Bottom water temperature measurements in the South China Sea,eastern Indian Ocean and western Pacific Ocean

文章报道了一批新的海底底水温度(BWT)数据,其中南海(SCS)158个站位、东印度洋(EIO)30个站位及西太平洋(WPO)37个站位。基于这批新的BWT数据,获得南海和西太平洋海域底水温度与水深经验关系,可为地球物理和物理海洋提供准确、可靠的海底温度边界。这将有助于海底油气资源调查与评估。同时,这批实测数据表明:1)水深超过3500m的海域,其底水温度在南海约为2.47℃,比东印度洋(～1.34℃)和西太平洋(～1.60℃)稍微偏高。这与大洋传送带模式所预测的情况比较吻合。该模式认为:低温高盐的海水,从北大西洋格陵兰岛和冰岛附近海域下沉到深层,然后向南流动,再与南极洲周围海域的低温高盐海水一同向北进入印度洋和太平洋。而南海是一个相对比较封闭的热带边缘海,其内部海水与印度洋和菲律宾海交换有限,导致海水温度整体高于印度洋和太平洋。2)台西南盆地水深在2700～3000m的部分站位,其底水温高达约3.00℃,明显高于其周边同水深海域底水温度(平均值约为2.33℃)。这可能是台西南盆地海底水热活动导致的结果。3)在东印度洋和西太平洋水深超过4800m海域,底水温度随着水压增大稍有升高,其升高率分别为10.6mK·MPa~(-1)和12.0mK·MPa~(-1)。这与理论估算的深层底水绝热压力温度梯度范围较为吻合。这也意味着东印度洋和西太平洋深层底水,主要由绝热自压作用导致其温度随着深度的增大而升高。     

印度洋海表温度的变化及其对印度夏季季风降水影响的诊断研究

对印度洋海表温度(SST)的主要特征及变化趋势进行分析,并研究了其与印度夏季季风降水(ISMR)和季风环流的关系,揭示出:从北印度洋到南半球中高纬度印度洋,SST最显著的变化模态是全海盆一致的变化,近50 a来总体趋势是上升的,在1976,1986年以及1996年间分别有一次跳跃性增温,与太平洋SST变化趋势基本一致.除了长期变化趋势外,南印度洋中高纬度比热带地区有更显著的模态分布.在印度洋SST升温的背景下,ISMR具有逐渐减少的趋势,但两者相关较弱.印度洋SST发生跳跃后的不同阶段,许多海区SST与ISMR相关均发生变化,但在春季,热带外南印度洋具有一对相对稳定区,其分布与EOF分析的第2模态相似.根据它们的分布,文中定义了春季南半球偶极子(SIOD),在正SIOD(PSIOD)情况下印度降水偏多,而负SIOD(NSIOD)则反之.环流分析表明,PSIOD(NSIOD)通过与大气的相互作用,对夏季马斯克林高压具有增强(减弱)作用,进而使得索马里越赤道气流增强(减弱),在印度地区低空产生异常的辐合(辐散),高层辐散(辐合),从而影响印度季风环流,使得印度季风降水偏多(少).     

普里兹湾附近绕极深层水和底层水及其运动特征

利用中国第15次南极科学考察科学考察队的CTD全深度观测资料(1998年11月至1999年2月),分析并讨论了普里兹湾以北的南大洋海域内,绕极深层水(CDW)和南极底层水(AABW)的物理特性及其空间分布.同时还与历史上其他学者的发现进行了比较.指出了在研究海域内,CDW在100～2000m之间从北向南扩展,其高温核(t>1.2℃)和高盐核(S>34.7)在75°E断面上最为深厚,向南扩展得最远;而AABW则在2500m以深由陆坡底部向北扩展,σ_θ>27.875的高密度水体在70°E断面上最为深厚,向北扩展得最远.此外还通过实测的CTD资料证实了CDW和AABW的经向环流特征,以及它们与迪肯流环(Deaconcell)、亚极地流环和深层流环的一致性.     

Contraction and warming of Antarctic Bottom Water in the Amundsen Sea

Antarctic Bottom Water（AABW） plays an important role in the meridional overturning circulation and contributes significantly to global heat transport and sea level rise（SLR）. Based on the Global Ocean（1/12）°Physical Reanalysis（GLORYS12V1） products and conductivity-temperature-depth instrument data from the World Ocean Circulation Experiment hydrographic program, we analyzed the trends in the thickness, volume,temperature, salinity, and neutral density of the AABW in the Amundsen Sea from 1993 to...     

Frontal structure and Antarctic Bottom Water flow through the Princess Elizabeth Trough,Antarctica

Hydrographic, current meter and ADCP data collected during two recent cruises in the South Indian Ocean (RRS Discovery cruise 200 in February 1993 and RRS Discovery cruise 207 in February 1994) are used to investigate the current structure within the Princess Elizabeth Trough (PET), near the Antarctic continent at 85°E, 63–66°S. This gap in topography between the Kerguelen Plateau and the Antarctic continent, with sill depth 3750 m, provides a route for the exchange of Antarctic Bottom Water between the Australian–Antarctic Basin and the Weddell–Enderby Basin. Shears derived from ADCP and hydrographic data are used to deduce the barotropic component of the velocity field, and thus the volume transports of the water masses. Both the Southern Antarctic Circumpolar Current Front (SACCF) and the Southern Boundary of the Antarctic Circumpolar Current (SB) pass through the northern PET (latitudes 63 to 64.5°S) associated with eastward transports. These are deep-reaching fronts with associated bottom velocities of several cm s^-1. Antarctic Bottom water (AABW) from the Weddell–Enderby Basin is transported eastwards in the jets associated with these fronts. The transport of water with potential temperatures less than 0°C is 3 (±1) Sv. The SB is shown to meander in the PET, caused by the cyclonic gyre immediately west of the PET in Prydz Bay. The AABW therefore also meanders before continuing eastwards. In the southern PET (latitudes 64.5 to 66°S) a bottom intensified flow of AABW is observed flowing west. This AABW has most likely formed not far from the PET, along the Antarctic continental shelf and slope to the east. Current meters show that speeds in this flow have an annual scalar mean of 10 cm s^-1. The transport of water with potential temperatures less than 0°C is 20 (±3) Sv. The southern PET features westward flow throughout the water column, since the shallower depths are dominated by the flow associated with the Antarctic Slope Front. Including the westward flow of bottom water, the total westward transport of the whole water column in the southern PET is 45 (±6) Sv.     

Fronts, baroclinic transport, and mesoscale variability of the Antarctic Circumpolar Current in the southeast Indian Ocean

Fronts,baroclinic transport,and mesoscale variability of the Antarctic Circumpolar Current(ACC) along 115°E are examined on the basis of CTD data from two hydrographic cruises occupied in 1995 as a part of the World Ocean Circulation Experiment(WOCE cruise I9S) and in 2004 as a part of CLIVAR/CO2 repeat hydrography program.The integrated baroclinic transport across I9S section is(97.2×106±2.2×106) m3/s relative to the deepest common level(DCL).The net transport at the north end of I9S,determined by the south Australian circulation system,is about 16.5×106m3/s westward.Relying on a consistent set of water mass criteria and transport maxima,the ACC baroclinic transport,(117×106 ±6.7×10 6)m3/s to the east,is carried along three fronts:the Subantarctic Front(SAF) at a mean latitude of 44°-49°S carries(50.6×10 6 ±13.4×106)m3/s;the Polar Front(PF),with the northern branch(PF-N) at 50.5°S and the southern branch(PFS) at 58°S,carries(51.3×106 ±8.7×106)m3/s;finally,the southern ACC front(SACCF) and the southern boundary of the ACC(SB) consist of three cores between 59°S and 65°S that combined carry(15.2×106 ±1.8×106)m3/s.Mesoscale eddy features are identifiable in the CTD sections and tracked in concurrent maps of altimetric sea level anomalies(SLA) between 44°-48°S and 53°-57°S.Because of the remarkable mesoscale eddy features within the SAF observed in both the tracks of the cruises,the eastward transport of the SAF occurs at two latitude bands separating by 1°.Both the CTD and the altimetric data suggest that the mesoscale variability is concentrated around the Antarctic Polar Frontal Zone(APFZ) and causes the ACC fronts to merge,diverge,and to fluctuate in intensity and position along their paths.     

西南印度洋中脊超慢速扩张的构造和岩浆活动特征

西南印度洋中脊是当前研究超慢速扩张中脊岩石圈增生模式和热液硫化物矿产资源的热点区域.本研究从西南印度洋中脊的扩张速率变化与全球地质历史事件的关系、岩浆活动强度及其不同尺度上的运移规律、热点-中脊交互作用的地质现象和地球物理特征等方面,系统总结了有关西南印度洋中脊的最新认识.针对以上内容,提出了进一步工作建议,如调查航次的区域与方法、岩浆-构造活动与岩石圈状态的相互关系以及热点-中脊交互作用的动力学机制.     

热带印度洋海温异常与ENS0关系的进一步研究

用1955年1月-2001年12月美国Scripps海洋研究所的海温再分析资料、美国NCEP再分析资料和美国气候预测中心(CPC)资科,讨论了热带太平洋ENSO与热带印度洋海温距平以及与印度洋儡极子(Dipole)的关系,研究结果发现:在垂直最大温度距平曲面(MTAL)上,热带印度洋海温距平分布存在着与热带太平洋ENS...     

Dianeutral mixing,transformation and transport of Antarctic Intermediate Water in the South Atlantic Ocean

Recently obtained World Ocean Circulation Experiment (WOCE) sections combined with a specially prepared pre-WOCE South Atlantic data set are used to study the dianeutral (across neutral surface) mixing and transport achieving Antarctic Intermediate Water (AAIW) being transformed to be part of the North Atlantic Deep Water (NADW) return cell. Five neutral surfaces are mapped, encompassing the AAIW from 700 to 1100 db at the subtropical latitudes.Coherent and significant dianeutral upwelling is found in the western boundary near the Brazil coast north of the separation point (about 25°S) between the anticyclonic subtropical and cyclonic south equatorial gyres. The magnitude of dianeutral upwelling transport is 10^-3 Sv (1 Sv=10⁶ m³ s^-1) for 1°×1° square area. It is found that the AAIW sources from the southwestern South Atlantic and southwestern Indian Ocean do not rise significantly into the Benguela Current. Instead, they contribute to the NADW return formation by dianeutral upwelling into the South Equatorial Current. In other words, the AAIW sources cannot obtain enough heat/buoyancy to rise until they return to the western boundary region but north of the separation point. The basin-wide integration of dianeutral transport shows net upward transports, ranging from 0.25 to 0.6 Sv, across the lower and upper boundary of AAIW north of 40°S. This suggests that the equatorward AAIW is a slow rising water on a basin average. Given one order of uncertainty in evaluating the along-neutral-surface and dianeutral diffusivities from the assumed values, K=10³ m² s^-1 and D=10^-5 m² s^-1, the integrated dianeutral transport has an error band of about 10–20%. The relatively weak integrated dianeutral upwelling transport compared with AAIW in other oceans implies much stronger lateral advection of AAIW in the South Atlantic.Mapped Turner Angle in diagnosing the double-diffusion processes shows that the salty Central Water can flux salt down to the upper half of AAIW layer through salt-fingering. Therefore, the northward transition of AAIW can gain salt either through along-neutral-surface advection and diffusion or through salt fingering from the Central Water and heat through either along-neutral-surface advection and diffusion or dianeutral upwelling. Cabbeling and thermobaricity are found significant in the Antarctic frontal zone and contribute to dianeutral downwelling with velocity as high as −1.5×10^-7 m s^-1. A schematic AAIW circulation in the South Atlantic suggests that dianeutral mixing plays an essential role in transforming AAIW into NADW return formation.     

Propagation of Antarctic Bottom Water in the Discovery Gap (Northeast Atlantic) Based on Measurements from 2019

Oceanology - The results of the analysis of the thermohaline water parameters of the bottom layer in the Discovery Gap (Azores-Gibraltar Fracture Zone, Northeast Atlantic) are presented. The data...     

西印度洋产纤维素酶细菌的筛选及酶学特性初步研究

本研究从西印度洋表层沉积物中筛选获得1株高抗性、稳定性好的纤维素酶高产菌株XN149,通过形态学、革兰氏染色、生理生化鉴定以及16S rRNA基因序列分析对菌株进行分类鉴定,并研究了其酶学特性。结果表明,菌株XN149为漳州芽孢杆菌（Bacillus zhangzhouensis）,具有较高的产纤维素酶能力。酶学特性研究表明,该菌株所产纤维素酶的最适反应温度为65 ℃,最佳pH为6.0,该条件下发酵48 h后粗酶液酶活力为（60.19±0.31） U/mL。在30～60 ℃及pH为5.0～8.0时酶活性稳定性较高,Fe3+、Mn2+对该酶活性有一定的促进作用,Ba2+对其酶活性具有抑制作用。综上,漳州芽孢杆菌XN149是一株高产纤维素酶菌株,所产纤维素酶具有良好的耐热性和一定的酸碱耐受性,具有潜在的产业应用开发价值。     

Large but variable particulate flux in the Antarctic Ocean and its significance for the chemistry of Antarctic water

Settling particles were collected at 1,460 m and 3,760 m depth in the Antarctic Ocean with sediment traps of time series type. The total deployment period of 40 days was divided into four terms of 10 days each. Seawater samples were collected both at deployment and retrieval of the traps at each site. During the 42 days the concentration of silicate in the surface water decreased by 32%, whereas those of nitrate and phosphate decreased by only 4–5%. The total particulate flux in the Antarctic Ocean is the largest among those hitherto observed in the world ocean. The time variation of the particulate flux at 1,460 m depth almost coincided with that at 3,760 m. The settling particles were comprised roughly of 80% biogenic silica, 15% organic matter and 5% other substances including sea salt. The clay fraction was only 0.05% at 1,460 m depth. The settling flux of biogenic silica agrees fairly well with the calculated rate of change in the concentration of silicate in the surface 100 m. Thus it is concluded that preferential propagation of diatoms reduces the concentration of silicate prior to other nutrients in the Antarctic Ocean.     

Diet of albacore Thunnus alalunga from the waters of Mauritius (western Indian Ocean) inferred from stomach contents and fatty acid analysis

The diet of albacore Thunnus alalunga from their spawning ground in the waters of Mauritius was investigated. The stomach contents of 249 albacore individuals, caught by industrial longliners and artisanal fishers, was analysed, and the dominant prey taxa were selected for lipid and fatty acid (FA) analysis. The FA profiles of prey were compared with those of liver tissue of spawning-capable and post-spawning female albacore, using multivariate analysis. Whereas stomach content analysis identified cephalopods and crustaceans as the dominant prey items in number, FA-profile analysis identified crustaceans and fishes as the most-frequently consumed prey of post-spawning female albacore. In contrast, the FA profiles of spawning-capable albacore and those of prey showed very low similarity. Analysis of the prey suggests that although cephalopods, crustaceans and fishes could all provide albacore with the required lipids and FAs, cephalopod prey seem to be less desirable owing to their lower energy content (i.e. low in total lipid, triacylglycerol, 16:0, 18:0 and 18:1ω9). Instead, the most beneficial food appeared to be locally available fishes, which are more energy-rich and have a higher docosahexaenoic acid/ eicosapentaenoic acid ratio. These results provide new information on the trophic ecology of albacore, promote our understanding of the importance of prey type for successful reproduction of albacore, and highlight the advantages of FA profiling to study diet.     

Ferromanganese Nodules and Crusts from the Christmas Island Region,Indian Ocean

A sampling expedition has shown that largely hydrogenetic marine ferromanganese deposits occur in the Christmas Island region south of Java (~10°S), as small nodules on seamount slopes and abyssal plains (red clay), and as thick crusts on volcanic ridges and seamounts. Vernadite is dominant, with birnessite, jacobsite and todorokite common. Nodules were recovered in 25% of free-fall grab stations in water 4600-5900 m deep, and are not abundant where present. The nodules average 9.6% Fe, 19.7% Mn, 0.51% Ni, 0.49% Cu, and 0.12% Co. Crusts are common in water 1450-3700 m deep, with average deposition rates of 1-1.5 mm / m.y. The crusts average 13.9% Fe, 16.2% Mn, 0.35% Ni, 0.11% Cu, and 0.44% Co. Cobalt grades are higher (~0.8%) in shallower water ( < 2500 m), so future exploration should concentrate on depths of 500-1500 m near the oxygen minimum zone.     

赤道印度洋海温偶极子的气候影响及数值模拟研究

在分析研究印度洋海温变化的基本特征,尤其是在分析赤道印度洋海温偶极子及其影响的基础上,利用IAP9L大气环流模式模拟研究了赤道印度洋海温偶极子异常对亚洲季风区气候变化的影响.其结果表明,印度洋、亚洲南部和东部地区的流场和降水都对印度洋海温异常的强迫作用比较敏感.正位相印度洋偶极子的作用使得赤道东印度洋-印度次大陆南部-阿拉伯海一带出现距平东风,孟加拉湾-中南半岛出现异常反气旋性环流,从而对减少印度南部和中南半岛南部、印度尼西亚地区的夏季降水,以及增加中国南部和东非的夏季降水有十分重要的作用.与此相反,负位相印度洋偶极子的作用将使赤道东印度洋附近出现西风异常,孟加拉湾-中南半岛存在异常气旋性环流,从而使印度次大陆和中南半岛南部、印度尼西亚地区的降水增加,使中国西部和孟加拉湾的降水减少.数值模拟结果与资料分析相互映证,切实地揭示了印度洋海温偶极子对亚洲季风区的气候变化有重要影响.     

The source and origin of the 1929 grand banks turbidity current inferred from sediment budgets

Side-scan data from the epicentral area of the 1929 Grand Banks earthquake and cores from the resulting turbidite are used to determine a sediment budget for the event. The 1929 turbidite has a volume of about 185 cubic km, which is mostly sand. Features indicating failure on the continental slope are observed only in muddy sediment. A major source of sand in the heads of the fan valleys of the Laurentian Fan is postulated to balance the sediment budget. This sand accumulated proglacially during the Wisconsinan glaciation and probably failed through liquefaction in the 1929 earthquake.     

Nature and distribution of manganese nodules from three sediment domains of the Central Indian Basin,Indian Ocean

Manganese nodules from the Central Indian Basin (5°–10°S) vary in abundance, morphology, mineralogy, and chemistry with water depth and sediment type. Nodules from the southern region, dominated by siliceous sediment, differ markedly from northern and central regions, dominated by terrigenous and terrigenous-siliceous mixed sediments, respectively. Effects of lysocline and sediment diagenesis are envisaged for trace metal enrichment in rough nodules of the southern region. Influence of deep ocean bottom currents have been postulated for the atypical trace metal enrichment of the smooth nodules from other regions. While nodules from other areas of sub-equatorial CIB are grown hydrogenetically, present area nodules show diagenetic influence.     

Periodic Intrusion of Cold Water from the Pacific Ocean into the Bottom Layer of the Bungo Channel in Japan

A cold-water intrusion, called a “bottom intrusion”, occurs in the lower layer of the Bungo Channel in Japan. It is an intrusion from the shelf slope region of the Pacific Ocean margin in the south of the channel. In order to reveal the fundamental characteristics of the bottom intrusion, we conducted long-term observations of water temperature at the surface and bottom layers of the channel and 15-day current observations at the bottom of the shelf-break region. The long-term water temperature data indicated that the bottom intrusion occurs repeatedly between early summer and late autumn, and its reiteration between early and mid-summer causes a local minimum of water temperature in the lower layer in mid-summer. Moreover, the data revealed that most of the bottom intrusions occurred in neap tidal periods. The current meter recorded a bottom intrusion with a speed of approximately 15 cm⋅s⁻¹. The current meter also revealed that the intruded cold water slowly retreated back to the shelf slope region after the intrusion. This revised version was published online in July 2006 with corrections to the Cover Date.     

东南印度洋沿岸海温年代际振荡及经向传播探讨

用SODA资料分析了热带西南印度洋上升区温度距平与整个南印度洋温度距平的时滞相关, 发现热带西南印度洋上升区温度距平与65°S, 105°E附近200 m深度的温度距平存在滞后10 a的相关振荡, 同时探讨了其可能的机制为温跃层内的斜压内波驱动, 即65°S, 105°E附近200 m深度的温度距平沿着温跃层上层在东南印度洋沿岸从高纬度向低纬的传播, 传播时间大约为10 a左右, 这种信号在传播过程中表现得较弱, 而在起点和终点的两端振荡比较强。波动的传播相比振荡本身要显得弱。