Seasonal Variation of Stratification in the Gulf of Thailand     

Tetsuo Yanagi  Suhendar I Sachoemar  Toshiyuki Takao  Shunji Fujiwara 《Journal of Oceanography》2001,57(4):461-470

Intensive hydrographic observations were carried out in the western part of the Gulf of Thailand and the east coastal sea of Peninsular Malaysia in September 1995 and April–May 1996. The characteristics of seasonal variation of oceanic condition in that area are discussed basis of an analysis of observed water temperature, salinity and density distributions in these cruises and NAGA cruises (Yanagi and Takao, 1998a). Stratification is most developed in March–May mainly due to large sea surface heating and weak sea surface wind, which weakened until September–October, vanishing in December–January. The horizontal distribution of bottom cold, saline and heavy water masses, which are found during the stratified season, is governed by the tidal mixing and the water depth. Water exchange between the Gulf of Thailand and the South China Sea becomes large in March–May due to a coupled effect of the intensified estuarine circulation and the Ekman transport by the southwest monsoon. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Using trace elements in skin to discriminate the populations of minke whales in southern hemisphere     

Kunito T  Watanabe I  Yasunaga G  Fujise Y  Tanabe S 《Marine environmental research》2002,53(2):175-197

Concentrations of 12 trace elements (V, Cr, Mn, Cu, Zn, Se, Rb, Sr, Cd, Cs, Ba, and Hg) were determined in liver and skin tissues of minke whales from various regions within the Antarctic Ocean. Cd concentrations in livers of southern minke whale were apparently higher than those in cetaceans from other regions, while Hg concentrations were lower. There were significant positive correlations between body length and concentrations of Cd and Hg in the liver. The concentrations of all trace elements in the skin were lower than those in other cetaceans reported previously. Significant positive correlations between liver and skin were found for Cr, Mn, Cu, Zn, Rb, Cd, and Cs, implying that the concentrations of these trace elements in the skin reflect those of internal organs. Large interannual variation of the accumulation pattern of trace elements in the skin was observed for the southern minke whales from Area V. There were significant differences in the skin element concentrations among Areas III, IV, and V, especially for males. Also, discriminant analysis between geographically two different groups collected during 1995/1996 austral summer season, based on the concentrations of trace elements in the skin, allowed for a correct classification of 90% of these minke whales. These results suggest that measurement of trace elements in skin samples could provide valuable information on the status of contamination and possible geographic differences in the accumulation levels in southern minke whales.  相似文献   

hoxY基因的克隆及其在节旋藻和螺旋藻系统学研究的应用     

张晓辉  隋正红  张学成 《中国海洋大学学报(自然科学版)》2005,35(6):1021-1025

从节旋藻属5个品系和螺旋藻属1个品系中克隆了hoxY基因的部分序列.序列长度都是479bp.在节旋藻中该基因GC含量为46.0%～46.6%,螺旋藻中为43.5%.节旋藻各品系间序列的相似性介于93.7%～100%,明显高于节旋藻属和螺旋藻属间的序列相似性（69.5%～72.2%）.2个属中镍铁氢化酶小亚基HoxY氨基酸序列的比较也表明螺旋藻和节旋藻之间存在较大差异.利用MEGA2通过比较核酸序列构建了系统树,表明螺旋藻和节旋藻属处于不同的分枝.  相似文献   

Carbon dioxide in surface seawaters of the Seto Inland Sea,Japan     

Eiji Ohtaki  Eiji Yamashita  Fukuichi Fujiwara 《Journal of Oceanography》1993,49(3):295-303

Observations were made of time variations of carbon dioxide in seawater, pCO₂, and in the atmosphere, PCO₂, in the Seto Inland Sea of Japan. The pCO₂ data showed well defined diurnal variation; high values at nighttime and low values during daylight hours. The pCO₂ correlated negatively with dissolved oxygen. These results denote that the diurnal variation of pCO₂ is associated with effects of photoplankton's activity in seawater. The pCO₂ measured in the Seto Inland Sea showed higher values than the PCO₂ during June to November, denoting transport of carbon dioxide from the sea surface to the atmosphere, and lower values during December to May, denoting transport of carbon dioxide from the atmosphere to the sea surface. The exchange rates of carbon dioxide were calculated using working formula given by Andriéet al. (1986). The results showed that the Seto Inland Sea gained carbon dioxide of 1.0 m-mol m^–2 d^–1 from the atmosphere in March and lost 1.7 m-mol m^–2 d^–1 to the atmosphere in August.  相似文献   

Formation of sand banks due to tidal vortices around straits     

Yoshio Takasugi  Tateki Fujiwara  Takashige Sugimoto 《Journal of Oceanography》1994,50(1):81-98

Sand banks around straits are used as a commercial fishing ground. In order to clarify the mechanism of sand bank formation, the Lagrangian method was used to measure currents and turbidity around the banks in the Neko Seto Sea in the Seto Inland Sea of Japan. A neutrally buoyant float released in the Neko Seto Strait at the maximum tidal flow stage was engulfed in a pair of tidal vortices and moved around one of the sand banks. The vertical distribution of turbidity, which was measured by the vessel moving with the neutral float, showed an extremely high turbidity in the bottom layer of this bank area. According to the analysis of these observational data, the process of sand bank formation around straits is as follows. The tidal vortex transports water mass with suspended materials (including sand) which are whirled up at the bottom by the tidal jet. In the decaying stage of the vortex, the materials in the bottom layer are gathered in the central part of the vortex by the secondary convergent flow in the vortex. Among these materials, a large-size sand particle with a high critical erosion velocity accumulates at the bottom and forms banks. The distribution of bottom sediment and the thickness of alluvium support this result.  相似文献   

Response of plant growth to surface water balance during a summer dry period in the Kazakhstan steppe     

Yoshihiro Iijima  Tsuneo Kawaragi  Takehiko Ito  Kanat Akshalov  Atsushi Tsunekawa  Masato Shinoda 《水文研究》2008,22(16):2974-2981

In drylands, water deficit is the primary factor limiting plant growth. In the present study, surface energy balance and plant growth (above‐ground and below‐ground biomass) were measured continuously during the 2002 growing season in semiarid grassland in the northern part of Kazakhstan, Central Asia. Although there was above normal total rainfall during the 2002 growing season (May–November; 244 mm over 183 days), there was a dry period during July and August. Evaporative water was effectively supplied by precipitation and surface soil moisture during the wet season (May and June), during which time above‐ground biomass increased. During the early stages of the dry period, mature plants were likely to tap deeper sources of soil moisture, representing stored snowmelt water. As the soil moisture content decreased during the summer dry period due to the high levels of evapotranspiration and lack of precipitation, the evaporative fraction and above‐ground biomass rapidly decreased, whereas the below‐ground biomass increased. These results suggest that in summer, soil moisture acts to store water, and that soil moisture is essential for plant growth as a direct source of water during the dry period in natural grasslands in the Kazakhstan steppe. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Accelerated continental-scale snowmelt and ecohydrological impacts in the four largest Siberian river basins in response to spring warming     

Kazuyoshi Suzuki  Tetsuya Hiyama  Koji Matsuo  Kazuhito Ichii  Yoshihiro Iijima  Dai Yamazaki 《水文研究》2020,34(19):3867-3881

River runoff from the four largest Siberian river basins (the Ob, Yenisei, Lena, and Kolyma) considerably contributes to freshwater flux into the Arctic Ocean from the Eurasian continent. However, the effects of variation in snow cover fraction on the ecohydrological variations in these basins are not well understood. In this study, we analysed the spatiotemporal variability of the maximum snow cover fraction (SCF_max) in the four Siberian river basins. We compared the SCF_max from 2000 to 2016 with data in terms of monthly temperature and precipitation, night-time surface temperatures, the terrestrial water storage anomaly (TWSA), the normalised difference vegetation index (NDVI), and river runoff. Our results exhibit a decreasing trend in the April SCF_max values since 2000, largely in response to warming air temperatures in April. We identified snowmelt water as the dominant control on the observed increase in the runoff contribution in May across all four Siberian river basins. In addition, we detected that the interannual river runoff was predominantly controlled by interannual variations in the TWSA. The NDVI in June was strongly controlled by the timing of the snowmelt along with the surface air temperature and TWSA in June. The rate of increase in the freshwater flux from the four Siberian rivers decreased from 2000 to 2016, exhibiting large interannual variations corresponding to interannual variations in the TWSA. However, we identified a clear increase trend in the freshwater flux of ~4 km³/year when analysing the long-term 39-year historical record (1978–2016). Our results suggest that continued global warming will accelerate the transition towards the earlier timing of snowmelt and spring freshwater flux into the Arctic Ocean. Our findings also highlight the effects of earlier snowmelt on ecohydrological changes in the Northern Hemisphere.  相似文献   

QSAT: The Satellite for Polar Plasma Observation     

Yoshihiro Tsuruda  Akiko Fujimoto  Naomi Kurahara  Toshiya Hanada  Kiyohumi Yumoto  Mengu Cho 《Earth, Moon, and Planets》2009,104(1-4):349-360

This paper introduces QSAT, the satellite for polar plasma observation. The QSAT project began in 2006 as an initiative by graduate students of Kyushu University, and has the potential to contribute greatly to IHY (International Heliophysical Year) by showing to the world the beauty, importance, and relevance of space science. The primary objectives of the QSAT mission are (1) to investigate plasma physics in the Earth’s aurora zone in order to better understand spacecraft charging, and (2) to conduct a comparison of the field-aligned current observed in orbit with ground-based observations. The QSAT project can provide education and research opportunities for students in an activity combining space sciences and satellite engineering. The QSAT satellite is designed to be launched in a piggyback fashion with the Japanese launch vehicle H-IIA. The spacecraft bus is being developed at the Department of Aeronautics and Astronautics of Kyushu University with collaboration of Fukuoka Institute of Technology. Regarding the payload instruments, the Space Environment Research Center of Kyushu University is developing the magnetometers, whereas the Laboratory of Spacecraft Environment Interaction Engineering of Kyushu Institute of Technology is developing the plasma probes. We aim to be ready for launch in 2009 or later.  相似文献   

Temporal changes in tree-ring nitrogen of Pinus thunbergii trees exposed to Black-tailed Gull (Larus crassirostris) breeding colonies     

Lopez C.M. Larry  Mizota Chitoshi  Yamanaka Toshiro  Nobori Yoshihiro 《Applied Geochemistry》2010

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Large-Scale Mapping Observations of the C i (3P1-3P0) and CO (J = 3-2) Lines toward the Orion A Molecular Cloud     

Ikeda M  Maezawa H  Ito T  Saito G  Sekimoto Y  Yamamoto S  Tatematsu K  Arikawa Y  Aso Y  Noguchi T  Shi SC  Miyazawa K  Saito S  Ozeki H  Fujiwara H  Ohishi M  Inatani J 《The Astrophysical journal》1999,527(1):L59-L62

Large-scale mapping observations of the 3P1-3P0 fine-structure transition of atomic carbon (C i, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mount Fuji submillimeter-wave telescope. The observations cover 9 deg2 and include the Orion Nebula M42 and the L1641 dark cloud complex. The C i emission extends over almost the entire region of the Orion A cloud and is surprisingly similar to that of 13CO (J=1-0). The CO (J=3-2) emission shows a more featureless and extended distribution than C i. The C i/CO (J=3-2) integrated intensity ratio shows a spatial gradient running from the north (0.10) to the south (1.2) of the Orion A cloud, which we interpret as a consequence of the temperature gradient. On the other hand, the C i/13CO (J=1-0) intensity ratio shows no systematic gradient. We have found a good correlation between the C i and 13CO (J=1-0) intensities over the Orion A cloud. This result is discussed on the basis of photodissociation region models.  相似文献