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Paired Measurements of Foraminiferal δ 18 O and Mg/Ca Ratios of Indian Monsoons Reconstructed from Holocene to Last Glacial Record
Author(s) -
MAHESH Badanal,
BANAKAR Virupaxa,
BURR George
Publication year - 2011
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.2011.00498.x
Subject(s) - holocene , last glacial maximum , glacial period , monsoon , foraminifera , geology , oceanography , sea surface temperature , climatology , salinity , globigerinoides , deglaciation , paleontology , benthic zone
The effect of seasonally reversing monsoons in the northern Indian Ocean is to impart significant changes in surface salinity (SS). Here, we report SS changes during the last 32 kyr in the Lakshadweep Sea (southeastern Arabian Sea) estimated from paired measurements of δ 18 O and sea surface temperature (SST) using Globigerinoides sacculifer , an upper mixed layer dwelling foraminifera. The heaviest δ 18 O G.sacculifer (–0.07±0.08‰) is recorded between 23 and 15 ka, which could be defined as the last glacial maximum (LGM). The δ 18 O G.sacculifer shift between the LGM and Holocene is 2.07‰. The SST shows an overall warming of 2°C from the LGM to Holocene (28°C to 30°C). However, coldest SSTs are observed prior to LGM, i.e., ∼27 ka. The SS was higher (∼38 psu) throughout most of the recorded last glacial period (32.5–15 ka). This high salinity together with generally lower SSTs suggests a period of sustained weaker summer or stronger winter monsoons. The deglacial warming is associated with rapid reorganization of monsoons and is reflected in decreased salinity to a modern level of ∼36.5 psu, within a period of ∼5 kyr. This indicates intensification of summer monsoons during cold to warm climate transition.