5:15 PM - 6:45 PM
[U03-P09] Deglacial variability in surface-water pH in the South China Sea- The role of East Asian Monsoon
Keywords:Surface-water pH, Boron isotopes, Planktonic foraminifera, South China Sea, East Asian Monsoon
Understanding the interplay between ocean carbon chemistry and hydrological variability in the past can provide clues to better constrain the control mechanisms of the global carbon cycle. It is generally recognized that open ocean upwelling regions (i.e. Southern Ocean and Eastern Equatorial Pacific) are the primary CO2 sources during the last deglaciation. Despite the possible role as CO2 sources based on modern observations, marginal seas, however, has not received much attention due to their dynamic features.
Here we reconstruct the deglacial variability in surface ocean pH using the boron isotope composition (δ11B) of planktonic foraminifera (T. sacculifer) from the South China Sea (SCS), and utilize trace element ratios as indicators of deglacial hydrological changes. The results from two sediment cores in the eastern (MD97-2142, water depth 1557m) and the western SCS (MD05-2901, water depth 1454m) suggest that the SCS acted as a CO2 source throughout the last deglaciation, with stronger CO2 sources during the cold intervals (Heinrich stadial 1 and Younger Dryas), while weaker CO2 sources during the warm period (Bølling–Allerød and the Holocene). The deglacial oceanic pH variability in the SCS was most likely controlled by surface hydrological condition, which is mainly driven by East Asian Winter Monsoon. This implies that the monsoon-driven oceanic CO2 outgassing from marginal seas may also contribute to the atmospheric CO2 rise since the Last Glacial Maximum. More paleo-CO2 reconstructions from the marginal seas are clearly required to better understand their roles in regulating atmospheric CO2 in the past.
Here we reconstruct the deglacial variability in surface ocean pH using the boron isotope composition (δ11B) of planktonic foraminifera (T. sacculifer) from the South China Sea (SCS), and utilize trace element ratios as indicators of deglacial hydrological changes. The results from two sediment cores in the eastern (MD97-2142, water depth 1557m) and the western SCS (MD05-2901, water depth 1454m) suggest that the SCS acted as a CO2 source throughout the last deglaciation, with stronger CO2 sources during the cold intervals (Heinrich stadial 1 and Younger Dryas), while weaker CO2 sources during the warm period (Bølling–Allerød and the Holocene). The deglacial oceanic pH variability in the SCS was most likely controlled by surface hydrological condition, which is mainly driven by East Asian Winter Monsoon. This implies that the monsoon-driven oceanic CO2 outgassing from marginal seas may also contribute to the atmospheric CO2 rise since the Last Glacial Maximum. More paleo-CO2 reconstructions from the marginal seas are clearly required to better understand their roles in regulating atmospheric CO2 in the past.