Impacts of the wintertime mesozooplankton community to downward carbon flux in the subarctic and subtropical Pacific Oceans     

《Deep Sea Research Part I: Oceanographic Research Papers》2013

We compared wintertime depth distributions of the mesozooplankton community and dominant copepods between the subtropical (S1) and subarctic (K2) Pacific Oceans to evaluate the relative importance of actively transported carbon by vertical migrants to sinking particulate organic carbon flux. Primary production was higher and the ratio of sinking particulate organic carbon flux to primary production was lower at S1 compared with those at K2. The mesozooplankton community was lower in abundance and biomass at S1 compared to K2. Copepods were the dominant group among both mesozooplankton abundance and biomass throughout the water column down to 1000 m at both sites. The depth distribution showed that diel vertical migration was obvious for the mesozooplankton abundance and biomass at S1 but was not apparent for the abundance at K2, because the dominant component was diurnally migrating species at S1 and overwintering species residing at mesopelagic depths at K2. The major components of diel migrants were copepods and euphausiids at S1 and only euphausiids at K2. Respiratory flux by the diurnally migrating mesozooplankton was estimated to be 2 mgC m⁻² day⁻¹ at S1 and 7 mgC m⁻² day⁻¹ at K2. The respiratory flux was equivalent to 131% of sedimentary fecal pellet flux at S1 and 136% of that at K2. Because pathways of downward carbon flux are facilitated by the mesozooplankton community, the actively transported carbon (respiration of dissolved inorganic carbon, excretion of dissolved organic carbon and egestion of fecal pellets at depth) might be larger during winter than the flux of sinking fecal pellets.  相似文献   

基于PAADCP 的海流流速的误差分析及校正方法     

郑一  岳军  纪乃华  施国全  韦俊霞 《海洋科学》2013,37(5):81-86

为了更加合理、有效地利用海流测速数据,必须进行误差分解和校正。通过分析相控阵声学多普勒海流剖面仪(PAADCP)测试海流流速的原理,提出了海试数据粗差区别与动态校正的算法,采用小波多尺度分析方法,降低了系统误差和随机误差,建立了海流流速的误差分析与校正方法。利用海试实测的垂向流速数据,分析了一般情况下的海流流速的误差,得到垂向流速的均值±0.02 m/s,误差精确度小于0.23 m/s,验证了方法的有效性及合理性。所得算法和方法对于海流测速数据的实时处理和后处理具有实用价值。  相似文献   

Thermal constraints on the respiration and excretion rates of krill,Euphausia hanseni and Nematoscelis megalops,in the northern Benguela upwelling system off Namibia     

《African Journal of Marine Science》2013,35(3):391-399

Rates of respiration and ammonia excretion of Euphausia hanseni and Nematoscelis megalops were determined experimentally at four temperatures representative of conditions encountered by these euphausiid species in the northern Benguela upwelling environment. The respiration rate increased from 7.7 µmol O₂ h^?1 g_ww ^?1 at 5 °C to 18.1 µmol O₂ h^?1 g_ww ^?1 at 20 °C in E. hanseni and from 7.0 µmol O₂ h^?1 g_ww ^?1 (5 °C) to 23.4 µmol O₂ h^?1 g_ww ^?1 (20 °C) in N. megalops. The impact of temperature on oxygen uptake of the two species differed significantly. Nematoscelis megalops showed thermal adaptations to temperatures between 5 °C and 10 °C (Q₁₀ = 1.9) and metabolic constraint was evident at higher temperatures (Q₁₀ = 2.6). In contrast, E. hanseni showed adaptations to temperatures of 10–20 °C (Q₁₀ = 1.5) and experienced metabolic depression below 10 °C (Q₁₀ = 2.6). Proteins were predominantly metabolised by E. hanseni in contrast to lipids by N. megalops. Carbon demand of N. megalops between 5 and 15 °C was lower than in E. hanseni versus equal food requirements at 20 °C. It is concluded that the two species display different physiological adaptations, based on their respective temperature adaptations, which are mirrored in their differential vertical positioning in the water column.  相似文献   

Unification of vertical datums by GPS and gravimetric geoid models using modified stokes formula     

Hossein Nahavandchi  Lars E. Sjöberg 《Marine Geodesy》2013,36(4):261-273

In general, neighboring vertical datums can be compared directly at one or more common points on the border between the datums. This direct method requires leveling and gravity measurements. Such a direct connection is not possible if the datums are separated by an ocean or another body of water. Then a rigorous mathematical model, an indirect approach, may be useful. In order to connect regional vertical datums, a rigorous mathematical model is derived based on a method by Rummel and Teunissen. In this study, two vertical datums are connected indirectly by means of a combination of precise geocentric positions of tide gauge sites and their geoid heights in one geocentric coordinate system and their height values in the respective height datums. This method is used to connect the Swedish and the Finnish height systems. The difference between Swedish RH70 and the Finnish N60 height systems is estimated to —12.1±2.7 cm. The results are mostly in good agreement with those of the direct approach by Sjöberg and by Ekman and the indirect approach by Pan and Sjöberg.  相似文献   

Predicting Global Seafloor Topography Using Multi-Source Data     

Min zhang Hu  Jian cheng Li  Hui Li  Chong Yang Shen  Tao yong Jin  Le lin Xing 《Marine Geodesy》2013,36(2):176-189

A new one-minute global seafloor topography model was derived from vertical gravity gradient anomalies (VGG), altimetric gravity anomalies, and ship soundings. Ship soundings are used to constrain seafloor topography at wavelengths longer than 200 km and to calibrate the topography to VGG (or gravity) ratios at short wavelengths area by area. VGG ratios are used to predict seafloor topography for wavelength bands of 100–200 km and to suppress the effect of crust isostasy. Gravity anomalies are used to recover seafloor topography at wavelengths shorter than 100 km. The data processing procedure is described in detail in this paper. The accuracy of the model is evaluated using ship soundings and existing models, including General Bathymetric Charts of the Oceans (GEBCO), DTU10, ETOPO1, and SIO V15.1. The results show that, in the discussed regions, the accuracy of the model is better than ETOPO1, GEBCO, and DTU10. Additionally, the model is comparable with V15.1, which is generally believed to have the highest accuracy. In the north-central Pacific Ocean, the accuracy of the model increased by approximately 29.5% compared with the V15.1 model. This indicates that a more accurate seafloor topography model can be formed by combining gravity anomalies, VGG, and ship soundings.  相似文献   

北太平洋西边界流的低频变化特征     

蔡榕硕  齐庆华  张启龙 《海洋学报》2013,35(1):9-14

基于日本气象厅长时间序列的温、盐度再分析资料,利用动力计算方法分析了北太平洋西边界的北赤道流及其下游黑潮和棉兰老流流量的年际和年代际变化,并探讨了北赤道流变化的可能原因。结果表明,北赤道流和黑潮具有比较一致的年际和年代际变化,均在1976年前后发生了一次气候跃变,之后有长期偏强的趋势,而棉兰老流的年际和年代际变化则有所不同。特别是,北赤道流1976年之后增加的流量似乎大多进入黑潮,而流入棉兰老流的流量则减少。进一步的分析还表明,西传的Rossby波和棉兰老冷涡的变动可能对北赤道流的年际变化有重要影响。  相似文献   

Vertical distribution patterns of macrofauna in a subtropical near‐shore coastal area affected by urban sewage     

Pablo Muniz  Ana M. S. Pires‐Vanin  Natalia Venturini 《Marine Ecology》2013,34(2):233-250

The vertical distribution of macrobenthic fauna, heavy metals, and other physico‐chemical and biological characteristics of the sediments were studied in three sediment layers (0–7, 8–14, 15–21 cm) at seven stations in the Ubatuba region, north coast of São Paulo State, Brazil at several temporal and spatial scales. Six stations were located in the inner bay near the riverine run‐off, and one was outside the bay, distant from the riverine influence. The samples were collected four times in 1 year, on a seasonal basis. Sediments were basis comprised predominantly of very fine sand and the vertical distribution of grain size was uniform to a depth of 21 cm in all stations. Higher values of total organic matter, organic carbon, sulphur, heavy metals and phaeopigments were recorded at the inner Ubatuba Bay stations, probably due to the riverine influence. C/N ratios indicated a mixed origin of organic matter with a major contribution of terrestrial material in the inner stations. The vertical distribution of heavy metals showed a slight decline with sediment depth in the inner stations, indicating the present contribution. Most of the macrofauna was found at the surface sediment layer. Biological data showed that in the inner stations of Ubatuba Bay, which are under the influence of urban sewage and are moderately polluted, the fauna was distributed more superficially within the substrate than in St. 7, which is located in the external portion of the bay distant from sewage inputs. The environmental quality of the sites studied varied little throughout the year, at least in relation to the variables considered here. Temporal variation in the vertical distribution of benthic fauna was not evident in the four sampling surveys analysed. Only minor changes in the vertical distribution of the total fauna were detected in the seasonal scale, with the organisms located less deep within the sediment column in summer, indicating some influence of the tourism impact and/or rainy season.  相似文献   

西天山南麓两次暴雪过程对比分析     

张俊  于碧馨  李如琦  李桉孛 《沙漠与绿洲气象(新疆气象)》2024,18(5)

利用常规气象观测、FY-4A卫星及ERA5再分析数据,对比分析2021年2月25—27日（过程I）和4月1—4日（过程II）西天山南麓阿克苏地区拜城县2次暴雪过程成因。结果表明有差异也有共性,共性为均在中亚低值系统影响下发生,300 hPa偏西急流、500 hPa低涡（低槽）、850 hPa偏东急流、地面冷高压冷锋及暴雪区上空垂直环流的发展是形成暴雪的主要动力机制;均有偏西和西南路径的水汽输送,水汽强辐合出现在700 hPa;降雪期间TBB极值、＜-30 ℃的维持时间及＞-5 ℃对降雪量级、持续时间及降水相态预报有很好的指示意义。不同点主要表现在：（1）过程I为中亚低槽快速东移型,偏东急流仅在850 hPa,急流强度较弱且位置偏南,过程II为中亚低涡缓慢东移型,700 hPa、850 hPa有明显偏东急流且持续时间长,位置西伸至西天山南麓阿克苏地区;（2）与过程I相比,过程II上升运动中心更接近暴雪中心,且强度强、伸展高、持续时间长,冷暖交汇更剧烈,暖平流导致降水相态发生变化,偏东水汽输送明显且辐合强度更强、辐合持续时间更长。  相似文献   

盾构区间过站技术研究     

冯义  陈寿根 《探矿工程》2010,37(8):76-80

城市地铁广泛采用盾构施工,目前城市盾构区间施工一般具有工程量小、里程短、盾构过站多、盾构调头多等特点,盾构过站是其重要组成部分。盾构过站一般场地狭小、工序繁多,合理的盾构过站,既可节省人力物力,又能保证优质高效地完成工程。结合工程实际,对盾构过站技术进行了较深入的研究。  相似文献   

三维激光扫描仪在道路竣工测量中的应用   总被引：1，自引：1，他引：0  

王星杰 《北京测绘》2012,(4):67-71

三维激光扫描仪在道路竣工测量中的应用相对于常规作业方式极大地提高了作业效率,降低了外业劳动量和劳动强度。由于三维激光扫描仪能够迅速采集大量的点云数据,实景再现了测区的地形地势,相对于传统的作业方法具有无法比拟的优势。全文概略介绍了三维激光扫描技术的工作原理,详细介绍了三维激光扫描技术在道路竣工测量中的内外业作业方法,同时进行了多方面的精度检验,为三维激光扫描技术在其他相关工程中应用的提供了很好的借鉴作用。  相似文献