The Pulicat, a distinctive shallow lagoon: Hypersalinity, thermodynamics and meromixis

Modelled and observed tendencies of temperature and salinity are investigated to assess the factors governing the heat and salt in the Pulicat lagoon, a hypersaline (>3.5%) lagoon along the south east coast of India. The salinity of the lagoon is extremely fluctuating, shifting regimes from fresh to hypersaline on seasonal scales. Examination of the spatio-temporal variability of the salinity of the lagoon shows certain regions of the lagoon remain hypersaline during most of the year. Hydrology and vertical solar heat fluxes constitute the major governing factors of the salt and heat of the lagoon respectively, while advection by hydrodynamics is important in specific regions during particular time of the year. Extremely high salinities higher than previously reported values, exceeding those during severe drought conditions were observed during this study period. A first account of meromixis with high heliothermic subsurface temperature and salinity during winter months November to February of different years in an embedded region of the lagoon is reported.

Automated summary

This study investigates the temperature and salinity trends in the Pulicat lagoon, highlighting the significant fluctuations in salinity and the influence of hydrology and solar heat fluxes. Extremely high salinities, exceeding values during severe drought conditions, were observed during the study period. Additionally, the occurrence of meromixis with high subsurface temperature and salinity during winter months in a specific region of the lagoon is reported.