MODULE icbthm !!====================================================================== !! *** MODULE icbthm *** !! Icebergs: thermodynamics routines for icebergs !!====================================================================== !! History : 3.3.1 ! 2010-01 (Martin&Adcroft) Original code !! - ! 2011-03 (Madec) Part conversion to NEMO form !! - ! Removal of mapping from another grid !! - ! 2011-04 (Alderson) Split into separate modules !! - ! 2011-05 (Alderson) Use tmask instead of tmask_i !!---------------------------------------------------------------------- !!---------------------------------------------------------------------- !! icb_thm : initialise !! reference for equations - M = Martin + Adcroft, OM 34, 2010 !!---------------------------------------------------------------------- USE par_oce ! NEMO parameters USE dom_oce ! NEMO domain USE in_out_manager ! NEMO IO routines, numout in particular USE iom USE lib_mpp ! NEMO MPI routines, ctl_stop in particular USE phycst ! NEMO physical constants USE sbc_oce USE icb_oce ! define iceberg arrays USE icbutl ! iceberg utility routines USE icbdia ! iceberg budget routines IMPLICIT NONE PRIVATE PUBLIC icb_thm ! routine called in icbstp.F90 module !! $Id$ CONTAINS SUBROUTINE icb_thm( kt ) !!---------------------------------------------------------------------- !! *** ROUTINE icb_thm *** !! !! ** Purpose : compute the iceberg thermodynamics. !! !! ** Method : - See Martin & Adcroft, Ocean Modelling 34, 2010 !!---------------------------------------------------------------------- INTEGER, INTENT(in) :: kt ! timestep number, just passed to icb_utl_print_berg ! INTEGER :: ii, ij REAL(wp) :: zM, zT, zW, zL, zSST, zVol, zLn, zWn, zTn, znVol, zIC, zDn REAL(wp) :: zMv, zMe, zMb, zmelt, zdvo, zdva, zdM, zSs, zdMe, zdMb, zdMv REAL(wp) :: zMnew, zMnew1, zMnew2, zheat REAL(wp) :: zMbits, znMbits, zdMbitsE, zdMbitsM, zLbits, zAbits, zMbb REAL(wp) :: zxi, zyj, zff, z1_rday, z1_e1e2, zdt, z1_dt, z1_dt_e1e2 TYPE(iceberg), POINTER :: this, next TYPE(point) , POINTER :: pt !!---------------------------------------------------------------------- ! z1_rday = 1._wp / rday ! we're either going to ignore berg fresh water melt flux and associated heat ! or we pass it into the ocean, so at this point we set them both to zero, ! accumulate the contributions to them from each iceberg in the while loop following ! and then pass them (or not) to the ocean ! berg_grid%floating_melt(:,:) = 0._wp berg_grid%calving_hflx(:,:) = 0._wp this => first_berg DO WHILE( associated(this) ) ! pt => this%current_point nknberg = this%number(1) CALL icb_utl_interp( pt%xi, pt%e1, pt%uo, pt%ui, pt%ua, pt%ssh_x, & & pt%yj, pt%e2, pt%vo, pt%vi, pt%va, pt%ssh_y, & & pt%sst, pt%cn, pt%hi, zff ) ! zSST = pt%sst zIC = MIN( 1._wp, pt%cn + rn_sicn_shift ) ! Shift sea-ice concentration !!gm ??? zM = pt%mass zT = pt%thickness ! total thickness ! D = (rn_rho_bergs/pp_rho_seawater)*zT ! draught (keel depth) ! F = zT - D ! freeboard zW = pt%width zL = pt%length zxi = pt%xi ! position in (i,j) referential zyj = pt%yj ii = INT( zxi + 0.5 ) ! T-cell of the berg ii = mi1( ii ) ij = INT( zyj + 0.5 ) ij = mj1( ij ) zVol = zT * zW * zL zdt = berg_dt ; z1_dt = 1._wp / zdt ! Environment zdvo = SQRT( (pt%uvel-pt%uo)**2 + (pt%vvel-pt%vo)**2 ) zdva = SQRT( (pt%ua -pt%uo)**2 + (pt%va -pt%vo)**2 ) zSs = 1.5 * SQRT( zdva ) + 0.1 * zdva ! Sea state (eqn M.A9) ! Melt rates in m/s (i.e. division by rday) zMv = MAX( 7.62e-3*zSST+1.29e-3*(zSST**2) , 0._wp ) * z1_rday ! Buoyant convection at sides (eqn M.A10) zMb = MAX( 0.58*(zdvo**0.8)*(zSST+4.0)/(zL**0.2) , 0._wp ) * z1_rday ! Basal turbulent melting (eqn M.A7 ) zMe = MAX( 1./12.*(zSST+2.)*zSs*(1+cos(rpi*(zIC**3))) , 0._wp ) * z1_rday ! Wave erosion (eqn M.A8 ) IF( ln_operator_splitting ) THEN ! Operator split update of volume/mass zTn = MAX( zT - zMb*zdt , 0._wp ) ! new total thickness (m) znVol = zTn * zW * zL ! new volume (m^3) zMnew1 = (znVol/zVol) * zM ! new mass (kg) zdMb = zM - zMnew1 ! mass lost to basal melting (>0) (kg) ! zLn = MAX( zL - zMv*zdt , 0._wp ) ! new length (m) zWn = MAX( zW - zMv*zdt , 0._wp ) ! new width (m) znVol = zTn * zWn * zLn ! new volume (m^3) zMnew2 = (znVol/zVol) * zM ! new mass (kg) zdMv = zMnew1 - zMnew2 ! mass lost to buoyant convection (>0) (kg) ! zLn = MAX( zLn - zMe*zdt , 0._wp ) ! new length (m) zWn = MAX( zWn - zMe*zdt , 0._wp ) ! new width (m) znVol = zTn * zWn * zLn ! new volume (m^3) zMnew = ( znVol / zVol ) * zM ! new mass (kg) zdMe = zMnew2 - zMnew ! mass lost to erosion (>0) (kg) zdM = zM - zMnew ! mass lost to all erosion and melting (>0) (kg) ! ELSE ! Update dimensions of berg zLn = MAX( zL -(zMv+zMe)*zdt ,0._wp ) ! (m) zWn = MAX( zW -(zMv+zMe)*zdt ,0._wp ) ! (m) zTn = MAX( zT - zMb *zdt ,0._wp ) ! (m) ! Update volume and mass of berg znVol = zTn*zWn*zLn ! (m^3) zMnew = (znVol/zVol)*zM ! (kg) zdM = zM - zMnew ! (kg) zdMb = (zM/zVol) * (zW* zL ) *zMb*zdt ! approx. mass loss to basal melting (kg) zdMe = (zM/zVol) * (zT*(zW+zL)) *zMe*zdt ! approx. mass lost to erosion (kg) zdMv = (zM/zVol) * (zT*(zW+zL)) *zMv*zdt ! approx. mass loss to buoyant convection (kg) ENDIF IF( rn_bits_erosion_fraction > 0._wp ) THEN ! Bergy bits ! zMbits = pt%mass_of_bits ! mass of bergy bits (kg) zdMbitsE = rn_bits_erosion_fraction * zdMe ! change in mass of bits (kg) znMbits = zMbits + zdMbitsE ! add new bergy bits to mass (kg) zLbits = MIN( zL, zW, zT, 40._wp ) ! assume bergy bits are smallest dimension or 40 meters zAbits = ( zMbits / rn_rho_bergs ) / zLbits ! Effective bottom area (assuming T=Lbits) zMbb = MAX( 0.58*(zdvo**0.8)*(zSST+2.0)/(zLbits**0.2), 0.) * z1_rday ! Basal turbulent melting (for bits) zMbb = rn_rho_bergs * zAbits * zMbb ! in kg/s zdMbitsM = MIN( zMbb*zdt , znMbits ) ! bergy bits mass lost to melting (kg) znMbits = znMbits-zdMbitsM ! remove mass lost to bergy bits melt IF( zMnew == 0._wp ) THEN ! if parent berg has completely melted then zdMbitsM = zdMbitsM + znMbits ! instantly melt all the bergy bits znMbits = 0._wp ENDIF ELSE ! No bergy bits zAbits = 0._wp zdMbitsE = 0._wp zdMbitsM = 0._wp znMbits = pt%mass_of_bits ! retain previous value incase non-zero ENDIF ! use tmask rather than tmask_i when dealing with icebergs IF( tmask(ii,ij,1) /= 0._wp ) THEN ! Add melting to the grid and field diagnostics z1_e1e2 = 1._wp / e1e2t(ii,ij) * this%mass_scaling z1_dt_e1e2 = z1_dt * z1_e1e2 zmelt = ( zdM - ( zdMbitsE - zdMbitsM ) ) * z1_dt ! kg/s berg_grid%floating_melt(ii,ij) = berg_grid%floating_melt(ii,ij) + zmelt * z1_e1e2 ! kg/m2/s ! zheat = zmelt * pt%heat_density ! kg/s x J/kg = J/s zheat = zmelt * lfus !rma kg/s x J/kg (latent heat of fusion) = J/s berg_grid%calving_hflx (ii,ij) = berg_grid%calving_hflx (ii,ij) + zheat * z1_e1e2 ! W/m2 CALL icb_dia_melt( ii, ij, zMnew, zheat, this%mass_scaling, & & zdM, zdMbitsE, zdMbitsM, zdMb, zdMe, & & zdMv, z1_dt_e1e2 ) ELSE WRITE(numout,*) 'icb_thm: berg ',this%number(:),' appears to have grounded at ',narea,ii,ij CALL icb_utl_print_berg( this, kt ) WRITE(numout,*) 'msk=',tmask(ii,ij,1), e1e2t(ii,ij) CALL ctl_stop('icb_thm', 'berg appears to have grounded!') ENDIF ! Rolling zDn = ( rn_rho_bergs / pp_rho_seawater ) * zTn ! draught (keel depth) IF( zDn > 0._wp .AND. MAX(zWn,zLn) < SQRT( 0.92*(zDn**2) + 58.32*zDn ) ) THEN zT = zTn zTn = zWn zWn = zT endif ! Store the new state of iceberg (with L>W) pt%mass = zMnew pt%mass_of_bits = znMbits pt%thickness = zTn pt%width = min(zWn,zLn) pt%length = max(zWn,zLn) next=>this%next !!gm add a test to avoid over melting ? IF( zMnew <= 0._wp ) THEN ! Delete the berg if completely melted CALL icb_utl_delete( first_berg, this ) ! ELSE ! Diagnose mass distribution on grid z1_e1e2 = 1._wp / e1e2t(ii,ij) * this%mass_scaling CALL icb_dia_size( ii, ij, zWn, zLn, zAbits, & & this%mass_scaling, zMnew, znMbits, z1_e1e2) ENDIF ! this=>next ! END DO ! now use melt and associated heat flux in ocean (or not) ! IF(.NOT. ln_passive_mode ) THEN emp (:,:) = emp (:,:) - berg_grid%floating_melt(:,:) qns (:,:) = qns (:,:) - berg_grid%calving_hflx (:,:) ENDIF ! END SUBROUTINE icb_thm !!====================================================================== END MODULE icbthm