Glacial Indonesian Throughflow weakening across the Mid-Pleistocene Climatic Transition

Benjamin Petrick,Alexandra Auderset,David De Vleeschouwer,Hideko Takayanagi,Alfredo Martínez-García,Hanaa Deik,Yasufumi Iryu,Lars Reuning,Gerald Auer,Gerald H Haug

doi:10.1038/s41598-019-53382-0

Abstract

The Indonesian Throughflow (ITF) controls the oceanic flux of heat and salt between the Pacific and Indian Oceans and therewith plays an important role in modulating the meridional overturning circulation and low latitude hydrological cycle. Here, we report new sea surface temperature and aridity records from the west coast of Australia (IODP Site U1460), which allow us to assess the sensitivity of the eastern Indian Ocean to the major reorganization of Earth’s climate that occurred during the Mid-Pleistocene Transition. Our records indicate glacial coolings at 1.55 and 0.65 million years ago that are best explained by a weakening of the ITF as a consequence of global sea level and tectonic changes. These coincide with the development of pronounced gradients in the carbon isotope composition of the different ocean basins and with substantial changes in regional aridity, suggesting that the restrictions of the ITF influenced both the evolution of global ocean circulation and the development of the modern hydrological cycle in Western Australia.

Highlights

The Indonesian Throughflow (ITF) constitutes the main pathway for the exchange of water, heat and salt between the Pacific and Indian Oceans, and represents a key node in the return branch of the MOC12
The new data reported here indicates that that glacio-eustatic ITF restriction potentially coupled with tectonic changes caused a significant cooling in the Indian Ocean at 1.55 and 0.65 Ma
These changes coincide with the development of stronger interoceanic benthic δ13C gradients suggesting that the restriction of the ITF during the MPT influenced the evolution of global circulation at both 0.65 and 1.55 Ma

Summary

Introduction

The Indonesian Throughflow (ITF) constitutes the main pathway for the exchange of water, heat and salt between the Pacific and Indian Oceans, and represents a key node in the return branch of the MOC12. Most climate model simulations predict a decrease in the ITF transport in response to anthropogenic warming, but the impacts of these changes on the MOC and global climate remain unclear[15,16] In this context, the study of ITF dynamics and their impact on the eastern Indian Ocean (IO) during episodes of major climatic changes in the past can provide important insights on their sensitivity to different climate forcings. The recently drilled IODP Site U1460 (27°22.4867′S, 112°55.4265′E, 215 m water depth) is located in the eastern Indian Ocean, off of the west coast of Australia, at a location well suited to monitor changes in the strength of the LC and by extension the ITF in the past (Fig. 1). We report an X-Ray fluorescence (XRF)-derived Ti/Ca record from the same site that allows us to infer past aridity changes in the region, and to evaluate potential links between regional aridity and the strength of the ITF

Methods

Results

Conclusion