| 1 | MODULE icbthm |
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| 2 | |
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| 3 | !!====================================================================== |
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| 4 | !! *** MODULE icbthm *** |
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| 5 | !! Icebergs: thermodynamics routines for icebergs |
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| 6 | !!====================================================================== |
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| 7 | !! History : 3.3.1 ! 2010-01 (Martin&Adcroft) Original code |
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| 8 | !! - ! 2011-03 (Madec) Part conversion to NEMO form |
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| 9 | !! - ! Removal of mapping from another grid |
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| 10 | !! - ! 2011-04 (Alderson) Split into separate modules |
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| 11 | !! - ! 2011-05 (Alderson) Use tmask instead of tmask_i |
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| 12 | !!---------------------------------------------------------------------- |
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| 13 | !!---------------------------------------------------------------------- |
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| 14 | !! icb_thm : initialise |
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| 15 | !! reference for equations - M = Martin + Adcroft, OM 34, 2010 |
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| 16 | !!---------------------------------------------------------------------- |
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| 17 | USE par_oce ! NEMO parameters |
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| 18 | USE dom_oce ! NEMO domain |
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| 19 | USE in_out_manager ! NEMO IO routines, numout in particular |
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| 20 | USE lib_mpp ! NEMO MPI routines, ctl_stop in particular |
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| 21 | USE phycst ! NEMO physical constants |
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| 22 | USE sbc_oce |
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| 23 | |
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| 24 | USE icb_oce ! define iceberg arrays |
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| 25 | USE icbutl ! iceberg utility routines |
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| 26 | USE icbdia ! iceberg budget routines |
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| 27 | |
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| 28 | IMPLICIT NONE |
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| 29 | PRIVATE |
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| 30 | |
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| 31 | PUBLIC icb_thm ! routine called in icbstp.F90 module |
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| 32 | |
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| 33 | !! $Id$ |
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| 34 | CONTAINS |
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| 35 | |
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| 36 | SUBROUTINE icb_thm( kt ) |
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| 37 | !!---------------------------------------------------------------------- |
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| 38 | !! *** ROUTINE icb_thm *** |
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| 39 | !! |
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| 40 | !! ** Purpose : compute the iceberg thermodynamics. |
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| 41 | !! |
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| 42 | !! ** Method : - See Martin & Adcroft, Ocean Modelling 34, 2010 |
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| 43 | !!---------------------------------------------------------------------- |
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| 44 | INTEGER, INTENT(in) :: kt ! timestep number, just passed to icb_utl_print_berg |
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| 45 | ! |
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| 46 | INTEGER :: ii, ij |
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| 47 | REAL(wp) :: zM, zT, zW, zL, zSST, zVol, zLn, zWn, zTn, znVol, zIC, zDn |
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| 48 | REAL(wp) :: zMv, zMe, zMb, zmelt, zdvo, zdva, zdM, zSs, zdMe, zdMb, zdMv |
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| 49 | REAL(wp) :: zMnew, zMnew1, zMnew2, zheat |
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| 50 | REAL(wp) :: zMbits, znMbits, zdMbitsE, zdMbitsM, zLbits, zAbits, zMbb |
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| 51 | REAL(wp) :: zxi, zyj, zff, z1_rday, z1_e1e2, zdt, z1_dt, z1_dt_e1e2 |
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| 52 | TYPE(iceberg), POINTER :: this, next |
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| 53 | TYPE(point) , POINTER :: pt |
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| 54 | !!---------------------------------------------------------------------- |
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| 55 | ! |
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| 56 | z1_rday = 1._wp / rday |
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| 57 | |
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| 58 | ! we're either going to ignore berg fresh water melt flux and associated heat |
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| 59 | ! or we pass it into the ocean, so at this point we set them both to zero, |
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| 60 | ! accumulate the contributions to them from each iceberg in the while loop following |
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| 61 | ! and then pass them (or not) to the ocean |
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| 62 | ! |
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| 63 | berg_grid%floating_melt(:,:) = 0._wp |
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| 64 | berg_grid%calving_hflx(:,:) = 0._wp |
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| 65 | |
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| 66 | this => first_berg |
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| 67 | DO WHILE( associated(this) ) |
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| 68 | ! |
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| 69 | pt => this%current_point |
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| 70 | nknberg = this%number(1) |
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| 71 | CALL icb_utl_interp( pt%xi, pt%e1, pt%uo, pt%ui, pt%ua, pt%ssh_x, & |
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| 72 | & pt%yj, pt%e2, pt%vo, pt%vi, pt%va, pt%ssh_y, & |
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| 73 | & pt%sst, pt%cn, pt%hi, zff ) |
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| 74 | ! |
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| 75 | zSST = pt%sst |
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| 76 | zIC = MIN( 1._wp, pt%cn + rn_sicn_shift ) ! Shift sea-ice concentration !!gm ??? |
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| 77 | zM = pt%mass |
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| 78 | zT = pt%thickness ! total thickness |
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| 79 | ! D = (rn_rho_bergs/pp_rho_seawater)*zT ! draught (keel depth) |
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| 80 | ! F = zT - D ! freeboard |
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| 81 | zW = pt%width |
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| 82 | zL = pt%length |
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| 83 | zxi = pt%xi ! position in (i,j) referential |
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| 84 | zyj = pt%yj |
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| 85 | ii = INT( zxi + 0.5 ) ! T-cell of the berg |
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| 86 | ii = mi1( ii ) |
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| 87 | ij = INT( zyj + 0.5 ) |
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| 88 | ij = mj1( ij ) |
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| 89 | zVol = zT * zW * zL |
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| 90 | zdt = berg_dt ; z1_dt = 1._wp / zdt |
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| 91 | |
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| 92 | ! Environment |
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| 93 | zdvo = SQRT( (pt%uvel-pt%uo)**2 + (pt%vvel-pt%vo)**2 ) |
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| 94 | zdva = SQRT( (pt%ua -pt%uo)**2 + (pt%va -pt%vo)**2 ) |
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| 95 | zSs = 1.5 * SQRT( zdva ) + 0.1 * zdva ! Sea state (eqn M.A9) |
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| 96 | |
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| 97 | ! Melt rates in m/s (i.e. division by rday) |
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| 98 | zMv = MAX( 7.62e-3*zSST+1.29e-3*(zSST**2) , 0._wp ) * z1_rday ! Buoyant convection at sides (eqn M.A10) |
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| 99 | zMb = MAX( 0.58*(zdvo**0.8)*(zSST+4.0)/(zL**0.2) , 0._wp ) * z1_rday ! Basal turbulent melting (eqn M.A7 ) |
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| 100 | zMe = MAX( 1./12.*(zSST+2.)*zSs*(1+cos(rpi*(zIC**3))) , 0._wp ) * z1_rday ! Wave erosion (eqn M.A8 ) |
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| 101 | |
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| 102 | IF( ln_operator_splitting ) THEN ! Operator split update of volume/mass |
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| 103 | zTn = MAX( zT - zMb*zdt , 0._wp ) ! new total thickness (m) |
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| 104 | znVol = zTn * zW * zL ! new volume (m^3) |
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| 105 | zMnew1 = (znVol/zVol) * zM ! new mass (kg) |
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| 106 | zdMb = zM - zMnew1 ! mass lost to basal melting (>0) (kg) |
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| 107 | ! |
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| 108 | zLn = MAX( zL - zMv*zdt , 0._wp ) ! new length (m) |
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| 109 | zWn = MAX( zW - zMv*zdt , 0._wp ) ! new width (m) |
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| 110 | znVol = zTn * zWn * zLn ! new volume (m^3) |
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| 111 | zMnew2 = (znVol/zVol) * zM ! new mass (kg) |
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| 112 | zdMv = zMnew1 - zMnew2 ! mass lost to buoyant convection (>0) (kg) |
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| 113 | ! |
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| 114 | zLn = MAX( zLn - zMe*zdt , 0._wp ) ! new length (m) |
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| 115 | zWn = MAX( zWn - zMe*zdt , 0._wp ) ! new width (m) |
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| 116 | znVol = zTn * zWn * zLn ! new volume (m^3) |
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| 117 | zMnew = ( znVol / zVol ) * zM ! new mass (kg) |
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| 118 | zdMe = zMnew2 - zMnew ! mass lost to erosion (>0) (kg) |
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| 119 | zdM = zM - zMnew ! mass lost to all erosion and melting (>0) (kg) |
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| 120 | ! |
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| 121 | ELSE ! Update dimensions of berg |
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| 122 | zLn = MAX( zL -(zMv+zMe)*zdt ,0._wp ) ! (m) |
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| 123 | zWn = MAX( zW -(zMv+zMe)*zdt ,0._wp ) ! (m) |
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| 124 | zTn = MAX( zT - zMb *zdt ,0._wp ) ! (m) |
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| 125 | ! Update volume and mass of berg |
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| 126 | znVol = zTn*zWn*zLn ! (m^3) |
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| 127 | zMnew = (znVol/zVol)*zM ! (kg) |
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| 128 | zdM = zM - zMnew ! (kg) |
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| 129 | zdMb = (zM/zVol) * (zW* zL ) *zMb*zdt ! approx. mass loss to basal melting (kg) |
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| 130 | zdMe = (zM/zVol) * (zT*(zW+zL)) *zMe*zdt ! approx. mass lost to erosion (kg) |
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| 131 | zdMv = (zM/zVol) * (zT*(zW+zL)) *zMv*zdt ! approx. mass loss to buoyant convection (kg) |
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| 132 | ENDIF |
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| 133 | |
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| 134 | IF( rn_bits_erosion_fraction > 0._wp ) THEN ! Bergy bits |
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| 135 | ! |
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| 136 | zMbits = pt%mass_of_bits ! mass of bergy bits (kg) |
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| 137 | zdMbitsE = rn_bits_erosion_fraction * zdMe ! change in mass of bits (kg) |
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| 138 | znMbits = zMbits + zdMbitsE ! add new bergy bits to mass (kg) |
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| 139 | zLbits = MIN( zL, zW, zT, 40._wp ) ! assume bergy bits are smallest dimension or 40 meters |
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| 140 | zAbits = ( zMbits / rn_rho_bergs ) / zLbits ! Effective bottom area (assuming T=Lbits) |
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| 141 | zMbb = MAX( 0.58*(zdvo**0.8)*(zSST+2.0)/(zLbits**0.2), 0.) * z1_rday ! Basal turbulent melting (for bits) |
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| 142 | zMbb = rn_rho_bergs * zAbits * zMbb ! in kg/s |
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| 143 | zdMbitsM = MIN( zMbb*zdt , znMbits ) ! bergy bits mass lost to melting (kg) |
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| 144 | znMbits = znMbits-zdMbitsM ! remove mass lost to bergy bits melt |
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| 145 | IF( zMnew == 0._wp ) THEN ! if parent berg has completely melted then |
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| 146 | zdMbitsM = zdMbitsM + znMbits ! instantly melt all the bergy bits |
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| 147 | znMbits = 0._wp |
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| 148 | ENDIF |
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| 149 | ELSE ! No bergy bits |
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| 150 | zAbits = 0._wp |
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| 151 | zdMbitsE = 0._wp |
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| 152 | zdMbitsM = 0._wp |
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| 153 | znMbits = pt%mass_of_bits ! retain previous value incase non-zero |
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| 154 | ENDIF |
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| 155 | |
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| 156 | ! use tmask rather than tmask_i when dealing with icebergs |
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| 157 | IF( tmask(ii,ij,1) /= 0._wp ) THEN ! Add melting to the grid and field diagnostics |
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| 158 | z1_e1e2 = r1_e1e2t(ii,ij) * this%mass_scaling |
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| 159 | z1_dt_e1e2 = z1_dt * z1_e1e2 |
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| 160 | zmelt = ( zdM - ( zdMbitsE - zdMbitsM ) ) * z1_dt ! kg/s |
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| 161 | berg_grid%floating_melt(ii,ij) = berg_grid%floating_melt(ii,ij) + zmelt * z1_e1e2 ! kg/m2/s |
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| 162 | zheat = zmelt * pt%heat_density ! kg/s x J/kg = J/s |
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| 163 | berg_grid%calving_hflx (ii,ij) = berg_grid%calving_hflx (ii,ij) + zheat * z1_e1e2 ! W/m2 |
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| 164 | CALL icb_dia_melt( ii, ij, zMnew, zheat, this%mass_scaling, & |
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| 165 | & zdM, zdMbitsE, zdMbitsM, zdMb, zdMe, & |
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| 166 | & zdMv, z1_dt_e1e2 ) |
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| 167 | ELSE |
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| 168 | WRITE(numout,*) 'icb_thm: berg ',this%number(:),' appears to have grounded at ',narea,ii,ij |
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| 169 | CALL icb_utl_print_berg( this, kt ) |
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| 170 | WRITE(numout,*) 'msk=',tmask(ii,ij,1), e1e2t(ii,ij) |
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| 171 | CALL ctl_stop('icb_thm', 'berg appears to have grounded!') |
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| 172 | ENDIF |
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| 173 | |
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| 174 | ! Rolling |
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| 175 | zDn = ( rn_rho_bergs / pp_rho_seawater ) * zTn ! draught (keel depth) |
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| 176 | IF( zDn > 0._wp .AND. MAX(zWn,zLn) < SQRT( 0.92*(zDn**2) + 58.32*zDn ) ) THEN |
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| 177 | zT = zTn |
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| 178 | zTn = zWn |
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| 179 | zWn = zT |
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| 180 | endif |
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| 181 | |
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| 182 | ! Store the new state of iceberg (with L>W) |
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| 183 | pt%mass = zMnew |
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| 184 | pt%mass_of_bits = znMbits |
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| 185 | pt%thickness = zTn |
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| 186 | pt%width = min(zWn,zLn) |
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| 187 | pt%length = max(zWn,zLn) |
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| 188 | |
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| 189 | next=>this%next |
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| 190 | |
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| 191 | !!gm add a test to avoid over melting ? |
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| 192 | |
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| 193 | IF( zMnew <= 0._wp ) THEN ! Delete the berg if completely melted |
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| 194 | CALL icb_utl_delete( first_berg, this ) |
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| 195 | ! |
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| 196 | ELSE ! Diagnose mass distribution on grid |
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| 197 | z1_e1e2 = r1_e1e2t(ii,ij) * this%mass_scaling |
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| 198 | CALL icb_dia_size( ii, ij, zWn, zLn, zAbits, & |
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| 199 | & this%mass_scaling, zMnew, znMbits, z1_e1e2) |
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| 200 | ENDIF |
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| 201 | ! |
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| 202 | this=>next |
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| 203 | ! |
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| 204 | END DO |
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| 205 | |
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| 206 | ! now use melt and associated heat flux in ocean (or not) |
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| 207 | ! |
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| 208 | IF(.NOT. ln_passive_mode ) THEN |
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| 209 | emp (:,:) = emp (:,:) - berg_grid%floating_melt(:,:) |
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| 210 | !! qns (:,:) = qns (:,:) + berg_grid%calving_hflx (:,:) !!gm heat flux not yet properly coded ==>> need it, SOLVE that! |
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| 211 | ENDIF |
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| 212 | ! |
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| 213 | END SUBROUTINE icb_thm |
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| 214 | |
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| 215 | !!====================================================================== |
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| 216 | END MODULE icbthm |
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