Long internal waves in the Tropical Atlantic ocean generated by periodic air pressure fluctuations

Taking into consideration stratification, the mean current velocity, and the tangential wind stress expressed in terms of air pressure fluctuations, we have derived iteration formulae and have performed computations of the amplitudinal characteristics of oceanic internal waves generated by air pressure waves of semi-diurnal and 4-day long periodicity propagating over the Tropical Atlantic Ocean. It has been demonstrated that such periodicity and wavelengths may contribute to the generation of long-amplitude internal waves, whose intensity is largely dependent on the direction of atmospheric wave propagation.Translated by Vladimir A. Puchkin.     

Long-range underwater photography in the deep ocean

Although the optical properties of seawater at extreme depths are more suitable for underwater photography than those at the surface or on continental shelves, they still impose severe limitations on long-range wide area bottom photography. Additionally, deep ocean operations impose technical limitations on control, power and bandwidth. This chapter reviews the approaches contemplated or made towards improving the camerato-target range in underwater photography in the deep ocean. Further significant improvements await advances in control, power/light sources and bandwidth reduction. With the developments now contemplated, TV and video systems will eventually present a strong challenge to emulsion film techniques.     

Sedimentation of lithogenic particles in the deep ocean

Investigation of lithogenic particles collected by sediment traps in open-ocean stations revealed that the sediment flux increased linearly with depth in the water column. This rate of increase decreased with distance of the station from the continent; it was largest at the Panama Basin station and almost negligible at the E. Hawaii Abyssal Plain station. At the Panama Basin station, smectite flux increased with depth. We suggest that smectite resuspended from bottom sediments of the continental slope west of the sediment-trap station is advected by easterly deep currents, and the suspended particles are then possibly entrapped by large settling particles. On the other hand, the flux of hemipelagic clay particles, kaolinite and chlorite, was nearly constant at all depths; this can be explained by incorporation of these particles in fecal pellets which then settle from the surface water. At the Demerara Abyssal Basin Station, flux of illite and chlorite particles increased with depth and the flux of smectite was constant. A sudden increase of the flux of illite and chlorite was observed near the bottom traps at the Söhm Abyssal Plain station. The flux of quartz and feldspar was 10 to 15% of the clay flux.     

Effects of the deep ocean circulation on the reservoir characteristics of the ocean

To examine the effects of the deep ocean circulation on the characteristics of the ocean as a reservoir, age distributions of the material whose source and sink are at the ocean surface are calculated using an idealized vertical two-dimensional model of the ocean. The results show that the large-scale vertical circulation of the deep water accelerates the renewal of deep water and reduces the average age of the material. It is also shown that the multi-layered structures of the deep circulation are more realistic than the one-layered structure and promote the renewal of the deep water.     

Infrasonic seismic and acoustic measurements in the deep ocean

The authors compare the signal-to-noise ratios obtained on bottomed seismometers, bottomed hydrophones, and buried seismometers from near-surface explosions in the Ngendei Expedition. The data were recorded in 5.5-km-deep water in the south central Pacific Ocean with a triaxial borehole seismograph and four triaxial ocean-bottom seismographs having externally mounted hydrophones. At ranges less than 35 km, the data indicate that the ocean bottom seismometer is a superior signal detector than the ocean-bottom hydrophone, and that the subbottom seismometer is superior in performance to the ocean-bottom seismometer. Above 4 Hz, the seismometer appears to have a 10-dB signal-to-noise advantage over the hydrophone for surface explosions at ranges less than 30 km     

Integrated navigation systems for precise positioning in the deep ocean

For navigation in deep ocean the most important navaids are self contained dead reckoning systems (DRS) such as classical DRS with log and compass or Doppler‐DRS or inertial navigation system (INS) and the external radio navaids LORAN, Omega and Navy Navigation Satellite System (NNSS). These navaids cannot satisfy the requirements for precise surveying if they are used in the conventional manner. Accuracy can be increased by integration of the DRS with the external navaids by a computer which estimates best values of position, velocity, etc. from all available data. The DRS is used as reference system and the external navaids are used for control measurements. The measurements are compared with the same quantities computed from the positions, which are indicated of the DRS. The differences between the measured and the computed values are described by error models of the integrated navaids and processed by a filter to estimate best values of the errors of the DRS and to make corresponding corrections. The principles of least square filtering are described in detail for integrated Inertial/LORAN‐C and Inertial/Omega navigation.     

海洋中深度与压强的转换方法

介绍了海洋学计算中3种深度与压强的转化方法:(1)EOS-80(Equation of State of Seawater 1980,EOS-80)标准采用的方法;(2)最新发布的TEOS-10(Thermodynamics Equation of seawater 2010,TEOS-10)标准采用的方法;(3)通过海水吉布斯函数计算压强与深度的关系的方法。对以上3种计算方法进行了比较,结果表明:在一般的海洋学研究中,3种方法精度相差不大,均可使用。在要求计算效率的情况下,可以选用EOS-80标准采用的方法,在更高精度的海洋学研究中,应该使用TEOS-10标准采用的方法或者吉布斯函数方法。     

EPSONDE: an instrument to measure turbulence in the deep ocean

EPSONDE is a tethered free-fall profiling system used to obtain temperature microstructure and velocity turbulence data to a depth of at least 1500 m. EPSONDE, which carries a variety of slow and fast sensors, is deployed on a loose kevlar multiconductor cable by a specialized wire-handling system. Data are transmitted from this underwater unit (1792 samples per second) to a shipboard system which includes a dedicated microcomputer for data logging and online data processing. The performance of this system is demonstrated by discussing a study of turbulent mixing processes in a lens of Mediterranean water (a MEDDY) found at a depth of 1000 m in the Canary basin. These studies indicate that turbulent kinetic energy dissipation may be an important mechanism in determining the decay and lifetime of a MEDDY     

Feasibility of dumping fossil-fuel CO2 into the deep ocean

An idea has been proposed to recover and dispose of the fossil-fuel CO₂ generated by stationary power plants into the deep sea, thereby reducing the CO₂ emission to the atmosphere. The assessment of its environmental effects and risks is essential for developing new technology for the recovery/disposal system, which has recently received growing attention in Japan.The simple calculation made here did not yield any decisively significant environmental risks so far. However, a further detailed study is needed for the consequences of lowering local pH and the abrupt dissolution of CaCO₃ in the deep-sea sediments. It is also shown that, on longer term, the atmospheric concentration of CO₂ may be influenced by the degree at which the reaction between the disposed fossil-fuel CO₂ and the sedimentary CaCO₃ takes place under such conditions. At any rate, the problem should be brought to serious scientific attention much like the case of ocean dumping of radioactive wastes.     

Inertial oscillations as deep ocean response to hurricanes

We discuss the deep ocean response to passing hurricanes (aka typhoons), which are considered as generators of near-inertial, internal waves. The analysis of data collected in the northwestern parts of the Pacific and Atlantic oceans in the hurricane season permit us to assess the deep ocean response to such a strong atmospheric forcing. A large number of moorings (more than 100) in the northwestern Pacific have allowed us to characterize the spatial features of the oceanic response to typhoons and the variable downward velocity of near-inertial wave propagation. The velocity of their downward propagation varies in the range 1–10 m/hour. It is higher in the regions of low stratification and high anticyclonic vorticity. The inertial oscillations generated by a hurricane last for 10–12 days. The mean anticyclonic vorticity in the region increases the effective frequency of inertial oscillations by 0.001–0.004 cyc/hour.     

An improved parachute drogue system for monitoring currents in the deep ocean

A parachute drogue is described that can quickly be assembled and easily launched at sea. An anchored buoy, which provides a reference from which drogue trajectories can be determined is also described and methods for launching are outlined. This buoy, which can be moored in several kilometers depth, will extend to the deep ocean the use of drogue monitoring techniques capable of defining wind driven currents and their short-term periodicities.     

An Ocean Bottom Hydrophone instrument for seismic refraction experiments in the deep ocean

Tests of a new Ocean Bottom Hydrophone (obh) instrument have recently been completed at Woods Hole Oceanographic Institution. This instrument is designed to float 3 m above the seafloor at depths of up to 6100 m for periods of up to 10 days and continuously records the output of a single hydrophone on a four-channel 0.064 cm/s (1/40 in./s) analog magnetic tape recorder. This instrument has an acoustic transponder and release system and is designed primarily for multiple deployments as a fixed ocean bottom receiver for seismic refraction work.Contribution No. 4174 of the Woods Hole Oceanographic Institution.     

Tsunami detectability using open-ocean bottom pressure fluctuations

Rationale for the measurement of open-ocean tsunami signatures are presented, and available pertinent data are reviewed. Models for tsunami signature and background noise are proposed in order to synthesize an optimum tsunami receiver. Using these models, the minimum tsunami amplitude (in cm) to yield the probability of correct tsunami detectionP_{D} = 0.999and probability of false alarmP_{F} = 10^{-3}is found to be0.718/sqrt{f_{0}}, wheref_{0}is the tsunami dominant frequency (in cycles/h). A realizable receiver is proposed and its performance is evaluated using actual tsunami signatures. It is demonstrated that the detection of a tsunami with an average amplitude as small as 0.7 cm is possible for theP_{D}andP_{F}as above. Simulation results using synthesized background noise are shown. Tidal effects on the receiver performance also are considered and are found negligible for a certain range of the receiver parameters, resulting in a considerable reduction of the signal processing required.     

Determination of gas bubble fractionation rates in the deep ocean by laser Raman spectroscopy

A new deep-sea laser Raman spectrometer (DORISS—Deep Ocean Raman In Situ Spectrometer) is used to observe the preferential dissolution of CO₂ into seawater from a 50%–50% CO₂–N₂ gas mixture in a set of experiments that test a proposed method of CO₂ sequestration in the deep ocean. In a first set of experiments performed at 300 m depth, an open-bottomed 1000 cm³ cube was used to contain the gas mixture; and in a second set of experiments a 2.5 cm³ funnel was used to hold a bubble of the gas mixture in front of the sampling optic. By observing the changing ratios of the CO₂ and N₂ Raman bands we were able to determine the gas flux and the mass transfer coefficient at 300 m depth and compare them to theoretical calculations for air–sea gas exchange. Although each experiment had a different configuration, comparable results were obtained. As expected, the ratio of CO₂ to N₂ drops off at an exponential rate as CO₂ is preferentially dissolved in seawater. In fitting the data with theoretical gas flux calculations, the boundary layer thickness was determined to be  42 μm for the gas cube, and  165 μm for the gas funnel reflecting different boundary layer turbulence. The mass transfer coefficients for CO₂ are k_L = 2.82 × 10^− 5 m/s for the gas cube experiment, and k_L = 7.98 × 10^− 6 m/s for the gas funnel experiment.     

Generation of long internal waves in the ocean by a moving pressure zone

The generation of plane internal waves in a continuously stratified ocean by a steadily moving anomaly of the atmospheric pressure is studied in a linear statement using a quasi-static approximation. Quantitative estimates for the parameters of internal waves in the wake are obtained for the average distribution of the Väisälä-Brunt frequency in the Caribbean Sea.Translated by Mikhail M. Trufanov.     

Relationship between the anomalies of temperature and air pressure over the ocean

This paper considers the relationship between multi-year air temperature and pressure fluctuations over the ocean, based on an approximate solution of the problem on the determination of large-scale seawater temperature anomalies from the conditions predominating at the sea surface. The dependence derived is numerically analysed using observations made in the North Atlantic. It is shown that the variability of annual mean air temperature anomalies is largely controlled by the air pressure field which has taken place during the preceding long-term period. The dependence derived may be applied to generate long-term forecasts of the ocean's hydrometeorological regime.Translated by Vladimir A. Puchkin.     

Measurements of ocean bottom pressure with a quartz sensor

Year long measurements of bottom pressure were made at 2,036 m depth in Sagami Trough, at 2,538 m depth in Suruga Trough, and at 32 m depth in the south of Minami-Daitojima Island. Amplitudes and phase lags of the major constituents of tides were estimated by the response method, and they were compared with the observational results at several tide stations operated by the Japan Meteorological Agency. A comparison with Schwiderski's global models for the eight tidal constituents showed that the amplitudes were in good accordance to one another within 3 cm, and that the differences of phase lags were less than 15°. The largest portion of the variations of the bottom pressure was caused by the tides: the variance of the major eight constituents was more than 98.5% as large as the total variance. The measurements show that tidal waves can be recorded offshore with a sufficient accuracy by the quartz sensors. Drifts of indication of the pressure gauges were significant and they prevented detection of a long-term variation which might be caused by fluctuations of the ocean currents or by the eddies.     

弱气压场中南海东北部海浪预报失败典型个案

目前在广东气象界里对海浪预报服务情况分析是比较少的,针对2005年12月底到2006年1月初南海东北部石油平台用户对海浪预报产品服务的意见反馈,本文通过分析该时段的天气背景,中尺度数值预报产品,实况风浪情况,综合我们提供给用户的海浪预报产品进行对比,目的是找出该次预报不成功的事实和原因,给用户有所交代;同时希望通过这类总结分析,对海上风浪预报服务提出警示,避免类似错误再次出现,提高专业预报服务质量。     

Surface manifestation of internal tides in the deep ocean: observations from altimetry and island gauges

The sea-surface height signatures of internal tides in the deep ocean, amounting to a few centimeters or less, are studied using two complementary measurement types: satellite altimetry and island tide gauges. Altimetry can detect internal tides that maintain coherence with the astronomical forcing; island gauges can monitor temporal variability which, in some circumstances, is due to internal tides varying in response to changes in the oceanic medium. This latter mechanism is at work at Hilo and other stations on the northern coasts of the Hawaiian Islands. By detecting spatially coherent low-frequency internal-tide modulations, the tide gauges, along with inverted echo sounders at sea, suggest that the mean internal tide is also spatially coherent; satellite altimetry confirms this. At Hawaii and in many other places, Topex/Poseidon altimetry detects mean surface waves, spatially coherent and propagating great distances (> 1000 km) before decaying below background noise. When temporal variability is small, the altimetry (plus information on ocean density) sets useful constraints on energy fluxes into internal tides. At the Hawaiian Ridge, 15 GW of tidal power is being converted from barotropic to first-mode baroclinic motion. Examples elsewhere warn that a simplistic interpretation of the altimetry, without regard to variability, noise, or in situ information, may be highly misleading. With such uncertainties, extension of the Hawaiian results into a usefully realistic estimate of the global internal-tide energy balance appears premature at this time.     

Shortening of submerged ocean cables due to hydrostatic pressure

It is well known that a submerged cable, under hydrostatic pressure, will shrink in diameter due to radial compressive stresses. Less widely appreciated is that the cable will also shorten due to axial compressive stresses acting along the length of the cable. This paper offers an explanation and presents numerical examples to illustrate this shortening effect. It is demonstrated that a submerged cable can support axial compressive stresses without buckling because the fluid pressure on the lateral surface provides a stabilizing force.