The long-term goal of this project is to understand and mitigate the uncertainties of shallow water acoustic inversions caused by strong oceanic temporal and spatial variability. To achieve this goal, we need to investigate the connection between acoustic signal fluctuations and the water-column variability, and further incorporate this connection into the acoustic inversions for increasing the inversion performance. The scientific objectives of this project are centered on improving acoustic inversions for estimating bottom properties and source position in a randomly fluctuating shallow-water ocean. The first objective is to develop and test a new data nullspace projection method to suppress the inversion errors caused by the random water-column fluctuations. The second objective is focused on developing a source localization technique. The acoustic and oceanographic data collected from the SW06 experiment , a multi-disciplinary experiment sponsored by the ONR and conducted on the Mid- Atlantic Bight continental shelf in 2006, were used to test the developed technique and also to study how water column variability negatively affects source range estimates. In addition to the source localization work, the PI also developed an empirical orthogonal function (EOF) fitting method to merge different data to estimate the full water-column sound speed profiles in the SW06 experiment. The goal of this EOF fitting study is to provide a more complete oceanographic view of the local water-column variability to connect with the acoustic fluctuations seen in the data.