辽东湾S2冰侧限剪切强度的试验研究

利用试验方法系统地研究了辽东湾S2型海冰侧限剪切强度随剪切应变速率、加载方向、法向应力、温度和冰内孔隙率的变化规律。介绍了S2型海冰各向异性特点及剪切应变速率对剪切破坏方式的效应和韧脆破坏转变的条件。分析了不同加载方向海冰峰值剪切强度的差异 ,获得 - 6 2℃温度下S2冰内摩擦角和内聚力分别为 42°和 70 0kPa。利用统计分析给出峰值剪切强度与冰温和孔隙率的试验关系     

Remote estimation of surficial seafloor properties through the application Angular Range Analysis to multibeam sonar data

The variation of the backscatter strength with the angle of incidence is an intrinsic property of the seafloor, which can be used in methods for acoustic seafloor characterization. Although multibeam sonars acquire backscatter over a wide range of incidence angles, the angular information is normally neglected during standard backscatter processing and mosaicking. An approach called Angular Range Analysis has been developed to preserve the backscatter angular information, and use it for remote estimation of seafloor properties. Angular Range Analysis starts with the beam-by-beam time-series of acoustic backscatter provided by the multibeam sonar and then corrects the backscatter for seafloor slope, beam pattern, time varying and angle varying gains, and area of insonification. Subsequently a series of parameters are calculated from the stacking of consecutive time series over a spatial scale that approximates half of the swath width. Based on these calculated parameters and the inversion of an acoustic backscatter model, we estimate the acoustic impedance and the roughness of the insonified area on the seafloor. In the process of this inversion, the behavior of the model parameters is constrained by established inter-property relationships. The approach has been tested using a 300 kHz Simrad EM3000 multibeam sonar in Little Bay, NH. Impedance estimates are compared to in situ measurements of sound speed. The comparison shows a very good correlation, indicating the potential of this approach for robust seafloor characterization.     

Sea surface temperature variations in the southwestern South China Sea over the past 160 ka

Sea surface temperatures (SSTs) in the southwestern South China Sea have been reconstructed for the past 160 ka using the Uk37 paleothermometer from the core MD01-2392. The temperature differences between glacial times (MISs 6 and 2) and interglacial times (MISs 5.5 and 1) are 2.2~2.5 ℃. Younger Dryas event during the last deglaciation was documented in both the planktonic foraminiferal δ18O and SST records. After MIS 5.5, SSTs displayed a progressive cooling from 28.6 to 24.5 ℃, culminating at the LGM. During this gradual cooling period, warm events such as MISs 5.3, 5.1 and 3 were also clearly documented. By comparison of SST between the study core and Core 17954, a pattern of low or no meridional SST gradients during the interglacial periods and high meridional SST gradients during the glacial periods was exhibited. This pattern indicates the much stronger East Asian winter monsoon at the glacial than at the interglacial periods. Spectral analysis gives two prominent cycles: 41 and 23 ka, with the former more pronounced, suggesting that SSTs in the southern SCS varied in concert with high-latitude processes through the connection of East Asian winter monsoon.     

Phytoplankton biomass and size fractions in surface waters of the Australian sector of the southern ocean

We collected surface water along the 142nd E meridian from Tasmania to Antarctica in December 1999. We measured temperature, salinity and total chlorophyll a; additionally, we collected suspended particle size fractions and used fluorometric analysis to determine the quantity of chlorophyll a in each of four cell size classes: picoplankton (<3 μm), two nanoplankton fractions (3–10 μm and 10–20 μm) and microplankton (> 20 μm). Changes in temperature and salinity show that we crossed 6 water masses separated by 5 fronts. We found low abundance (<0.2 mg m⁻³) of chlorophyll in all size classes, with the exception of higher values near the continent (0.2 to 0.4 mg m⁻³). Lowest chlorophyll values (<0.1 mg m⁻³) were found in the Polar Frontal Zone (51° to 54°S). Microplankton made up the largest portion of total chlorophyll throughout most of the region. We conclude that biomass of all phytoplankton fractions, especially pico-and nanoplankton, was constrained by limiting factors, most probably iron, throughout the region and that ecosystem dynamics within a zone are not circumpolar but are regionalized within sectors.     

珠江口伶仃洋温度分布特征

依据实测资料，分析了伶汀洋冬、夏季的水温分布特征及其变化。冬季湾内水温的分布和变化较单一，夏季由于河流入海流量增大，河流与海洋水体的相互作用加强，明显可见两个冷、暖水锋在河口湾中段相交，上段为高温的河流淡水控制区，下段为低温的陆架水控制区，两者显著的特点是其控制区内温度变化很小，而在锋面转折地带的河口湾中段，盐淡水混合强烈，其温度变化大，温度等值线呈倾斜分布。     

裙带菜配子体基因工程选择标记的研究

研究了裙带菜(Undaria pinnatifida)配子体对除草剂草丁膦的敏感性以及温度对草丁膦处理效果的影响。结果表明,裙带菜配子体对草丁膦敏感;统计学分析得出了草丁膦在不同温度条件下处理裙带菜配子体的半致死浓度(LD50)及95%可信限;温差达到10℃时,相同处理时间各组内不同处理温度样品的LD50之间呈现显著差异,第6天的LD50由10℃组的15.78 mg/L降为20℃组的11.56 mg/L和25℃组的10.33 mg/L。研究发现可以尝试采用草丁膦作为裙带菜配子体遗传转化的选择试剂。     

Geoacoustic Characterisation of Fine-grained Sediments using Single and Multiple Reflection Data

Fine-grained sediments commonly occur in areas of the continental shelf where wave and current energy are weak. Bulk density, compressional wave speed and attenuation are fundamental physical properties of these sediments required for predicting the response of the seabed for diverse branches of marine science. The traditional coring approach is time and labor-intensive, with large uncertainties associated with sediment disturbance in the sampling phase. Acoustic methods offer the advantages of remote sensing, i.e., sampling the sediment structure without mechanical disturbance and a significantly larger seabed coverage rate per unit time. Two different acoustic methods are described: one using short-range single-bounce interactions with the seabed, and the second using long-range modal propagation to infer the sediment properties. The relative strengths and sensitivities of each approach are explored through simulations guided by experience with measured data.     

Cross-Calibration and Long-Term Monitoring of the Microwave Radiometers of ERS, TOPEX, GFO, Jason, and Envisat

The radiometers on board the satellites ERS-1, TOPEX/Poseidon, ERS-2, GFO, Jason-1, and Envisat measure brightness temperatures at two or three different frequencies to determine the total columnal water vapor content and wet tropospheric path delay, a major correction to the altimeter range measurements. In order to asses the long-term stability of the path delay, the radiometers are calibrated against vicarious cold and hot references, against each other, and against several atmospheric models. Four of these radiometers exhibit significant drifts in at least one of the channels, resulting in yet unmodeled errors in path delay of up to 1 mm/year, thus limiting the accuracy at which global sea level rise can be inferred from the altimeter range measurements.     

东太平洋下中新统氧同位素地层与古海洋学意义

研究取自于东太平洋CC48柱状样的钙质超微化石和底栖有孔虫的氧同位素成分变化的结果表明,该区下中新统至少可分出九个氧同位素地层(期),反映该区在早中新世期间至少经历了4次气温上升和5次下降的古气候变化。南极大陆冰川应是形成于早中新世而不是前人认为的中中新世。在早中新世,南极冰体体积有较大的变化。受古气候变化的影响,在早中新世期间东太平洋水柱热结构或温度梯度有比较大的变化,海平面出现多次上升与下降。