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1.
近2000年来福建南部海岸沙丘记录的风沙活动序列   总被引:3,自引:0,他引:3       下载免费PDF全文
对福建南部漳浦地区赤湖海岸沙丘(CH)和大澳海岸沙丘(CDS)近2 000年以来海岸风沙活动历史及其东亚冬季风(EAWM)的关系进行研究。在野外沙丘剖面沉积构造考察基础上, 通过光释光(OSL)测年技术重建研究区海岸风沙活动序列。结果表明: (1)漳浦海岸有近2 000年来发育的多期海岸风沙沉积, 其中, CH沙丘记录的风沙活动期分别为BC100–AD300年、AD500–AD870年、AD1050–AD1380年; CDS沙丘记录了AD200年左右、AD1040–AD1280年以及AD1410–AD1710年3个风沙活动期。(2)研究区海岸风沙活动期与我国东部海岸、东北亚及西北欧海岸风沙活动期大体一致。可能反映了近2 000年以来北半球气候环境发生了大范围的阶段性变化, 各个区域海岸风沙活动起止时间的不同, 反映了各地所处大气环流系统位置的分异或是地方性因素的差异。(3)东亚冬季风对福建南部沿海的风沙活动有明显影响。一般来讲, EAWM强盛时, 海岸风沙沉积比较活跃。虽然在最近2000年的冷暖期都有海岸风沙沉积, 但在暖期仅限于EAWM相对强盛的时期。EAWM影响范围广阔, 是东亚海岸风沙活动周期具有准同时性的基本驱动因素。此外, 北大西洋涛动(NAO)通过影响EAWM的强度驱动海岸风沙活动的阶段性发生, 因而对研究区海岸沙丘发育产生间接影响。本文讨论近2 000年以来季风区海岸沙丘演变序列及驱动机制, 可提取百年尺度上的海岸沉积古环境信息, 探讨东亚冬季风演化特征。  相似文献   

2.
为了探讨福建长乐东部海岸环境演变,运用探地雷达(GPR)探测了研究区海岸沙丘的沉积构造,初步得出以下结论:(1)研究区海岸沙丘沉积构造主要由海滩沉积和海岸沙丘沉积构成,其中下伏沉积为海滩波浪作用形成的波状交错层理,上覆沉积为风成大角度倾斜的交错层理以及局部的水平层理;(2)上部发育的倾向向背的大角度风成交错层理,反映了研究区丰富的沙源、宽阔的海滩、植被扩张的进积海岸特点;(3)从沉积序列分析,研究区海岸地貌环境演变经历了早期的滨岸浅海到晚期的海岸沙丘带两个阶段,反映了海岸向东的进积过程中,外力作用由波浪作用为主演变为风沙沉积作用为主。  相似文献   

3.
沉积物粒度参数的无偏估计及其在长乐海岸的应用   总被引:1,自引:0,他引:1  
根据数理统计方法对粒度参数进行无偏估计,使之较以往参数估计更符合无系统误差的这一估计量的评选标准,并用这一方法对长乐东部海岸的风沙进行了系统的粒度参数分析,结果表明长乐海岸风沙沉积物的主要粒级为细沙,分选好,偏度为近对称,峰态很窄等特征,说明研究区域海岸风沙的搬运风动力主要为NE向、而且动力强度较稳定。  相似文献   

4.
1全新世记录Godwin(1943)早期对广泛分布于欧洲西北部海岸中一晚全新世夹层泥炭的观测表明,上述因子和过程(包括一些区域的显著性)已完成对整个研究区相似地层序列的塑造。仅在主要的潮沟和海岸离岸砂坝发育处或相对海平面下降的稳定期的结果有明显的偏差。  相似文献   

5.
福建长乐东部海岸沙丘风蚀坑研究   总被引:4,自引:0,他引:4  
沙丘风蚀坑是沙质海岸常见的风成地貌形态,是固定沙丘开始活化的明显标志.福建长乐东海岸风沙规模大、地貌类型多样,发育了许多典型的海岸沙丘地貌.由于各种自然和人为因素的作用,部分海岸沙丘发育了风蚀坑.根据对研究区风蚀坑的实地调查,本文论述了风蚀坑的形态特征、风蚀坑内的风速与风向变化,以及风蚀坑的风沙搬运与沉积过程,并对风蚀坑的成因和风蚀坑的演化阶段进行了讨论.文中得出以下几点结论:(1)研究区主要发育槽形风蚀坑,风蚀坑中轴线的方位多介于NE40°~NE65°之间,两侧侵蚀壁坡度介于35°~40°之间.(2)大型风蚀坑,风速在顶部最大.小型风蚀坑,较狭窄部位的风速可能大于项部.(3)大型风蚀坑,沿着中轴线上风向基本上保持不变,近侵蚀壁的风向则发生不同程度的改变.小型风蚀坑,从坑口到坑顶的风向变化明显.  相似文献   

6.
河北昌黎黄金海岸是我国海岸沙丘的集中分布区,选择其中形态典型的新月形沙丘,分不同部位采集了42个沙丘表面沉积物粒度样品,通过对采集样品粒度及其参数的分析与计算,研究了其表面粒度分异。结果表明,昌黎黄金海岸新月形沙丘两翼、迎风坡脚、迎风坡、沙丘顶部、背风坡、背风坡脚的粒度总体上是中砂、分选好、偏度近对称和中等峰态,只有平均粒径在新月形沙丘表面的不同部位存在一定的差异,自迎风坡脚到沙丘顶部粒径变粗,背风坡粒径相对变细,到背风坡脚粒径又变粗,整个沙丘表面粒径顶部最粗、背风坡最细,其分布可以归入沙丘顶部砂物质最粗的分布模式。该粒度分布模式是本区域主风向与强风向交替变化及其风力差异、沙丘两侧不对称和凹型迎风坡形态等组合作用的结果。  相似文献   

7.
粤东及琼东北第四纪老红砂分布于全新世和现代海岸风沙强烈作用带,其野外产状、沉积构造与海滩砂不同,粒度、石英砂磨圆度、石英砂表面微结构统计、孢粉和硅藻等分析证明这些老红砂与海岸沙丘砂有着成因上的联系,热释光年代为距今1.62—5.19万a,故它们是毗邻海滩的海岸风成砂,形成于未次冰期的低海平面期,其形成和分布与盛行风和向岸风的共同作用有关。  相似文献   

8.
尝试恢复了中全新世东亚冬季风表现出的太阳活动以及ENSO周期变化。通过对东海内陆架泥质沉积区EC2005孔进行粒度分析以及AMS碳-14测年,对高分辨率敏感粒度资料揭示的中全新世近700a(距今5.2~5.9ka)东亚冬季风记录与GRIP冰心氧同位素记录的气候变化进行了对比,良好的对应关系说明,东亚冬季风变化与格陵兰冰心揭示的古气候变化有某种内在联系,期间东亚冬季风的增强得到了良好的区域性响应,同时又具有全球性背景。中全新世东亚冬季风具有明显的周期变化,主要表现为62,11a的太阳活动周期以及与现代ENSO周期相似的6,5a周期。东海内陆架EC2005孔泥质沉积物揭示的中全新世东亚冬季风变化与格陵兰冰心氧同位素记录的良好对应说明两者有相似的发生机制,可能是太阳活动以及古ENSO对全球气候系统的影响所致。  相似文献   

9.
河北昌黎典型海岸沙丘的沉积构造及其发育模式   总被引:3,自引:0,他引:3  
采用探地雷达探测了昌黎海岸沙丘区典型横向沙脊和新月形沙丘的沉积构造,据此初步揭示了研究区海岸沙丘的沉积序列特征和发育过程。结果表明,昌黎海岸带在2 000 a BP波浪作用下发育滨岸沙坝,沙坝主要以向海向陆缓倾斜的沉积构造为主,现今的风成沉积发育于滨海相沙坝之上。海岸带向海一侧经历了潮上带前丘到横向沙脊的过程,横向沙脊在东北风的作用下主要发育向陆倾斜的高角度交错层理,同时由于向岸合成风力的阶段性变化,这些层理的倾角略有差异,记录了海岸带风沙活动的周期性变化;内侧新月形沙丘由4组倾角不同的层理组成,被较大规模的二级界面分隔,复合新月形沙丘(链)经历了由盾状沙堆到典型新月形沙丘的加积发育并遭受风蚀的过程。  相似文献   

10.
东海北部泥质区敏感粒度组分对东亚季风演变的响应   总被引:3,自引:0,他引:3  
运用粒级-标准偏差方法对FJ04孔146 cm以上部分进行敏感粒度组分分析与提取,证明选取的敏感粒度组分是本区重要的环境替代性指标,其平均粒径的变化可以用来指示东亚季风的强弱.获得了东海北部泥质区3 kaBP以来东亚冬季风强度的演化过程,结果表明东亚季风经历了两个主要的演变阶段:①3~1.15 kaBP为东亚冬季风较弱,中等程度波动阶段,期间也存在几次冬季风加强期;②1.15 kaBP到现代为东亚冬季风强盛、高频率波动阶段.1.15 kaBP是一个明显的转折点,此外,3 kaBP来敏感粒度组分平均粒级的变化还记录了11次冬季风增强事件,与全球其他地区的气候记录具有极好的对应关系,但在不同的地区的响应程度不同,说明气候变化存在全球一致性和区域响应的特殊性.  相似文献   

11.
东亚冬季风异常对西北太平洋海温的影响   总被引:6,自引:0,他引:6  
利用1950—1998年的月平均海温资料和NCEP/NCAR月平均大气环流再分析资料,研究了东亚冬季风的异常对西北太平洋海温的作用过程。结果表明,南海—台湾附近海域—日本南部以南海域(简称东亚邻海)是海-气热通量异常的显著区。弱东亚冬季风在东亚邻海有偏南风距平,抑制相应海域海-气界面上由海表向大气释放的热通量,从而使得海表温度出现正距平。强冬季风则反之。这种大气-热通量-海温的异常影响过程所需的响应时间约为1个月。东亚邻海冬季发生的海温异常可持续到下一年的夏季。  相似文献   

12.
Seasonal coastal upwelling was analyzed along the NW African coastline (11–35°N) from 1981 to 2012. Upwelling magnitudes are calculated by wind speed indices, sea-surface temperature indices and inferred from meteorological station, sea-surface height and vertical water column transport data. A permanent annual upwelling regime is documented across 21–35°N and a seasonal regime across 12–19°N, in accordance with the climatology of previous studies. Upwelling regions were split into three zones: (1) the Mauritania–Senegalese upwelling zone (12–19°N), (2) the strong permanent annual upwelling zone (21–26°N) and (3) the weak permanent upwelling zone (26–35°N). We find compelling evidence in our various indices for the Bakun upwelling intensification hypothesis due to a significant coastal summer wind speed increase, resulting in an increase in upwelling-favorable wind speeds north of 20°N and an increase in downwelling-favorable winds south of 20°N. The North Atlantic Oscillation plays a leading role in modifying interannual variability during the other seasons (autumn–spring), with its influence dominating in winter. The East Atlantic pattern shows a strong correlation with upwelling during spring, while El Niño Southern Oscillation and Atlantic Multi-decadal Oscillation teleconnections were not found. A disagreement between observationally-based wind speed products and reanalysis-derived data is explored. A modification to the Bakun upwelling intensification hypothesis for NW Africa is presented, which accounts for the latitudinal divide in summer wind regimes.  相似文献   

13.
Temporal and spatial variations of sea surface circulation in the South China Sea were revealed with use of altimetric data provided by TOPEX/POSEIDON from December 1992 to October 1997. The estimated distribution of sea surface dynamic heights from altimetric data coincide well with the results of observation by Soong et al. (1995) and Chu et al. (1998). The RMS variability of sea surface dynamic height, which is obtained after tidal correction based on Yanagi et al. (1997), is high in the central part of the South China Sea, the Gulf of Tongking, the Sunda Shelf and the Gulf of Thailand. The high RMS variability in the Gulf of Tongking, the Sunda Shelf and the Gulf of Thailand is due to set up and set down of sea water by the East Asian monsoon, which is northeasterly during winter and southwesterly during summer. Also, the high RMS variability in the central part of the South China Sea is due to the variations of basin-wide circulation. The circulations are dominant in the central part of the South China Sea during summer and winter, an anticyclonic circulation during summer and a cyclonic circulation during winter. It is suggested that these circulations are controlled by the East Asian monsoon. Hence, there is an interannual variability of the basin-wide circulation associated with the variation of the East Asian monsoon.  相似文献   

14.
新生代以来澳大利亚板块向北漂移了~20°,气候也随之发生了明显改变,即其北部逐渐进入了热带辐合带的影响范围,与亚欧大陆间的联系越来越紧密。上新世时印度尼西亚贯穿流的流通性受到限制,这可能直接促成了澳大利亚季风的形成。海洋沉积记录显示,澳大利亚气候的季节性特征最早出现于~3.5 Ma,而现代意义上的澳大利亚季风则形成于~2.4 Ma。第四纪阶段的澳大利亚季风表现出明显的轨道周期:冰期(间冰期)时夏季风减弱(加强),其演化主要受控于北半球日射量、东亚冬季风的跨赤道作用、表层海水温度与海平面高度变化。在更短的时间尺度上,末次冰期以来的澳大利亚季风则具有与北半球高纬度地区典型气候事件相似的千年周期,大致表现为:北半球的丹斯伽阿德—厄施格尔(Dansgaard/Oeschger)暖期对应着澳大利亚夏季风强度的减弱,而北半球的海因里希(Heinrich stadials)与新仙女木(Younger Dryas)冷事件时澳大利亚夏季风增强。但马来群岛不同地区的上述古气候记录之间存在差异,这可能与区域性因素的影响有关。季风降水的千年尺度变化与热带辐合带的位置密切相关,且其相位变化与同纬度的非洲和南美洲古季风截然不同,明显响应了北半球日射量,这可能与亚洲季风系统的跨赤道作用有关。末次冰期古生产力研究表明,在班达海与澳大利亚西北沿海,澳大利亚季风可以通过影响洋流模式、陆表降水与径流,来控制陆源物质向海洋的输送、海水结构的稳定性以及表层海水过程,进而影响海洋生物生产力。  相似文献   

15.
晚更新世末期东海陆架沙海之形成   总被引:1,自引:0,他引:1  
距今18000a前的海面比现在低约130m。那时东海的大部分、台湾海峡都出露成陆,构成亚洲东部最大的南北向低平原。该低平原在寒冷而又干燥的冬季风作用之下,出现了大面积的沙海环境,或者称为陆架沙海,并构成北半球沙漠带的最东缘。  相似文献   

16.
东亚冬夏季风对热带印度洋秋季海温异常的响应   总被引:5,自引:0,他引:5  
利用多年的Reynolds月平均海表温度资料和NCEP/NCAR全球大气再分析资料,分析了热带印度洋秋季海表温度距平(SSTA)与后期东亚冬夏季风强度变化的关系。结果表明,热带印度洋秋季SSTA的主要模态是全区一致(USB)型和偶极子(IOD)型,USB型模态主要代表热带印度洋秋季SSTA的长期变化趋势,而IOD型模态主要反映热带印度洋秋季SSTA的年际变化。热带印度洋秋季海温气候变率中既存在着明显的ENSO信号,也有独立于ENSO的变率特征,独立于ENSO的热带印度洋秋季SSTA变化的主要模态仍是USB型和IOD型。前期秋季USB模态与东亚冬季风及东亚副热带夏季风之间为负相关关系;与前期正(负)IOD模态相对应,南海夏季风强度偏弱(强),而东亚副热带夏季风强度偏强(弱)。USB型和IOD型模态对后期东亚冬、夏季风强度变化的影响是独立于ENSO的,但ENSO起到了调节二者相关显著程度的作用。  相似文献   

17.
南海北部陆坡区DLW3101孔沉积物特征及古环境意义   总被引:1,自引:1,他引:0  
利用氧同位素地层学方法确定DLW3101孔底部年龄约为306 ka BP,对沉积物进行粒度和地球化学元素分析,结果显示:22.1~63 μm粗粒级组分的高值可用来指示海平面下降和东亚冬季风的强盛,0.35~1.16 μm和2.32~13.14 μm细粒级组分的高值可用来指示海平面上升和东亚夏季风的增强;Al/Ti和K/Ti比值反映的沉积物源区化学风化强度变化可用来指示东亚夏季风的强弱。  相似文献   

18.
Altogether three coastal dune fields, one located north and two south of the city of Essaouira, Atlantic Morocco, have been investigated to establish the distribution and overall sand volumes of various dune types. The purpose of the study was to characterize and classify the aeolian landforms of the coastal dune belt, to estimate their sand volumes and to assess the effectiveness of coastal dune stabilization measures. The northern dune field is 9 km long and lined by a wide artificial foredune complex fixed by vegetation, fences and branches forming a rectangular grid. Active and ephemeral aklé dunes border the inner backshore, while some intrusive dunes have crossed the foredune belt and are migrating farther inland. The total sand volume of the northern dune belt amounts 13,910,255 m3. The central coastal sector comprises a much smaller dune field located just south of the city. It is only 1.2 km long and, with the exception of intrusive dunes, shows all other dune types. The overall sand volume of the central dune field amounts to about 172,463 m3. The southern dune field is characterized by a narrower foredune belt and overall lower dunes that, in addition, become progressively smaller towards the south. In this sector, embryonic dunes (coppice, shadow dunes), tongue-like and tabular dunes, and sand sheets intrude from the beach, the profile of which has a stepped appearance controlled by irregular outcrops of old aeolianite and beach rock. The total volume of the southern dune field amounts 1,446,389 m3. For the whole study area, i.e. for all three dune fields combined, a sand volume of about 15,529,389 m3 has been estimated. The sand of the dune fields is derived from coastal erosion and especially the Tensift River, which enters the sea at Souira Qedima some 70 km north of Essaouira. After entering the sea, the sand is transported southwards by littoral drift driven by the mainly north-westerly swell climate and the Trade Winds blowing from the NNE. This sand feeds the beaches along the coast, from where it is blown obliquely onshore to generate the dune fields. The maximum sand input occurs in the north, from where it gradually decreases southwards, this being also reflected in the grain size and dune typologies. The study shows that dune stabilization measures have been reasonably effective along most of the coast, with the exception of a large area immediately north of Essaouira where the almost complete destruction of the plant cover has reactivated sand mobility—this may in the future threaten the city.  相似文献   

19.
南海冬季海浪的时空变率特征   总被引:4,自引:1,他引:3  
The spatial and temporal variation characteristics of the waves in the South China Sea(SCS) in the boreal winter during the period of 1979/1980–2011/2012 have been investigated based on the European Centre for Medium-range Weather Forecasts interim(ERA-Interim) reanalysis dataset. The results show that the leading mode of significant wave height anomalies(SWHA) in the SCS exhibits significant interannual variation and a decadal shift around the mid-1990 s, and features a basin-wide pattern in the entire SCS with a center located in the west of the Luzon Strait. The decadal change from a weak regime to a strong regime is mainly associated with the enhancement of winter monsoon modulated by the Pacific decadal oscillation(PDO). The interannual variation of the SWHA has a significant negative correlation with the El Ni?o Southern Oscillation(ENSO) in the same season and the preceding autumn. For a better understanding of the physical mechanism between the SCS ocean waves and ENSO, further investigation is made by analyzing atmospheric circulation. The impact of the ENSO on the SWHA over the SCS is bridged by the East Asian winter monsoon and Pacific-East Asian teleconnection in the lower troposphere. During the El Ni?o(La Ni?a), the anomalous Philippine Sea anticyclone(cyclone) dominates over the Western North Pacific, helps to weaken(enhance) East Asian winter monsoon and then emerges the negative(positive) SWHA in the SCS.  相似文献   

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