(*)Offline tracer read bug fix

  Corrected bugs in the offline tracer code that were preventing it from
reproducing across processor counts (and perhaps working sensibly at all). All
answers and output in the MOM6-examples regression suite are bitwise identical.
Although answers with the offline tracer code will change because of the bug
fix, because of some bugs that were fixed in another recent commit, it was
previously impossible to have run the offline tracer cases at all.

src/tracer/MOM_offline_aux.F90

@@ -673,21 +673,23 @@ subroutine update_offline_from_files(G, GV, nk_input, mean_file, sum_file, snap_
     vhtr(:,:,:) = 0.0
     ! Time-summed fields
     call MOM_read_vector(sum_file, 'uhtr_sum', 'vhtr_sum', uhtr(:,:,1:nk_input), &
-                         vhtr(:,:,1:nk_input), G%Domain, timelevel=ridx_sum)
+                         vhtr(:,:,1:nk_input), G%Domain, timelevel=ridx_sum, &
+                         scale=GV%kg_m2_to_H)
     call MOM_read_data(snap_file, 'h_end', h_end(:,:,1:nk_input), G%Domain, &
                        timelevel=ridx_snap,position=CENTER)
     call MOM_read_data(mean_file, 'temp', temp_mean(:,:,1:nk_input), G%Domain, &
                        timelevel=ridx_sum,position=CENTER)
     call MOM_read_data(mean_file, 'salt', salt_mean(:,:,1:nk_input), G%Domain, &
                        timelevel=ridx_sum,position=CENTER)
-  endif
 
-  do j=js,je ; do i=is,ie
-    if (G%mask2dT(i,j)>0.) then
-      temp_mean(:,:,nk_input:nz) = temp_mean(i,j,nk_input)
-      salt_mean(:,:,nk_input:nz) = salt_mean(i,j,nk_input)
-    endif
-  enddo ; enddo
+    ! Fill temperature and salinity downward from the deepest input data.
+    do k=nk_input+1,nz ; do j=js,je ; do i=is,ie
+      if (G%mask2dT(i,j)>0.) then
+        temp_mean(i,j,k) = temp_mean(i,j,nk_input)
+        salt_mean(i,j,k) = salt_mean(i,j,nk_input)
+      endif
+    enddo ; enddo ; enddo
+  endif
 
   ! Check if reading vertical diffusivities or entrainment fluxes
   call MOM_read_data( mean_file, 'Kd_interface', Kd(:,:,1:nk_input+1), G%Domain, &