rink_glacier_streamice

A set of input files, shell scripts of code to manage the simulation of a section of western greenland with MITgcm/STREAMICE

The Repository is organised as follows:

• code folder: A set of files that are needed in order to compile MITgcm in order to use the STREAMICE package.
• input folder: A set of text input files to be read by MITgcm at runtime, as well as matlab files which are used to create binary inputs
• archer_scripts folder: A set of files helpful for use on the ARCHER2 supercomputer (Not intended for use at UT)
• ls6_scripts folder: A set of files provided by An Nguyen to enable use on the Lonestar6 supercomputer (in progress)

Note: this readme is a placeholder for a more extensive wiki that will evolve over time. The bare minimum is given below.

Overview of experiment.

This experiment models a section of West Greenland containing Rink, Inngia and Umiammakku Isbrae using the STREAMICE package of MITgcm. A resolution of 600m in a polar stereographic reference grid is used. The geometry of the model (surface elevation and bed elevation) are interpolated from BedMachine Greenland, with "islands" of ice removed. A hybrid stress balance (Goldberg, 2010) is used, with a coulomb-limited velocity-dependent sliding law (Cornford et al, 2020). The ITS_LIVE velocity mosaic is used as a constraint in a control method inversion. The control parameters are $\beta$, the square root of the sliding coefficient, and $\overline{B}$, the vertically averaged ice-sheet stiffness parameter (equivalent to $A^{-1/3}$ where $A$ is Glen's coefficient). An uniform initial guess is used for each; there is no constraint for $\overline{B}$ to match, or be informed by, ice-sheet temperature. Below the results of this inversion are shown: the modelled, observed speed and the difference.

The results took about 30 minutes to generate on 108 cpus on the ARCHER2 supercomputer.

MODELLED SPEED

ITS_LIVE

Steps in running experiment.

Preparing input files.

The input folder contains 3 matlab files:

• snip.m defines the domain and the grid locations, and subsets the ITS_LIVE and BM-Greenland files for easier use later on.
• gen_mesh.m defines the number of cpus (npx and npy), determines the size of the computational domain (i.e. by "padding" noncomputational cells to ensure the appropriate tile size). Calls setup_experiment.m
• setup_experiment.m. Creates binary input files needed for experiment.

The order of processing is (i) snip.m, (ii) gen_mesh.m.

Additionally the input folder contains the parameter input files needed. Note the parameters in data.streamice are explained here.

Compiling on TACC resources.

TBC.

Running on TACC resources.

TBC

Goldberg, D N (2011). A variationally-derived, depth-integrated approximation to the Blatter/Pattyn balance. J. of Glaciology, 57, 157-170.

Cornford, S and others (2020). Results of the third Marine Ice Sheet Model Intercomparison Project (MISMIP+). The Cryosphere, 14, 2283–2301. (doi:10.5194/tc-2019-326)