Early mid‐Holocene SST variability and surface‐ocean water balance in the southwest Pacific

Abstract

International audienceWe present early mid-Holocene records of Sr/Ca, δ¹⁸O and δ¹⁸O_sw from marine archives collected in Vanuatu: two Porites sp. corals (6.7-6.5 ka BP) and a Tridacna maxima giant clam (6.2-6.0 ka BP). Sr/Ca, δ¹⁸O, and δ¹⁸O_sw were used as proxies for sea surface temperature (SST) and sea surface salinity (SSS). The fossil geochemical records were compared to modern Porites sp. and T. maxima records. Reconstructed mean SSTs from the two fossil Porites sp. and from the modern coral are similar, implying that the Western Pacific Warm Pool (WPWP)' southern edge had reached its modern location by 6.7-6.5 ka BP. The post-glacial SST rise in the Southwest Pacific was thus completed by the early mid-Holocene. The two early mid-Holocene corals and the giant clam recorded saltier conditions than modern related to 1) a decoupling between the precipitation regime and the SPCZ due to a northerly position of this climatic feature and 2) an increase of the moisture transport to the extra-tropics, driven by a strengthened or extended Hadley cell. The longest δ¹⁸O coral profile displays an El Niño Southern Oscillation (ENSO) signal reduced by 20-30% compared to the period 1928-1992, in concordance with the reduced ENSO variability observed in the Pacific area during the first half of the Holocene. However, the decoupling between the SPCZ and the precipitation regime may have also contributed to the weak ENSO signal recorded in the early mid-Holocene coral δ¹⁸O profile

Cyclic changes of Asian monsoon intensity during the early mid-Holocene from annually-laminated stalagmites, central China

“…Subsequently, the hydrological/thermal conditions in the tropical ocean reached the modern level, and the postglacial SST rise in the Southwest Pacific was completed (6.7e6.5 ka BP, Duprey et al, 2012). Observational and coral studies showed that decadal AM variability was tightly linked to the ENSO activity (Charles et al, 1997;Kumar et al, 1999;Yim et al, 2008), possibly via the midlatitude-tropical atmospheric teleconnection (Wang et al, 2000).…”

Links between tropical Pacific seasonal, interannual and orbital variability during the Holocene

“…In the western Pacific (Fig. 2a), the records show a significant decrease in ENSO variance during the early and mid-Holocene 16,17,30,37 ; there are only a few records from the 6-2 kyBP interval but these also show reduced ENSO variance. A decrease in ENSO variance is present throughout the past 7ky in the CP (Fig.…”

“…We compare these data to an ensemble of nine state-of-the-art global climate models (GCMs) from the Paleoclimate Modeling Intercomparison Project (PMIP3 28 ), which include simulations of pre-industrial (piControl) as well as industrial era (historical) and MH (midHolocene) climate (Table S2). The datasets represent the most comprehensive collection of oxygen isotope measurements on Holocene corals 16,17,24,25,[29][30][31][32][33][34][35] and mollusks 26,[36][37][38] to date from the tropical Pa- Table S1 and Fig. S1).…”

Evaluation of annual resolution coral geochemical records as climate proxies in the Great Barrier Reef of Australia

“…To acquire seasonal to monthly climatic information, most studies sample coral skeletons at very high-resolution intervals (ca. 1 mm or less; e.g., McCulloch et al 1994;Alibert and McCulloch 1997;Gagan et al 1998;McCulloch et al 1999;Sun et al 2004;Wei et al 2007;Deng et al 2009;Duprey et al 2012;DeLong et al 2013). However, high-resolution sampling requires a considerable number of subsamples for analysis, which makes coral-based climate reconstructions time consuming, labor intensive, and expensive.…”