Apparent calcite supersaturation at the ocean surface: Why the present solubility product of pure calcite in seawater does not predict the correct solubility of the salt in nature

It is generally accepted that seawaters near the ocean surface are supersaturated with calcite and that increasing atmospheric CO₂ will not overcome this condition until late in the 21st century. These expectations are based on comparisons of the ion activity products (IAPs) of various seawaters to the solubility product (K) of seawater saturated with pure calcite at 1 atm and a given temperature. It has been shown in recent papers, however, that calcites in contact with natural seawater in the surface oceans are not pure, but are magnesian calcite compositions. As a result, the presently accepted values of the solubility product of calcite in seawater cannot be used to obtain a correct, or even a reasonable estimate of the saturation state of sea water relative to either pure or magnesian calcite. Data are presented demonstrating that use of the currently accepted solubility product of calcite in seawater to determine seawater's relative calcite saturation leads to gross overestimates of its extent.     

Structural and geochemical alterations in the Mg calcite bryozoan Myriapora truncata under elevated seawater pCO2 simulating ocean acidification

The possible effects of ocean acidification on the calcareous skeleton of the Mediterranean bryozoan Myriapora truncata (Pallas, 1766) were studied by transplanting live and dead colonies into an area of natural volcanic CO₂ vents at Ischia (Gulf of Naples, Tyrrhenian Sea), Italy. Morphology and geochemistry were compared between colonies from normal (mean pH = 8.07, min. pH 7.95), below‐normal (mean pH 7.66, min. pH 7.32) and acidic (mean pH 7.43, min. pH 6.83) conditions after colonies had been exposed in situ for 45 and 128 days. Both distal (juvenile) and proximal (adult) parts of the branches were investigated. Skeletons of live colonies in acidic pH site after 45 days of exposure were less corroded than those of dead colonies, suggesting that the organic tissues enveloping the skeleton play a protective role. Colonies remained alive at the below‐normal and acidic pH sites during the 45‐day experiment but corrosion was very striking after 128 days, with colonies from the acidic site showing significant loss of skeleton. Compared to the control, these colonies also had lower levels of Mg (mean 8 versus 9.5 wt% Mg) within their skeletons. Electron microprobe mapping showed Mg to be higher in the outer layers of the skeletal walls in colonies from the normal pH site. Corrosion of outer layers of the walls probably explains the lower Mg level found in colonies exposed to acidic conditions. As solubility of calcite increases with Mg content, the enrichment of Mg in outer layers of the skeleton should enhance the vulnerability of Myriapora truncata to dissolution. These findings raise concerns over the survival of bryozoans with Mg calcite skeletons in the face of predicted decreases in oceanic pH levels.     

Geodetic measurements in the ocean

This paper covers the topic of marine geodesy, its goals, and applications. Specifically discussed are position determination and establishment of geodetic control on the ocean bottom, ocean surface, and subsurface, and the determination of the geoid, a vertical reference surface. The various techniques used in position determination (including satellite, airborne, radio, inertial and acoustic techniques) are assessed in terms of accuracy, coverage, and contribution to the solution of specific problems associated with position and control. The results of several marine geodetic control experiments are presented. Classical techniques for the determination of the geoid are discussed and assessed, as are new techniques such as satellite altimetry. The outlook for marine geodetic measurements in the ocean is outlined in terms of what is being planned or considered for the next decade, and several recommendations are made.     

Regeneration of silicate in the ocean

Regeneration of silicate in the Japan Sea, an example of semi-closed sea, was studied. In the Japan Sea Proper Water the apparent regenerative ratio of the nutrients was determined to be:O C N P Si=–289 (116)14.3181.It was assumed that the dissolved silicate present in sea water is grouped into three fractions; 1)preformed silicate of conservative nature, 2)oxidative silicate which dissolves in oxidation process of organisms with consumption of oxygen, and 3)non-oxidative silicate which dissolves without oxygen consumption. The dissolution rate ofnon-oxidative silicate in the Japan Sea Proper Water was estimated to be 0.07g-at. Si/l/yr from the data ofAOU values and assumed rates of oxygen consumption. This dissolution rate ofnon-oxidative silicate agreed with that obtained in the deep Pacific by the vertical advection diffusion model byKido andNishimura (1972).     

The saturation of calcite and aragonite in the Arctic Ocean

We report on the chemical saturation of CaCO₃ in the waters of the Arctic Ocean calculated from total alkalinity (A_T) and total dissolved inorganic carbon (C_T). Data based on four different expeditions are presented: International Arctic Ocean Expedition (IAOE-91), Arctic Ocean Section 94 (AOS94), Polarstern Arctic '96 expedition (ACSYS 96), and Joint Ocean Ice Study 97 (JOIS 97). The results show a lysocline at around 3500 m for aragonite and that most of the Arctic Ocean sea floor lies above the lysocline for calcite. The only anomaly is the low degree of saturation at the shelf break depth in the Canadian Basin seen in the sections of the AOS94 and JOIS 97 cruises, correlated with nutrient maxima and very low O₂ concentration, suggesting decomposition of organic matter. The insignificant variability in degree of saturation between the deep waters of the different basins in the Arctic Ocean indicates a very low sedimentation/remineralisation of organic soft matter.     

Turbulent dispersion in the ocean

The mathematical framework for turbulent transport in the ocean is reasonably well established. It may be applied to large-scale fields of scalars in the ocean and to the instantaneous or continuous discharge from a point. The theory and its physical basis can also provide an interpretation of passive scalar spectra. Spatial variations in the rate of turbulent transfer can be related to the movement of the center of mass of a scalar and to a formulation in terms of entrainment. The relative dispersion of a scalar with respect to its center of mass and the streakiness of the concentration field within the relative dispersion domain need to be considered. In many of these problems it is valuable to think in terms of simple models for individual streaks, as well as overall statistical properties.     

Lagrangian fronts in the ocean

We introduce the concept of Lagrangian fronts (LFs) in the ocean and describe their importance for analyzing water mixing and transport and the specific features and differences from hydrological fronts. A method of calculating LFs in a given velocity field is proposed. Based on altimeter velocity fields from AVISO data in the northwestern Pacific, we calculate the Lagrangian synoptic maps and identify LFs of different spatial and temporal scales. Using statistical analysis of saury catches in different years according to the Goskomrybolovstvo (State Fisheries Committee of the Russian Federation), we show that LFs can serve as good indicators of places that are favorable for fishing.     

CABARET in the ocean gyres

A new high-resolution Eulerian numerical method is proposed for modelling quasigeostrophic ocean dynamics in eddying regimes. The method is based on a novel, second-order non-dissipative and low-dispersive conservative advection scheme called CABARET. The properties of the new method are compared with those of several high-resolution Eulerian methods for linear advection and gas dynamics. Then, the CABARET method is applied to the classical model of the double-gyre ocean circulation and its performance is contrasted against that of the common vorticity-preserving Arakawa method. In turbulent regimes, the new method permits credible numerical simulations on much coarser computational grids.     

Vertical exchange in the ocean

We analyze the expressions for vertical turbulent flows and the coefficients of turbulent exchange in the ocean and their dependences on the stratification of density. It is shown that, in the case of high density gradients, turbulent mixing is localized in separate bounded relatively small zones (turbulized spots or layers). Formulas for typical vertical sizes of turbulent spots and local coefficients of vertical turbulent exchange depending on the Väisälä-Brunt frequency are presented. We consider a model of vertical turbulent exchange for the case of spot-like intermittent turbulence (a similar model was independently developed at the Marine Hydrophysical Institute of the Ukrainian Academy of Sciences with certain differences in the statement the problem and methodology). We emphasize the priority of A. G. Kolesnikov in the investigations of vertical turbulent exchange in the ocean by the direct method, in the development and construction of quick-response measuring devices with detectors of pulsations of the components of velocity and temperature, and in the first determination of the characteristics of turbulence in lakes, seas, and oceans performed by using this equipment.     

Mercury concentration in the ocean

Seventy percent of 342 seawater samples collected in the Bering Sea, North and South Pacific, Japan Sea, East and South China Seas, and Indian Ocean had concentrations of “total” mercury ranging from 3 to 6 ng Hg l^?1 with an arithmetic mean of 5.3 ng l^?1 and a geometric mean of 5.0 ng l^?1. In some cases, a higher concentration was observed at the surface, at the halocline or thermocline, or in the bottom water. But in general, there was no consistent correlation between mercury concentration and depth, except for a statistical tendency for mercury concentration to be slightly higher in the surface water. This tendency suggests that mercury in the ocean is supplied from the atmosphere by rain washout. The latitudinal variation of surface mercury concentrations showed that the maximum concentration at each latitude decreased from 40°N to 30°S. This variation provides evidence that atmospheric mercury is emitted mainly from continental areas naturally or anthropogenically.     

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.     

Particulate organic carbon in the global ocean derived from SeaWiFS ocean color

Satellite remote sensing offers new means of quantifying particulate organic carbon, POC, concentration over large oceanic areas. From SeaWiFS ocean color, we derived 10-year data of POC concentration in the surface waters of the global ocean. The 10-year time series of the global and basin scale average surface POC concentration do not display any significant long-term trends. The annual mean surface POC concentration and its seasonal amplitude are highest in the North Atlantic and lowest in the South Pacific, when compared to other ocean basins. POC anomalies in the North Atlantic, North Pacific, and global concentrations seem to be inversely correlated with El Niño index, but longer time series are needed to confirm this relationship. Quantitative estimates of POC reservoir in the oceanic surface layer depend on the choice of what should represent this layer. Global average POC biomass is 1.34 g m^?2 if integrated over one optical depth, 3.62 g m^?2 if integrated over mixed layer depth, and up to 6.41 g m^?2 if integrated over 200-m layer depth (when assumed POC concentration below MLD is 20 mg m^?3). The global estimate of total POC reservoir in the surface 200-m layer of the ocean is 228.61×10¹³ g. We expect that future estimates of POC reservoir may be even larger, when more precise calculations account for deep-water organic-matter maxima in oligotrophic regions, and POC biomass located just below the seasonal mixed layer in spring and summer in the temperate regions.     

Eddy-resolving ocean circulation in the Asian-Australian region inferred from an ocean reanalysis effort

The first global ocean reanalysis with focus on the Asian-Australian region was performed for the period October 1992 to June 2006. The 14-year experiment assimilated available observations of altimetric sea-level anomaly, satellite SST and quality-controlled in situ temperature and salinity profiles from a range of sources, including field surveys and the Argo float array. This study focuses on dominant circulation patterns in the South-East Asian/Australian region as simulated by an eddy-resolving and data-assimilating ocean general circulation model. New estimates of the ocean circulation are provided which are largely in agreement with the limited number of observations. Transports of key currents in the region are as follows: The total (top-to-bottom) annual mean Indonesian Throughflow transport and its standard deviation are 9.7 ± 4.4 Sv from the Pacific to the Indian Ocean with a minimum in January (6.6 Sv) and a maximum in April (12.3 Sv). The Leeuwin Current along the west coast of Australia is dominated by eddy structures with a mean southward transport of 4.1 ± 2.0 Sv at 34°S. Along the southern coast of Australia a narrow shelf edge current known as the South Australian Current advects 4.5 ± 2.6 Sv eastward at 130°E. The South Australian Current converges east of Tasmania with the eddy-rich extension of East Australian Current. At 32°S this current transports 36.8 ± 18.5 Sv southward. A dominating feature of the circulation between north-eastern Australia and Papua-New Guinea is the strong and quasi-permanent Coral Sea Gyre. This gyre is associated with the highly variable Hiri Current which runs along the south coast of Papua-New Guinea and advects 8.2 ± 19.1 Sv into the Western Pacific Ocean. All of these transport estimates are subject to strong eddy variability.     

海洋酸化研究进展

<正>海洋是巨大的碳库,不断地从大气吸收CO2,工业革命以来,海洋吸收了人类向大气排放CO2的30%~40%[1]。海洋吸收的CO2对于缓解全球变暖起着重要的作用,但是它破坏了海洋自身碳酸盐的化学平衡,导致海水酸度增加。这种由于海洋吸收了大气中人为CO2引起的海水酸度增加过程,被称为海洋酸化。目前全球海洋正处于5500万年以来海洋酸化速度最快的时期,工业革命以来,全球表层海水pH已     

Utilization of the energy in ocean waves

The characteristics of ocean wind waves place certain constraints upon devices designed to convert their energy to a useful form. Here we consider the nature of these constraints and the theoretical analysis of a wave power generator that conforms to the design criteria. We also present the results of field tests with several models of the wave power generator. The experimental results support the theory and indicate that such a wave pump is suitable for power generation in a variety of circumstances.     

Measurement of tsunamis in the open ocean

Abstract

The spectrum of long waves, which are a background to tsunamis, is analyzed on the basis of records of near‐bottom pressure sensors obtained in the Northwest Pacific during the first and second USA‐USSR expeditions on the investigation of tsunamis in the open ocean (1975 and 1978). Instrumental trends, tidal oscillations, and quasistationary longwave noise were contained in the records. Special filters were used to pick out small waves generated by the seismicity of the ocean bottom. A decrease of noise level from 10² cm (including tides) to 10°¹ cm could be reached. The level of long‐wave noise is found to depend on the instrument's location. Minimal disturbances in the records were observed at stations situated on the edge of the continental slope. The influence of cyclones passing over the instrument's site is deduced. It shows an increase in noise level on Nyquist frequency (0.5 min°¹), which possibly is caused by the action of swell generated by the cyclone. Seismicity of the region under investigation for the second expedition (August‐October 1978) is described, and the recurrence of tsunamis is estimated, including microtsunamis. Taking into account this analysis, records were filtered and sections corresponding to probable arrivals of tsunamis from most strong earthquakes were selected. The anomalous disturbance of ocean level with a height of about 0.5 cm was found. Presumably, it was generated by an earthquake with magnitude M = 6.     

Measurement of krypton-85 in the ocean

To measure ⁸⁵Kr in the ocean, methods have been developed to extract gases from large volumes of water, to isolate trace quantities of krypton from these extracted gases, and to measure low levels of ⁸⁵Kr radioactivity. Gases are extracted with an efficiency of 91% by a continuous flow, vacuum extraction technique which operates at a water flow rate of 7 l min⁻¹. Typically, 4 l of gas are extracted from a 250-l seawater sample. Using a combination of chemical reactions and gas chromatography, approximately 20 μl of krypton and 100 ml of argon are isolated from a 4-l gas sample, with recoveries in excess of 95 and 99%. ⁸⁵Kr radioactivity is measured with miniature gas proportional counters (1 ml volume). The counting efficiency ranges from 63 to 70% and the counter background ranges from 0.03 to 0.06 cpm. The minimum detectable amount of ⁸⁵Kr is 0.4 dpm/ml Kr and the precision for surface water samples is ± 4%. The dynamic range of the measurement is approximately 100.     

Coupling winds to ocean surface currents over the global ocean

A Wind stress–Current Coupled System (WCCS) consisting of the HYbrid Coordinate Ocean Model (HYCOM) and an improved wind stress algorithm based on Donelan et al. [Donelan, W.M., Drennan, Katsaros, K.B., 1997. The air–sea momentum flux in mixed wind sea and swell conditions. J. Phys. Oceanogr. 27, 2087–2099] is developed by using the Earth System Modeling Framework (ESMF). The WCCS is applied to the global ocean to study the interactions between the wind stress and the ocean surface currents. In this study, the ocean surface current velocity is taken into consideration in the wind stress calculation and air–sea heat flux calculation. The wind stress that contains the effect of ocean surface current velocity will be used to force the HYCOM. The results indicate that the ocean surface velocity exerts an important influence on the wind stress, which, in turn, significantly affects the global ocean surface currents, air–sea heat fluxes, and the thickness of ocean surface boundary layer. Comparison with the TOGA TAO buoy data, the sea surface temperature from the wind–current coupled simulation showed noticeable improvement over the stand-alone HYCOM simulation.     

Non-hydrostatic Kelvin waves in the ocean

A theory of the coastal Kelvin wave is presented in which the pressure is assumed not to be hydrostatic. The results show that the non-hydrostatic Kelvin wave is dispersive and that the e^–1 decay distance of the wave amplitude from the coast decreases as the wave length becomes shorter. Similar conclusions can be drawn on the equatorial Kelvin wave.