Post-glacial evolution of the Indo-Pacific Warm Pool and El Niño-Southern oscillation

Recent research has revealed new insights into the temperature, size, and variability of the Indo-Pacific Warm Pool (IPWP) and the nature of the El Niño-Southern Oscillation (ENSO) since the Last Glacial Maximum (LGM). Sea surface temperature (SST) reconstructions from foraminiferal Mg/Ca, alkenone, and revised coral Sr/Ca palaeothermometry agree that SSTs in the IPWP during the LGM were B3 C cooler than at present. In the central portion of the IPWP, the rapid post-glacial rise in SST led the deglaciation by B3000 years to produce near-modern SSTs by the early Holocene. In contrast, further west and north, post-glacial shifts in SSTs in the South China and Sulu Seas are synchronous with abrupt climate changes in the North Atlantic. New evidence for the nature of the Little Ice Age in the tropics has been obtained from a 420-year record of coral Sr/Ca and dO from the Great Barrier Reef, Australia. This indicates that SSTs and salinity were higher in the 18th century than in the 20th century. The results suggest that the tropical Pacific played a role as a source region of water vapour during the global expansion of Little Ice Age glaciers. The onset of modern ENSO periodicities is identified by palaeo-ENSO records throughout the tropical Pacific region B5000 years ago, with an abrupt increase in ENSO magnitude B3000 years ago. Individual ENSO events recorded by corals reveal that the precipitation response to El Niño temperature anomalies was subdued in the mid-Holocene. The apparent non-linear onset of ENSO in the late Holocene appears to reflect abruptly enhanced interaction between the Southern Oscillation and the Pacific Intertropical Convergence Zone. Comparisons of precipitation variability recorded by Great Barrier Reef corals with ENSO indices for the last 350 years confirms that non-stationarity of ENSO teleconnections is a natural characteristic of modern climate. r 2003 Elsevier Ltd and INQUA. All rights reserved.