Abstract
Modern observations have presented linkages between subsurface waters of the western Pacific warm pool and both El Niño/Southern Oscillation-related and extratropic-controlled upper-ocean stratification on interannual timescales. Moreover, studies have showed that such controls may operate on orbital cycles, although the details remain unclear. Here we present paired temperature and salinity reconstructions for the surface and thermocline waters in the central western Pacific warm pool over the past 360,000 years, as well as transit modeling results from an Earth system model. Our results show that variations in subsurface temperature and salinity in the western Pacific warm pool have consistently correlated with the shallow meridional overturning cell over the past four glacial-interglacial cycles, and they vary on eccentricity and precession cycles. The shallow meridional overturning cell regulates subsurface waters of the western Pacific warm pool by changing subtropical surface water density and thus equatorial upper-ocean stratification, acting as an El Niño/Southern Oscillation-like process in the precession band. Therefore, the western Pacific warm pool is critical in connecting the austral shallow meridional overturning cell to the Earth’s climate system on orbital timescales.
Highlights
Modern observations have presented linkages between subsurface waters of the western Pacific warm pool and both El Niño/Southern Oscillation-related and extratropic-controlled upper-ocean stratification on interannual timescales
Modern observations show that the thermocline depth of the western Pacific warm pool (WPWP) is closely associated with the El Niño/Southern Oscillation (ENSO) evolution[2] and large-scale changes in extratropical atmospheric circulation[1]
Multiple plankton tows have demonstrated that the apparent calcification depth of N. dutertrei is 130 m on average off Papua New Guinea[16] and 140–150 m in the eastern part of the WPWP within the upper thermocline[17]
Summary
Modern observations have presented linkages between subsurface waters of the western Pacific warm pool and both El Niño/Southern Oscillation-related and extratropic-controlled upper-ocean stratification on interannual timescales. The shallow meridional overturning cell regulates subsurface waters of the western Pacific warm pool by changing subtropical surface water density and equatorial upper-ocean stratification, acting as an El Niño/Southern Oscillation-like process in the precession band. Two precession-dominated subsurface seawater temperature (subT) records off southern Sumatra[11] and Mindanao Island[12] in the far western part of the WPWP were controlled by local monsoon-induced oceanic upwelling processes responding to local summer precessional insolation changes[11]. Another newly published subT record from the WEP showed a dominant half-precession cycle under bihemispheric influences[13]. Combined with our previously published sea surface temperature (SST) and salinity (SSS) records from the mixed-layer species Globigerinoides ruber[15], enabling further investigation of the orbital-scale upper ocean thermal/salinity structures of the WPWP and their linkage to the southern extratropical oceans and ENSO-like processes over the last four glacial–interglacial cycles
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