mom_ocean_model_mct.F90

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!> Top-level module for the MOM6 ocean model in coupled mode.
module mom_ocean_model_mct
 
! This file is part of MOM6. See LICENSE.md for the license.
 
! This is the top level module for the MOM6 ocean model.  It contains routines
! for initialization, termination and update of ocean model state.  This
! particular version wraps all of the calls for MOM6 in the calls that had
! been used for MOM4.
!
! This code is a stop-gap wrapper of the MOM6 code to enable it to be called
! in the same way as MOM4.
 
use mom,                     only : initialize_mom, step_mom, mom_control_struct, mom_end
use mom,                     only : extract_surface_state, allocate_surface_state, finish_mom_initialization
use mom,                     only : get_mom_state_elements, mom_state_is_synchronized
use mom,                     only : get_ocean_stocks, step_offline
use mom_constants,           only : celsius_kelvin_offset, hlf
use mom_diag_mediator,       only : diag_ctrl, enable_averaging, disable_averaging
use mom_diag_mediator,       only : diag_mediator_close_registration, diag_mediator_end
use mom_domains,             only : pass_var, pass_vector, agrid, bgrid_ne, cgrid_ne
use mom_domains,             only : to_all, omit_corners
use mom_error_handler,       only : mom_error, fatal, warning, is_root_pe
use mom_error_handler,       only : calltree_enter, calltree_leave
use mom_file_parser,         only : get_param, log_version, close_param_file, param_file_type
use mom_forcing_type,        only : allocate_forcing_type
use mom_forcing_type,        only : forcing, mech_forcing
use mom_forcing_type,        only : forcing_accumulate, copy_common_forcing_fields
use mom_forcing_type,        only : copy_back_forcing_fields, set_net_mass_forcing
use mom_forcing_type,        only : set_derived_forcing_fields
use mom_forcing_type,        only : forcing_diagnostics, mech_forcing_diags
use mom_get_input,           only : get_mom_input, directories
use mom_grid,                only : ocean_grid_type
use mom_io,                  only : close_file, file_exists, read_data, write_version_number
use mom_marine_ice,          only : iceberg_forces, iceberg_fluxes, marine_ice_init, marine_ice_cs
use mom_restart,             only : mom_restart_cs, save_restart
use mom_string_functions,    only : uppercase
use mom_surface_forcing_mct, only : surface_forcing_init, convert_iob_to_fluxes
use mom_surface_forcing_mct, only : convert_iob_to_forces, ice_ocn_bnd_type_chksum
use mom_surface_forcing_mct, only : ice_ocean_boundary_type, surface_forcing_cs
use mom_surface_forcing_mct, only : forcing_save_restart
use mom_time_manager,        only : time_type, get_time, set_time, operator(>)
use mom_time_manager,        only : operator(+), operator(-), operator(*), operator(/)
use mom_time_manager,        only : operator(/=), operator(<=), operator(>=)
use mom_time_manager,        only : operator(<), real_to_time_type, time_type_to_real
use mom_tracer_flow_control, only : call_tracer_register, tracer_flow_control_init
use mom_tracer_flow_control, only : call_tracer_flux_init
use mom_unit_scaling,        only : unit_scale_type
use mom_variables,           only : surface
use mom_verticalgrid,        only : verticalgrid_type
use mom_ice_shelf,           only : initialize_ice_shelf, shelf_calc_flux, ice_shelf_cs
use mom_ice_shelf,           only : add_shelf_forces, ice_shelf_end, ice_shelf_save_restart
use coupler_types_mod,       only : coupler_1d_bc_type, coupler_2d_bc_type
use coupler_types_mod,       only : coupler_type_spawn, coupler_type_write_chksums
use coupler_types_mod,       only : coupler_type_initialized, coupler_type_copy_data
use coupler_types_mod,       only : coupler_type_set_diags, coupler_type_send_data
use mpp_domains_mod,         only : domain2d, mpp_get_layout, mpp_get_global_domain
use mpp_domains_mod,         only : mpp_define_domains, mpp_get_compute_domain, mpp_get_data_domain
use fms_mod,                 only : stdout
use mpp_mod,                 only : mpp_chksum
use mom_eos,                 only : gsw_sp_from_sr, gsw_pt_from_ct
use mom_wave_interface,      only: wave_parameters_cs, mom_wave_interface_init
use mom_wave_interface,      only: mom_wave_interface_init_lite, update_surface_waves
 
! MCT specfic routines
use mom_domains,             only : mom_infra_end
 
#include <MOM_memory.h>
 
#ifdef _USE_GENERIC_TRACER
use mom_generic_tracer, only : mom_generic_tracer_fluxes_accumulate
#endif
 
implicit none ; public
 
public ocean_model_init, ocean_model_end, update_ocean_model
public ocean_model_save_restart, ocean_stock_pe
public ice_ocean_boundary_type
public ocean_model_init_sfc, ocean_model_flux_init
public ocean_model_restart
public ice_ocn_bnd_type_chksum
public ocean_public_type_chksum
public get_ocean_grid
 
!> This type is used for communication with other components via the FMS coupler.
!! The element names and types can be changed only with great deliberation, hence
!! the persistnce of things like the cutsy element name "avg_kount".
type, public ::  ocean_public_type
  type(domain2d) :: domain    !< The domain for the surface fields.
  logical :: is_ocean_pe      !< .true. on processors that run the ocean model.
  character(len=32) :: instance_name = '' !< A name that can be used to identify
                              !! this instance of an ocean model, for example
                              !! in ensembles when writing messages.
  integer, pointer, dimension(:) :: pelist => null()   !< The list of ocean PEs.
  logical, pointer, dimension(:,:) :: maskmap =>null() !< A pointer to an array
                    !! indicating which logical processors are actually used for
                    !! the ocean code. The other logical processors would be all
                    !! land points and are not assigned to actual processors.
                    !! This need not be assigned if all logical processors are used.
 
  integer :: stagger = -999   !< The staggering relative to the tracer points
                    !! points of the two velocity components. Valid entries
                    !! include AGRID, BGRID_NE, CGRID_NE, BGRID_SW, and CGRID_SW,
                    !! corresponding to the community-standard Arakawa notation.
                    !! (These are named integers taken from mpp_parameter_mod.)
                    !! Following MOM5, stagger is BGRID_NE by default when the
                    !! ocean is initialized, but here it is set to -999 so that
                    !! a global max across ocean and non-ocean processors can be
                    !! used to determine its value.
  real, pointer, dimension(:,:)  :: &
    t_surf => null(), &  !< SST on t-cell (degrees Kelvin)
    s_surf => null(), &  !< SSS on t-cell (psu)
    u_surf => null(), &  !< i-velocity at the locations indicated by stagger, m/s.
    v_surf => null(), &  !< j-velocity at the locations indicated by stagger, m/s.
    sea_lev => null(), & !< Sea level in m after correction for surface pressure,
                         !! i.e. dzt(1) + eta_t + patm/rho0/grav (m)
    frazil =>null(), &   !< Accumulated heating (in Joules/m^2) from frazil
                         !! formation in the ocean.
    melt_potential => null(), & !< Instantaneous heat used to melt sea ice (in J/m^2)
    area => null(), &    !< cell area of the ocean surface, in m2.
    obld => null()       !< Ocean boundary layer depth, in m.
  type(coupler_2d_bc_type) :: fields    !< A structure that may contain named
                                        !! arrays of tracer-related surface fields.
  integer                  :: avg_kount !< A count of contributions to running
                                        !! sums, used externally by the FMS coupler
                                        !! for accumulating averages of this type.
  integer, dimension(2)    :: axes = 0  !< Axis numbers that are available
                                        !! for I/O using this surface data.
end type ocean_public_type
 
!> The ocean_state_type contains all information about the state of the ocean,
!! with a format that is private so it can be readily changed without disrupting
!! other coupled components.
type, public :: ocean_state_type ;
  ! This type is private, and can therefore vary between different ocean models.
  logical :: is_ocean_pe = .false.  !< True if this is an ocean PE.
  type(time_type) :: time     !< The ocean model's time and master clock.
  integer :: restart_control  !< An integer that is bit-tested to determine whether
                              !! incremental restart files are saved and whether they
                              !! have a time stamped name.  +1 (bit 0) for generic
                              !! files and +2 (bit 1) for time-stamped files.  A
                              !! restart file is saved at the end of a run segment
                              !! unless Restart_control is negative.
 
  integer :: nstep = 0        !< The number of calls to update_ocean.
  logical :: use_ice_shelf    !< If true, the ice shelf model is enabled.
  logical :: use_waves        !< If true use wave coupling.
 
  logical :: icebergs_alter_ocean !< If true, the icebergs can change ocean the
                              !! ocean dynamics and forcing fluxes.
  logical :: restore_salinity !< If true, the coupled MOM driver adds a term to
                              !! restore salinity to a specified value.
  logical :: restore_temp     !< If true, the coupled MOM driver adds a term to
                              !! restore sst to a specified value.
  real :: press_to_z          !< A conversion factor between pressure and ocean
                              !! depth in m, usually 1/(rho_0*g), in m Pa-1.
  real :: c_p                 !< The heat capacity of seawater, in J K-1 kg-1.
  logical :: offline_tracer_mode = .false. !< If false, use the model in prognostic mode
                              !! with the barotropic and baroclinic dynamics, thermodynamics,
                              !! etc. stepped forward integrated in time.
                              !! If true, all of the above are bypassed with all
                              !! fields necessary to integrate only the tracer advection
                              !! and diffusion equation read in from files stored from
                              !! a previous integration of the prognostic model.
 
  logical :: single_step_call !< If true, advance the state of MOM with a single
                              !! step including both dynamics and thermodynamics.
                              !! If false, the two phases are advanced with
                              !! separate calls. The default is true.
  ! The following 3 variables are only used here if single_step_call is false.
  real    :: dt               !< (baroclinic) dynamics time step (seconds)
  real    :: dt_therm         !< thermodynamics time step (seconds)
  logical :: thermo_spans_coupling !< If true, thermodynamic and tracer time
                              !! steps can span multiple coupled time steps.
  logical :: diabatic_first   !< If true, apply diabatic and thermodynamic
                              !! processes before time stepping the dynamics.
 
  type(directories) :: dirs   !< A structure containing several relevant directory paths.
  type(mech_forcing) :: forces !< A structure with the driving mechanical surface forces
  type(forcing)   :: fluxes   !< A structure containing pointers to
                              !! the thermodynamic ocean forcing fields.
  type(forcing)   :: flux_tmp !< A secondary structure containing pointers to the
                              !! ocean forcing fields for when multiple coupled
                              !! timesteps are taken per thermodynamic step.
  type(surface)   :: sfc_state !< A structure containing pointers to
                              !! the ocean surface state fields.
  type(ocean_grid_type), pointer :: &
    grid => null()            !< A pointer to a grid structure containing metrics
                              !! and related information.
  type(verticalgrid_type), pointer :: &
    gv => null()              !< A pointer to a structure containing information
                              !! about the vertical grid.
  type(unit_scale_type), pointer :: us => null() !< A pointer to a structure containing
                              !! dimensional unit scaling factors.
  type(mom_control_struct), pointer :: &
    mom_csp => null()         !< A pointer to the MOM control structure
  type(ice_shelf_cs), pointer :: &
    ice_shelf_csp => null()   !< A pointer to the control structure for the
                              !! ice shelf model that couples with MOM6.  This
                              !! is null if there is no ice shelf.
  type(marine_ice_cs), pointer :: &
    marine_ice_csp => null()  !< A pointer to the control structure for the
                              !! marine ice effects module.
  type(wave_parameters_cs), pointer :: &
    waves !< A structure containing pointers to the surface wave fields
  type(surface_forcing_cs), pointer :: &
    forcing_csp => null()     !< A pointer to the MOM forcing control structure
  type(mom_restart_cs), pointer :: &
    restart_csp => null()     !< A pointer set to the restart control structure
                              !! that will be used for MOM restart files.
  type(diag_ctrl), pointer :: &
    diag => null()            !< A pointer to the diagnostic regulatory structure
end type ocean_state_type
 
contains
 
!> ocean_model_init initializes the ocean model, including registering fields
!! for restarts and reading restart files if appropriate.
!!
!!   This subroutine initializes both the ocean state and the ocean surface type.
!! Because of the way that indicies and domains are handled, Ocean_sfc must have
!! been used in a previous call to initialize_ocean_type.
subroutine ocean_model_init(Ocean_sfc, OS, Time_init, Time_in, gas_fields_ocn, input_restart_file)
  type(ocean_public_type), target, &
                       intent(inout) :: ocean_sfc !< A structure containing various publicly
                                !! visible ocean surface properties after initialization,
                                !! the data in this type is intent out.
  type(ocean_state_type), pointer    :: os        !< A structure whose internal
                                !! contents are private to ocean_model_mod that may be used to
                                !! contain all information about the ocean's interior state.
  type(time_type),     intent(in)    :: time_init !< The start time for the coupled model's calendar
  type(time_type),     intent(in)    :: time_in   !< The time at which to initialize the ocean model.
  type(coupler_1d_bc_type), &
             optional, intent(in)    :: gas_fields_ocn !< If present, this type describes the
                                              !! ocean and surface-ice fields that will participate
                                              !! in the calculation of additional gas or other
                                              !! tracer fluxes, and can be used to spawn related
                                              !! internal variables in the ice model.
  character(len=*), optional, intent(in) :: input_restart_file !< If present, name of restart file to read
  ! Local variables
  real :: rho0        ! The Boussinesq ocean density, in kg m-3.
  real :: g_earth     ! The gravitational acceleration in m s-2.
  real :: hfrz        !< If HFrz > 0 (m), melt potential will be computed.
                      !! The actual depth over which melt potential is computed will
                      !! min(HFrz, OBLD), where OBLD is the boundary layer depth.
                      !! If HFrz <= 0 (default), melt potential will not be computed.
  logical :: use_melt_pot!< If true, allocate melt_potential array
 
! This include declares and sets the variable "version".
#include "version_variable.h"
  character(len=40)  :: mdl = "ocean_model_init"  ! This module's name.
  character(len=48)  :: stagger
  integer :: secs, days
  type(param_file_type) :: param_file !< A structure to parse for run-time parameters
  logical :: use_temperature
 
  call calltree_enter("ocean_model_init(), MOM_ocean_model_mct.F90")
  if (associated(os)) then
    call mom_error(warning, "ocean_model_init called with an associated "// &
                    "ocean_state_type structure. Model is already initialized.")
    return
  endif
  allocate(os)
 
  os%is_ocean_pe = ocean_sfc%is_ocean_pe
  if (.not.os%is_ocean_pe) return
 
  os%Time = time_in
  call initialize_mom(os%Time, time_init, param_file, os%dirs, os%MOM_CSp, &
                      os%restart_CSp, time_in, offline_tracer_mode=os%offline_tracer_mode, &
                      input_restart_file=input_restart_file, &
                      diag_ptr=os%diag, count_calls=.true.)
  call get_mom_state_elements(os%MOM_CSp, g=os%grid, gv=os%GV, us=os%US, c_p=os%C_p, &
                              use_temp=use_temperature)
  os%fluxes%C_p = os%C_p
 
  ! Read all relevant parameters and write them to the model log.
  call log_version(param_file, mdl, version, "")
 
  call get_param(param_file, mdl, "SINGLE_STEPPING_CALL", os%single_step_call, &
                 "If true, advance the state of MOM with a single step "//&
                 "including both dynamics and thermodynamics.  If false, "//&
                 "the two phases are advanced with separate calls.", default=.true.)
  call get_param(param_file, mdl, "DT", os%dt, &
                 "The (baroclinic) dynamics time step.  The time-step that "//&
                 "is actually used will be an integer fraction of the "//&
                 "forcing time-step.", units="s", fail_if_missing=.true.)
  call get_param(param_file, mdl, "DT_THERM", os%dt_therm, &
                 "The thermodynamic and tracer advection time step. "//&
                 "Ideally DT_THERM should be an integer multiple of DT "//&
                 "and less than the forcing or coupling time-step, unless "//&
                 "THERMO_SPANS_COUPLING is true, in which case DT_THERM "//&
                 "can be an integer multiple of the coupling timestep.  By "//&
                 "default DT_THERM is set to DT.", units="s", default=os%dt)
  call get_param(param_file, "MOM", "THERMO_SPANS_COUPLING", os%thermo_spans_coupling, &
                 "If true, the MOM will take thermodynamic and tracer "//&
                 "timesteps that can be longer than the coupling timestep. "//&
                 "The actual thermodynamic timestep that is used in this "//&
                 "case is the largest integer multiple of the coupling "//&
                 "timestep that is less than or equal to DT_THERM.", default=.false.)
  call get_param(param_file, mdl, "DIABATIC_FIRST", os%diabatic_first, &
                 "If true, apply diabatic and thermodynamic processes, "//&
                 "including buoyancy forcing and mass gain or loss, "//&
                 "before stepping the dynamics forward.", default=.false.)
 
  call get_param(param_file, mdl, "RESTART_CONTROL", os%Restart_control, &
                 "An integer whose bits encode which restart files are "//&
                 "written. Add 2 (bit 1) for a time-stamped file, and odd "//&
                 "(bit 0) for a non-time-stamped file.  A restart file "//&
                 "will be saved at the end of the run segment for any "//&
                 "non-negative value.", default=1)
  call get_param(param_file, mdl, "OCEAN_SURFACE_STAGGER", stagger, &
                 "A case-insensitive character string to indicate the "//&
                 "staggering of the surface velocity field that is "//&
                 "returned to the coupler.  Valid values include "//&
                 "'A', 'B', or 'C'.", default="C")
  if (uppercase(stagger(1:1)) == 'A') then ; ocean_sfc%stagger = agrid
  elseif (uppercase(stagger(1:1)) == 'B') then ; ocean_sfc%stagger = bgrid_ne
  elseif (uppercase(stagger(1:1)) == 'C') then ; ocean_sfc%stagger = cgrid_ne
  else ; call mom_error(fatal,"ocean_model_init: OCEAN_SURFACE_STAGGER = "// &
                        trim(stagger)//" is invalid.") ; endif
 
  call get_param(param_file, mdl, "RESTORE_SALINITY",os%restore_salinity, &
                 "If true, the coupled driver will add a globally-balanced "//&
                 "fresh-water flux that drives sea-surface salinity "//&
                 "toward specified values.", default=.false.)
  call get_param(param_file, mdl, "RESTORE_TEMPERATURE",os%restore_temp, &
                 "If true, the coupled driver will add a "//&
                 "heat flux that drives sea-surface temperature "//&
                 "toward specified values.", default=.false.)
  call get_param(param_file, mdl, "RHO_0", rho0, &
                 "The mean ocean density used with BOUSSINESQ true to "//&
                 "calculate accelerations and the mass for conservation "//&
                 "properties, or with BOUSSINSEQ false to convert some "//&
                 "parameters from vertical units of m to kg m-2.", &
                 units="kg m-3", default=1035.0)
  call get_param(param_file, mdl, "G_EARTH", g_earth, &
                 "The gravitational acceleration of the Earth.", &
                 units="m s-2", default = 9.80)
 
  call get_param(param_file, mdl, "ICE_SHELF",  os%use_ice_shelf, &
                 "If true, enables the ice shelf model.", default=.false.)
 
  call get_param(param_file, mdl, "ICEBERGS_APPLY_RIGID_BOUNDARY",  os%icebergs_alter_ocean, &
                 "If true, allows icebergs to change boundary condition felt by ocean", default=.false.)
 
  os%press_to_z = 1.0/(rho0*g_earth)
 
  call get_param(param_file, mdl, "HFREEZE", hfrz, &
                 "If HFREEZE > 0, melt potential will be computed. The actual depth "//&
                 "over which melt potential is computed will be min(HFREEZE, OBLD), "//&
                 "where OBLD is the boundary layer depth. If HFREEZE <= 0 (default), "//&
                 "melt potential will not be computed.", units="m", default=-1.0, do_not_log=.true.)
 
  if (hfrz .gt. 0.0) then
    use_melt_pot=.true.
  else
    use_melt_pot=.false.
  endif
 
  !   Consider using a run-time flag to determine whether to do the diagnostic
  ! vertical integrals, since the related 3-d sums are not negligible in cost.
  call allocate_surface_state(os%sfc_state, os%grid, use_temperature, &
                              do_integrals=.true., gas_fields_ocn=gas_fields_ocn, use_meltpot=use_melt_pot)
 
  call surface_forcing_init(time_in, os%grid, os%US, param_file, os%diag, &
                            os%forcing_CSp, os%restore_salinity, os%restore_temp)
 
  if (os%use_ice_shelf)  then
    call initialize_ice_shelf(param_file, os%grid, os%Time, os%ice_shelf_CSp, &
                              os%diag, os%forces, os%fluxes)
  endif
 
  if (os%icebergs_alter_ocean)  then
    call marine_ice_init(os%Time, os%grid, param_file, os%diag, os%marine_ice_CSp)
    if (.not. os%use_ice_shelf) &
      call allocate_forcing_type(os%grid, os%fluxes, shelf=.true.)
  endif
 
  call get_param(param_file, mdl, "USE_WAVES", os%Use_Waves, &
       "If true, enables surface wave modules.", default=.false.)
  if (os%use_waves) then
    call mom_wave_interface_init(os%Time, os%grid, os%GV, os%US, param_file, os%Waves, os%diag)
  else
    call mom_wave_interface_init_lite(param_file)
  endif
 
  if (associated(os%grid%Domain%maskmap)) then
    call initialize_ocean_public_type(os%grid%Domain%mpp_domain, ocean_sfc, &
                                      os%diag, maskmap=os%grid%Domain%maskmap, &
                                      gas_fields_ocn=gas_fields_ocn)
  else
    call initialize_ocean_public_type(os%grid%Domain%mpp_domain, ocean_sfc, &
                                      os%diag, gas_fields_ocn=gas_fields_ocn)
  endif
 
  ! This call can only occur here if the coupler_bc_type variables have been
  ! initialized already using the information from gas_fields_ocn.
  if (present(gas_fields_ocn)) then
    call coupler_type_set_diags(ocean_sfc%fields, "ocean_sfc", &
                                ocean_sfc%axes(1:2), time_in)
 
    call extract_surface_state(os%MOM_CSp, os%sfc_state)
 
    call convert_state_to_ocean_type(os%sfc_state, ocean_sfc, os%grid, os%US)
  endif
 
  call close_param_file(param_file)
  call diag_mediator_close_registration(os%diag)
 
  if (is_root_pe()) &
    write(*,'(/12x,a/)') '======== COMPLETED MOM INITIALIZATION ========'
 
  call calltree_leave("ocean_model_init(")
end subroutine ocean_model_init
 
!> update_ocean_model uses the forcing in Ice_ocean_boundary to advance the
!! ocean model's state from the input value of Ocean_state (which must be for
!! time time_start_update) for a time interval of Ocean_coupling_time_step,
!! returning the publicly visible ocean surface properties in Ocean_sfc and
!! storing the new ocean properties in Ocean_state.
subroutine update_ocean_model(Ice_ocean_boundary, OS, Ocean_sfc, &
                              time_start_update, Ocean_coupling_time_step, &
                              update_dyn, update_thermo, Ocn_fluxes_used)
  type(ice_ocean_boundary_type), &
                     intent(in)    :: ice_ocean_boundary !< A structure containing the
                                              !! various forcing fields coming from the ice.
  type(ocean_state_type), &
                     pointer       :: os      !< A pointer to a private structure containing
                                              !! the internal ocean state.
  type(ocean_public_type), &
                     intent(inout) :: ocean_sfc !< A structure containing all the
                                              !! publicly visible ocean surface fields after
                                              !! a coupling time step.  The data in this type is
                                              !! intent out.
  type(time_type),   intent(in)    :: time_start_update  !< The time at the beginning of the update step.
  type(time_type),   intent(in)    :: ocean_coupling_time_step !< The amount of time over
                                              !! which to advance the ocean.
  logical, optional, intent(in)    :: update_dyn !< If present and false, do not do updates
                                              !! due to the ocean dynamics.
  logical, optional, intent(in)    :: update_thermo !< If present and false, do not do updates
                                              !! due to the ocean thermodynamics or remapping.
  logical, optional, intent(in)    :: ocn_fluxes_used !< If present, this indicates whether the
                                              !! cumulative thermodynamic fluxes from the ocean,
                                              !! like frazil, have been used and should be reset.
  ! Local variables
  type(time_type) :: master_time ! This allows step_MOM to temporarily change
                                 ! the time that is seen by internal modules.
  type(time_type) :: time1       ! The value of the ocean model's time at the
                                 ! start of a call to step_MOM.
  integer :: index_bnds(4)       ! The computational domain index bounds in the
                                 ! ice-ocean boundary type.
  real :: weight          ! Flux accumulation weight
  real :: dt_coupling     ! The coupling time step in seconds.
  integer :: nts          ! The number of baroclinic dynamics time steps
                          ! within dt_coupling.
  real :: dt_therm        ! A limited and quantized version of OS%dt_therm (sec)
  real :: dt_dyn          ! The dynamics time step in sec.
  real :: dtdia           ! The diabatic time step in sec.
  real :: t_elapsed_seg   ! The elapsed time in this update segment, in s.
  integer :: n, n_max, n_last_thermo
  type(time_type) :: time2  ! A temporary time.
  logical :: thermo_does_span_coupling ! If true, thermodynamic forcing spans
                                       ! multiple dynamic timesteps.
  logical :: do_dyn       ! If true, step the ocean dynamics and transport.
  logical :: do_thermo    ! If true, step the ocean thermodynamics.
  logical :: step_thermo           ! If true, take a thermodynamic step.
  integer :: secs, days
  integer :: is, ie, js, je
 
  call calltree_enter("update_ocean_model(), MOM_ocean_model_mct.F90")
  call get_time(ocean_coupling_time_step, secs, days)
  dt_coupling = 86400.0*real(days) + real(secs)
 
  if (time_start_update /= os%Time) then
    call mom_error(warning, "update_ocean_model: internal clock does not "//&
                            "agree with time_start_update argument.")
  endif
 
  if (.not.associated(os)) then
    call mom_error(fatal, "update_ocean_model called with an unassociated "// &
                    "ocean_state_type structure. ocean_model_init must be "//  &
                    "called first to allocate this structure.")
    return
  endif
 
  do_dyn = .true. ; if (present(update_dyn)) do_dyn = update_dyn
  do_thermo = .true. ; if (present(update_thermo)) do_thermo = update_thermo
 
  ! This is benign but not necessary if ocean_model_init_sfc was called or if
  ! OS%sfc_state%tr_fields was spawned in ocean_model_init.  Consider removing it.
  is = os%grid%isc ; ie = os%grid%iec ; js = os%grid%jsc ; je = os%grid%jec
  call coupler_type_spawn(ocean_sfc%fields, os%sfc_state%tr_fields, &
                          (/is,is,ie,ie/), (/js,js,je,je/), as_needed=.true.)
 
  ! Translate Ice_ocean_boundary into fluxes.
  call mpp_get_compute_domain(ocean_sfc%Domain, index_bnds(1), index_bnds(2), &
                              index_bnds(3), index_bnds(4))
  weight = 1.0
 
  call convert_iob_to_forces(ice_ocean_boundary, os%forces, index_bnds, os%Time, &
                             os%grid, os%US, os%forcing_CSp)
 
  if (os%fluxes%fluxes_used) then
 
    ! GMM, is enable_averaging needed now?
    call enable_averaging(dt_coupling, os%Time + ocean_coupling_time_step, os%diag)
 
    if (do_thermo) &
      call convert_iob_to_fluxes(ice_ocean_boundary, os%fluxes, index_bnds, os%Time, dt_coupling, &
                               os%grid, os%US, os%forcing_CSp, os%sfc_state, &
                               os%restore_salinity, os%restore_temp)
 
    ! Add ice shelf fluxes
    if (os%use_ice_shelf) then
      if (do_thermo) &
        call shelf_calc_flux(os%sfc_state, os%fluxes, os%Time, dt_coupling, os%Ice_shelf_CSp)
      if (do_dyn) &
        call add_shelf_forces(os%grid, os%US, os%Ice_shelf_CSp, os%forces)
    endif
    if (os%icebergs_alter_ocean)  then
      if (do_dyn) &
        call iceberg_forces(os%grid, os%forces, os%use_ice_shelf, &
                            os%sfc_state, dt_coupling, os%marine_ice_CSp)
      if (do_thermo) &
        call iceberg_fluxes(os%grid, os%US, os%fluxes, os%use_ice_shelf, &
                          os%sfc_state, dt_coupling, os%marine_ice_CSp)
    endif
 
    ! Fields that exist in both the forcing and mech_forcing types must be copied.
    call copy_common_forcing_fields(os%forces, os%fluxes, os%grid)
 
#ifdef _USE_GENERIC_TRACER
    call enable_averaging(dt_coupling, os%Time + ocean_coupling_time_step, os%diag) !Is this needed?
    call mom_generic_tracer_fluxes_accumulate(os%fluxes, weight) !here weight=1, just saving the current fluxes
#endif
 
  else
 
    os%flux_tmp%C_p = os%fluxes%C_p
 
    if (do_thermo) &
      call convert_iob_to_fluxes(ice_ocean_boundary, os%flux_tmp, index_bnds, os%Time, dt_coupling, &
                               os%grid, os%US, os%forcing_CSp, os%sfc_state, os%restore_salinity,os%restore_temp)
 
    if (os%use_ice_shelf) then
      if (do_thermo) &
        call shelf_calc_flux(os%sfc_state, os%flux_tmp, os%Time, dt_coupling, os%Ice_shelf_CSp)
      if (do_dyn) &
        call add_shelf_forces(os%grid, os%US, os%Ice_shelf_CSp, os%forces)
    endif
    if (os%icebergs_alter_ocean)  then
      if (do_dyn) &
        call iceberg_forces(os%grid, os%forces, os%use_ice_shelf, &
                            os%sfc_state, dt_coupling, os%marine_ice_CSp)
      if (do_thermo) &
        call iceberg_fluxes(os%grid, os%US, os%flux_tmp, os%use_ice_shelf, &
                          os%sfc_state, dt_coupling, os%marine_ice_CSp)
    endif
 
    call forcing_accumulate(os%flux_tmp, os%forces, os%fluxes, os%grid, weight)
 
    ! Some of the fields that exist in both the forcing and mech_forcing types
    ! (e.g., ustar) are time-averages must be copied back to the forces type.
    call copy_back_forcing_fields(os%fluxes, os%forces, os%grid)
 
#ifdef _USE_GENERIC_TRACER
    call mom_generic_tracer_fluxes_accumulate(os%flux_tmp, weight) !weight of the current flux in the running average
#endif
  endif
 
  call set_derived_forcing_fields(os%forces, os%fluxes, os%grid, os%US, os%GV%Rho0)
  call set_net_mass_forcing(os%fluxes, os%forces, os%grid, os%US)
 
  if (os%use_waves) then
    call update_surface_waves(os%grid, os%GV, os%US, os%time, ocean_coupling_time_step, os%waves)
  endif
 
  if (os%nstep==0) then
    call finish_mom_initialization(os%Time, os%dirs, os%MOM_CSp, os%restart_CSp)
  endif
 
  call disable_averaging(os%diag)
  master_time = os%Time ; time1 = os%Time
 
  if(os%offline_tracer_mode) then
    call step_offline(os%forces, os%fluxes, os%sfc_state, time1, dt_coupling, os%MOM_CSp)
 
  elseif ((.not.do_thermo) .or. (.not.do_dyn)) then
    ! The call sequence is being orchestrated from outside of update_ocean_model.
    call step_mom(os%forces, os%fluxes, os%sfc_state, time1, dt_coupling, os%MOM_CSp, &
                  waves=os%Waves, do_dynamics=do_thermo, do_thermodynamics=do_dyn, &
                  reset_therm=ocn_fluxes_used)
 
  elseif (os%single_step_call) then
    call step_mom(os%forces, os%fluxes, os%sfc_state, time1, dt_coupling, os%MOM_CSp, waves=os%Waves)
 
  else
    n_max = 1 ; if (dt_coupling > os%dt) n_max = ceiling(dt_coupling/os%dt - 0.001)
    dt_dyn = dt_coupling / real(n_max)
    thermo_does_span_coupling = (os%thermo_spans_coupling .and. &
                                (os%dt_therm > 1.5*dt_coupling))
 
    if (thermo_does_span_coupling) then
      dt_therm = dt_coupling * floor(os%dt_therm / dt_coupling + 0.001)
      nts = floor(dt_therm/dt_dyn + 0.001)
    else
      nts = max(1,min(n_max,floor(os%dt_therm/dt_dyn + 0.001)))
      n_last_thermo = 0
    endif
 
    time2 = time1 ; t_elapsed_seg = 0.0
    do n=1,n_max
      if (os%diabatic_first) then
        if (thermo_does_span_coupling) call mom_error(fatal, &
            "MOM is not yet set up to have restarts that work with "//&
            "THERMO_SPANS_COUPLING and DIABATIC_FIRST.")
        if (modulo(n-1,nts)==0) then
          dtdia = dt_dyn*min(nts,n_max-(n-1))
          call step_mom(os%forces, os%fluxes, os%sfc_state, time2, dtdia, os%MOM_CSp, &
                        waves=os%Waves, do_dynamics=.false., do_thermodynamics=.true., &
                        start_cycle=(n==1), end_cycle=.false., cycle_length=dt_coupling)
        endif
 
        call step_mom(os%forces, os%fluxes, os%sfc_state, time2, dt_dyn, os%MOM_CSp, &
                      waves=os%Waves, do_dynamics=.true., do_thermodynamics=.false., &
                      start_cycle=.false., end_cycle=(n==n_max), cycle_length=dt_coupling)
      else
        call step_mom(os%forces, os%fluxes, os%sfc_state, time2, dt_dyn, os%MOM_CSp, &
                      waves=os%Waves, do_dynamics=.true., do_thermodynamics=.false., &
                      start_cycle=(n==1), end_cycle=.false., cycle_length=dt_coupling)
 
        step_thermo = .false.
        if (thermo_does_span_coupling) then
          dtdia = dt_therm
          step_thermo = mom_state_is_synchronized(os%MOM_CSp, adv_dyn=.true.)
        elseif ((modulo(n,nts)==0) .or. (n==n_max)) then
          dtdia = dt_dyn*(n - n_last_thermo)
          n_last_thermo = n
          step_thermo = .true.
        endif
 
        if (step_thermo) then
          ! Back up Time2 to the start of the thermodynamic segment.
          time2 = time2 - set_time(int(floor((dtdia - dt_dyn) + 0.5)))
          call step_mom(os%forces, os%fluxes, os%sfc_state, time2, dtdia, os%MOM_CSp, &
                        waves=os%Waves, do_dynamics=.false., do_thermodynamics=.true., &
                        start_cycle=.false., end_cycle=(n==n_max), cycle_length=dt_coupling)
        endif
      endif
 
      t_elapsed_seg = t_elapsed_seg + dt_dyn
      time2 = time1 + set_time(int(floor(t_elapsed_seg + 0.5)))
    enddo
  endif
 
  os%Time = master_time + ocean_coupling_time_step
  os%nstep = os%nstep + 1
 
  call mech_forcing_diags(os%forces, dt_coupling, os%grid, os%Time, os%diag, os%forcing_CSp%handles)
 
  if (os%fluxes%fluxes_used) then
    call forcing_diagnostics(os%fluxes, os%sfc_state, os%grid, os%US, os%Time, os%diag, os%forcing_CSp%handles)
  endif
 
! Translate state into Ocean.
!  call convert_state_to_ocean_type(OS%sfc_state, Ocean_sfc, OS%grid, &
!                                   Ice_ocean_boundary%p, OS%press_to_z)
  call convert_state_to_ocean_type(os%sfc_state, ocean_sfc, os%grid, os%US)
  call coupler_type_send_data(ocean_sfc%fields, os%Time)
 
  call calltree_leave("update_ocean_model()")
end subroutine update_ocean_model
 
!> This subroutine writes out the ocean model restart file.
subroutine ocean_model_restart(OS, timestamp, restartname)
  type(ocean_state_type),     pointer    :: os !< A pointer to the structure containing the
                                               !! internal ocean state being saved to a restart file
  character(len=*), optional, intent(in) :: timestamp !< An optional timestamp string that should be
                                               !! prepended to the file name. (Currently this is unused.)
  character(len=*), optional, intent(in) :: restartname !< Name of restart file to use
                                               !! This option distinguishes the cesm interface from the
                                               !! non-cesm interface
 
  if (.not.mom_state_is_synchronized(os%MOM_CSp)) &
      call mom_error(warning, "End of MOM_main reached with inconsistent "//&
         "dynamics and advective times.  Additional restart fields "//&
         "that have not been coded yet would be required for reproducibility.")
  if (.not.os%fluxes%fluxes_used) call mom_error(fatal, "ocean_model_restart "//&
      "was called with unused buoyancy fluxes.  For conservation, the ocean "//&
      "restart files can only be created after the buoyancy forcing is applied.")
 
  if (present(restartname)) then
     call save_restart(os%dirs%restart_output_dir, os%Time, os%grid, &
          os%restart_CSp, gv=os%GV, filename=restartname)
     call forcing_save_restart(os%forcing_CSp, os%grid, os%Time, &
          os%dirs%restart_output_dir) ! Is this needed?
     if (os%use_ice_shelf) then
        call ice_shelf_save_restart(os%Ice_shelf_CSp, os%Time, &
             os%dirs%restart_output_dir)
     endif
  else
     if (btest(os%Restart_control,1)) then
        call save_restart(os%dirs%restart_output_dir, os%Time, os%grid, &
             os%restart_CSp, .true., gv=os%GV)
        call forcing_save_restart(os%forcing_CSp, os%grid, os%Time, &
             os%dirs%restart_output_dir, .true.)
        if (os%use_ice_shelf) then
           call ice_shelf_save_restart(os%Ice_shelf_CSp, os%Time, os%dirs%restart_output_dir, .true.)
        endif
     endif
     if (btest(os%Restart_control,0)) then
        call save_restart(os%dirs%restart_output_dir, os%Time, os%grid, &
             os%restart_CSp, gv=os%GV)
        call forcing_save_restart(os%forcing_CSp, os%grid, os%Time, &
             os%dirs%restart_output_dir)
        if (os%use_ice_shelf) then
           call ice_shelf_save_restart(os%Ice_shelf_CSp, os%Time, os%dirs%restart_output_dir)
        endif
     endif
  end if
 
end subroutine ocean_model_restart
! </SUBROUTINE> NAME="ocean_model_restart"
 
!> ocean_model_end terminates the model run, saving the ocean state in a restart
!! and deallocating any data associated with the ocean.
subroutine ocean_model_end(Ocean_sfc, Ocean_state, Time)
  type(ocean_public_type), intent(inout) :: ocean_sfc   !< An ocean_public_type structure that is
                                                        !! to be deallocated upon termination.
  type(ocean_state_type),  pointer       :: ocean_state !< A pointer to the structure containing
                                                        !! the internal ocean state to be deallocated
                                                        !! upon termination.
  type(time_type),         intent(in)    :: time        !< The model time, used for writing restarts.
 
  call ocean_model_save_restart(ocean_state, time)
  call diag_mediator_end(time, ocean_state%diag, end_diag_manager=.true.)
  ! print time stats
  call mom_infra_end
  call mom_end(ocean_state%MOM_CSp)
  if (ocean_state%use_ice_shelf) call ice_shelf_end(ocean_state%Ice_shelf_CSp)
end subroutine ocean_model_end
 
!> ocean_model_save_restart causes restart files associated with the ocean to be
!! written out.
subroutine ocean_model_save_restart(OS, Time, directory, filename_suffix)
  type(ocean_state_type),     pointer    :: os  !< A pointer to the structure containing the
                                                !! internal ocean state (in).
  type(time_type),            intent(in) :: time !< The model time at this call, needed for mpp_write calls.
  character(len=*), optional, intent(in) :: directory  !<  An optional directory into which to
                                                !! write these restart files.
  character(len=*), optional, intent(in) :: filename_suffix !< An optional suffix (e.g., a time-stamp)
                                                !! to append to the restart file names.
! Note: This is a new routine - it will need to exist for the new incremental
!   checkpointing.  It will also be called by ocean_model_end, giving the same
!   restart behavior as now in FMS.
  character(len=200) :: restart_dir
 
  if (.not.mom_state_is_synchronized(os%MOM_CSp)) &
    call mom_error(warning, "ocean_model_save_restart called with inconsistent "//&
         "dynamics and advective times.  Additional restart fields "//&
         "that have not been coded yet would be required for reproducibility.")
  if (.not.os%fluxes%fluxes_used) call mom_error(fatal, "ocean_model_save_restart "//&
       "was called with unused buoyancy fluxes.  For conservation, the ocean "//&
       "restart files can only be created after the buoyancy forcing is applied.")
 
  if (present(directory)) then ; restart_dir = directory
  else ; restart_dir = os%dirs%restart_output_dir ; endif
 
  call save_restart(restart_dir, time, os%grid, os%restart_CSp, gv=os%GV)
 
  call forcing_save_restart(os%forcing_CSp, os%grid, time, restart_dir)
 
  if (os%use_ice_shelf) then
    call ice_shelf_save_restart(os%Ice_shelf_CSp, os%Time, os%dirs%restart_output_dir)
  endif
 
end subroutine ocean_model_save_restart
 
!> Initialize the public ocean type
subroutine initialize_ocean_public_type(input_domain, Ocean_sfc, diag, maskmap, &
                                        gas_fields_ocn)
  type(domain2d),          intent(in)    :: input_domain !< The ocean model domain description
  type(ocean_public_type), intent(inout) :: Ocean_sfc !< A structure containing various publicly
                                !! visible ocean surface properties after initialization, whose
                                !! elements are allocated here.
  type(diag_ctrl),         intent(in)    :: diag  !< A structure that regulates diagnsotic output
  logical, dimension(:,:), &
                 optional, intent(in)    :: maskmap !< A mask indicating which virtual processors
                                              !! are actually in use.  If missing, all are used.
  type(coupler_1d_bc_type), &
                 optional, intent(in)    :: gas_fields_ocn !< If present, this type describes the
                                              !! ocean and surface-ice fields that will participate
                                              !! in the calculation of additional gas or other
                                              !! tracer fluxes.
  integer :: xsz, ysz, layout(2)
  ! ice-ocean-boundary fields are always allocated using absolute indicies
  ! and have no halos.
  integer :: isc, iec, jsc, jec
 
  call mpp_get_layout(input_domain,layout)
  call mpp_get_global_domain(input_domain, xsize=xsz, ysize=ysz)
  if(PRESENT(maskmap)) then
    call mpp_define_domains((/1,xsz,1,ysz/),layout,ocean_sfc%Domain, maskmap=maskmap)
  else
    call mpp_define_domains((/1,xsz,1,ysz/),layout,ocean_sfc%Domain)
  endif
  call mpp_get_compute_domain(ocean_sfc%Domain, isc, iec, jsc, jec)
 
  allocate (ocean_sfc%t_surf (isc:iec,jsc:jec), &
            ocean_sfc%s_surf (isc:iec,jsc:jec), &
            ocean_sfc%u_surf (isc:iec,jsc:jec), &
            ocean_sfc%v_surf (isc:iec,jsc:jec), &
            ocean_sfc%sea_lev(isc:iec,jsc:jec), &
            ocean_sfc%area   (isc:iec,jsc:jec), &
            ocean_sfc%OBLD   (isc:iec,jsc:jec), &
            ocean_sfc%melt_potential(isc:iec,jsc:jec), &
            ocean_sfc%frazil (isc:iec,jsc:jec))
 
  ocean_sfc%t_surf  = 0.0  ! time averaged sst (Kelvin) passed to atmosphere/ice model
  ocean_sfc%s_surf  = 0.0  ! time averaged sss (psu) passed to atmosphere/ice models
  ocean_sfc%u_surf  = 0.0  ! time averaged u-current (m/sec) passed to atmosphere/ice models
  ocean_sfc%v_surf  = 0.0  ! time averaged v-current (m/sec)  passed to atmosphere/ice models
  ocean_sfc%sea_lev = 0.0  ! time averaged thickness of top model grid cell (m) plus patm/rho0/grav
  ocean_sfc%frazil  = 0.0  ! time accumulated frazil (J/m^2) passed to ice model
  ocean_sfc%melt_potential  = 0.0  ! time accumulated melt potential (J/m^2) passed to ice model
  ocean_sfc%OBLD    = 0.0  ! ocean boundary layer depth, in m
  ocean_sfc%area    = 0.0
  ocean_sfc%axes    = diag%axesT1%handles !diag axes to be used by coupler tracer flux diagnostics
 
  if (present(gas_fields_ocn)) then
    call coupler_type_spawn(gas_fields_ocn, ocean_sfc%fields, (/isc,isc,iec,iec/), &
                              (/jsc,jsc,jec,jec/), suffix = '_ocn', as_needed=.true.)
  endif
 
end subroutine initialize_ocean_public_type
 
!> This subroutine translates the coupler's ocean_data_type into MOM's
!! surface state variable.  This may eventually be folded into the MOM
!! code that calculates the surface state in the first place.
!! Note the offset in the arrays because the ocean_data_type has no
!! halo points in its arrays and always uses absolute indicies.
subroutine convert_state_to_ocean_type(sfc_state, Ocean_sfc, G, US, patm, press_to_z)
  type(surface),         intent(inout) :: sfc_state !< A structure containing fields that
                                               !! describe the surface state of the ocean.
  type(ocean_public_type), &
                 target, intent(inout) :: Ocean_sfc !< A structure containing various publicly
                                               !! visible ocean surface fields, whose elements
                                               !! have their data set here.
  type(ocean_grid_type), intent(inout) :: G    !< The ocean's grid structure
  type(unit_scale_type),   intent(in)  :: US   !< A dimensional unit scaling type
  real,        optional, intent(in)    :: patm(:,:)  !< The pressure at the ocean surface, in Pa.
  real,        optional, intent(in)    :: press_to_z !< A conversion factor between pressure and
                                               !! ocean depth in m, usually 1/(rho_0*g), in m Pa-1.
 
  ! Local variables
  real :: IgR0
  character(len=48)  :: val_str
  integer :: isc_bnd, iec_bnd, jsc_bnd, jec_bnd
  integer :: i, j, i0, j0, is, ie, js, je
 
  is = g%isc ; ie = g%iec ; js = g%jsc ; je = g%jec
  call pass_vector(sfc_state%u,sfc_state%v,g%Domain)
 
  call mpp_get_compute_domain(ocean_sfc%Domain, isc_bnd, iec_bnd, &
                              jsc_bnd, jec_bnd)
  if (present(patm)) then
    ! Check that the inidicies in patm are (isc_bnd:iec_bnd,jsc_bnd:jec_bnd).
    if (.not.present(press_to_z)) call mom_error(fatal, &
        'convert_state_to_ocean_type: press_to_z must be present if patm is.')
  endif
 
  i0 = is - isc_bnd ; j0 = js - jsc_bnd
  if (sfc_state%T_is_conT) then
    ! Convert the surface T from conservative T to potential T.
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%t_surf(i,j) = gsw_pt_from_ct(sfc_state%SSS(i+i0,j+j0), &
                               sfc_state%SST(i+i0,j+j0)) + celsius_kelvin_offset
    enddo ; enddo
  else
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%t_surf(i,j) = sfc_state%SST(i+i0,j+j0) + celsius_kelvin_offset
    enddo ; enddo
  endif
  if (sfc_state%S_is_absS) then
    ! Convert the surface S from absolute salinity to practical salinity.
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%s_surf(i,j) = gsw_sp_from_sr(sfc_state%SSS(i+i0,j+j0))
    enddo ; enddo
  else
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%s_surf(i,j) = sfc_state%SSS(i+i0,j+j0)
    enddo ; enddo
  endif
 
  if (present(patm)) then
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%sea_lev(i,j) = sfc_state%sea_lev(i+i0,j+j0) + patm(i,j) * press_to_z
      ocean_sfc%area(i,j) = us%L_to_m**2*g%areaT(i+i0,j+j0)
    enddo ; enddo
  else
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%sea_lev(i,j) = sfc_state%sea_lev(i+i0,j+j0)
      ocean_sfc%area(i,j) = us%L_to_m**2*g%areaT(i+i0,j+j0)
    enddo ; enddo
  endif
 
  if (associated(sfc_state%frazil)) then
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%frazil(i,j) = sfc_state%frazil(i+i0,j+j0)
    enddo ; enddo
  endif
 
  if (allocated(sfc_state%melt_potential)) then
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%melt_potential(i,j) = sfc_state%melt_potential(i+i0,j+j0)
    enddo ; enddo
  endif
 
  if (allocated(sfc_state%Hml)) then
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%OBLD(i,j) = sfc_state%Hml(i+i0,j+j0)
    enddo ; enddo
  endif
 
  if (ocean_sfc%stagger == agrid) then
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%u_surf(i,j) = g%mask2dT(i+i0,j+j0) * &
                0.5*(sfc_state%u(i+i0,j+j0)+sfc_state%u(i-1+i0,j+j0))
      ocean_sfc%v_surf(i,j) = g%mask2dT(i+i0,j+j0) * &
                0.5*(sfc_state%v(i+i0,j+j0)+sfc_state%v(i+i0,j-1+j0))
    enddo ; enddo
  elseif (ocean_sfc%stagger == bgrid_ne) then
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%u_surf(i,j) = g%mask2dBu(i+i0,j+j0) * &
                0.5*(sfc_state%u(i+i0,j+j0)+sfc_state%u(i+i0,j+j0+1))
      ocean_sfc%v_surf(i,j) = g%mask2dBu(i+i0,j+j0) * &
                0.5*(sfc_state%v(i+i0,j+j0)+sfc_state%v(i+i0+1,j+j0))
    enddo ; enddo
  elseif (ocean_sfc%stagger == cgrid_ne) then
    do j=jsc_bnd,jec_bnd ; do i=isc_bnd,iec_bnd
      ocean_sfc%u_surf(i,j) = g%mask2dCu(i+i0,j+j0)*sfc_state%u(i+i0,j+j0)
      ocean_sfc%v_surf(i,j) = g%mask2dCv(i+i0,j+j0)*sfc_state%v(i+i0,j+j0)
    enddo ; enddo
  else
    write(val_str, '(I8)') ocean_sfc%stagger
    call mom_error(fatal, "convert_state_to_ocean_type: "//&
      "Ocean_sfc%stagger has the unrecognized value of "//trim(val_str))
  endif
 
  if (coupler_type_initialized(sfc_state%tr_fields)) then
    if (.not.coupler_type_initialized(ocean_sfc%fields)) then
      call mom_error(fatal, "convert_state_to_ocean_type: "//&
               "Ocean_sfc%fields has not been initialized.")
    endif
    call coupler_type_copy_data(sfc_state%tr_fields, ocean_sfc%fields)
  endif
 
end subroutine convert_state_to_ocean_type
 
!>   This subroutine extracts the surface properties from the ocean's internal
!! state and stores them in the ocean type returned to the calling ice model.
!! It has to be separate from the ocean_initialization call because the coupler
!! module allocates the space for some of these variables.
subroutine ocean_model_init_sfc(OS, Ocean_sfc)
  type(ocean_state_type),  pointer       :: os  !< The structure with the complete ocean state
  type(ocean_public_type), intent(inout) :: ocean_sfc !< A structure containing various publicly
                                !! visible ocean surface properties after initialization, whose
                                !! elements have their data set here.
  integer :: is, ie, js, je
 
  is = os%grid%isc ; ie = os%grid%iec ; js = os%grid%jsc ; je = os%grid%jec
  call coupler_type_spawn(ocean_sfc%fields, os%sfc_state%tr_fields, &
                          (/is,is,ie,ie/), (/js,js,je,je/), as_needed=.true.)
 
  call extract_surface_state(os%MOM_CSp, os%sfc_state)
 
  call convert_state_to_ocean_type(os%sfc_state, ocean_sfc, os%grid, os%US)
 
end subroutine ocean_model_init_sfc
 
!> ocean_model_flux_init is used to initialize properties of the air-sea fluxes
!! as determined by various run-time parameters.  It can be called from
!! non-ocean PEs, or PEs that have not yet been initialzed, and it can safely
!! be called multiple times.
subroutine ocean_model_flux_init(OS, verbosity)
  type(ocean_state_type), optional, pointer :: os  !< An optional pointer to the ocean state,
                                             !! used to figure out if this is an ocean PE that
                                             !! has already been initialized.
  integer, optional, intent(in) :: verbosity !< A 0-9 integer indicating a level of verbosity.
 
  logical :: os_is_set
  integer :: verbose
 
  os_is_set = .false. ; if (present(os)) os_is_set = associated(os)
 
  ! Use this to control the verbosity of output; consider rethinking this logic later.
  verbose = 5 ; if (os_is_set) verbose = 3
  if (present(verbosity)) verbose = verbosity
 
  call call_tracer_flux_init(verbosity=verbose)
 
end subroutine ocean_model_flux_init
 
!> Ocean_stock_pe - returns the integrated stocks of heat, water, etc. for conservation checks.
!!   Because of the way FMS is coded, only the root PE has the integrated amount,
!!   while all other PEs get 0.
subroutine ocean_stock_pe(OS, index, value, time_index)
  use stock_constants_mod, only : istock_water, istock_heat,istock_salt
  type(ocean_state_type), pointer     :: os         !< A structure containing the internal ocean state.
                                                    !! The data in OS is intent in.
  integer,                intent(in)  :: index      !< The stock index for the quantity of interest.
  real,                   intent(out) :: value      !< Sum returned for the conservation quantity of interest.
  integer,      optional, intent(in)  :: time_index !< An unused optional argument, present only for
                                                    !! interfacial compatibility with other models.
! Arguments: OS - A structure containing the internal ocean state.
!  (in)      index - Index of conservation quantity of interest.
!  (in)      value -  Sum returned for the conservation quantity of interest.
!  (in,opt)  time_index - Index for time level to use if this is necessary.
 
  real :: salt
 
  value = 0.0
  if (.not.associated(os)) return
  if (.not.os%is_ocean_pe) return
 
  select case (index)
    case (istock_water)  ! Return the mass of fresh water in the ocean in kg.
      if (os%GV%Boussinesq) then
        call get_ocean_stocks(os%MOM_CSp, mass=value, on_pe_only=.true.)
      else  ! In non-Boussinesq mode, the mass of salt needs to be subtracted.
        call get_ocean_stocks(os%MOM_CSp, mass=value, salt=salt, on_pe_only=.true.)
        value = value - salt
      endif
    case (istock_heat)  ! Return the heat content of the ocean in J.
      call get_ocean_stocks(os%MOM_CSp, heat=value, on_pe_only=.true.)
    case (istock_salt)  ! Return the mass of the salt in the ocean in kg.
       call get_ocean_stocks(os%MOM_CSp, salt=value, on_pe_only=.true.)
    case default ; value = 0.0
  end select
  ! If the FMS coupler is changed so that Ocean_stock_PE is only called on
  ! ocean PEs, uncomment the following and eliminate the on_PE_only flags above.
  !  if (.not.is_root_pe()) value = 0.0
 
end subroutine ocean_stock_pe
 
!> Write out FMS-format checsums on fields from the ocean surface state
subroutine ocean_public_type_chksum(id, timestep, ocn)
 
  character(len=*),        intent(in) :: id  !< An identifying string for this call
  integer,                 intent(in) :: timestep !< The number of elapsed timesteps
  type(ocean_public_type), intent(in) :: ocn !< A structure containing various publicly
                                             !! visible ocean surface fields.
  integer :: n, m, outunit
 
  outunit = stdout()
 
  write(outunit,*) "BEGIN CHECKSUM(ocean_type):: ", id, timestep
  write(outunit,100) 'ocean%t_surf   ',mpp_chksum(ocn%t_surf )
  write(outunit,100) 'ocean%s_surf   ',mpp_chksum(ocn%s_surf )
  write(outunit,100) 'ocean%u_surf   ',mpp_chksum(ocn%u_surf )
  write(outunit,100) 'ocean%v_surf   ',mpp_chksum(ocn%v_surf )
  write(outunit,100) 'ocean%sea_lev  ',mpp_chksum(ocn%sea_lev)
  write(outunit,100) 'ocean%frazil   ',mpp_chksum(ocn%frazil )
  write(outunit,100) 'ocean%melt_potential  ',mpp_chksum(ocn%melt_potential)
 
  call coupler_type_write_chksums(ocn%fields, outunit, 'ocean%')
100 FORMAT("   CHECKSUM::",a20," = ",z20)
 
end subroutine ocean_public_type_chksum
 
subroutine get_ocean_grid(OS, Gridp)
  ! Obtain the ocean grid.
  type(ocean_state_type) :: os
  type(ocean_grid_type) , pointer :: gridp
 
  gridp => os%grid
  return
end subroutine get_ocean_grid
 
end module mom_ocean_model_mct