[MITgcm-support] SHELFICE Boundary Layer Parameterization

Miller, Sara G smiller85 at gatech.edu
Wed Jun 2 16:20:43 EDT 2021


Hello all,

I am trying to understand the treatment of the ice-ocean boundary layer in the SHELFICE package. My goal is to use MITgcm to model a dynamic, global ice shell over an ocean on Jupiter's moon Europa. I believe the SHELFICE package will be useful for me, but I do not fully understand the description given in the user manual regarding boundary layer modeling.

What is the total tendency and how is it used in the calculation of the boundary layer temperature at a future time step? The boundary layer temperature and freezing/melting information feels like a chicken-and-egg problem. It would make sense to me that you need to know the temperature in the BL to determine if you're in the freezing or melting regime, but MITgcm shows boundary layer temperature as a function of that total tendency term which I think captures the freezing/melting information.

More fundamentally, how do you melt the ice in MITgcm? Does it slowly melt until it passes the threshold to step up to the next grid, or does its pressure just change? That is, the ice base is always the first grid cell, and as it melts upwards the pressure term just changes with it. I am new to modeling, but I don’t understand why we’re working in fractions of a grid cell instead of just making the grid more densely-spaced in the boundary layer region.

I apologize for the volume of questions in a single email! I appreciate any and all wisdom/advice.

Best regards,
Sara

---
Sara G. Miller (she/her)
PhD Student
Georgia Institute of Technology
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