Sea ice extent measures the area of the sea where there is at least some minimum concentration of sea ice, typically 15% coverage. Sea ice area is a measure of the actual area covered by the sea ice. Because extent counts grid cells which only have partial coverage, extent will always be larger than area, but when things are in the deep freeze and there is little breakage at the edges and even in the interior of the ice pack, they will approach each other. Thus the difference/ratio of the two is a measure of compactness
Everybunny who owns the keys to a blog has been showing Winipus' scary global sea ice extent graph, which if anything as iconic of the mess that we are in of our own doing as any hockey stick.
The dive at the end indicates the continuing breakup of the Antarctic ice pack while growth of the ice in the Arctic is historically low. However Winipus has now produced a sea ice area graph which is beyond scary
In previous years the November peak is well above the June one. Not this year.
Sea ice is crashing. The clause is probably human driven climate change imposed on natural variability, but the reticence of scientists can dangerously go the more study is needed route too easily. Mark Serreze from the National Snow and Ice Data Center has gone the full Al Gore is an alarmist route
The combined number, while easy to derive from our online posted data, is not useful as an analysis tool or indicator of climate trends. Looking at each region's ice extent trends and its processes separately provides more insight into how and why ice extent is changing. Sea ice in the Arctic is governed by somewhat different processes than the sea ice around Antarctica, and the very different geography of the two poles plays a large role. Sea ice in the Arctic exists in a small ocean surrounded by land masses, with greater input of dust, aerosols, and soot than in the Southern Hemisphere. Sea ice in the Southern Hemisphere fringes an ice-covered continent, Antarctica, surrounded by open oceans. While both regions are affected by air, wind, and ocean, the systems and their patterns are inherently very different. Moreover, at any point in time, the two poles are in opposite seasons, and so a combined number would conflate summer and winter trends, or spring and autumn trends, for the two regions.The detailed mechanisms may differ, but the cause is the same.
It's a wild-looking departure, but I'm not convinced it is anything more profound than a view-byte. Serreze (check yr spelz) isn't the only one with some caution about the numbers. Take from New Scientist:
ReplyDeleteThis is a weather event... In fact, it’s two weather events
https://www.newscientist.com/article/2113493-global-sea-ice-has-reached-a-record-low-should-we-be-worried/
This comment has been removed by the author.
ReplyDeleteMark Serreze might want to think a little harder about the big picture.
ReplyDeleteThese camel-hump plots and similar have for a number of years been disturbing to watch, as the fat has melted from the bactrian's back, but this year's sudden switch to dromedary is a real concern. Yes, the aggregate covers a wide array of physcial cofactors that impinge on the totals for each year, but there is nevertheless a relatively tight bounding confidence interval. And this year that CI has been left far behind in the rear view mirror, in a way that hindsight may well recognise as the demarcation of a tipping point...
And Serreze wants to pick up his fiddle?
Oops.
Barry, I'm not quite as sanguine as you, for the reason that I touched on above. The 2016 trajectory is a significant excursion from the historic record and yes, weather, but for weather to have such an impact on deviation from the central tendency there has to be something underpinning.
ReplyDeleteThat something is a climatic boot, and the target is the biosphere's arse.
Published CV of 'barry;.
ReplyDelete"Lifelong interest in science as a layman, work in the arts, bad at math, underqualified in every way to comment but still let myself converse. On the plus side I'm very rational. On the down side, this actually counts for something on science blogs (it should be de rigeur)."
That's all you need to know about barry. Besides the fact that he thinks a New Scientist article is a credible technical source, specifically one so lave that asks 'Should we be worried?'.
The last few days have seen a sharp recovery in the Arctic, and projected weather promises more of the same. Still low, but the Apocalypse is still a decade or three out: http://forum.arctic-sea-ice.net/index.php?topic=230.3400#msg94640
ReplyDeleteOdd weather is an odd culprit since that just sweeps the problem into a different corner. How is odd weather that produces a 6.9 sigma result better than the 6.9 sigma result? The ice was never going to melt itself.
ReplyDeleteThe Guardian has an article today about the Arctic warmth and the lack of sea-ice:
ReplyDelete'Extraordinarily hot' Arctic temperatures alarm scientists
At the top of the article is a photo showing sea-ice with prominent melt ponds on the surface. I think it's important to understand that the passive microwave measurements of sea-ice calculate area based on the average emissions from entire pixels of received energy. Since melt ponds emit microwave energy at the same level as open water, this averaging process results in considering melt ponds as open water. There may still be considerable ice below the individual melt ponds, (appearing as light blue in the photo), thus I think using the "area" value will tend to overstate the actual melt. Calculations of overall sea-ice "volume" may also be overstated, if they are based on the calculated "area" multiplied by some thickness. My personal preference is that the calculated value for "extent" is a more reasonable measure of the overall situation. That said, both measures look astonishing this month.
One should produce a graph of the global sea ice albedo which has a very physical meaning that is beyond the "different seasons blah blah" counterpoints. I bet that global measure must have taken the escape route as well....
ReplyDeleteI think the conclusion here is inescapable, even for the most die-hard denier. I think even Mr. Trump must have been filled in with the details already, not that is will change his stated policies. It's not as if this was not predict and expected. And here it is.
ReplyDeleteThe oscillation overthruster!
They just think that somebody else will fix it for them, in the future!
Of course this is a weather event, just as the 2012 record minimum was and IIRC a couple of oversize unseasonable cyclones over the same period. Each comes to an end, but the tendency will be for them to come more frequently and become greater in magnitude and/or duration as Arctic amplification proceeds. Unfortunately it seems there's no way to develop a single metric for such a diversity of events.
ReplyDeleteIMO people should lose those global sea ice graphs. They only serve to make understanding more difficult. By all means put up the north and south ones side by side, though.
All of that said, the Arctic sea ice trend is a bit of a distraction. Watch the permafrost.
It is not a weather event.
ReplyDeleteAs to the permafrost thing, after the rainstorm couple of weeks ago over Svalbard, part of Longyearbyen has become permanently uninhabitable since the muds just slide around. 256 people are homeless and have had to go to Norway proper.
There are polar bear cubs rotting.
Bernard J,
ReplyDeleteOf course the globe is warming and the sea ice is shrinking, and will continue to do so.
What I see with this story is some hay being made out of a big diversion on a graph. It's political hay, and that's ok as it goes. But this has been pitched in some friendly quarters as some kind of seismic shift in the downward trajectory of global sea ice that *may be* a permanent new regime. That is NOT a scientific conclusion. This is where responsible concern turns into the kind of alarmism that the contrarians are justified in complaining about.
Having made this point on the previous thread, I was taken to task for my lack of substance on the matter. But here and at Tamino's there is no statistical analysis, and certainly no physical underpinning to back up a regime shift. We already know that sea ice is shrinking and will continue to do so. These short-lived anomalies should be called for what they are, or else wolf gets cried too often.
Maybe my balance on this is too 'sanguine'. It just irks me when we hold ourselves to a lower standard than we do the contrarians, and make foolish claims based on short-term excursions. Yes, the wiggle is extraordinary. But it's just a visual, and I see a lot of people whipping that up into something with precisely the lack of substance I was scolded for not buttressing a more moderate view (remedied somewhat, I hope, on the previous thread).
Maybe it's better to herald any old wild looking observation such as above, to try and drum up some passion. Maybe this graph-byte fits with Schneider's notion of drumming up scary stories (and sewing them with truth). I think it oversteps. The truth is enough.
Eric, it's not melt ponds. If you look at the sea ice maps (uni bremen) the edge of the ice is sharp. There is no ice in the Bering Strait or Hudson's Bay. It is totally alarming
ReplyDeletehttps://seaice.uni-bremen.de/amsr2/Arctic_AMSR2_nic.png
Some other views on the graph:
ReplyDeletehttps://www.wunderground.com/blog/JeffMasters/crazy-cryosphere-record-low-sea-ice-an-overheated-arctic-and-a-snow
http://www.theverge.com/2016/11/17/13667630/global-sea-ice-concentration-graph-science-twitter
Even Snopes has become involved.
We'll see how the record low November conditions the Arctic sea ice for Winter and the following melt season. Regulars at Neven's sea ice blog will be watching multiyear ice and PIOMAS (ice thickness).
There's little multiyear sea ice in the Antarctic, and much less likely for the recent low concentration over Winter to have a 'memory' for following seasons. Antarctic sea ice melts nearly out in Summer.
There is no 'we' barry, and you are only the designated spokesperson for 'you'. Your CV speaks for itself. Here is how I quickly and easily identify an fascist with authoritarian tendencies and Dunning Kruger affliction. They speak in terms of 'we' and 'us' and not for themselves, and are not capable of performing any original work.
ReplyDeleteThat's you, barry. You are in good company, just not here.
Eli, I don't disagree that this year's sea-ice is different, but my point was about the "extent" graph vs the "area" graph. They have a similar appearance, except that the distance between the NH minimum and zero is much less with the "area" graphics, which I think somewhat overstates the seriousness of the situation. As for the sea-ice in Hudson Bay, here's some other historical data from 2012, the year with the record lowest extent:
ReplyDeleteftp://polar.ncep.noaa.gov/pub/ice/nh/2012/nh12.20121122.gif
How about 2007, which has some sea-ice in Hudson Bay, but more open water poleward of the Bering Strait?
ftp://polar.ncep.noaa.gov/pub/ice/nh/2007/nh12.20071122.gif
The sea ice was considerably thicker back then Eric.
ReplyDeleteLying Rabett. Such a nasty man. Sea ice is expanding everywhere. Sad. Sorry losers and haters. Your big hoax isn't fooling anyone.
ReplyDeletehttps://s-media-cache-ak0.pinimg.com/originals/3a/2b/eb/3a2bebb681979bd1b7d5f949fee4b2a2.jpg
ReplyDeleteD. Trump has given us arguably the best smiley face ever used with a post, indicating the completely laughable nature of said post...
ReplyDeleteCruel satire will thrive in the very near future, in the new old Amurka.
ReplyDeleteBill Maher came up with that orangutan photo. He pointed out the similarity in color of the orangutan and Trump, and said he would donate $5 million to charity ("Hair Club for Men") if Trump could prove he was not the son of that orangutan. Trump actually came up with his birth certificate and when Maher refused to pay the $5 million, Trump sued. Read more: http://www.motherjones.com/politics/2016/09/trump-files-donald-son-orangutan
ReplyDeleteThe Holocene began when the Younger Dryas (YD) mini ice age ended in only three years. See "The Two-Mile Time Machine" by Richard Alley. That happened when the sea ice, which had spread as far south as Ireland during the YD, retreated into the Arctic Ocean. The abrupt warming was caused by the change in global albedo, which upset the energy balance at the top of the atmosphere. The only way the balance could be restored was for enough new cloud cover to form, replacing the albedo lost when the ice disappeared.
ReplyDeleteWhen the summer Arctic sea ice disappears, the ice will not reform in the winter. You can see how difficult it is finding it to reform from a base of 4,000 million sq. km now. From a base of zero it will hardly reform at all, and the following summer there will be less ice and more warming of the exposed Arctic Ocean sea surface, which will be heated by the sun continuously for almost six months.
At the end of the YD and start of the Holocene the temperature in Greenland rose by 20 C. How long will the Greenland ice sheet last if that happens again?
That's a great story Alistair but having studied the Younger Dryas extensively up to our current understanding you'll just have to forgive me for not buying into whatever it is you are trying to say.
ReplyDelete@8c7793...
ReplyDeleteMaybe you're not buying what Alastair has to say-- but prudent policy is not based just on future events we're confident about. We should be worrying about even small risks of catastrophic, irreversible outcomes, especially because (see Lewandowski) a very large proportion of the total climate risk we're running lies in the more extreme scenarios. Even when weighted for their comparatively low probability, the associated costs make up a large part of the total risk we face. Insurers are worried, and they should be.
He got it kind of right, but his magnitudes are way off and he's ignoring a whole suite of oceanic forcings and regional effects. Maybe he's just not reading the same paleoproxy papers that I'm reading.
ReplyDeleteHere's how I do it when I have the time. I go to google scholar and type in "Younger Dryas" and then sort by date.
Hi 8c7793...,
ReplyDeleteThanks for commenting on my post. I am not really surprised you did not buy into it if you are following the current ideas. I'm proposing a new scheme. You will be aware that there are two proposals - outflow from the pro-glacial Lake Agassiz and a meteorite impact. Neither of these can explain the abrupt warmings. What I am proposing it is the positive feedback sea ice-albedo effect that produces the abrupt changes, both warming and cooling. Moreover, it is not the THC which causes the sea ice, It is the sea ice which switches the THC.
It is explained better here: https://www.researchgate.net/publication/301540905_A_Paradigm_shift_to_an_Old_Scheme_for_Outgoing_Longwave_Radiation
PS
I've been interested in the Younger Dryas since before Google Scholar was created, and I tried a search for Younger Dryas on Google Scholar and got 44,000 hits,2,000 this year so far! I haven't read them all yet!
Sorry, wrong poster. This is the correct one: https://www.researchgate.net/publication/304897458_A_New_Radiation_Scheme_to_Explain_Rapid_Climate_Change
ReplyDeleteEli might find the other of interest.
https://www.youtube.com/embed/wqYpTTDF7dY
ReplyDeleteHmmm, looks familiar -- maybe the Arctic is toast?
After 5 and a half months of extraordinary departure, global sea ice area is now no longer at record lows.
ReplyDeletehttps://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/grf/nsidc_global_area_byyear_b.png
Wondered how long it would take for the squiggly line to rejoin the lower edge of the pack.
This has not occurred yet for the extent metric.
Be interesting to see down the road if this was an anomalous departure (coincidence of N/S low anomalies), or if some kind of corner has been turned.