Computing the effect of sound on the marine environment by the adaptive mesh refinement method

Concern about the impact of sound on marine mammals has increased over the past decade causing regulatory agencies to take a more rigorous look at the potential impact of activities that introduce sound into the marine environment. Environmental Impact Statements (EIS's) must now be prepared to anticipate the impact of anthropogenic sound on marine mammals before engaging in underwater sound activities. In this paper we address the computational challenges of predicting the risk of non-physiological marine mammal harassments out to distant ranges. The maximum extent and step sizes of each dimension (range, depth and bearing) of the simulation space will have a significant impact on the amount of processing time required as well as the resulting accuracy. However, dynamic changes in the predicted sound pressure level as a function of depth and range combined with undulating bathymetry make it difficult to apply one simple grid structure at the outset of the simulation. Here, we investigate the current need for faster and more accurate calculations by applying the Adaptive Mesh Refinement (AMR) method to provide maximum accuracy in localized regions on an as-needed basis, and using sparser sampling in the larger regions of ocean where the sound field is relatively unchanged.