emordnilap wrote:
As woodburner pointed out, a tremendous amount of energy is going into melting the poles and Greenland (along with ice and snow in other parts of the world). Once they're gone, where is this energy to go?
Good question. The latent heat of fusion of water is 333 kJ per kg, whereas the specific heat capacity of water is 4.18 kJ per kg. so, 333 kJ of energy can melt a kg of ice, or it can raise a kg of water by 80 deg. C. I think I've got that right?
So...is that scary? Or is it simply scary?
Well personally, I'd rate it as pretty f**cking terrifying, especially if you are a sea-creature or live on low-lying land like an estuary in Eastern Scotland. (Oh..wait..)
(Actually, the opportunity to forage for shellfish and the fertile ground for growing stuff in these parts trumps the medium term risk of sea-level rise in my books. Besides, we can always bug out to the woodland, which is quite a bit higher).
Humour me. A lump of energy turns a lump of ice to water but doesn't raise its temperature. That same size lump of energy raises that water by 80°?
I experience pleasure and pains, and pursue goals in service of them, so I cannot reasonably deny the right of other sentient agents to do the same - Steven Pinker
Water has the highest specific heats of any known molecule. Chemically water is really weird stuff. The solid phase is LESS dense than the liquid phase! It is the chemical for which the term 'hydrogen bonding' was invented. It's molecular shape is a fairly simple 'bent stick' but the angle of the bend gives it very interesting pseudo crystaline properties. It has an extremely high surface tension allowing small creatures to walk across its liquid phase surface.
emordnilap wrote:Humour me. A lump of energy turns a lump of ice to water but doesn't raise its temperature. That same size lump of energy raises that water by 80°?
RalphW wrote:Correct.
Thanks for the clarification. So it's not simply scary. It's scary.
I experience pleasure and pains, and pursue goals in service of them, so I cannot reasonably deny the right of other sentient agents to do the same - Steven Pinker
Of course Greenland ice doesn't actually have to boil. That 2257 kJ/kg of latent heat of evaporation is absorbed when water evaporates, as in when you hang your towel up to dry.
If the atmospheric water vapour increases (as it is doing) we have a big energy sink. This may be a bigger effect than that of ice melting.
Good point. We could get some interesting temperature variations here in Eastern Scotland. We already experience the Fohn effect, when moist air from the Atlantic rises over the mountains, dumps its moisture and then heats up as its pressure rises when descending on the lea side. They get the same thing in Calgary, with moist Pacific air coming over the Rockies. They call the winds Chinnooks, or "snow melters".
I imagine moister air would lead to a more pronounced effect.
The physics of water at the molecular level is in fact so weird that, so I'm told, it isn't yet fully understood. There are 8 different possible structures of ice (depending on pressure and temp) and a (fictional) 9th one in Mr Vonnegut's story Cat's Cradle, that instantly "froze" any water it touched.
Can anyone clarify an aspect of the GIS internal melt dynamics for me ?
It's tempting to accept that 80kgs of water at 1.0C in a sunny 5 kilometer melt-pool on the surface
- when it melts open its winter-choked moulin and drains down it in a couple of hours
- will melt 1.0kg of ice that is at the transition temperature,
but this sounds too simple.
I think there are far too many variables to give a simple answer. The sea ice is to a gretaer or lesser extent saline (mixed with salt). The dynamics of sea ice melt include top melt, bottom melt, side melt, water column mixing (as both temperature and salinity vary with depth and time) sea currents, wave action, cloud cover (low or high level) , albido, winds, atmospheric pressure, air temperature and insolation. The ice itself varies in density and depth with age. I've probably missed a few.
Nevan's blog and forum is the best place I've found for the intelligent non-specialist.
RalphW wrote:I think there are far too many variables to give a simple answer. The sea ice is to a gretaer or lesser extent saline (mixed with salt). The dynamics of sea ice melt include top melt, bottom melt, side melt, water column mixing (as both temperature and salinity vary with depth and time) sea currents, wave action, cloud cover (low or high level) , albido, winds, atmospheric pressure, air temperature and insolation. The ice itself varies in density and depth with age. I've probably missed a few.
Nevan's blog and forum is the best place I've found for the intelligent non-specialist.
[edit] Trust me to spout off before reading the comment. Nevan's forum
also talks about the Greenland Ice Sheet.
He has a very good writing style. His writing also reads as very technically authoritative. However, I have no way of personally verifying that as my science in this area is pretty sketchy. Is there anything known anything about his background? Who he actually is, in other words?
Ralph - thanks for your response, albeit at cross purposes. The internal melt of the Greenland Ice Sheet looks like one of the hidden issues that will act as an unexpected multiplier the longer it's allowed to continue.
Getting a quantification of its current rate - as a ratio of sun-warmed meltwater draining down the moulins, looks the best course for promoting public awareness of its threat.
stevecook172001 wrote:He has a very good writing style. His writing also reads as very technically authoritative. However, I have no way of personally verifying that as my science in this area is pretty sketchy. Is there anything known anything about his background? Who he actually is, in other words?
This is a fundamental problem isn't it? If even scientifically-educated people like (many of) us don't know quite enough to tell whether someone who appears to be an expert has got it right, or is telling the truth, what hope have the rest of the Great British (and everybody else's) Public, who are experts on other things, such as the work that takes up so much of their time and energy?? And so we have instead to try and second-guess the author's motives. I have often found myself in this situation.
Bizarrely, Mr Spengler writes about a kind of "peak science" which a given civilisation reaches due to a cross between this effect, and the "buying" of scientific research by large vested interests, which results in untrustworthy findings.
Wisdom includes the ability to assess the worth of what is said when one does not know much of the subject. The methodology of science includes some standard ways to help in this task.
(My judgement is that Neven's blog is worth reading.)
