What causes long-term temporal changes in the South Atlantic?

Two zonal sections at 11 degrees S in the South Atlantic, separated in time by 11 years, provide temperature differences in the deep ocean. The aim of this case study is to check whether intrinsic temperature changes are suff iciently large to identify long-term water mass property variations which c ould be related to climate change. Potential temperature differences on iso baric surfaces in the deep ocean here reach several tenths of degrees C. Th ey can be caused by vertical (cross-isopycnal) or horizontal (isopycnal) ad vection and mixing, or by intrinsic water mass changes. The effect of verti cal transport is removed by using neutral (density) surfaces. The effect of horizontal transport is determined by using a mixing parameterization for temperature and silica on neutral surfaces. The residual intrinsic temperat ure changes are, with a few local exceptions, within the range of the +/-0. 05 degrees C uncertainty, and the temperature changes can thus be explained by advection and mixing alone.