Influence of Southern Ocean Intermediate Water on the nutrient distribution in the eastern equatorial Pacific on orbital timescales

摘要: The eastern equatorial Pacific (EEP) is one of the key areas for studying oceanic processes that control atmospheric CO2 concentrations. Southern-sourced water masses (SOIW) are thought to stimulate biological pump in EEP and hence contributed drawdown during glacial times. Orbital forcing combination with local feedback mechanisms assumed be main driver this mass advection. Newest studies, however, question capability SOIW primary productivity Marine Isotope Stage 2 (MIS2), as nutrients rather utilized Southern Ocean. Instead, nutrient-rich Glacial North Intermediate Waters (GNPIW) seem a major component upwelled enhance MIS2. We present changes over last 190 ka derived from surface-dwelling planktic foraminifera Globigerinoides ruber deep-dwelling Globorotaloides hexagonus (ODP Site 1240). δ13C gradient between surface sub-thermocline (Δδ13Crub-hex) has been used assess export production area. We compare variations nutrient (Δδ13Chex-SOIW) waters (~350 m) SOIW. Δδ13Chex-SOIW variability dominated by 100 kyr 23 cycles. This implies strong response orbital precession internal climate related ice volume. At times low difference concentrations delivered via differ substantially, thus indicating not providing sufficient EEP. scenario most prominent MIS2 MIS6. Following interpretation Max et al. (submitted) we speculate similar MIS2, were trapped Ocean also MIS6 leaving northward-advected nutrient-depleted. Similar MIS 2, assume greater contribution hence, influence GNPIW on A switch recorded terminations.