Hydrothermal Vent Geology and Biology at Earth’s Fastest Spreading Rates     

Richard N. Hey  Gary J. Massoth  Robert C. Vrijenhoek  Peter A. Rona  John Lupton  David A. Butterfield 《Marine Geophysical Researches》2006,27(2):137-153

Earth’s fastest present seafloor spreading occurs along the East Pacific Rise near 31°–32° S. Two of the major hydrothermal plume areas discovered during a 1998 multidisciplinary geophysical/hydrothermal investigation of these mid-ocean ridge axes were explored during a 1999 Alvin expedition. Both occur in recently eruptive areas where shallow collapse structures mark the neovolcanic axis. The 31° S vent area occurs in a broad linear zone of collapses and fractures coalescing into an axial summit trough. The 32° S vent area has been volcanically repaved by a more recent eruption, with non-linear collapses that have not yet coalesced. Both sites occur in highly inflated areas, near local inflation peaks, which is the best segment-scale predictor of hydrothermal activity at these superfast spreading rates (150 mm/yr).  相似文献   

Sensitivity of a global ocean model to increased run-off from Greenland   总被引：2，自引：0，他引：2  

Rüdiger Gerdes  William Hurlin  Stephen M. Griffies 《Ocean Modelling》2006,12(3-4):416-435

We study the reaction of a global ocean–sea ice model to an increase of fresh water input into the northern North Atlantic under different surface boundary conditions, ranging from simple restoring of surface salinity to the use of an energy balance model (EBM) for the atmosphere. The anomalous fresh water flux is distributed around Greenland, reflecting increased melting of the Greenland ice sheet and increasing fresh water export from the Arctic Ocean. Depending on the type of surface boundary condition, the large circulation reacts with a slow-down of overturning and gyre circulations. Restoring of the total or mean surface salinity prevents a large scale redistribution of the salinity field that is apparent under mixed boundary conditions and with the EBM. The control run under mixed boundary conditions exhibits large and unrealistic oscillations of the meridional overturning. Although the reaction to the fresh water flux anomaly is similar to the response with the EBM, mixed boundary conditions must thus be considered unreliable. With the EBM, the waters in the deep western boundary current initially become saltier and a new fresh water mass forms in the north-eastern North Atlantic in response to the fresh water flux anomaly around Greenland. After an accumulation period of several decades duration, this new North East Atlantic Intermediate Water spreads towards the western boundary and opens a new southward pathway at intermediate depths along the western boundary for the fresh waters of high northern latitudes.  相似文献   

Spatial and temporal variability of microplankton and detritus, and their export to the shelf sediments in the upwelling area off Concepción, Chile (∼36°S), during 2002-2005     

Humberto E. González  Eduardo Menschel  Carola Aparicio 《Progress in Oceanography》2007,75(3):435-451

Seasonal variations in diversity and biomass of diatoms, tintinnids, and dinoflagellates and the contribution of microplankton and faecal material to the vertical flux of particulates were investigated at one time series station T (station 18) between 2002 and 2005 and at a grid of stations during November 2004 in the coastal and oceanic area off Concepción (36°S), Chile. The variations were analysed in relation to water column temperature, dissolved oxygen, nutrient concentration, offshore Ekman transport, and chlorophyll-a concentration. Abundance was estimated as cell numbers per litre and biomass in terms of biovolume and carbon units.A sharp decrease with depth was observed in the abundance of both phytoplankton and microzooplankton during the whole annual cycle; over 70% of their abundance was concentrated in the upper 10 m of the water column. Also, a clear seasonality in microplankton distribution was observed at station T, with maxima for diatoms, tintinnids, and dinoflagellates every summer (centred on January) from 2002 to 2005.On the grid of stations, the maximum integrated (0-50 m) micro-phytoplankton abundances (>1 × 10⁹ cells m⁻²) occurred at the coastal stations, an area directly influenced by upwelling. A similar spatial distribution was observed for the integrated (0-200 m) faecal carbon (with values up to 632 mg C m⁻²). Tintinnids were distributed in all the first 300 miles from the coast and dinoflagellates were more abundant in oceanic waters.At station T, the average POC export production (below 50 m depth) was 16.6% (SD = 17%; range 2-67%; n = 16). The biological-mediated fluxes of carbon between the upper productive layer and the sediments of the continental shelf off Concepción depend upon key groups of phytoplankton (Thalassiosira spp., Chaetoceros spp.) and zooplankton (euphausiids) through the export of either cells or faecal material, respectively.  相似文献   

西太平洋暖池区海—气通量计算分析   总被引：4，自引：0，他引：4  

徐天真  陈伯海 《中国海洋大学学报(自然科学版)》1993,(Z2)

用J.Launiaimen和T.Vihma提出的近地面层湍流通量计算方法,对我国在1992年11月至1993年2月TOGA—COARE—IOP实验中所获资料计算处理。得出所在站位的海一气间显效、潜热及动量通量。指出西大平洋暖池海区游热通量与显效通量之比为10.14:1;风速大于8m/s后各通量随风速的变化率明显增加;动量与热量的块体通量系数Cd和Ce,h随风速变化有相似的规律;Monin—Obukhov大气稳定度参数Z/L与△T/U_(10)之间有较好的统计关系。  相似文献   

南黄海夏季海水pCO2研究Ⅱ--下层海水涌升和长江冲淡水对海-气界面CO2通量的贡献     

江春波  张龙军  王峰 《中国海洋大学学报(自然科学版)》2006,36(Z1):147-152

根据2001年7月对南黄海的大面积调查,研究了南黄海夏季pCO2的分布机制,着重讨论下层海水涌升和长江冲淡水对海-气界面CO2通量的贡献,并给出了南黄海海-气界面CO2通量。研究结果表明:夏季南黄海总体上是CO2的1个弱源,大约向大气中释放45.05×104t C。夏季南黄海表层海水pCO2分布表现出了极大的不均性,其汇区主要由长江冲淡水造成,影响区域占汇区吸收CO2的99.9%;而在源区,下层海水涌升虽然面积较小却占源区释放CO2的35.2%。可见陆架边缘海区源/汇格局的地域差异非常之特别。  相似文献   

长江中下游6月份降水的一个预报指标     

赵永平  陈永利 《海洋科学》1995,19(1):39-42

根据１９６３－１９９２年嵊山海洋站２月海气感热输送和２２ａ太阳磁周期与降水的关系，提出了一个长江中下游６月降水的综合预报指标，用此指标，对１９９３年６月长江中下游降水进行回报，结果与实况一致。  相似文献   

台湾海峡海流结构及海水通量     

傅子琅  胡建宇 《热带海洋学报》1995,(3)

主要根据台湾海峡的实测海流资料，以夏、冬为代表季节，分析了台湾海峡２—３个纬向断面的海流结构，计算出各断面的海水通量。结果表明：夏季，台湾海峡中、北部海域各层的海流一般偏Ｎ向流动，Ｎ向的海水净通量为３．３２×１０６ｍ３·ｓ－１；冬季，高温高盐的黑潮水和南海水由南向北经南部断面进入台湾海峡，其海水通量分别为１．６９×１０６ｍ３·ｓ－１和０．５９×１０６ｍ３·ｓ－１；而东海水由北向南通过北部断面进入台湾海峡，其海水通量为１．０２×１０６ｍ３·ｓ－１，其中，有０．４０×１０６ｍ３·ｓ－１的海水沿着福建和广东近岸流进南海，其余０．６２×１０６ｍ３·ｓ－１的海水在台湾海峡北部混合后随同黑潮水和南海水流入东海。总之，流经台湾海峡的Ｎ向海水净通量为１．７４×１０６ｍ３·ｓ－１。  相似文献   

Chemical Fluxes of Asian Rivers into Oceans and their Controlling Factors     

杨守业  李从先  刘曙光 《海洋通报(英文版)》2001,3(2)

Chemical fluxes of Asian rivers into oceans bear different regional variations. Three zones are characteristic of distinct dissolved sediment loads and yields and ionic concentration.Rivers into oceans in China play an important role in Asia because of their different chemical fluxes, among which those draining the Loess Plateau have high ionic concentration, low water discharges and dissolved sediment loads and yields.Climate, vegetation, soil and strata lithology, chemical weathering intensity and tectonic activity dominate chemical fluxes of Asian rivers into oceans, and different factors have different effects on the chemical fluxes of separate regional rivers. Rising of the Tibet Plateau also exerts an important influence on chemical compositions of rivers originating from it.  相似文献   

九龙江流域水葫芦打捞去除水体营养盐模型研究   总被引：1，自引：0，他引：1  

陈彬  赵由才  王金坑 《台湾海峡》2007,26(3):327-333

水葫芦被收获时,水体中的营养盐也将包含在植物组织中而被去除.本研究首先通过野外实验和参考国内外有关文献,建立了九龙江流域水葫芦生长数学模型和持续生产模型,确定了模型的各有关参数:水葫芦生长容量K值为25.6 kg/m2、最大生长速率rmax为0.12d-1;水体中氮和磷的半饱和系数hN和hP值分别为0.2和0.03;水葫芦最低生长温度(mθin)为7℃,最适水温(oθpt)为30℃,最高生长温度(θmax)为40℃.随后采用所建立的模型计算了研究区水葫芦打捞的营养盐去除效果,研究区面积6 000m2的水体实施水葫芦打捞策略后,1a所能收获的水葫芦最大产量为9.18×105kg,去除的TP为214.4kg,TN为966.6kg.  相似文献   

WATER MASS FORMATION IN THE SOUTH INDIAN OCEAN BY AIR-SEA FLUXES     

Ming Feng 《热带海洋学报》2004,23(6):16-21

1Introduction　TheIndianCentralWater (ICW) ,formedandsubductedintheSubtropicalConvergenceintheSouthIndianOcean ,occupiesasignificantportionofthethermoclineintheIndianOcean[1,2 ]　 (Fig .1 ) .TheSubantarcticModeWater(SAMW)isformedinthe 2 6.5-2 7.1σθrangenorthoftheSub antarcticFront—thesouthernboundaryofthesubtropicalgyres[3]　 .InthesoutheastIndianO cean ,theSAMWisthethickest,ventilatedasathicklayerofhighoxygenextendingtothetropicalIndianOcean[4 ,5 ]　 .　Watermasstransformation…  相似文献