Vesimassan

Vesimassan is a term used in hydrology and oceanography to denote the total mass of water contained within a defined body or region. It is a scalar quantity that can be derived by integrating density over the volume of the region, M = ∫ ρ dV. In cases where the water has approximately uniform density, vesimassan approximates to M ≈ ρ V. Water density varies with temperature and salinity, with freshwater near 0 to 4 degrees Celsius having about 1000 kg per cubic meter, and seawater typically around 1025 kg/m^3 depending on salinity.

On a global scale, the mass of Earth’s oceans is about 1.35 × 10^21 kilograms. Vesimassan is therefore a useful concept for quantifying changes in ocean or lake water mass due to processes such as precipitation, evaporation, river inflows, ice melt, and groundwater exchange. Measurements combine hydrographic profiles of temperature and salinity with bathymetric data, and, for large-scale changes, satellite gravity missions (such as GRACE) that detect mass distribution and its temporal evolution.

Applications of vesimassan include climate and hydrological budget analyses, studies of ocean circulation, and assessments of sea level change. While related in everyday language to the idea of a “water mass” in oceanography, vesimassan emphasizes the actual mass contained in a region, whereas the term water mass in English is often used to describe a body of seawater with coherent density-salinity properties.

Etymology wise, vesimassan derives from Finnish vesi meaning water and massa meaning mass, reflecting its use in Finnish scientific literature as a translation of the broader concept of water mass.