The role of coupled feedbacks in the decadal variability of the SH
eddy-driven jet
Abstract
Recent work has suggested that tropical Pacific decadal variability and
external forcings have had a comparable influence on the observed
changes in the Southern Hemisphere (SH) summertime eddy-driven jet over
the satellite era. Here we contrast the zonally asymmetric response of
the SH eddy-driven jet to tropical Pacific decadal variability using
ensembles of the Community Earth System Model version 1 (CESM1) in a
pacemaker framework, where sea surface temperatures (SSTA) in the
tropical Pacific are nudged to observations. In both coupled and
uncoupled experiments, the observed South Pacific jet intensification is
found in all seasons, indicating the tropical Pacific SST cooling
anomaly impacts the South Pacific jet mainly via direct atmospheric
processes. By contrast, only the coupled pacemaker reproduces the South
Atlantic-Indian jet poleward shift in the summertime, suggesting that
the air-sea coupling is essential in driving the teleconnections between
tropical Pacific SSTA and South Atlantic-Indian jet variations.