As the storm is still there, big, but no longer strong, and comment threads fill up quickly, I figured it's time for an open thread. And yes, it's a bit of an update as well, with interesting comments and graphs.
But first the updated animation. Now that the swathe of ice floes in the East Siberian Sea has detached itself, it's time to slowly say bye-bye to the ice atoll in the upper left corner:
sea ice concentration maps courtesy of the University of Bremen
Here's a comment by Rob Dekker that I want to put the spotlight on, because it's very interesting and gets to the core of the consequences of this storm:
I understand Neven's position that we should wait and see what the impact of the storm will really be after the clouds are gone, but let me tell you that I have a very bad feeling about this one.
Last year, with the "flash melt" during the November storm, I was confident that the "flash melt" was mostly caused by sea water flushing over the ice, which only temporarily (and artificially) confuses the satellite sensors in believing that large swats of ice have turned to water.
At that time, the ocean flux data from ITP buoys revealed that ocean water was stirred up down to 25 meter or so, which caused some salty water to bubble up to under the ice, with the potential to 'flash' melt out about 10 cm from the bottom of the ice pack.
This storm however, is completely different.
For starters, freezing has not yet started seriously, so any flushed-over ice will take longer to re-appear on the SSMI satellite instruments. Second, the ice pack in the Western Arctic was already heavily fragmented even before this storm even started. There were plenty of polynia and areas where ice concentration was no more than some 50 %. This means that the "flash melt" area starts to behave much more like "open ocean" than an area with a semi-solid ice pack.
But even worse, this storm seems to have stirred up not just the upper halocline at 20-75 meters, but even the lower halocline at a 200-500 meter depth. Two separate ITP buoys, separated by a few hundred km, record this disturbance so it is not just a local event :
Several studies show that the upper halocline can be disturbed down to some 50 meters, and these are great reads :
but I've not seen anything like this disturbance down to 500 meter over a wide area ever before in the ITP records.
What does this mean ? Well, the stratification layers in the West Arctic in the "flash melt" zone seem to be completely eliminated for the moment. This brings up 'warm' and more importantly, 'salty' water to the surface (and cool, fresh water downward). The saline anomaly at the surface is disturbing : it increased from 25 psu to about 31.5 psu over the past couple of days. That means that the melting temp of sea ice just reduced by 0.5 C, and this is even without counting the increase in water temperature towards the surface that the stirring down to 500 meters causes.
It's hard to estimate how much ice melt this will cause, but since the storm still is causing significant water movement along the ice (ITP53 reports rock-and-rolls of 0.8 m/sec) as well as up/down welling, and because the crumbled ice above has a large surface area to absorb the heat, melting may resemble sugar in a stirred cup of tea right now.
The real important question is, how long will this de-stratified state persist ? The short answer is that we simply don't know. Ocean models (even without ice cover) are simply not yet capable of simulating deep ocean turbulence effects after a storm. Here is a good read:
So after all is said and done, it seems that Neven was right and we need to wait out this storm to assess what it's long-term effects really will be. But at the same time, the de-stratification this storm has caused down to 500 meter depth and the mixing of salinity and heat content throughout that column over the area of this storm (about 1 million km^2) will most certainly have caused very significant damage to the already fragmented ice pack, to the point that it become hard to believe that the entire area or even part of it will somehow magically re-appear on the satellite record.
I think the "flash melt" area is knocked out for the season, and on top of that this storm will leave a lot of salty water behind at the surface, which will eliminate small pockets of ice remaining and make it harder for the area to freeze up in fall.
Someone from NASA’s Earth Science News Team mailed me to tell me that they have been following this story since Monday and decided to put out some images of the storm. Here's one they put on Flickr:
With the following text:
Summer Storm Spins Over Arctic
An unusually strong storm formed off the coast of Alaska on August 5 and tracked into the center of the Arctic Ocean, where it slowly dissipated over the next several days.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color mosaic image on August 6, 2012. The center of the storm at that date was located in the middle of the Arctic Ocean.
The storm had an unusually low central pressure area. Paul A. Newman, Chief Scientist for Atmospheric Sciences at NASA Goddard estimates that there have only been about eight storms of similar strength during the month of August in the last 34 years of satellite records. “It’s an uncommon event, especially because it’s occurring in the summer. Polar lows are more usual in the winter,” Newman said.
Arctic storms such as this one can have a large impact on the sea ice, causing it to melt rapidly through many mechanisms, such as tearing off large swaths of ice and pushing them to warmer sites, churning the ice and making it slushier, or lifting warmer waters from the depths of the Arctic Ocean.
“It seems that this storm has detached a large chunk of ice from the main sea ice pack. This could lead to a more serious decay of the summertime ice cover than would have been the case otherwise, even perhaps leading to a new Arctic sea ice minimum,” said Claire Parkinson, a climate scientist with NASA Goddard. “Decades ago, a storm of the same magnitude would have been less likely to have as large an impact on the sea ice, because at that time the ice cover was thicker and more expansive.”
Aqua passes over the poles many times a day, and the MODIS Rapid Response System stitches together images from throughout each day to generate a daily mosaic view of the Arctic. This technique creates the diagonal lines that give the image its "pie slice" appearance.
An unusually large, long-lasting, and powerful cyclone was churning over the Arctic in early August 2012. Two smaller systems merged on August 5 to form the storm, which at the time occupied much of the Beaufort-Chukchi Sea and Canadian Basin. On average, Arctic cyclones last about 40 hours; as of August 9, 2012, this storm had lasted more than five days.
The Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP captured this view of the storm on August 7, 2012. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Aqua captured a natural-color image of the storm as well.
Arctic cyclones are more common during the summer than winter; however, summer cyclones tend to be weaker than the storms that batter the region during the winter. This cyclone’s central sea level pressure reached about 964 millibars on August 6, 2012—a number more typical of a winter cyclone. That pressure puts it within the lowest 3 percent of all minimum daily sea level pressures recorded north of 70 degrees latitude, noted Stephen Vavrus, an atmospheric scientist based at the University of Wisconsin.
The number of cyclones affecting the Arctic appears to be increasing. According to a study of long-term Arctic cyclone trends authored by a team led by John Walsh and Xiangdong Zhang of the University of Alaska Fairbanks, the number and intensity of Arctic cyclones has increased during the second half of the twentieth century, particularly during the summer.
The cause of the increase is an open question, but climate change may be affecting Arctic cyclones. One study published in Atmospheric and Oceanic Science Letters, concluded that the total number of exratropical cyclones in the Northern Hemisphere would decline as the climate changed, but that the Arctic Ocean and adjacent areas would see slightly more and stronger summer storms.
One way climate change may affect Arctic cyclones is by changing the sea ice and ocean temperature. Climate change has caused sea ice to retreat markedly in recent decades and has also warmed Arctic Ocean temperatures. Such changes may be providing more energy and moisture to support cyclone development and persistence, Zhang explained.
However, scientists who study extratropical storms emphasize that pinning down how exactly climate change is affecting the size, frequency, or tracks of Arctic storms remains an important but unresolved question. “This past week’s storm was exceptional, and the occurrence of Arctic storms of extreme intensity is a topic deserving closer investigation,” noted Walsh. “With reduced ice cover and warmer sea surfaces, the occurrence of more intense storms is certainly a plausible scenario. The limitation at present is the small sample size of exceptional events, but that may change in the future.”
That last bit is the reason I'm hesitant calling this the Great Arctic Cyclone of 2012, or Arcticane, or some such. What if we see a similar cyclone in 2013 or 2014? We'll run out of names.
Mind you, I don't want to downplay the importance and magnitude of this storm, it's by far the biggest thing I have seen in the Arctic since I started the blog, but to me this whole event isn't about the storm itself, but about a possible new regime - a new aspect of the new abnormal - with big summer storms in the middle of the Arctic. Or who knows maybe next time a bit closer to the coast. Because if I was had one wrong apprehension, it was that this storm was going to do major coastal damage. That's to say, I haven't seen it mentioned anywhere yet. Maybe more reports will start to trickle in now that NASA has given it some attention.
I'll be less reticent if we see another Arctic summer storm of this magnitude in the near future.
Time to do another round of sea ice extent and area graphs. The NSIDC daily SIE graph has started to show the effects of the storm. The reason it's late to the party is that it uses a 5 day average: Luckily the DMI trend line has gone back up a bit, because it was about to break the minimum SIE record, and that would've been much, much too early:
IJIS SIE had a decent drop of 75K and is still lowest, after it took first position for the first time this melting season:
Cryosphere Today however had that big drop I anticipated the last couple of days (137 square kilometres) and is getting awfully close to the records of 2007 and 2011, a couple of weeks earlier:
Maybe one more century break, and then it will slow down again. But just 300K needed to break the record. It's amazing to see this happening...
Have at it. There will be a new ASI update tomorrow.