Halinе entropy flux into the Ocean due to spatial heterogeneity of the difference precipitation – evaporation

The formulas are proposed for estimating the haline component of entropy flux generated by uneven spatial distribution of evaporation, precipitation, and salinity at the ocean–atmosphere boundary. The entropy flux is calculated with 4о discretion on GODAS (Global Ocean Data Assimilation System) data for the meridian transect in the Pacific along 180о in 1984–2024 and its decadal variability is analyzed. The transect is separated to blocks with prevalence of evaporation (the salt flux into the ocean) and precipitation (the salt flux from the ocean). The fluxes of temperature, salinity, and mass are determined for each block and the haline component of entropy flux is estimated as ~ –5.10–5 W/m2K. This value does not exceed 1 % of the entropy flux caused by heat exchange between the ocean and atmosphere. However, this parameter is important for monitoring of the water exchange stability in conditions of changing climate. Increasing difference of the sea surface temperature is observed between blocks with opposite balance of evaporation and precipitation, but the tendency for the total entropy flux (due to heat and mass transfer) to increase presumably stabilizes spatial gradients of temperature and salinity on climate scale.

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