how_MOM_inits_grid

This outlines how MOM6 initialises from a restart file, with particular focus on the grid structure.
This should inform the subsequent steps including changing bathymetry, lateral redistribution of mass and tracers, and 
re-initialisation of the model.

## working Notes ##

There seems to be a file called MOM_horizontal_regridding.F90 which is called in initialization/MOM_state_initialization.F90. Could this somehow just solve our problems from the get-go? Nope!


The config driver (either solo_driver or the coupler) will call initialize_MOM. This is within the main module of MOM: MOM.F90 (/src/MOM6/src/core/MOM.F90) 

!!! initialize_MOM !!!
	Initialize MOM, including memory allocation, setting up parameters and diagnostics,
	initializing the ocean state variables, and initializing subsidiary modules
	1) get_MOM_input - gets parameter files, dir paths and restart files

	This is followed by a lot of param defs from MOM_input.
    
    2) MOM_domains_init !!! (MOM6/src/framework/MOM_domains.F90)
	Sets up MOM domains and grids - deals with assigning PEs etc, not of interest to us.

	3) hor_index_init

	4) create_dyn_horgrid

	5) verticalGridInit 
	GV => CS%GV

	6) MOM_initialize_fixed(dG, CS%OBC, param_file, write_geom_files, dirs%output_directory)
!!! 





subroutine ocean_model_init (/src/MOM6/config_src/coupled_driver/ocean_model_MOM.F90)
	
	1 - Model allocates surface state and surface forcing via 
	call allocate_surface_state (defined in MOM6/src/core/MOM_variables.F90)
	call surface_forcing_init (defined in MOM6/config_src/coupled_driver/MOM_surface_forcing.F90)

	a.s.s simply initialises the data structures for surface variables such as sst, sss, rho, u, v etc and sets them to 0.

	2 - initialize_ocean_public_type (define in MOM6/config_src/coupled_driver/ocean_model_MOM.F90)