Monsoon influence on planktic δ18O records from the South China Sea.

While the benthic δ 18 O records from many South China Sea sites mimic the SPECMAP/LR04 standard, their paired planktic δ 18 O 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 δ 18 O 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 δ 18 O records after derivation from the SPECMAP/LR04 standard, variations in the rain water δ 18 O affected by regional hydroclimate changes are considered to have played an important role. In contrast to the SPECMAP/LR04 standard δ 18 O curve prevailed by 100-kyr cycles, these regional planktic δ 18 O curves are distinguished by 20-kyr precession signal, showing partial similarity to the δ 18 O records of atmospheric oxygen in polar ice-core bubbles and in stalagmite calcite. We speculate that the common features of these three independent δ 18 O records are indicative of the effect of evolving hydrological cycling driven by monsoon circulation in low latitudes. [ABSTRACT FROM AUTHOR]