\renewcommand{\lineheight}{4cm}
{
    \color{BSCblue}\hspace{27cm}\Large\bf\textit{Mixed layer depth (MLD)}
}

\begin{minipage}[c][\lineheight][c]{0.17\textwidth}
    \begin{center}
        \includegraphics[height=3.2cm]{mld_argo.png}
    \end{center}
\end{minipage}
\begin{minipage}[c][\lineheight][c]{0.17\textwidth}
    \begin{center}
        \includegraphics[height=3.2cm]{mld_en4.png}
    \end{center}
\end{minipage}
\begin{minipage}[c][\lineheight][c]{0.17\textwidth}
    \begin{center}
        \includegraphics[height=3.2cm]{mld_vhr.png}
    \end{center}
\end{minipage}
\begin{minipage}[c][\lineheight][c]{0.17\textwidth}
    \begin{center}
        \includegraphics[height=3.2cm]{mld_hr.png}
    \end{center}
\end{minipage}
\begin{minipage}[c][\lineheight][c]{0.17\textwidth}
    \begin{center}
        \includegraphics[height=3.2cm]{mld_lr.png}
    \end{center}
\end{minipage}
\begin{minipage}[c][\lineheight][c]{0.04\textwidth}
    \begin{flushleft}
        \includegraphics[height=3.4cm]{mld_axes.png}
    \end{flushleft}
\end{minipage}
\hfill
\begin{minipage}[c][\lineheight][c]{6.5cm}
    \captionof{figure}{\color{BSCblue}\\\emph{MLD} time-average.}   
\end{minipage}