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Messages - andy_t_roo

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1
Do we know the ground topology for this glacier that leads to this different behaviour?

In order to sustain a long and narrow profile this glacier either has a higher "ice pressure" feeding it or has a lower melt-rate. Alternatively this entire glacier has been unstable for a while, and has only just fallen of it's equilibrium enough to disturb the structural integrity of the area past the front, and cause the calving that we haven't seen before.

This "long+narrow" is a qualitative observation compared compared to something like the short+stubby shape of other glaciers that we talk about eg:

79N is thinning

2
Arctic sea ice / Re: What the Buoys are telling
« on: May 14, 2017, 02:09:20 PM »
I produced a plot of ice temperatures last year, so I have done the same for buoy2017A starting from 10.March.
Xaxis are days counting from 10.March  i.e. 60 = 9.May
Y axis are temperatures at the thermistor string  numbered downwards from the top , about .5m above the ice down into the sea below it. Horizontal lines are at -5 -10 ... -25 C
The temperatures at the thermistors above the snow are the lowest during winter and the temperature of all thermistors below the ice are nearly the same at -1.6
It shows large daily fluctuations when clear skies in April brought high daytime and low nighttime temperatures, but more steady higher temperatures when moist warmer air inflow brought clouds.

Is there enough information to estimate the thermal conductivity / heat capacity of the ice, by thickness there -- you have the time series of top/bottom temps, it feels like it won't be too hard to calculate the estimated energy flows between each sensor, as you have the oscillation at the surface, being damped at each layer, combined with the long term trend from the weather ..

3
Anything comes to thermal equilibrium with its surroundings. You can think of this material as, by being selective about only absorbing or emitting frequencies that the atmosphere is transparent to, being slightly closer to thermal equilibrium with empty space, rather than the sun. The downside : strong emission = strong absorption, so this only works when exposed to the sky, if you point it at anything that naturally emits ir at that frequency (the ground) then it will not cool.

4
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: February 09, 2017, 09:28:29 PM »
I must say the PIOMAS location of the thick ice is very strange.
Indeed.
Could that be related to https://www.washingtonpost.com/news/energy-environment/wp/2016/04/08/the-melting-of-greenland-and-antarctica-isnt-just-raising-seas-its-changing-the-earths-rotation/ perhaps?


Unlikely. The earth will slow down as the mass from the poles gets distributed across the oceans.  Think of an ice skater in a fast tight spin holding out their arms and slowing down. It's simple conservation of angular momentum.
I believe we are looking at micro-second level variations here, as there are several effects here https://en.m.wikipedia.org/wiki/Day_length_fluctuations has a reasonable summary of observed variations in day length. I believe Greenland is capable of causing an effect, but not sea ice, as the sea ice (like the ocean it floats on)  is already at a gravitationally neutral position.

5
Arctic sea ice / Re: Arctic Cyclone Trends
« on: January 21, 2017, 12:47:51 AM »
Hello All,
...
I'm looking for some background information on Arctic weather. I know storms are not uncommon in the Arctic but is there a trend change in frequency, duration or intensity?
...
Welcome to the forum Pragma.

Re: storms in the Arctic, storms with lightning are actually quite a new occurrence -- http://neven1.typepad.com/blog/2016/07/iced-lightning.html . Although i'm not aware of any quantitative long term measures of storm strength, storms without lightning would have to have much less moisture and hence energy involved, and the substantial increase in lightning strikes would roughly correlate with the impact on the ice these storms could have.

That people here on the forum look at these storms getting to the arctic and invent terms like 'cyclone cannon' to describe the unusual train of storms getting to the arctic in the absence of strong blocking by the polar vortex/jet stream means that people more knowledgeable than me are also somewhat surprised.

6
Antarctica / Re: Sea Ice Extent around Antarctica
« on: December 19, 2016, 09:42:10 PM »
Winter rainfall over Australia was extreme this year ...possibly caused by the southern ocean lows moving slightly northward
http://www.bom.gov.au/tmp/cc/rranom.aus.0608.58473.hires.png
Sorry kiwichick16,  but both your links are 'page not found'

7
Antarctica / Re: Sea Ice Extent around Antarctica
« on: December 18, 2016, 09:36:10 PM »
Given that the ice melts back to the coast in many areas, even on an normal year, is anyone able  to split out the area graphics by region, or longitude?

This would allow the discussion to be split into 'the area was probably going to melt anyway so what does extended exposure to sea temps for the coast/ glaciers mean? '  and 'will the higher rate of melting mean this area will melt?'

8
Arctic sea ice / Re: Ice free predictions and their uncertainty
« on: December 08, 2016, 09:17:40 PM »
The line drawn looks to be very good but does it really extend to first and last 15 years well?

I don't think you can rule out the following sort of relationship

One thing to remember is that co2 is the forcing agent, and as such the amount of it in the atmosphere relates to the rate of change, as the equilibrium point gets further away. If we stopped emitting today, that graph would go straight down for a while.

9
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 03, 2016, 10:44:44 AM »
GFS is not looking much better seven days out for the Arctic.

It also seems that they have redefined their colour scheme, with red->white in the +20-30 range ... because of the issues  with the colour scale being clipped at +20 red previously.

10
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 25, 2016, 12:52:46 PM »
one thing to keep in mind is that ice is an insulator, so the first meter or 2 is by a huge margin the easiest to grow;
growth becomes an exponentially declining value, so if instead of -20c it sits at -10c all winter, the thickness will be more similar than you might think (ie, halving the temperature difference from freezing, will mean it will probably be missing the thickness of ice that would reduce heat flow by 50%.

(some more relevent numbers -- https://nsidc.org/cryosphere/seaice/processes/thermodynamic_growth.html suggests that one such emperical formula is Thickness (cm) = 1.33 * FDD (°C)0.58; )

estimating climatology as ~2000 fdd by this time we get ~110cm
we are missing ~600 fdd, so 1400 fdd gets us ~88cm. I'd expect this ~20cm deficiency to either persist (if temps remain warmer than normal), or begin to decrease if temps return to mean as the lesser ice insulation allows slightly faster than normal growth in the latter part of the season.

(all the numbers are ~ because estimating fdd over ice that has just frozen up is wonky, the formula is emperical, weather is unpredictable, and we don't know if the broken up initial state and current humidity invalidates prior estimates of energy flow)

<last paragraph of speculation on how this means it might look like the ice recovered edited out, as i don't feel that speculation without reasonable evidence to back it up adds to the quality of this forum; i'd like to thank everyone who has contributed to the informed discussion around here>

11
Arctic sea ice / Re: Albedo-Warming Potential
« on: October 31, 2016, 07:41:54 PM »
Once the sun goes down permanently in the north, the emissivity of water is a strong negative warning potential, due to the energy imbalance. Would it be possible to update charts to show the net effect of the unprecedented area of open water that currently exists?

12
Consequences / Xkcd on climate change
« on: September 13, 2016, 09:41:40 PM »
Xkcd has once again managed to put together a graph / comic that simply illustrates a complex issue ; in this case the current rate of climate change vs historical rates.

http://xkcd.com/1732/

13
The rest / Re: Do you understand the Enthalpy of Fusion of ice?
« on: September 01, 2016, 10:04:16 PM »

So take 1g of ice combined with 1g of water at 80C, and you get 2g of water at 0C.

What does this mean for the arctic? The amount of energy required to melt 1g of ice will heat that same 1g of ice by 80C. Which is to say, melting ice absorbs an astounding amount of energy. What if the ice weren't there? Then instead of melting 1g of ice, you would heat that same 1g of water by 80 degrees! Or more realistically, you'd heat 10g by 8 degrees or 100g by 0.8 degrees.

Point being, things get really hot, really fast.

Except that the volume of ice is quite low, what do you get when you mix a water column of 1m of ice (0c) and 80m of water (1c); the same all water 0c.

We have been discussing the effects of wave action on the ice elsewhere  and recent estimates of the storms have the swell penetrating  broken Ice and mixing the top 50+m. And we see this effect with large swathes of ice quickly melting under certain storms.

14
Arctic sea ice / Re: 2016 sea ice area and extent data
« on: August 28, 2016, 09:21:29 PM »
Here is the shadow CT-area report based on calibrated F18 NSIDC sea ice concentration data:

day  CT-date       NH               SH                Global
Sat 2016.6493 -170.0  2.918565  +56.9 14.809784  -113.1 17.728349
Sun 2016.6521 -109.9  2.808624  -40.2 14.769591  -150.1 17.578215
Mon 2016.6548  -52.5  2.756159  +81.7 14.851282   +29.2 17.607441
Tue 2016.6575  -57.9  2.698250  +53.4 14.904697    -4.5 17.602947


Single handed done by the CAB: -64k.

Shadow NSIDC extent is now 4.5373 dropping -172.4k. Done by the CAB (-132k), Chukchi (-29k) and ESS (-24k).

The left Wrangle arm is in flames in the attached delta image.

If this is a compaction event, does anyone know why there is a lack of light blue concentration increases internal to the pack in recent days?  We are even seeing blocs of concentration drops (light red)?

15
Both sides at once? Does anyone know how mechanically couped the 2 sides are? I would of thought that undercutting from the front would cause failure on one side only. Could this be caused by ice  pushing from behind. That way a failure on one side increases the stress on the other making it fail also.

16
Arctic sea ice / Re: 2016 sea ice area and extent data
« on: June 04, 2016, 07:08:44 AM »
Wipneus,
Is the F18 data available for last year?
if so you could get a feel for how accurate is by running last years data through your algorithm, and comparing the the F17 data previously used.

17
Arctic sea ice / Re: The 2016 melting season
« on: May 06, 2016, 11:13:37 AM »
...
You talk about the last 15 years: what is the clearest way of seeing this dramatic loss?
to put things into perspective, volume wise :


18
Arctic sea ice / Re: Glossary ... for newbies and others
« on: April 10, 2016, 02:14:03 PM »
a low resolution labeled picture showing which areas of the arctic are refereed to by each of the area graphs would be nice

as eg : https://en.wikipedia.org/wiki/Barents_Sea doesn't list actually what area is talked about, but we're quite happy to list the amount of ice in it at https://sites.google.com/site/arcticseaicegraphs/regional

perhaps something like a labeled version of the following?



19
Policy and solutions / Re: Batteries: Today's Energy Solution
« on: March 08, 2016, 01:14:00 PM »
talking about energy density in inverters;
typical solar inverters run at ~5w/cubic in

google ran a competition, with a top prize of $1 million for an inverter with a power density of more than 50w/in3

the winners turned in a 143 w/in3 inverter (2kw in 14 in3).

http://googleresearch.blogspot.com.au/2016/02/and-winner-of-1-million-little-box.html

I guess this means that there is still quite a way to go in power engineering, it's more a lack of demand that has been holding us back ...

20
Consequences / Re: 2015/16 El Niño, the aftermath
« on: February 07, 2016, 10:40:00 PM »
When looking at NOAA's weekly SST data, it's now over a year ago since they reported negative anomalies for the Nino4 region. And the last time it was at -0.5° (or lower) was in April 4:th, 2013.

Now there's only five individual runs below 0° in the attached Nino4 forecast from CFSv2, the trend has been that the demize of this event has been pushed forwards and it's becoming more and more likely that we will not have a La Nina at all this year.

It will be really interesting to see the plumes from ECMWF for February.

Given that the world as a whole has warmed, isn't an average of 0.5 indicative of just a shift in the mean,  and not an excess buildup of heat in only 1 specific area? 


21
Arctic sea ice / Re: The 2015/2016 freezing season
« on: January 31, 2016, 10:08:28 PM »


Considering that the Arctic temps were well above normal during the last 3 or 4 days of 2015, we now have had in excess of 30 consecutive days with temps in excess of 5o C above the long term average.  This must have some eventual impact on the final maximums of area, extent and volume.  How much....I don't have a clue!!

According to http://cires1.colorado.edu/~aslater/ARCTIC_TAIR/index_80_t2m.html we are about 500 degree days warmer than the average and for the last week the warmer than all years up to 2010.

22
Arctic sea ice / Re: The 2015/2016 freezing season
« on: December 29, 2015, 05:15:34 AM »
Yes the heat is being pumped in, but that means more overall energy lost to space...  Energy radiated is proportional to temperature difference squared (or so, it could be ^4 atmospheric physics is complicated ), so the further form its normal - 20 or so, the more energy the world as a whole looses. 
Remember that without sunlight open water has perhaps a 400 w/m energy imbalance,  which is why most of the central Arctic basin freezes the moment the sun goes down.

23
Consequences / Re: 2015 El Niño?
« on: November 16, 2015, 10:23:09 PM »
I think the impacts of El Nino are a good entry into climate change discussion ; a small part of the Pacific gets 2c warmer and entire continents have issues, and we are looking at a permanent (hundreds of years ++)  future change of that scale across the entire world...

24
Policy and solutions / Re: LENR as a new energy source?
« on: November 05, 2015, 10:44:27 PM »
Low energy fusion must be a hoax unless completly new science is invoked.

Fusion happens when nuclei get close enough for the nuclear force to become attractive.
That occurs at approximately^ 10^-15 mm ( https://en.m.wikipedia.org/wiki/Nuclear_force)
Atoms themselves are approximately 10^-10m in size, and the electrostatic force from the positive charge of the nucleus repells based on distance ^-2
Therefore the the repulsive force to be overcome to achieve fusion is at least 10^10 times stronger than the influence of the next nearest atom.  (low temperatures in a solid = spacing of atoms at more than 10^-10m apart)

Ie,  the only way to get fusion is for(at least)  one of the particles to be moving fast enough to overcome this barrier, and other atoms in the (chemically distant)  vicinity have no significant effect. Fast=hot.

Hydrogen fusion is actually the easiest fusion to do, and we can't even do that in a sustained manner at the moment.

25
Arctic sea ice / Re: The 2015/2016 Re-Freeze Season
« on: August 27, 2015, 11:23:34 PM »
Given the surface radiative imbalance, I think that extent of refreeze isn't going to do to much interesting, as irrespective of water temperature, the surface will always be able to freeze. (It's a non-linear process)
This however could mask a much bigger volume drop as the insulation effect of ice/show combined with slightly warmer water prevents thickness growth.

Are the end of the day, the energy required to melt/freeze all the ice is treated to volume, but we can only measure area (extent when melt ponds are around) with high accuracy. So I think we could set up for a season with unexpectedly high melting without realising it.

26
And here we go again, remember this glacier is never supposed to calve, but anyway, we have a dual calving and by the way the calving to the left was created at least because of a melt water river :

Why is it that it is never supposed to calve, other than a lack of doing so for an extended period of time, through to 2012?

27
Quote
IW velocity-mapping by cross-correlation is preferable to manually picking features to track

Good point. Getting at the velocity vector field manually over any kind of area would drive a person to distraction. Repeating over many image dates would finish them off. However there is some value in identifying hotspots, anticipating what magnitudes to expect and determining whether acceleration is plausibly within reach of IW Sentinel within what sort of time frame and what level of error.

In the presence of contrast changes, normalised mutual information is a much better alignment measure that cross-correlation
Correlation matches absolute brightness values, where as mi roughy corresponds to comparing histograms.

The extreme example is 'match a white square on a black background with a black square on a white background' any corr. Based measure will return ' don't overlap the squares at all' any mi based measure will return 'overlap the squares as much as possible'.
Mi is also relatively insensitive to multiplicative noise, as long as the underlying 'texture'is still there.

Another alternative approach is to preprocess the data with x, and y gradient operators, and match vs offset is based on  abs (corr x) + abs(corr y)

You should be able to co register Landsat and sentinel data that way, given that edges in one field are also edges in the other, and we know the precise scaling factor between the 2 data sets.

(I have done post research looking at how to compare and align medical images)

28
Arctic sea ice / Re: 2015 sea ice area and extent data
« on: August 01, 2015, 12:52:45 AM »
From today's NSIDC data update I calculate the following CT updates (the days in this list are the days of data released, three days behind ice dates):

Thu       4.562689
Fri -30.1  4.532572
Sat -119.4  4.413175

Saturday's century is mostly the result of the CAB (-63k4). Smaller contributions from Baffin(-17k), CAA (-15k) and Laptev (-14k).

Some of the concentration drop seems to align with the heating over the north of CAA and the bordering CAB.

In the attached NSIDC delta map, pixels with larger concentration changes than 7% or colored pinkish (down) or light blue (up). Solid red and blue are where the pixel concentration crosses the 15% limit (for extent).
I'm surprised that there are significant concentration drops in what is traditionally the most solid ice area next to Greenland. That we have a low compactness isn't a surprise to me at all, given the way the ice is broken up but no strong melt front has been established.

29
Arctic sea ice / Re: The 2015 melting season
« on: July 30, 2015, 11:51:35 PM »
Yes. Extent is not worth looking at. I think the the only thing worth looking at are volume and ice thickness.
I believe, from a satellite perspective extent is the most accurately known number, as melt ponds, clouds, fog, snow cover, and a lack of resolution hinder accurate measurement of area.
Thickness is only exactly known at a few points,  so any volume measures must be a model of both area, correcting for the errors above, and thickness, estimating the thickness pattern from sparse measurements and weather patterns.

I think everyone here would agree volume is one of the most important measurements, as that is what absorbed energy directly affects, but it is also the hardest to know actually. (See discussions elsewhere on the difference between the various models)

30
Arctic sea ice / Re: What the Buoys are telling
« on: July 19, 2015, 06:12:50 AM »
this floe at camera2 shows what ice looks like when it is getting thin.
I think the ice is now porous from molten brine channels and therefore translucent when low in the water and wet but white when the the drained brine has been replaced by air.  The image shows that the surface of the floe on which the camera stands is still well clear of the water but the reduced density of the ice above the waterline gives an exaggerated impression of its overall thickness.

and this picture also highlights the difficulty of separating melt ponds from ice area; this picture shows that the circular holes in the ice appear to be true holes, so represent a decrease in area; does anyone have a satellite picture of this area, and what it looks like compared to the earlier times when we could see that they were melt ponds instead?

31
Science / Re: A Looming Climate Shift??
« on: July 12, 2015, 04:45:58 AM »
the scary part is the bifurcation..
a sudden shift between the states... im not sure the exact temp difference where this exists....

I don't think anyone is, as it depends on the shape of the temp gradient, and that varies depending on land cover, as is indicated by they possibility of extended differing patterns for the north and south hemispheres.

32

Maybe we could get a cheap ice core by scraping a tool along one of these beasts longitudinally after it has shoaled at the far west end of the fjord (Espen?). Till at the very bottom would be especially informative. Its age could not be dated by layer stratigraphy because that is long gone but its thickness, minerals and certain isotopes like beryllium could be informative.

I would suspect that exposure to seawater would contaminate and parts per million / billion variations what I've cores try to measure...

33
Arctic sea ice / Re: 2015 sea ice area and extent data
« on: July 11, 2015, 10:28:51 AM »
Today's puzzle is the ESS. The (CT) area drops by -16k, but (NSIDC) extent .... has an increase of a whopping +45k7 !

That looks like a diffusion / shift by wind for the ice; nullschool shows slow wind towards ess, but faster winds in ess towards the coast.

Could this be simple divergence of fragmented ice? -- unusual fluctuations in *area* would be unphysical, but extent is just the shuffling of the ice fragments; especially with the purple "lost concentration %" segment nearby, it looks like that ice just got shuffled into pixels which had a little under 15% ice last pass.

34
Arctic sea ice / Re: The 2015 melting season
« on: May 31, 2015, 08:43:49 AM »
June 1st and July 1st have abnormally high drops in NSIDC extent which has been apparent back for the past 25 years.  Typically double the average for that fortnight.

Does anyone have an explanation for this?

I believe it's a change in false land-fast ice away from the arctic circle in areas considered to have completely melted out, so are set to 0, rather than a few residual pixels.

35
Arctic sea ice / Re: 2015 sea ice area and extent data
« on: May 24, 2015, 05:13:18 AM »
What are we to infer from that?. Perhaps that the thickness of the ice is within the margin of error of the measurement, which is too imprecise to tell us anything useful?
perhaps leads opening up could change the average thickness quite rapidly ; if this visualisation is tuned so that the volume of ice is correct, and there's a few hundred m of open water, then the "thickness" could fluctuate quite rapidly as the concentration of ice is diffused; if someone calculated the divergence of the motion field we could quantify that effect.

36
Arctic sea ice / Re: Seasonally ice free state
« on: May 23, 2015, 05:23:39 AM »
given that 15% is typically the threshold to determine "does this contain ice" i believe this is nice, defendable, and consistent definition;
an area is ice free when it drops below 15% concentration; it doesn't matter if it is a pixel, the entire basin, or the individual regions discussed here.

37
Arctic sea ice / Re: The 2015 melting season
« on: May 18, 2015, 11:37:06 PM »



This is crazy.

I really can't wait to see how it's going to turn out. I feel really ghoulish saying it but wow, it's pretty exciting.

(Not the most recent forecast, but the less extreme of the last 2 posted to this thread)
Looking at this it feels like the only source of very cold air (-10 or below) is air blown off of Greenland, and that isn't producing enough of a cooling effect to keep up with increased hearing due to decreased albedo. The boys show that the surface of the ice is around -2 c, and with broken I've everywhere the cold air would be having to work directly against the water,  which takes much more effort to freeze them simply cooling the surface of already frozen ice with a -10c core.

38
Arctic sea ice / Re: 2015 sea ice area and extent data
« on: May 09, 2015, 01:20:31 AM »
CT is back again!

My last prediction, calculated fro NSIDC sea ice concentration data, was:


Wed -36.6 11.797073


Today CT reported:

-36k6 11.796725

That is 0.3k off (about half a "pixel" at 100%)
Do you think that this indicates that numbers displayed to that precision present false certainty?
Perhaps the last 2 didgets could be removed, leaving the last significant figure at 0.1k, or less than 1/4 a pixel. Given the resolution and noise of the data, this difference could even be caused by floating point error accumulations on a even a perfect match of the actual underlying maths. I don't believe these last 2 figures tell us anything

39
Science / Re: Earthquakes and climate change
« on: May 09, 2015, 12:54:45 AM »
One problem with earthquakes is that stress continually builds up until released. When the pressure is close to release, even a small cause can trigger the inevitable.

Perhaps a week or month, or year sooner than the pressure build up would of done anyway.

40
Policy and solutions / Re: Renewables Reach a Tipping Point...
« on: May 06, 2015, 11:15:50 AM »
i don't think we will ever move to a predominantly localised generation due to pure economics of scale; eg: concentrated solar thermal allows relatively cheap energy buffering on a scale not easily achievable with smaller scale batteries.

The efficiency of various generations and storage scales with size, so there will always be a place for centralised power.

My previous comment was about how batteries as an independent technology are now cost viable for load leveling.

Generation wise, renewables have been cost efficient for a while, they just suffer from load balancing and dispatchability issues which had prevented penetration of renewables beyond about 20%, before grid instability becomes an issue.

Here in australia we are beginning to have some issues, as solar power generation peaks harder than power demand during the day, causing coal powerplants to become less profitable due to not being able to ramp up for base load during the day, because of the dip in power demand at midday.

One report i saw [citation needed, cant find it now] said that there was risk of brownouts on a 5-10 year horizion due to under-investment in baseload, when comparing expected demand to planed new generation capacity.

41
Policy and solutions / Re: Renewables Reach a Tipping Point...
« on: May 05, 2015, 10:57:51 AM »
One of the bigger factors preventing wide scale deployment of pure renewable power is dispatchability.

Recent technological advances in battery storage are helping to eliminate that, such that at current prices using batteries to buy off-peak, and sell peak power is possible to make a profit.

The mean cost of storage using batteries is still higher than the mean cost of electricity, but the spot price of electricity has enough volatility that batteries are now profitable.

see http://rameznaam.com/2015/04/30/tesla-powerwall-battery-economics-almost-there/ and http://rameznaam.com/2015/04/14/energy-storage-about-to-get-big-and-cheap/#FlowCAES

Moderate deployment of battery tech would have the interesting side-effect of putting a price cap on short term demand swings, and may actually make gas power plants less profitable, and filling in the low demand points would allow coal to run higher baseload, making it more profitable, so who knows what the net affect is.

either way, the long term effect of better battery technology is higher renewable penetration into the market without the grid destabilization we are beginning to see at high renewable %.

42
Arctic sea ice / Re: IJIS/JAXA
« on: April 24, 2015, 12:40:57 PM »
(April 23, 2015)down 90,195 km2

do you know what the earliest century break has been?

43
The forum / Re: threading
« on: April 19, 2015, 11:56:45 AM »
Can replies be tagged with a reference to the post to which they are a reply ? this reference could be NULL if there is no parent post ? (I have, of course, Usenet threading in mind ...)

sidd
quotes link to the thread they are quoting from, and i believe they work cross-board:

Here is PIOMAS, AMSR2-SIT and CRYOSAT compared.

44
there must be significant tension in the ice, as the the ice floats away after breaking; the only thing preventing that from happening earlier was the structural integrity of the ice.

does anyone know the the rate of water outflow under the ice? (it must be at least the speed we can see the surface ice moving...)

45
Arctic sea ice / Re: 2015 sea ice area and extent data
« on: March 07, 2015, 11:18:38 PM »
The interesting thing is that 2007 had 27 centuries, which is 2nd highest, and so for these two years, at least, there is a 100% inverse correlation between A) high number of centuries and B) low September minimum.
100% (inverse) correlation implies that all of the change in one of the values predicts all of the change in the other. While correlated, the relationship between count of century drops and overall magnitude of minimum isn't close to '100% inverse'.

Do you know how well this relationship works if extended to the top 10 years in rank?

46
Arctic sea ice / Re: The 2015 melting season
« on: March 05, 2015, 10:42:50 AM »
The new ice monitor appears to have a new feature : sea ice thickness derived from AMSR2. With as an extra bonus ice melting fraction as well.



Has anyone integrated the implied thickness by pixel area to get volume?

47
I recently found http://people.ee.ethz.ch/~luethim/pdf/script/pdg/chapter5.pdf -- on the physical properies of glaciers, and the numerical simulation of velocity and stress fields under various geometries.

Some of the thoughts here might aid discussions on future flow velocities of the various glaciers.

48
Arctic sea ice / Re: The 2015 melting season
« on: February 22, 2015, 09:23:17 AM »
Attempting to estimate "most rotten ice possible" leads to some interesting conclusions:

water is about 3% salt (32 grams/l)

25% frozen, salt retained -> remaining water 10% salt, freezing temp of the remaining -6c
40% frozen, salt retained -> remaining water 20% salt, freezing temp of the remaining water -16c.
60% frozen, -> remaining water is 45%, probably never frozen in the arctic ...

(if you assume only 50% of the salt is retained within the ice, half the unfrozen % of the above calculations. ie, 50/80% frozen)
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/meltpt.html
 10% salt solution was said to lower the melting point to -6°C  and a 20% salt solution was said to lower it to -16°C

49
Arctic sea ice / Re: The 2015 melting season
« on: February 21, 2015, 01:51:27 PM »
Jim, thanks for updating those graphs. You're right, there isn't that much of a difference between this year and last year at that bouy (and the drift has actually brought it almost back to where it was also)... I guess the follow up question is, how much of a difference does the air temp actually make then?

50
Arctic sea ice / Re: Daily SMOS Ice Thickness available.
« on: February 21, 2015, 12:07:20 AM »
Do you know how thick(>.6m), but broken ice would show as?

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