Impact of salinity on modeled transmission loss

Often ocean sound speed profiles are estimated using a temperature profile measured, for example, with an expendable bathythermograph (XBT) combined with a database value for salinity. The prevalence of this approach is due to the added expense and limited availability of sensors that can simultaneously measure both temperature and salinity profiles, for example conductivity-temperature-depth (CTD) probes. When predicting acoustic performance of a sonar system, using the sound speed profile based only on measured temperature is typically but not always sufficient. In this study in the Gulf of Maine, the standard approach is accurate in 92% of cases. The assessment of a profile’s adequacy is based on how well modeled transmission loss (TL) matches the TL modeled using the measured temperature and salinity profile from CTD. A potential improvement using database values based on oceanographic models rather than those from climatological averages is discussed.