Through biological productivity and ocean-atmosphere CO2 exchange, North Pacific mid-depth ventilation has the potential to regulate regional climate over glacial timescales. Nevertheless, the subtropical Northwest Pacific currently lacks continuous long redox records that would enable us to evaluate this process. In this instance, we present δ98/95Mo and redox-sensitive trace element data derived from Okinawa Trough sediments to reconstruct redox conditions and assess their possible significance in regulating atmospheric CO2 in the subtropical Northwest Pacific over the last 200 k.y. Enhanced oxic conditions induced by a strengthened Kuroshio Current during Marine Isotope Stage (MIS) 1 suggest the presence of enhanced deep water ventilation and upwelling in the Okinawa Trough, which likely contributed to high atmospheric CO2 concentrations during interglacial periods. The Okinawa Trough may have been oxic and served as a regional net carbon sink during MIS2 and MIS6, due to glacial North Pacific Intermediate Water (GNPIW) and a weak Kuroshio Current. During interglacials, high productivity brought on by the stronger East Asian Summer Monsoon (EASM) leads to an increase in organic matter burial and oxygen consumption. This substantial positive excursion in δ98/95Mo values during MIS4 and early MIS3 can be linked to the anaerobic oxidation of methane (AOM) and the release of methane-rich fluids from methane hydrate decomposition. Our findings highlight potential links between higher upwelling, GNPIW expansion, and the underlying processes regulating the atmospheric CO2 budget in the subtropical North Pacific during the late Quaternary.

中文翻译：

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过去 200 k.y 中北太平洋中水和亚热带西北太平洋氧化还原条件相关变化的钼同位素证据


通过生物生产力和海洋-大气 CO2 交换，北太平洋中深度通风有可能调节冰川时间尺度上的区域气候。尽管如此，亚热带西北太平洋目前缺乏连续的长氧化还原记录，使我们能够评估这一过程。在这种情况下，我们提出了来自冲绳海槽沉积物的 δ98/95Mo 和氧化还原敏感微量元素数据，以重建氧化还原条件并评估它们在过去 200 k.y 中对调节亚热带西北太平洋大气 CO2 的可能意义。在海洋同位素阶段 （MIS） 1 期间，增强的黑潮引起的高氧条件表明冲绳海槽中存在增强的深水通风和上升流，这可能是导致间冰期大气 CO2 浓度高的原因。由于冰川北太平洋中间水 （GNPIW） 和较弱的黑潮，冲绳槽可能是含氧的，并在 MIS2 和 MIS6 期间充当区域净碳汇。在间冰期期间，更强的东亚夏季季风 （EASM） 带来的高生产力导致有机物埋藏和耗氧量增加。在 MIS4 和早期 MIS3 期间，δ98/95Mo 值的这种显著的正偏移可能与甲烷的厌氧氧化 （AOM） 和甲烷水合物分解中释放富含甲烷的流体有关。我们的研究结果强调了更高的上升流、GNPIW 扩张以及第四纪晚期亚热带北太平洋大气 CO2 收支调节潜在过程之间的潜在联系。