A multiproxy analysis of late MIS 6 to early MIS 5d OSP Site 161-975 sediments

A multiproxy analysis based on planktic foraminiferal abundances, derived SSTs, and stable planktic isotopes measurements together with alkenone abundances and Uk'37 SSTs was performed on late MIS 6 to early MIS 5d sediment recovered from Site 975 (ODP Leg 161) in the South Balearic Islands basin (Western Mediterranean) with emphasis on reconstructing the climate progression of the last interglacial period. A number of abrupt climate changes related to alternative influence of nutrient rich northern and oligotrophic southern water masses were revealed. Heinrich event 11 and cooling events C27, C26, C25, C24, C23, which have been previously described in the North Atlantic, were recognized. However, in comparison to the eastern North Atlantic mid-latitude region, events C27 and C26 at Site 975 seem to be significantly more pronounced. Together with evidence of a two-phase climate optimum with maximum SSTs reached during its later phase, this implies a close similarity in climate dynamics between the Western Mediterranean and the Nordic seas. We propose that postglacial effects in the Nordic seas had an influence on the western Mediterranean climate via atmospheric circulation and that these effects competed with the insolation force.本研究针对西地中海巴利阿里群岛南部盆地975站位（大洋钻探计划161航次，Ocean Drilling Program Leg 161, ODP Leg 161）获取的深海氧同位素阶段（Marine Isotope Stage, MIS）6晚期至5d早期沉积物，开展了多代理指标综合分析，涉及浮游有孔虫丰度、反演得到的海表温度（Sea Surface Temperature, SST）、浮游有孔虫稳定同位素测试数据、烯酮类化合物丰度以及基于Uk'37指标的海表温度，研究重点在于重建末次间冰期的气候演化历程。研究揭示了多起与富营养型北部水团及贫营养型南部水团交替影响相关的突发性气候突变事件，并识别出此前在北大西洋被报道过的海因里希事件11（Heinrich event 11）以及C27、C26、C25、C24、C23冷却事件。不过相较于北大西洋中纬度东部海域，975站位记录的C27与C26事件表现得更为突出。结合暖期存在两阶段气候最优期、且海表温度峰值出现于第二阶段的证据，本研究认为西地中海与挪威海（Nordic seas）的气候动力机制高度相似。我们提出，挪威海的冰消期效应可通过大气环流影响西地中海气候，且该效应与太阳辐射强迫存在竞争关系。