The precession phase of the boreal summer monsoon as viewed from the eastern Mediterranean (ODP Site 968)
The precession phase of the boreal summer monsoon as viewed from the eastern Mediterranean (ODP Site 968)
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DOI：
10.1016/j.quascirev.2010.03.011
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发表时间：
2010-06
影响因子：
4
通讯作者：
M. Ziegler;E. Tuenter;L. Lourens
中科院分区：
文献类型：
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作者：
M. Ziegler;E. Tuenter;L. Lourens
东地中海上新世-更新世的天文时间尺度建立在腐泥层与北方半球夏季日照最大值的调谐上。一个3000年的岁差滞后已成为工具的调谐过程中的放射性碳测年显示，最年轻的腐泥，S1，在全新世早期的中点发生约3000年后的日照最大。时间滞后的起源仍然难以捉摸，但是，因为腐泥通常与最大的非洲季风强度和瞬态气候模拟结果表明，在相位行为的非洲季风相对于岁差强迫。在这里，我们提出了新的高分辨率记录散装沉积物地球化学和底栖有孔虫氧同位素ODP网站968在东地中海。我们发现，3000年的岁差时间滞后的腐泥中点是一致的（1）全球海洋同位素年代学，（2）最大（季风）降水条件在地中海地区和中国来自放射性测年洞穴记录，（3）最大大气甲烷浓度在南极冰芯。我们发现，时滞与岁差节奏的北大西洋冷事件的发生，系统地推迟了强北方夏季风强度的发作。我们的研究结果也可以解释非洲季风在过去300万年的非平稳行为，由于更频繁和更强烈的冷事件在晚更新世。
The astronomical timescale of the Eastern Mediterranean Plio–Pleistocene builds on tuning of sapropel layers to Northern Hemisphere summer insolation maxima. A 3000-year precession lag has become instrumental in the tuning procedure as radiocarbon dating revealed that the midpoint of the youngest sapropel, S1, in the early Holocene occurred approximately 3000 years after the insolation maximum. The origin of the time lag remains elusive, however, because sapropels are generally linked to maximum African monsoon intensities and transient climate modeling results indicate an in-phase behavior of the African monsoon relative to precession forcing. Here we present new high-resolution records of bulk sediment geochemistry and benthic foraminiferal oxygen isotopes from ODP Site 968 in the Eastern Mediterranean. We show that the 3000-year precession time lag of the sapropel midpoints is consistent with (1) the global marine isotope chronology, (2) maximum (monsoonal) precipitation conditions in the Mediterranean region and China derived from radiometrically dated speleothem records, and (3) maximum atmospheric methane concentrations in Antarctica ice cores. We show that the time lag relates to the occurrence of precession-paced North Atlantic cold events, which systematically delayed the onset of strong boreal summer monsoon intensity. Our findings may also explain a non-stationary behavior of the African monsoon over the past 3 million years due to more frequent and intensive cold events in the Late Pleistocene.