气候变化领域集成服务门户

Carbon stable isotopes (delta C-13) in modern seawater samples and planktic foraminifera Globigerina bulloides from core top and downcore sediments are used to estimate the distribution of delta C-13 of dissolved inorganic carbon (DIC) in the surface waters of the southwest Pacific in the modern, preindustrial (PI), and over the last 25 kyr. The predicted delta C-13 distribution in the modern (delta C-13(DIC)), PI (delta C-13(PI)), and late Holocene (from planktic foraminifera Globigerina bulloides [temperature corrected delta C-13(G. )bulloidesTC] from core tops) displays a broad peak at the subtropical front) and subantarctic surface waters due to the combination of high biological productivity and thermodynamic air-sea gas exchange of CO2 in this region. The estimated delta C-13(PI) values and measured delta C-13-(G.)(bulloidesTC)( )values from the core tops are higher than the modern values due to the Suess Effect. However, there is poor agreement between the delta C-13(PI) values and core top delta(13)C(G.)(bulloidesTC )values south of 40 degrees S as the back-calculation approach using chlorofluorocarbon-11 (CFC-11) method for removing the anthropogenic delta C-13 is not effective at these higher southern latitudes. The delta(13)C(G.)(bulloidesTC)( )from a latitudinal transect of cores in the southwest Pacific were compiled by region using a Monte Carlo approach to determine the long-term trends in delta C-13 over the last 25 kyr. Glacial subantarctic delta C-13(G.)bulloidesTC values are low, while subtropical delta C-13(G.)bulloidesTC are high. The peak in delta C-13-(G.)(bulloidesTC)( )values shifts south in the early Holocene. These latitudinal variations in delta(13)C(G.)(bulloidesTC)( )are linked to changes in ocean circulation, biological productivity (associated with the shifts in the subtropical front), and air-sea CO2 exchange, likely related to the structure and position of the Southern Hemisphere Westerly Wind in the South Pacific region.