North Pacific sea ice cover, a predictor for the Western North Pacific typhoon frequency?

The relationship between the sea ice cover in the North Pacific and the typhoon frequency has been studied in this paper. It follows that the index for the sea ice cover in the North Pacific (ISA) both in December-January-February (DJF) and in March-April-May (MAM) is negatively correlated with annual typhoon number over the western North Pacific (TNWNP) during 1965―2004, with correlation coeffi-cients of -0.42 and -0.49 respectively (above 99% significant level). Large sea ice cover in the North Pacific tends to decrease TNWNP. Positive ISA (MAM) is associated with the tropical circulation and SST anomalies in the North Pacific, which may lead to unfavorable dynamic and thermal conditions for typhoon genesis over WNP from June to October (JJASO). The variability of the atmospheric circula-tion over the North Pacific, associated with the ISA anomaly in MAM is connected to the tropical at-mospheric circulation variability in MAM via the teleconnection wave train. Besides, as the tropical circulation has strong seasonal persistency from the MAM to JJASO, thus, the ISA in MAM-related variability of the tropical atmospheric circulation as well as the SST can affect the typhoon activity over the western North Pacific.     

Inversion for tides in the Eastern North Pacific Ocean

A regional model of tides in the Eastern North Pacific Ocean is developed through the use of inversion with two-dimensional finite element codes. Since global tide models are least accurate in coastal environments, modeling tides on a regional scale allows tidal propagation and interaction along the coast to be more accurately represented. In this respect, a regional model can act as a liaison between open ocean dynamics and physical processes more pertinent to coastal systems. The region of interest in this study extends from the Aleutian Islands to Southern California and includes deep ocean, continental shelf, and shallow water features. Boundary conditions are determined from nonlinear inversion of harmonic data from both shallow water and deep ocean tide gauges. Spatial patterns of amplitudes and phases from the model are examined for major constituents. Results are also compared to global tide models at selected stations.     

The density of North Atlantic and North Pacific deep waters

The densities of seventeen samples of seawater from GEOSECS stations 27 (North Atlantic) and 217 (North Pacific) have been measured with a vibrating flow densimeter at 25°C. The densities of the deep samples were found to be 5 ± 1.5and16 ± 3.6ppm greater, for the North Atlantic and North Pacific, respectively, than predicted by the equation of state of Millero, Gonzalez and Ward (1976) derived for seawaters of constant relative composition. The results are in good agreement with the density anomalies predicted by Brewer and Bradshaw (1975) on the basis of the observed increase of dissolved silica, alkalinity and total carbon dioxide in oceanic deep waters. The application of these corrections results in an agreement with the Millero, Gonzalez and Ward (1976) equation of state to ±4 ppm.     

Bifurcation of Pacific North Equatorial Current at the surface

The grid altimetry data between 1993 and 2006 near the Philippines were analyzed by the method of Empirical Orthogonal Function (EOF) to study the variation of bifurcation of the North Equatorial Current at the surface of the Pacific. The relatively short-term signals with periods of about 6 months, 4 months, 3 months and 2 months are found besides seasonal and interannual variations mentioned in previous studies. Local wind stress curl plays an important role in controlling variation of bifurcation latitude except in the interannual timescale. The bifurcation latitude is about 13.3°N in annual mean state and it lies at the northernmost position (14.0°N) in January, at the southernmost position (12.5°N) in July. The amplitude of variation of bifurcation latitude in a year is 1.5°, which can mainly be explained as the contributions of the signals with periods of about 1 year (1.2°) and 0.5 year (0.3°). Supported by National Basic Research Program of China (Grant No. 2007CB411802), National Natural Science Foundation of China (Grant Nos. 40806012, 40876013), Open Fund of the Key Laboratory of Ocean Circulation and Waves, Chinese Academy of Sciences (Grant No. KLOCAW0803) and Scientific Research Foundation for Talent, Guangdong Ocean University (Grant No. E06118)     

In-situ dissolution experiment of radiolaria in the central North Pacific ocean

Monospecific phaeodarian radiolarian assemblages of Castanidium longispinum were suspended in plastic cages built with 225 μm nylon mesh at different water depths from 378 to 5582 m in the central North Pacific. Weight losses of these samples after a suspension period of 61 days were used to determine dissolution rates. The highest weight losses were observed at 378 m where samples lost ～90% of their initial weight. Through the main thermocline weight losses decreased from 90 to 60% and reached a constant value of 40% below it. These weight losses are roughly an order of magnitude higher than those reported by earlier workers. The higher weight losses can be attributed in part to the more soluble nature of the phaeodarian radiolarian skeletons and in part to the improved experimental technique. Kinetic considerations show that temperature is the major factor that controls silica dissolution rates in the ocean. Using an Arrehnius plot for the apparent rate constants, it can be shown that in surface water dissolution rats should be two orders of magnitude higher than in deep water below the main thermocline.     

Geothermal regime and geodynamics of the North Pacific Ocean

The distribution of heat flow in the North Pacific Ocean has been examined, and a map of geothermal and geomagnetic fields for the Bering Sea as it is known today has been made. Reliable data are lacking regarding the time of origin for features of oceanic and continental genesis in the Bering Sea, which is an obstacle to the study of geodynamic processes in the North Pacific. Heat flow data were used to yield numerical estimates for the age of seafloor features in the Bering Sea: the Kamchatka Basin (21 Ma), Shirshov Ridge (95 Ma for the northern part and 33 Ma for the southern), the Aleutian Basin (70 Ma), Vitus Rise (44 Ma), Bowers Ridge (30 Ma), and Bowers Basin (40 Ma). These age estimates are corroborated by combined geological, geophysical, and plate kinematic data. A thermochemical model of global mantle convection has been developed in order to perform a numerical simulation of the thermal process involved in the generation of extended regional features in the North Pacific (the Emperor Fracture Zone, Chinook Trough, etc.). The modeling suggests a plume-tectonic origin for these features, yielding the optimal model for the tectonic evolution of the North Pacific. An integrated geological and geothermal analysis leads to the conclusion that the northern and southern parts of the Shirshov Ridge are different, not only in geologic age, but also in tectonic structure. The northern part is of imbricated-thrust terrane origin, while the southern part is of ensimatic island-arc origin, similar to that of Bowers Ridge. The seafloor of the Aleutian Basin is an outlier of the Upper Cretaceous Kula plate where, in the Vitus Rise area, backarc spreading processes originated during Eocene time. The terminating phase of activity in the Bering Sea began about 21 Ma by spreading in the older seafloor of the Kamchatka Basin. We developed plate-tectonic reconstructions of evolution for the North Pacific for the times 21, 33, 40, and 70 Ma in the hotspot system based on age estimates for the seafloor features derived from heat flow data and modeling of the thermal generation of regional faults, as well as on an analysis of geomagnetic, tectonic, and geological data.     

Plastic ingestion by planktivorous fishes in the North Pacific Central Gyre

A significant amount of marine debris has accumulated in the North Pacific Central Gyre (NPCG). The effects on larger marine organisms have been documented through cases of entanglement and ingestion; however, little is known about the effects on lower trophic level marine organisms. This study is the first to document ingestion and quantify the amount of plastic found in the gut of common planktivorous fish in the NPCG. From February 11 to 14, 2008, 11 neuston samples were collected by manta trawl in the NPCG. Plastic from each trawl and fish stomach was counted and weighed and categorized by type, size class and color. Approximately 35% of the fish studied had ingested plastic, averaging 2.1 pieces per fish. Additional studies are needed to determine the residence time of ingested plastics and their effects on fish health and the food chain implications.     

Marine debris collects within the North Pacific Subtropical Convergence Zone

Floating marine debris, particularly derelict fishing gear, is a hazard to fish, marine mammals, turtles, sea birds, coral reefs, and even human activities. To ameliorate the economic and environmental impact of marine debris, we need to efficiently locate and retrieve dangerous debris at sea. Guided by satellite-derived information, we made four flights north of Hawaii in March and April 2005. During these aerial surveys, we observed over 1800 individual pieces of debris, including 122 derelict fishing nets. The largest debris concentrations were found just north of the North Pacific Transition Zone Chlorophyll Front (TZCF) within the North Pacific Subtropical Convergence Zone (STCZ). Debris densities were significantly correlated with sea-surface temperature (SST), chlorophyll-a concentration (Chla), and the gradient of Chla. A Debris Estimated Likelihood Index (DELI) was developed to predict where high concentrations of debris would be most likely in the North Pacific during spring and early summer.     

The Sumatra tsunami of 26 December 2004 as observed in the North Pacific and North Atlantic oceans

The M _w=9.3 megathrust earthquake of December 26, 2004 off the coast of Sumatra in the Indian Ocean generated a catastrophic tsunami that caused widespread damage in coastal areas and left more than 226,000 people dead or missing. The Sumatra tsunami was accurately recorded by a large number of tide gauges throughout the world's oceans. This paper examines the amplitudes, frequencies and wave train structure of tsunami waves recorded by tide gauges located more than 20,000 km from the source area along the Pacific and Atlantic coasts of North America.     

北太平洋海表面高度的年际变化及其机制

利用15年（1993～2007年）月平均的海表面高度（SSH）异常资料,分析了北太平洋海表面高度的年际变化的时空结构,并研究了热通量和风应力两个因子对其的强迫作用.结果表明,北太平洋年际时间尺度SSH变化的大值区在黑潮延伸区和西太平洋暖池区.EOF分解第一模态的空间结构沿纬向呈带状分布,第二模态为沿经向呈带状分布.热通量强迫作用在中纬度的东北太平洋可以解释SSH年际变化40%以上.风应力对SSH的作用包括正压和斜压两个方面.正压Sverdrup平衡模型模拟的SSH年际变化较弱,仅能解释高纬度副极地环流西部的20%~40%.由大尺度风应力强迫的第一阶斜压Rossby波模型可以解释热带地区的20%~60%,中纬度中部的20%~40%,以及阿拉斯加环流东部和副极地环流西部的20%~60%.风应力强迫的一阶斜压Rossby波模型对SSH的强迫机理又可分为局地风应力强迫和西传Rossby波作用.其中,风应力的局地强迫作用（Ekman抽吸）在东北太平洋、白令海以及热带中部有显著的预报技巧,可以解释SSH年际变异的40%以上.Rossby波的传播作用在中纬度海域的副热带环流中西部和夏威夷岛以东起着重要作用,可解释20%~60%.     

Water exchange between the subpolar and subtropical North Pacific in an OGCM

The water exchange between the subpolar and subtropical gyres of the North Pacific is demonstrated by the simulation of chlorofluorocarbon (CFC) using an ocean general circulation model. The simulated CFC concentration in the North Pacific is in good agreement with observations. The water exchange is clearly illustrated by the tongues of CFC concentration. The subpolar waters with high CFC are transported southward into the eastern subtropical gyre, whereas the subtropical waters with low CFC are transported northward into the western subpolar gyre. The simulated exchange transport along 42°N in the layer of σθ< 26.8 indicates that the northward mass transport is about 15 Sv (1 Sv = 106 m3·s-1) west of 165°E, and about 5 Sv between 175°W and 150°W. The southward mass transport is about 5 Sv between 165°E and 175°W, and about 2 Sv east of 150°W.     

The water column distributions of thorium isotopes in the western North Pacific

Four vertical profiles of²³⁰Th and²²⁸Th were determined using large volume water samples in the western North Pacific. An almost linear increase of²³⁰Th with depth was observed for all of the profiles for which the unidirectional first order scavenging model was difficult to explain. We developed a model which included a dissolved-particulate transformation as well as parameters of the scavenging model. Application of the model to the vertical distributions of total and the GEOSECS particulate Th isotopes (²³⁰Th and²³⁴Th) yielded the residence time of dissolved Th with respect to adsorption to particles and the turnover time of particulate Th to be 235 days and 57 days, respectively. The Th isotopes appeared to be carried down the water column by fine particles with a mean settling velocity of 1 m/day which continually release Th into sea water as well as pick up Th from the water along their journey to the bottom.For²²⁸Th, a large excess over²³²Th was observed throughout the water column with pronounced high concentrations in surface and bottom waters, suggesting that the²²⁸Th was derived from²²⁸Ra diffused out of sediments. The vertical distributions of²²⁸Th seemed to be significantly influenced by lateral mixing along isopycnals.     

Summary of taxa and distribution of Sirenia in the North Pacific Ocean

Abstract North Pacific fossil sirenians comprise representatives of three subfamilies of the Dugongidae: Halitheriinae ( Metaxytherium arctodites , Middle Miocene, North America), Hy-drodamalinae ( Dusisiren spp., Early-Late Miocene, and Hydrodamalis spp., Late Miocene-Pleistocene, North America and Japan), and Dugonginae ( Dioplotherium allisoni , Early-Middle Miocene, North America). Indeterminate dugongid remains are also known from the Late Oligocene of Japan, and the discovery of additional taxa in the western Pacific, especially in Paleogene rocks, can be anticipated. The known North Pacific Neogene taxa apparently dispersed into the Pacific from the Caribbean. Metaxytherium gave rise in the Pacific to Dusisiren ; a series of chronospecies of the latter genus eventually culminated in Hydrodamalis , which was exterminated by humans circa AD 1768. Dioplotherium left no known descendants in the Pacific. The Recent Dugong probably entered the Pacific from the Indian Ocean. The presence in the North Pacific Miocene of at least three sympatric dugongid lineages, together with desmostylians, is evidence for a diversity of marine plants that was reduced by subsequent climatic cooling.     

北太平洋对人为二氧化碳吸收的数值模拟

采用一个开边界海盆尺度环流模式研究人为CO2在北太平洋的吸收和分布,并与闭边界模式的模拟结果进行了比较.模拟结果表明,西北太平洋和赤道东太平洋是两个重要的人为CO2汇.使用较大的等密度面扩散系数使得西北太平洋人为CO2通量增大,而赤道海区通量减小（RUN2）.与闭边界模式相比,开边界模式中该两个区域的人为CO2通量都增加了.1800～1997年间,北太平洋共吸收人为CO2 23.75GtC(1Gt=1×1015 g, RUN1).副极地海区是人为CO2的一个重要输出区,能输出人为CO2吸收量的38％～54％,而20°N～30°N海区是人为CO2的一个重要贮存区,占整个北太平洋的24％.开边界对于10°N以南太平洋吸收和贮存人为CO2有很大影响.与基于观测资料的估计相比,虽然模式低估了西北太平洋的人为CO2的穿透,高估了东北太平洋的人为CO2的穿透,但总的说来,模式比较好地估计了人为CO2在北太平洋的贮存.     

The eastward subtropical countercurrent on isopycnal surface in the western North Pacific

The classic Sverdrup theory suggests that the water movement in the central subtropical gyre of North Pa-cific be slowly westward or southwestward.In the late sixties of the20th century,the existence of a peculiar eastward narrow flow between20°N and25°N in spring was theoretically predicted.It was named the Subtropical Countercurrent(STCC),although direct observational evidences were not yet sufficient to con-firm whether or not such eastward flow between20°N and25°N was a persistent…     

Evolution of seasonal temperature disturbances and solar forcing in the US North Pacific

We analyze the long-term evolution of seasonal temperature disturbances in a 2.5×2.5° area of the US North Pacific. Late Fall and early Winter display significant correlation of temperature disturbances and are investigated in detail. The long-term evolution of the Fall temperature disturbances from 1945 to 2008 closely follows that of solar activity. The robustness of these results is successfully controlled in a 2.5×2.5° area immediately north of the studied region. The modulation of temperature disturbances is very large (～30%) compared to the corresponding changes in solar irradiance, and has significant variability, even at small geographical scale. The physical mechanism of solar forcing of temperature disturbances remains to be understood, but a relation with cloudiness and influence of the Madden–Julian oscillation in the North Pacific is suggested.     

Water mass characteristics in the western North Pacific based on a streamfunction projection

A streamfunction projection method called gravest empirical mode(GEM) is applied to the hydrographic section at 137°E to filter out eddy noises in the western North Pacific and derive quantitative ensemble-average water mass properties in the North Equatorial Current region. The GEM fields capture more than 80% of total property variances in the thermocline layer. The core layer structures of key water masses, including the North Pacific Tropical Water(NPTW) and the North Pacific Intermediate Water(NPIW), are examined with a definition of water mass boundary based on property gradient. It shows that a tongue of maximal root-mean-square(RMS) residual exists in the upper half of NPIW for all water properties. These subsurface RMS tongues appear to be close to sharp property gradients. It is the first time a GEM diagnosis is applied to nutrient data, which reveals a drastic difference of N/P reaction rate ratio above and below the maximal-nutrient core at 1250 m. Additionally, a GEM velocity reconstruction successfully produces the North Equatorial Undercurrent(NEUC), demonstrating the stable thermal-wind nature of this newly-discovered current.