In recent decades, instrumental data recorded at the South African Weather Service station on Marion Island (46¿54'S and 37¿51'E) in the Southern Ocean shows that the local climate of this island has undergone significant changes since the 1960s, mostly in austral summer. These include a decrease in rainfall, an increase in nonrainy days, changes in wind speed and direction, and an increase in maximum and minimum local air temperature and in nearshore sea surface temperature. This study analyzes surface temperature, pressure, sea surface temperature, and rainfall recorded daily at Marion Island together with NCEP reanalyses to explore the mechanisms potentially associated with these changes. It is suggested that the changes to the local climate of Marion Island are linked to the well-documented shift in phase of the semiannual oscillation in the Southern Hemisphere after about 1980.