Summary of Abstract Submission

Abstract Submission No. IO50-06-0029PresentationPoster

RECONSTRUCTION OF EQUATORIAL INDIAN OCEAN SURFACE CLIMATOLOGY OVER THE LAST 100 KYR FROM PAIRED MEASUREMENTS OF FORAMINIFERAL 18O AND MG/CA RATIOS

Mahesh B S*1, V K Banakar2

1 National Centre for Antarctic and Ocean Research, India
2 National Instittute of Oceanography, India

ABSTRACT :

A 5.62 m long gravity core (GCEq2) was retrieved at 2 29` N latitude and 78 E longitude on board R. V. A. A. Sidorenko Cruise 65 from a water depth of 3788 m in the Equatorial Indian Ocean (EIO). The chronology for the upper 1 m section of the core is derived by eight radiocarbon dates while for the next 1.4 m section derived by tuning 18OG.ruber to LR04 benthic 18O stack. The studied upper section (2.4 m) of the sediment core covers last 100 kyr time-period. Here, we report the surface climatology (sea surface - temperature and - salinity: SST and SS) changes for the last 100 kyr in the EIO estimated from paired measurements of 18O and Mg/Ca in surface dwelling foraminifera Globigerinoides ruber. The heaviest 18OG.ruber (-10.08) is recorded between 25 13.6 ka BP, which could be defined as the last glacial maximum (LGM). The 18OG.ruber shift between the LGM and Holocene is 1.46 . The SST shows an overall warming of 3C from the LGM to Holocene (25 C to 28 C) similar to that recorded in the western and eastern pacific SST records. The SS was higher (~37 psu) throughout most of the recorded last glacial period (74 14 ka BP) while lowest salinity (~36 psu) is recorded at around 90 ky BP. The rapid warming events recorded in the SST time-series, comparable to the D-O oscillations indicate the influence of northern hemisphere climate on EIO hydrography. The variation in SS time-series similar to the LR04 benthic stack and the Vostok temperature anomaly suggests the influence of southern hemisphere climate. The general trend of SST time-series, glacial-interglacial shift and beginning of deglaciation in the present SST time-series are comparable to eastern and western Pacific SST records. This suggests a common mechanism which influences the climate in EIO and the Pacific over glacial-interglacial time-scales, probably the El-Nino Southern Oscillation. The most likely pathway which transmits the Antarctic climate signatures to the Indian Ocean would be through the subantarctic mode water which spreads equatorward and upwells in the equatorial region influencing the surface hydrography of the EIO.