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C $Header: /u/gcmpack/MITgcm/pkg/icefront/icefront_thermodynamics.F,v 1.8 2010/04/22 18:24:44 yunx Exp $ |
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C $Name: $ |
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#include "ICEFRONT_OPTIONS.h" |
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CBOP |
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C !ROUTINE: ICEFRONT_THERMODYNAMICS |
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C !INTERFACE: |
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SUBROUTINE ICEFRONT_THERMODYNAMICS( |
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I myTime, myIter, myThid ) |
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C !DESCRIPTION: \bv |
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C *=============================================================* |
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C | S/R ICEFRONT_THERMODYNAMICS |
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C | o shelf-ice main routine. |
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C | compute temperature and (virtual) salt flux at the |
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C | shelf-ice ocean interface |
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C | |
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C | stresses at the ice/water interface are computed in separate |
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C | routines that are called from mom_fluxform/mom_vecinv |
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C *=============================================================* |
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C !USES: |
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IMPLICIT NONE |
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C === Global variables === |
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#include "SIZE.h" |
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#include "EEPARAMS.h" |
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#include "PARAMS.h" |
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#include "GRID.h" |
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#include "DYNVARS.h" |
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#include "FFIELDS.h" |
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#include "ICEFRONT.h" |
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C !INPUT/OUTPUT PARAMETERS: |
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C === Routine arguments === |
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C myIter :: iteration counter for this thread |
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C myTime :: time counter for this thread |
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C myThid :: thread number for this instance of the routine. |
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_RL myTime |
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INTEGER myIter |
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INTEGER myThid |
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CEOP |
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#ifdef ALLOW_ICEFRONT |
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C !LOCAL VARIABLES : |
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C === Local variables === |
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C I,J,K,bi,bj :: loop counters |
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C tLoc, sLoc, pLoc :: local in-situ temperature, salinity, pressure |
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C thetaICE :: averaged temperature of glacier interior |
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C theta/saltFreeze :: temperature and salinity of water at the |
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C ice-ocean interface (at the freezing point) |
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C FreshWaterFlux :: fresh water flux due to freezing or melting of ice |
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C front in kg/m^2/s (positive increases ocean salinity) |
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C HeatFlux :: ice front heat flux in W/m^2 |
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C (positive decreases ocean temperature) |
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C auxiliary variables and abbreviations: |
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C a0, b, c0 |
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C eps1, eps2, eps3, eps4, eps5, eps6, eps7 |
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C aqe, bqe, cqe, discrim, recip_aqe |
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INTEGER I,J,K |
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INTEGER bi,bj |
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_RL tLoc, sLoc, pLoc |
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_RL uLoc, vLoc, wLoc, speedLoc |
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_RL thetaICE |
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_RL thetaFreeze, saltFreeze |
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_RS FreshWaterFlux( 1:sNx, 1:sNy ) |
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_RS HeatFlux ( 1:sNx, 1:sNy ) |
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_RS ICEFRONTheatTransCoeff ( 1:sNx, 1:sNy ) |
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_RS ICEFRONTsaltTransCoeff ( 1:sNx, 1:sNy ) |
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_RL a0, b, c0 |
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_RL eps1, eps2, eps3, eps4, eps5, eps6, eps7 |
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_RL aqe, bqe, cqe, discrim, recip_aqe |
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_RL SW_TEMP |
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EXTERNAL SW_TEMP |
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C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----| |
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#ifdef ALLOW_SUBGLACIAL_RUNOFF |
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IF ( SGrunofffile .NE. ' ' ) THEN |
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CALL SGRUNOFF_READ(myTime, myIter, myThid) |
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ENDIF |
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#endif /* ALLOW_SUBGLACIAL_RUNOFF*/ |
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C Linear dependence of freezing point on salinity. |
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a0 = -0.0575 _d 0 |
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c0 = 0.0901 _d 0 |
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b = -7.61 _d -4 |
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DO bj = myByLo(myThid), myByHi(myThid) |
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DO bi = myBxLo(myThid), myBxHi(myThid) |
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DO K = 1, Nr |
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DO J = 1, sNy |
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DO I = 1, sNx |
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IF( ICEFRONTlength(I,J,bi,bj) .GT. 0. _d 0 |
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& .AND. K .LE. K_icefront(I,J,bi,bj) ) THEN |
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C Make local copies of velocity, temperature, salinity and depth (pressure). |
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uLoc = 0.5*(uVel(I,J,K,bi,bj) +uVel(I+1,J,K,bi,bj)) |
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vLoc = 0.5*(vVel(I,J,K,bi,bj) +vVel(I,J+1,K,bi,bj)) |
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wLoc = 0.5*(wVel(I,J,K,bi,bj) +wVel(I,J,K+1,bi,bj)) |
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speedLoc = SQRT(uLoc*uLoc + vLoc*vLoc + wLoc*wLoc) |
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C A few abbreviations. |
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C IF (myTime .GT. 600) THEN |
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ICEFRONTheatTransCoeff(I,J) = 1.1 _d -03 |
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C & *abs(wVEL(I,J,K,bi,bj)) |
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& *abs(speedLoc) |
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& +1.0 _d -04 |
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ICEFRONTsaltTransCoeff(I,J) = 3.1 _d -05 |
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C & *abs(wVEL(I,J,K,bi,bj)) |
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& *abs(speedLoc) |
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& +5.05 _d -07 |
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C ENDIF |
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eps1 = rUnit2mass*HeatCapacity_Cp*ICEFRONTheatTransCoeff(I,J) |
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eps2 = rUnit2mass*ICEFRONTlatentHeat*ICEFRONTsaltTransCoeff(I,J) |
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eps3 = rUnit2mass*ICEFRONTheatCapacity_Cp |
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& *ICEFRONTsaltTransCoeff(I,J) |
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eps5 = mass2rUnit/HeatCapacity_Cp |
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aqe = a0 *(-eps1+eps3) |
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recip_aqe = 0.5 _d 0/aqe |
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C Make local copies of temperature, salinity and depth (pressure). |
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pLoc = ABS(rC(k)) |
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tLoc = theta(I,J,K,bi,bj) |
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sLoc = MAX(salt(I,J,K,bi,bj), 0. _d 0) |
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C Turn potential temperature into in-situ temperature. |
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tLoc = SW_TEMP(sLoc,tLoc,pLoc,0.D0) |
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C Get ice temperature. Assume linear ice temperature change from |
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C the surface (ICEFRONTthetaSurface) to the base(0 degree C). |
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IF ( K .EQ. K_icefront(I,J,bi,bj)) THEN |
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pLoc = 0.5*(ABS(R_icefront(I,J,bi,bj))+ABS(rF(K))) |
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ENDIF |
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thetaICE = ICEFRONTthetaSurface* |
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& (R_icefront(I,J,bi,bj)-pLoc) |
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& / R_icefront(I,J,bi,bj) |
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C A few more abbreviations. |
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eps4 = b*pLoc + c0 |
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eps6 = eps4 - tLoc |
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eps7 = eps4 - thetaIce |
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C Solve quadratic equation to get salinity at icefront-ocean interface. |
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bqe = - eps1*eps6 -sLoc*a0*eps3 + eps3*eps7 + eps2 |
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cqe = -(eps2+eps3*eps7)*sLoc |
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discrim = bqe*bqe - 4. _d 0*aqe*cqe |
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saltFreeze = (- bqe - SQRT(discrim))*recip_aqe |
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IF ( saltFreeze .LT. 0. _d 0 ) |
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& saltFreeze = (- bqe + SQRT(discrim))*recip_aqe |
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thetaFreeze = a0*saltFreeze + eps4 |
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C-- Calculate the outward (leaving the ocean) heat (W/m^2) |
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C and freshwater (kg/m^2/s). |
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C Sign convention: inward (negative) fresh water flux implies glacier |
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C melting due to outward (positive) heat flux. |
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FreshWaterFlux(I,J) = maskC(I,J,K,bi,bj) * |
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& eps1 * ( thetaFreeze - tLoc ) / |
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& (ICEFRONTlatentHeat + ICEFRONTheatCapacity_cp* |
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& (thetaFreeze - thetaIce)) |
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HeatFlux(I,J) = maskC(I,J,K,bi,bj) * HeatCapacity_Cp * |
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& ( -rUnit2mass*ICEFRONTheatTransCoeff(I,J) + |
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& FreshWaterFlux(I,J) ) * ( thetaFreeze - tLoc ) |
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C Compute tendencies. |
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icefront_TendT(i,j,K,bi,bj) = - HeatFlux(I,J)* eps5 |
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icefront_TendS(i,j,K,bi,bj) = FreshWaterFlux(I,J) * |
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& mass2rUnit * sLoc |
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C Scale by icefrontlength, which is the ratio of the horizontal length |
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C of the ice front in each model grid cell divided by the grid cell area. |
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IF (k .LT. k_icefront(i,j,bi,bj)) THEN |
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icefront_TendT(i,j,K,bi,bj) = icefront_TendT(i,j,K,bi,bj) |
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& * ICEFRONTlength(i,j,bi,bj) |
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icefront_TendS(i,j,K,bi,bj) = icefront_TendS(i,j,K,bi,bj) |
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& * ICEFRONTlength(i,j,bi,bj) |
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ELSEIF (k .EQ. k_icefront(i,j,bi,bj)) THEN |
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C At the bottom of the ice shelf there is additional scaling due |
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C to the partial depth of the ice front. |
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icefront_TendT(i,j,K,bi,bj) = icefront_TendT(i,j,K,bi,bj) |
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& * ICEFRONTlength(i,j,bi,bj) |
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& * (ABS(R_icefront(I,J,bi,bj))-ABS(rF(K))) |
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& * recip_drF(K) |
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icefront_TendS(i,j,K,bi,bj) = icefront_TendS(i,j,K,bi,bj) |
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& * ICEFRONTlength(i,j,bi,bj) |
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& * (ABS(R_icefront(I,J,bi,bj))-ABS(rF(K))) |
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& * recip_drF(K) |
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ENDIF |
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ELSE ! K .LE. K_icefront |
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HeatFlux (I,J) = 0. _d 0 |
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FreshWaterFlux(I,J) = 0. _d 0 |
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ENDIF ! K .LE. K_icefront |
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ENDDO ! I = 1, sNx |
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ENDDO ! J = 1, sNy |
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#ifdef ALLOW_DIAGNOSTICS |
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IF ( useDiagnostics ) THEN |
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CALL DIAGNOSTICS_FILL_RS(FreshWaterFlux,'ICFfwFlx', |
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& k,1,3,bi,bj,myThid) |
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CALL DIAGNOSTICS_FILL_RS(HeatFlux, 'ICFhtFlx', |
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& k,1,3,bi,bj,myThid) |
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ENDIF |
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#endif /* ALLOW_DIAGNOSTICS */ |
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ENDDO ! K = 1, Nr |
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ENDDO ! bi = myBxLo, myBxHi |
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ENDDO ! bj = myByLo, myByHi |
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#endif /* ALLOW_ICEFRONT */ |
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RETURN |
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END |
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