  Observations of planets throughout our Solar System have revealed that the
Earth is not alone in possessing natural, inter-annual atmospheric cycles. The
equatorial middle atmospheres of the Earth, Jupiter and Saturn all exhibit a
remarkably similar phenomenon - a vertical, cyclic pattern of alternating
temperatures and zonal (east-west) wind regimes that propagate slowly downwards
with a well-defined multi-Earth-year period. Earth's Quasi-Biennial Oscillation
(QBO, observed in the lower stratospheres with an average period of 28 months)
is one of the most regular, repeatable cycles exhibited by our climate system,
and yet recent work has shown that this regularity can be disrupted by events
occurring far away from the equatorial region, an example of a phenomenon known
as atmospheric teleconnection. Here we reveal that Saturn's equatorial
Quasi-Periodic Oscillation (QPO, with a ~15-year period) can also be
dramatically perturbed. An intense springtime storm erupted at Saturn's
northern mid-latitudes in December 2010, spawning a gigantic hot vortex in the
stratosphere at $40^\circ$N that persisted for 3 years. Far from the storm, the
Cassini temperature measurements showed a dramatic $\sim10$-K cooling in the
0.5-5 mbar range across the entire equatorial region, disrupting the regular
QPO pattern and significantly altering the middle-atmospheric wind structure,
suggesting an injection of westward momentum into the equatorial wind system
from waves generated by the northern storm. Hence, as on Earth, meteorological
activity at mid-latitudes can have a profound effect on the regular atmospheric
cycles in the tropics, demonstrating that waves can provide horizontal
teleconnections between the phenomena shaping the middle atmospheres of giant
planets.
