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Formation of the South Pacific Shallow Salinity Minimum: A Southern Ocean Pathway to the Tropical Pacific In the eastern South Pacific Ocean, at a depth of about 200 m, a salinity minimum is found. This minimum is associated with a particular water mass, the Shallow Salinity Minimum Water (SSMW). SSMW outcrops in a fresh tongue (S^sub min^) centered at about 45°S. The S^sub min^ appears to emanate from the eastern boundary, against the mean flow. The watermass transformation that creates SSMW and S^sub min^ is investigated here. The S^sub min^ and SSMW are transformed from saltier and warmer waters originating from the western South Pacific. The freshening and cooling occur when the water is advected eastward at the poleward side of the subtropical gyre. Sources of freshening and cooling are air-sea exchange and advection of water from south of the subtropical gyre. A freshwater and heat budget for the mixed layer reveals that both sources equally contribute to the watermass transformation in the mixed layer. The freshened and cooled mixed layer water is subducted into the gyre interior along the southern rim of the subtropical gyre. Subduction into the zonal flow restricts the transformation of interior properties to diffusion only. A simple advection/diffusion balance reveals diffusion coefficients of order 2000 m^sup 2^ s^sup -1^. The tongue shape of the S^sub min^ is explained from a dynamical viewpoint because no relation to a positive precipitation-evaporation balance was found. Freshest S^sub min^ values are found to coincide with slowest eastward mixed layer flow that accumulates the largest amounts of freshwater in the mixed layer and creates the fresh tongue at the sea surface. Although the SSMW is the densest and freshest mode of water subducted along the South American coast, the freshening and cooling in the South Pacific affect a whole range of densities (25.0-26.8 kg m^sup -3^). The transformed water turns northward with the gyre circulation and contr