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\section*{The Arctic MURI}
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\noindent
{\bf PI: Prof. Henrik Schmidt, henrik@mit.edu}

\noindent
{\bf Sponsor: The Office of Naval Research}

\vspace{0.1in}
\noindent
The MURI project explores the feasibility of extracting useful
environmental information from underwater ambient noise. Unlike active
acoustics studies where synthetic sources are used to image or examine
environmental features, ambient noise from natural sources are the
focus in this project. For LAMSSâ€™s involvement, we are examining how
rapid changes to the Arctic Ice cover and underwater sound speed
profile (SSP) in recent decades are reflected in the underwater
ambient noise. Our work builds upon a wealth of previous studies in
the Beaufort Sea region that correlate changes in the ambient noise to
environmental stresses such wind, temperature, ocean current, and ice
cover properties. In addition, we bring unique new insights by
comparing ambient noise data from the region collected decades apart
to identify differences attributed to the changed environment.  With
our improved understanding of ambient noise, we hope to inform more
effective underwater communication and navigation strategies within
the dynamic Arctic environment.

\vspace{0.1in}
\begin{figure}[H]
  \centering 
  \includegraphics[width=0.85\textwidth]{figures/muri.pdf}
  \caption{Underwater noise vertical directionality profile (VDP) is
    one way we can quantify differences between the present and past
    ambient noise environments in the Arctic. The figure here shows
    the measured VDPs in 1994 (SIMI94) and 2016 (ICEX16) in
    blue. Notice the noise notch near 0 deg. elevation that has
    developed in 2016 compared to 1994. this feature is in part due to
    the changed SSP between the two times. Also shown are modeled VDPs
    generated with the assumption of a uniform surface source
    distribution in the ice cover, using the SSP of 1994 and 2016,
    respectively. By comparing of the measured and modeled VDPs in
    each case, we can see that the SIMI94 profiles match well but not
    the ICEX16 profiles. This result suggests that the uniform surface
    source distribution assumption may be valid for 1994 but is not
    descriptive of the ice cover in 2016.}
  \label{fig_icex}
\end{figure}
\vspace{0.1in}

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