Monsoon influence on planktic δ18O records from the South China Sea

Abstract

While the benthic δ18O records from many South China Sea sites mimic the SPECMAP/LR04 standard, their paired planktic δ18O curves differ by comparable values at negative peaks corresponding to interstadials, especially between MIS 5.1, 5.3, 5.5, 6.5, and 7.3. Similar planktic δ18O records also occur in some other low-latitude oceans under monsoon influence. Because neither temperature nor salinity effects can fully account for the variations of such δ18O records after derivation from the SPECMAP/LR04 standard, variations in the rain water δ18O affected by regional hydroclimate changes are considered to have played an important role. In contrast to the SPECMAP/LR04 standard δ18O curve prevailed by 100-kyr cycles, these regional planktic δ18O curves are distinguished by 20-kyr precession signal, showing partial similarity to the δ18O records of atmospheric oxygen in polar ice-core bubbles and in stalagmite calcite. We speculate that the common features of these three independent δ18O records are indicative of the effect of evolving hydrological cycling driven by monsoon circulation in low latitudes.