Title: Western Tropical Pacific as the Heat and Moisture Engine: from Late Quaternary to deeper and recent times

Authors: Haowen Dang¹, Zhimin Jian¹, Lijuan Sha², Yue Wang¹, Hai Cheng², Chen Li¹, Mahyar Mohtadi³, Yair Rosenthal⁴, Franck Bassinot⁵

Affiliations:
¹ State Key Laboratory of Marine Geology, Tongji University, Shanghai, China.
² Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an, China.
³ MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
⁴ Department of Marine and Coastal Science and Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ, USA.
⁵ Laboratoire des Sciences du Climat et de l’Environnement/IPSL, CEA-CNRS-UVSQ, University Paris-Saclay, Gif-sur-Yvette, France.

Abstract: The western tropical Pacific, often known as the West Pacific Warm Pool, plays a pivotal role as one major source of heat and moisture in the Earth surface system. By developing novel proxies of planktonic foraminifera, including Ocean Heat Content calculated from Mg/Ca thermometer and atmospheric humidity estimated by triple oxygen isotopes, we have revealed a coherent precession-dominated feature in the upper-Ocean Heat Content and moisture convergence over the Warm Pool during the Late Quaternary. Such results uncover that, under the orbital insolation forcing, the upper Ocean Heat Content of the Warm Pool waxes and wanes, thereby drives the moisture cycling from the oceanic evaporation sources to surrounding landmasses via meridional and zonal atmospheric circulations. A tight (thermo)dynamic connection from tropical oceanic heat budget to hydroclimatic cycling is therefore proposed, from the perspective of energetics, to propel a deeper understanding of the driving force of low-latitude processes in the global climate system. Our ongoing work with Plio-Pleistocene sediment records from ocean drilling and cold-water corals collected by deep diving are extending these findings from Late Quaternary to deeper and more recent times. In a warmer world like early Pleistocene and Pliocene, the obliquity-driven inter-latitudinal thermal contrast plays a central role in driving the thermal and hydroclimatic variations in the Warm Pool. Combining with the reconstructions of cold-water corals, it is implied that under the current global warming, a projected increase in the volume and heat-content of the Warm Pool would possibly trigger fundamental changes in the climate regime, therefore the Warm Pool, given its role of heat and moisture engine, serves as an underemphasized “tipping point” in the Earth’s future.

Biography: Dr. Dang started his paleoenvironmental studies since his undergraduate years at Peking University, and then threw himself into paleoceanography during his pursuing for Master’s and Doctorate degrees at Tongji University and working as a postdoc at LSCE in Gif-sur-Yvette, France. He mainly studies the paleo-reconstructions of the upper-ocean thermal structure and hydroclimate of the West Pacific Warm Pool, using geochemical proxies of foraminifera, sediment and cold-water corals, for the time intervals from the Pliocene, Quaternary to recent millennia. His research, published on Nature, Science Advances, EPSL, GRL, etc., have revealed several key findings such as the modulation effect of subsurface heat on Walker Cell since the Last Glacial Maximum, regulation of Warm Pool heat content on sea-land moisture transport, and the orbital-induced moisture convergence dynamics over the Warm Pool.