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Linkage between Seasonal Insolation Gradient in the Tropical Northern Hemisphere and the Sea Surface Salinity of the Equatorial Indian Ocean during the Last Glacial Period
Author(s) -
RAJEEV Saraswat,
RAJIV Nigam,
ANDREAS Mackensen,
SYEE Weldeab
Publication year - 2012
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.1755-6724.2012.00746.x
Subject(s) - geology , interglacial , oceanography , climatology , monsoon , equator , northern hemisphere , glacial period , sea surface temperature , western hemisphere warm pool , holocene , latitude , paleontology , geodesy
Paired stable oxygen isotope and Mg/Ca analyses in calcite tests of the mixed‐layer‐dwelling planktic foraminifer Globigerinoides ruber has been used to reconstruct equatorial Indian Ocean δ 18 O of seawater (δ 18 O sw ) over the last ∼137 thousand years. On the basis of ice‐volume‐corrected δ 18 O sw (δ 18 O sw–ivc ), relative changes in sea surface salinity (SSS) have been estimated. The SSS estimates suggest three episodes of higher SSS (131–113 thousand years before present (kyr BP), 62–58 kyr BP, and 30–24 kyr BP) within the last glacial period as compared with the present. SSS comparison between interglacial episodes reveals that the surface seawater over the core site was significantly saltier during the penultimate interglacial than the Holocene. We suggest that the evolution of a seasonal insolation gradient between the Indian monsoon areas and the equator over the investigated time interval was instrumental in shaping the strength of the Indian winter and summer monsoons that left their imprints on the equatorial Indian Ocean SSS via freshwater input and wind‐induced mixing. The study shows that the insolation difference between northern latitudes and the equator during winter affects monsoon strength in the Indian region, especially during cold intervals.