Many studies have documented the trends in the latitudinal position and
strength of the midlatitude westerly jet in the Southern Hemisphere.
However, very little attention has been paid to the longitudinal
variations of these trends. Here, we specifically focus on the zonal
asymmetries in the southern jet trends between 1980-2018. Meteorological
reanalyses show a robust strengthening and an equatorward shift of the
annual-mean and springtime jet over the Pacific sector, in contrast to a
weaker strengthening and poleward shift over the Atlantic and Indian
Ocean sectors. The reanalysis trends fall within the ensemble spread for
historical climate model simulations, showing that climate models are
able to capture the observed trends. Climate model simulations indicate
that the differential movement of the jet is a manifestation of internal
variability and is not a forced response. Implications of these
asymmetries for other components of the climate system are discussed.