Australian Politics Forum - Arctic summer temperatures warmest for 120,000 yrs

Chimp_Logic

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Re: Arctic summer temperatures warmest for 120,000 yrs
Reply #180 - Nov 17^th, 2013 at 3:27pm

# wrote on Nov 17^th, 2013 at 1:28pm:

Chimp_Logic wrote on Nov 17^th, 2013 at 1:14pm:

# wrote on Nov 17^th, 2013 at 1:02pm:

Chimp_Logic wrote on Nov 17^th, 2013 at 12:56pm:

...
even amateur scientists ...

Again, you're confusing amateur scientists with amateurs who aren't scientists.

at least they understand why frozen water cannot undergo sublimation at atmospheric pressures.
...

Do you have a freezer?

you cant change the Triple point of water in the P-T phase diagram - you do realise this is a property of water?

It means that sublimation of frozen water cannot occur above the triple point. ie (0.01 C, 0.00603 ATM)

You can freeze water to whatever temperature below zero that you want, it will not undergo sublimation unless the pressure is below 0.00603 ATM (ie vacuum conditions)

You have a freezer that is under 0.00603 ATM?

You must be in the Freeze Drying industry - check out how they freeze dry products. (hint under vacuum conditions)

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lee Gold Member Offline Australian Politics Posts: 21609 Gender:	Re: Arctic summer temperatures warmest for 120,000 yrs Reply #181 - Nov 17^th, 2013 at 3:28pm AS I said as an aggregator the source of the article is given if you don't want to believe the first point of contact. In other words links to livescience, nature whatever.
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muso

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Re: Arctic summer temperatures warmest for 120,000 yrs
Reply #182 - Nov 17^th, 2013 at 3:29pm

Chimp_Logic wrote on Nov 17^th, 2013 at 1:14pm:

at least they understand why frozen water cannot undergo sublimation at atmospheric pressures.

And they don't try to hide from their mistakes by deflections and garbage

Chimp - it's a very slow process which is part and parcel of glacial ablation. It's commonly referred to as sublimation, because there is no obvious water phase involved. In point of fact, there is a sub-microscopic layer of water.

Google is your friend. You'll find many glaciology papers that deal with the phenomenon of sublimation.

By the way, you yourself are exhibiting the behaviour of a true sceptic. You question everything. That's a good thing. Let's move on.

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muso Gold Member Offline Posts: 13151 Gladstone, Queensland Gender:	Re: Arctic summer temperatures warmest for 120,000 yrs Reply #183 - Nov 17^th, 2013 at 3:33pm Chimp_Logic wrote on Nov 17^th, 2013 at 3:27pm: It means that sublimation of frozen water cannot occur above the triple point. ie (0.01 C, 0.00603 ATM) Chimp, Can you get pure water in liquid phase below 0 degrees C at 101.325 kpa ? The Phase Diagram says no. What do you say?
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Chimp_Logic

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Re: Arctic summer temperatures warmest for 120,000 yrs
Reply #184 - Nov 17^th, 2013 at 3:39pm

muso wrote on Nov 17^th, 2013 at 3:33pm:

Chimp_Logic wrote on Nov 17^th, 2013 at 3:27pm:

It means that sublimation of frozen water cannot occur above the triple point. ie (0.01 C, 0.00603 ATM)

Chimp, Can you get pure water in liquid phase below 0 degrees C at 101.325 kpa ? The Phase Diagram says no. What do you say?

can you get ice in the ocean at 2 deg C?

The question muso and # is whether ice can undergo sublimation at atmospheric pressure. (no where near low enough pressures)

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muso Gold Member Offline Posts: 13151 Gladstone, Queensland Gender:	Re: Arctic summer temperatures warmest for 120,000 yrs Reply #185 - Nov 17^th, 2013 at 3:46pm You're not listening. The phase diagram refers to equilibrium conditions. It doesn't allow for kinetics.
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Chimp_Logic

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Re: Arctic summer temperatures warmest for 120,000 yrs
Reply #186 - Nov 17^th, 2013 at 3:46pm

muso wrote on Nov 17^th, 2013 at 3:29pm:

Chimp_Logic wrote on Nov 17^th, 2013 at 1:14pm:

at least they understand why frozen water cannot undergo sublimation at atmospheric pressures.

And they don't try to hide from their mistakes by deflections and garbage

Chimp - it's a very slow process which is part and parcel of glacial ablation. It's commonly referred to as sublimation, because there is no obvious water phase involved. In point of fact, there is a sub-microscopic layer of water.

Google is your friend. You'll find many glaciology papers that deal with the phenomenon of sublimation.

By the way, you yourself are exhibiting the behaviour of a true sceptic. You question everything. That's a good thing. Let's move on.

...just saying that ice cannot undergo sublimation at atmospheric pressure - you do understand what the triple point of water is in a standard pressure-temperature phase diagram?

We are not talking about mono-atomic film thicknesses of water.

What is the minimum number of Water molecules that you need to be able to distinguish or characterise the state these water molecules are in?

This is a Quantum Physics problem.

Dry Ice undergoes sublimation very easily at atmospheric pressures - and that's because its triple point is (-56.6 deg C, 5.11 atm). The triple point for water is (0.01 degC, 0.00603 atm)

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Chimp_Logic Gold Member Offline πολιτικός Posts: 4826 Mawson Base Gender:	Re: Arctic summer temperatures warmest for 120,000 yrs Reply #187 - Nov 17^th, 2013 at 3:49pm muso wrote on Nov 17^th, 2013 at 3:46pm: You're not listening. The phase diagram refers to equilibrium conditions. It doesn't allow for kinetics. Explain the mechanism whereby frozen ice can undergo sublimation at atmospheric pressure conditions - use all the Kinetics you like
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muso Gold Member Offline Posts: 13151 Gladstone, Queensland Gender:	Re: Arctic summer temperatures warmest for 120,000 yrs Reply #188 - Nov 17^th, 2013 at 4:11pm Why does water ice have a vapour pressure?
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muso

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Re: Arctic summer temperatures warmest for 120,000 yrs
Reply #189 - Nov 17^th, 2013 at 4:40pm

http://www.igsoc.org:8080/journal/57/204/t10J220.pdf

Quote:

684 Journal of Glaciology, Vol. 57, No. 204, 2011

Sublimation and surface energy budget of Taylor Glacier,
Antarctica

Andrew K. BLISS,Kurt M. CUFFEY, Jeffrey L. KAVANAUGH

Department of Geography, University of California Berkeley, 507 McCone Hall, Berkeley, California 94720-4740, USA
E-mail: andybliss@gmail.com

Department of Earth & Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada

ABSTRACT.

Taylor Glacier, an outlet of the East Antarctic ice sheet, flows through the Transantarctic Mountains and terminates in the Dry Valleys. Understanding how this glacier fluctuates is important for studies of glacial geology, paleoclimate, ice dynamics and ecology. Sublimation is the primary mass-loss process for most of the glacier. Four years of specific balance measurements from the ablation zone show sublimation rates up to 40cm a−1 1.
We used data from an array of weather stations as inputs to a model for latent heat flux and hence sublimation rate. Calculated and measured ablation rates agree to within uncertainties, indicating that wind speed and vapour pressure gradient (a function of temperature and humidity) are the governing variables, as expected from theory. Measurements and model results together allowed us to examine the spatial and temporal variations of sublimation on the glacier. On average, sublimation is about two times faster in summer than winter. Rapid sublimation occurs during storms and katabatic wind events, but such periods contribute less to the annual total than do slow, persistent losses. Spatially, sublimation reaches a maximum midway along the glacier, where descending surface air currents are focused by the topography of the aptly named tributary, Windy Gully.

Imagine extremely cold dry air that is water saturated blowing into a slightly warmer environment (but still sub zero). The vapour pressure of the ice is greater than the partial pressure of water in the warming air. The result is that water vapour will partition into the flowing air (wind) causing ablation of the ice. It is commonly referred to as sublimation regardless of the actual mechanism, which involves an ultra thin film of liquid water far below freezing point.

This is a reputable journal, and the physical chemistry is robust.

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Chimp_Logic Gold Member Offline πολιτικός Posts: 4826 Mawson Base Gender:	Re: Arctic summer temperatures warmest for 120,000 yrs Reply #190 - Nov 17^th, 2013 at 5:30pm muso wrote on Nov 17^th, 2013 at 4:11pm: Why does water ice have a vapour pressure? Explain how ice can undergo sublimation at conditions above the Triple point
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# Gold Member Offline A fool is certain: an ignorant fool, absolutely so Posts: 2603	Re: Arctic summer temperatures warmest for 120,000 yrs Reply #191 - Nov 17^th, 2013 at 6:34pm Chimp_Logic wrote on Nov 17^th, 2013 at 5:30pm: muso wrote on Nov 17^th, 2013 at 4:11pm: Why does water ice have a vapour pressure? Explain how ice can undergo sublimation at conditions above the Triple point Can you deny that it does?
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Soren Gold Member Offline Posts: 25654 Gender:	Re: Arctic summer temperatures warmest for 120,000 yrs Reply #192 - Nov 17^th, 2013 at 7:00pm Muso and Chimp arguing - LOVE IT!!! The clash of mathematics and superstition. And since there is no common ground, the result is by no mean certain!! A parable for our time. The multiculturalism of the mind right before our eyes.
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muso

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Re: Arctic summer temperatures warmest for 120,000 yrs
Reply #193 - Nov 17^th, 2013 at 7:53pm

Chimp_Logic wrote on Nov 17^th, 2013 at 5:30pm:

muso wrote on Nov 17^th, 2013 at 4:11pm:

Why does water ice have a vapour pressure?

Explain how ice can undergo sublimation at conditions above the Triple point

I thought I just did that. Anyway, here goes nothing.

An understanding of the process must include investigation of what is happening on the molecular scale. All sorts of "large-scale" phenomena have properties determined by "microscopic" physics.

A phase diagram is a characterization of the overall "macroscopic" system at equilibrium, something we observe at "laboratory-scale". The phenomenon you are asking about concerns physical behavior at the "microscopic" (in this case, molecular) scale. It requires a current of air to work, so the system is not at equilibrium. As we saw from the supercooled water experiment, the phase diagram is not hard and fast for all situations.

At any temperature above 0 K, there will always be a tiny ( the colder it gets, the lesser it gets) fraction of water molecules at the surface of the ice which can obtain a kinetic energy sufficient to overcome the weak intermolecular bonds with their neighbours and escape the surface. In that sense, the process isn't much different from the evaporation of liquid water at temperatures well below the boiling point (for instance, water at 300 K does have a vapor pressure). The sublimation is really slow, but it is there.

You can look at this as being a sub-microscopic layer of liquid supercooled water if you like, but the effect is essentially a slow sublimation.

Now in the Antarctic Dry Valleys, most ablation is caused by Katabatic winds. Do you understand how that works? Katabatic winds are denser than the surrounding atmosphere and they flow downhill as a result of the effect of gravity. These winds are extremely cold and dry as a result.

What can you tell me about the effect of increasing water vapour on the density of air?

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« Last Edit: Nov 17^th, 2013 at 8:41pm by muso »

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muso Gold Member Offline Posts: 13151 Gladstone, Queensland Gender:	Re: Arctic summer temperatures warmest for 120,000 yrs Reply #194 - Nov 17^th, 2013 at 7:59pm Chimp - you seem to have an inability to think outside the box. Another example was the Linear Non Threshold Dose Response for radiation. You don't seem to understand the underlying science. You take the "Rulez is rulez" approach. Don't take this the wrong way, but are you really male?
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