25ka B.P.以来黑潮流域古环境演化对高频全球变化事件的响应

本文利用黑潮流域主流轴上的两个柱状沉积物岩芯MD05-2908以及PC-1为研究材料，在AMS14C测年的基础上，利用高分辨率的有机地球化学分析记录结合浮游有孔虫氧、碳同位素，恢复并重建了过去25,000 cal a BP以来黑潮流域古海洋环境演化的历史。以及表层海水生产力以及物质输送状况的演化历史。通过利用Uk’37古海水温度以及盐度指标恢复重建了过去25,000 cal a BP以来海洋表层海水温度、盐度；通过机碳、氮含量以及同位素变化、长链正构烷烃以及正构烷醇等指标重建了过去7000a B.P.以来的陆源物质输入历史；通过长链不饱和烯酮含量以及有机碳同位素指标恢复了过去7000a B.P.以来海水表层生产力的历史。此外，通过基于以上各种指标的环境信息与区域以及全球其它气候记录进行对比研究以及不同环境指标的时间系列分析，探讨了该区表层环流系统以及生产力的演化对于全球气候变化的响应，揭示了不同尺度的短周期高频率全球变化事件在黑潮流域的具体作用过程和响应机制。通过这些研究取得了以下的主要认识： 基于有机地球化学指标的古气候环境记录与黑潮流域已有的研究成果有很好的对应关系，从我们高分辨率的有机地球化学记录中可以识别出全新世黑潮强弱变化的几次明显的事件；25000a B.P.以来黑潮流域的环境变化与全球环境变化有着很好的对应性，黑潮强弱演化总体趋势与全球气候背景演化相一致，黑潮对高频气候变化事件的记录与全球记录具有同步性，这种同步性尤其体现在末次冰消期以来的气候快速高频振荡以及全新世以来的气候突变事件上。 全球性的高频气候事件对黑潮主体本身及黑潮流域的相邻区域的大气和海洋环流都具有重要的控制作用，这种控制作用主要通过副高、ITCZ以及季风三种气候要素之间相互关联、彼此影响造成的。具体表现为：太阳辐射量的减少导致热力差异减小，这种相对减小弱化了热带西太平洋的对流活动，造成了西太平洋副热带高压长期偏南、偏东，ITCZ平均北界位置偏南，降雨带长时间集中在南部地区，增强的降雨量提高了风化剥蚀以及沉积物向海洋搬运的能力，陆源物质供应量增加；同时，辐射量以及热力差的减小又与加强的东亚冬季风相联系，增强的冬季风导致了近底层“雾状层”物质的向海传输，物质传输效率增高。这种物源供应以及搬运量的双重增加导致了冲绳海槽流域物质通量的增加。 基于有机地球化学指标的海洋表层生产力的变化与陆源物质供应量以及黑潮流的强弱变化存在着对应关系，通常情况增加的海洋表层生产力对应着高的陆源物质输入以及相对较弱的黑潮。这种变化与东亚夏季风的以及冬季风的强弱都有很好的一致性。陆源物质的输入增加了表层营养物质的含量，导致生产力的勃发；陆源物质的输入增加又对应着减少的太阳辐射量，偏南的ITCZ北界位置以及副热带高压，这些对应于减弱的东亚夏季风（增强的东亚冬季风）。 黑潮流域的高沉积速率事件对应于减弱的黑潮强度和增加的ENSO频度，这些事件与上述的副热带高压、ITCZ位移和强弱的变化相一致。黑潮流域过去25000a B.P.以来南北温度的差异有冰期加大而全新世减小的趋势，但这种冰期与全新世的差异很小，我们认为末次盛冰期的时候黑潮主流轴没有移出冲绳黑潮，只是由于强度的减弱受陆架水体的影响有所加大。 黑潮流域很好的记录到了包括数千年尺度的D/O旋回周期到大气——海洋系统内部振荡所致的PDO、NAO等数十年尺度的高频振荡，说明黑潮流域对过去全球及区域环境变化事件有很好的响应。黑潮流域各古海洋指标所记录周期上的一致性说明这些环境因子控制机理上具有的一致性，即大背景上受太阳活动所引起的辐射量变化控制，局部的高频快速气候波动又受到局域性的气候因素如海气相互作用的放大影响。

Intraseasonal variability of Indian Ocean sea surface temperature during boreal winter: Madden-Julian Oscillation versus submonthly forcing and processes

[ 1] Intraseasonal variability of Indian Ocean sea surface temperature (SST) during boreal winter is investigated by analyzing available data and a suite of solutions to an ocean general circulation model for 1998 - 2004. This period covers the QuikSCAT and Tropical Rainfall Measuring Mission (TRMM) observations. Impacts of the 30 - 90 day and 10 - 30 day atmospheric intraseasonal oscillations (ISOs) are examined separately, with the former dominated by the Madden-Julian Oscillation (MJO) and the latter dominated by convectively coupled Rossby and Kelvin waves. The maximum variation of intraseasonal SST occurs at 10 degrees S - 2 degrees S in the wintertime Intertropical Convergence Zone (ITCZ), where the mixed layer is thin and intraseasonal wind speed reaches its maximum. The observed maximum warming ( cooling) averaged over ( 60 degrees E - 85 degrees E, 10 degrees S - 3 degrees S) is 1.13 degrees C ( - 0.97 degrees C) for the period of interest, with a standard deviation of 0.39 degrees C in winter. This SST change is forced predominantly by the MJO. While the MJO causes a basin-wide cooling ( warming) in the ITCZ region, submonthly ISOs cause a more complex SST structure that propagates southwestward in the western-central basin and southeastward in the eastern ocean. On both the MJO and submonthly timescales, winds are the deterministic factor for the SST variability. Short-wave radiation generally plays a secondary role, and effects of precipitation are negligible. The dominant role of winds results roughly equally from wind speed and stress forcing. Wind speed affects SST by altering turbulent heat fluxes and entrainment cooling. Wind stress affects SST via several local and remote oceanic processes.

Mixed-layer water oscillations in tropical Pacific for ENSO cycle

The main modes of interannal variabilities of thermocline and sea surface wind stress in the tropical Pacific and their interactions are investigated, which show the following results. (1) The thermocline anomalies in the tropical Pacific have a zonal dipole pattern with 160 W as its axis and a meridional seesaw pattern with 6-8 degrees N as its transverse axis. The meridional oscillation has a phase lag of about 90 to the zonal oscillation, both oscillations get together to form the El Nino/La Nina cycle, which behaves as a mixed layer water oscillates anticlockwise within the tropical Pacific basin between equator and 12 degrees N. (2) There are two main patterns of wind stress anomalies in the tropical Pacific, of which the first component caused by trade wind anomaly is characterized by the zonal wind stress anomalies and its corresponding divergences field in the equatorial Pacific, and the abnormal cross- equatorial flow wind stress and its corresponding divergence field, which has a sign opposite to that of the equatorial region, in the off-equator of the tropical North Pacific, and the second component represents the wind stress anomalies and corresponding divergences caused by the ITCZ anomaly. (3) The trade winds anomaly plays a decisive role in the strength and phase transition of the ENSO cycle, which results in the sea level tilting, provides an initial potential energy to the mixed layer water oscillation, and causes the opposite thermocline displacement between the west side and east side of the equator and also between the equator and 12 degrees N of the North Pacific basin, therefore determines the amplitude and route for ENSO cycle. The ITCZ anomaly has some effects on the phase transition. (4) The thermal anomaly of the tropical western Pacific causes the wind stress anomaly and extends eastward along the equator accompanied with the mixed layer water oscillation in the equatorial Pacific, which causes the trade winds anomaly and produces the anomalous wind stress and the corresponding divergence in favor to conduce the oscillation, which in turn intensifies the oscillation. The coupled system of ocean-atmosphere interactions and the inertia gravity of the mixed layer water oscillation provide together a phase-switching mechanism and interannual memory for the ENSO cycle. In conclusion, the ENSO cycle essentially is an inertial oscillation of the mixed layer water induced by both the trade winds anomaly and the coupled ocean-atmosphere interaction in the tropical Pacific basin between the equator and 12 degrees N. When the force produced by the coupled ocean-atmosphere interaction is larger than or equal to the resistance caused by the mixed layer water oscillation, the oscillation will be stronger or maintain as it is, while when the force is less than the resistance, the oscillation will be weaker, even break.

东海内陆架泥质区EC2005孔沉积特征及古环境记录

本论文通过对东海内陆架浙闽沿岸泥质沉积带EC2005孔沉积物岩性、粒度、AMS14C测年、粘土矿物以及全岩矿物衍射分析、沉积物常微量元素和稀土元素分析、总碳氮以及有机碳氮分析、磁化率测试和综合研究，以EC2005孔岩芯记录为依据分析了研究区的沉积环境演化、海平面升降、浙闽沿岸流形成历史以及蕴含的古气候信息，探讨了陆源物质矿物、地球化学成分与粒度的关系。 EC2005孔岩芯自底部至41.00 m（17.3~13.1 ka BP）为末次冰消期以来的湖泊三角洲沉积序列，物质来源主要是来自湖盆流域物质的输入。随着海平面逐渐上升，海水自13.1 ka BP开始侵入研究区，自12.3 ka BP开始海水深度加大，沿岸流的地位开始显现，7.3 ka BP以来，形成了高海平面以来主要受沿岸流控制的浅海沉积。稀土元素结果显示，东海内陆架EC2005孔12.3~9.8 ka BP是以湖盆流域近源物质为主向长江物质为主转变的过渡阶段，自大约10~9.8 ka BP开始，由于海水深度的进一步加大、沿岸流作用进一步增强，长江物质对研究区的物质供给成为主导。海平面的升高以及沿岸流的形成是物质来源发生变化的重要原因。 东海内陆架泥质沉积物中全新世期间长达700 a（5.9~5.2 ka BP）的高分辨率细粒敏感组分资料揭示的东亚冬季风增强，与GRIP冰芯δ18O揭示的冷期具有良好的对应关系。5500 a BP前后东亚冬季风突然增强，与世界范围内的5500 a BP强降温事件非常一致。功率谱分析揭示出62 a和11 a的太阳活动周期以及与现代ENSO周期相似的6 a和5 a周期，因此，中全新世东亚冬季风演化可能是太阳活动以及古ENSO事件对全球气候系统的影响所致。 东海内陆架区对末次冰消期至早全新世气候回暖的记录与该时期世界性的广泛记录相一致，应该是轨道时间尺度上太阳辐射增强与ITCZ北移以及太阳活动变化综合影响的结果。东海内陆架浙-闽沿岸泥质带EC2005孔存在的4个百年时间尺度上快速沉积事件：12.3~12.1 ka BP、7.5~7.3 ka BP、5.9~5.2 ka BP和1.5~1.3 ka BP，与新仙女木事件、7.3 ka BP冷事件、第二新冰期（5.5 ka BP强降温事件）以及北大西洋1.4 ka BP浮冰事件均有良好的对应，世界范围内广泛存在的8.2 ka冷事件对本钻孔沉积也形成了一定影响。 EC2005孔磁化率变化受到多种因素的制约，如岩性粗细、早期成岩作用以及人类活动等的影响。近3.6 ka以来，磁化率的剧烈波动可能是由于人类活动影响造成的。东海内陆架EC2005孔TOC、TN和TOC/TN的大小主要受控于岩性变化。 此外，根据陆源物质粒度和矿物成分之间的关系，建立了陆源物质平均粒径与主要矿物成分含量大小的函数模型。地球化学成分与其所赋存单种矿物的相关性分析则进一步表明，陆源矿物种类和含量控制着地球化学成分及其含量，矿物种类和含量对地球化学成分的控制是决定性的，而粒度对元素（化学成分）的“控制”实际上是由于不同粒度的矿物组分不同而造成。