No, there is no provision (at least as at Emacs 24.5) for additionally continuing to look for and process ancestor
.dir-locals.el files after a nearer one has been located.
However, if it makes sense for your scenario, you can remove your "current directory" file and specify all the variables in the parent
Keys which are strings specify sub-directories; and the variables beneath that are set in addition to (or perhaps overriding) the ones in the top-level specifications.
(emacs) Directory Variables, which provides the following example:
((nil . ((indent-tabs-mode . t)
(fill-column . 80)))
(c-mode . ((c-file-style . "BSD")
(subdirs . nil)))
. ((nil . ((change-log-default-name
This sets ‘indent-tabs-mode’ and ‘fill-column’ for any file in the
directory tree, and the indentation style for any C source file. The
special ‘subdirs’ element is not a variable, but a special keyword which
indicates that the C mode settings are only to be applied in the current
directory, not in any subdirectories. Finally, it specifies a different
‘ChangeLog’ file name for any file in the ‘src/imported’ subdirectory.