400 / 2024-09-16 11:30:54

Late Quaternary orbital variations through upper-ocean heat and atmosphere moisture of the western tropical Pacific: Low-latitude Forcing of climate cycles

Indo-Pacific Warm Pool,Upper-Ocean Heat,Moisture Dynamics,Orbital Forcing

The tropical oceans over western Pacific and eastern Indian possess the largest volume of warm water in the upper-ocean, known as the Indo-Pacific Warm Pool (IPWP), which plays as the heat and moisture engine in the global climate system. Sedimentary reconstructions of planktonic foraminiferal proxies, including Mg/Ca for sea surface and thermocline water temperatures and novel triple oxygen isotopes for air humidity, consistently reveal a precession-dominated insolation control on the upper-ocean heat content and atmospheric moisture convergence over the IPWP in the Late Quaternary. Such a feature is accordant with speleothem δ¹⁸O records over the monsoonal regions of South/East Asia and South America, as well as the W-E zonal thermal contrast across the equatorial Pacific, and can be explained by the dynamics of summer monsoon circulation and El Niño-Southern Oscillations. It is implied that, from the point of view of energetics, the tropical ocean-atmosphere system can be directly driven by orbital insolation change, representing a “Low-latitude Forcing” of the global climate cycles, other than the "High-latitude Forcing" characterized by ice-sheet waxing and waning.