[ESAC Seminar] Yuanyuan Song

“Removing Rotational Heat Transport Reveals Distinct Recharge Pathways for Eastern- and Central-Pacific El Niño”

Eastern-Pacific (EP) and Central-Pacific (CP) El Niño redistribute ocean heat through distinct pathways, yet quantifying this redistribution remains difficult. The vertically integrated heat transport is dominated by a rotational, divergence-free circulation that leaves regional heat content unchanged, even as it overwhelms both directional components of the full transport vector. As a result, tests of the recharge–discharge paradigm have largely relied on warm water volume or depth-integrated transport as proxies. Here we apply a Helmholtz decomposition to the ENSO heat budget in the OCCA2 state estimate, isolating the divergent (effective) component of the transport. Without this decomposition, the Niño-3 and Niño-4 heat budgets show no significant correlation with either transport direction; after decomposition, correlations recover to 0.85–0.97. With the effective transport thus isolated, EP events exhibit a clear meridional recharge–discharge cycle, peaking roughly six months before the event and reversing within four months after. CP events, by contrast, are nearly three times weaker, temporally diffuse, and lack a coherent zonal convergence signal.

ESAC Early-Career Seminar Series —

A forum for students and postdocs to share recent research, hone presentation skills, and build community among peers, sponsored by the EAPS Student Advisory Committee. Open to current EAPS graduate and undergraduate students and postdocs. Typically hosted on Thursdays during the semester, including pizza lunch.

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