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Messages - Peter Ellis

Pages: [1]
1
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 10, 2020, 07:04:18 PM »
Interesting figures, S.Pansa!  Is there a particular reason why, in Figure 6-5, the incoming and outgoing radiation don't seem to net to zero globally?  (Just eyeballing it, it looks like there's no way the areas under the curves match).
Remember that the total area from (say) 0-10 degrees north is MUCH larger than the area from 80-90 degrees north.

2
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: October 04, 2019, 12:15:38 AM »
Pumice is also foamy with a lot of trapped air, which makes it an excellent insulator.

3
Arctic sea ice / Re: When will the Northwest Passage "open" in 2019?
« on: August 12, 2019, 02:37:27 PM »
1. Don't care what the definition is bc I do not now, and never have, agreed with it, thus stated I was stating my perspective from my very first post. Ergo, I cannot be wrong within that context. I am not attempting to conform.

4
Arctic sea ice / Re: The caa-greenland mega crack
« on: July 30, 2019, 10:12:21 AM »
The phrase you're looking for is "flaw lead".

5
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: July 29, 2019, 01:23:18 PM »
Not free. I followed your link, had to log in ( give information) and then directly request access to the paper. Haven't received it yet.

Here is the abstract of the paper:
Quote
During recent decades, there has been dramatic Arctic sea ice retreat. This has reduced the top‐of‐atmosphere albedo, adding more solar energy to the climate system. There is substantial uncertainty regarding how much ice retreat and associated solar heating will occur in the future. This is relevant to future climate projections, including the timescale for reaching global warming stabilization targets. Here we use satellite observations to estimate the amount of solar energy that would be added in the worst‐case scenario of a complete disappearance of Arctic sea ice throughout the sunlit part of the year. Assuming constant cloudiness, we calculate a global radiative heating of 0.71 W/m2 relative to the 1979 baseline state. This is equivalent to the effect of one trillion tons of CO2 emissions. These results suggest that the additional heating due to complete Arctic sea ice loss would hasten global warming by an estimated 25 years.

From here:

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL082914

... or just use Sci-Hub to find papers <cough>

Looking at it...  this is a self evidently ridiculous paper.  It's a simple albedo calculation, based on the complete absence of ice from March through to September.

From their methods:
Quote
In the calculations of albedo and radiative heating presented here, we use data from the National Aeronautics and Space Administration's CERES Terra SSF Edition 4 monthly averaged 1 × 1-degree product, between March 2000 and October 2016, available online (https://ceres.larc.nasa.gov/order_data.php). The Arctic Ocean is defined here as the land-free area poleward of 60◦N. Due to issues concerning polar night, we only consider the months of March to September of each year.

i.e. they account for extra incoming energy during an ice-free summer, but do not account for any extra outgoing energy during the winter.  This is effectively equivalent to assuming that the Arctic freezes over as normal each winter (i.e. insulating the surface and restricting heat loss) and then the ice magically disappears overnight some time in March.

It's completely unphysical and the only utility it has is giving a ballpark figure for HALF the energy equation resulting from an ice-free Arctic. Don't waste any time trying to interpret this one any further than that.

6
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: July 15, 2019, 02:42:53 PM »
BZZT - ambiguous pronoun referents detected!

"It is worse than we thought" = the "we" refers to the climate science community.

"It isn't as bad as we feared" = the "we" refers to members of this board.

Both statements are thus true, because this board is much more alarmist that the community in general.

7
Convection is when heat is transported by fluid flow.

If the fluid flow is itself caused by the heat (e.g. warm water rising from the bottom of a saucepan, cold water sinking from melting ice) then it is called "free heat convection".  If the fluid flow is caused by something else (e.g. I squirt a warm stream of liquid into a cold pool) then it is called "forced heat convection".

In both cases, heat is transported by moving hot molecules from one location to another, rather than by transferring energy from one molecule to another.

8
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: July 04, 2019, 10:14:45 PM »
am i the only one who thinks that i cannot be a coincidence that several time each year, around special events like extent falling below 2012/2016, minima, maxima or other extremes, some of the data providers stop delivering.
Probably not, there's a lot of nutters out there.

https://i.kym-cdn.com/entries/icons/facebook/000/016/146/eird-al-yankovic-tin-foil-hat-160x160.jpg

9
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: July 03, 2019, 02:34:55 PM »
A-Team posted this back on November 24, 2017 on the Ice Apocalypse thread.  I think it is a little funny yet worth another read considering the shape of the Arctic Ice today and should cause us to pause a moment and consider the implications.  It also parallels gerontocrat's "Perils of Projections."

Another parable I find of use in my own field of molecular biology is to consider how your measurement protocols affect the thing you're measuring.

When the blind men studied an elephant, they could not agree what it was like.  They said:
"An elephant is like a rope"
"An elephant is like a treetrunk"
"An elephant is like a wall"
"An elephant is like a snake"
"An elephant is like a sail"
Nevertheless, by synthesising their points of view, they were able to approximate the truth.


In contrast, when the blind elephants studied a man, they were unanimous:
"Men are flat"

10
Arctic sea ice / Re: The 2019 melting season
« on: June 17, 2019, 01:00:37 PM »
My question concerned the other blue line on that plot, the LIGHT blue line labelled "Anom. Forecast", which may well be short for "Anomaly Forecast". I have no idea how this line was derived.
The "anomaly forecast" simply assumes that the anomaly stays constant, i.e. if we are currently 2 million below average, then in 50 days' time we will still be 2 million below average. Note that the anomaly in this case measured relative to the 1988-2013 average.

From the "About the Plots" section:

http://cires1.colorado.edu/~aslater/SEAICE/
Quote
"Anomaly Persistence uses data from 1988-2013 as the mean state."

11
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: April 24, 2019, 01:11:00 PM »
If you want to remove heat from the ocean, that heat has to go somewhere - and it has to go somewhere that is colder than the ocean. You could melt the ice caps, using Greenland and Antarctica as the heat sinks. This is a bad idea. Or you can let the energy radiate out to space, using the cosmic microwave background as a heat sink. This is a better idea, but requires us to stop adding insulating gases that get in the way of transferring heat from our planet into space.

12
Arctic sea ice / Re: Latest PIOMAS update (April 2019)
« on: April 16, 2019, 12:52:55 PM »
I think an exponential was the perfect fit from about 2002 to 2012. After and before that period linear fits were better. Sometime in the near future exponential fits will become the better fit again.
That suggests to me that the "bound" the exponential trend ran into (and bounced off of) was 3-4000KM2 rather than zero.

Let me once again point to Tietsche et al 2011.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL045698

DO NOT LOOK AT THE TIME FRAME
DO NOT LOOK AT THE SPECIFIC "ICE FREE" THOUGHT EXPERIMENT

The point to make here is that Figure 1 shows the "shape" of the decline towards zero, as predicted by a full climate model with atmosphere, ocean, geography and bathymetry included.  It is not linear, exponential, Gompertz or any such simple shape.  It is conditioned by the ocean currents, land masses and airflow patterns.  These conspire to produce a "stepped" decline with plateaus at ~4.5 million km^2 and ~2 million km^2 mean September extent.

The first plateau corresponds to an Arctic where (roughly speaking) the "shallow rim" seas melt out, but ice cover is retained over the deep central triangle.  The second plateau corresponds to an Arctic which is mostly ice-free but has a remnant core of ice crammed up against north Greenland/Ellesmere. Since 2007, we have been basically bumping along the first of these plateaus, as is clear from the September record.
http://nsidc.org/arcticseaicenews/2018/10/

It's anybody's guess as to when we fall off and plummet down to the second, but the Tietsche paper suggests it will be some time in the next decade. Given the rather wide standard deviation, the "ice free" threshold of 1 million could be hit at any point thereafter.

14
The forum / Re: Poll predictions are stupid
« on: September 23, 2018, 12:41:50 PM »
They're useful, but not for anything they tell us about the ice.  They're useful as a barometer for how "connected" this forum is with reality.

An interesting exercise - if technically feasible, which I assume it isn't - would be to have two versions of the results graph.  One where everybody's vote is weighted evenly, and one where the votes are voted by how prolific each poster is.

The first of these tells us whether the readership of the forum has any insight into what's actually going on.  The second tells us who's driving the forum content, and whether they're more or less barking mad than the rest of us :-)

15
However, as A-Team remarked earlier this melt season, the time of peak solar activity does not overlap well with the time of minimum ice. 

Why would you expect it to?  Even in a world where sunlight is the main cause of ice melt, then the peak solar activity would not coincide with the point of minimum ice but with the peak point of ice loss - i.e. the steepest part of the yearly ice loss curve during the melt season.

As it happens, there's a little bit of extra lag beyond that, because it takes a while for various short-term summer feedbacks (snow melt lowering albedo, melt ponds and leads likewise, and the sheer time taken to melt through the ice layer) to kick in. Not much of a lag though - the point of fastest melt rate typically occurs within 2-4 weeks after the solstice.

The inflection point between melting and freezing (i.e. the annual minimum) happens at or around the equinox, more or less exactly as you'd expect from that being the point where solar input (or rather radiation balance) starts to turn negative.

If you approximate ice extent as a yearly sine wave, it's offset by 1/4 of a cycle from the solar input cycle, exactly as you'd expect if insolation was the main factor affecting melt and freeze-up.  Sure, there are other interesting dynamics from warm air and warm water intrusion - and we discuss them to death every year - but they're second order effects.

16
Arctic sea ice / Re: SMOS
« on: July 22, 2018, 02:44:12 AM »
Bottom melt happens primarily near the edges of floes, and the heat source is from radiation absorbed by the open water between the floes.  The onset is generally quite late in the season, but because of the huge thermal mass of the ocean, it can continue even after atmospheric temperatures have dropped below freezing at the transition from summer to autumn.

Anything other than the above is a mere detail in the small decimal places. This forum used to know stuff like this!

17
Arctic sea ice / Re: SMOS
« on: July 21, 2018, 10:38:50 AM »
...the factual claims you keep making are large, strange and without evidence, and I see it as my duty to point this out before this forum becomes a fantasy free-for-all.
Quite. As far as I can tell from Hyperion's ramblings, warm air currents are supposed to magically cause bottom melt without top melt, so the ice surface stays dry.  A contention that's trivially disproved with a large dry martini and a hairdryer.

This magical bottom-only melt arises because "Ice conducts heat better than water", and so it will conduct the atmospheric energy through to the water under the ice, allowing the ice to melt from the bottom, but not the top.  This is drivel.  Heat cannot of itself pass from one body to a hotter body. i.e. if the ice is conducting heat downwards, then the top of the ice is hotter than the bottom, so the top will melt first.

18
Arctic sea ice / Re: SMOS
« on: July 20, 2018, 12:09:05 PM »
So massive thickening in the CAB, so I presume melt season somehow ended already?
It's not thickening.  SMOS doesn't measure thickness accurately during the melt season.
(This could be posted as a followup to every other post in this thread, so let's just assume it was)

19
Arctic sea ice / Re: 2018 sea ice area and extent data
« on: July 14, 2018, 09:40:00 PM »
Worldview shows thick cloud over the basin, I expect that's confusing the sensors and a significant amount of it will reappear in a few days. The images from 11th/12th didn't look anything like as low concentration as Uni Bremen suggests, so it's probably also getting confused by melt ponds.

20
Arctic sea ice / Re: The 2018 melting season
« on: July 14, 2018, 09:34:47 PM »
Well they have plenty of sub's and drones both above and below.
... no they don't.  They integrate what data is available, which is very very little.  It's predominantly a mathematical model driven by weather data, with assimilation of ice concentration data from NSIDC.

21
Arctic sea ice / Re: 2018 sea ice area and extent data
« on: July 11, 2018, 09:06:51 PM »
OK, I will buy into that.  Now....how close are we to an average size being about 100M?
A very long way away.  Any floe you can see on Worldview is a minimum of kilometres across, given that the pixel size is 250 metres.

The centre of this picture has some faint milky swirls. That's what floes smaller than 100m look like, because each one isn't large enough to turn a whole pixel white.  Not a lot of the Arctic looks like this yet, thank God.
https://go.nasa.gov/2NI3qW8

22
Arctic sea ice / Re: Land snow cover effect on sea ice
« on: July 08, 2018, 12:24:03 PM »
Normally for a hind-cast, that would include ALL the prior years available.

No.  To be a hind-cast you have to use the algorithm to predict data points that ARE NOT PART of the dataset used for the regression.

Forecasting is predicting future data.  Hindcasting is "predicting" data that already exists, which you do by not looking at it before you make your prediction. That graph contains three forecast points (2016-2018) and no hindcast points.

23
Arctic sea ice / Re: Land snow cover effect on sea ice
« on: July 07, 2018, 11:56:37 PM »
Here is what this hind-cast method did for the past 26 years :
Presumably at least some of those years were the ones used to fit the regression line, rather than being true hind-cast years.  Which of those years were not part of the data set used to fit the regression?

24
Arctic sea ice / Re: September Predictions Challenge
« on: June 24, 2018, 01:12:08 PM »
Maybe it helps to reframe it.  Think of it like betting on a roulette wheel.  Each of us gets a hundred tokens.  Distribute those across the various bins, and at the end of the day, your score is however many tokens you put in the correct bin.

High confidence means you stack all your tokens in one bin.  If you're right, you score 100, otherwise you get nothing.

Medium confidence means you put 50 in one of the bins, and the rest in the adjacent bins.  If you're dead on - well you still only score 50, because you weren't really sure about it.  If you weren't quite dead on, you get to pick up 25 points or so because you had at least a few tokens in the right bin.

Low confidence means distributing your tokens widely.  Sure, you'll pick up a few points no matter what the result is, but only a few because you basically pulled the numbers out of your fundament.

Or, put yet another way, saying you have "high confidence" in one bin is the same as saying you're certain it won't be in any of the other bins - so why would you expect to score points for them?

25
Arctic sea ice / Re: How soon could we go ice free?
« on: June 20, 2018, 08:10:45 PM »
Yes, that graph is from 89 ensemble runs under RCP8.5 emission scenario.  The mean value is still above 1.0 M km2 by 2100.  The large variability is due to how much weight is placed on various factors, such as albedo, clouds, radiation losses, and observational data.
The mean is the wrong measure to use when there are significant outliers like the red series of lines.  Try something more robust like the median.  A median which - with five more years of data to include after the plotted values that stop at 2017 - the real world is pretty much bang on.

Of course, do also remember that this isn't a prediction of the FIRST ice free year.  When the median hits 1.0 M km^2 (in around 2045), it means that ~every other year will be ice free.  The first ice-free year could easily come a decade earlier in 2035 or so.

26
Arctic sea ice / Re: How soon could we go ice free?
« on: June 19, 2018, 09:18:40 PM »
Seriously - ignore the blue bits on this and just look at the black line and dotted surround, i.e. the long term trend and the variability around that trend.

The variability goes below 1 million square km from 2035 onwards, i.e. it's predicting that from 2035 onwards, a "bad year" for the Arctic will count as ice-free for the entire month of September, not just a day or so.  From ~2055 on, the UPPER bound is below 1 million, meaning that EVERY year is ice-free for the entire month of September, even the good years.

This paper, and that graph are SCARY AS FUCK.  They say we are on the edge of a precipitate decline (the trend from ~2020-2035 is 2.5x the trend from 1985 to 2010) to a "remnant rump" state with a residual amount of ice hanging around northern Greenland.

27
Arctic sea ice / Re: How soon could we go ice free?
« on: June 19, 2018, 09:11:39 PM »
Quote
I think you misunderstand the Tietsche et al 2011

Ditto. A model is an abstraction of reality, some of them can be useful. In the reality created by Tietsche et al 2011 Arctic sea ice extent does not reach 0 until 2070. That goes against observations

No it doesn't. Arctic ice has not reached zero yet, nor has the year reached 2070.


...and many models, particularly more recent models. 

This would be more believable if you linked to the models and publications derived therefrom.

In that universe where Arctic extent decay is so slow that it won't disappear until 2070, the arctic recovers after a BOE.

I wish I hadn't mentioned the BOE aspect.  The point I was making was not about what happens in the event of a BOE, it was to discuss the shape of the way the long term trend approaches zero, i.e. a stepped decline.  The Tietsche model is not really "so slow" - it predicts that the current slight plateau is temporary, that the trendline is about to accelerate sharply downwards, that there will be a rapid collapse over about a decade or so to leave a rump of about 1.5 million square km hanging out above Greenland.  Their error bars show a dip below 1 million square km (i.e. the generally accepted "ice free" threshold for the Arctic) as early as 2035.

If even that isn't alarmist enough for you, I honestly don't know what to say.

28
Arctic sea ice / Re: How soon could we go ice free?
« on: June 19, 2018, 08:15:08 PM »
Read the context. He posted that paper out of context since we are talking about the first ice free arctic, not the year after the first ice free arctic, which is the context of the paper.

No, you missed the two points I was making.

1)  In their model, when you perturb the system - even a perturbation as massive as removing all ice - it returns to the long-term trendline within two years.

This means that it's important for us not to get misled by single extraordinary years, but instead concentrate on the shape of that long term trendline and how it declines towards zero. The claimed two-year "memory" of the Arctic for extraordinary shocks is consistent with what we see in the real world, where there was a short-term "rebound" after both 2007 and 2012, but in each case the "rebound" only took us back up to the long-term downward trendline. 


2)  Leaving aside any of the artificial non-physical perturbations, the SHAPE of the approach to zero is not linear, not quadratic, not exponential, and not a sudden "poof" to zero.

The prediction is for a "stepped" decline with plateaus at ~5 million and ~1.5 million km^2. These plateaus are dictated by the overall geography of the Arctic and the bathymetry of the Arctic ocean. In my view regardless of whether their precise predicted timetable for the fall towards zero is accurate or not, these plateaus make physical sense, and so we should expect a similar "stepped" decline to play out in the real world.



As it happens, the real world progression of September extents seems to be reasonably close to their model, which predicts a plateau until ~2020 and then a comparatively rapid collapse to about ~1.5 million.  I would hazard a guess that we're on the verge of that transition.

29
Arctic sea ice / Re: How soon could we go ice free?
« on: June 18, 2018, 12:25:28 PM »
I think Figure 1 from Tietsche et al 2011 is important.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL045698

This shows two things - firstly, the general shape of the (modelled) decline in Arctic ice over the coming decades, and secondly the time taken to recover from extreme events such as the summers of 2007 and 2012.

For the latter, the conclusion is quite simple - the Arctic has a "memory" of about two years, and so any major excursion will bounce back to the long-term trendline within a couple of years.  They only modelled downward excursions, but my guess is that it holds the other way too - even if by chance we have a particularly good year for ice retention, it'll be gone in another couple of years.  The paper discusses the mechanisms for this, but fundamentally it's quite simple - if you have a massive loss of ice one autumn, that means a correspondingly massive extra heat loss in the following winter.  By the end of spring, first year ice has grown back. A low summer minimum has very little effect on the following maximum.  This is believable, and we've seen it after every major loss year for more than a decade now.

For the longer term decline, look at the shape of the curve.  Note how it's staggered and stepped.  This reflects the shape of the Arctic ice basin. There are shallow seas around the edge, and a deep central portion that covers about 5 million square km. So, as ice loss progresses, there's an initial period of rapid decline that plateaus at around 4.5 to 5 million until about 2020.  That's exactly where we are now, in that plateau, where the summer minimum roughly covers the deep parts of the Arctic Ocean but the peripheral seas melt out each summer. Subsequently, there's another period of rapid decline that plateaus again at 1.5-2 million.  This is the "remnant above Greenland" stage.  The final collapse comes after that.

The shape looks entirely plausible to me, all that we need to work out is the scaling on the X axis, and to be honest I'd be surprised if they're far off. Right now we're on the verge of the second period of decline - but it'll plateau again in another couple of decades, probably before hitting the "ice free" threshold of 1 million.

It may be we need to squash the X axis up by 10% or so to fit reality - someone with more time than I can probably make an overlay - but it's really not far off.

30
Arctic sea ice / Re: The 2018 melting season
« on: June 12, 2018, 07:29:46 PM »
... Nasa came to a different conclusion in the case of the smaller Mackenzie River in 2012 ... after an ice dam gave way, Aqua infrared showed phenomenal near-surface warming of an area ~ 500 km x 500 km. (In the case of either suspended sediment or algal bloom, heat from sunlight is captured higher up in the water column than it would have been otherwise.) ...
Never thought about the Mackenzie ice dams (which develop to some extent every year, I recall reading) being part of the 2012 'perfect storm'.

... they're not talking about normal year-on-year river flow, dammed or not. 

They're talking about a one-off pulse of 9,500 km^3 of fresh water from partial drainage of Lake Agassiz - a relic of the Ice Age approximately the size of the Black Sea.  Yes, that'll have an effect on Arctic ice.  It's not remotely relevant to year-on-year observations of sea ice melt.

31
Arctic sea ice / Re: Arctic sea ice minimum early prediction
« on: May 31, 2018, 12:11:15 PM »
That depends on much faith you would put in predict-o-matic value 0f 4.33.  If the predicted value is 6th lowest, would that not be a more reasonable guess, based on valid inputs?

No, it would not be if the question is (as it was) is how ought I bet if I bet the same way every time.

Right, so what you want to know is the distribution of yearly ranks when considering only the dataset to date.  i.e. 1979, as the first full year in the series, was by definition a new record (rank 1) even though it's now ranked 30th in the dataset.  1980 was a bit higher, so it was second lowest (rank 2) at the time even though it's now ranked 39th. 2005 was a new record at the time even though it's now ranked 12th, and so on.

Here's the stats:

Rank to date   #years with that rank
1   10
2   8
3   8
4   3
5   3
6   2
7   2
8   1
9   1
10   0
11   0
12   1


Thus, if you're betting on the rank, it always makes sense to bet in the lowest bracket.  Not particularly surprising given that there's a downward trend.  Not a lot in it though, ranks 1-3 are all quite close to each other. This indicates that the average yearly residual is about three times larger than the yearly decrease in the linear trendline.

32
Arctic sea ice / Re: Arctic Ocean 'acidifying rapidly'
« on: May 17, 2013, 11:15:23 PM »
Something can not become "more acidic" if it is not acidic to start with.
A child can't ever get taller, only less short.  One whisper can't be louder than another, only less quiet.  You can't edit your post to be more intelligent, only less stupid.

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