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The second graph within a few days where the pen is writing its line on previously untouched areas...
But cut some slack to this poor clapped out analyst and his poor clapped out laptop. Weep, sniffle, reach for handkerchief.
Will the attached do? ('cos it's all you're getting)The graphs are a bit hard to interpret. Is the software smart enough to put a vertical line between the averages and the last three years?No, but maybe I am
Hehehe...You see what my problem was then.
The graphs are a bit hard to interpret. Is the software smart enough to put a vertical line between the averages and the last three years?No, but maybe I am
Bering Sea - now a maritime sea, (that sometimes has a bit of ice in it)
Central Arctic - still an ice desert, (that sometimes has a bit of open water in it)
PERCENTAGES OF OPEN WATER IN THE ARCTIC
I started with one figure - the calendar year. After including all the comments - too many figures
I'll add one to three to get four and suggest going by celestial days, equinoxes and solstices, you'd still get a winter number after december solstice. If you go by two please do it by equinoxes so there's a physical reason to it, there's probably more use to such an index that takes in account the available sunlight. You could also calculate it for only the period when it's dark or wholly lighted say... Above 75N?
I'd rather see two (or three) numbers. One calculated from the beginning of September to the end of March and one from the end of March to the beginning of September (and your current calculation or a variation with the year starting end of March).
(I think the Winter number would be the real Atlantification number.)
The intention was not to create a measure that would replace all others as in Douglas Adams' "42" but to create a measure that gives a better idea of progress in the conversion of the Arctic Ocean from an ice desert to a maritime open water sea over the last 40 years. The climate works on an annual basis, so a measure for the whole year is needed. I am doing a write up on my thoughts on why such a measure is needed, but decided to chuck the results into the arena to see the reaction. Already I am having a think about reactions received so far..
...
I don't care to predict the end of Summer Ice, since I don't think anyone has any real handle on that, but I say that when the Summer Ice goes the Winter Ice will soon, if not immediately, follow.
The collapse of the Arctic cell and Atlantification will feed each other to end it.
P.S. I am only talking about the CAB. Ice near the continents might keep showing up for decades.
I cannot say that I agree. Why would the ice in the center of the ocean make that much more difference than the ice near shore? The ice will retreat slowly (sometimes more rapidly) towards land. I would expect the effects of this to be roughly proportion to the amount of ice present. Why would the loss of 80% of the ice make that much more difference than 60%?
Good arguments behind that happening. It would be a natural follow-on from a point I made earlier. Once the enthalpy in the Arctic builds up to a sufficiently high level we could easily see major changes in heat transport that will rapidly flip the system into an entirely new state.[Moved from the 2018 area & extent data thread]
Earlier this summer I posted four scenarios for extent loss:
https://forum.arctic-sea-ice.net/index.php/topic,2057.msg158764.html#msg158764
I think it will be some variant of scenario 4, except I wouldn't know which year. I think "the end" will come suddenly, and I don't think anyone has a handle on when that end will happen.
Basically, I expect the Arctic Cell collapsing and the CAB becoming part of the Atlantic to happen at the same time -- I just don't know the time.
in this thread i agree 100%, just not in the "year round thread"
5 years are still pessimistic (considering we don't WANT to see a BOE any time soon) but as you say, the possibility for a sudden death of summer sea-ice cannot be entirely discarded.
Good arguments behind that happening. It would be a natural follow-on from a point I made earlier. Once the enthalpy in the Arctic builds up to a sufficiently high level we could easily see major changes in heat transport that will rapidly flip the system into an entirely new state.[Moved from the 2018 area & extent data thread]
Earlier this summer I posted four scenarios for extent loss:
https://forum.arctic-sea-ice.net/index.php/topic,2057.msg158764.html#msg158764
I think it will be some variant of scenario 4, except I wouldn't know which year. I think "the end" will come suddenly, and I don't think anyone has a handle on when that end will happen.
Basically, I expect the Arctic Cell collapsing and the CAB becoming part of the Atlantic to happen at the same time -- I just don't know the time.
[Moved from the 2018 area & extent data thread]
Earlier this summer I posted four scenarios for extent loss:
https://forum.arctic-sea-ice.net/index.php/topic,2057.msg158764.html#msg158764
Absent massive intervention, the only argument right now is how soon that will take place.
A BOE requires a sufficiently large heat budget combined with a rate of transport (into and out of the Arctic) that exceeds the ability of local conditions to maintain temperatures that overwhelm the ice.
if you mean "could happen any time" together with "year round" it's a clear now, can't happen and this is physics, calculating the energy needed to melt all the ice and keep the arctic ice-free in winter is simply not there and can come from nowhere in such a short time that the terms "imminent" or "could happen any time" are valiid and quite far from it.All the energy is right there. It might not be within snorkeling distance, but it is within SCUBA diving distance of the ice.
As to the year-round BOE, IMHO it will take a long time after the first September BOE, decades or centuries, even if we continue the BAU trajectory (which we probably won't due to collapse, but that's for a different thread).
A term can't help how people use it so preferably we just tell people their use is incorrect? With one thread per melt season a bit of education might work?I agree. GAC has been abused here this season (though the last few days may be an exception - not my area really), but it's still a useful and meaningful term when used properly.
IIRC, the Hudson Bay is fully mixed and brackish at all depths whereas the Arctic Ocean has a cold fresh layer about 100 to 300 meters thick (dunno specifically, haven't read about its oceanography in detail recently) with a relatively warm (4 to 6C ish) salty layer below that. The idea is that the warm salty layer is mixed with the fresh layer by large storms on an open sea Arctic, although I would think the cold layer is too thick for that?
The Hudson Bay experiences a BBE every year and continues to freeze reliably in the dead of winter. Explain to me the mechanism that will prevent temperatures from plunging below the freezing temperature of sea water in the long polar night.
Don't misunderstand me. I am not saying no such mechanism exists. I am just saying I don't know what it would be.
In large parts of the Arctic Ocean, the top layer (about 50 m (160 ft)) is of lower salinity and lower temperature than the rest. It remains relatively stable, because the salinity effect on density is bigger than the temperature effect.
a) year round will take a long time (intentionally don't name my idea of how long)
b) is certainly NOT IMMINENT ?
Toss out the imminent part. I say that when you get a BOE in mid-August you'll have BOE year round. (Not sure about it if the BOE is at the very end of what is currently the melt season.) All you need are long fetches to roll the water.
The Hudson Bay experiences a BBE every year and continues to freeze reliably in the dead of winter. Explain to me the mechanism that will prevent temperatures from plunging below the freezing temperature of sea water in the long polar night.
Don't misunderstand me. I am not saying no such mechanism exists. I am just saying I don't know what it would be.
a) year round will take a long time (intentionally don't name my idea of how long)
b) is certainly NOT IMMINENT ?
the long term change in ocean chemistry. Changes in saline ratios, oxygen depletion, higher water temperatures and species migration will have much bigger negative feed backs.
It would be interesting to see more about effects of seasonally ice-free conditions a few thousand years ago, during the early-mid Holocene. This has happened before, it would be nice to know what to expect.
Possibly depends whether you expect serious consequences from a BOE that was just due to natural variability?
I don't expect "serious consequences" from a BOE per se, given that we've defined a BOE as just crossing some arbitrary threshold (1 million km2 extent or 1 thousand km3 volume). Going from 1.1 to 0.9 in either case will be small in effect, compared to the much larger change that has already happened. In fact, I think the whole concept of "eek, a BOE!" is misplaced. What matters is the long-term decline. But people want excitement and drama...
Is there available a graph of the decadal averages for the north of 80 temperature? I'm interested in seeing how much the winter temperatures have increased.
The Lincoln Sea and thereabouts still looks a mess. This via Aqua yesterday:
...
So, our two values - end of season maximum volume, and annual volume loss - are on intersecting trajectories. I don't think ice loss is going to change radically. However, increasing ocean heat and related knock-on positive feedbacks I think will increasingly erode the numbers we see for our annual maximum, and may have been key factors we hadn't previously understood, as until the last couple years, we've been far more focused on what happens in summer.
I will start expecting it imminently when the winter max volume drops under 20,000KM3. When we hit that threshold, I think we will have a 1 in 10 chance that year of a BOE with relatively normal melt. When the max drops below 19,000KM3, I think it will rise to a 1 in 4 chance. At 18,000KM3 I think it will be 1 in 2.
The one consideration that you are ignoring is that per the research that I reference in Reply #5, the relatively freshwater layer immediately above the deeper warm layer of water, is unstable. So it is not that the deeper and denser warm water will magically float up through less dense cooler water, but rather that the upper cooler/fresher lay may well some day flow laterally away (into the North Atlantic) which would then leave the warm water closer to the surface.
If the deep water flow from the FRAM slowed dramatically it would have catastrophically serious consequences for the AMOC.
DMI 80N continues to drop rapidly.
I don't see how you can say anything about how DMI 80N is doing at the moment, and certainly not that it is dropping rapidly. There is a slight indication that the Winter Cold will be somewhat delayed once again, but it is way too soon to say so....and we will see how much bottom melt continues with the help of some stirring and mixing...
It is to be hoped elsewhere is very close to the bridgeQuotenow at 72.863807° N 149.126623° EQuoteAt 72°N, there are only 34 km per degree of longitude, so many of those decimals are superfluous. The 6th decimal place is roughly 3.4 cm vs 11 cm in the latitude direction.That is where the ship's bridge is (more specifically, where the GPS instrument is). The rest of the ship is elsewhere (i.e., at different decimal places). [or so I learned from an old Coast Guard sailor]
From the data thread...That would be a fine analysis if you ignored the Battle of the Bulge on the Atlantic Front.
Battle of the Bulge ... I like it.
Sorry, I shouldn't have started this in this thread, it's veering into analysis that goes better in the "melt season" thread.
My fault, but let's take it over there.
JAXA ARCTIC EXTENT 4,904,571 km2（August 24, 2018）
[...snip...]
Resulting minimum from average remaining melt is 4.30 million km2.
JAXA has been staying persistently within the range of 4.2 to 4.3 million km2 for some time now.
The "story" of this season seems to be that it's been basically a typical 2010s year, except that Hudson and Baffin Bays took longer than usual to melt out -- so in June and July we had first anomalously slow extent loss, then anomalously fast. But then we got back on the usual track and now it's just marching along as usual.
Of course, having posted this, tomorrow will probably see either a century break or a freak uptick in extent...
My assumption was that you had to be very cold to get ice to form despite convective overturning The heat lost to the atmosphere has to be greater than the heat input by convection. Once the ice has formed, then the water that forms the ice becomes less saline, bouyant, and stays frozen, relying on conduction for heat transfer rather than convection. That means that its easier to form ice with no surface mixing (still conditions) and where the depth of convection is small (close to land)
(5) Eventually...
But the northernmost part of Greenland and Ellesmere Island do come closer to the -11 or so required to freeze sea water (as I understand it), although presumably no sea ice will form on land.
GFS 2 meter air temperature from 12:00 zulu today:
-11 ? I think that is way off. Around-2 is about right.
"NVM -- I gather that the planet is going to attempt to get rid of heat faster as it gets warmer, all other things being equal (which they aren't)."
Theory says so, and a solid dry planet would probably cool down pretty fast. On Earth, in practise this leads to more water vapor getting higher up in the atmosphere thus keeping the temperatures higher on the surface. Taking atmosphere in account, earth radiates more when hotter, we just don't notice it easily here on the ground. Please check this also from elsewhere, it's been a while when I last had to write this down, and may have mixed up some words.
You could also take the view that heat out varies with 4th power of temperature and this is a strong negative feedback that dominates the system and tends to prevent run away situations.
Please explain. I'd say justify too, but I think an explanation would cover that.
(This could explain why we are not Pluto or Venus, but I don't understand it.)
The Stefan-Boltzmann law for black body radiation says that the amount of energy radiated from a black body varies with the 4th power of the surface temperature of the body. If you want to go full Venus, you'll need to add energy at a rate strong enough to dominate this effect, see: https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law
Edit: Thank you Ned for correcting my error.
You could also take the view that heat out varies with 4th power of temperature and this is a strong negative feedback that dominates the system and tends to prevent run away situations.
