--- MITgcm/pkg/dic/fe_chem.F	2005/12/12 19:07:36	1.7
+++ MITgcm/pkg/dic/fe_chem.F	2008/04/18 19:32:12	1.14
@@ -1,8 +1,7 @@
-C $Header: /home/ubuntu/mnt/e9_copy/MITgcm/pkg/dic/fe_chem.F,v 1.7 2005/12/12 19:07:36 stephd Exp $
+C $Header: /home/ubuntu/mnt/e9_copy/MITgcm/pkg/dic/fe_chem.F,v 1.14 2008/04/18 19:32:12 stephd Exp $
 C $Name:  $
 
 #include "DIC_OPTIONS.h"
-#include "GCHEM_OPTIONS.h"
 
 CStartOfInterFace
       SUBROUTINE Fe_CHEM(
@@ -22,9 +21,7 @@
 #include "EEPARAMS.h"
 #include "PARAMS.h"
 #include "GRID.h"
-#include "DIC_BIOTIC.h"
-#include "PTRACERS_SIZE.h"
-#include "PTRACERS.h"
+#include "DIC_VARS.h"
 
 C     == Routine arguments ==                
 C     bi, bj, iMin, iMax, jMin, jMax - Range of points for which calculation
@@ -34,12 +31,16 @@
       _RL  fe(1-OLx:sNx+OLx,1-OLy:sNy+OLy,Nr,nSx,nSy)
       INTEGER bi,bj,iMin,iMax,jMin,jMax
       INTEGER myIter,myThid
+#ifdef AD_SAFE
+      _RL thx, thy, theps
+#endif
 CEndOfInterface
 
 #ifdef ALLOW_FE
 
       INTEGER I,J,K
       _RL  lig, FeL
+      _RL  tmpfe
 
 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCc
 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCc
@@ -55,23 +56,43 @@
 C ligand balance in surface layer
 C in surface layer
 
-       DO j=1-OLy,sNy+OLy
-        DO i=1-OLx,sNx+OLx
-         DO k=1,nR
-          IF(hFacC(i,j,k,bi,bj) .gt. 0.0)THEN
-
-C   Ligand,FeL,Fe calculation
+       DO j=jmin,jmax
+        DO i=imin,imax
+         DO k=1,Nr
+          IF (hFacC(i,j,k,bi,bj) .GT. 0. _d 0) THEN
+
+#ifdef DIC_NO_NEG
+              tmpfe=max(0. _d 0 , fe (i,j,k,bi,bj))
+#else
+              tmpfe=fe (i,j,k,bi,bj)
+#endif
             
-              lig=(-ligand_stab*fe (i,j,k,bi,bj)+
-     &              ligand_stab*ligand_tot-1
-     &             +((ligand_stab*fe (i,j,k,bi,bj)
-     &                -ligand_stab*ligand_tot+1)**2+4
-     &                *ligand_stab*ligand_tot)**0.5)/(2*ligand_stab)
+C   Ligand,FeL,Fe calculation
+              lig=(-ligand_stab*tmpfe +
+     &              ligand_stab*ligand_tot-1. _d 0
+     &             +((ligand_stab*tmpfe 
+     &                -ligand_stab*ligand_tot+1. _d 0)**2
+     &               +4. _d 0*ligand_stab*ligand_tot)**0.5 _d 0
+     &            )/(2. _d 0*ligand_stab)
  
               FeL = ligand_tot-lig
-              freefe(i,j,k,bi,bj) = fe (i,j,k,bi,bj)-FeL
+              if (tmpfe.eq.0. _d 0) then
+                freefe(i,j,k,bi,bj) = tmpfe -FeL
+              else
+                freefe(i,j,k,bi,bj) = 0. _d 0
+              endif
 #ifdef MINFE
+#ifdef AD_SAFE
+              thx=freefe(i,j,k,bi,bj)
+              thy=freefemax
+              theps=1. _d -8
+              freefe(i,j,k,bi,bj) =
+     &                 ( 1. _d 0 - tanh((thx-thy)/theps) ) * thx/2.+
+     &                 ( 1. _d 0 + tanh((thx-thy)/theps) ) * thy/2.
+
+#else
               freefe(i,j,k,bi,bj) = min(freefe(i,j,k,bi,bj),freefemax)
+#endif
               fe(i,j,k,bi,bj) = FeL+freefe(i,j,k,bi,bj)
 #endif
           END IF  
@@ -81,4 +102,4 @@
 c
 #endif 
         RETURN
-        END                      
+        END