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South Asian summer monsoon variability during the last ~54 kyrs inferred from surface water salinity and river run off proxies

DRS at CSIR-National Institute of Oceanography

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Title South Asian summer monsoon variability during the last ~54 kyrs inferred from surface water salinity and river run off proxies
 
Creator Gebregiorgis, D.
Hathorne, E.C.
Sijinkumar, A.V.
Nath, B.N.
Nurnberg, D.
Frank, M.
 
Subject OCEANOGRAPHY AND LIMNOLOGY
GEOLOGY AND GEOPHYSICS
METEOROLOGY AND CLIMATOLOGY
PALAEO-STUDIES
PALAEO-STUDIES
 
Description The past variability of the South Asian Monsoon is mostly known from records of wind strength over the Arabian Sea while high-resolution paleorecords from regions of strong monsoon precipitation are still lacking. Here, we present records of past monsoon variability obtained from sediment core SK 168/GC-1, which was collected at the Alcock Seamount complex in the Andaman Sea. We utilize the ecological habitats of different planktic foraminiferal species to reconstruct freshwater-induced stratification based on paired Mg/Ca and delta18O analyses and to estimate seawater delta18O (delta18Osw). The difference between surface and thermocline temperatures (DELTA T) and delta18Osw (DELTA delta18Osw) is used to investigate changes in upper ocean stratification. Additionally, Ba/Ca in G. sacculifer tests is used as a direct proxy for riverine runoff and sea surface salinity (SSS) changes related to monsoon precipitation on land. Our DELTA delta18Osw time series reveals that upper ocean salinity stratification did not change significantly throughout the last glacial suggesting little influence of NH insolation changes. The strongest increase in temperature gradients between the mixed layer and the thermocline is recorded for the mid-Holocene and indicate the presence of a significantly shallower thermocline. In line with previous work, the delta18Osw and Ba/Ca records demonstrate that monsoon climate during the LGM was characterized by a significantly weaker southwest monsoon circulation and strongly reduced runoff. Based on our data the South Asian Summer Monsoon (SAM) over the Irrawaddyy strengthened gradually after the LGM beginning at ~18 ka. This is some 3 kyrs before an increase of the Ba/Ca record from the Arabian Sea and indicates that South Asian Monsoon climate dynamics are more complex than the simple N-S displacement of the ITCZ as generally described for other regions. Minimum delta18Osw values recorded during the mid-Holocene are in phase with Ba/Ca marking a stronger monsoon precipitation, which is consistent with model simulations
 
Date 2016-04-11T06:10:52Z
2016-04-11T06:10:52Z
2016
 
Type Journal Article
 
Identifier Quaternary Science Reviews, vol.138; 2016; 6-15
http://drs.nio.org/drs/handle/2264/4943
 
Language en
 
Rights An edited version of this paper was published by Elsevier. Copyright [2016] Elsevier
 
Publisher Elsevier