Fix bug for bgc diagnostic wdet100 (this affects cycle4 output wdet10…

…0 only).

Due to this bug, wdet100 in cycle4 represents sea surface detritus concentration multiplied by the detritus sinking speed (specified as a wombat parameter).

src/mom5/ocean_csiro_bgc/csiro_bgc.F90

@@ -1978,7 +1978,7 @@ subroutine csiro_bgc_source(isc, iec, jsc, jec, isd, ied, jsd, jed, T_prog, grid
 
 !det export at 100 m
 if (id_wdet100 .gt. 0) then
-  wdet100(:,:) = wdetbio(isc:iec,jsc:jec)*t_prog(ind_det)%field(isc:iec,jsc:jec,minloc(grid%zt(:)-100,dim=1),time%taum1)
+  wdet100(:,:) = wdetbio(isc:iec,jsc:jec)*t_prog(ind_det)%field(isc:iec,jsc:jec,minloc(abs(grid%zt(:)-100),dim=1),time%taum1)
   used = send_data(id_wdet100, wdet100(isc:iec,jsc:jec),          &
        time%model_time, rmask = grid%tmask(isc:iec,jsc:jec,1))
 endif