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 delta 98/95 Mo 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 delta 98/95 Mo 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.

基于AMS14C年龄和底栖有孔虫氧同位素建立的地层年代框架,重点探讨了冲绳海槽中北部CSHC-15孔MIS6期以来(约200 ka)底栖有孔虫δ13C特征及其古海洋指示意义.结果显示,冰期-间冰期表层初级生产力和有机质通量的变化是导致底栖有孔虫δ13C值在MIS4和MIS6期负偏而在MIS1、MIS3和MIS5期正偏的主要原因.MIS2期的底栖有孔虫δ13C正偏,指示了 NPIW侵入冲绳海槽,导致通风性加强,底层水呈弱氧化状态.甲烷渗漏引发的甲烷厌氧氧化作用(AOM)是导致CSHC-15孔底栖有孔虫在MIS4期碳同位素大幅负偏的原因.

通过对东海外陆坡–冲绳海槽GSW1孔沉积物孔隙水δ13C、δ18O、δ11B、δ37Cl同位素和C1?、SO2-4、K+、Na+等离子指标的分析,探讨了沉积物早期成岩作用、流体来源、迁移和氧化环境的变化.研究发现,GSW1孔孔隙水溶解无机碳主要来自海水和有机质,SO2-4浓度随深度下降比较平缓,C1?浓度远低于海水,该孔表层沉积物中硫酸盐消耗主要由有机质硫酸盐还原作用(OSR)所控制,甲烷厌氧氧化作用(AOM)发生在4 m以下更深的层位.OSR产生的H2S向上扩散富集并被氧化,是导致GSW1孔110～360 cm处SO2-4浓度未明显下降的主要因素.孔隙水SO2-4浓度整体随着深度增加呈减小的趋势,表明GSW1孔沉积环境由氧化、次氧化环境逐渐转变为还原环境.δ11B、δ37C1值垂向变化波动较大,一方面受到早期成岩阶段有机质降解的影响,也可能与孔隙流体扩散以及沉积物/孔隙水相互作用有关.