<p>The way I see the effect on a glacier, the glacier surface is essentially a cooling plate that under melting conditions is always at zero degrees C. If you then consider air a few metres above the surface it will show more of the ambient air temperature for the area (we need to forget about radiation and shading effects for the moment). As the air close to the surface is cooled it is moved downhill and is replaced by the warmer air higher up from the surface. There will thus be a downdraft towards the surface created as the cold air moves down. This is a bit of a simplistic view so we need to consider other factors.</p>
<p>The glacier surface under melting conditions is, of course, melting. The melt is generated by the energy balance at the surface. The energy balance involves radiation fluxes both in short-wave (visible light) and long-wave (infra red, heat). In addition there will be turbulent fluxes cause by air moving across the surface. There will be a turbulent sensible heat flux from convection of air towards the surface. There will also be a turbulent latent heat flux cased by air moisture evaporating or condensation on the surface. In addition rain can also produce melt since rain drops will likely have a temperature higher than the melting point. So this affects the process of cooling the air above the surface due to the turbulence mixing air at the surface with air higher up (still within metres) from the surface. Hence the glacier wind will help cool the air above the glacier because of the turbulent exchange occurring above the glacier surface.</p>
<p>So to get back to the question, I do not see this as a convection cell. The glacier is a cooling plate and warmer air will be constantly supplied and cooled through the wind generated turbulence over the surface. At the lower end the wind will continue downhill but due to moving over ground it can now warm again. This is perhaps described as you write an &quot;infinite sink for cold air&quot;. I am less sure about the &quot;infinite source of cold air&quot; since it is the surface itself that creates the cold air.</p>
<p>Another possible complication to be considered is also that air will warm as it moves down in elevation, Föhn effect. The size of the effect is coupled to the drop in elevation. This means that if the cold air is simply replaced by air residing above the advected cold air, the effect is pretty much negligible but if the air is forced across the surface by larger scale winds then the air reaching the surface may be quite warm and require larger energy fluxes to be cooled. It is unclear from your question how you perceive your model is coupled to the atmosphere surrounding the glacier and it is the processes replacing the cold air that is fuzzy in your model.</p>
<p>Note that I have focused on a melting glacier surface. If the surface and the air is below freezing then the surface one could be both colder or warmer than the other and the surface will not generally be cooling the air, instead the air may warm from moving downhill and perhaps also warm the surface over time. So that is a completely different story.</p>

CC BY-SA 4.0
2024-09-12T14:58:02.477Z
2024-09-12T17:22:55.803Z
2024-09-12T17:22:55.803Z
Peter Jansson
<p>When air close to a glacier surface gets cooled, it becomes heavier and flows down the glacier slope as glacier winds. I am a glaciologist trying to study and model glacier winds. I am confused about whether I should consider this a <strong>circulation</strong>, or not. Usually, winds occur in the form of a circulation, where cold air replaces hot air rising up. For example, land-sea breeze system. In glacier winds, even if there is no replacement of air involved, you would still get a flow (Illustrated below). This is what confuses me.</p>
<p><a href="https://i.sstatic.net/yk6CyLQ0.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/yk6CyLQ0.png" alt="enter image description here" /></a></p>
<p>Unlike the convection cells in a teapot, this is more like the flow of a river down the slope. Should the formation of the circulation cell be considered at all for the modelling of these winds?   I am not an expert in geophysical fluid dynamics, so please excuse me if I said something totally wrong.</p>

<meteorology><wind><glaciology><microclimates>
For glacier winds to exist, are circulation cells needed?
AlphaLife
# For glacier winds to exist, are circulation cells needed?

(Asked by: username_0 on 2024-09-12)

When air close to a glacier surface gets cooled, it becomes heavier and flows down the glacier slope as glacier winds. I am a glaciologist trying to study and model glacier winds. I am confused about whether I should consider this a **circulation**, or not. Usually, winds occur in the form of a circulation, where cold air replaces hot air rising up. For example, land-sea breeze system. In glacier winds, even if there is no replacement of air involved, you would still get a flow (Illustrated below). This is what confuses me.

[![enter image description here](https://i.sstatic.net/yk6CyLQ0.png)](https://i.sstatic.net/yk6CyLQ0.png)

Unlike the convection cells in a teapot, this is more like the flow of a river down the slope. Should the formation of the circulation cell be considered at all for the modelling of these winds? I am not an expert in geophysical fluid dynamics, so please excuse me if I said something totally wrong.

**Tags:** meteorology, wind, glaciology, microclimates


---

## 1 answers

### Answer by username_1 on 2024-09-12. Score: 3

The way I see the effect on a glacier, the glacier surface is essentially a cooling plate that under melting conditions is always at zero degrees C. If you then consider air a few metres above the surface it will show more of the ambient air temperature for the area (we need to forget about radiation and shading effects for the moment). As the air close to the surface is cooled it is moved downhill and is replaced by the warmer air higher up from the surface. There will thus be a downdraft towards the surface created as the cold air moves down. This is a bit of a simplistic view so we need to consider other factors.

The glacier surface under melting conditions is, of course, melting. The melt is generated by the energy balance at the surface. The energy balance involves radiation fluxes both in short-wave (visible light) and long-wave (infra red, heat). In addition there will be turbulent fluxes cause by air moving across the surface. There will be a turbulent sensible heat flux from convection of air towards the surface. There will also be a turbulent latent heat flux cased by air moisture evaporating or condensation on the surface. In addition rain can also produce melt since rain drops will likely have a temperature higher than the melting point. So this affects the process of cooling the air above the surface due to the turbulence mixing air at the surface with air higher up (still within metres) from the surface. Hence the glacier wind will help cool the air above the glacier because of the turbulent exchange occurring above the glacier surface.

So to get back to the question, I do not see this as a convection cell. The glacier is a cooling plate and warmer air will be constantly supplied and cooled through the wind generated turbulence over the surface. At the lower end the wind will continue downhill but due to moving over ground it can now warm again. This is perhaps described as you write an "infinite sink for cold air". I am less sure about the "infinite source of cold air" since it is the surface itself that creates the cold air.

Another possible complication to be considered is also that air will warm as it moves down in elevation, Föhn effect. The size of the effect is coupled to the drop in elevation. This means that if the cold air is simply replaced by air residing above the advected cold air, the effect is pretty much negligible but if the air is forced across the surface by larger scale winds then the air reaching the surface may be quite warm and require larger energy fluxes to be cooled. It is unclear from your question how you perceive your model is coupled to the atmosphere surrounding the glacier and it is the processes replacing the cold air that is fuzzy in your model.

Note that I have focused on a melting glacier surface. If the surface and the air is below freezing then the surface one could be both colder or warmer than the other and the surface will not generally be cooling the air, instead the air may warm from moving downhill and perhaps also warm the surface over time. So that is a completely different story.


---

