Ground Heat Flux Question

[kkoepnick]

Hi there!

I understand that the ground heat flux, G, is the net heat flux from the atmosphere into the top of the ground. I am interested in the ground heat flux the way this term is used by glaciologists. They mean this ground flux to be the heat flux (also sometimes called subsurface/conductive heat flux) into the deeper ice levels after taking into account the heat loss to melting. This is normally calculated by a vertical temperature diffusion equation of the subsurface layers. Is this glaciological ground heat flux saved as an output variable or can it be calculated as a residual of variables outputted by the model (CESM1).

Specifically, I wonder if this ground flux is the FGR - FSM (where FSM is the snow melt heat flux). In that case, is a diffusion equation used to calculate FSM? In addition, what happens if the ice is directly exposed with no snow layer (only ice)?

Thank you in advance for any tips/hints!

Best,
Kirstin

 

[slevis]

Hi Kirstin,

I don't know off the top of my head, though you seem to be thinking about this in a reasonable way.

One suggestion is to look in the CLM Technote and/or the CLM code for an explanation of FSM:

2. CLM Technical Note — ctsm release-clm5.0 documentation

@sacks do you have feedback on Kirstin's last question?

 

[sacks]

I'm not sure about this, either, but one piece that might help answer your question (which you may or may not be aware of already) is: In glacier columns, the "ground" starts at the top of the ice column, but below the explicitly-simulated snow pack. If there is no snow pack (because the snow has entirely melted in column), then the "ground" in a glacier column is still the top of the ice. I'm not sure if this actually helps with your question. I realized that I'm not sure myself of whether FGR includes the heat into the snow pack or only includes the heat into the ground itself (meaning the soil in vegetated columns or the ice in glacier columns).

I will pass this along to a few people in the Land Ice Working Group to see if any of them can give a better answer.

 

[kkoepnick]

Thank you both for your thoughts! I have looked through the technote as well as the source code and admittedly am still a little stuck and would love confirmation on this ground heat flux. Did you hear back from the Land Ice Working Group? Thank you :)

 

[sacks]

I'm sorry, I haven't heard back from anyone yet.