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navegante

Do you mention the sudden finish for how thin the ice is at places? CAA, ESS of course, but also much of the periphery at the pacific side...

Robert S

I've never been completely convinced by the PIOMAS volume loss associated with 2012's GAC. It was such a dramatic compaction event that it may have pushed the model outside of its range of accuracy. On the other hand, the extent loss truly was dramatic.

Whether or not 2019 breaks 2012's record, it will be close enough, and looks like a function of the "new normal", where-as 2012 was a unique event. That in itself is reasonably scary.

Looks like there may be some ice export down the east coast of Greenland over the next week. Winds have been keeping that area reasonably compact, so decompaction in this area will impact the extent numbers, although also dooming the exported ice.

Doc Snow

As of 8/8, 2012 is opening up a lead... no pun intended, of course. Another straw in the wind that we won't see a new record this year, though of course nothing is "settled" yet.

DavidR

Well the GAC is over and the extent difference is only about 200K above 2012. PIOMAS becomes less accurate as the ice gets thinner so the difference now with 2012 is probably within the margin of error. It has been a hot summer in the Arctic particularly above 80N which suggests plenty of capacity for late melt.

A couple of years ago a suggested formula for Area and Volume was posted on the forum.
Area = 1.282(Volume^0.5136).
This formula predicts an increased decline in Area once volume drops below 5K km^3 as occurred in 2012 and a precipitous decline when it drops below 3K. It will be interesting to see if the same process occurs this year.

James S.

DavidR, can you provide the source of that surface area-to-volume equation?

Thanks!

Jim

Doc Snow

"...the GAC is over and the extent difference is only about 200K above 2012."

Yeah, in fact as of yesterday (8/11) JAXA had it at 110K. And it's early for this last phase of things, but the slope of the decline so far looks about the same as that of 2012 post-GAC.

So maybe it's more of a horse race than I thought it might be last week. The Arctic weather gods still have lots of scope for action. And if I'm reading the weather outlook right, said gods want to keep the ice melting rapidly for another few days at least.

Robert S

The plume of Siberian wildfire smoke being sucked out across the ice is truly impressive today. Lots of heat with it, too. Meanwhile the Northwest Passage is within days of opening unless there's major ice movement south. We could have close to a month with both the Northwest and Northeast passages open. Circumnavigation opportunity if anyone is positioned...

javimozo

Where can we see the Siberian smoke plume, Robert S? Could you please post a link?

Robert S

javimozo: See for instance https://worldview.earthdata.nasa.gov - set the view to arctic and, depending on the time of day, step back a day for a full view

Doc Snow

2012-2019 gap still at 110K, per JAXA. More and more interesting.

The Arctic weather outlook remains generally pretty warm. And am I right in thinking that the weather patterns have been favoring ice export via Fram? (That's what I think I'm seeing on the Reanalyzer.)

wndchaser

Doc,

You ask a great question. I too have been watching the forecasts and it sure seems like there are favourable conditions for ice export. I don't dig far enough into this hole. Maybe someone else here does.

JB

javimozo

Thank you, Robert S.

AnotherJourneybyTrain

I've never heard it explained as to why <1M km^2 defines "a sea-ice free Arctic".

Why then should anyone expect that that particular number will ever be breached?

On the forum a few days ago someone put up a formula relating Arctic Sea-Ice-Volume to Arctic Sea-Ice-Area... basically it went down at an increasing rate once Volume went below 5, and it went down precipitously if Volume went below 3. (Obviously I can't find the thread at this point in time or I would have left a link to it.)

Doc Snow

The sub-1M km2 standard is essentially arbitrary. The idea is that at that level, the Arctic basin would be essectially bare, with just some bits floating round and/or landfast in sheltered locations.

Why should it be breached? I'm not sure I understand the full context of your question, but basically because of Fudd's Law: "If you push something hard enough, it will fall over."

Fudd's is obviously non-quantitative, in contrast to actual scientific laws, but given that the energy required to melt all the Arctic ice is finite; that annual minima are only about 20% the volume they used to be; and that we may confidently expect both air and sea temperatures to keep climbing (as well as GHG radiative forcing) for the near future; we appear to be in a Fudd's-type situation. Energy available for melt is going to keep increasing, while ice volume keeps decreasing, until the system 'falls over'.

The analogy fails a bit at that point, because seasonal refreeze won't stop then--though it does appear that a perenially ice-free Arctic Ocean is in fact a possibility:

"Fossil records verify that during the Eocene period, 50 to 55 million years ago, there was no permanent polar ice on Ellesmere Island. Instead, a lush rainforest dominated by dawn redwood trees and tropical vegetation flourished near Strathcona Fiord. This fertile ecosystem survived despite being shrouded in darkness for six months of the year. The forest thrived on rich flood plains that teemed with a diverse variety of life, including alligators, tapir, giant tortoises, primates, snakes, lizards and the hippo-like Coryphodon, all nourished by the abundant rainfall and mild climate."

http://arcticjournal.ca/uncategorized/fossils-at-risk/

Doc Snow

As of 8/18, 2012 has opened up a bit more 'space', with the difference from this year up to ~250k. (Interestingly, that 2012 value for August 18th--4.31 million km2--is also pretty close to the 2010s average for the minimum--4.39 million km2). I expect 2019 to hit that mark later this week, barring sudden changes in conditions.

It looks to me as if the chances now favor a 2nd-lowest-ever minimum in about 3 weeks.

AnotherJourneybyTrain

The latest update from NSIDC says that the average sea ice thickness for that date is about half what it was in the 80s.

javimozo

Maybe I'm just crying wolf again, in which case I do apologise, but that's the forecast in 2 days time:

https://www.tropicaltidbits.com/analysis/models/ecmwf/2019082100/ecmwf_z500_mslp_nhem_3.png

and in 3 days time:

https://www.tropicaltidbits.com/analysis/models/ecmwf/2019082100/ecmwf_z500_mslp_nhem_4.png

It could be worthy to keep an eye on it.

Doc Snow

As of 8/23, the separation with 2012 has increased to nearly half a million square kilometers, so you'd have to say that 2019 is fading badly in horse race terms. Good for the Arctic and planetary environment, less good for humanity's awakening, perhaps.

Interestingly, despite what would appear to my not-very-acute eye to be pretty favorable conditions for melting, even a second-place finish is now somewhat in doubt, if you go by the current decline. Project the 2019 graph line forward, make your best guess at when the minimum turns out to be--conveniently, 2016 (early) and 2007 (late) more or less bracket the range--and you likely end up with 2019 somewhere in the vicinity of those two years, which is to say around the 4 million mark.

It took a little longer than I expected, but 2019 has indeed roughly equaled the minimum of the 2010s average now--more precisely, 2019 is at 4.41k, while the 2010's average bottoms out at 4.4 for the dates 9/12 and 9/13--so a finish that's well below the decadal average is in the bag.

I suppose it would be well to mention once again, for folks who are jumping in now, that this is all per the JAXA extent data, which may be found here:

https://ads.nipr.ac.jp/vishop/#/extent/&time=2019-08-22%2000:00:00

(Hope that link holds--otherwise, JAXA extent is in the excellent collection of 'house graphs' which Neven curates, accessible via the "Arctic Sea Ice Graphs" link in the upper right of this very page.)

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