Modeling cumulative sound exposure along a seismic line to assess the risk of seismic research surveys on marine mammals in the Antarctic Treaty Area

• Main Authors: Breitzke, Monika, Bohlen, Thomas
• Format: Book Part
• Language: unknown
• Published: 2012
• Subjects: Antarctic; Eia; The Antarctic; Antarc*
• Online Access: https://epic.awi.de/id/eprint/22606/; http://www.springerlink.com/content/978-1-4419-7311-5#section=1024458&page=1&locus=19; https://hdl.handle.net/10013/epic.38776

Based on the Protocol for the Protection of the Antarctic Environment established in 1991 all activities south of 60°S are subject to an environmental impact assessment (EIA). This also applies to seismic research surveys, which have come into public and regulatory bodies’ focus due to their potential impact on marine mammals. To assess the potential risk of air-gun shots on marine mammals numerical modelling of sound propagation is essential tool. In advance of a seismic survey computed sound fields are used to derive critical exposure zone radii, within which certain hearing thresholds are exceeded. Up to now only ray tracing approaches, which take the geometry of an air-gun array and the signatures of its individual air guns into account, but neglect the sound velocity profile of the water column and the seafloor, are used in EIAs for sound propagation modelling of single shots. However, increasing demands to consider (i) effects resulting from a stratified water column, (ii) interactions with the seafloor and (iii) cumulative effects resulting from multiple shots fired a along seismic line accentuate the need to use full waveform methods. Therefore, here we summarize the results of a detailed 2.5D finite-difference (FD) modelling study (Breitzke and Bohlen 2010), which fulfills these requirements, approximates compact air-gun clusters deployed by R/V Polarstern in polar regions by ‘point source equivalents’ and simulates marine mammals as static receivers. It is a contribution to a strategic risk assessment study on the impact of seismic research surveys on marine mammals in the Antarctic Treaty Area (Boebel et al. 2009).