Orbital and suborbital variability in the equatorial Indian Ocean as recorded in sediments of the Maldives Ridge (ODP Hole 716A) during the past 444 ka

Abstract

This study is aimed at understanding past 444 ka record of climate variability in the equatorial Indian Ocean using high resolution records of planktic and benthic foraminifera and pteropods from Ocean Drilling Program Hole 716A, Maldives Ridge, southeastern Arabian Sea. In total, 892 samples of 10 cm³ volume from 444 ka old sequence were analysed at 1 cm intervals to generate census data of the foraminiferal fauna and pteropods. The percent and detrended time series of mixed-layer species Globigerinoides ruber and Globigerinoides sacculifer and thermocline species Neogloboquadrina dutertrei, benthic foraminifera Cymbaloporetta squammosa, Sphaeroidina bulloides and Uvigerina proboscidea, and pteropods from ODP Hole 716A reveal significant changes in wind intensity during the past 444 ka. An abrupt decrease in the Cymbaloporetta squammosa population at c. 300 ka (across MIS 8/9) suggests a weakening of equatorial wind intensity, which could be linked to Indian monsoon and may have driven pronounced changes in the oxygen minimum zone in the Maldivian region. These changes were contemporaneous with the Mid-Brunhes Climatic Event, the beginning of aridity in the Indonesian-Australian region and the onset of a humid phase in equatorial East Africa as observed in several oceanic and continental records. This strengthens a connection between equatorial Indian Ocean wind intensity, the Indian monsoon and Indonesian-Australian-African climates.