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Messages - JimboOmega

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1
Greenland and Arctic Circle / Where Does The Water Go?
« on: August 10, 2019, 12:05:25 AM »
On the DMI Greenland site, losses are often expressed in terms of Gigatons, which they explain as being equivalent to a cubic kilometer of water.  In a typical year, it seems like ~200 GT might melt, whereas in the worst years like this one, 300 or 400 GT might melt.

This is a tremendous amount , and it's very fresh water, assuming it melts and winds up in the surrounding waters. 300 Gt could cover the entire arctic ocean 2cm deep; or it could cover a million square kilometers 30 cm deep.

Does such a large impulse of fresh water actually impact the surrounding currents and oceans? In years where it's way more than climatology, what weird effects occur? Does the water go somewhere else (for instance, evaporating into the atmosphere)?  On some days, like recently, 10GT are removed in a day, do those pulses have impacts on other things in the cryosphere? Or are they mostly of concern only to the greenland ice sheet itself?

2
Arctic sea ice / Re: The 2018 melting season
« on: July 19, 2018, 09:39:52 PM »
For 2018 the thing that REALLY surprises me is the Bering sea.  The straight never fully froze over, and was open in February. The ice edge was so far back from what it normally is.  Many articles were written even outside of sea ice geek circles about how unusual it was.

But the ice edge has moved back so incredibly slowly in the melting season it's getting close to normal there. What the heck happened?  Where did all that extra insolation go?  Was that heat shuffled off somewhere else (like out?)  I was almost sure all those warm bering sea waters would cause all kinds of melt and it absolutely didn't materialize.

3
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: June 11, 2018, 09:32:57 PM »
Readers that are familiar with my animations know that I mostly enhance contrast somewhat to make the variability better visible. That is not needed here: the apparent sea ice concentration of the land-fast ice in the Laptev is gone to 0% in many places. The added color-coded concentration map will show you that.

Looking in worldview that ice is still there, though it is very blue; its surface has dramatically changed over the last week.

4
Arctic sea ice / When is Radiation Breakeven?
« on: March 26, 2018, 07:55:10 PM »
Assume an area of open ocean, under a clear sky, at the freezing point of the water, with no interaction from the atmosphere, currents, etc.

At what amount of insolation does it breakeven - in the sense of losses to space are the same as inbound solar radiation?

Ideally I'd like some sort of general way to figure out what day of the solar year this occurs at a given latitude.

The motivation for the question is - in the winter, water opening up as Polynya causes the system to (overall) lose more heat to space and leads to more ice forming.  In the summer, the opposite is true, as expanses of open water absorb more sunlight than they lose heat to space. In the spring, like right now, I don't really have any idea.


5
Arctic sea ice / Re: The 2017/2018 freezing season
« on: February 26, 2018, 09:07:29 PM »
The current spike in temps is amazing and unprecedented, but I don't *think* it means that much for the coming melt season. We're only a little bit below last year on extent.  The sun has yet to rise so that excess heat is going to be vented to space.  Looks like the GFS is bringing its forecast of return to normal temps earlier, even with the anomalous open ocean on the northern coast of greenland. Open water there is about as good a thing as we could hope for this time of year in terms of venting heat to space. The warmer it is, the more heat the system loses.

All things considered winter still has time, and moreover, the current (ice) numbers aren't that different than what has come before. Not enough to forecast anything calamitous, yet. If the CAB numbers stay this low through March/Sunrise, I'll be worried, because Albedo will kick in hard at that point.

Hi Subg!

I wonder just how much of the 80N circle will see above freezing temps on tues/weds and how that will play out on the DMI plot?

Over summer the latent heat of fusion keeps temps close to freezing ( due to ongoing melt) but Warm Air Advection passing over the pole whilst it is frozen?

Could we see temps beyond what we see mid summer over those days?

What would the world make of all that once they're made aware of it

Warm area over the pole will only cause it to melt some (assuming the net heat balance is sufficient, which I'm not sure it is - it's still dark and energy is still being lost to space).

It still can't get much above freezing until all the ice is gone.  And honestly, melting the snow on top and then refreezing it as ice... I'm not sure what the impact of that would be, but it might even help with albedo (ice being more reflective than snow iirc).

6
Arctic sea ice / Re: The 2017/2018 freezing season
« on: February 23, 2018, 10:36:54 PM »
This is complete insanity. Above freezing temps forecast across the pole and most of the way across the CAB. It's only a couple days in the future.  And it's not even that far from the current situation with above freezing temps on the Greenland north coast.

If these anomalies keep on like this...  I just don't know. The scary thing is that so far *they have been*. I can't remember the last time I looked at CCI-reanalyzer and it had a nowcast with a < 5  degree C anomaly.

There's a few more weeks before the rising sun will "lock in" these losses, and the arctic will really start to lose its ability to vent heat to space.

CCI-reanalyzer has also kept saying that these anomalies will come down, but they haven't.  Somewhere upthread I recall somebody saying how GFS forecast it would be over by February 20.... That forecast definitely didn't verify.  It's not one warm system or one day of warm temps.  In the DMI graph it looks almost like spring started 70+ days early.

Does anybody think we'll get a real dip (that lasts a week+) back towards the climate average before winter ends? A chance for a last gasp freezeup?

7
Arctic sea ice / Re: The 2017/2018 freezing season
« on: February 22, 2018, 01:37:43 AM »

One could argue that the Bering Sea is somewhat peripheral/ irrelevant also, and furthermore, the recent storms there could well have compressed the ice into the Chukchi- where it is certainly relevant for it to exist in order to prevent early high-arctic melt. That being said, Bering is toast.

The ice is in bad shape for winter, but I don't think it looks like were setting up for a particularly bad early-summer melt event. Especially when you look at the NH Snow Water Equivalent. Which if my memory serves me correctly, was high last year also, and in turn caused ice to linger on the Siberian coast for a surprisingly long time.


That is what I was trying to argue. I thought about comparing to the Sea of Okhotsk. Of course if it . melts earlier, there will be a little more heat (from albedo effects) in the overall system, but compared to CAB heat, it is a way smaller fraction. Yes, the Bering straight is open, but it is narrow and shallow. It *will* make a difference... just not a huge one.

I also couldn't find snowpack numbers, sadly, but figured that they would be more significant.

8
Arctic sea ice / Re: The 2017/2018 freezing season
« on: February 20, 2018, 09:34:37 PM »
[Edit] I will add, all that open water in the Bering also means much early heat uptake from insolation, which in earlier years would get spilled back out by albedo.  None of that now - the only thing stopping it is cloud cover, and even then, that means down-welling longwave radiation will still get picked up by the water rather than deflected by ice.

The Bering will be starting the season with a significant heat surplus, and a net acceleration in heat which can be captured.  I've no idea yet how much of an effect that will have on the ice further north, but I can't think it will be good.

During the winter, open water also loses heat much faster than frozen-over water. . I still think there's time for it to freeze over in normal or colder weather, but that window is closing. I can't really say when it's closed - though it looks like the Bearing Sea has (historically) added ice at times throughout March so it isn't immediate.

I also think Albedo effects on the Bering may not be that significant (for the arctic ocean ice), because of the narrowness and shallowness of the straight limiting the current that can pass through it (compared to the Atlantic side, especially). The Beaufort can open before the straight is fully cleared, so I don't think it's a keystone or anything.

It might impact the weather farther on because of the extra pool of warm water available there, but I can't really say what those impacts would be. It may well be a cloudier summer due to more vapor available.

It is insanely warm there now, and the ice cover is shockingly low, but I feel like the impacts will be muted later in the season.

Though if it stays somewhat open on the Arctic/Beaufort side of the straight... then I'm way more worried. I feel like that would require this insane weather (I mean, 0C+ temps! In February!) to continue for more than a month, constant split PV and all that.

9
Arctic sea ice / Re: The 2017/2018 freezing season
« on: February 16, 2018, 11:34:23 PM »
Couldn't resist this cci-reanalyzer image for Tuesday 20th Feb. Arctic temp anomaly + 6.7 degrees celsius.

But by 26th Feb down to 2 degrees.

It's currently forecasting +6.9C on the 20th with a nowcast of +6...

Kind of crazy how it crashes down to +2 C (which seems so low these days...)

10
Arctic sea ice / Re: The 2017 melting season
« on: July 26, 2017, 11:28:45 PM »
While the past freeze season was one for the record books, we have had anomalously warm polar winters for at least a decade. I would be surprised if this is not the case for the next freeze season.

To me, what happened last year was that the ice opened early in a big way, causing the waters to absorb more heat than they usually would.

Come freezing season, this heat was released as water vapor to the atmosphere, making the air warmer and more moist. This heat and moisture meant that the air was warmer (especially when the cycle was completed by snow coming out).

All that extra snow really slowed down this melting season; it seems like it had a bigger impact in the end the warm air keeping the ice thin.

That all being said the conditions that triggered the 2016 fast opening are not, IMO, magical or impossible to repeat. There will be continued see-sawing, but I think the long term direction is very well established.


11
Arctic sea ice / Re: The 2017 melting season
« on: July 14, 2017, 10:00:08 PM »
...
Anyways a lot of the easy ice of past few days melted in the past 3 so now it may take more work to melt the next sections. ...
Normally, that would be true. But we are going through this "soup" season here, as i call it. All bets are off.
Concur.

Based on the fragmented state of the ice, and how much late, thin FYI is woven through the pack, the melt season is playing out much as I'd imagined.

What remains to be seen is if weather and the break we got from additional snow cover will rescue the pack  from a new low.

I think it possible we might find ourselves in a unique place in September. I think it possible we may still see a new low in area, but may not have one in extent.

One thing I've seen in particular this season is that regardless of how fragmented it is, its durability is heavily influenced by thickness. You can have ice like the Beaufort Gyre (or south Hudson Bay) that sticks along despite constant heat and warm(er) waters. 

Then you have ice that just starts to break apart on its own even mid-pack, which is much thinner... thickness is hard to see from worldview (unlike fragmentation), but it makes a big difference.

12
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: July 05, 2017, 09:05:48 PM »
So we are lowest on both parameters, as of 7/4/2017.

Hopefully this will help end the fantasy that 2017 has a lot of "catching up" to do to have a chance at a record this year. Area, extent, and volume are all at record lows or close to it by all measures I can find. I think the fact that there was no May or June "Cliff" has lead people to miss the fact that the year started way ahead of others - and has posted steady declines.

13
When I look at Nullschool's depiction of the developing CAB cyclone, there's a large volume of precipitation in the forecast. In the areas where it is predicted the surface temp shows up as somewhere between -0.3 and +0.5 degrees. However, there's also a "1000 MB temp" graphic available - and for this system, at least, it consistently shows a core temp for the cyclone several degrees higher than the surface temp.

I've been interpreting the above as implying that the precip will mostly be falling as rain onto wet ice/snow... (and from what little I can tell of the actual effect on the surface this seems quite plausible)

But it just now occurred to me that the forecast SLP in the eye of the cyclone is only 970MB! So my stupid question of the day is...

 - What does the 1000MB temp mean when the SLP is less than 1000MB?
That is a really good question. A 3-D model of such a cyclone would probably help, if someone knows where to find it. Other than that, maybe they are referring to the altitude that 1000 mb would normally be found without a cyclone, that is around 111 meters, though rounded off on their about page. Speaking of, Earth NS has this page https://earth.nullschool.net/about.html which seems to indicate that they are simply using the term as an altitude, but there is an email address on the page for inquiries also.

I think they are probably referring to the altitude at which 1000mb would be found, assuming the atmosphere extended that low (which it does not, in this case). So if the cyclone was over the dead sea, then 1000mb might indeed occur at some point in the atmosphere (even for a cyclone with a 970mb pressure at sea level), and they would expect it to have such a temperature.

14
People in the main thread are talking about cyclones dragging cold air into the arctic.

Where does that air come from? The arctic is the coldest part of the northern hemisphere already... right?

15
Arctic sea ice / Re: The 2017 melting season
« on: June 19, 2017, 10:18:07 PM »
Rather than look at distant forecasts...

I noticed that right now, according to cci-reanalyzer, there's rain falling over a lot of the arctic, including near the pole. Is this a fantasy or known model issue?

16
Another question...

What determines the initial conditions for models like the GFS in the arctic?  Is it driven by the buoys? Satellite measurements? I'm wondering if the input data could be wrong because there are so few reliable stations in the arctic.

17
Arctic sea ice / Re: The 2017 melting season
« on: June 13, 2017, 05:55:07 PM »
Well, I can't wait to see what will happen in these two places. I also have a doubt that the hole will stay, but it looks real on Bremen June 11th and 12th.

The one the "right" of your image is real as per worldview - the ice there is broken into lots of bits and is melting and dispersing and so on.

The one on the left is another glitch, since I don't see any evidence of it on worldview and there's no reason for it to be there.

I do wonder what leads to these deep in the pack "hot spots", especially since the last one - the North Pole one - lasted a couple days too. But absent any other evidence for it existing I have to think it's a Uni Bremen error.  I'd imagine certain atmospheric conditions could cause deep cracks to form into the ice, splitting the pack up, but... not just a big hole in one spot like that.  Perhaps it has to do with satellite tracks and getting marginal sampling of an area.

In other news, here in California, the Tahoe ski resorts picked up more snow over the weekend. This is rare, happening only every 5-10 years. 

18
So I noticed a bunch of areas, like the Hudson, Greenland North Coast, etc, that have cycles where the wind blows the ice away from the coast, creating open water, and then later back towards the coast.

My question... does this have any particular impact on the ice? Does the water it's being blown into warm in a few days in the sun? Does the ice coming back push that water out of the way? Or does a few days of sun not really matter?

19
Arctic sea ice / Re: The 2017 melting season
« on: June 06, 2017, 01:29:38 AM »
Any chance we see an eye of open water form at the poll in a week or so?

None. I'm pretty confident this is noise - you don't see anything on WorldView or any other source. Usually this is melt ponding (not open water)... But it's too cold for that there.

I guess it's possible divergence in the pack opens water there, but that's slower than this.

Let's see what it says tonight... or if we get an unobscured visual pass.

In the meantime I'm really wondering how long it can be so warm on the shores of Hudson Bay (80F/27C forecast tomorrow for Port Nelson.. with rain!) without the ice just off the shore melting or showing any negative impacts. I can't imagine much worse weather for ice...

But then I'm planning on skiing on July the 4th up in Tahoe, so... maybe snow/ice is just immune to warm weather this year?  :)


20
Arctic sea ice / Re: The 2017 melting season
« on: June 03, 2017, 12:20:40 AM »
Here's SAT for next week (but I've read that GFS wildly overestimates temperatures that far out, so there's hope), with most of the Arctic reaching 0 °C or higher:

The GFS (at least as cci-reanalyzer has it) has been wanting to make the whole arctic +0C a week out for a while. I don't know why, but I definitely have seen this before, with a few degrees C of positive anomaly that hasn't materialized.

21
Arctic sea ice / What happened (or didn't) in May?
« on: June 02, 2017, 11:42:32 PM »
So May came, and with volume so much below normal, some people were calling for a cliff.

Instead (as extent goes) we had a pretty unimpressive month, especially compared to last year.

So... what happened - or didn't - in May?  Anybody want to take a shot at explaining it before NSIDC does?

22
Arctic sea ice / Re: The 2017 melting season
« on: June 01, 2017, 08:45:14 PM »
Perfect weather conditions with little clouds on the imagery coming in for today, it is not complete yet, but what is available I have attached. Have to look at all the way forward to June 19th 2016, for a similar situation.

(Edit: Changed image type from PNG to JPG to reduce size, little effects on quality)

Is there any history of this area being open... ever(in the satellite era, anyway)? Along the Greenland North coast, I mean.

I'm not really sure what the implications of it is, so I'm curious if there's anything comparable that's happened.

23
Arctic sea ice / Re: The 2017 melting season
« on: May 25, 2017, 02:37:55 AM »
Anybody else notice it's above freezing in Barrow? And there are melt ponds not just on the snow on land but out on the ice as well. Also the first time I've seen people out walking and riding bicycles (I'm sure not the first time it's happened).

Spring is arriving in the high arctic...

24
In the main thread a lot of people are getting excited about Nares "Export". But Baffin Bay is entirely frozen over. So why is it significant that ice is getting exported into more ice... more than any other Polynya opening up?

25
Arctic sea ice / Re: The 2017 melting season
« on: April 26, 2017, 07:36:52 PM »

I agree with you there - the average temperature is not going to be all that important.  We talk in terms of volume and extent.  Extent, is the least important but the thickness/volume is.  Any tipping point will be due to the loss of thick MYI versus FYI.
I am using some of this in classes, and stressing to my students that using averages is the appropriate method to do so (along with the standard other facors - variation, STD etc.).

My feeling is that thickness matters less than everyone thinks it does, because it is the surface that interacts the most thermodynamically - it is the frozen area that reflects the light, that radiates heat off to space.  Especially right now, it seems things opening up (or not) has more to do with wind creating polynya than the thickness of the relevant ice and its resistance to melting.

Also the modeling behind thickness is a lot more imprecise - from what I've heard - than it is for extent (looking down from space and seeing ice is one thing, knowing how thick it is requires some assumptions).  There are a couple different volume numbers with very contrasting values (last I heard, anyway!)

Last year I heard a lot that a real cliff was coming, that the volume was so bad, we're so much worse off than 2012, etc. This year I'm not (automatically) buying it.

I think that the global climate implications of a the melting season are much more driven by extent than by volume, because that's what (via Albedo) controls how much extra heat would enter the system because of ice (or the lack thereof).

Last time I brought this up I asked people to make predictions based on the volume, IE, when would we see the results of the current volume in extent or other grossly visible things. I'd repeat that challenge again. 

Of course if you want to argue that weather trumps volume and thus you can't make any real predictions beyond a week or two, that's a valid assertion - but of course is contrary to the argument that average temperature matters less than volume.

It's also possible that each year we're getting a thinner pack and this is the year the thinness really does lead to a catastrophic extent/area drop. Do you think it is?  If it's not, how thin would it need to be for it to happen?

26
Arctic sea ice / Re: The 2017 melting season
« on: April 18, 2017, 09:17:04 PM »
If the average temperature is still well below freezing, does it matter about winter anomaly in the short term? Obviously not a good indication for summer or long-term, but freezing is freezing, so does it make a big difference? Yet?

Someone correct me if I'm wrong, but I think it does. The ice can get much colder than the freezing point. I imagine -30C ice would resist the melting season longer than -10C ice. Also I imagine that warmer ice have different physical characteristics as colder ice.

This is true but bear in mind that the energy associated with melting is far greater than the energy associated with heating.  Ice has a specific heat of 2.05kJ/kg*degree, while to melt it requires 333 kJ/kg

So to melt a kilogram of -30C ice would take ~393 kJ, while for -10C ice the figure is ~353kJ. Not a big difference really.

The reality with these air temps at this time of year is that newly exposed seawater (polynya, etc) can't refreeze. That's the biggest difference. Things can open up early and start soaking up that warm sunshine.  Since the temps are pretty close to freezing the atmosphere won't play too big a role for now.  (Later they can induce melt ponds and cause preconditioning, which is a whole separate thing)

27
Arctic sea ice / Re: The 2017 melting season
« on: April 14, 2017, 05:42:28 PM »
There's no sign of any activity on the North Pole Environmental Observatory web site, but nonetheless there is now an ice mass balance buoy in situ near the North Pole:

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/winter-201617-imb-buoys/#2017B

To celebrate I've updated the IMB buoy temperature profiles slightly. The dotted lines at the left show maximum and minimum air temperature over the preceeding 24 hour period. The thermistor 1 reading is now in column 2.

As also reported by the the 2 Degrees North Pole Expedition, it's warming up in the area.

Current Buoy Data (04/12/2017):

Pos: 89.19 N, 30.07 E
Air Temp: -15.56 C
Air Pres: 1020.69 mb
Snow depth : ? cm
Ice thickness : 172 cm

Can you explain the attached graph? Is that air temperature, per hour, on the 12th of April? As it reaches and seems to be steady at -2 that's a bit different than the quoted -15.6.

I'd be very surprised to see that temperature, especially that flat. Usually when I see a temperature graph go flat like that I assume it's because of an ongoing phase change.

28
Arctic sea ice / Re: The 2017 melting season
« on: April 12, 2017, 12:00:24 AM »
Big positive anomalies coming back to the Arctic Basin, Kara and Barents Seas:

Even more crazy when you look at the temps themselves being forecast... since the baseline is rising rapidly this time of year.

The center of the patch in the central arctic is forecast to be above 0 C!

29
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: April 11, 2017, 05:52:01 PM »
BTW... under what circumstances does Wipneus provide the numbers? Or are they no longer relevant/being produced for some reason?

I used to look here first, to see the ice volume of the day...

At least for PIOMAS aftr they are uploaded which happens once a month in the first couple of days of the month on the webpage of the science center that produces those numbers. And they uploaded them a couple of hours ago I think, so I guess Wipneus will update his graphs in a couple of days/ hours

I misspoke when I said volume - I meant ASMR2 Extent & Area (what this thread is for).

I used to look forward to the numbers - including the breakdown by basin. A little tick on a NSIDC chart is not nearly as nice :).

30
Arctic sea ice / Re: The 2017 melting season
« on: April 11, 2017, 05:49:44 PM »
Uni-Bremen is back up.


What's happening in the Hudson? Melt ponds? Is that atypical for this time of year?

31
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: April 06, 2017, 06:01:55 PM »

Yep, water is no blackbody. Nor is ice. The atmosphere makes this a tricky question.


Make simplyfying assumptions as necessary. I was trying to throw weather out, where possible.  Pick your favorite weather, average the weather, whatever makes the calculation easy.

I'm looking for a ballpark figure; when the sun is enough on its own to keep the water open. I really don't have a sense of it.

You can always cheat and use observations; we have pretty good observations of temperature of outbound (as measured by satellite), a pretty good sense of albedo (I did suggest open water), and a little internet digging will give you the incident (I know they exist, though I was't having much luck finding a good one).  It's true that observations are prone to all sorts of variables (most notably clouds) but it should be a decent ballpark.

By early May, the insolation for north pole crosses the incident of the equator so certainly it's somewhere sooner than that. At equinox it's 0W incident, so it's later than that. It gives about a 50 day range; I'd say probably it's between April 1 and May 10 just based on that information.

32
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: April 06, 2017, 04:33:04 PM »
For the pole the break-even day for radiation is of course the equinox since the orbit, but this is still a good question considering lower latitudes.

Well maybe it's s day or two before equinox for the pole since the light scattering and bending properties of atmosphere but for blackbody. I guess the Moon could serve as a nuce example.

I don't think that's the case. At equinox the sun is right at the horizon... I  find it odd that it would be exactly the same as the net radiation water at 0C radiates out.

Anyway I did a little googling (finding:http://www.applet-magic.com/insolation.htm) and it suggests that the incoming radiation is still 0 at the equinox... which I think is perhaps aggressive rounding, but it's all together too big of an angle to be much energy, anyway. 

So it's not that. :)

33
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: April 05, 2017, 06:55:57 PM »
So a relatively simple question motivated by seeing some new ice form...

Do we know what day is breakeven for heat flux, counting only radiation, at various latitudes? Assume clear skies (though I'd be curious for cloudy too), and open water at 0C for albedo/blackbody purposes.

That is - if we only look at heat gained from the sun and heat lost via longwave to space (ignore atmospheric interaction, upwelling, currents, etc), what day of the solar year does this breakeven occur at various latitudes?

34
Arctic sea ice / When is heat flux breakeven?
« on: April 05, 2017, 06:06:47 PM »
So a relatively simple question motivated by seeing some new ice form...

Do we know what day is breakeven for heat flux, counting only radiation, at various latitudes? Assume clear skies (though I'd be curious for cloudy too), and open water at 0C for albedo/blackbody purposes.

That is - if we only look at heat gained from the sun and heat lost via longwave to space (ignore atmospheric interaction, upwelling, currents, etc), what day of the solar year does this breakeven occur at various latitudes?

35
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: April 04, 2017, 06:14:34 PM »
BTW... under what circumstances does Wipneus provide the numbers? Or are they no longer relevant/being produced for some reason?

I used to look here first, to see the ice volume of the day...

36
Arctic sea ice / Re: The 2017 melting season
« on: April 03, 2017, 09:07:34 PM »
JO, what "extent impacts" were you expecting?

Ice that is "rubble"--something like a slushy--is going to be able to spread out faster and further more easily than an ice pack that is mostly made up of solid, multi-meter-thick ice slabs, right?

I suspect that most of our metrics are no longer measuring exactly what they used to be...we can get solid figures on various supposed measures of quantity more easily than we can get reliable estimates of overall quality of the ice.

Last year, I was expecting thin, spread out ice to... well, melt.

But rather than get into an argument about what the "Real state" of the ice is that our metrics can't measure... what I'd like to know is what people expect of the things our metrics can measure.

If we take it as given that the ice is much less thick than last year, that all the good ice went out the Fram, etc, what do we expect that to mean for the ice in June? As measured by ASMR2 or NSDIC or JAXA or your favorite measure.

Will we see a rapid cliff once some condition is met because the ice is too thin to resist? Or will we have a new-normal (2010s)ish melting season but... feel like it's thinner the entire time?  I understand that the weather matters and would be happy with someone saying something like "It's more likely we'll have a record low extent than we did with the same extent last year, because this year's ice is thinner".

37
Arctic sea ice / Re: The 2017 melting season
« on: April 03, 2017, 08:31:49 PM »
BTW the thread to take the year-round ice free arctic discussion is this one: http://forum.arctic-sea-ice.net/index.php/topic,191.msg102977.html#msg102977

What I really want to know about this year is... when do we see the impact of this low volume situation? Last year we heard "rubble", "weak", "low volume", "melt ponds"... all the time, and didn't see the extent impacts I would have felt from such talk.

38
Arctic sea ice / Re: The 2017 melting season
« on: March 29, 2017, 06:47:28 PM »
When it comes to these temperature anomalies... which I've been watching since at least November... I really have to wonder how much they matter this time of year (over ice, in particular).

If there's a patch of the arctic where normally it is -40 C/F, but instead due to huge anomalies it is -10 C, so what? It doesn't melt, melt ponds don't happen... I feel like the thermodynamics don't change...  until it gets above freezing.

Do we expect anything to come of these high anomalies, where temperatures still stay below freezing?

39
Arctic sea ice / Re: The 2017 melting season
« on: March 28, 2017, 08:48:49 PM »
It seems a little quiet today except in the ESS and the Bering Sea.


Are those melt ponds (in the ESS)? In March? It's been anomalously warm... but not that (above freezing) warm. Right?

40
Arctic sea ice / Re: The 2017 melting season
« on: March 24, 2017, 11:08:40 PM »
I believe it to be a good possibility that the  Beaufort ice might be the only ice to offer any resistance to disintegration and melt this year. Everything else is ready to go already.


And we have drift forecast like this for Monday. Tuesday is pretty much the same or even worse.
Image: https://www7320.nrlssc.navy.mil/hycomARC/arctic.html

How can we have drift like this and not have large Polynya open up along the Kara Sea coast? It's been continuously warm-ish there (per cci-reanalyzer) and the 30cm/sec is 25km/day - more than enough to be visible on satellites.

41
Arctic sea ice / Re: The 2017 melting season
« on: March 17, 2017, 09:01:28 PM »
My understanding is that the anomaly tends to be higher in winter and less in the summer.
Yes, but a persistent 4C+ anomaly through the whole winter is new to the data set. Also summer temperatures are limited by the ice. The anomalies during summer will not be this high until sufficient ice is gone.

Right; ice and water together have to have a temperature around 0C; pumping more heat in just turns more of the ice to water. So summer anomalies can't really go up until the ice all melts.

For this reason, in the summer, we tend to look more at the 925 hPa (or is it mb? I forget) temperature forecasts, to get a sense of the warmth being transported in. By not looking right at the surface we can see how anomalously warm it is.

42
Arctic sea ice / Re: The 2017 melting season
« on: March 16, 2017, 10:11:30 PM »
Meanwhile,  the heat is on... cci-reanalyzer shows the lowest anomaly to be reached for the Arctic in its current forecast window is +2.8C. 

This is especially true near Novaya Zemlya, over the Kara Sea temperatures look to be frequently above freezing and not really getting much below.

So ice pumping down the Fram and heat pumping up the eastern Atlantic side...  Perfect conditions for the start of spring.

43
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 07, 2017, 05:35:34 PM »
The formula for energy needed to melt 1980 ice must be different then that needed for melting 2017 ice.

I can't see why. It's true that of course all the other dynamics you mentioned may be different - more (or less) dark ice as a result of particulates, physically more dispersed ice as a result of it being thinner and subject to wave action, etc. And obviously less of it to start with.

But in the end, other than perhaps slight differences in salinity (especially between MYI and FYI), ice is ice and it takes the same amount of energy to melt. Things like waves and particulates change how the energy is delivered and how much, but it still the same amount is energy.

It'll be very interesting to see how the melt season progresses from such a lower starting point; especially one that implies the ice really is a lot thinner (and should melt faster)

44
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 10, 2016, 12:06:38 AM »
After a long search, Barber's ice breaker finally found a 16-km (10-mile) wide floe of multiyear ice that was around 6 to 8 meters (20-26 feet) thick. But as the crew watched, the floe was hit by a series of waves, and disintegrated in five minutes.]
The point is, maybe the ice has been in worse shape than we thought for a while now. Models derived from satellite images just aren't the same as seeing for oneself.

www.reuters.com/article/us-climate-canada-arctic-idUSTRE59S3LT20091029

Somehow I doubt that 10 miles of ice 20 feet thick disintegrated in *five minutes*.  I think it'd last longer than that in tropical waters.

45
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 28, 2016, 08:24:56 PM »
Meanwhile, if we look at SIE numbers, Nov 27th is still some 800k km^2 below the previous record low and 2 million below average. The region is slowly becoming more cold and stable but there's still some wind/wave action happening north of Greenland bringing warm air from the atlantic ocean.

Well... the GFS-generated nowcast shows an arctic anomaly of "only" +2.7 C, dropping to 2.0C before heading back over 3.0C later (but not much higher than that!). Meanwhile, Andrew Slater's 2M temperature graph for 80N+ shows that the current average temperature is now within the 100th percentile for the first time in... a month or two?  And while ice extent is way behind where it should be, the rate of growth is at least typical for the time of year! Barrow looks mostly frozen over, at last!

It's sad that these are the things we have to hold on to, but right now, things are looking like a lot more like a "normal" winter... just on a month delay.  It's kind of hard to figure out what is "normal" in a system that seems to set or nearly set shocking records every year, but it doesn't "feel" as shocking as it did a week or two ago.  That "feeling" won't bring back the ice, but it gives some hope it'll show up later?

It's a "feeling" of a continuation of a long gradual downward slope, and not a total collapse.  We still have 3 months before the normal peak ice, and a  months or two after that before the sun starts to shine down in earnest.  How much more open ocean will it be shining on?

46
Antarctica / Re: Sea Ice Extent around Antarctica
« on: November 24, 2016, 01:48:12 AM »


It looks like the Ross ice shelf totally melts out.  It even looks like polynya are starting to form there  right now.  Is either of those things normal?

I think all the ice shelves in these images are shadowed in with the land mass, as these are not considered to be the same as sea ice and thus not counted with sea ice extent.
See image below.

That makes a lot of sense. I was wondering why the sheets didn't cleanly line up.

I guess given its vastly different properties - being so much thicker - it's not so meaningful (or unusual) for the front between sea and ice to be there.

47
Antarctica / Re: Sea Ice Extent around Antarctica
« on: November 23, 2016, 11:50:22 PM »
What to expect for sea ice around Antarctica?
First frame from Nov. 21(most recent image available)
Second frame is forecast ice for Jan. 1st
Third frame is forecast ice for Jan. 31st
Forecast taken from Climate Reanalyzer
Click to animate please.

It looks like the Ross ice shelf totally melts out.  It even looks like polynya are starting to form there  right now.  Is either of those things normal?

48
The rest / Any Local Discussions?
« on: November 23, 2016, 02:52:47 AM »
Given the unprecedented scale of "the current weirdness", I find myself craving real-time conversation a little more than usual.

So I'm curious, are there any local discussion groups people are aware of? Any forumites in the SF Bay Area?

49
Antarctica / Ice Sheet Balance Graph?
« on: November 21, 2016, 10:48:03 PM »
We have the ice sheet mass balance graphs for Greenland from DMI, that is continuously updated...

Do we have anything like that for Antarctica?

50
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: November 18, 2016, 09:46:09 PM »
Extent and area dipping:

Update 20161117.

Extent: -50.1 (-1200k vs 2015, -1429k vs 2014, -1084k vs 2013, -559k vs 2012)
Area: -24.6 (-1150k vs 2015, -1437k vs 2014, -1064k vs 2013, -536k vs 2012)

The cause is shown in the attached animation (click to start).

Thanks for the update! What determines when we get them?

This is a huge area/extent gap, but I still see lots of potential for catch up before the sun rises and albedo becomes a factor again. We have several months before that!

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