Contributions of Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation to Global Ocean Heat Content Distribution (Invited Presentation)

Regional sea surface temperature (SST) mode variabilities, especially the La Niña–like Pacific Ocean
temperature pattern known as the negative phase of the interdecadal Pacific oscillation (IPO) and the associated heat redistribution within the ocean, are the leading mechanisms explaining the recent global
warming hiatus. Here version 1 of the Community Earth System Model (CESM) is used to examine how
different phases of two leading decadal time scale SST modes, namely the IPO and the Atlantic multidecadal
oscillation (AMO), contribute to heat redistribution in the global ocean in the absence of time-evolving
external forcings. The results show that both the IPO and AMO contribute a similar magnitude to global
mean surface temperature and ocean heat redistribution. Both modes contribute warmer surface temperature
and higher upper ocean heat content in their positive phase, and the reverse in their negative phase. Regionally, patterns of ocean heat distribution in the upper few hundred meters of the tropical and subtropical Pacific Ocean depend highly on the IPO phase via the IPO-associated changes in the subtropical cell. In the
Atlantic, ocean heat content is primarily associated with the state of the AMO. The interconnections between
the IPO, AMO, and global ocean heat distribution are established through the atmospheric bridge and the
Atlantic meridional overturning circulation. An in-phase variant of the IPO and AMO can lead to much
higher surface temperatures and heat content changes than an out-of-phase variation. This result suggests that
changes in the IPO and AMO are potentially capable of modulating externally forced SST and heat
content trends.