Absence of propagating upper ocean heat content anomalies in the eastern tropical South Pacific after ENSO events

Abstract

In order to explore why after a mature ENSO warm phase (MEWP), upper ocean heat content (OHC) anomalies disappear in the eastern tropical South Pacific (ETSP: 10°S-20°S, 140-W-100°W), relationships with sea surface temperature (SST), sea level pressure (SLP), wind-stress curl (WSC) and latent heat flux (LHF), are investigated. After a MEWP, positive SST anomalies in the ETSP are first associated with overlying negative SLP anomalies through enhanced atmospheric convection and atmospheric hydrostatic processes. Then negative SLP anomalies and surface winds, lead to positive WSC and negative LHF anomalies (i.e., oceanic heat loss) which dominate the region. The above mechanisms, combined with a weakened South Equatorial Current, contribute to a rapid decay of positive OHC anomalies. It is exactly the opposite of what has been observed in the western tropical North Pacific, where in contrast OHC anomalies associated with ENSO, do grow with time and propagate. Copyright 2008 by the American Geophysical Union.