基于小波变换的西、北江水沙关系特征分析

对珠江高要、石角站近50年(1957-2000年)流量、含沙量和输沙量月均时间序列利用复Morlet小波变换,分析水沙序列的多时间尺度变化特征,并在流量的特征时间尺度上分段建立相应的水沙关系,结果显示:(1)两站水沙时间序列具有多时间尺度特征,年内洪枯季周期最为显著,水沙丰枯变化不同期.流量的长周期振荡特征较含沙量与输沙量明显,中时间尺度振荡在20世纪70年代有明显的突变点,石角站突变点略滞后于高要站.高要站输沙量明显多于石角站,在20世纪80年代之后石角站输沙量明显减少;(2)特征时间尺度上水沙关系存在丰枯变化.水沙关系公式Cs=aQb中,系数a值变化反映出少水期泥沙的供给量较小,指数b值显示少水期水流的挟沙能力强.两个多水时段(1992-2000年和1957-1974年)水沙关系近似平行下移,说明水流的挟沙能力相近,但泥沙供给量存在一定差别,前一个多水时段泥沙供应量小于后一多水时段,明显的人类活动是主要原因.整体时段的水沙关系曲线只能代表多水期的水流挟沙特征,而不能代表少水期的水沙关系.     

近50年来长江入河口区含沙量和输沙量的变化趋势

为了研究长江入河口区含沙量和输沙量的变化规律,用 Hilbert-Huang 变换对长江大通水文站近 50 a 来的月均含沙量和输沙量时间序列进行分析,以研究它们在长江入河口区的演变特征.结果显示,虽然长江大通站多年含沙量和输沙量与多年径流量之间相关性不显著,但月均含沙量和输沙量仍具有类似径流的周期性震荡特征,即两者均具有显著的季节、洪枯季变化;含沙量具有 26 a,12 a,4 a 和 2 a 左右的周期性变化,输沙量具有 27 a,7 a,4 a,2 a的周期性变化,这些周期性震荡主导着长江入河口区含沙量和输沙量的变化;20 世纪 60 年代到 90 年代和 80 年代中期到 90 年代分别是含沙量和输沙量下降加速的阶段,但 90 年代以后含沙量和输沙量下降呈减缓趋势.     

长江口水沙变化与趋势预测

随着长江流域水土保持、上游水库拦蓄调节、沿江用水增加及气候变化,进入长江口的水沙通量发生改变,入海泥沙量锐减。此外,长江口相继实施了深水航道治理、青草沙水源地、浅滩圈围等大型工程。因此,需要针对长江口水沙变化开展相关研究。对长江口陆相和海相水沙变化规律及趋势、河床容积与泥沙收支变化以及整治工程下分汊河口演变预测等进行了概述,预测了今后10～50年大通站流量、含沙量、输沙量变化以及南北槽的演变趋势,为进一步研究变化条件下的长江口重大工程安全提供基础条件。     

近70年珠江水沙变化特征及人类活动影响因素分析

收集1954—2019年珠江流域的3个主要水文站:高要站(西江)、石角站(北江)和博罗站(东江)的径流量与输沙量资料,运用Mann-Kendall非参数检验法和累积距平法,分析了珠江流域水沙近70年来的年际变化特征。结果表明,1954—2019年珠江年径流量变化趋势不明显,年输沙量呈下降趋势,高要站与博罗站年输沙量分别于2003年和1991年发生突变,多年平均输沙量较突变前分别减少了71.30%和48.88%,石角站未发生明显突变。2000—2019年珠江流域归一化植被指数(Normalized Difference Vegetation Index,NDVI)整体呈上升趋势,植被覆盖改善区域占流域总面积的89.27%,但NDVI与水沙变化的相关性不显著。运用双累积曲线法对不同时期人类活动对珠江输沙量的影响进行分析,20世纪80年代以来,森林砍伐、水库建设、水土保持等人类活动对输沙量造成显著影响,2000年以后龙滩水库建设是西江输沙量下降的主要原因,植被改善对于珠江流域输沙量的影响不明显。     

黑潮输送的异常及其与大尺度海气相互作用的关系

以128.5°E为界,沿27°N,北太平洋西边界流输送可以分成呈明显负相关的东、西2段。西段(即黑潮)主要参与副热带环流(STG)和经向环流(STC);东段主要参与日本东南的反气旋式涡旋再回流。从气候态来看,西段输送在7、8月份最大,3月份次大;东段输送在6—8月份最小,其它月份比较接近;整体结果表现为全年有2个接近的极大值,分别是3、4月份和7、8月份。从年序列来看,西段输送在20世纪70年代后期有一次明显的突变;而东段在1955年突然减小,在1963年突然增大。小波分析表明,东、西两段的振荡周期都随时间变化。西段输送时间序列的20a左右周期振荡在1976年以前非常明显,9a左右周期振荡在1985年以后比较显著;东段输送的13a左右周期在1976年以前显著,1985年以后的主要振荡周期从7a逐渐减小到3a左右。奇异谱分析表明,西段输送的年代际变化占总方差的45%,年际变化占总方差的13.6%;东段输送的年代际变化占总方差的24.3%,年际变化占总方差的32.3%。黑潮输送异常和太平洋年代际振荡(PDO)及ENSO有着非常密切的关系。在年代际尺度上,一个可能的过程是,PDO超前于黑潮输送异常;异常的黑潮输送通过改变北太平洋中部的SST梯度引起的海气相互作用过程而调制ENSO的变化。在年际尺度上,黑潮输送异常滞后于PDO和ENSO变化,且呈负相关。     

黄河入海径流量周期变化与东亚夏季风的关系研究

为揭示近 70 年东亚夏季风与黄河夏季入海径流量的多尺度特征以及二者之间的响应关系,本文利用集合经验模态分解 （EEMD） 和小波分析对二者的多尺度特征进行研究,利用交叉小波分析和小波相干性等方法对东亚夏季风和黄河夏季入海径流量在时频域内的共振周期以及相干性进行探究。结果表明：东亚夏季风具有显著的年际、年代际尺度特征,且以年际周期振荡最为显著,其中,2.7 a 左右的周期尺度对东亚夏季风的整体影响程度最高,另外,40 a 左右的年代际周期亦具有较强显著性。黄河夏季入海径流量的年际、年代际尺度周期均通过了 80 %的显著性检验,且以 2.1 a 左右的年际周期为主。东亚夏季风与黄河夏季入海径流量的交叉小波功率谱显示二者在 2 a、6~7 a 左右具有显著的共振周期,且在 1980— 1990 年之间通过了 95 %的显著性检验,由二者的小波相干谱发现,东亚夏季风和径流量的显著性在低能量区大于高能量区,且东亚夏季风提前径流量约 1/4 个周期,另外,1980—2000 年之间在 6~7 a 左右周期尺度上二者的相干性极强。该研究可为黄河下游水资源管理及预测提供一定的理论依据。     

赤道新加坡地区潜热能相当温度的低频振荡

本文用最大熵谱分析法,研究了1984年1月～1988年12月5年新加坡地区潜热能相当温度的低频振荡特征.主要结果如下:(1)赤道新加坡地区潜热能相当温度谱与云量谱很相似,它可以反映大气中的低频振荡特征.(2)潜热能相当温度具有203、47～52、24～28、15～18和8～11天、的周期性振荡.(3)1986～1987埃尔尼诺对潜热能相当温度的振荡周期没有影响.(4)东北冬季风和西南夏季风期,潜热能相当温度的振荡周期都一样,不受季节变化的影响.本文所得到的初步结果可能有助于新加坡地区的中期天气预报.     

长江口南支河床容积对来沙量减少的响应规律研究

近年来,长江中下游来沙量持续性减小,其对河床冲刷的效应已逐渐在长江口显现。然而,长江口河床容积的变化特征缺少定量研究,与来沙量减小的时空响应规律不明确。通过分析长江大通站、徐六泾站的泥沙资料,并统计不同高程下的河床容积随时间变化特征,建立不同区段、不同高程河床容积与上游不同时段平均来沙量的关系。结果表明,大通站2003—2020年的年输沙量较三峡工程建成前有大幅减少,其对徐六泾站的当年洪季含沙量有着直接且显著的影响。长江口南支0 m以下河床处于冲刷态势,2003年后河床冲刷速率有明显增加,其中-10 m以下深槽部分的冲刷量贡献最大。南支主要落潮通道河床容积与前1年大通平均来沙量具有显著的相关性,因此来沙量减小主要引起长江口落潮通道河床容积增加,其效应具有约1 a的滞后性。     

长江河口径流与盐度的谱分析

根据大通水文站的流量和引水船站的盐度系列资料,应用谱分析方法研究长江口径流、盐度的变化规律及两者的相互关系.分析表明,长江口径流存在4～8a,2～3a,1.5a,1a,30～60d及20d的及化周期;盐度存在5～10a,2～3a,1.5a,1a,0.5a,40～50d,26～30d,14～15d7～8d及3.5d的变化周期.径流和盐度的谱结构在各水文年基本一致,均以1a周期变化占优势,但盐度谱结构在高频部分较径流的谱结构具有更大的振荡.盐度与流量的5～10a,2～3a,1.5a,1a的周期振动上存在高相关.径流对盐度变化的影响主要体现在低频部分.在低频变化中表现为盐度变化滞后于径流变化,在高频带呈同步变化.     

本溪王家崴洞10500～5000aBP石笋记录及区域气候意义

基于典型东亚季风区辽宁省本溪市2支石笋样品(W6与W4),通过9个230 Th年龄和386个氧同位素数据,重建了10 500～5 000aBP期间平均分辨率为12～34a的氧同位素时间变化序列。研究时段石笋δ18 O相对振幅为2.0‰,在平均值约-8.5‰上下波动,指示了早全新世东亚季风强度的长期趋势变化和百年尺度振荡信息。相同时段本溪王家崴洞、湖北三宝洞、贵州董哥洞石笋δ18 O记录对比结果表明,全新世石笋δ18 O长期增加趋势类似于北半球太阳辐射能量变化曲线,但东北地区石笋δ18 O大约在10 500a已达到最大值,早于长江流域以南地区约1 000a,这可能表明全新世亚洲季风降水并不同步变化,可能与热带、亚热带季风系统差异响应于区域大气环流有关。功率谱分析W6石笋δ18 O时间序列发现其存在显著的225和91a的周期,与树轮Δ14 C周期(208和88a)基本一致,揭示了中全新世百年尺度东亚季风变化可能主要响应于太阳活动。     

Fluxes of Amino Acid and Hexosamine in Sinking Particles in Subarctic and Arctic Coastal Regions

Spatial and temporal variations in the vertical fluxes of amino acids and hexosamine were studied at coastal sites in the south of the Chukchi Sea, Otsuchi Bay, and the center and the entrance of Funka Bay. Amino acid fluxes were higher in the upper trap than in the lower trap material, but hexosamine fluxes were opposite to amino acid fluxes. The ratios between protein amino acids (Asp, Glu and Arg) and their decomposition products (β-Ala, γ-Aba and Orn) indicate that the labile organic matter was more abundant in the upper traps than in the lower ones and increased during periods of enhanced amino acid fluxes. The ratios of Ser/Gly did not vary temporally and spatially and were nearly constant, indicating that Ser and Gly were preserved in a stable form within sinking particles. Hexosamine/amino acid ratios of these particles were higher in the lower sediment trap than in the upper trap material. This implies that the sinking particles derived from zooplankton are relatively more abundant in deep layers than in the surface layer in the water column. We suggest that the difference in amino acid flux and the composition between the upper and lower trap material is influenced by the processes of microbial decomposition and zooplankton consumption of sinking particulate organic matter. This revised version was published online in July 2006 with corrections to the Cover Date.     

On contemporary sedimentation at the titanic survey area

The basic parameters of the sedimentation environment are considered: the Western Boundary Deep Current that transports sedimentary material and distributes it on the survey area; the nepheloid layer, its features, and the distribution of the concentrations and particulate standing crop in it; the distribution of the horizontal and vertical fluxes of the sedimentary material; and the bottom sediments and their absolute masses. The comparison of the vertical fluxes of the particulate matter and the absolute masses of the sediments showed that the contemporary fluxes of sedimentary material to the bottom provided the distribution of the absolute masses of the sediments in the survey area during the Holocene.     

Excess polonium-210 in the coastal atmosphere originating from marine biogenic material

1Introduction In the atmosphere, gaseous radon-222 (t1/2=3.8 d) produces a series of decay products,lead-210(t1/2=22.3 a), bismuth-210 (t1/2=5.01 d), andpolonium-210 (t1/2=138.4 d), etc. These radondaughters are readilyadsorbed onto aerosols and thengrowd…     

Geochemistry of dispersed sedimentary matter and its fluxes in the water column of the Caspian Sea

The first data on the chemical composition of dispersed matter from sedimentary traps are reported. The suspended components of sedimentary matter (amorphous silica, organic matter, carbonates, and lithogenic material, as well as Fe, Mn, and minor elements) are considered. As a result, it is shown that the intraannual variability in vertical fluxes of sedimentary matter is characterized by a seasonal increase in spring and autumn. The high fluxes of the components of sedimentary matter on the northern and southern slopes of the Derbent Basin in winter are explained by precipitation of material from the nepheloid layer that forms over the contour current.     

伶仃洋低频水流与水沙纵向输运

在分析实测燃料（1978－1979）的基础上，运用物质纵向输移模式讨论了伶仃洋河口湾余流的垂向结构，同时，对同步资料进行低通滤波处理，得到垂向低频水流分布。结果表明，两种分析方法对伶仃洋河口环流与水沙输移的解释基本一致，东、西、两槽均存在明显的垂向环流，平均流、斯托克斯漂移效应，以及垂向净环流是净输沙的主要贡献项。     

Regeneration of chemical elements from settling particles collected by sediment trap in Funka Bay,Japan

Sediment trap experiments were carried out 39 times during the years from 1977 to 1981 in Funka Bay, Hokkaido, Japan. The observed total particulate flux varies seasonally, that is, the particulate fluxes in winter and spring are larger than those in summer. The fluxes in all seasons increased with depth. Major components of settling particles are aluminosilicate in winter, biogenic silicate in spring and organic matter and terrestrial material in summer, respectively. The fluxes of each chemical component observed with sediment traps are normalized to that of Al by assuming that the actual flux of Al is equal to the accumulation rate onto the sediment surface. Vertical changes of the normalized flux of each chemical component indicate the following: Fe was not regenerated from the settling particles in the water column. Mn was regenerated from the settling particles in the lower layer exclusively between 80 m depth and the sediment surface. Cd was actively regenerated in the upper layer above 80 m depth. Phosphate was regenerated in the upper layer, while biogenic silicate was in the lower layer. The silicate regeneration, therefore, occurs after phosphate regeneration. The material decomposing in the water column below 40 m has an atomic ratio of P ∶ Si ∶ C = 1 ∶ 52 ∶ 128.     

Seasonal and annual variability in particle fluxes in the Gulf of California: A response to climate forcing

A six-year time series of sediment trap samples is used to document seasonal and interannual changes in particle fluxes in Guaymas Basin, Gulf of California. Sedimentation in this region of the Gulf of California is dominated by two seasonally varying components: biogenic silica during the late fall–spring and lithogenic material during the summer. This variability in sediment fluxes is a direct response to the seasonally reversing monsoon climate in this region. In addition, this seasonal variability in particle flux to the seafloor combined with the lack of bioturbation results in the formation of sediment laminae or varves in Guaymas Basin. Observed interannual differences in the magnitude of sediment fluxes appear to be related to ENSO. These findings indicate that biogenic sediment fluxes, and hence primary productivity, are higher during non-ENSO years in the central Gulf of California. A decrease in the carbonate: opal flux ratio from 1991 to 1996 indicates that diatoms became an increasingly important component of the plankton during this period and further supports our findings that productivity in Guaymas Basin is higher during non-ENSO years.     

Particulate Flux and Cd/P Ratio of Particulate Material in the Pacific Ocean

Time-series Mark 7 sediment traps were deployed at three stations at 0°N, 13°N and 48°N along 175°E to investigate seasonal and spatial variations of particulate material flux. Chemical analysis of particulate material was performed for four major chemical components, viz. opal, CaCO₃, organic material and clay minerals, Cd and P in the particulate material were also determined. We discuss the characteristics of particulate material at each site and the transportation of Cd and P to deep water by the particulate material. The total mass fluxes and variation of fluxes at each site reflect oceanographic conditions, such as biological productivity and kind of major planktonic organisms. At the northern site, large mass fluxes with a spring bloom and high ratios of opal are characteristic. Relatively small mass fluxes with high ratios of CaCO₃ are distinct, and dissolution of CaCO₃ due to sinking is recognized in the middle latitude and 0°N sites. The larger flux at the lower trap than the upper trap at the equatorial site suggests influence by lateral transport in the deep water. Distinctive decreasing Cd/P ratio and CaCO₃ concentrations in the particulate material with increasing depth suggests that the change of Cd/P ratio in the intermediate and deep water occurs through the dissolution of CaCO₃. The dissolved Cd/P ratios in the deep water are proportional to the age of the deep water in the Atlantic but not in the Pacific. This is explained by the difference of kinds of particulate material transporting Cd and P in the deep water between the oceans. That is, the major planktonic organisms are planktons of CaCO₃ tests in the Atlantic Ocean and diatoms of opal tests in the North Pacific Ocean.     

Origin and variability of downward biogeochemical fluxes on the Rhone continental margin (NW mediterranean)

A one year study of downward particle fluxes conducted in the northwestern Mediterranean Sea is presented. Two mooring lines equipped with sediment traps and current meters were deployed at around 1000 m depth on the northeastern continental slope of the Gulf of Lions, one inside the Grand-Rhône canyon and the other outside on the adjacent open slope. Mean total mass fluxes increased slightly with trap depth inside the canyon, a feature quite typical of fluxes in continental margin environments. The near-bottom trap inside the canyon collected more material than its counterpart deployed at equivalent depth on the open slope, indicating a preferential transport of material within the canyon. Major biogeochemical constituents (organic and inorganic carbon, opal, and siliciclastic residue) revealed a marked difference in particle composition between the sub-surface (80 m) and deeper traps, suggesting the existence of at least two sources of material. The two shallower traps showed a clear biological signal: flux peaks were related to periods of surface biological production, especially perceptible in summer and autumn. The particulate matter trapped at deeper levels in the canyon and on the open slope was characterized by a more stable composition with a major lithogenic contribution, originating from sedimentary material most probably resuspended on the upper- or mid-slope. The seasonal variability was dominated by the summer/winter alternation; the latter period was characterized by a weak stratification of the water column and an enhanced current variability favoring vertical exchanges. The present results are compared with those obtained previously in the Lacaze-Duthiers canyon on the southwestern side of the Gulf of Lions. The comparison shows strong differences between the NE entrance and the SW exit of the gulf, with respect to the general along-slope circulation of water masses, both in terms of intensity of particulate fluxes and transport processes.     

High resolution profiles of vertical particulate organic matter export off Cape Blanc,Mauritania: Degradation processes and ballasting effects

Vertical carbon fluxes between the surface and 2500 m depth were estimated from in situ profiles of particle size distributions and abundances me/asured off Cape Blanc (Mauritania) related to deep ocean sediment traps. Vertical mass fluxes off Cape Blanc were significantly higher than recent global estimates in the open ocean. The aggregates off Cape Blanc contained high amounts of ballast material due to the presence of coccoliths and fine-grained dust from the Sahara desert, leading to a dominance of small and fast-settling aggregates. The largest changes in vertical fluxes were observed in the surface waters (<250 m), and, thus, showing this site to be the most important zone for aggregate formation and degradation. The degradation length scale (L), i.e. the fractional degradation of aggregates per meter settled, was estimated from vertical fluxes derived from the particle size distribution through the water column. This was compared with fractional remineralization rate of aggregates per meter settled derived from direct ship-board measurements of sinking velocity and small-scale O₂ fluxes to aggregates measured by micro-sensors. Microbial respiration by attached bacteria alone could not explain the degradation of organic matter in the upper ocean. Instead, flux feeding from zooplankton organisms was indicated as the dominant degradation process of aggregated carbon in the surface ocean. Below the surface ocean, microbes became more important for the degradation as zooplankton was rare at these depths.