
http://ediss.sub.uni-hamburg.de/volltexte/2011/5257/pdf/Dissertation.pdf
Posted by: Gerhard Trausner | August 13, 2013 at 05:35
Blaine
I also agree with you. The Coriolis force is not a force, only an apparent effect.
The deviation from winter to summer can also be caused by the lower ice concentration in summer. Characterized the ice has less resistance to the outside.
Posted by: Gerhard Trausner | August 13, 2013 at 06:17
Blain said
I've been trying to reproduce that statement with some simple physics diagrams, but were unable to do so.
In fact, after a few tries, I'm quite puzzled (and thus curious) as to how that angle can be determined from simple physics of ice motion and Coriolis forces due to wind sheer.
Do you have a reference to where you obtained your assertion, or if you based in on physics alone, can you give the calculations you used ?
I like this kind of puzzles.
Posted by: Rob Dekker | August 13, 2013 at 07:40
Regarding SIE and SIA, I find the ice concentration graphics in this product : http://ocean.dmi.dk/arctic/icedrift_anim/index.uk.php to be most useful, as a way of visually understanding the development of ice breakdown,impacts of storms, etc. The current lower concentration band through the middle of the ice is interesting, and appeared to be exacerbated by the storm.
Posted by: Robert S | August 13, 2013 at 07:48
Gerhard, thanks for the full dissertation to the angle of divergence observations.
I found this in the paper :
which suggests that further clarification of the angle of divergence (and the difference between summer and winter) due to wind sheer can be found in Thorndike and Colony (1982).
Posted by: Rob Dekker | August 13, 2013 at 08:38
Rob Dekker wrote August 13, 2013 at 07:40
Hi Rob,
This classic paper on the topic of Ekman transport introduced the physics nearly 50 years ago:
Hunkins, K. (1966, August). Ekman drift currents in the Arctic Ocean. In Deep Sea Research and Oceanographic Abstracts (Vol. 13, No. 4, pp. 607-620). Elsevier.
Abstract:
Hope this helps, and your local resources allow you access to the full paper. If not, there's a reasonably complete description of the math at Wikipedia.
Cheers,
Lodger
Posted by: Artful Dodger | August 13, 2013 at 10:49
Apparently the topic of ice drift is not as simple as one might think:
http://scholar.google.com/scholar?q=ice+drift+law&btnG=&hl=en&as_sdt=80005&sciodt=0%2C11&cites=11421538101964309241&scipsc=
Posted by: Kevin McKinney | August 13, 2013 at 13:55
Rob: I was doing the calculation myself.
Assume a constant driving acceleration A0 in an x direction along the surface of the earth, a drag acceleration -V/Tau, and Acoriolis = -2 Omega x V, and motion fixed to zero vertically.
Wait for steady state velocity.
Then 0 = Atot = A0 - 2 Omega x V - V / Tau
Take the y component along the surface of the earth, perpendicular to x and set it to zero.
0 = -Vy/Tau - 2 Omega Vx sin Latitude
Vy/Vx = -2 Omega Tau sin Latitude
Clockwise Coriolis Deflection = Arctan (2 Omega Tau sin Latitude)
This assumes that the effect of the ice stress is negligible, which Grehard says is not true in his thesis. The convergence-strain resisting stress of the ice would of course be greatest in winter when the ice is thickest, and Gerhard appears to be saying that this is the reason why the actual deflection differs in the opposite way from what would be predicted by free Coriolis drift. Or at least, I think that's what he means by characterized the ice has less resistance to the outside.
Posted by: Blaine | August 14, 2013 at 09:38
Thanks Blaine !
I have only a few minutes today, and assuming your first equation is a 'vector' equation, with x being the outer product, and your second one a scalar equation, I can't find anything wrong with your calculations.
Your calcs seem to suggest that the heavier the object (mass of ice floe) the larger its angle of deflection, given a certain wind shear (force).
That's interesting, and does indeed question why Thorndike and Colony (1982) found that in reality the angle seems to be smaller in winter than in summer.
I hope to have a bit more time tomorrow, to double check your equations, but it seems that you are on to some apparent paradox here.
Good work !
Posted by: Rob Dekker | August 14, 2013 at 11:00
So, given what has happened this season, the suggestion from HYCOM of what is happening in the Eastern Arctic, is it going to happen?
will we see a virtually Ice Free Eastern Arctic this year? An Ice Free North Pole.
Or is this some sort of coitus interruptus in potentio.
Aaargghh.....
Posted by: Glenn Tamblyn | August 14, 2013 at 13:21
The third Persistent Arctic Cyclone (PAC-C Aug13) died off a couple of days ago. It lasted six days – peaked below 980 hPa - and fulfilled the general criteria suggested earlier ahead of “PAC-B Jul13” (see http://neven1.typepad.com/blog/2013/07/the-naming-of-arctic-cyclones.html ) .
A few questions were raised during this event, e.g. whether this was a real “storm”?.
In Denmark we use the term “snowstorm” when at least 10 cm of snow falls within 6 hours and wind speeds exceed 10 m/s. Similar criteria are used in lowland parts of Sweden and Germany.
New evidence from a recent GRL paper ( http://onlinelibrary.wiley.com/doi/10.1002/grl.50517/pdf ) point to the fact, that even moderate winds (8-12 m/s) have a significant impact on the heat transfer from ocean to ice. Measurements taken north of Svalbard last year on a 0.8 m thick ice floe documented that - during windy conditions (similar to conditions this year during PAC-B & -C) - the heat flux from the ocean increased to near 70 W/m2.
Others have asked about the energy source for this storm. Advection of moist air from much lower latitudes (as alluded to here: http://neven1.typepad.com/blog/2013/07/second-storm.html?cid=6a0133f03a1e37970b01901e9abeaa970b#comment-6a0133f03a1e37970b01901e9abeaa970b ) may be one of the sources, leading to condensation and snow fall over the ice pack. A rough back-of-the-envelope calculation gave a record low (since 1948) SST gradient from the Caribbean to the Barents Sea of roughly 17 K (30-13 deg C) during the storm. The distance is roughly 11,000 km, which means that the average gradient is around 0.0015 K/km. This number happens to be in the same ballpark as the Equator to Pole temperature gradient applied by W. Langford (see the second diagram in slide 25 in his presentation: http://www.fields.utoronto.ca/programs/scientific/10-11/biomathstat/Langford_W.pdf ). It is a disturbing fact that such a low temperature gradient may have led to direct advection of moist air all the way from the Caribbean to the Barents Sea at the same time as the low was churning in the Arctic. If NH single cell configuration and persistent Arctic cyclones is one and the same thing, we may indeed be closer to the tipping point, than we thought.
The lasting impact from this particular cyclone remains to be seen, as the clouds disappear later in the melting season. Recent photos from some of the buoys show up to 15 cm of fresh snow on the remaining ice floes, which may affect both albedo and insulation of the sea ice.
Do I have to mention, that a new deep Arctic cyclone has appeared in the far end of the current weather forecasts…
Posted by: P-maker | August 14, 2013 at 15:27
@P-maker,
Thanks, these are very interesting findings.
Referring to this article, The Summer Cyclone Maximum over the Central Arctic Ocean, Mark C. Serreze and Andrew P. Barrett, 2008, Journal of Climate, which was referenced in the 'On persistent cyclones' thread, I guess you are not saying that Arctic summer cyclones are a new phenomena, but rather that the apparent formation of a NH single cell would further fuel the Arctic cyclones and therefore further enforce these, as the channeling of tropical moisture is enhanced?
If that is the case, it would seem this is a negative feedback, as it appears the cyclones are reducing ice melting (which we will be able to evaluate by the end of the melting season).
Posted by: John Christensen | August 14, 2013 at 16:53
John
Please have a look at the Barrow Web Cam: http://seaice.alaska.edu/gi/observatories/barrow_webcam and
the Healy Web Cam: http://icefloe.net/Aloftcon_Photos/index.php?album=2013 and
the North Pool Web Cam: http://psc.apl.washington.edu/northpole/NPEO2013/18.jpg and
the Canadian Met Service analysis: http://weather.gc.ca/data/analysis/935_100.gif and
the DMI NE Greenland satellite imagery: http://ocean.dmi.dk/arctic/images/MODIS/NEW/201308141358.jpg and
the ECMWF 240h forecast: http://www.wetterzentrale.de/topkarten/fsecmeur.html
and tell me once more that all of this is the result of a negative feedback.
You’d better put the kettle on for that cup of coffee you promised me a while ago.
My bike is pumped and ready to roll!
Cheers P
Posted by: P-maker | August 14, 2013 at 21:07
@P-maker,
See:
James A. Screen, Ian Simmonds and Kevin Keay, 2011, Journal of Geophysical Research
From the introduction:
The perennial (September) Arctic sea ice cover exhibits large interannual variability, with changes of over a million square kilometers from one year to the next. Here we explore the role of changes in Arctic cyclone activity, and related factors, in driving these pronounced year‐to‐year changes in perennial sea ice cover. Strong relationships are revealed between the September sea ice changes and the number of cyclones in the preceding late spring and early summer. In particular, fewer cyclones over the central Arctic Ocean during the months of May, June, and July appear to favor a low sea ice area at the end of the melt season. Years with large losses of sea ice are characterized by abnormal cyclone distributions and tracks: they lack the normal maximum in cyclone activity over the central Arctic Ocean, and cyclones that track from Eurasia into the central Arctic are largely absent.
- taken from 'On persistent cyclones'.
Late season cyclones will certainly have a different impact on the ice and I do not know what it will look like by the end of the melting season, but it does appear the cyclones have reduced melting this far. Barrow had perhaps some ice in 2008, but has since been ice-free by this time.
That said, I live in Nærum and you are very welcome to come over. Espen is 5km from here, so could join - irrespective of the ice development in the next weeks.
Posted by: John Christensen | August 14, 2013 at 22:43
@P-maker,
The Healy is passing the Aleutian Islands right now, so had you expected to see any ice there in August??
And I checked the NP webcam this morning - looks cold up there.
But that is not the point; in data from PIOMAS and CT, it appears that the cold brought by the cyclones has more than outweighted the increase in melting caused by the force of the storms, but again we really need to see what everything looks like by mid/end-Sept to analyze the impact.
Right now the ice is certainly very thin, with huge red areas(on CT), dotted with yellow and green holes in the pack, except in the highest concentration areas right north of CAA and Greenland.
Posted by: John Christensen | August 15, 2013 at 11:54
John,
She is docked in Barrow at the moment?
http://www.sailwx.info/shiptrack/shipposition.phtml?call=NEPP
Posted by: Espen Olsen | August 15, 2013 at 12:32
Espen,
You are right, I had just checked on marinetraffic.com and had not noticed their last position was from 7/30, thanks.
Will you join for Arctic coffee?
Posted by: John Christensen | August 15, 2013 at 12:47
I really don't like ice coffee BTW, so it would be nice and hot - like the Arctic..
Posted by: John Christensen | August 15, 2013 at 12:48
What coffee?
Posted by: Espen Olsen | August 15, 2013 at 13:13
Sorry; I was going on earlier on the entry for the second cyclone (PAC-2) back in July that the cyclone could cause the melt to slow down, as we saw with PAC-1, and that by the end of August if the cyclones turned out to have a net negative impact on ice, I would offer coffee..
Posted by: John Christensen | August 15, 2013 at 13:21
A fourth one:
Fourth storm on it's way!
Posted by: Kris | August 17, 2013 at 13:25