The recent detection of a central Pacific type of El Niño has added a new dimension to the El Niño‐Southern Oscillation climatic puzzle. Sea surface salinity (SSS) observations collected during 1977–2008 in the tropical Pacific are used to contrast the three eastern Pacific (EP) (1982–1983, 1991–1992, 1997–1998) and seven central Pacific (CP) (1977–1978, 1986–1988, 1990–1991, 1992–1995, 2002–2003, 2004–2005, 2006–2007) types of El Niño events, as well as the six EP (1985–1986, 1988–1989, 1995–1996, 1999–2001, 2005–2006, 2007–2008) and two CP (1983–1984, 1998–1999) types of La Niña events. The EP El Niño events result in large (∼30° longitude) eastward displacements of the eastern edge of the low‐salinity warm pool waters in the equatorial band, a resulting well‐marked SSS freshening (∼−1) near the dateline, and a SSS increase (∼+1) below the mean position of the South Pacific Convergence Zone (SPCZ). The CP El Niño events are characterized by smaller (50%) eastward displacements of the eastern edge, a ∼15° longitude westward shift of the equatorial SSS freshening, and a comparatively reduced (∼50%) SSS increase in the SPCZ. A qualitative analysis indicates that changes in zonal currents and precipitation can account for the observed contrasted signature in SSS. Eastward current anomalies appear over most of the equatorial band during EP El Niño events. In contrast, there is a tendency for zonal current convergence slightly west of the dateline during CP El Niño events, consistent with the confinement of the warm/fresh pool in the western central equatorial basin, the related quasi‐inexistent northeastward migration of the SPCZ, and associated heavy precipitation regime.

Recent analyses of physical measurements show the existence of a central Pacific type of El Niño (CPEN) with a sea surface temperature warming pattern distinct from that of the “classical” eastern Pacific El Niño (EPEN). In this study, we analyze the surface chlorophyll signature of El Niño‐Southern Oscillation (ENSO), using monthly maps of satellite‐derived chlorophyll anomalies between September 1997 and December 2010. We identify five typical ENSO structures. The first structure describes the lonely 1997–1998 EPEN of the period, the second and third represent La Niña, the fourth illustrates intermediate conditions, and the fifth characterizes CPEN. During the 1997–1998 EPEN, a large eastward shift of the oligotrophic warm pool and a reduction of equatorial upwelling result in negative chlorophyll anomalies east of 170°E between 10°S and 10°N. During the four CPEN events, a reduced eastward shift yields negative chlorophyll anomalies in the equatorial band, within about 160°E and 160°W only. Westward surface current in the central basin limits the expansion of the anomaly core. Negative chlorophyll anomalies that extend eastward from the equatorial anomaly core probably result from reduced upward iron fluxes linked to the deepening of the Equatorial Undercurrent. During La Niña, the westward expansion of the equatorial upwelling results in positive chlorophyll anomalies west of the date line. Away from the equatorial band, advection of oligotrophic warm pool waters by enhanced eastward countercurrents drives negative anomalies within 8–10°N and toward the Marquesas Islands during CPEN, while reduced countercurrents lead to positive chlorophyll anomaly during La Niña.