Yes. This happens in places where the ambient temperature exceeds 0 degrees C for at least one part of the year.

Good information, but I stand by my previous posts.

muso wrote on Nov 22^nd, 2013 at 10:35am:


youre getting closer muso

Its taking a lot of energy and time to drag out the underlying mechanism from your decaying public carcass

It will come muso

be patient.

Your task is incomplete.

Chimp_Logic wrote on Nov 22^nd, 2013 at 10:40am:


We're going from the sublime to the ridiculous. I don't need any clues. You need to get one. I thought you were going to phone a friend. Maybe she can help you get a clue.

At the McMurdo Dry Valleys, the temperature doesn't exceed zero degrees. Well, it's rare. Yet any ice that accumulates  sublimates pretty quickly due to katabatic winds dropping off the ice shelf. Low partial pressure of water (below the triple point pressure) => True sublimation. 

No liquid film involved.

We're speaking here about the conditions in the Antarctic dry valleys and the conditions that result in sublimation.

At any temperature above 0 K, there will always be a tiny   fraction of water molecules at the surface of the ice which can obtain a kinetic energy sufficient to overcome the weak intermolecular bonds (weak hydrogen bond) 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 process is endothermic. The Heat of Sublimation (ΔHsub)
is 333.5 kJ/kg. This heat comes from the environment. Katabatic winds have speeds up to 300km/hr. The temperature of the air itself is extremely low, so the sublimation is energy limited.

Obviously where the conditions are clear, the extra energy comes from the sun. 

I have no doubt that for glaciers in just about any other location, melting and interstitial water are significant factors in the ablation process, but the extremely low ambient temperatures at the Dry Valleys of Antarctica make this unlikely.  When the sublimation curve is crossed, the substance changes directly from solid to gas.

So is sublimation possible at normal atmospheric pressure? Yes of course it is.  The Phase Diagram you quoted was for a single component, namely water. The Pressure referred to is the Vapour pressure of water (Partial Pressure to be precise) , which is a tiny fraction of atmospheric pressure at low ambient temperatures.

Now depending on the exact circumstances, the katabatic wind may actually be close to its dewpoint, but of course, the absolute humidity is extremely low.  The rate of sublimation is determined by the wind velocity, temperature, dewpoint of the katabatic wind and incident solar energy.

Happy?