Freshwater input into the coastal ocean and its relation on the salinity distribution off Austral Chile (35-54ºS)

around 48ºS.In this study, the relation of the terrestrial precipitation with the salinity off southern Chile (38-55ºS) is analyzed, particularly considering the remarkable salinity minimum (around 33.8 at 400 km offshore) found between 45 and 52ºS. Estimations of the amount of fresh water that enters into the coastal system were obtained from two independent methods. In the first one, the freshwater river input was taken from a hydrological balance published by the Chilean Dirección General de Aguas, using 30 years (1951-1980) of river flow data and a simple hydrological balance in the main and secondary river basins. In the second method, the amount of the freshwater was obtained from an independent study of precipitation in south Chile. The total freshwater river input for the study area was estimated to be 27000 m3/s while the estimated precipitation for the corresponding continental area is around 32000 m3/s. The fraction of freshwater in the marine system (Kf) was calculated using the method of Blanton and Atkinson (1983), using the salinity base data of Levitus 1994, with a spatial resolution of 1º of latitude and 1º of longitude. Salinity values at the surface and at 10, 20, 30 and 50 m depth were considered for the points closest to the coast. An annual mean and monthly distributions of Kf were obtained. The annual distribution has maximum values of Kf at 47, 50 and 52ºS, all greater than 0.6 m, and minimum values at 49ºS, of the order of 0.3 m. In the monthly distributions large values of Kf between 50-55ºS and between of 43-47ºS were observed. This zone of maximum Kf is separated by a zone of minimum Kf between 47-50ºS. Typical values of Kf are found between 0.2 and 0.8 m, except in March, when Kf greater than 1.5 m between 50 y 55ºS were observed. The curves of Kf versus latitude for the different depths considered are strongly correlated. The seasonal variations of Kf shows a peak in March for nearly all the latitudes considered, these values being even greater from 46ºS to the south. The maximum values are observed at 50ºS, 51ºS, and 52ºS. At 49ºS a minimum is observed in November. The latitudinal distributions of Kf are well correlated with the latitudinal distribution of freshwater input, particularly at the minimum of salinity around 50ºS and the relative maximum of salinity