(*)Avoid diagnostic seg fault in a 10km deep ocean

  It was noted in /issues/491 that the call to
initialize_regridding() for diagnostics gives a segmentation fault when the
maximum depth of the ocean is greater than 9250 m unless DIAG_COORD_DEF_Z is
explicitly set.  This commit fixes this problem by (1) adding an extra layer to
the bottom of the hard-coded WOA09 list of diagnostic depths when the ocean is
deeper than the 9250 m maximum depth in that file, and (2) changing the default
behavior for diagnostic grids to be be uniform when the maximum ocean depth is
deeper than 9250 m, for which WOA09 is no longer likely to be a convenient
choice.  With this change, MOM6 no longer has segmentation faults for the
configuration described in issues/491.  All solutions are bitwise identical, but
some z-space diagnostic grids will be modified in cases that previously had
segmentation faults.

src/ALE/MOM_regridding.F90

@@ -211,6 +211,8 @@ subroutine initialize_regridding(CS, GV, US, max_depth, param_file, mdl, coord_m
   real :: tmpReal  ! A temporary variable used in setting other variables [various]
   real :: P_Ref    ! The coordinate variable reference pression [R L2 T-2 ~> Pa]
   real :: maximum_depth ! The maximum depth of the ocean [m] (not in Z).
+  real :: dz_extra      ! The thickness of an added layer to append to the woa09_dz profile when
+                        ! maximum_depth is large [m] (not in Z).
   real :: adaptTimeRatio, adaptZoomCoeff ! Temporary variables for input parameters [nondim]
   real :: adaptBuoyCoeff, adaptAlpha     ! Temporary variables for input parameters [nondim]
   real :: adaptZoom  ! The thickness of the near-surface zooming region with the adaptive coordinate [H ~> m or kg m-2]
@@ -311,7 +313,7 @@ subroutine initialize_regridding(CS, GV, US, max_depth, param_file, mdl, coord_m
     param_name = create_coord_param(param_prefix, "DEF", param_suffix)
     coord_res_param = create_coord_param(param_prefix, "RES", param_suffix)
     string2 = 'UNIFORM'
-    if (maximum_depth>3000.) string2='WOA09' ! For convenience
+    if ((maximum_depth>3000.) .and. (maximum_depth<9250.)) string2='WOA09' ! For convenience
   endif
   call get_param(param_file, mdl, param_name, string, &
                  "Determines how to specify the coordinate "//&
@@ -458,20 +460,27 @@ subroutine initialize_regridding(CS, GV, US, max_depth, param_file, mdl, coord_m
     endif
   elseif (index(trim(string),'WOA09')==1) then
     if (len_trim(string)==5) then
-      tmpReal = 0. ; ke = 0
+      tmpReal = 0. ; ke = 0 ; dz_extra = 0.
       do while (tmpReal<maximum_depth)
         ke = ke + 1
+        if (ke > size(woa09_dz)) then
+          dz_extra = maximum_depth - tmpReal
+          exit
+        endif
         tmpReal = tmpReal + woa09_dz(ke)
       enddo
     elseif (index(trim(string),'WOA09:')==1) then
       if (len_trim(string)==6) call MOM_error(FATAL,trim(mdl)//', initialize_regridding: '// &
                  'Expected string of form "WOA09:N" but got "'//trim(string)//'".')
       ke = extract_integer(string(7:len_trim(string)),'',1)
+      if (ke>40 .or. ke<1) call MOM_error(FATAL,trim(mdl)//', initialize_regridding: '// &
+                   'For "WOA05:N" N must 0<N<41 but got "'//trim(string)//'".')
     endif
-    if (ke>40 .or. ke<1) call MOM_error(FATAL,trim(mdl)//', initialize_regridding: '// &
-                 'For "WOA05:N" N must 0<N<41 but got "'//trim(string)//'".')
     allocate(dz(ke))
-    dz(1:ke) = woa09_dz(1:ke)
+    do k=1,min(ke, size(woa09_dz))
+      dz(k) = woa09_dz(k)
+    enddo
+    if (ke > size(woa09_dz)) dz(ke) = dz_extra
   else
     call MOM_error(FATAL,trim(mdl)//", initialize_regridding: "// &
       "Unrecognized coordinate configuration"//trim(string))