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Ice dynamics (mom-ocean#35)
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* In MOM_ice_shelf_dynamics.F90 changes are  made to calc_shelf_visc() and calc_shelf_driving_stress() to account for an irregular quadrilateral grid. In MOM_ice_shelf_initialize.F90 changes are made to initialize_ice_thickness_from_file() to correct masks at initialization.

* Changed indentation

* Changes are made to 'calc_shelf_visc()` to make computations of the velocity derivatives rotation-invariant. Changes in `update_ice_shelf()` utilize G%IareaT(:,:) instead of 1/G%areaT(:,:).
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@OlgaSergienko
OlgaSergienko committed Dec 17, 2021
1 parent bbb9753 commit 50df270
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Showing 2 changed files with 99 additions and 64 deletions.
118 changes: 81 additions & 37 deletions src/ice_shelf/MOM_ice_shelf_dynamics.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -260,9 +260,9 @@ subroutine register_ice_shelf_dyn_restarts(G, param_file, CS, restart_CS)
allocate( CS%v_shelf(IsdB:IedB,JsdB:JedB), source=0.0 )
allocate( CS%t_shelf(isd:ied,jsd:jed), source=-10.0 ) ! [degC]
allocate( CS%ice_visc(isd:ied,jsd:jed), source=0.0 )
allocate( CS%AGlen_visc(isd:ied,jsd:jed), source=2.261e-25 ) ! [Units?]
allocate( CS%AGlen_visc(isd:ied,jsd:jed), source=2.261e-25 ) ! [Pa-3s-1]
allocate( CS%basal_traction(isd:ied,jsd:jed), source=0.0 )
allocate( CS%C_basal_friction(isd:ied,jsd:jed), source=5.0e10 ) ! [Units?]
allocate( CS%C_basal_friction(isd:ied,jsd:jed), source=5.0e10 ) ! [Pa (m-1 s)^n_sliding]
allocate( CS%OD_av(isd:ied,jsd:jed), source=0.0 )
allocate( CS%ground_frac(isd:ied,jsd:jed), source=0.0 )
allocate( CS%taudx_shelf(IsdB:IedB,JsdB:JedB), source=0.0 )
Expand Down Expand Up @@ -553,8 +553,8 @@ subroutine initialize_ice_shelf_dyn(param_file, Time, ISS, CS, G, US, diag, new_
call pass_vector(CS%u_bdry_val, CS%v_bdry_val, G%domain, TO_ALL, BGRID_NE)
call pass_vector(CS%u_face_mask_bdry, CS%v_face_mask_bdry, G%domain, TO_ALL, BGRID_NE)

!initialize ice flow velocities from file
call initialize_ice_flow_from_file(CS%bed_elev,CS%u_shelf, CS%v_shelf,CS%ground_frac, ISS%hmask,ISS%h_shelf, &
!initialize ice flow characteristic (velocities, bed elevation under the grounded part, etc) from file
call initialize_ice_flow_from_file(CS%bed_elev,CS%u_shelf, CS%v_shelf,CS%ground_frac, &
G, US, param_file)
call pass_vector(CS%u_shelf, CS%v_shelf, G%domain, TO_ALL, BGRID_NE)
call pass_var(CS%bed_elev, G%domain,CENTER)
Expand All @@ -567,9 +567,9 @@ subroutine initialize_ice_shelf_dyn(param_file, Time, ISS, CS, G, US, diag, new_
'y-velocity of ice', 'm yr-1', conversion=365.0*86400.0*US%L_T_to_m_s)
! I think that the conversion factors for the next two diagnostics are wrong. - RWH
CS%id_taudx_shelf = register_diag_field('ice_shelf_model','taudx_shelf',CS%diag%axesB1, Time, &
'x-driving stress of ice', 'kPa', conversion=1.e-9*US%RL2_T2_to_Pa)
'x-driving stress of ice', 'kPa', conversion=1.e-3*US%RL2_T2_to_Pa)
CS%id_taudy_shelf = register_diag_field('ice_shelf_model','taudy_shelf',CS%diag%axesB1, Time, &
'y-driving stress of ice', 'kPa', conversion=1.e-9*US%RL2_T2_to_Pa)
'y-driving stress of ice', 'kPa', conversion=1.e-3*US%RL2_T2_to_Pa)
CS%id_u_mask = register_diag_field('ice_shelf_model','u_mask',CS%diag%axesB1, Time, &
'mask for u-nodes', 'none')
CS%id_v_mask = register_diag_field('ice_shelf_model','v_mask',CS%diag%axesB1, Time, &
Expand All @@ -579,9 +579,9 @@ subroutine initialize_ice_shelf_dyn(param_file, Time, ISS, CS, G, US, diag, new_
CS%id_col_thick = register_diag_field('ice_shelf_model','col_thick',CS%diag%axesT1, Time, &
'ocean column thickness passed to ice model', 'm', conversion=US%Z_to_m)
CS%id_visc_shelf = register_diag_field('ice_shelf_model','ice_visc',CS%diag%axesT1, Time, &
'viscosity', 'm', conversion=1e-6*US%Z_to_m)
'vi-viscosity', 'Pa s-1 m', conversion=US%RL2_T2_to_Pa*US%L_T_to_m_s) !vertically integrated viscosity
CS%id_taub = register_diag_field('ice_shelf_model','taub_beta',CS%diag%axesT1, Time, &
'taub', 'Pa yr m-1', conversion=1e-6*US%Z_to_m)
'taub', 'MPa', conversion=1e-6*US%RL2_T2_to_Pa)
CS%id_OD_av = register_diag_field('ice_shelf_model','OD_av',CS%diag%axesT1, Time, &
'intermediate ocean column thickness passed to ice model', 'm', conversion=US%Z_to_m)
endif
Expand Down Expand Up @@ -673,7 +673,10 @@ subroutine update_ice_shelf(CS, ISS, G, US, time_step, Time, ocean_mass, coupled
logical, optional, intent(in) :: coupled_grounding !< If true, the grounding line is
!! determined by coupled ice-ocean dynamics
logical, optional, intent(in) :: must_update_vel !< Always update the ice velocities if true.

real, dimension(SZDIB_(G),SZDJB_(G)) ::taud_x,taud_y !<area-averaged driving stress [R L2T-2 ~> Pa]
real, dimension(SZDI_(G),SZDJ_(G)) :: ice_visc ! <area-averaged vertically integrated ice viscosity
!![R2 L2T-3 ~> Pa s-1 m]
real, dimension(SZDI_(G),SZDJ_(G)) :: basal_tr ! <area-averaged basal traction [R L2T-2 ~> Pa]
integer :: iters
logical :: update_ice_vel, coupled_GL

Expand Down Expand Up @@ -706,12 +709,24 @@ subroutine update_ice_shelf(CS, ISS, G, US, time_step, Time, ocean_mass, coupled
if (CS%id_u_shelf > 0) call post_data(CS%id_u_shelf, CS%u_shelf, CS%diag)
if (CS%id_v_shelf > 0) call post_data(CS%id_v_shelf, CS%v_shelf, CS%diag)
! if (CS%id_t_shelf > 0) call post_data(CS%id_t_shelf,CS%t_shelf,CS%diag)
if (CS%id_taudx_shelf > 0) call post_data(CS%id_taudx_shelf, CS%taudx_shelf, CS%diag)
if (CS%id_taudy_shelf > 0) call post_data(CS%id_taudy_shelf, CS%taudy_shelf, CS%diag)
if (CS%id_taudx_shelf > 0) then
taud_x(:,:) = CS%taudx_shelf(:,:)*G%IareaT(:,:)
call post_data(CS%id_taudx_shelf,taud_x , CS%diag)
endif
if (CS%id_taudy_shelf > 0) then
taud_y(:,:) = CS%taudy_shelf(:,:)*G%IareaT(:,:)
call post_data(CS%id_taudy_shelf,taud_y , CS%diag)
endif
if (CS%id_ground_frac > 0) call post_data(CS%id_ground_frac, CS%ground_frac,CS%diag)
if (CS%id_OD_av >0) call post_data(CS%id_OD_av, CS%OD_av,CS%diag)
if (CS%id_visc_shelf > 0) call post_data(CS%id_visc_shelf, CS%ice_visc,CS%diag)
if (CS%id_taub > 0) call post_data(CS%id_taub, CS%basal_traction,CS%diag)
if (CS%id_visc_shelf > 0) then
ice_visc(:,:)=CS%ice_visc(:,:)*G%IareaT(:,:)
call post_data(CS%id_visc_shelf, ice_visc,CS%diag)
endif
if (CS%id_taub > 0) then
basal_tr(:,:) = CS%basal_traction(:,:)*G%IareaT(:,:)
call post_data(CS%id_taub, basal_tr,CS%diag)
endif
!!
if (CS%id_u_mask > 0) call post_data(CS%id_u_mask,CS%umask,CS%diag)
if (CS%id_v_mask > 0) call post_data(CS%id_v_mask,CS%vmask,CS%diag)
Expand Down Expand Up @@ -874,6 +889,7 @@ subroutine ice_shelf_solve_outer(CS, ISS, G, US, u_shlf, v_shlf, taudx, taudy, i
if (rhoi_rhow * ISS%h_shelf(i,j) - CS%bed_elev(i,j) > 0) then
float_cond(i,j) = 1.0
CS%ground_frac(i,j) = 1.0
CS%OD_av(i,j) =0.0
endif
enddo
enddo
Expand Down Expand Up @@ -960,7 +976,7 @@ subroutine ice_shelf_solve_outer(CS, ISS, G, US, u_shlf, v_shlf, taudx, taudy, i

!! begin loop

do iter=1,100
do iter=1,50

call ice_shelf_solve_inner(CS, ISS, G, US, u_shlf, v_shlf, taudx, taudy, H_node, float_cond, &
ISS%hmask, conv_flag, iters, time, Phi, Phisub)
Expand Down Expand Up @@ -1775,7 +1791,7 @@ subroutine calc_shelf_driving_stress(CS, ISS, G, US, taudx, taudy, OD)
intent(inout) :: taudx !< X-direction driving stress at q-points [kg L s-2 ~> kg m s-2]
real, dimension(SZDIB_(G),SZDJB_(G)), &
intent(inout) :: taudy !< Y-direction driving stress at q-points [kg L s-2 ~> kg m s-2]
! This will become [R L3 Z T-2 ~> kg m s-2]
! This will become [R L3 Z T-2 ~> kg m s-2]

! driving stress!

Expand All @@ -1790,12 +1806,14 @@ subroutine calc_shelf_driving_stress(CS, ISS, G, US, taudx, taudy, OD)

real, dimension(SIZE(OD,1),SIZE(OD,2)) :: S, & ! surface elevation [Z ~> m].
BASE ! basal elevation of shelf/stream [Z ~> m].
real, pointer, dimension(:,:,:,:) :: Phi => NULL() ! The gradients of bilinear basis elements at Gaussian
! quadrature points surrounding the cell vertices [m-1].


real :: rho, rhow, rhoi_rhow ! Ice and ocean densities [R ~> kg m-3]
real :: sx, sy ! Ice shelf top slopes [Z L-1 ~> nondim]
real :: neumann_val ! [R Z L2 T-2 ~> kg s-2]
real :: dxh, dyh ! Local grid spacing [L ~> m]
real :: dxh, dyh,Dx,Dy ! Local grid spacing [L ~> m]
real :: grav ! The gravitational acceleration [L2 Z-1 T-2 ~> m s-2]

integer :: i, j, iscq, iecq, jscq, jecq, isd, jsd, is, js, iegq, jegq
Expand All @@ -1813,6 +1831,7 @@ subroutine calc_shelf_driving_stress(CS, ISS, G, US, taudx, taudy, OD)
is = iscq - 1; js = jscq - 1
i_off = G%idg_offset ; j_off = G%jdg_offset


rho = CS%density_ice
rhow = CS%density_ocean_avg
grav = CS%g_Earth
Expand All @@ -1821,13 +1840,14 @@ subroutine calc_shelf_driving_stress(CS, ISS, G, US, taudx, taudy, OD)

! or is this faster?
BASE(:,:) = -CS%bed_elev(:,:) + OD(:,:)
S(:,:) = BASE(:,:) + ISS%h_shelf(:,:)

S(:,:) = -CS%bed_elev(:,:) + ISS%h_shelf(:,:)
! check whether the ice is floating or grounded
do j=jsc-G%domain%njhalo,jec+G%domain%njhalo
do i=isc-G%domain%nihalo,iec+G%domain%nihalo
if (rhoi_rhow * ISS%h_shelf(i,j) - CS%bed_elev(i,j) <= 0) then
S(i,j) = (1 - rhoi_rhow)*ISS%h_shelf(i,j)
else
S(i,j)=ISS%h_shelf(i,j)-CS%bed_elev(i,j)
endif
enddo
enddo
Expand All @@ -1838,7 +1858,8 @@ subroutine calc_shelf_driving_stress(CS, ISS, G, US, taudx, taudy, OD)
sy = 0
dxh = G%dxT(i,j)
dyh = G%dyT(i,j)

Dx=dxh
Dy=dyh
if (ISS%hmask(i,j) == 1) then ! we are inside the global computational bdry, at an ice-filled cell

! calculate sx
Expand All @@ -1857,20 +1878,22 @@ subroutine calc_shelf_driving_stress(CS, ISS, G, US, taudx, taudy, OD)
else ! interior
if (ISS%hmask(i+1,j) == 1) then
cnt = cnt+1
Dx =dxh+ G%dxT(i+1,j)
sx = S(i+1,j)
else
sx = S(i,j)
endif
if (ISS%hmask(i-1,j) == 1) then
cnt = cnt+1
Dx =dxh+ G%dxT(i-1,j)
sx = sx - S(i-1,j)
else
sx = sx - S(i,j)
endif
if (cnt == 0) then
sx = 0
else
sx = sx / (cnt * dxh)
sx = sx / ( Dx)
endif
endif

Expand All @@ -1892,20 +1915,22 @@ subroutine calc_shelf_driving_stress(CS, ISS, G, US, taudx, taudy, OD)
else ! interior
if (ISS%hmask(i,j+1) == 1) then
cnt = cnt+1
Dy =dyh+ G%dyT(i,j+1)
sy = S(i,j+1)
else
sy = S(i,j)
endif
if (ISS%hmask(i,j-1) == 1) then
cnt = cnt+1
sy = sy - S(i,j-1)
Dy =dyh+ G%dyT(i,j-1)
else
sy = sy - S(i,j)
endif
if (cnt == 0) then
sy = 0
else
sy = sy / (cnt * dyh)
sy = sy / (Dy)
endif
endif

Expand All @@ -1930,10 +1955,10 @@ subroutine calc_shelf_driving_stress(CS, ISS, G, US, taudx, taudy, OD)
taudy(I,J) = taudy(I,J) - .25 * rho * grav * ISS%h_shelf(i,j) * sy * G%areaT(i,j)
endif
if (CS%ground_frac(i,j) == 1) then
! neumann_val = .5 * grav * (rho * ISS%h_shelf(i,j)**2 - rhow * CS%bed_elev(i,j)**2)
! neumann_val = (.5 * grav * (rho * ISS%h_shelf(i,j)**2 - rhow * CS%bed_elev(i,j)**2))
neumann_val = .5 * grav * (1-rho/rhow) * rho * ISS%h_shelf(i,j)**2
else
neumann_val = .5 * grav * (1-rho/rhow) * rho * ISS%h_shelf(i,j)**2
neumann_val = (.5 * grav * (1-rho/rhow) * rho * ISS%h_shelf(i,j)**2)
endif

if ((CS%u_face_mask(I-1,j) == 2) .OR. (ISS%hmask(i-1,j) == 0) .OR. (ISS%hmask(i-1,j) == 2) ) then
Expand Down Expand Up @@ -1971,7 +1996,6 @@ subroutine calc_shelf_driving_stress(CS, ISS, G, US, taudx, taudy, OD)
endif
enddo
enddo

end subroutine calc_shelf_driving_stress

subroutine init_boundary_values(CS, G, time, hmask, input_flux, input_thick, new_sim)
Expand Down Expand Up @@ -2528,8 +2552,8 @@ subroutine apply_boundary_values(CS, ISS, G, US, time, Phisub, H_node, ice_visc,
call pass_vector(u_bdry_contr, v_bdry_contr, G%domain, TO_ALL, BGRID_NE)
end subroutine apply_boundary_values


!> Update depth integrated viscosity, based on horizontal strain rates, and also update the
!! nonlinear part of the basal traction.
subroutine calc_shelf_visc(CS, ISS, G, US, u_shlf, v_shlf)
type(ice_shelf_dyn_CS), intent(inout) :: CS !< A pointer to the ice shelf control structure
type(ice_shelf_state), intent(in) :: ISS !< A structure with elements that describe
Expand All @@ -2540,9 +2564,9 @@ subroutine calc_shelf_visc(CS, ISS, G, US, u_shlf, v_shlf)
intent(inout) :: u_shlf !< The zonal ice shelf velocity [L T-1 ~> m s-1].
real, dimension(G%IsdB:G%IedB,G%JsdB:G%JedB), &
intent(inout) :: v_shlf !< The meridional ice shelf velocity [L T-1 ~> m s-1].

real, pointer, dimension(:,:,:,:) :: Phi => NULL() ! The gradients of bilinear basis elements at Gaussian
! quadrature points surrounding the cell vertices [m-1].
! update DEPTH_INTEGRATED viscosity, based on horizontal strain rates - this is for bilinear FEM solve
! so there is an "upper" and "lower" bilinear viscosity

! also this subroutine updates the nonlinear part of the basal traction

Expand All @@ -2553,7 +2577,7 @@ subroutine calc_shelf_visc(CS, ISS, G, US, u_shlf, v_shlf)
real :: Visc_coef, n_g
real :: ux, uy, vx, vy
real :: eps_min, dxh, dyh ! Velocity shears [T-1 ~> s-1]
real, dimension(8,4) :: Phi
! real, dimension(8,4) :: Phi
real, dimension(2) :: xquad
! real :: umid, vmid, unorm ! Velocities [L T-1 ~> m s-1]

Expand All @@ -2566,6 +2590,12 @@ subroutine calc_shelf_visc(CS, ISS, G, US, u_shlf, v_shlf)
is = iscq - 1; js = jscq - 1
i_off = G%idg_offset ; j_off = G%jdg_offset

allocate(Phi(1:8,1:4,isd:ied,jsd:jed), source=0.0)

do j=jsc,jec ; do i=isc,iec
call bilinear_shape_fn_grid(G, i, j, Phi(:,:,i,j))
enddo ; enddo

n_g = CS%n_glen; eps_min = CS%eps_glen_min
CS%ice_visc(:,:)=1e22
! Visc_coef = US%kg_m2s_to_RZ_T*US%m_to_L*US%Z_to_L*(CS%A_glen_isothermal)**(-1./CS%n_glen)
Expand All @@ -2575,21 +2605,35 @@ subroutine calc_shelf_visc(CS, ISS, G, US, u_shlf, v_shlf)
if ((ISS%hmask(i,j) == 1) .OR. (ISS%hmask(i,j) == 3)) then
Visc_coef = US%kg_m2s_to_RZ_T*US%m_to_L*US%Z_to_L*(CS%AGlen_visc(i,j))**(-1./CS%n_glen)

ux = ((u_shlf(I,J) + (u_shlf(I,J-1) + u_shlf(I,J+1))) - &
(u_shlf(I-1,J) + (u_shlf(I-1,J-1) + u_shlf(I-1,J+1)))) / (3*G%dxT(i,j))
vx = ((v_shlf(I,J) + v_shlf(I,J-1) + v_shlf(I,J+1)) - &
(v_shlf(I-1,J) + (v_shlf(I-1,J-1) + v_shlf(I-1,J+1)))) / (3*G%dxT(i,j))
uy = ((u_shlf(I,J) + (u_shlf(I-1,J) + u_shlf(I+1,J))) - &
(u_shlf(I,J-1) + (u_shlf(I-1,J-1) + u_shlf(I+1,J-1)))) / (3*G%dyT(i,j))
vy = ((v_shlf(I,J) + (v_shlf(I-1,J)+ v_shlf(I+1,J))) - &
(v_shlf(I,J-1) + (v_shlf(I-1,J-1)+ v_shlf(I+1,J-1)))) / (3*G%dyT(i,j))
do iq=1,2 ; do jq=1,2

ux = ( (u_shlf(I-1,J-1) * Phi(1,2*(jq-1)+iq,i,j) + &
u_shlf(I,J) * Phi(7,2*(jq-1)+iq,i,j)) + &
(u_shlf(I-1,J) * Phi(5,2*(jq-1)+iq,i,j) + &
u_shlf(I,J-1) * Phi(3,2*(jq-1)+iq,i,j)) )

vx = ( (v_shlf(I-1,J-1) * Phi(1,2*(jq-1)+iq,i,j) + &
v_shlf(I,J) * Phi(7,2*(jq-1)+iq,i,j)) + &
(v_shlf(I-1,J) * Phi(5,2*(jq-1)+iq,i,j) + &
v_shlf(I,J-1) * Phi(3,2*(jq-1)+iq,i,j)) )

uy = ( (u_shlf(I-1,J-1) * Phi(2,2*(jq-1)+iq,i,j) + &
u_shlf(I,J) * Phi(8,2*(jq-1)+iq,i,j)) + &
(u_shlf(I-1,J) * Phi(6,2*(jq-1)+iq,i,j) + &
u_shlf(I,J-1) * Phi(4,2*(jq-1)+iq,i,j)) )

vy = ( (v_shlf(I-1,j-1) * Phi(2,2*(jq-1)+iq,i,j) + &
v_shlf(I,J) * Phi(8,2*(jq-1)+iq,i,j)) + &
(v_shlf(I-1,J) * Phi(6,2*(jq-1)+iq,i,j) + &
v_shlf(I,J-1) * Phi(4,2*(jq-1)+iq,i,j)) )
enddo ; enddo
! CS%ice_visc(i,j) =1e15*(G%areaT(i,j) * ISS%h_shelf(i,j)) ! constant viscocity for debugging
CS%ice_visc(i,j) = 0.5 * Visc_coef * (G%areaT(i,j) * ISS%h_shelf(i,j)) * &
(US%s_to_T**2 * (ux**2 + vy**2 + ux*vy + 0.25*(uy+vx)**2 + eps_min**2))**((1.-n_g)/(2.*n_g))
endif
enddo
enddo

deallocate(Phi)
end subroutine calc_shelf_visc

subroutine calc_shelf_taub(CS, ISS, G, US, u_shlf, v_shlf)
Expand Down
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