watermassatracering

Watermassatracering is a method in hydrology and oceanography for identifying and following water masses through time by using tracer signatures. The central goal is to determine the origin, transport pathways, mixing, and residence times of water parcels within larger bodies of water, such as seas, oceans, rivers, or estuaries.

Tracers used in watermassatracering include physical properties like temperature and salinity, as well as chemical and isotopic indicators such as stable isotopes (oxygen-18, deuterium), dissolved nutrients, dissolved inorganic carbon, and anthropogenic tracers like CFCs, tritium, and SF6. Dye-release experiments may also be used in controlled settings. Data are collected through shipborne sampling, moored sensors, autonomous vehicles, and remote sensing proxies, and are analyzed with Lagrangian or Eulerian frameworks and with mixing models to infer water mass origins and pathways.

Applications include reconstructing ocean circulation patterns, tracing riverine freshwater inputs, monitoring ventilation and stratification, assessing pollutant dispersion, and informing climate studies that require histories of water mass modification.

Limitations include non-uniqueness of tracer interpretations, rapid mixing that erases signatures, tracer decay or uptake, and the need for multi-tracer calibration and historical baseline data. Spatial and temporal gaps in data can complicate inferences, and local processes such as estuarine circulation can dominate signals at small scales.

Watermassatracering complements traditional water mass analyses that rely on temperature-salinity coordinates by adding multiple tracers to resolve ambiguous histories of water parcels.