Abstract
A new model for seawater scattering was developed, in which Gibbs function was used exclusively to derive the thermodynamic parameters that are associated with density fluctuation. Because Gibbs function was determined empirically from highly accurate measurements of a group of thermodynamic variables and is valid for S(A) up to 120 g kg(-1) (Deep-Sea Research I, 55, 1639, 2008), we expect the model is also valid over the extended range of salinity. The model agrees with the measurements by Morel (Cahiers Oceanographiques, 20, 157, 1968) with an average difference of -0.6% for S = 0 and 2.7% for S = 38.4. The scattering by seawater as predicted increases with salinity in a non-linear fashion, and linear extrapolation of scattering based on Morel's measurements would overestimate by up to 30%. The extrapolation of ZHH09 model (Optics Express, 17, 5698, 2009), which is valid for S(A) up to 40 g kg(-1), however, agrees with the prediction within +/- 2.5% over the entire range of salinity. Even though there are no measurements available for validation, the results suggested that the uncertainty is limited in using the newly developed model in estimating the scattering by seawater of high salinity.
Highlights
Light scattering by seawater is an inherent optical property of fundamental importance in oceanic optics
Gibbs function used in Eq (12) was empirically fitted against a group of thermodynamic data sets covering an extended range of temperature (−6 - 80°C) and salinity [10], while the thermodynamic parameters used in ZHH09 are fitted against the measurements of individual parameters directly
Data sets used in deriving Gibbs function and aw were diverse in order to cover a wider range of temperature and salinity, though they are related thermodynamically
Summary
Light scattering by seawater is an inherent optical property of fundamental importance in oceanic optics. Zhang et al [5] deduced thermodynamically the effect of sea salts on the scattering by seawater and found that scattering increases with salinity non-linearly. Their results agreed with Morel’s measurements within his experimental error of 2%. The developed Gibbs function, g(SA, Tc, p), where SA is the absolute salinity in g kg−1, Tc the temperature in Celsius, and p sea pressure in Pa, has an extended range of validity for 0 ≤ SA ≤ 120 g kg−1, −12 °C ≤ Tc ≤80 °C, and −0.1 Pa ≤ p ≤ 100 MPa. Since the thermodynamic parameters, ρ, βT, and aw as used in Eqs. The purposes of this study are to develop a light scattering model for seawater that is based on Gibbs function and to estimate the scattering for high salinity waters
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
