Stable isotope record, Mg/Ca ratios and sea surface reconstruction for sediment core MD06-3067

We present sea surface, upper thermocline, and benthic d18O data, as well as temperature and paleoproductivity proxy data, from the International Marine Global Change Study Program (IMAGES) Core MD06-3067 (6°31'N, 126°30'E, 1575 m water depth), located in the western equatorial Pacific Ocean within the flow path of the Mindanao Current. Our records reveal considerable glacial-interglacial and suborbital variability in the Mindanao Dome upwelling over the last 160 kyr. Dome activity generally intensified during glacial intervals resulting in cooler thermocline waters, whereas it substantially declined during interglacials, in particular in the early Holocene and early marine oxygen isotope stage (MIS) 5e, when upwelling waters did not reach the thermocline. During MIS 3 and MIS 2, enhanced surface productivity together with remarkably low SST and low upper ocean thermal contrast provide evidence for episodic glacial upwelling to the surface, whereas transient surface warming marks periodic collapses of the Mindanao Dome upwelling during Heinrich events. We attribute the high variability during MIS 3 and MIS 2 to changes in the El Niño Southern Oscillation state that affected boreal winter monsoonal winds and upper ocean circulation. Glacial upwelling intensified when a strong cyclonic gyre became established, whereas El Niño-like conditions during Heinrich events tended to suppress the cyclonic circulation, reducing Ekman transport. Thus, our findings demonstrate that variations in the Mindanao Dome upwelling are closely linked to the position and intensity of the tropical convection and also reflect far-field influences from the high latitudes.

本研究报道了采自西赤道太平洋棉兰老流（Mindanao Current）流经海域的国际海洋全球变化研究计划（International Marine Global Change Study Program, IMAGES）岩芯MD06-3067（北纬6°31′，东经126°30′，水深1575米）的海表、上层温跃层（upper thermocline）及底栖δ¹⁸O数据，同时涵盖温度与古生产力代用指标（paleoproductivity proxy）数据。本次岩芯记录揭示了过去16万年（kiloyear, kyr）以来，棉兰老穹顶上升流（Mindanao Dome upwelling）存在显著的冰期-间冰期（glacial-interglacial）及亚轨道尺度变化。冰期时段穹顶活动普遍增强，导致温跃层水体降温；而间冰期时段该活动则显著减弱，尤其在早全新世（early Holocene）及海洋同位素第5e亚阶段（Marine Isotope Stage, MIS 5e），此时上升流水体未能抵达温跃层。在海洋同位素阶段3（MIS 3）与阶段2（MIS 2）期间，升高的表层生产力（surface productivity）、显著偏低的海表温度（Sea Surface Temperature, SST）以及较弱的上层海洋热对比度（upper ocean thermal contrast），为冰期间歇性表层上升流提供了证据；而海因里希事件（Heinrich events）期间出现的短暂表层升温，则标志着棉兰老穹顶上升流的周期性崩溃。我们将海洋同位素阶段3与阶段2期间的高变异性，归因于厄尔尼诺-南方涛动（El Niño Southern Oscillation, ENSO）状态的变化——该变化影响了北半球冬季季风风场（boreal winter monsoonal winds）与上层海洋环流。当强盛的气旋式环流（cyclonic gyre）形成时，冰期上升流会增强；而海因里希事件期间的类厄尔尼诺状态则会抑制气旋式环流，削弱埃克曼输运（Ekman transport）。综上，本研究结果表明，棉兰老穹顶上升流的变化与热带对流（tropical convection）的位置及强度密切相关，同时也反映了高纬度（high latitudes）地区的远程影响。