Arctic Sea Ice : Forum

Cryosphere => Arctic sea ice => Topic started by: Jim Hunt on May 28, 2019, 10:02:37 AM

Title: Basic questions about melting physics
Post by: Jim Hunt on May 28, 2019, 10:02:37 AM
Further to one (https://forum.arctic-sea-ice.net/index.php/topic,2707.msg201623) or two (https://forum.arctic-sea-ice.net/index.php/topic,143.msg201340.html#msg201340) recent discussions, here is a place to discuss the basic physics of freezing and melting sea ice.

Here are my own helpful hints on that thorny topic (amongst other things):

http://GreatWhiteCon.info/resources/arctic-sea-ice-explanations/
Title: Re: Basic questions about melting physics
Post by: Jim Hunt on May 28, 2019, 10:05:21 AM
With dramatic loss of old thick sea ice since 2010, I would expect that PIOMAS Sept. minimum would show stronger downward trend for 2010-2019, but while the long term trend is obvious, the last 10 years have been fairly flat.  Why doesn't loss of old thick ice show up more in PIOMAS Sept. minimum volume?
Title: Re: Basic questions about melting physics
Post by: Jim Hunt on May 28, 2019, 10:06:44 AM
Why doesn't loss of old thick ice show up more in PIOMAS Sept. minimum volume?

Because thermodynamics means the new ice grows to 2 meters plus thick across the Arctic Basin over every winter?

See the "Slow Transition" thread (https://forum.arctic-sea-ice.net/index.php/topic,933) for more details.
Title: Re: Basic questions about melting physics
Post by: Jim Hunt on May 28, 2019, 10:07:25 AM
RE #1866 "Because thermodynamics means the new ice grows to 2 meters plus thick across the Arctic Basin over every winter?"

   But that 2 meter new ice growth happens with or without old thick ice.  So it seems that a year with less returning old thick ice from previous year + summer freezing/thickening would result in less volume than an earlier year that had more returning old thick ice and gets the same amount of  summer freezing/thickening.

   The only way I can figure it is that with lower portion of old thick ice, the young ice that replaces it allows faster thickening.  Perhaps the thinner ice cover over water allows more heat loss and thus more thickening, whereas old thick ice is a better insulator and is less dynamic.
Title: Re: Basic questions about melting physics
Post by: Jim Hunt on May 28, 2019, 10:08:00 AM
   But that 2 meter new ice growth happens with or without old thick ice.  So it seems that a year with less returning old thick ice from previous year + summer freezing/thickening would result in less volume than an earlier year that had more returning old thick ice and gets the same amount of  summer freezing/thickening.
And indeed that has been the behavior. When old ice is lost, it is replaced with FYI and the result is a lower winter maximum volume trend. However the winter maximum also depends on the preceding summer minimum and on the effectiveness of autumn freezing. A look at the attached graph (day 120) shows how winter maximum volume has continued on a downward trend, with winter 2017 having an extreme record low. It also shows the correlation between summer minimum (day 260) and the following winter volume. The summer minimum result depends more heavily on weather and is more volatile.

Note: the data includes CAB, Beaufort, Chukchi, ESS, Laptev, Kara, CAA, Greenland Sea - the regions where MYI actually exists.

Note 2: do read the "slow transition" thread, very interesting.

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=143.0;attach=121348;image)
Title: Re: Basic questions about melting physics
Post by: Jim Hunt on May 28, 2019, 10:08:32 AM
Thick ice (of any age - rafting, etc. can make thick year old ice) will not grow 2 meters thicker during the winter when nearby thin ice will.  Attached chart shows an example for lake ice - how it grows less as thickness increases.  Ice, basically, is an insulator.

Decades ago, with much of the Arctic covered in MYI (multiyear ice), there was less volume increase in the central Arctic than during recent winters.

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=143.0;attach=121349;image)
Title: Re: Basic questions about melting physics
Post by: b_lumenkraft on May 28, 2019, 10:30:29 AM
Good move Jim!
Title: Re: Basic questions about melting physics
Post by: Flocke on May 28, 2019, 11:31:40 AM
Ice, basically, is an insulator.

Maybe depending on how you define insulator. Ice has a thermal conductivity of around 2.25 W/mK, water only 0.56 W/mK (both temperature dependant). The difference seems to be the missing convection in ice.
Title: Re: Basic questions about melting physics
Post by: Archimid on May 28, 2019, 01:32:01 PM
Quote
With dramatic loss of old thick sea ice since 2010, I would expect that PIOMAS Sept. minimum would show stronger downward trend for 2010-2019, but while the long term trend is obvious, the last 10 years have been fairly flat.  Why doesn't loss of old thick ice show up more in PIOMAS Sept. minimum volume?


The attached graph shows yearly volume gain and losses calculated from PIOMAS. After 2007 there is a significant increase in losses, but there is also a significant increase in gains. The increase in losses have many causes,  thinner ice being one of them. That's one way that the loss of thick ice shows.

I think the gains in volume are mostly explained by the loss of thick multiyear ice. That's where it really shows. Like Jim said and you correctly explained, thin ice grows to 2 meters very fast relative to ice growth beyond 2 meters.

See Lebedev formula:

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=1611.0;attach=88074;image)

The loss of thick ice implies there is much more thin ice, and when there is thin ice volume increases much faster.

Before I finish, I would like to echo Jim and Oren. Read the slow transition thread.
Title: Re: Basic questions about melting physics
Post by: interstitial on May 29, 2019, 11:23:32 AM
I am not certain I have calculations right so if I don’t let me know.


On the molecular scale freezing is an ordered stacking of water molecules so it makes sense that putting ions in the way makes that harder. On the macro scale we see evidence of that when the freezing point decreases.


It is common to see -1.8 C as freezing point of sea water but it is a bit more complicated. -1.8C corresponds to 29.52 g of salts/kg seawater. Molar ratios of  ions are listed below for 35g solute/kg seawater


0.546 moles Cl-
0.469 moles Na+
0.053 moles Mg2+
0.028 moles SO42-
0.0103 moles Ca2+
0.0102 moles K+


Anyway salinity in the artic near the surface varies from about 26 g of salts/kg seawater with a freezing point of -1.58C to 36 g of salts/kg seawater with a freezing point of -2.21C. For most purposes -1.8C is good enough.


But that is not really how sea ice freezes it starts at the temperature associated with the salinity of the water but the ice is nearly pure water. It rejects the salt when it freezes this increases the salinity of the water. So the water has to get a little bit colder to freeze the next bit. This process continues until the salty water gets trapped in ice. Eventually the last of the water freezes at about -21C.  This is first year Ice. It has pockets with high salt concentrations in it. Some of the pockets even most may not of frozen solid.


When the temperature climbs above -21C the pockets of high salt concentration melt first. The temperature is still too low to melt the pure ice.  Since Ice melts at the solid to liquid (or solid to gas interface but that is not relevant here) interface and as the salty water is in contact with pure ice and gets a little bit warmer it can melt a little bit more ice. This lowers the salinity and the ice can’t continue to melt until it gets warmer still.


The high concentration salt water can often burrow out of the pure ice before most of the pure ice melts. When the temperature drops again lower concentration salt water freezes inside. This is how multiyear ice is formed each freeze and thaw cycle of salty water can more and more salts out until it is pure ice with no salts. That makes the multiyear ice fresher and more melt resistant.

The melting temperature of the pure multiyear ice is dependent on the salinity of the surrounding liquid. When the pure multiyear ice melts the local salinity drops and the temperature must increase to melt more. That’s another reason it is more resistant to melt than first year ice.



So to succinctly answer the original question the purified ice melts at the temperature determined by the salinity of the surrounding water. That may be higher than -1.8C but it is not 0C.


Freezing point depression
https://en.wikipedia.org/wiki/Freezing-point_depression (https://en.wikipedia.org/wiki/Freezing-point_depression)
 presentation on chemical composition in sea water
https://www.soest.hawaii.edu/oceanography/courses/OCN623/Spring%202015/Salinity2015web.pdf
Title: Re: Basic questions about melting physics
Post by: Rich on May 29, 2019, 12:56:38 PM
I am not certain I have calculations right so if I don’t let me know.


On the molecular scale freezing is an ordered stacking of water molecules so it makes sense that putting ions in the way makes that harder. On the macro scale we see evidence of that when the freezing point decreases.


It is common to see -1.8 C as freezing point of sea water but it is a bit more complicated. -1.8C corresponds to 29.52 g of salts/kg seawater. Molar ratios of  ions are listed below for 35g solute/kg seawater


0.546 moles Cl-
0.469 moles Na+
0.053 moles Mg2+
0.028 moles SO42-
0.0103 moles Ca2+
0.0102 moles K+


Anyway salinity in the artic near the surface varies from about 26 g of salts/kg seawater with a freezing point of -1.58C to 36 g of salts/kg seawater with a freezing point of -2.21C. For most purposes -1.8C is good enough.


But that is not really how sea ice freezes it starts at the temperature associated with the salinity of the water but the ice is nearly pure water. It rejects the salt when it freezes this increases the salinity of the water. So the water has to get a little bit colder to freeze the next bit. This process continues until the salty water gets trapped in ice. Eventually the last of the water freezes at about -21C.  This is first year Ice. It has pockets with high salt concentrations in it. Some of the pockets even most may not of frozen solid.


When the temperature climbs above -21C the pockets of high salt concentration melt first. The temperature is still too low to melt the pure ice.  Since Ice melts at the solid to liquid (or solid to gas interface but that is not relevant here) interface and as the salty water is in contact with pure ice and gets a little bit warmer it can melt a little bit more ice. This lowers the salinity and the ice can’t continue to melt until it gets warmer still.


The high concentration salt water can often burrow out of the pure ice before most of the pure ice melts. When the temperature drops again lower concentration salt water freezes inside. This is how multiyear ice is formed each freeze and thaw cycle of salty water can more and more salts out until it is pure ice with no salts. That makes the multiyear ice fresher and more melt resistant.

The melting temperature of the pure multiyear ice is dependent on the salinity of the surrounding liquid. When the pure multiyear ice melts the local salinity drops and the temperature must increase to melt more. That’s another reason it is more resistant to melt than first year ice.



So to succinctly answer the original question the purified ice melts at the temperature determined by the salinity of the surrounding water. That may be higher than -1.8C but it is not 0C.


Freezing point depression
https://en.wikipedia.org/wiki/Freezing-point_depression (https://en.wikipedia.org/wiki/Freezing-point_depression)
 presentation on chemical composition in sea water
https://www.soest.hawaii.edu/oceanography/courses/OCN623/Spring%202015/Salinity2015web.pdf

This doesn't make sense.

Sea water contains H2O molecules and NaCl dissolved in a solution.

When sea water freezes, the hydrogen bonds between the water molecules spread out into a fixed lattice structure and the NaCl falls out of the solution into the enlarged spaces between the hydrogen bonds.

Ice is less dense than liquid water. Fewer molecules in a given volume means more space between molecules for the salt / brine to exit the the lattice structure.

There is no frozen salt water in the Arctic. The ice is like a building made out of water molecules. Just as you would not consider a human inside of a building to be part of the building, a salt molecule inside of an ice lattice is not part of the ice.

The "screws" that hold the ice building together are hydrogen bonds. Weaker than covalent bonds inside the water molecules itself, these are intermolecular attractions between positively charged H and negatively charged O atoms.

To unscrew the connections in the building (melt the ice), it is necessary to apply heat to those H-O-H intermolecular bonds. The presence or absence of salt in the vicinity is irrelevant to the properties of the screws holding the H2O house together.

At 1 atm. of pressure, the house is going to fall apart at 0C.
Title: Re: Basic questions about melting physics
Post by: oren on May 29, 2019, 04:28:45 PM
Rich, at the risk of exposing my ignorance, I think you got it wrong there. At the bottom, the ice is floating is salt water, and will melt below 0C. At the top you may be correct.
Title: Re: Basic questions about melting physics
Post by: Rich on May 29, 2019, 05:12:02 PM
Rich, at the risk of exposing my ignorance, I think you got it wrong there. At the bottom, the ice is floating is salt water, and will melt below 0C. At the top you may be correct.

I said the ice will melt at 0C at 1 atm of pressure. This describes surface conditions.

Under water,  pressure increases and changes the melting point.

Ice at depth in a fresh water lake will also melt at temps below 0C due to increased pressure.
Title: Re: Basic questions about melting physics
Post by: Tor Bejnar on May 29, 2019, 06:39:39 PM
Sorry for the aside, but there can be a problem with
Quote
you would not consider a human inside of a building to be part of the building
   When calculating the energy needs of a building (e.g., heating and A/C), the humans can be a significant component.  (Years ago I did public building energy audits.)

I have no clue, however, about salt water freezing and 'fresh' ice thawing issues.
Title: Re: Basic questions about melting physics
Post by: Observer on May 29, 2019, 07:04:00 PM
Thank you for starting this thread. As someone with less knowledge of the natural sciences than of political (unnatural?) science I have many questions about the behavior of water and ice. I have been reading some threads, mostly concerning extent and current season, for a few years. As my curiosity about the physics of water and aqueous solutions has grown, I joined with the hope of asking questions such as those addressed above. This thread and the information have provided above is much appreciated.
Title: Re: Basic questions about melting physics
Post by: oren on May 29, 2019, 07:15:29 PM
Sorry for the back and forth despite my being a layman on this subject. But: I am talking about ice touching salt water, not at depth but nearly at the surface where pressure change is negligible. It is "known" that salt hastens the melting of ice. In other words lowering the melting point, even if the ice is pure freshwater.
Can some expert step in?  ???
Title: Re: Basic questions about melting physics
Post by: johnm33 on May 29, 2019, 11:54:53 PM
From W.Ds. blog "New sea ice starts from 3 important concurring factors: -1.8 C water, little or no sea waves and colder than -11 C surface temperatures "
http://eh2r.blogspot.com/2016/10/new-sea-ice-starts-from-3-important.html
So away from the shore much colder than-11C probably important.
What's the rate of sublimation from ice at various air temps.? since there can't be an energetic 'free lunch' how much impact does this have on ice formation/cooling.
Title: Re: Basic questions about melting physics
Post by: petm on May 29, 2019, 11:57:06 PM
I'm no expert but I know that it's common practice to throw salt on e.g. roads and sidewalks to melt the ice. Presumably sea ice in contact with sea water at a different salinity would have a melting temperature somewhere between the two. https://phys.org/news/2019-02-salt-doesnt-ice-winter-streets.html
Title: Re: Basic questions about melting physics
Post by: interstitial on May 30, 2019, 03:15:25 AM
Temperature is a measure of kinetic energy of the system. Kinetic energy includes translational rotational and vibrational modes.
Temperature does not consider potential energy of the system.  Potential energy includes the energy of bonding. This include strong bonding like ionic and covalent as well as weaker interactions such as hydrogen bonding, vander wahls interactions and others.
Pure water has a higher potential energy than pure ice. If the system is at equilibrium the water and ice have the same kinetic energy namely temperature. The difference in energy is the potential energy of hydrogen bonding you mentioned.
Salt water has a lower potential energy than pure water because of the interactions between ions and water molecules. This interaction is weaker than h bonding so salt water has a higher potential energy then pure ice.

Potential energy of each system from high to low is pure water, salt water and then pure ice. I am not talking about temperature here just bonding energies. 
The potential energy of the saltwater changes with concentration higher concentrations of ions gives lower potential energy of the system.
the difference in potential energy of a saltwater pure ice system is lower than the potential energy difference between pure water and pure ice. Due to conservation of energy potential energy can be converted from kinetic energy. So the kinetic energy required to melt the saltwater pure ice system is lower than for the pure water pure ice system. In other words saltwater pure ice system melts at a lower temperature than pure water pure ice system.
Title: Re: Basic questions about melting physics
Post by: binntho on May 30, 2019, 07:11:36 AM
I should think that Oren is right - salt at the boundary between ice (even if made from pure water) will lower the melting point of that ice. The salt in the sea water causes the ice to melt at a lower temperature.
Title: Re: Basic questions about melting physics
Post by: binntho on May 30, 2019, 07:16:36 AM
Another thing that I've been thinking about lately, given the discussions re. insolation and melt ponds:

For those familiar with snow and ice, seeing ice melt in direct sunlight even when the air temperature is below zero is not unknown. Ice (and snow) will slowly sublimate directly into vapor in dry air, and sunlight helps this process along.

I've also noticed myself how snow that has lying for some time without melt will still have different surface characteristics depending on whether it has been exposed to direct sunlight. In the shadows, the snow is loose while in direct sunlight it seems to gain a brittle crust.

So my point is: Direct sunlight will cause surface melt and surface changes, even if air temperatures are below zero.
Title: Re: Basic questions about melting physics
Post by: wdmn on May 30, 2019, 07:25:57 AM
This is a question/comment about enthalpy of fusion and albedo. It could probably go elsewhere but fits here too, I think.

Ice at 0 Celsius takes a lot of energy to melt from latent heat.

According to wikipedia, it takes 333.55 kJ of energy to melt 1 kg of ice, but only 83.6 kJ of energy to increase the temperature of 1kg of water by 20 degrees celsius. That means that 333.55 kJ of energy raises the temperature of water ~80 degrees C.

Discussion around decreasing arctic sea ice tends to be about albedo. But doesn't decreasing sea ice also mean an increasing amount of available latent heat to warm the oceans/adjacent land? And what might that mean as we approach <1mk2 of summer sea ice? It seems like it would be simple math to quantify the excess heat going into the exposed ocean, and I wonder if anyone has done that already?

Thanks
Title: Re: Basic questions about melting physics
Post by: binntho on May 30, 2019, 07:50:57 AM
Definitely during summer the latent heat uptake of melting ice keeps the temperature hovering just over the 0 mark as can be seen on the DMI graphs. There are also temperature spikes in autumn when the freezing gets going, with release of latent heat that presumably is lost out through the atmosphere.

On the other hand, the ice insulates the underlying sea from losing too much heat to the atmosphere, so I´m not at all sure what the net result of a more-or-less ice free arctic would be.
Title: Re: Basic questions about melting physics
Post by: wdmn on May 30, 2019, 08:35:50 AM
Thank you. Always something to make things more complex...

But there's got to be some way to think about this numerically. I wonder if anyone's done it? Anyway, I'll give it some more thought.
Title: Re: Basic questions about melting physics
Post by: interstitial on May 30, 2019, 10:18:29 AM
This is a question/comment about enthalpy of fusion and albedo. It could probably go elsewhere but fits here too, I think.

Ice at 0 Celsius takes a lot of energy to melt from latent heat.

According to wikipedia, it takes 333.55 kJ of energy to melt 1 kg of ice, but only 83.6 kJ of energy to increase the temperature of 1kg of water by 20 degrees celsius. That means that 333.55 kJ of energy raises the temperature of water ~80 degrees C.

Discussion around decreasing arctic sea ice tends to be about albedo. But doesn't decreasing sea ice also mean an increasing amount of available latent heat to warm the oceans/adjacent land? And what might that mean as we approach <1mk2 of summer sea ice? It seems like it would be simple math to quantify the excess heat going into the exposed ocean, and I wonder if anyone has done that already?

Thanks


the temperature is kinetic energy and the latent heat of fusion is potential this energy can and readily does converts from one to the other but that doesn't change the total energy of the system.


if you think about the water and ice of the ocean as a system with thorough mixing and no change in energy to or from the system the temperature will be at the freezing point and there will be a fixed amount of ice. Of course the ocean isn't perfectly mixed but it is easier to think about.



Adding energy to the ocean system can decrease the amount of ice in the ocean or increase the temperature. If it is not thouroghly mixed it can do both at the same time at different locations.


So whats really important is the energy imbalance of the system overtime. Solar energy from space can add energy to the system and warm objects emit energy in the infrared to space. Solar energy entering the atmosphere is mostly predictable based on the season. their is some variation of in solar cycles but that is not as significant as the season in the arctic. The amount of energy that an object radiates is a function of material and temperature. The albedo of the atmosphere and ice are harder to predict and control how much energy makes it in and out of the system.   


Yes in general someone has calculated how much energy is tied up in melting ice but it is not very useful as it is a simple calculation of volume of ice melted times the latent heat of fusion. If you can predict energy flow over time it would be relatively straight forward to predict the volume.


On a related note volume numbers are mostly based on models and little on direct measurement. Models can only get better with lots of direct measurement. Only the thinnest of ice can be measured by satellite. Occasionally people go to measure ice thickness but that isn't nearly enough and only produces one data point at a time. Because of this their is large variability in the thickness data from different models. They are working on a system measure thickness from below I believe using sonar but I am not sure.
Title: Re: Basic questions about melting physics
Post by: petm on May 30, 2019, 02:36:54 PM
According to wikipedia, it takes 333.55 kJ of energy to melt 1 kg of ice, but only 83.6 kJ of energy to increase the temperature of 1kg of water by 20 degrees celsius. That means that 333.55 kJ of energy raises the temperature of water ~80 degrees C.

Yes, and once that energy becomes available, what happens to the weather? In vulnerable regions, could some storms mix up to the surface warm Atlantic waters from below the halocline? If so, could this become a positive feedback, further increasing storm intensity and subsequent mixing? And what could be the result of such a feedback on global atmospheric circulation patterns, winter re-freeze, etc.?

At some point, the Arctic will become ice-free year-round. This will very probably require centuries more warming, but no one really knows how long or the path that will take us there.
Title: Re: Basic questions about melting physics
Post by: Glen Koehler on May 30, 2019, 03:28:47 PM
     Simpler framing of the original question makes the answer easier to see.
Original mystery (to me at least) was why wasn't PIOMAS volume decreasing in sync  with loss of old think ice?

    My new dope-slap-forehead observation - winter maximums have declined, but not as much as summer minimums (maxima, minima for those of you who remember 7th grade Latin).  Thus it is clear that winter refreeze has increased along with declining summer minima.  Not enough to fully compensate for increased summer losses, but enough to reduce their impact on winter maxima.
 
   As helpfully pointed out by Oren and others, that is indeed the case.  As to why winter ice gain increases with declining summer minima, two mechanisms are
1) thinner ice is able to increase thickness faster, and
2) ice cover acts as an insulator, thus less insulation means faster cooling in the following fall/winter. 
     There may be other mechanisms in addition to 1 and 2 (changes in cloud cover or wind patterns?).  And within 1 and 2 there are more detailed explanations for how/why they work.

   So nothing new here in this post!  I just thought anybody who was also puzzled by the original question, lack of 1:1 correlation between dramatic loss of older, thick ice, and the more subtle (but consistent trend) of PIOMAS ice volumes would find a bit of catch up and summary useful. 

   Two particularly interesting and useful points that arose -
    a) thick ice does not necessarily mean old ice.  Thinner fractured ice floes are more susceptible to being transported by wind or currents into thicker piles.
   b) salinity differences account for why older ice is more resistant to melt; and younger, saltier ice is less resistant to melt (though not everybody seems to agree about the chemistry at the molecular level).
   
Title: Re: Basic questions about melting physics
Post by: gerontocrat on May 30, 2019, 03:30:08 PM

But there's got to be some way to think about this numerically. I wonder if anyone's done it?
I like this example from the Polar Science Center, which brings in both the overall vast energy quantities involved and a dim light bulb at the micro level.

http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/
Quote
Perspective: Ice Loss and Energy
It takes energy to melt sea ice. How much energy? The energy required to melt the 16,400 Km3 of ice that are lost every year (1979-2010 average) from April to September as part of the natural annual cycle is about 5 x 1021 Joules. For comparison, the U.S. Energy consumption for 2009 (www.eia.gov/totalenergy) was about 1 x 1020 J. So it takes about the 50 times the annual U.S. energy consumption to melt this much ice every year. This energy comes from the change in the distribution of solar radiation as the earth rotates around the sun.

To melt the additional 280 km3 of sea ice, the amount we have have been losing on an annual basis based on PIOMAS calculations, it takes roughly 8.6 x 1019 J or 86% of U.S. energy consumption.

However, when spread over the area  covered by Arctic sea ice, the additional energy required to melt this much sea ice is actually quite small. It corresponds to about 0.4 Wm-2 . That’s like leaving a very small and dim flashlight bulb continuously burning on every square meter of ice. Tracking down such a small difference in energy is very difficult, and underscores why we need to look at longer time series and consider the uncertainties in our measurements and calculations.
Title: Re: Basic questions about melting physics
Post by: binntho on May 30, 2019, 04:16:06 PM
It's not a simple matter!

       Two particularly interesting and useful points that arose -
    a) thick ice does not necessarily mean old ice.  Thinner fractured ice floes are more susceptible to being transported by wind or currents into thicker piles.
   b) salinity differences account for why older ice is more resistant to melt; and younger, saltier ice is less resistant to melt (though not everybody seems to agree about the chemistry at the molecular level).

I think that a) is a very useful insight, but b) is perhaps not wholly correct. Younger ice will tend to be more porous and even contain pockets of brine, both of which help with faster melting.

And I don't think there is any real disagreement abut the molecular-level chemistry - it's fairly basic after all. But applying molecular-level chemistry to floating sea ice is perhaps a bit more tricky.
Title: Re: Basic questions about melting physics
Post by: LRC1962 on May 30, 2019, 09:57:31 PM
https://nsidc.org/cryosphere/seaice/index.html (https://nsidc.org/cryosphere/seaice/index.html)
Quote
Can you drink melted sea ice?
New ice is usually very salty because it contains concentrated droplets called brine that are trapped in pockets between the ice crystals, and so it would not make good drinking water. As ice ages, the brine eventually drains through the ice, and by the time it becomes multiyear ice, nearly all of the brine is gone. Most multiyear ice is fresh enough that someone could drink its melted water. In fact, multiyear ice often supplies the fresh water needed for polar expeditions. See Salinity and Brine in the Characteristics section for more information.
https://nsidc.org/cryosphere/seaice/characteristics/brine_salinity.html (https://nsidc.org/cryosphere/seaice/characteristics/brine_salinity.html)
Quote
Fresh water freezes at 0 degrees Celsius (32 degrees Fahrenheit), but the freezing point of sea water varies. For every 5 psu increase in salinity, the freezing point decreases by 0.28 degrees Celsius (0.5 degrees Fahrenheit); thus, in polar regions with an ocean salinity of about 32 psu, the water begins to freeze at -1.8 degrees Celsius (28.8 degrees Fahrenheit). The Arctic Ocean is generally fresher than other oceans, somewhere between 30 and 34 psu, but salinity levels vary by region, and areas with strong river inflow may have even lower salinity.
Title: Re: Basic questions about melting physics
Post by: Glen Koehler on May 31, 2019, 01:59:15 AM
Doing some homework by reading the Slow Transition forum. https://forum.arctic-sea-ice.net/index.php/topic,933, 
    To expedite access to the take home points for others still getting their arms around the original question, here are some selected items from that discussion that provide a plausible explanation.  The quotes are from 2014 and I think they hold up well 5 years later.

1. Chris Reynolds #6  July 2014
"...2007 and 2012 saw massive gains in volume despite delays to the onset of melt. This is because the rate of growth of ice for open water and thin ice is extremely fast. The following graphic is from Thorndike 1975."

(https://imagizer.imageshack.com/v2/320x240q90/921/mohdgL.png)

2. Chris Reynolds #49  July 2014
"…the contention that future April Arctic Ocean volume will be set by ice growing to thermodynamic equilibrium thickness (TET) from September to April, then further volume loss events leading to net thinning of the pack and enabling further increases of melt season losses of volume look unlikely.   Because with a mainly first year ice pack further drops in volume in years like 2012 will be followed by rapid recoveries to the volume implied by the TET around the time of those drops within a few years at most (Tietsche et al)."

3. From Chris Reynolds  Dosbat Blog.  http://dosbat.blogspot.com/2014/07/the-slow-transition.html
    "I am becoming convinced that the approximate levelling of PIOMAS volume over the last few winters is telling us that the pack is becoming dominated by FYI, whose thermodynamic equilibrium thickness is largely setting the peak volume in April."

    "I was persuaded that the loss of MYI represented energy that would then have to go into melting FYI after the MYI had declined. However because FYI regrows in the winter it vents this notional energy. The energy that once went into melting MYI is thus vented into the atmosphere and radiated to space in autumn/winter."
Title: Re: Basic questions about melting physics
Post by: Tor Bejnar on May 31, 2019, 02:35:06 AM
I 'found' this 1991 paper Physical and Dynamic Properties of Sea Ice in the Polar Oceans (https://apps.dtic.mil/dtic/tr/fulltext/u2/a256303.pdf) linked in a 2017 Barneo post (https://forum.arctic-sea-ice.net/index.php/topic,1905.msg108637.html#msg108637).  I've been reading about ice salinity and the various mechanisms that desalinate ice. (40+ pages)
Title: Re: Basic questions about melting physics
Post by: Archimid on May 31, 2019, 02:54:31 AM
Quote
"The energy that once went into melting MYI is thus vented into the atmosphere and radiated to space in autumn/winter."

And that shows as much warmer fall/winter temperatures, and in some cases a delay in freezing until the extra atmospheric and ocean heat is "vented".

See the fall/winter of 2016/17

https://www.climate.gov/news-features/featured-images/2017-arctic-report-card-extreme-fall-warmth-drove-near-record-annual

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Focean.dmi.dk%2Farctic%2Fplots%2FmeanTarchive%2FmeanT_2016.png&hash=ed3bc1964e488b5d83cfae05c243a1bc)

This is where I believe the slow transition theory has the highest chance for failing early.
Title: Re: Basic questions about melting physics
Post by: oren on May 31, 2019, 03:09:42 AM
Doing some homework by reading the Slow Transition forum. https://forum.arctic-sea-ice.net/index.php/topic,933, 
    To expedite access to the take home points for others still getting their arms around the original question, here are some selected items from that discussion that provide a plausible explanation.  The quotes are from 2014 and I think they hold up well 5 years later.
While Chris's theory was brilliant and I think very innovative for its time, the winter of 2016-2017 showed that it was not foolproof. Refreeze was so delayed and autumn temps so high (as noted by Archimid above) that April saw a record low volume in the Arctic Ocean. I cannot manage to recreate Chris's numbers but here's a chart showing PIOMAS volume for the inner basin plus CAA and Greenland Sea for day 120, with 2010-2014's flatline highlighted. The break below 18k km3 clearly shows that the transition may not be as slow as postulated/hoped for - because the FYI may not thicken as much as it used to.
Title: Re: Basic questions about melting physics
Post by: Dharma Rupa on June 02, 2019, 07:27:47 PM
My memory of the slow transition thread is that the main questionmark was the future behavior of water vapor.  My contention at the time, and to this day, is that the Arctic is in transition from a desert climate to a maritime climate.  The Arctic nights are going to get cloudier and lose less heat to space.  I think the transition from desert to maritime has already happened rather abruptly in late December 2015, and we are now simply waiting for enough ice to melt in Summer that it cannot reach thermal equilibrium the following Winter.

Title: Re: Basic questions about melting physics
Post by: Dharma Rupa on June 02, 2019, 07:29:18 PM
Sorry for the back and forth despite my being a layman on this subject. But: I am talking about ice touching salt water, not at depth but nearly at the surface where pressure change is negligible. It is "known" that salt hastens the melting of ice. In other words lowering the melting point, even if the ice is pure freshwater.
Can some expert step in?  ???

How about someone who has made ice cream?
Title: Re: Basic questions about melting physics
Post by: johnm33 on June 02, 2019, 09:47:03 PM
" Salty water freezes at a lower temperature than plain water. But the ice is made of plain water, so it melts at 0 degrees Celsius. Since the ice keeps melting, but the water no longer freezes (because there is only salt water, which doesn't freeze at 0 degrees), the temperature goes down.

The heat gained by the ice as it melts is no longer offset by the heat given up by freezing water (since the water is no longer freezing back onto the ice). The heat gain has to come from somewhere else. It comes from the ice cream and your hands.

The sodium and chlorine in the salt split apart into charged ions, and these ions attract water molecules to form weak chemical bonds.

The resulting compound has a freezing point of -21.1 degrees Celsius (-5.98 degrees Fahrenheit). This is 21.1 degrees colder than ice (37.98 degrees Fahrenheit colder than ice). " from https://sci-toys.com/scitoys/scitoys/thermo/ice_cream/ice_cream.html
So it seems that any windborne salt could 'suck' heat out of the wet surface layer of ice creating I presume a drop of brine at>-0C but cooling the remainder down to a possible -21C but no further effect on saltwater.
Title: Re: Basic questions about melting physics
Post by: SteveMDFP on June 02, 2019, 11:43:56 PM

The resulting compound has a freezing point of -21.1 degrees Celsius (-5.98 degrees Fahrenheit). This is 21.1 degrees colder than ice (37.98 degrees Fahrenheit colder than ice). " from https://sci-toys.com/scitoys/scitoys/thermo/ice_cream/ice_cream.html
So it seems that any windborne salt could 'suck' heat out of the wet surface layer of ice creating I presume a drop of brine at>-0C but cooling the remainder down to a possible -21C but no further effect on saltwater.

Windborne salt?  On the forum somewhere recently it was stated that 2/3 of overall melt is bottom surface melt.  Only 1/3 is top surface.  Salty seawater will melt the bottoms of floes until an equilibrium temp is reached.  Although the freshening of the seawater by melt will slow the process, there's always some mixing of seawater going on, and also conduction of heat from another meter or so down.
Title: Re: Basic questions about melting physics
Post by: Phil. on June 04, 2019, 02:02:19 PM
Temperature is a measure of kinetic energy of the system. Kinetic energy includes translational rotational and vibrational modes.
Temperature does not consider potential energy of the system.  Potential energy includes the energy of bonding. This include strong bonding like ionic and covalent as well as weaker interactions such as hydrogen bonding, vander wahls interactions and others.
Pure water has a higher potential energy than pure ice. If the system is at equilibrium the water and ice have the same kinetic energy namely temperature. The difference in energy is the potential energy of hydrogen bonding you mentioned.
Salt water has a lower potential energy than pure water because of the interactions between ions and water molecules. This interaction is weaker than h bonding so salt water has a higher potential energy then pure ice.

Potential energy of each system from high to low is pure water, salt water and then pure ice. I am not talking about temperature here just bonding energies. 
The potential energy of the saltwater changes with concentration higher concentrations of ions gives lower potential energy of the system.
the difference in potential energy of a saltwater pure ice system is lower than the potential energy difference between pure water and pure ice. Due to conservation of energy potential energy can be converted from kinetic energy. So the kinetic energy required to melt the saltwater pure ice system is lower than for the pure water pure ice system. In other words saltwater pure ice system melts at a lower temperature than pure water pure ice system.

The other important factor in the solutions is entropy which can have a bigger contribution to Free Energy than enthalpy in such mixture.  The 'order' due to hydrogen bonding around the ions being a major contributor in some biological systems the 'order' effects can be the drivers rather than enthalpy differences:  DeltaG=DeltaH-T*DeltaS
Title: Re: Basic questions about melting physics
Post by: Tor Bejnar on July 25, 2019, 05:41:45 PM
There was some discussion on a 'main' thread abut 850 temperatures vs. 2m temperatures.

Towards our mutual understanding of whys and wherefores, I offer the following.  I know extremely little about atmospheric science, so cannot offer (really) anything, but hope those who do will share more, even extensively!

An internet search led me to WeatherPrediction.com (http://www.theweatherprediction.com/habyhints/278/). 
Quote
FORECASTING SURFACE HIGH USING 850-mb TEMP 

METEOROLOGIST JEFF HABY

LIMITATIONS

 Forecasting the surface high using the 850-mb temperature has been a popular forecasting technique. First Iwill go over the limitations of using this method:

 1. Method does not work on cloudy days or days with afternoon precipitation

 2. There is a tendency that temperature will be higher than predicted on days the wind is light and will be lower than predicted on days the wind is strong. This is because the low level wind effectsthe depth of mixing.

 3. Method assumes air is mixed only between the surface and 850 mb. If the air mixes to a height significantly above or below 850 mb the technique will not work accurately.

 4. Method does not account for elevation. High elevation regions have a greater chance of mixing air that is above 850 mb.

 5. Daylight hours effect accuracy. There is a significant difference in daylight hours between the warm and cool season.

 6. Method only works in a barotropic atmosphere. Fronts or differential advection will contaminate technique.

 7. Method does not work well in regions with complex topography or near mesoscale temperature gradients such as coastal areas, very hilly areas, and areas near large lakes.

 The method works best in locations near sea level, in the warm season, on barotropic days, with flat topography, on moderate windy cloud-free days. If any of these conditions are not met then take that into account on the temperature prediction.

THE METHOD

 The method itself is very easy. Method needs to be done on a Skew-T to ensure accuracy. From the morning sounding, note the 850-mb temperature. Take a parcel of air at 850 mb using the 850-mb temperature and bring it dry adiabatically to the surface. The temperature of this parcel after it is brought to the surface will estimate the high temperature for the day.
[minor editing - some words became 'run-on words' when copied]
Title: Re: Basic questions about melting physics
Post by: Rich on July 25, 2019, 06:39:57 PM
Thank you Tor !!
Title: Re: Basic questions about melting physics
Post by: Tor Bejnar on July 25, 2019, 06:40:13 PM
Here is an apparent conflict between physics and 'experience'.
Quote
You do know that there are no "sources" of cold?

Of course there are sources of cold. If I have a glass of warm water and I need a source of cold I just go get some ice and throw it in.
<Snippage>
OK, while creative, not really A Thing.

You don't really have "sources of cold" any more than you have "sources of vaccuum".  What "cold" indicates is a difference in enthalpy - net heat content components of a system, and thanks to the laws of thermodynamics heat will attempt to equilibrate across it - thus your ice cubes melting. 

There wasn't any "cold source" here, just the heat of varying levels being redistributed.

This does bring me to a point which I feel people have been overlooking.  It unfortunately is one for which we probably have the least instrumentation for - net enthalpy of the Arctic ocean and surrounding seas.

*This* will be the key factor in the tipping point.
<<a great deal of material removed - it is basically Arctic-specific.>>

In the northern hemisphere mid-latitudes when a 'cold North wind' blows, it gets colder.  A balloon floating in that cold air physically goes south, so I say the cold air came south too.  The source of that cold air was 'someplace' north of me.  Yes, it is a 'distribution' thing, but in the local sense, it sure seems like there is a 'source'.  The balloon 'came from the north', why can't the 'cold'?  OK: the 'air packet' came from the north, and it happened to be cold.  That air packet is cold because it lost its heat to the heavens [angels, I guess, lug the heat up when taking breaks from harp playing].  So, a source for the air, but not the cold.

(Those drink-cooling ice cubes were clearly made by a 'heat-redistribution machine'.)
How wrong did I go, physicists of the world?
Title: Re: Basic questions about melting physics
Post by: DrTskoul on July 25, 2019, 07:34:30 PM
From a mathematical point of view, similar to a current of "holes" in semiconductors , a current and a source of "cold" for a higher level ( not deep) understanding are perfectly valid as long as one appreciates the simplifying assumptions. For me as a chemical engineer, I can solve the problem and give you the same result regardless the framework.
Title: Re: Basic questions about melting physics
Post by: binntho on July 26, 2019, 07:15:30 AM
Here is an apparent conflict between physics and 'experience'.
Quote
You do know that there are no "sources" of cold?

Of course there are sources of cold. If I have a glass of warm water and I need a source of cold I just go get some ice and throw it in.
<Snippage>
OK, while creative, not really A Thing.

You don't really have "sources of cold" any more than you have "sources of vaccuum".  What "cold" indicates is a difference in enthalpy - net heat content components of a system, and thanks to the laws of thermodynamics heat will attempt to equilibrate across it - thus your ice cubes melting. 

There wasn't any "cold source" here, just the heat of varying levels being redistributed.

This does bring me to a point which I feel people have been overlooking.  It unfortunately is one for which we probably have the least instrumentation for - net enthalpy of the Arctic ocean and surrounding seas.

*This* will be the key factor in the tipping point.
<<a great deal of material removed - it is basically Arctic-specific.>>

In the northern hemisphere mid-latitudes when a 'cold North wind' blows, it gets colder.  A balloon floating in that cold air physically goes south, so I say the cold air came south too.  The source of that cold air was 'someplace' north of me.  Yes, it is a 'distribution' thing, but in the local sense, it sure seems like there is a 'source'.  The balloon 'came from the north', why can't the 'cold'?  OK: the 'air packet' came from the north, and it happened to be cold.  That air packet is cold because it lost its heat to the heavens [angels, I guess, lug the heat up when taking breaks from harp playing].  So, a source for the air, but not the cold.

(Those drink-cooling ice cubes were clearly made by a 'heat-redistribution machine'.)
How wrong did I go, physicists of the world?
In daily parlance, having a "source" of cold is quite normal. Having just had my air-conditioner fixed has made me thankful for that particular source of cold when I'm trying to sleep.

But when talking about larger systems, hemispheric and global weather for example, one has to be clear that  there is never a source of cold, only sources of heat.

I started this whole "source of cold" discussion after reading a post by Archimid about how there were this and that source of cold that could have this and that effect on the Arctic. That was so obviously a wrong way to talk about weather and climate that I had to ask, and he has been strangely reticent in agreeing with the physics.

I also wanted to point out (and perhaps get a little bit closer to the topic of this thread? Edit: Didn't realize that this was a new and more appropriate thread for this sort of thing) that space is a great sucker of warmth, a massive sink of heat, and would be by very far the hugest "source of cold" ever.

And the Arctic, during the winter months, loses massive amounts of heat to space and will continue to do so. Losing summer ice is only going to increase this heat loss, and if there ever is an equitable climate, this heat loss is going to get even bigger, leading to a fall in temperatures elsewhere.

Which all counts as a huge negative feedback, reducing the speed of global warming and generally working to cool the planet down.

Of course, there is another, very potent positive feedback in losing Arctic ice, so an ice-free Arctic ocean will presumably have a significant net effect of warming rather than cooling the planet. But never forget that negative feedback that's going to have it's say as well!

And once all the ice is gone, the positive feedback of losing ice stops. But the negative feedback of losing heat just keeps growing with increasing temperatures. How this will all play out is a total mystery to me, but some people seem to think they've got it all worked out.
Title: Re: Basic questions about melting physics
Post by: bill kapra on August 21, 2019, 01:57:10 AM
Hey folks,

Longtime lurker. Soft condensed matter guy. Just starting to look at sea ice and stumbled across this. FWIW:

Critical behavior of transport in sea ice

Author links open overlay panelK.M.Golden
Show more
https://doi.org/10.1016/j.physb.2003.08.007Get rights and content
Abstract
Geophysical materials such as sea ice, rocks, soils, snow, and glacial ice are composite media with complex, random microstructures. The effective fluid, gas, thermal, and electromagnetic transport properties of these materials play an important role in the large-scale dynamics and behavior of many geophysical systems. A striking feature of such media is that subtle changes in microstructural characteristics can induce changes over many orders of magnitude in the transport properties of the materials, which in turn can have significant large-scale geophysical effects. For example, sea ice, which mediates energy transfer between the ocean and atmosphere, plays a key role in global climate, and serves as an indicator of climatic change, is a porous composite of ice, brine and gases. Relevant length scales range from microns and millimeters for individual brine structures, to centimeters and meters for connected brine channels across floes, to hundreds of kilometers across an ice pack. Sea ice is distinguished from many other porous composites, such as sandstones or bone, in that its microstructure and bulk material properties can vary dramatically over a relatively small temperature range. The fluid permeability of sea ice ranges over six orders of magnitude for temperatures between 0°C and −25°C. Moreover, small changes in brine volume fraction around a threshold value of about 5%, corresponding to variations in temperature around a critical point of about −5°C, control an important transition between low and high fluid permeability regimes. Below this critical temperature, the sea ice is effectively impermeable, while for higher temperatures the brine phase becomes connected over macroscopic scales, allowing fluid transport through the ice. This transition has been observed to impact a wide range of phenomena such as surface flooding and snow–ice formation, enhancement of heat transfer due to fluid motion, mixing in the upper ocean, melt pool persistence, surface albedo (ratio of reflected to incident radiation) and other optical properties, growth and nutrient replenishment of algal and bacterial communities living in sea ice, and remote sensing of the sea ice pack from space. Recently, we have shown how continuum percolation theory can be used to understand the critical behavior of fluid transport in sea ice. Here we review this application of percolation theory to sea ice, and briefly discuss electromagnetic transport in sea ice, in particular how the geometry and connectivity of the brine microstructure determine its effective complex permittivity.
Title: Re: Basic questions about melting physics
Post by: nanning on August 21, 2019, 05:34:52 AM
Thanks bill, very interesting abstract.

Being a soft condensed matter guy, you might have some knowledge and understanding to add to the "Sea Ice Melting Affected by Microplastics?"-thread:
https://forum.arctic-sea-ice.net/index.php/topic,2732.msg203438.html#msg203438

(the hyperlink to the abstract/paper is not correct because of the attached "Get")  https://doi.org/10.1016/j.physb.2003.08.007
Title: Re: Basic questions about melting physics
Post by: bill kapra on August 21, 2019, 10:29:41 PM
Thanks for the fix and the reference, Nanning. Fascinating materials problem here!
Title: Re: Basic questions about melting physics
Post by: blumenkraft on August 28, 2019, 10:33:51 PM
Not entirely on topic, but the ice is melting there. (maybe)

Hear physics! Scary sounds from a frozen lake 🔊

Link >> https://www.reddit.com/r/Damnthatsinteresting/comments/cwmpk9/scary_sounds_from_a_frozen_lake/
Title: Re: Basic questions about melting physics
Post by: nanning on August 29, 2019, 05:27:23 AM
Maybe I'm not hearing the special sounds?  :-\

Those sounds are very familiar to me. I thought this is what a clear frozen toplayer does over a larger expanse.

I also remember cracks overtaking you when iceskating on a thin layer, also with great sounds. 8)
They say "cracking ice is trustworthy ice to skate on. If it doesn't make cracking sounds, be very careful".

That guy throwing the icesheet whilst rotating has had some practice I think. I wonder how many sets of dry clothes he used up for that shot, or perhaps the ice is much thicker than the icesheet he's throwing. Icesheets are supposed to be pretty heavy  ;D
Title: Re: Basic questions about melting physics
Post by: binntho on August 29, 2019, 05:42:53 AM
Not entirely on topic, but the ice is melting there. (maybe)

Hear physics! Scary sounds from a frozen lake 🔊

Link >> https://www.reddit.com/r/Damnthatsinteresting/comments/cwmpk9/scary_sounds_from_a_frozen_lake/

I've seen another one (if I remember correctly) where he used a single stone. The lake was very different, in a forested narrow valley.

But anyway, the sound that's so "scary" is the echo of the impact (and subsequent sliding) of the ice. This echo seems to be reverberating from the ice, a bit like the soundbox of a guitar or a violin, and then slowly fading away.

Wonder if there is a free space under the ice, creating the "soundbox" - i've seen such things (i.e. free space under the ice) happen on a lakesize scale, but with much thinner ice.
Title: Re: Basic questions about melting physics
Post by: Feeltheburn on August 30, 2019, 07:51:26 AM
This very interesting discussion regarding the heat losses and gains when ice melts and refreezes got me to thinking about a different heat flow issue involving water: Liquid water and water vapor.

I can't seem to find much in the climate science literature about it, but it is in physics books and an old popular science archive from 1891. Yes, that long ago!

When water evaporates from a body of water, the remaining thermal energy in the water is reduced by the amount of heat required to cause the phase change, or the latent heat of vaporization, which is enormous (540 calories per gram of water). It takes 100 calories to heat water from 0 degrees C to 100 degrees C, but 5-1/2 times more heat to just change liquid water to water vapor at constant temperature. This explains why evaporative coolers are very efficient at lowering air temperature in hot, dry climates.

When water evaporates from the ocean, heat energy (540 cal/gram) is transferred from the water to the water vapor, which then rises up into the upper atmosphere, where it meets extremely cold dry air, forms clouds, and then precipitates as rain or snow. When water vapor turns into water or ice, an enormous amount of heat energy is released into the surrounding upper atmosphere equal to the latent heats of vaporization and fusion.

Thus, there is a constant cooling cycle in which heat energy in the ocean is continuously being transferred to the upper atmosphere, where extremely cool rarified air absorbs this energy, causing water to precipitate and return to the earth as cold water or ice. The energy emitted from the precipitating water into the rarified air is then emitted back to outer space. I wonder if anyone has ever done the mathematical calculations to determine the absolute quantity of heat energy that is released from the oceans and sent on a one way ticket to the upper atmosphere where it is mostly sent back into space by the process of evaporation and precipitation cycles.

I read people saying there is unaccounted for heat hiding somewhere in the ocean, just waiting to strike the climate with a vengeance. But what if this energy isn't missing or hiding at all but slipping out the back door right before our very eyes by rising water vapor that is a conduit that pumps heat energy from the ocean back into space through continuous cycles of surface evaporation (picking up heat), rising 20,000 to 40,000 miles above the earth, and then releasing this energy into the freezing upper atmosphere when water precipitates and falls back to the earth. The heat cannot come back to earth because the precipitated water by definition gave up all its heat of vaporization and fusion to the upper atmosphere.

In short, rising water vapor is a one way conduit that removes heat from the ocean and all bodies of water and sends it up to the upper atmosphere, where it is released from the water, which falls back to earth depleted of heat, forming a heat gradient in the upper atmosphere. Because of entropy, hotter air always moves in the direction of colder air, which is air that is further from earth and closer to space. That means the heat that is released by precipitation is mostly lost to outer space. There is no mechanism to return it to earth.

Thus, the ocean is one giant heat pump that sends heat back to space through a process that is remarkably similar to how air conditioners work through a working fluid that evaporates to cool locally in one place and condenses to heat locally at another place. The cooling through evaporation is at the earth's surface, and the heating through condensation to release heat is at 20,000 to 40,000 feet where the heat is essentially given up by the earth for good.

I welcome all opinions and counterpoints.
Title: Re: Basic questions about melting physics
Post by: oren on August 30, 2019, 08:39:37 AM
Quote
I read people saying there is unaccounted for heat hiding somewhere in the ocean, just waiting to strike the climate with a vengeance. But what if this energy isn't missing or hiding at all but slipping out the back door right before our very eyes by rising water vapor that is a conduit that pumps heat energy from the ocean back into space 
I doubt you are describing it correctly, and I doubt "most energy is immediately lost to outer space", but regardless this mechanism has been in place forever, while ocean heat content growth is measurable and very real, so what is there to doubt?
Title: Re: Basic questions about melting physics
Post by: binntho on August 30, 2019, 08:56:19 AM
Quote
I read people saying there is unaccounted for heat hiding somewhere in the ocean, just waiting to strike the climate with a vengeance. But what if this energy isn't missing or hiding at all but slipping out the back door right before our very eyes by rising water vapor that is a conduit that pumps heat energy from the ocean back into space
I doubt you are describing it correctly, and I doubt "most energy is immediately lost to outer space", but regardless this mechanism has been in place forever, while ocean heat content growth is measurable and very real, so what is there to doubt?

I think in general FTB's essay has it right, but the particulars that oren points out are what needs closer scrutiny.

For one, the heat content of the oceans is something that can be (and is) measured directly, and it is rapidly increasing (causing most of the current sea level rise - the oceans are acting as their own old-fashioned thermometer).

As oren points out, the evaporative cycle is nothing new but it's there and it is probably conducting more heat the hotter the oceans get.

As for condensation, not all the water vapor condenses in the upper atmosphere - much of it condenses back to the surface (e.g. during nighttime) or close to the surface as fog. Not to forget the Foehn effect where heat released by condensation is brought down from the mountains into the lowlands, significantly raising near-surface temperatures.

And the heat released by cloud condensation is going to be radiative heat to a large degree, and given both greenhouse gases and the fact that this is happening inside a cloud, I don't think it's possible to claim that most of it gets lost to space. Much of it certainly, but how much? Does anybody know?

But in the end this is all just part of the heat balance, the flow of energy in the atmosphere (including the oceans), all very well measured and accounted for in total although the details may be a bit trickier.
Title: Re: Basic questions about melting physics
Post by: P-maker on August 30, 2019, 11:35:27 AM
Felltheburn,

To some extent, you are thinking along the right lines. Alternatively, you are messing up some of the basic physics.

As long as we are in the Tropics, everything is honkydory. Most physical processes take place well above 0C (or 273K). It is when you start using calories and F, your problems begin.

When in the Sub-tropics, some of the precipitation comes down as hail. In recent years, we have seen an increasing hail diameter and more devastating hailstorms spreading north. This may be a sign of the kind of physics you focus on. More evaporative cooling in combination with more humid air should eventually lead to bigger hail, if condensation nuclei are present.

Moving to Mid-latitudes, we begin to have the change-over from freezing rain to warm rain. Apparently, you have forgot to include the temperature of the falling rain. All heat evaporated is not simply sent out to outer space. Some of it will return to Earth as a mild, warm rain, where you would even enjoy getting your underpants wet from time to time.

Now, finally to the physical processes in the Arctic. Your idea that all evaporative cooling will eventually leave the Arctic cold and the World in thermal balance (had it not been for the wicked ocean heat storage), is simply wrong. The moisture advected from southerly latitudes (as well as the minor part of the moisture evaporated from open Arctic waters), will eventually have to come down again as either rain (above 0C), or as snow. In the latter case, we may see the opposite of "sublimation" - that is water vapour going directly into the frozen phase - which of course releases a lot more energy, than just converting water vapour directly into rain.

In the presence of cloud condensation nuclei, we will see hailstorms spreading north, and we will see rain and showers entering the Arctic during winter. What we have not seen yet, is the physical reaction from/to a clean - basically CCN-free - Arctic atmosphere. My guess would be that initially, we will see ice pellets, but eventually we will see drizzle as the Arctic temperatures during winter goes above 0C.

Sitting in Svalbard through the dark "drizzle season" is no great joy I would presume. Maybe it will be a great time to reflect on the basic physics of our time.

Cheers P





Title: Re: Basic questions about melting physics
Post by: Klondike Kat on August 30, 2019, 01:36:52 PM
Feeltheburn is not wrong in his understanding of the physics.  It may be a simplistic way of stating the processes.  In general, heat flows from a hot body to a colder body.  During evaporation, water vapor carries heat energy into the atmosphere, where it can dissipated to the surrounding air molecules.  This is many diverge in their analysis.  Feeltheburn stated that it is "mostly sent back to space."  P-maker states that, "some of it will return to earth."  The major question is how much?  Many modeler claim that a significant portion of the energy will simply return to the surface via the radiative effect due to the higher concentration of greenhouse gases.  This seems to be an overestimate as it involves heat flowing from a cooler to a warmer body.  Feeltheburn is probably close to the correct answer, and explains why so many have overestimated the warming effect of increasing atmospheric concentrations of greenhouse gases.  It would also help explain why the warmer waters entering the Arctic have not resulted in lower sea ice minima.
Title: Re: Basic questions about melting physics
Post by: binntho on August 30, 2019, 01:39:53 PM
Feeltheburn is probably close to the correct answer, and explains why so many have overestimated the warming effect of increasing atmospheric concentrations of greenhouse gases.  It would also help explain why the warmer waters entering the Arctic have not resulted in lower sea ice minima.

This got me confused. Who have been overestimting the warming effect of increased greenhous gases?

And am I missing something or haven't the lower sea ice minima been coming in at a regular rate as the oceans get warmer?

In the last few decades sea ice has declined drastically - so what is there to explain? Feeltheburn is, I feel, barking up the wrong tree altogether.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on August 30, 2019, 01:56:29 PM
Feeltheburn is probably close to the correct answer, and explains why so many have overestimated the warming effect of increasing atmospheric concentrations of greenhouse gases.  It would also help explain why the warmer waters entering the Arctic have not resulted in lower sea ice minima.

This got me confused. Who have been overestimting the warming effect of increased greenhous gases?

And am I missing something or haven't the lower sea ice minima been coming in at a regular rate as the oceans get warmer?

In the last few decades sea ice has declined drastically - so what is there to explain? Feeltheburn is, I feel, barking up the wrong tree altogether.

Based on the NSIDC data, sea ice minima were occurring roughly every three years until 2007.  Since then, there has been only one - in 2012.  Nine of the past eleven years have seen a higher minimum, and this year is likely to make ten.  The other year, 2016, barely edged out 2007 for a lower minimum.  All this has occurred while the oceans have been getting warmer.  So no, lower sea ice minima have NOT been coming at a regular rate as the oceans get warmer.
Title: Re: Basic questions about melting physics
Post by: binntho on August 30, 2019, 02:27:44 PM
Feeltheburn is probably close to the correct answer, and explains why so many have overestimated the warming effect of increasing atmospheric concentrations of greenhouse gases.  It would also help explain why the warmer waters entering the Arctic have not resulted in lower sea ice minima.

This got me confused. Who have been overestimting the warming effect of increased greenhous gases?

And am I missing something or haven't the lower sea ice minima been coming in at a regular rate as the oceans get warmer?

In the last few decades sea ice has declined drastically - so what is there to explain? Feeltheburn is, I feel, barking up the wrong tree altogether.

Based on the NSIDC data, sea ice minima were occurring roughly every three years until 2007.  Since then, there has been only one - in 2012.  Nine of the past eleven years have seen a higher minimum, and this year is likely to make ten.  The other year, 2016, barely edged out 2007 for a lower minimum.  All this has occurred while the oceans have been getting warmer.  So no, lower sea ice minima have NOT been coming at a regular rate as the oceans get warmer.

I think you are confusing random variability with trend. On a decadal trend, it is very obvious that sea ice has declined as ocean temps have gone up. Looking for that to happen every year is perhaps a bit simplistic.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on August 30, 2019, 02:34:22 PM
Feeltheburn is probably close to the correct answer, and explains why so many have overestimated the warming effect of increasing atmospheric concentrations of greenhouse gases.  It would also help explain why the warmer waters entering the Arctic have not resulted in lower sea ice minima.

This got me confused. Who have been overestimting the warming effect of increased greenhous gases?

And am I missing something or haven't the lower sea ice minima been coming in at a regular rate as the oceans get warmer?

In the last few decades sea ice has declined drastically - so what is there to explain? Feeltheburn is, I feel, barking up the wrong tree altogether.

Based on the NSIDC data, sea ice minima were occurring roughly every three years until 2007.  Since then, there has been only one - in 2012.  Nine of the past eleven years have seen a higher minimum, and this year is likely to make ten.  The other year, 2016, barely edged out 2007 for a lower minimum.  All this has occurred while the oceans have been getting warmer.  So no, lower sea ice minima have NOT been coming at a regular rate as the oceans get warmer.

I think you are confusing random variability with trend. On a decadal trend, it is very obvious that sea ice has declined as ocean temps have gone up. Looking for that to happen every year is perhaps a bit simplistic.

The decadal trend from the mid 90s to the mid 00s was definitively and largely downward.  The decadal trend since has been flat - a very slight increase starting at 2007, a similar decrease starting at 06 or 08.  I am not looking for it to happen every year - just more than once a decade.
Title: Re: Basic questions about melting physics
Post by: binntho on August 30, 2019, 02:54:39 PM
The decadal trend from the mid 90s to the mid 00s was definitively and largely downward.  The decadal trend since has been flat - a very slight increase starting at 2007, a similar decrease starting at 06 or 08.  I am not looking for it to happen every year - just more than once a decade.

I think you'll find that there is nowhere near enough datapoints to make statistically valid claims about changes in trends from one decade to another. In other words, it is not valid scientifically to say that there are differences in trend between one decade and another.

Besides just looking at a graph of minimums since the start of the satellite era shows a growing downwards trend, to match a growing warmin oceans trend.

But it's interesting that you think that Feeltheburn's hypothesis of having found a major missing piece in the whole field of meteorology can explain why your once-a-decade minimums aren't coming in (besides, I thought 2012 was this decade's minimum?)
Title: Re: Basic questions about melting physics
Post by: MyACIsDying on August 30, 2019, 04:57:01 PM
The AMOC has been weakening this decade to it's lowest strength, when the AMOC was a reason for arctic melt to increase, one would assume this weakening to minimum would mean increase in arctic ice extent? Clearly not.. so I wholly disagree on the flat lining trend of arctic ice melt. The 'Slow Transition' thread also explains reasons why extent is proportionally dropping less than volume is.

Klondike Kat I appreciate having your down to earth attitude on this forum but to say people are overestimating the effect GHG's?? I thought the science world was in general agreement that GHGs raising our radiation emittance roof is by far the largest reason for the change in thermodynamic equilibrium we know is happening by increases in heat content (.4Wms-2 imbalance to ~1200 Wms-2 incoming solar radiation may seem little but it accounts for all of the ~10^21 J /year OHC increase)

gerontocrat pointed out recently this is 130 times the energy used for our yearly losses to put that in perspective. Sure we can have localized feedback mechanisms that bring areas to cold extremes but I doubt any of these would be able overcome the global increase in temps in a permanent matter.

This is all assuming we keep the trend of GHG increase as it is.. I'm very curious what would happen if we lower the roof by taking CO2 out of the atmosphere? A cooldown faster than the warmup has taken I expect. Anyone know of models that ran such scenarios?
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on August 30, 2019, 05:45:55 PM
The AMOC has been weakening this decade to it's lowest strength, when the AMOC was a reason for arctic melt to increase, one would assume this weakening to minimum would mean increase in arctic ice extent? Clearly not.. so I wholly disagree on the flat lining trend of arctic ice melt. The 'Slow Transition' thread also explains reasons why extent is proportionally dropping less than volume is.

Klondike Kat I appreciate having your down to earth attitude on this forum but to say people are overestimating the effect GHG's?? I thought the science world was in general agreement that GHGs raising our radiation emittance roof is by far the largest reason for the change in thermodynamic equilibrium we know is happening by increases in heat content (.4Wms-2 imbalance to ~1200 Wms-2 incoming solar radiation may seem little but it accounts for all of the ~10^21 J /year OHC increase)

gerontocrat pointed out recently this is 130 times the energy used for our yearly losses to put that in perspective. Sure we can have localized feedback mechanisms that bring areas to cold extremes but I doubt any of these would be able overcome the global increase in temps in a permanent matter.

This is all assuming we keep the trend of GHG increase as it is.. I'm very curious what would happen if we lower the roof by taking CO2 out of the atmosphere? A cooldown faster than the warmup has taken I expect. Anyone know of models that ran such scenarios?

Thank you for your kind response.  The "people" to which I was referring are the posters here who claim that the current scientific thinking is too conservative and that the current warming is being masked by factor X, and once this is overcome, warming will skyrocket, causing all sorts of global catastrophes.  What if factor X for Arctic sea ice is just as FeeltheBurn has postulated, and will never be overcome?
Title: Re: Basic questions about melting physics
Post by: gerontocrat on August 30, 2019, 06:09:15 PM
I am not even going to try to get into the physics of the melting of ice. What I am looking at is what are the best measures of trends in sea ice loss (or gain)

When I was looking at trends in sea ice, like most people I used to look mostly at the sea ice annual minimum, and a little bit at the maximum. But as I started to make graphs of the Arctic in total, and then sea by sea, it became apparent that minimal reductions or even increases in the minimum could conceal significant reductions in sea ice.

I now have data that looks at ice-free days, open water percentages at various times of the year, and finally 365 trailing averages for extent, area and volume, the latter which  I attach. These show that although the 2012 JAXA extent minimum was 0.84 million km2 below any minimum since, the 2016 year produced a lower 365 day average. This was because sea ice was low for much longer than the crash in 2012.

2019 may now be looking like a bit of an end-of-season anti-climax, but nevertheless if refreeze is slow, the 365 day trailing average could well be a new record low by Spring 2020.

After the minimum, and after the end of the calendar year I hope to be able to show a similar story when looking at ice-free days and increases in open water.

So what am I saying - simply that minima may not be falling - but sea ice is declining.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on August 30, 2019, 06:35:14 PM
Geronocrat,
I agree that the ice has been generally in decline for the past four decades.  This occurred slowly at first, as the maximum sea ice started to fall.  The minimum was declining only slightly until the late 90s, when it plummeted.  This led to ab overall ice declined at a much faster rate until recently, when it has slowed considerably.  This occurred during the time that many pundits predicted an accelerated loss in Arctic sea ice to near ice-free conditions this decade.    All I am saying is that that his explanation is plausible explanation for the change.
Title: Re: Basic questions about melting physics
Post by: gerontocrat on August 30, 2019, 06:58:54 PM
Geronocrat,
I agree that the ice has been generally in decline for the past four decades.  This occurred slowly at first, as the maximum sea ice started to fall.  The minimum was declining only slightly until the late 90s, when it plummeted.  This led to ab overall ice declined at a much faster rate until recently, when it has slowed considerably.  This occurred during the time that many pundits predicted an accelerated loss in Arctic sea ice to near ice-free conditions this decade.    All I am saying is that that his explanation is plausible explanation for the change.
I just think that the minima to some extent disguise the loss of sea ice over time, and that the graphs I posted support that to some extent. I make no firm predictions about when a BOE etc etc will happen, but
- CO2 ppm will increase significantly for a good few years more on the most optimistic assumptions,
- the atmosphere will heat up for many more years,
- the Arctic will heat up faster than the average.

Ice and heat don't make long-lasting partners. The cryosphere in the Arctic will diminish, and so my very unfirm prediction is for summer sea ice to be very very much less by 2030, for which I cannot offer any evidence other than the above.
Title: Re: Basic questions about melting physics
Post by: sailor on August 30, 2019, 11:41:51 PM
Geronocrat,
I agree that the ice has been generally in decline for the past four decades.  This occurred slowly at first, as the maximum sea ice started to fall.  The minimum was declining only slightly until the late 90s, when it plummeted.  This led to ab overall ice declined at a much faster rate until recently, when it has slowed considerably.  This occurred during the time that many pundits predicted an accelerated loss in Arctic sea ice to near ice-free conditions this decade.    All I am saying is that that his explanation is plausible explanation for the change.
I just think that the minima to some extent disguise the loss of sea ice over time, and that the graphs I posted support that to some extent. I make no firm predictions about when a BOE etc etc will happen, but
- CO2 ppm will increase significantly for a good few years more on the most optimistic assumptions,
- the atmosphere will heat up for many more years,
- the Arctic will heat up faster than the average.

Ice and heat don't make long-lasting partners. The cryosphere in the Arctic will diminish, and so my very unfirm prediction is for summer sea ice to be very very much less by 2030, for which I cannot offer any evidence other than the above.
Completely true. A good example is 2016 Winter. It’s kinda predictable what will come, but how, it will amuse us or terrify us
Title: Re: Basic questions about melting physics
Post by: binntho on August 31, 2019, 06:38:57 AM
When I was looking at trends in sea ice, like most people I used to look mostly at the sea ice annual minimum, and a little bit at the maximum. But as I started to make graphs of the Arctic in total, and then sea by sea, it became apparent that minimal reductions or even increases in the minimum could conceal significant reductions in sea ice.

I now have data that looks at ice-free days, open water percentages at various times of the year, and finally 365 trailing averages for extent, area and volume, the latter which  I attach. These show that although the 2012 JAXA extent minimum was 0.84 million km2 below any minimum since, the 2016 year produced a lower 365 day average. This was because sea ice was low for much longer than the crash in 2012.
...
So what am I saying - simply that minima may not be falling - but sea ice is declining.

I agree with you Gero, and I think that the three graphs you posted there are by far the best when it comes to looking at the real underlying trends.

But I am not so sure about the red polynomial lines on two of them - just from eyeballing I would have thought that a simple curve (i.e. second grade polynomial) with an increasing downwards curve would be the best match?
Title: Re: Basic questions about melting physics
Post by: binntho on August 31, 2019, 07:05:45 AM
Geronocrat,
I agree that the ice has been generally in decline for the past four decades.  This occurred slowly at first, as the maximum sea ice started to fall.  The minimum was declining only slightly until the late 90s, when it plummeted.  This led to ab overall ice declined at a much faster rate until recently, when it has slowed considerably.  This occurred during the time that many pundits predicted an accelerated loss in Arctic sea ice to near ice-free conditions this decade.    All I am saying is that that his explanation is plausible explanation for the change.

I'm a bit surprised at your repeated claims here KK.

"The minimum was declining only slightly until the late 90s when it plummeted" is not correct, nor has it slowed "considerably" recently.

The attached is NSIDC daily minimum figures, up to and including 2019 at 4.3 4.6, which is appr. today's number. This graph does not allow any such statements, and there are no statistical models that will support anything other than a straight line.

The curve does jump up and down, but that cannot be shown to be other than random variability. So any and all guesses as to explanations for probably non-existent changes in trend are really a bit silly.

EDIT: The figure I used for 2019 was the Jaxa figure, NSIDC is apparently 0.3 MKm2 higher. Graph is corrected.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on August 31, 2019, 03:24:38 PM
Geronocrat,
I agree that the ice has been generally in decline for the past four decades.  This occurred slowly at first, as the maximum sea ice started to fall.  The minimum was declining only slightly until the late 90s, when it plummeted.  This led to ab overall ice declined at a much faster rate until recently, when it has slowed considerably.  This occurred during the time that many pundits predicted an accelerated loss in Arctic sea ice to near ice-free conditions this decade.    All I am saying is that that his explanation is plausible explanation for the change.

I'm a bit surprised at your repeated claims here KK.

"The minimum was declining only slightly until the late 90s when it plummeted" is not correct, nor has it slowed "considerably" recently.

The attached is NSIDC daily minimum figures, up to and including 2019 at 4.3 4.6, which is appr. today's number. This graph does not allow any such statements, and there are no statistical models that will support anything other than a straight line.

The curve does jump up and down, but that cannot be shown to be other than random variability. So any and all guesses as to explanations for probably non-existent changes in trend are really a bit silly.

EDIT: The figure I used for 2019 was the Jaxa figure, NSIDC is apparently 0.3 MKm2 higher. Graph is corrected.

Your curve supports my claim as stated.  The minimum was decreasing slowly, until it took a bigger dive in the 90s.  That lasted about 15 years, depending on which curve fitting one chooses.  Since then, the minimum has flatlined.  Calling those significant chances random variability is quite the stretch.  Even the curve Gerontocrat presenter shows the changes.  My claim should come as no surprise to those who have been following the ice for the past years (decades),
Title: Re: Basic questions about melting physics
Post by: Archimid on August 31, 2019, 04:02:37 PM
So basically your argument is that "there has been no warming since 1998" adapted poorly to "Sea Ice stopped melting in 2012".

For that you use a pseudo explanation, seconded by the climate change deniers and validated by  Bintho's polite argument.

Quote
The "people" to which I was referring are the posters here who claim that the current scientific thinking is too conservative and that the current warming is being masked by factor X, and once this is overcome, warming will skyrocket, causing all sorts of global catastrophes. 

This has already happened and will keep happening and getting worse. You can't see it because fear blinds you, but you will feel it soon regardless if you understand what is happening or not.
Title: Re: Basic questions about melting physics
Post by: gerontocrat on August 31, 2019, 04:51:47 PM
I agree with you Gero, and I think that the three graphs you posted there are by far the best when it comes to looking at the real underlying trends.

But I am not so sure about the red polynomial lines on two of them - just from eyeballing I would have thought that a simple curve (i.e. second grade polynomial) with an increasing downwards curve would be the best match?
So did I, so I told it to do it, and it produced a lunatic U curve pointing UP, and a lousy R2. So I looked for a reasonable R2 and a result not showing ridiculous future increases or decreases. The ones on the graphs are the best I could do. But I don't like these red trend lines either. These periodic large rises and falls are just as well represented by an obviously untrue linear projection.

My own pure guess is that we are looking at 2 steps down, 1 step up as the years go by until the ice gets so thin and fragmented that in a year favourable for melting - poof ! (as posters have shown here and there on the melting season thread). But that is pure speculation (that now belongs to me since I stole it from others).
Title: Re: Basic questions about melting physics
Post by: binntho on August 31, 2019, 05:14:28 PM
Calling those significant chances random variability is quite the stretch. 
<snip> 
My claim should come as no surprise to those who have been following the ice for the past years (decades),

Well yes, I've seen the same claim made over and over again over the last few years and every time I try to point out that it simply can't be done that way. The points are way too few, the variation far too big, to be able to claim with any statistical support whatsoever that the trend has changed during the satellite era.

This is not to say that there has not been a change in trend, but statistical analysis will not support this. It is not good enough to squint at the chart and say, "it seems to me that the trend is bigger here than there ..." It can be good fun, and it can be very interesting to try to figure out why the trend has changed (that is, of course, if it has changed and it's not just natural variability).

But going from "it looks to me like the trend has been changing" to taking Feeltheburns attempts at rewriting meteorology to support this feeling is a huge stretch, literally an immaginative jump. And as such, pretty silly.

And look at the graph again, and compare it to this famous graph, copied from tamino's webpage. It's obvious, isn't it, that there is a change in trend between the 90s, the noughts and the teens? The noughts are obviously stalling.

(https://tamino.files.wordpress.com/2019/01/nasa1y.jpg)

But no, Tamino has shown again and again that statistically there was no pause in global warming in the noughts - it just looks that way because of the randomness of natural variability.

And the same goes for the changes in SIE minimums over the last four decades - randomnes and natural variability are just as good an explanation as any hypothetical state changes leading to changes in melting rate.

https://tamino.wordpress.com/
Title: Re: Basic questions about melting physics
Post by: binntho on August 31, 2019, 05:18:32 PM
I agree with you Gero, and I think that the three graphs you posted there are by far the best when it comes to looking at the real underlying trends.

But I am not so sure about the red polynomial lines on two of them - just from eyeballing I would have thought that a simple curve (i.e. second grade polynomial) with an increasing downwards curve would be the best match?
So did I, so I told it to do it, and it produced a lunatic U curve pointing UP, and a lousy R2.
I tried the same and got the same result. Doh!
Title: Re: Basic questions about melting physics
Post by: binntho on August 31, 2019, 05:25:20 PM
For that you use a pseudo explanation, seconded by the climate change deniers and validated by  Bintho's polite argument.

*sigh* I keep forgetting that there are Americans reading this blog. What I did was what we in Europe call "a polite rejection", similar to the Chinese custom of helping your opponent maintain face.

As Mrs. Brown would say, "that's nice".

Besides, Feeltheburn's small essay was well written and started off fine, but it ended in a very strange conclusion, so dealing politely with it seemed to me to be the best thing. But did I validate his conclusion? I hope not.
Title: Re: Basic questions about melting physics
Post by: Archimid on August 31, 2019, 05:37:04 PM
Your second reply completely invalidates his conclusion with a very appropriate language and tone. Thank you for that great reply and thank you for proving me wrong.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on August 31, 2019, 05:44:15 PM
Calling those significant chances random variability is quite the stretch. 
<snip> 
My claim should come as no surprise to those who have been following the ice for the past years (decades),

Well yes, I've seen the same claim made over and over again over the last few years and every time I try to point out that it simply can't be done that way. The points are way too few, the variation far too big, to be able to claim with any statistical support whatsoever that the trend has changed during the satellite era.

This is not to say that there has not been a change in trend, but statistical analysis will not support this. It is not good enough to squint at the chart and say, "it seems to me that the trend is bigger here than there ..." It can be good fun, and it can be very interesting to try to figure out why the trend has changed (that is, of course, if it has changed and it's not just natural variability).

But going from "it looks to me like the trend has been changing" to taking Feeltheburns attempts at rewriting meteorology to support this feeling is a huge stretch, literally an immaginative jump. And as such, pretty silly.

And look at the graph again, and compare it to this famous graph, copied from tamino's webpage. It's obvious, isn't it, that there is a change in trend between the 90s, the noughts and the teens? The noughts are obviously stalling.

(https://tamino.files.wordpress.com/2019/01/nasa1y.jpg)

But no, Tamino has shown again and again that statistically there was no pause in global warming in the noughts - it just looks that way because of the randomness of natural variability.

And the same goes for the changes in SIE minimums over the last four decades - randomnes and natural variability are just as good an explanation as any hypothetical state changes leading to changes in melting rate.

https://tamino.wordpress.com/

That graph us an excellent example.  Would you use a simple linear curve for that data?  Of course not, it is polymeric in nature.  The R2 would tell you that.  Just like Gerontocrat has been trying to tell you with his graphs.  Using a simple linear regression does not tell the whole story.  Does the line in his graphs tell the whole story?  Probably not.  However, it is a better analysis than a straight line.  Selective curve fitting to match ones own beliefs, is one of the reasons that several people have erroneously predicted that the Arctic would be ice-free by now.  The Arctic sea ice minimum has not decreased recently.  If you refuse to see that from the data, there is nothing more that I can say.
Title: Re: Basic questions about melting physics
Post by: oren on August 31, 2019, 05:50:15 PM
Geronocrat,
I agree that the ice has been generally in decline for the past four decades.  This occurred slowly at first, as the maximum sea ice started to fall.  The minimum was declining only slightly until the late 90s, when it plummeted.  This led to ab overall ice declined at a much faster rate until recently, when it has slowed considerably.  This occurred during the time that many pundits predicted an accelerated loss in Arctic sea ice to near ice-free conditions this decade.    All I am saying is that that his explanation is plausible explanation for the change.
At what point did FTB's description include anything about a change in the described mechanism? Evaporation from the ocean is nothing new.  Why would it suddenly halt sea ice loss? Regardless of whether there has been or hasn't been a hiatus in ice loss, his description doesn't explain anything at all.
KK, do you believe global ocean heat content has been rising, or is it stable maybe? If it is rising, FTB's description is irrelevant.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on August 31, 2019, 06:15:42 PM
Geronocrat,
I agree that the ice has been generally in decline for the past four decades.  This occurred slowly at first, as the maximum sea ice started to fall.  The minimum was declining only slightly until the late 90s, when it plummeted.  This led to ab overall ice declined at a much faster rate until recently, when it has slowed considerably.  This occurred during the time that many pundits predicted an accelerated loss in Arctic sea ice to near ice-free conditions this decade.    All I am saying is that that his explanation is plausible explanation for the change.
At what point did FTB's description include anything about a change in the described mechanism? Evaporation from the ocean is nothing new.  Why would it suddenly halt sea ice loss? Regardless of whether there has been or hasn't been a hiatus in ice loss, his description doesn't explain anything at all.
KK, do you believe global ocean heat content has been rising, or is it stable maybe? If it is rising, FTB's description is irrelevant.

Globally, yes.  That may not be true in the Arctic.  The lessening of Arctic sea will cause more evaporative losses.  Heat is lost more readily at the poles than elsewhere.
Title: Re: Basic questions about melting physics
Post by: oren on August 31, 2019, 07:01:44 PM
I wonder then how it is that seas which lose their sea ice cover earlier (such as the Chukchi) have warmer SSTs than in the past. You would think that this newfound evaporation scheme would cool them somehow.
Note: I don't have access to a ready-made chart for this claim, but am pretty sure it is true based on following the melting seasons.
Title: Re: Basic questions about melting physics
Post by: Glen Koehler on August 31, 2019, 08:06:09 PM
  The Arctic sea ice minimum has not decreased recently.  If you refuse to see that from the data, there is nothing more that I can say.

KK - depends on what you mean by "recently."  Given the internal variability of the system, a 7-year or 10-year window (i.e. since 2012, 2008) is too short to draw conclusions.  To protect against cherry picking and our innate human tendency for "pattern matching" where there is none, a longer interval of at least 20 years is required. 

     The 20-year downward trend in annual minimum Arctic sea ice volume appears to be much larger than year-to-year variation, and thus appears to be statistically significant.  Maybe somebody with more time and skill will run the stats on 1998-2018 annual min. volume data.  Moreover, 2019 is likely to end up with less the 4M km3, and thus land right on and thus reinforce the PIOMAS trend shown at
http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAprSepCurrent.png (http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAprSepCurrent.png)

    I think focusing so much on Extent leads us to false conclusions on both the high and low side.  2012 was bad for volume, but not nearly as extreme as it was for Extent.  To a substantial degree, Extent reflects temporary wind and current conditions, not the true status of the Arctic sea ice.  By focusing on Extent we can under-represent the cumulative progressive effects on overall condition of the ice. 

     The ice year this year has looked weaker more fractured than in past years.  A subjective measure to be sure, but not to be fully discounted either.  It will be interesting to see how the MYI numbers look after the 2019 melt season.  My guess is that they took another downward hit such that we are getting very close to only 1st and 2nd year ice that is more vulnerable than the tough old 5- and even 10-year old ice of the recent past.  The final phase of decline in ASI Extent is slowed by the much more rapid regrowth of 1st year ice.  But the flip side of that is that 1st year ice also melts out faster.   In retrospect, the functional loss of the Beaufort Sea ice nursery may be seen as a crucial event marking the beginning of the end of ASI in Aug-Sept.   I suspect with only 1st-year ice to get rid of at the start of future melt seasons, it won't last much beyond July 31.

     That's how it looks to me anyway.  No formal training in Arctic or ice, just a little experience analyzing numbers and interpreting science added to lurking in the ASIF.  Thanks to those who provide interesting info and speculation to ASIF.  Esp. thanks to Neven, Gero, JCG, uniquorn, Alphabet and others. Less gratitude for those who engage in extended ego-defensive debates.  To those folks I say, let others disagree with you and get over it.  Nobody else cares if somebody insults you.  Now you can disagree with me! 
Title: Re: Basic questions about melting physics
Post by: gerontocrat on August 31, 2019, 08:12:58 PM
I wonder then how it is that seas which lose their sea ice cover earlier (such as the Chukchi) have warmer SSTs than in the past. You would think that this newfound evaporation scheme would cool them somehow.
Note: I don't have access to a ready-made chart for this claim, but am pretty sure it is true based on following the melting seasons.
Google provides...
https://arctic.noaa.gov/Report-Card/Report-Card-2015/ArtMID/5037/ArticleID/220/Sea-Surface-Temperature

A bit out of date (only to 2015) but I am sure given recent data that the only way was up.

Quote
The Chukchi Sea and eastern Baffin Bay show the largest ocean surface warming trends; August SSTs are increasing at ~0.5°C/decade in these regions.
Title: Re: Basic questions about melting physics
Post by: gerontocrat on August 31, 2019, 08:57:32 PM
Oren - you sent me on the hunt for data....

A bit more... from NOAA Report Card 2018
https://www.arctic.noaa.gov/Report-Card/Report-Card-2018/ArtMID/7878/ArticleID/779/Sea-Surface-Temperature

Quote
Mean August SSTs from 1982-2018 show warming trends over much of the Arctic Ocean; statistically significant (at the 95% confidence interval) linear warming trends of up to +1° C decade-1 are observed (Figs. 1d and 2). These warming trends coincide with declining trends in summer sea-ice extent (including late-season freeze-up and early melt, e.g., Parkinson, 2014), increased solar absorption (e.g., Timmermans et al., 2018), and increased vertical ocean heat transport (e.g., Lind et al., 2018).
Title: Re: Basic questions about melting physics
Post by: oren on August 31, 2019, 10:38:03 PM
Thank you G.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on August 31, 2019, 10:49:32 PM
  The Arctic sea ice minimum has not decreased recently.  If you refuse to see that from the data, there is nothing more that I can say.

KK - depends on what you mean by "recently."  Given the internal variability of the system, a 7-year or 10-year window (i.e. since 2012, 2008) is too short to draw conclusions.  To protect against cherry picking and our innate human tendency for "pattern matching" where there is none, a longer interval of at least 20 years is required.

Glen, I fear you may be the one engaging in cherry picking.  By choosing a start date of 1998, you are ensuring the largest possible decreasing trend.  Contrarily, I choose the entire 40/year dataset.   The 7- or 10-year window only appears too short to you, because it does give the trend you want to see.  That is one of the main reasons I prefer analyses by well-established scientists over others.
Title: Re: Basic questions about melting physics
Post by: nanning on September 01, 2019, 04:08:48 AM
<snip>
Nobody else cares if somebody insults you.

Good post imo Glen but I disagree with this last bit because I do care.
If somebody uses nasty language, impolite insults, name calling etc. they don't get a like from me, even if I think the rest of the post is really good.
I don't think it has any influence but it is my way. In some cases I'll post a question about it.

OK back to topic, sorry.
Title: Re: Basic questions about melting physics
Post by: binntho on September 01, 2019, 08:42:16 AM
That graph us an excellent example.  Would you use a simple linear curve for that data?  Of course not, it is polymeric in nature.  The R2 would tell you that.
I doubt very much if it is "polymeric" in "nature" - whatever that means. Can a graph have a "nature"? And if you are so sure of the R2, why not try yourself?

Me, I am nowhere near good enough at statistics to make such claims, but I have been following Tamino's blog for some years, and he is a true master of the art.

His latest post is actually about this very thing, i.e. how has the rate of warming changed over the last 150 years or so. And funnily enough, he doesn't even mention the "polymeric nature" of the graph.

Here, on the other hand, is that graph with some statistically valid change points and linear trends connecting them. This is apparently statistically the best fit to the data. (https://tamino.wordpress.com/2019/08/20/global-warming-how-fast/)

(https://tamino.files.wordpress.com/2019/08/model2.jpg)

Quote

 Just like Gerontocrat has been trying to tell you with his graphs.  Using a simple linear regression does not tell the whole story.  Does the line in his graphs tell the whole story?  Probably not.  However, it is a better analysis than a straight line.


If Gerontocrat tried to tell me something, I'm sure that he would succeed. And I do not recall him trying to tell me that graphs have "polymeric" natures, or that his polymeric line is a "better analysis" than a straight line. So what does Gero himself have to say about his polymeric red lines?

But I don't like these red trend lines either. These periodic large rises and falls are just as well represented by an obviously untrue linear projection.

Which is perfectly reasonable. A linear trend is simply the only thing that matches the data we have in any statistically valid sense. And before somebody points this out, I am well aware that the R2 values for the polynomials are slightly better than for the linears, but that is still not valid since these graphs are running averages.

If you run linear and polynomial regressions on the raw data you get identical R2 values of c.a. 0.037 (because of the very large variance, the R2 is quite low), no visible trend changes in the polynomial within the period in question, and a downward trend of 73.000 km2 per annum for both.

Funnily enough, this graph plotting the NSIDC values shows a downward trend of 81.100 km2 per annum, while Gero's SIE 365 day running average linear regression shows a downward trend of 67.291 km2 per annum.

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=2709.0;attach=131600;image)
Missing from the graph is the formula y = -0.0811x + 168.03 and an R2 of 0.7803.


The problem arises when people try to extend the linear trend into a linear projection and get different answers from different graphs. So clearly, the linear trends cannot be used to project the zero point. That does not mean that other strangely looking swirly polynomials are going to do any better. To repeat: There are not enough data points in the minimum graph, and the variance is too big to justify anything other than a linear trend.

Quote
Selective curve fitting to match ones own beliefs, is one of the reasons that several people have erroneously predicted that the Arctic would be ice-free by now.  The Arctic sea ice minimum has not decreased recently.  If you refuse to see that from the data, there is nothing more that I can say.

We can agree that selective curve fitting is a no-go. But I can only agree with your statement that the minimum has not "decreased recently" if we always define "recently" as "since the last record minimum".

The problem with your statements, KK, is that you think you can see trend changes in the graph. I claim that the graph has too few data points and too much variance to justify such claims.  So the "not decreased recently" is a real thing for now, but has no actual meaning - it is not possible, based on the data, to make claims about a statistically valid change in trend.

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=2709.0;attach=131600;image)

That is not to say that there isn't a change in the underlying forces that interact in the high Arctic and give us minimums every year. Perhaps something has changed that makes new record minimums very unlikely, or perhaps that was always built into the system, that the graph would eventually flatline around this level.

And yes, just looking at the graph of SIE minimums can well make you think that this is what is happening. But there is no statistically valid basis to such claims, and probably won't be for another 10 years or so. If, in 2029, we are still hovering around the 4M mark, a change in trend will be statistically valid. Today it is not.

And when you seek weird explanations (such as Feeltheburn's erraneous understanding of meteorology) to explain your non-statistically-valid claims, then we are way into the land of silliness.
Title: Re: Basic questions about melting physics
Post by: blumenkraft on September 01, 2019, 10:52:17 AM
Kat, what you see as a stalling is most likely variance. Variance is expected in a highly complex/chaotic system. Given the context, it's extremely unlikely that it is indeed a stalling.

Title: Re: Basic questions about melting physics
Post by: Klondike Kat on September 02, 2019, 03:10:51 PM
Kat, what you see as a stalling is most likely variance. Variance is expected in a highly complex/chaotic system. Given the context, it's extremely unlikely that it is indeed a stalling.

If it were truly variance, it should be random.  Look at the graph and trend posted by binntho.  From 96 to 06, all the variance was above the trend.  Then, there were six straight years below the trend, some substantially.  There is no physical reason that the ice should follow a linear line.  Perhaps it is just variance, but it has shown variance in a flattening direction for over a decade now.  How long must it occur, before it becomes acceptable?
Title: Re: Basic questions about melting physics
Post by: binntho on September 02, 2019, 03:52:28 PM
Kat, what you see as a stalling is most likely variance. Variance is expected in a highly complex/chaotic system. Given the context, it's extremely unlikely that it is indeed a stalling.

If it were truly variance, it should be random.  Look at the graph and trend posted by binntho.  From 96 to 06, all the variance was above the trend.  Then, there were six straight years below the trend, some substantially. 


Even if it is possible for the human mind to see patterns doesn't mean that they aren't the product of random variance. Co-incidence and randomness could indeed well produce the pattern we all see in the graphs.

This whole discussion really revolves around the number of datapoints. With only 40 datapoints it's not possible to claim anythying statistically other than that a linear trend is a fairly good fit.

Quote

There is no physical reason that the ice should follow a linear line.  Perhaps it is just variance, but it has shown variance in a flattening direction for over a decade now.  How long must it occur, before it becomes acceptable?

There is a very good physical reason for the ice to follow what seems to be a linear trend over the 40 year period - global temperatures have been rising with a linear trend during the same time, and lower SIE is a direct consequence of higher temperatures.

As can be seen in my earlier graph, the closest we can say statistically about the temperature change over the 40 year period is that it has risen linearly. Therefore we should a priori expect sea ice extent to fall linearly.

On the other hand, we can all come up with lots of reasons for why the rate of diminishing SIE or rate of falling minimums etc. should not be linear, at least not always and under all circumstances. The drastic loss of MYI is certainly one of the most obvious ones, the shape of the Arctic ocean another.

But there are lots of other factors at play, such as the relentlessly rising ocean temperatures, the increasing storminess, and the essential randomness of weather coupled with the apparent sensitivity of the melting season to the "right" type of weather at the "right" time.

So at least from my point of view, declaring the linear trend to be dead and void is much too premature. I'll repeat what I said earlier - let's wait another 10 years, and then we'll (perhaps) be able to tell if there really was a change in trend 10 years ago.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on September 02, 2019, 04:44:34 PM
Kat, what you see as a stalling is most likely variance. Variance is expected in a highly complex/chaotic system. Given the context, it's extremely unlikely that it is indeed a stalling.

If it were truly variance, it should be random.  Look at the graph and trend posted by binntho.  From 96 to 06, all the variance was above the trend.  Then, there were six straight years below the trend, some substantially. 


Even if it is possible for the human mind to see patterns doesn't mean that they aren't the product of random variance. Co-incidence and randomness could indeed well produce the pattern we all see in the graphs.

This whole discussion really revolves around the number of datapoints. With only 40 datapoints it's not possible to claim anythying statistically other than that a linear trend is a fairly good fit.

Quote

There is no physical reason that the ice should follow a linear line.  Perhaps it is just variance, but it has shown variance in a flattening direction for over a decade now.  How long must it occur, before it becomes acceptable?

There is a very good physical reason for the ice to follow what seems to be a linear trend over the 40 year period - global temperatures have been rising with a linear trend during the same time, and lower SIE is a direct consequence of higher temperatures.

As can be seen in my earlier graph, the closest we can say statistically about the temperature change over the 40 year period is that it has risen linearly. Therefore we should a priori expect sea ice extent to fall linearly.

On the other hand, we can all come up with lots of reasons for why the rate of diminishing SIE or rate of falling minimums etc. should not be linear, at least not always and under all circumstances. The drastic loss of MYI is certainly one of the most obvious ones, the shape of the Arctic ocean another.

But there are lots of other factors at play, such as the relentlessly rising ocean temperatures, the increasing storminess, and the essential randomness of weather coupled with the apparent sensitivity of the melting season to the "right" type of weather at the "right" time.

So at least from my point of view, declaring the linear trend to be dead and void is much too premature. I'll repeat what I said earlier - let's wait another 10 years, and then we'll (perhaps) be able to tell if there really was a change in trend 10 years ago.

I will agree with much of what you says.  40 data points is not possible to claim anything statistically.  Although, we can say with much confidence that today is lower that 40 years ago.  Focusing on just the data from the annual minimum is not the best method of analyzing the sea ice, but it tends to get the most attention.   Yes, many factors are in play, such that correlating sea ice directly to global temperatures may not be the best practice.  I have no reason to believe that the sea ice will show a flat trend for another 10 years, but if it does, than I would expect most to accept the change in trend.  The sharp decline in sea ice has only shown a ~15-year trend, so they would be on par. 

One final point.  Sea ice analyses, no matter which metric, treats the entire ice as one.  In reality, it is made up of several small seas, bays, etc., and one large central ocean.  Much of the previous changes occurred largely in the peripheral seas, and less so in the central Arctic basin.  We may just be seeing a shift to the new regime.
Title: Re: Basic questions about melting physics
Post by: binntho on September 02, 2019, 05:01:23 PM
I will agree with much of what you says.  40 data points is not possible to claim anything statistically.  Although, we can say with much confidence that today is lower that 40 years ago. 

To be specific: 40 datapoints are not enough to decide whether there has been a change in trend. But it's plenty sufficient to show that there is a downward trend!

Quote

Focusing on just the data from the annual minimum is not the best method of analyzing the sea ice, but it tends to get the most attention.   


Absolutely, and the graphs that Gerontocrat has made from the 365 day averages are vastly to be preferred.

Quote
Yes, many factors are in play, such that correlating sea ice directly to global temperatures may not be the best practice.  I have no reason to believe that the sea ice will show a flat trend for another 10 years, but if it does, than I would expect most to accept the change in trend.  The sharp decline in sea ice has only shown a ~15-year trend, so they would be on par. 


If the trend flatlines for the next 10 years then I think that it's going to be pretty obvious, and statistically valid as well. And if there is an underlying dynamic that has cause a stall the last 10 years, why shouldn't it continue?

On the other hand, if the trend does not flatline then a hypothetical change in trend becomes unproven - but the underlying dynamics may still have been at work, flatlining for a period, but too hidden by the noisiness of the signal to be statistically detectable.

And your last comment, that the sharp decline in sea ice has shown a ~15 year trend, is again not something that cannot be stated with any statistical validity. There is no 10 or 15 or 20 year trends that can be read out of the minimum graphs, or the 365 day average graphs.

The only trend that can be read out of the graphs is that sea ice has been declining, and as far as the statistics go, basically linearly for the last 40 years.

Quote
One final point.  Sea ice analyses, no matter which metric, treats the entire ice as one.  In reality, it is made up of several small seas, bays, etc., and one large central ocean.  Much of the previous changes occurred largely in the peripheral seas, and less so in the central Arctic basin.  We may just be seeing a shift to the new regime.

Yes that's absolutely true, as I indicated earlier by mentioning the shape of the Arctic ocean. And a hypothetical "shift to a new regime" could well be an explanation for a hypothetical "stall". And if there is indeed such a shift then I would expect the stall to easily last the next 10 years.
Title: Re: Basic questions about melting physics
Post by: blumenkraft on September 02, 2019, 05:20:40 PM
If it were truly variance, it should be random.

OK, you don't understand what randomness is. That's a common problem with humans.

Quote
If you roll a fair, 6-sided die, there is an equal probability that the die will land on any given side.

Meaning, if you roll a dice, you have always the chance to roll a 6. So, if you roll 20 times a 6 in a row, it is ... well ... completely random! :)
Title: Re: Basic questions about melting physics
Post by: crandles on September 02, 2019, 05:36:11 PM
To be specific: 40 datapoints are not enough to decide whether there has been a change in trend. But it's plenty sufficient to show that there is a downward trend!

The number of datapoints needed does of course depend on how much the trend changes, the level of noise in the data, and perhaps other factors.

Also 40 datapoints is not all we have got. We have other months data which also show similar shapes. How much use that is may depend on autocorrelation, but I think there isn't much autocorrelation between maximum and minimum.

So anyone want to venture a calculation of when we should be able to say change of trend is statistically significant rather than just plucking 10 years out of the air? 10 years seems a bit long to me if the difference in trend rate is noticeably different. If new data points tend to be just above long term linear rate then it will take a long time, probably longer than 10 years. So the answer may need to be in terms of 'if x difference then y years but if z different then w years. So maybe a better question is at what statistical level of confidence are we at now? (Where not reasonably established until 95% confidence reached.)
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on September 02, 2019, 05:40:14 PM
If it were truly variance, it should be random.

OK, you don't understand what randomness is. That's a common problem with humans.

Quote
If you roll a fair, 6-sided die, there is an equal probability that the die will land on any given side.

Meaning, if you roll a dice, you have always the chance to roll a 6. So, if you roll 20 times a 6 in a row, it is ... well ... completely random! :)

Really?  I would question your die.  That odds of that occurring is less than 1 in a trillion.  You call that random, and have the audacity to question my understanding of randomness?!
Title: Re: Basic questions about melting physics
Post by: blumenkraft on September 02, 2019, 06:01:03 PM
That odds of that occurring is less than 1 in a trillion.

And? What has odds to do with how the dice will fall?

The dice can't remember it's recent states and it has no understanding of the concept of 'odds'. It just obeys physics.

I'm having a bitcoin mining background which is the ultimate lesson in understanding randomness. I got this, Kat, believe me.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on September 02, 2019, 06:07:22 PM
That odds of that occurring is less than 1 in a trillion.

And? What has odds to do with how the dice will fall?

The dice can't remember it's recent states and it has no understanding of the concept of 'odds'. It just obeys physics.

I'm having a bitcoin mining background which is the ultimate lesson in understanding randomness. I got this, Kat, believe me.

What does the odds have to do with how the dice fall?  Everything!  While each individual throw has the same odds, over time, they will even out, each number occurring nearly equally.  Straight-forward mathematics.  Should one number dominate against all odds, I would seriously question the integrity of the die.  This has nothing to do with physics, unless the die is loaded, causing the number 6 to occur repeatedly.
Title: Re: Basic questions about melting physics
Post by: blumenkraft on September 02, 2019, 06:15:44 PM
each individual throw has the same odds

Stop right there. This is really all there is to it.

It's not math. Math is a tool to calculate the odds. The math doesn't make the odds.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on September 02, 2019, 06:55:00 PM
each individual throw has the same odds

Stop right there. This is really all there is to it.

It's not math. Math is a tool to calculate the odds. The math doesn't make the odds.

If you truly understand the odds, then why are you having such a hard time grasping the improbability of 20 straight sixes?
Title: Re: Basic questions about melting physics
Post by: blumenkraft on September 02, 2019, 07:16:28 PM
If you truly understand the odds, then why are you having such a hard time grasping the improbability of 20 straight sixes?

I'm not talking about the odds, Kat. You do. I'm talking about randomness.

You can't know the odds concerning the arctic area/extent numbers. And here we go full circle. :)

You can though, given the context, make assumptions about the odds. And they tell me this is most likely variance.
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on September 02, 2019, 07:21:27 PM
If you truly understand the odds, then why are you having such a hard time grasping the improbability of 20 straight sixes?

I'm not talking about the odds, Kat. You do. I'm talking about randomness.

You can't know the odds concerning the arctic area/extent numbers. And here we go full circle. :)

You can though, given the context, make assumptions about the odds. And they tell me this is most likely variance.

So, depending on ones assumptions, determined ones assessment.  Hence, they is little agreement.
Title: Re: Basic questions about melting physics
Post by: blumenkraft on September 02, 2019, 07:27:09 PM
Hence, they is little agreement.

Totally agree to disagree. :)
Title: Re: Basic questions about melting physics
Post by: petm on September 02, 2019, 07:35:11 PM
Are you talking about rolling 1 six after having rolled five sixes already, or rolling 6 sixes after having rolled none? Completely different questions.

Also, wtf?  ??? ;D
Title: Re: Basic questions about melting physics
Post by: crandles on September 02, 2019, 07:39:28 PM
(https://tamino.files.wordpress.com/2016/07/ice_change.jpg)

Quote
To know whether or not those indicated changes are real or just the impression given by random noise, a good way is to apply changepoint analysis. That confirms that these changes are indeed real, and gives the following “continuous piecewise linear” model of the anomalies.

https://tamino.wordpress.com/2016/07/17/arctic-heat/

Seems like Tamino confirmed it was real/statistically significant back in 2016?

We are rather off topic lets move this to https://forum.arctic-sea-ice.net/index.php/topic,2348
(When will the Arctic Go Ice Free?)
Title: Re: Basic questions about melting physics
Post by: petm on September 03, 2019, 12:55:29 AM
There is a brief discussion of latent heat fluxes (which are clearly well understood by climate scientists) mentioned up-thread in part 2 of this video (@~7 min). The whole video is well worth watching, as are all of the channel's videos. Solid, current climate science explained well in laymen's terms.

https://www.youtube.com/watch?v=uBngaoG_-6A

PS. Should I move this to a different thread, and where?
Title: Re: Basic questions about melting physics
Post by: Klondike Kat on September 03, 2019, 03:56:31 AM
Thanks crandles.  Will do.
Title: Re: Basic questions about melting physics
Post by: nanning on September 03, 2019, 07:43:44 AM
binntho, you have me mixed up with crandles. It was his/her find and posts:
https://forum.arctic-sea-ice.net/index.php/topic,2709.msg226369.html#msg226369
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg226396.html#msg226396
Title: Re: Basic questions about melting physics
Post by: binntho on September 03, 2019, 07:58:49 AM
binntho, you have me mixed up with crandles. It was his/her find and posts:
https://forum.arctic-sea-ice.net/index.php/topic,2709.msg226369.html#msg226369
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg226396.html#msg226396

You are quite right nanning - my mistake, I've corrected it in the post above. Thanks!

EDIT: I've moved the post to the "When will the Arctic go Ice Free" thread as suggested by Crandles. Seems like I'm just now waking up, after 2 hours of hectic activity!

https://forum.arctic-sea-ice.net/index.php/topic,2348.msg226465.html#msg226465
Title: Re: Basic questions about melting physics
Post by: Feeltheburn on September 23, 2019, 09:33:23 AM
Felltheburn,

To some extent, you are thinking along the right lines. Alternatively, you are messing up some of the basic physics.

As long as we are in the Tropics, everything is honkydory. Most physical processes take place well above 0C (or 273K). It is when you start using calories and F, your problems begin.

When in the Sub-tropics, some of the precipitation comes down as hail. In recent years, we have seen an increasing hail diameter and more devastating hailstorms spreading north. This may be a sign of the kind of physics you focus on. More evaporative cooling in combination with more humid air should eventually lead to bigger hail, if condensation nuclei are present.

Moving to Mid-latitudes, we begin to have the change-over from freezing rain to warm rain. Apparently, you have forgot to include the temperature of the falling rain. All heat evaporated is not simply sent out to outer space. Some of it will return to Earth as a mild, warm rain, where you would even enjoy getting your underpants wet from time to time.

Now, finally to the physical processes in the Arctic. Your idea that all evaporative cooling will eventually leave the Arctic cold and the World in thermal balance (had it not been for the wicked ocean heat storage), is simply wrong. The moisture advected from southerly latitudes (as well as the minor part of the moisture evaporated from open Arctic waters), will eventually have to come down again as either rain (above 0C), or as snow. In the latter case, we may see the opposite of "sublimation" - that is water vapour going directly into the frozen phase - which of course releases a lot more energy, than just converting water vapour directly into rain.

In the presence of cloud condensation nuclei, we will see hailstorms spreading north, and we will see rain and showers entering the Arctic during winter. What we have not seen yet, is the physical reaction from/to a clean - basically CCN-free - Arctic atmosphere. My guess would be that initially, we will see ice pellets, but eventually we will see drizzle as the Arctic temperatures during winter goes above 0C.

Sitting in Svalbard through the dark "drizzle season" is no great joy I would presume. Maybe it will be a great time to reflect on the basic physics of our time.

Cheers P

Thank you for your thoughtful response. Just trying to understand processes that no doubt affect weather, which is dynamic, but which may not be well accounted for in the climate models.