Responses of foraminiferal isotopic variations at ODP Site 1143 in the southern South China Sea to orbital forcing

Responses of foraminiferal isotopic variations at ODP Sit 1143 in the southern South China Sea to orbital forcing

The foraminiferal δ18O and δ13C records for the past 5 Ma at ODP Site 1143 reveal the linear responses of the Plio-Pleistocene climatic changes in the southern South China Sea to orbital forcing at the obliquity and precession bands. The phase of the δ18O variations with the orbital forcing is opposite to that of the δ13C, which may be caused by the frequent El Nino events from the equatorial Pacific. The amplification of the Northern Hemisphere Ice Sheet at ～3.3 Ma probably affected the development of the 100-ka climatic cycles. Its further spreading may spur the 100-ka climatic cycle to become the dominant cycle in the late Pleistocene. The 'MidPleistocene Transition' event has localized influence on the isotopic variations in the southern South China Sea. The foraminiferal δ13C records for the past 5 Ma at Site 1143 are highly coherent with the orbital forcing at the long eccentricity band, and lead the δ18O records at the shorter eccentricity band, highlighting the importance of the carbon cycle in the global climate change.

The foraminiferal δ 18O and δ 13C records for the past 5 Ma at ODP Site 1143 reveal the linear responses of the Plio-Pleistocene climatic changes in the southern South China Sea to orbital forcing at the obliquity and precession bands. The phase of the δ 18O variations with the orbital forcing is opposite to that of the δ 13C, which may be caused by the frequent El Ni?o events from the equatorial Pacific. The amplification of the Northern Hemisphere Ice Sheet at ?3.3 Ma probably affected the development of the 100-ka climatic cycles. Its further spreading may spur the 100-ka climatic cycle to become the dominant cycle in the late Pleistocene. The “Mid- Pleistocene Transition” event has localized influence on the isotopic variations in the southern South China Sea. The foraminiferal δ 13C records for the past 5 Ma at Site 1143 are highly coherent with the orbital forcing at the long eccentricity band, and lead the δ 18O records at the shorter eccentricity band, highlighting the importance of the carbon cycle in the global climate change.