fix(recom): correct variable sinking into benthos for Phy and Dia

Fix variable sinking into benthos for Phy and Dia

Frauke detected an error in variable sinking routine.
Despide, zero sinking speed for Phy and Dia in the
namelist.recom, the depth dependent sinking cause
Phy and Dia to reach benthos !!!!! We let
slow-sinking detritus to sink into
benthos with variable speed.

src/oce_ale_tracer.F90

@@ -1116,10 +1116,11 @@ subroutine ver_sinking_recom_benthos(tr_num,mesh)
 
 ! 1) Calculate sinking velociy for vertical sinking case
 ! ******************************************************
-        if (allow_var_sinking) then
-          if (any(recom_det_tracer_id == tracer_id(tr_num))) Vben = Vdet
-          if (any(recom_phy_tracer_id == tracer_id(tr_num))) Vben = VPhy
-          if (any(recom_dia_tracer_id == tracer_id(tr_num))) Vben = VDia
+
+        if (any(recom_det_tracer_id == tracer_id(tr_num))) Vben = Vdet
+        if (any(recom_phy_tracer_id == tracer_id(tr_num))) Vben = VPhy
+        if (any(recom_dia_tracer_id == tracer_id(tr_num))) Vben = VDia
+        if (allow_var_sinking .and. any(recom_det_tracer_id == tracer_id(tr_num))) then
           Vben = Vdet_a * abs(zbar_3d_n(:,n)) + Vben
         end if
 

src/recom_sinking.F90

@@ -92,7 +92,7 @@ subroutine recom_sinking_new(tr_num,mesh)
 #endif
     end if
 
-!! No sinking if background sinking velocity is less than 0.1 m/day
+!! Very low or no sinking if background sinking velocity is less than 0.1 m/day
 if (Vsink .gt. 0.1) then
 
    do n = 1,myDim_nod2D