2万年来热带温度变化：调节半球间的气候变化

２万年来热带温度变化：调节半球间的气候变化Ｔ．Ｐ．Ｇｕｉｌｄｅｒｓｏｎ等世界范围内因ＣＯ＿２含量倍增引起的全球温度变化估计为１°－４℃，这与热带海洋表面温度（ＳＳＴｓ）的变化非常相似。相似的热带ＳＳＴｓ变化范围（＋１°－＋３℃）显然取决于全球循环模型...     

Heinrich事件研究及其意义

近年来对末次冰期气候变化的详细研究发现了一些很难用米兰科维奇地球轨道理论解释的气修变冷事件,Ｈｅｉｎｒｉｃｈ事件就是其中之一。通过Ｈｅｉｎｉｒｉｃｈ事件这种短期气候的快速变化的广泛研究,对于认识短周期的气候的变化和人类生存环境均有重要意义。     

末次冰期以来南海东北部陆源有机碳埋藏通量演变:海平面和季风驱动

大陆边缘盆地是大陆风化剥蚀产物的主要沉积汇,其中有机碳的埋藏通量及其控制机制的研究对于理解全球碳循环具有重要科学意义。本研究基于南海东北部台西南盆地TWS-1岩芯的AMS14C测年、总有机碳、总氮含量和稳定碳同位素组成的分析,探讨了末次盛冰期23ka BP以来南海东北部陆源有机碳的来源、历史和影响机制。与潜在物源端元对比表明,台湾是研究站位沉积物陆源有机碳的主要物源,相对海源其贡献比例约为58%,陆源物质可能主要通过海底峡谷水道和低海平面时期陆架河流输入。重建的陆源有机碳通量在末次冰消期早期(19—13kaBP)和中全新世(7—4ka BP)期间有两个峰值,分别约0.16g/(cm2·ka)和0.09g/(cm2·ka)。综合分析表明,二者分别受控于冰期低海平面时期增强的陆架风化剥蚀和全新世季风强盛期降水驱动的古台湾岛剥蚀。我们的工作表明冰期-间冰期循环中海平面和季风分别驱动的大陆边缘有机碳埋藏可能对全球碳循环和大气CO2浓度演变有重要影响。     

古老的珊瑚与海平面

众所周知,末次冰期最盛期结束后(大约2万年前),世界大洋的海平面上升了150多米。在大约13万年前的前一个问冰期,大体上类似的情况也发生过。融化过程进行得不均匀,在总的背景下的南极洲和北冰洋都可以划分出巨大冰山的快速脱离幕。     

异地性介形虫堆积速率与古气候变化的相关性——以南海17940-2柱状样为例

17940－2柱状样采自南海北部陆坡、东洋群岛东南水深1727m处，柱长1330cm。通过分析该柱4万年以来的介形虫化石群落，发现异地性浅水分子的堆积速率在末次冰期和气候转变期时明显呈现高值，而在相邻的两个转变期之间则偏低，尤其在冰后期气候平趋的整个全新世，异地性分子的堆积速率降到最低。这一变化与该孔中有机碳通量的变化趋势相一致，但与原地性介形虫堆积速率的变化截然不同。以上结果说明在古气候变化时期该海域陆坡表层沉积物的顺坡搬运作用明显增强，推测是因海平面变动激发所在站位上方浊流所至。本研究结果说明，异地性介形虫的堆积速率可能成为古气候变化的敏感信号。     

红海的碳化学研究

目的是对红海的碳酸盐及其相关的化学做一初步的研究。滴定减度、总二氧化碳量及表观氧消耗量等的垂直剖面图皆和红海深水的流动型式相符合,而由滴定碱度的垂直剖面图可看出红海的碳酸钙似乎有沉淀现象。计算红海方解石和霰石饱和度的结果显示红海全水柱都是处于过饱和状态,而且红海深水的饱和度比印度洋西北部深水的饱和度高。     

末次冰期以来巽他陆架的演变及其对南沙群岛海区古环境的影响

通过对南沙群岛海区NS94－93柱样磁组构，矿物成分分析，结合^14C测年，分析了末次冰盛期巽他陆架出露成陆及其后巽他陆架被海水淹没后南沙群岛海区沉积环境的变化，认为巽他陆架在13.2kaB.P。时开始被海水淹没，约经历600a左右趋于稳定，在末次冰期，南沙群岛海区水体封闭，沉积物以陆源物质为主，碳酸盐含量低，13.2-10kaB.P，沉积物以陆源物质为主，碳酸盐含量逐渐增加，至10kaB.P.南沙群岛海区进入全新世，水体交换条件得到较大改善，沉积物中生源物质显著上升，陆源物质明显减少，碳酸盐含量一直维持在较高水平。     

冲绳海槽末次冰期以来千年尺度古海洋演化的沉积记录

格陵兰冰芯的δ18O记录表明，末次冰期的气候发生了一系列快速的冷暖交替过程，即所谓的Dansgaard-Oeschgerk旋回(Dansgaard et al.,1995；Stuiver et al.,1995；Grootes et al.,1997)。在北大西洋区域，海洋的沉积记录也清楚地再现了在总的冰期背景下代表强烈冰川漂移事件的6次变冷事件,即所谓的Heinrich事件(Bond et al.,1992，1993；Rasmussen et al.,1997；Andrews,1998)。通过对比发现Dansgaand-Oeschger旋回和Heinrich事件并非两个孤立的气候演变过程,Heinrich事件(H)发生在Dansgaard Oeshger旋回的最冷期，几次大的Heinrich事件使格陵兰的大气温度在冰期的气候条件下又降低3-6℃(Mayewski et al.，1997)。随后，越来越多的研究成果表明，这些气候事件的发生，尤其冷事件并不仅限于格陵兰和北大西洋等北半球的高纬度地区，几乎在全球各大区域均找到了它们的印记。 冲绳海槽作为西太平洋的一个弧后盆地，其较高的沉积速率和对全球气候变化的“放大效应”，为我们识别过去地质历史时期气候演化事件并进行全球对比提供了可靠的保证。本文作者对取自冲绳海槽北部的CSH1孔的孢粉组合和中部DGKS9603孔的浮游有孔虫动物群进行了分析，以期获得有关北半球高纬度地区记录的末次冰期气候突变事件具有全球意义的新证据。     

末次冰期以来西太平洋暖池变化的浮游有孔虫记录

探讨了末次冰期以来西太平洋暖池区浮游有孔虫动物群变化对环境和全球气候变化的响应。对取自西太平洋暖池核心区WP92-5柱样中的浮游有孔虫及其壳体δ^18O的分析结果表明,西太平洋暖池末次冰期的冬季表层水温比全新世低2℃以上;浮游有孔虫Neogloboquadrina pachyderma的含量变化与Globigerinoides sacculifer的δ^18O值呈明显相关,各时段的峰值可能与YD事件和Heinrich事件H1、H2和H3大致对应,分别出现在21—29、38—46、64—72和106—117cm,^14C年龄约为9．7—11．1、12．8—14．7、19—20．9和26．2—27．4ka B．P．;浮游有孔虫N．pachyderma的含量与G．sacculifer的δ^18O在各峰值之间含有数个频次不等的亚级变化,反映了末次冰期以来西太平洋暖池区气候的短尺度快速变化特征。     

南黄海HY126YA1孔末次冰期多层泥炭的发现及其古气候意义

南黄海ＨＹ１２６ＹＡ１孔是国家１２６专项０３项目下设的“黄海、东海浅钻调查”课题的指定钻孔之一,目的是通过这一钻孔的研究揭示南黄海第四纪古环境特征。该钻孔由上海海洋地质调查局一海大队和国土资源部海洋地质研究所共同实施。１９９８年７月完成海上钻探施工,同年１２月完成室内编录。钻孔位于黄海海槽的边部,地理坐标为３６°２２′４９″Ｎ,１２３°２８′７６″Ｅ,水深７７．６０ｍ,获取岩心总长６０．０１ｍ。     

我国海平面上升研究进展及前瞻

从原因、趋势、影响、对策4个方面对我国海平面上升的研究进行回顾和总结,指出了研究中存在的问题,并在此基础上,探讨了我国该区域未来的研究趋向。     

The tectonic style of the northern Red Sea

Multichannel seismic reflection profiles recorded in the northern Red Sea show structures that we interpret to be a result of the intrusion of uppermost Miocene salt. We believe that the evaporites are underlaid by attenuated continental crust and the flow of salt is due to renewed faulting of basement in the Pliocene when sea floor spreading began between latitudes 21°N and 15°30°N.     

The density of Red Sea brines

The densities of artificial and real Red Sea brines have been measured at 25°C with a vibrating tube densimeter. Measurements were also made on mixtures of Red Sea brines with seawater and pure water. The results have been used to characterize the density—composition relations of waters across the interface of brine and average Red Sea waters. The results for the real and artificial brines are in reasonable agreement.The composition of the brines and mixtures with seawater have been characterized by conductivity measurements of weight diluted samples. The conductivity salinities were found to be conservative to within $\text{±0.07‰}$ for the mixtures.The densities of brines and mixtures of brines and seawater were estimated from apparent molal volume data using Young's rule. The calculated densities for all of the solutions were found to be in good agreement with the measured values, demonstrating the applicability of Young's rule to concentrated natural waters.     

Near bottom magnetic profile across the Red Sea

Results are presented from a high precision geophysical profile made at an altitude of about 100 m above the sea floor with the Deep Two instrument package, crossing the Red Sea at 17°30N. The emphasis is on the analysis and interpretation of the magnetic field, including an inversion which removes the distortions due to bathymetry and the orientation with respect to the earth's main field vector. The spreading rates are determined precisely and found to be highly asymmetric: only 5 mm yr^-1 to the east and up to 10 mm yr^-1 to the west. We conclude that the axis of spreading is located on a volcanic ridge, rather than on the axial graben, based on the presence of a zone of high magnetization. The magnetization high (40 Am^-1) is about twice as great as found on the Mid-Atlantic Ridge with the same instrument and analysis. The quality of the recording of the magnetic anomalies in the oceanic crust is much greater than expected for such a low spreading rate.     

Molluscan Hard-Substrate Associations in the Northern Red Sea

Abstract. The mollusc associations of 29 hard-substrate localities in the Northern Bay of Safaga Red Sea, Egypt were studied. The hard substrates were classified into 7 types: reef flats, intertidal rock bottom, very shallow subtidal conglomerate, Porites carpet, faviid carpet, platy scleractinian association, Sarcophyton carpet. Based on a cluster analysis the molluscs of these hard substrates can be classified into 5 groups: Group A is dominated by Dendropoma maxima , Chamoidea and Tridacna maxima , group B by Pedum spondyloideum, T. maxima and Coralliophila neritoidea , group C by Chamoidea and Cerithium rüppelli , group D by Modiolus auriculatus , Chamoidea, Morula granulata and Nerita albicilla and group E by Chamoidea and Pitar hebraea . The latter group contains only samples which are generally poor in molluscs. Group A molluscs are diagnostic for reef flats, group B for Porites and faviid carpets, group C for Sarcophyton carpets and group D for tidal/shallow subtidal rock substrates. The different hard substrates are therefore characterized by diagnostic mollusc associations and some of them could also be identified in the fossil record.     

Red Sea Intermediate Water at the Agulhas Current termination

The inter-ocean exchange of water masses at the Agulhas Current termination comes about through the shedding of rings, and this process plays an important role in the global thermohaline circulation. Using several hydrographic sections collected during the ARC (Agulhas Retroflection Cruise), MARE (Mixing of Agulhas Rings Experiment) and WOCE (World Ocean Circulation Experiment), this investigation aims to establish the degree to which Red Sea Intermediate Water (RSIW) is involved in this exchange and at what level of purity. To this end a wide range of hydrographic parameters were used. Upstream from the Agulhas Current retroflection water with clear RSIW origin is shown to move downstream on both the landward and seaward sides of the Agulhas Current with the highest water sample purity or water-mass content exceeding 15%. The least mixed water was found close to the continental shelf. At the retroflection the RSIW purity shows considerable variability that ranges between 5% and 20%. This suggests that RSIW moves down the current in patches of considerably varying degrees of previous mixing. This pattern was also observed in a ring sampled during the ARC experiment. The MARE sections in turn indicate that at times RSIW may be entirely absent in the Agulhas Current. RSIW is therefore shown to travel down the current as discontinuous filaments, and this intermittency is reflected in its presence in Agulhas Rings. From the sections investigated it is therefore clear that any calculation of RSIW fluxes involved in inter-ocean exchange can only be done on the basis of event scales. RSIW not trapped in Agulhas Rings flows east with the Agulhas Return Current.     

Rising to the integration ambitions of Marine Spatial Planning: Reflections from the Irish Sea

Marine Spatial Planning (MSP) is emerging as key tool in the delivery of more effective sea use management and the integration ambitions of MSP are central to its rise to prominence. This paper reviews three key strands of thinking (integrated coastal and ocean management; integrated water resource management; and terrestrial spatial planning) that are informing the development of MSP and sets out a framework encompassing different dimensions of integration that those engaged in MSP might find it helpful to consider. The paper then explores how this framework can inform MSP development and related activity by using it to structure reflections on experience in the Irish Sea. Here the paper draws upon the outputs of a project that was funded by the UK's Economic and Social Research Council concerning Transnational Partnership Working in Support of Marine Spatial Planning in the Irish Sea. The analysis highlights the integration strengths and weaknesses associated with the emerging MSP structures in the Irish Sea and areas where further attention may be beneficial. The paper concludes by reflecting upon the value of the integration framework proposed, how it could be developed, and on key issues that those engaged in MSP in other contexts might need to address in rising to the integration ambitions of MSP.