Bottom water formation in the Weddell Sea resolved by principal component analysis and target estimation

The general mixing situation in the southern Weddell Sea is studied by principal components analysis (PCA). A method for computing the fractions of the assumed source waters in a given sample is presented. The method is applied to the formation of Antarctic Bottom Water in the southern part of the Weddell Sea. The algorithm is a combination of PCA and regression. The method can be used to compile the variation in a number of measured variables without limitations of the variable count. Previous oceanographic knowledge is combined with the score mixing patterns in order to estimate the number of source waters and their compositions. In the application described, the principle of this method is demonstrated with the variables temperature, salinity and oxygen. Three source waters were indicated by PCA and the fractions of the two source waters, ice shelf water and warm deep water were calculated.