Tev gamma-ray astronomy in South Africa     

B. Christo Raubenheimer 《Astrophysics and Space Science》1995,230(1-2):263-277

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西太平洋特定海域15万年以来古海洋学研究   总被引：1，自引：0，他引：1  

苍树溪  阎军 《海洋地质与第四纪地质》1993,13(3):97-101

本文是我们近年来对西太平洋特定海域进行古海洋学研究的成果概述和讨论。古海洋学是多学科、综合性边缘科学。主要是通过对海底沉积物所进行的多项分析,包括:稳定同位素地层、地球化学元素地层、古生物地层及气候地层学方法,恢复近15万年以来古海洋环境,诸如古海流、古温度、古盐度、古季风等。  相似文献   

An analysis of a zooplankton sampling-gear change in the CalCOFI long-term monitoring program, with implications for copepod population abundance trends     

Ginger A. Rebstock   《Progress in Oceanography》2002,53(2-4)

The California Cooperative Oceanic Fisheries Investigations (CalCOFI) program has been systematically sampling zooplankton off the west coast of North America since 1949. In 1978, the 1-m diameter ring net used by the program was replaced with a bongo net, which consists of two 0.71-m diameter nets on a single frame. This study compares paired zooplankton samples taken with a ring net and a 0.71-m or 0.6-m bongo net to determine the relative performances of the two net types for catching calanoid copepods. Thirty-one species and stages were enumerated, along with the category ‘total female calanoids’. Twenty-one categories of calanoid copepods were abundant enough to test for effects of changes in net type. No significant differences between the nets were found after correcting for multiple testing. Statistical power was then estimated for a range of potential net effects equivalent to ratios of copepod densities between the nets of 1.1–3.0. The probability of detecting differences greater than a factor of 1.5–3.0 was high (≥80%) for total female calanoids, Metridia pacifica, Pleuromamma abdominalis edentata, P. borealis, Calanus pacificus, Eucalanus californicus and Rhincalanus nasutus. For these categories of copepods, any population changes greater than a factor of 1.5–3.0 that might be found from the CalCOFI data set can be assumed to be the result of factors other than the change in net type.  相似文献   

Growth, feeding, production, and consumption in 0-group bib (Trisopterus luscus L.) and whiting (Merlangius merlangus L.) in a shallow coastal area of the south-west Netherlands     

Hamerlynck  Olivier; Hostens  Kris 《ICES Journal of Marine Science》1993,50(1):81-91

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3≈6 Months Variation of Sea Surface Height in the South China Sea and Its Adjacent Ocean     

Jianyu Hu  Hiroshi Kawamura  Huasheng Hong  Fumiaki Kobashi  Dongxiao Wang 《Journal of Oceanography》2001,57(1):69-78

Sea surface height (SSH) variations with a period of 36 months (SSH36 variations) in the South China Sea (SCS) and its adjacent ocean are intensively investigated using six years of TOPEX/POSEIDON-derived SSH data. The results show that there appears higher energy of SSH36 variations in the east of the Luzon Strait and in some areas of the SCS, both of which are correlated with each other. The SSH36 variations usually propagate westward in the subtropical region of the northern Pacific Ocean and turn northward in the east of the Luzon Strait while they sometimes propagate into the SCS through the Luzon Strait with the phase speed of about 11–12 cm/s, which may be considered as Rossby waves. It can be inferred that the SSH36 variations are strongly associated with current structures and eddies in the SCS because of their significant intensiveness. The SSH variations with the period of 6 months are more dominant than those with the other periods in the SCS.  相似文献   

Seafloor electromagnetic induction studies in the Bay of Bengal     

Joseph  E. John  Toh  H.  Fujimoto  H.  Iyengar  R.V.  Singh  B.P.  Utada  H.  Segawa  J. 《Marine Geophysical Researches》2000,21(1-2):1-21

Seafloor magnetometer array experiments were conducted in the Bay of Bengal to delineate the subsurface conductivity structure in the close vicinity of the 85°E Ridge and Ninety East Ridge (NER), and also to study the upper mantle conductivity structure of the Bay of Bengal. The seafloor experiments were conducted in three phases. Array 1991 consisted of five seafloor stations across the 85°E Ridge along 14°N latitude with a land reference station at Selam (SLM). Array 1992 also consisted of five seafloor stations across 85°E Ridge along 12°N latitude. Here we used the data from Annamalainagar Magnetic Obervatory (ANN) as land reference data. Array 1995 consisted of four seafloor stations across the NER along 9°N latitude with land reference station at Tirunelveli (TIR). OBM-S4 magnetometers were used for seafloor measurements. The geomagnetic Depth Sounding (GDS) method was used to investigate the subsurface lateral conductivity contrasts. The vertical gradient sounding (VGS) method was used to deliniate the depth-resistivity structure of the oceanic crust and upper mantle. 1-D inversion of the VGS responses were conducted and obtained a 3-layer depth-resistivity model. The top layer has a resistivity of 150–500 m and a thickness of about 15–50 km. The second layer is highly resistive (2000–9000 m) followed by a very low resistive (0.1–50 m) layer at a depth of about 250–450 km. The 3-component magnetic field variations and the observed induction arrows indicated that the electromagnetic induction process in the Bay of Bengal is complex. We made an attempt to solve this problem numerically and followed two approaches, namely (1) thin-sheet modelling and (2) 3-D forward modelling. These model calculations jointly show that the observed induction arrows could be explained in terms of shallow subsurface features such as deep-sea fans of Bay of Bengal, the resistive 85°E Ridge and the sea water column above the seafloor stations. VGS and 3-D forward model responses agree fairly well and provided depth-resistivity profile as a resistive oceanic crust and upper mantle underlained by a very low resistive zone at a depth of about 250–400 km. This depth-range to the low resistive zone coincide with the seismic low velocity zone of the northeastern Indian Ocean derived from the seismic tomography. Thus we propose an electrical conductivity structure for the oceanic crust and upper mantle of the Bay of Bengal.  相似文献   

海洋污染对毛蚶超氧化物歧化酶影响的研究   总被引：17，自引：0，他引：17       下载免费PDF全文

赵元凤  吕景才  李丹彤  刘长发  常亚青  侯美艳  潘德建  宋晓阳  孙静 《海洋学报》2003,25(3):77-82

采用体内、体外染毒实验,研究了海洋中常见污染物0＃柴油、二甲苯以及重金属镉离子(Cd2+)对毛蚶(Scapharca subcrenata)肌肉超氧化物歧化酶(SOD)活性的影响.结果表明,在实验剂量范围内,3种污染物对毛蚶肌肉中SOD均表现出不同程度诱导作用;0＃柴油和二甲苯体内、体外染毒对毛蚶SOD活性影响规律基本一致,这两种污染物对毛蚶SOD活性变化的剂量-效应曲线均为抛物线型;Cd2+在体内、体外染毒对毛蚶肌肉SOD活性诱导曲线均不呈抛物线型,低浓度Cd2+对毛蚶SOD活性表现为显著诱导,随后曲线迅速下降,表明毛蚶对Cd2+污染反应十分敏感,也表明Cd2+对毛蚶毒性作用较强,3种毒物对毛蚶的毒性强弱次序为,Cd2+,0＃柴油、二甲苯.  相似文献   

Comparison of atmospheric forcing in four sub-arctic seas     

Muyin Wang  Nicholas A. Bond  James E. Overland 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2543

A comparative analysis was conducted on climate variability in four sub-arctic seas: the Sea of Okhotsk, the Bering Sea shelf, the Labrador Sea, and the Barents Sea. Based on data from the NCEP/NCAR reanalysis, the focus was on air–sea interactions, which influence ice cover, ocean currents, mixing, and stratification on sub-seasonal to decadal time scales. The seasonal cycles of the area-weighted averages of sea-level pressure (SLP), surface air temperature (SAT) and heat fluxes show remarkable similarity among the four sub-arctic seas. With respect to variation in climate, all four seas experience changes of comparable magnitude on interannual to interdecadal time scales, but with different timing. Since 2000 warm SAT anomalies were found during most of the year in three of the four sub-arctic seas, with the exception of the Sea of Okhotsk. A seesaw (out of phase) pattern in winter SAT anomalies between the Labrador and the Barents Sea in the Atlantic sector is observed during the past 50 years before 2000; a similar type of co-variability between the Sea of Okhotsk and the Bering Sea shelf in the Pacific is only evident since 1970s. Recent positive anomalies of net heat flux are more prominent in winter and spring in the Pacific sectors, and in summer in the Atlantic sectors. There is a reduced magnitude in wind mixing in the Sea of Okhotsk since 1980, in the Barents Sea since 2000, and in early spring/late winter in the Bering Sea shelf since 1995. Reduced sea-ice areas are seen over three out of four (except the Sea of Okhotsk) sub-arctic seas in recent decades, particularly after 2000 based on combined in situ and satellite observations (HadISST). This analysis provides context for the pan-regional synthesis of the linkages between climate and marine ecosystems.  相似文献   

华北地区8级大震的深部构造特征及地震成因的探讨c          下载免费PDF全文

张先  张先康  刘敏  赵丽 《地震学报》2003,25(2):136-142

在地震地质、航磁反演及人工地震测深工作的基础上，阐明了华北地区8级大震的3个深部构造特征，即地震发生在深部超壳断裂的上部，地震发生在强度较大的构造块体的边缘，震源区深部存在低速、低密及高导层构造．同时对地震成因进行了探讨，讨论了构造运动和壳内爆炸两种地震成因的可能．   相似文献   

218P₀测深法寻找基岩地下水实用研究          下载免费PDF全文

李惠恩  桑运秀  侯士德  王景荣  王东锋 《水科学进展》2003,14(2):213-217

阐明了一种新的找水方法——218P₀测深法。对其操作过程和根据实测曲线识别含水层、确定含水层数、分析富水性,以及计算含水层底板埋深的方法作了分析,并对有关机理作了初步探讨。  相似文献