Mechanisms Involved in the Amplification of the Solar Cycle Signal... Pacific Ocean Stergios Misios

Mechanisms Involved in the Amplification of the Solar Cycle Signal in the Tropical
Pacific Ocean
Stergios Misios [[email protected]] and Hauke Schmidt, Max Planck Institute for
Meteorology, Hamburg, Germany
It is debated whether the response of the tropical Pacific Ocean to 11-year solar cycle forcing
resembles a La Niña- or El Niño-like signal. To address this issue, we conduct ensemble simulations
employing an atmospheric general circulation model with and without ocean coupling. In our
coupled simulations the tropically averaged sea surface temperature rises almost in phase with the 11year solar cycle. In the Pacific, a basin-wide warming of approximately 0.1 K is simulated whereas
the warming in the Indian and Atlantic oceans is weaker. Outside the Pacific the surface warming is
mainly caused by a water-vapor feedback. In the western Pacific, the region of deep convection shifts
to the east thus reducing the surface easterlies. This shift is independent of the ocean coupling; the
deep convection moves to the east in the uncoupled simulations, too. The reduced surface easterlies
cool the subsurface western Pacific but warm the surface. The surface warming is attributed to the
reduction of the heat transport divergence which operates together with the water-vapor feedback.
These results suggest that, firstly, the surface heating in the Pacific Ocean should be ascribed to a
synergetic effect of climate feedbacks and secondly, the atmospheric response to the 11-year solar
cycle drives the ocean. The latter implies that the Pacific response to the 11-year solar cycle does not
result from atmosphere-ocean feedbacks and thus the solar surface signature should stand out neither
as El Niño-like nor as La Niña-like.