Pacific Surface Waters Research Articles

Carbon isotope records from pacific surface waters and atmospheric carbon dioxide

We have stacked planktonic carbon isotope data from three cores in the western equatorial Pacific in order to generate a new reconstruction of atmospheric carbon dioxide over the past 450,000 years. Our new reconstruction resembles that of Shackleton et al. (1983) based on data from East Pacific core V19-30, which successfully predicted features that were subsequently verified by Barnola et al. (1987) in the record from the Vostock ice core. In addition the new data confirm the discovery of Shackleton and Pisias (1985) that changes in atmospheric CO 2 lead changes in ice volume and hence probably contributed to the glacial-interglacial cycles. Our new reconstruction avoids some of the deficiencies of the previous reconstruction: in particular the planktonic species ( Neogloboquadrina dutertrei), on which the earlier reconstruction depends, does not calcify in truly nutrient-free surface water as the model assumes, whereas our new reconstruction uses Globigerinoides sacculifer which is expected to be more reliable. In addition, the surface waters in the west Pacific are closer to the nutrient-free ideal on which the model (Broecker, 1982) depends. On the other hand, the amplitude of the new reconstruction is significantly smaller than the amplitude observed by Barnola et al. (1987). It is not clear whether this smaller range is a better estimate of the amplitude of the ‘biological pump’ effect, or whether the true amplitude is reduced by bioturbation in the west Pacific cores that we studied.

Effects of iron, manganese, copper, and zinc enrichments on productivity and biomass in the subarctic Pacific

Natural plankton populations from subarctic Pacific surface waters were incubated in 7-d experiments with added concentrations of Fe, Mn, Cu, and Zn. Small additions of metals (0.89 nM Fe, 1.8 nM Mn, 3.9 nM Cu, and 0.75 nM Zn) were used to simulate natural perturbations in metal concentrations potentially experienced by marine plankton. Trace metal concentrations, phytoplankton productivity, Chl a, and the species composition of phytoplankton and microzooplankton were measured over the course of the experiment. Although the controls indicated little growth, increases in phytoplankton productivity, Chl a, and cell densities were dramatic after the addition of 0.89 nM Fe, indicating that it may limit the rates of algal production in these waters. Similar increases were observed in experiments with 3.9 nM Cu added. The Cu effect is attributed to a decrease in the grazing activities of the microzooplankton (ciliates) and increases in the rates of production. Mn enrichment had its greatest effect on diatom biomass, whereas Zn enrichment had its greatest effect on other autofluorescent organisms. The extent of trace metal adsorption onto carboy walls was also evaluated. These results imply that natural systems may be affected as follows: natural levels of Fe and Cu may influence phytoplankton productivity and trophic structure in open-ocean, high-nutrient, low-biomass systems; rates of net production are not limited by one micronutrient alone. Because of the effects of adsorption and complexation, experiments must be carefully monitored for free vs. total metal concentrations, and short-term incubations (1 d) may not be affected dramatically by small perturbations in trace metal micronutrients.

Chemical pollution of the northwest Pacific

Data on the distribution of anionic detergents and petroleum hydrocarbons in the northwest Pacific surface waters are presented. Higher concentrations of these pollutants were observed in the Sea of Japan and in the Kuroshio region. The average content of total non-polar petroleum hydrocarbons, measured by IR spectrophotometry, was decreased from 26 ppb in 1980–1982 to 15 ppb in 1986–1988.

Southern Ocean circulation and global climate in the Middle Pleistocene (early Brunhes)

Compilation of published data has enabled the reconstruction of the Southern Ocean circulation regime in the Middle Pleistocene between approx. 0.7 and 0.4 m.y. B.P. (early Brunhes). Possible links with northern hemisphere climate are indicated. These data show that Southern Ocean circulation was characterized by: (1) an enhanced Antarctic Circumpolar Current; (2) expansion of Antarctic Surface Water as well as; (3) Antarctic Bottom Water, but by; (4) a reduction of Antarctic Intermediate Water flow at levels of its present depth stratum. It is inferred that at the same time northern hemisphere atmospheric circulation was strongly zonal and displaced to the north. The pattern suggests an upper layer flow in the Atlantic with Gulf Stream waters characterized by lowered T/S values. North Pacific surface waters are concluded to have had higher salinities. In the Southern Ocean a stronger Circumpolar Current can primarily be related to intensified atmospheric circulation associated with an increased ocean to atmosphere heat and moisture flux. Together with enhanced Antarctic Bottom Water formation the latter conditions are indicative of low pycnocline stability. Sea ice formation around Antarctica was probably retarded. Enhanced Southern Ocean convection is assumed to have been linked to a change of the North Atlantic Deep Water T/S signature. A lowering of North Atlantic Deep Water salinity is thought to have originated from lowered T/S values characterizing Gulf Stream waters as well as from increased sinkwater formation in a more ice-free Arctic Ocean. A larger Antarctic ice volume to be ascribed to increased precipitation is proposed to explain lower interglacial sea level stands reported. In addition to generally enhanced convection, larger floating ice shelves may also have favoured Antarctic Bottom Water formation. Interglacial 18O enrichment observed in oxygen isotope records prior to stage 9 (11) is considered to reflect such an increased ice volume on Antarctica. Not only the equatorial region, but also the mid-latitudes of the northern hemisphere are concluded to have had a climatic regime marked by increased moisture starvation.

The salinity contrast between the Atlantic and Pacific oceans during glacial time

In today's ocean the salinity of low‐latitude surface waters in the Pacific is on the average 1 per mil lower than in the Atlantic. Oxygen isotope records for planktonic foraminifera suggest that an even larger salinity deficit may have existed for Pacific surface water during glacial time. If so, the transport of water vapor from the Atlantic to the Pacific must have been as strong as or even stronger. To balance the tendency toward salt buildup the Atlantic would have had to export, during glacial time, waters saltier than it received from the other oceans.

The impact of atmospheric aerosols on trace metal chemistry in open ocean surface seawater: 2. Copper

Atmospheric deposition contributes copper to the surface ocean. The biogeochemical importance and fate of this copper is poorly understood for open ocean regions. Atmospheric aerosols collected at Enewetak Atoll, in the tropical North Pacific, were exposed to seawater and artificial rainwater in laboratory experiments. Aerosol copper during the high‐dust season at Enewetak Atoll is made up of aluminosilicate, oceanic, and possibly soil organic matter components. During the low‐dust season, aerosol copper appears to be essentially all of oceanic origin. Virtually all nonaluminosilicate copper in marine aerosols collected at Enewetak is soluble in seawater. Dissolved organic matter and possibly cations in seawater increase the dissolution of aerosol copper. The net atmospheric flux of soluble copper to the tropical North Pacific near Enewetak is approximately 0.13 nmol cm−2 yr−1 out of a total net atmospheric copper flux of 0.14 nmol cm−2 yr−1. Atmospheric deposition supplies roughly the same quantity of soluble copper to tropical open North Pacific surface waters as does upwelling to eastern North Pacific surface waters. Atmospheric copper deposition, which appears to be primarily of natural origin, may be the most important input of copper to the surface waters of the central gyre of the North Pacific.

Determination of thorium isotopes in seawater by using preconcentration of thorium-XO complexes on XAD-2 resin

Thorium isotopes in seawater are determined by means of adsorption of the Xylenol Orange /XO: H6A/ complex onto XAD-2 resin at pH=3 and the XO concentration of 10−5M, and subsequent purification using an anion-exchange resin, and finally with alpha-spectrometry. The dissolved232Th concentration in the western North Pacific surface water is found to range from 0.8 to 1.2 μBq l−1. The adsorbed species of the Th-XO complex under the experimental conditions has a composition of Th/H2A/2 according to the mass balance analysis.

Variation of carbon dioxide partial pressure in the western North Pacific surface water during the 1982/83 El Niño event

Variation of carbon dioxide partial pressure in the western North Pacific surface water during the 1982/83 El Niño event

Vertical profile of lead isotopic compositions in the north-east Pacific

Ratios of lead isotopes (^(204)Pb, ^(206)Pb, ^(207)Pb and ^(208)Pb) may be used to distinguish leads from different sources in sea water in a manner similar to neodymium isotopes. The following data from the north-east Pacific include the first vertical profile measurements of lead isotopic compositions in sea water. These preliminary data indicate that lead in offshore (48° N, 141° W) north-east Pacific surface waters (^(206)Pb/^(207)Pb = 1.164) was derived from aeolian inputs of Asian (Japanese) industrial leads (^(206)Pb/^(207)Pb = 1.160) (M. Murozumi, personal communication), but that lead in water immediately (400 m) below it (^(206)Pb/^(207)Pb = 1.211) was derived from North America industrial leads (^(206)Pb/^(207)Pb = 1.222). This remarkable contrast in isotopic compositions over such a relatively short distance reveals the potential of lead isotopic compositions to resolve the importance of horizontal transport processes on the lead cycle in the oceans, which were recently proposed to partially account for its oceanographic variability in the North Pacific.

Cycles of chemical substances in the atmosphere, the Sea and the sea-floor

Since 1960 when I was a senior student, I have studied natural phenomena observed in the hydrosphere and atmosphere by means of chemical elements. Each of the phenomena is, in general, very complicated and so I have attempted to depict the whole picture of material circulation in the marine environment by studying its various aspects at the same time. My chief strategy has been to use natural radio-nuclides as clocks of various phenomena, and to use sediment traps for the determination of vertical fluxes in the ocean. The many results I have obtained can be summarized as follows. 1. I have found that several sporadic events control the material exchange through the atmosphere. These include the strong winter monsoon and typhoons that transport sea-salt particles to the Japanese Islands, theKosa episodes that transport soil dust to the ocean, and storms that result in exchange of sparingly soluble gases such as oxygen and carbon dioxide at the air-sea interface. I have also proved quantitatively that the source of aluminosilicate material in pelagic sediments is air-borne dust. 2. I have proposed a model,Settling model, for the removal of chemical substances from the ocean and found various lines of evidence supporting the model. This model predicts the reversibility in the existing state of insoluble chemical elements in seawater among large settling particles, small suspended particles and colloidal particles that pass through a membrane filter and explains well their behavior in the ocean. I have first precisely measured calcium and iodine in the ocean and have explained their distributions on the basis of the solution and redox equilibria. 3. Using chemical tracers, I have estimated the vertical eddy diffusion coefficients to be 1.2 cm2sec−1 for the Pacific deep water, 0.5 cm2sec−1 for the deep Bering Sea water and 3–80 cm2sec−1 for the Pacific surface water, and have studied the structure of water masses in the western North Pacific and the Sea of Japan. I have also invented and applied a method for the calculation of the age of deep waters using radiocarbon. 4. I have calculated the rates of decomposition of organic matter and the regeneration rates of chemical components in the deep and bottom waters as well as coastal waters by modelling water circulation and mixing. Particulate fluxes and regeneration rates are larger in the deep waters beneath the more biologically productive surface waters. I have stressed the role of silicate in the marine ecosystem, especially in the succession of phytoplankton species. 5. I have quantitatively studied the migration of chemical elements during the early diagenesis of bottom sediments especially manganese using chemical and radiochemical techniques. Manganese is being actively recycled not only in coastal seas but also in pelagic sediments except in the highly oligotrophic subtropical ocean. This recycling can explain the formation of manganese nodules and enables us to balance the manganese budget in the ocean.

Radium-228 in the Japan Sea

The distribution of228Ra in surface and subsurface waters in the Japan Sea was studied. The concentrations of228Ra in surface waters were around 100 dpm/1000l which were much higher than those reported for Pacific surface waters. The concentrations of228Ra decreased with increasing depth to less than 10 dpm/1000l in the Japan Sea Proper Water. Based on the comparison between observed values of228Ra and calculated profile through the near-surface water mass and the underlying main water mass in the Japan Sea, the apparent vertical eddy diffusion coefficient was estimated to be about 2 cm2 s−1.

Plutonium concentrations in fish and seawater from Kwajalein Atoll.

A follow-up study has been made to assess the concentrations of 239+240Pu and 137Cs in the marine environment of Kwajalein Atoll. Fish collected from the atoll in 1972 had body burdens of plutonium that were substantially higher than concentrations in similar species from locations contaminated only with global fallout. Our recent results, however, indicated that Kwajalein lagoon seawater contained levels of plutonium more similar to global fallout levels found in north equatorial Pacific surface waters. No satisfactory explanation for the reported plutonium levels in fish from Kwajalein collected in 1972 could be deduced from the available data. The highest plutonium concentrations reported for the 1972 reef species of fish could expose man, through ingestion of marine foods, to a dose rate as high as 25% of the proposed EPA guideline for annual total transuranic dose rate to bone (3 mrad/yr over 70 yr). Our present results show the dose rate from the marine food pathway is nearer to 0.005% of the recommended EPA value and is consistent with the view that Kwajalein Atoll contains plutonium concentrations that are expected from global fallout. The magnitude of the plutonium levels reported in fish collected from Kwajalein lagoon during 1972 was excessively high, and these results appear to be inconsistent with other environmental data from the lagoon. Our results also show that concentration factors for plutonium in fish muscle and bone tissues appear to be independent of species, trophic level and location, which leads us to believe that there is a great deal of validity in the concept of a concentration factor for estimating concentrations of plutonium in fish.

Radium and thorium isotopes in the surface waters of the East Pacific and coastal Southern California

A fiber extraction technique is used to concentrate Ra and Th isotopes from 1000 liters or more of seawater. Natural 226Ra and 234Th are used as yield tracers. In the equatorial Pacific the 228Ra activity of surface water varies from 20 to 1 dpm/1000 kg and generally decreases away from continental shelf areas. Across the Peru Current System, this decrease is modeled as one-dimensional diffusion and indicates the possibility of two flow regimes with distinct characteristic mixing lengths and apparent eddy diffusivities of 10 5 and 10 7 cm 2/s. The perturbing effects of advection and equatorial upwelling west of the Galapagos Islands are noted. Off the coast of Southern California a vertical 228Ra distribution gives an apparent diffusivity of 1.6 cm 2/s for the upper thermocline. 226Ra concentrations near the coast appear to be higher than the open ocean values at comparable depths, which may reflect supply of this isotope from continental shelf sediments and/or upwelling. The insoluble daughter/soluble parent activity ratios 228Th/ 228Ra and 234Th/ 238U in the equatorial Pacific surface water display latitudinal trends which may be correlated with productivity variations. Near the coast of California these ratios reflect the differing oceanographic conditions north and south of Pt. Conception indicating a mean chemical removal time constant on the order of 4 months for Th and other highly reactive elements within the Southern California Bight. The 232Th content of seawater sampled is less than 0.1 μg/1000 1; most of the published values for seawater 232Th could well be too high. A comparison of the two methods of determining 228Ra (via 228Ac and via 228Th) made on 64 seawater samples shows that the time delay required by the 228Th method is more than compensated by its better analytical simplicity and precision.

Investigations of gram quantities of Atlantic and Pacific surface particulates

Particulates amounting to 0.1–2.0 g efficiently collected from large volumes of Atlantic and Pacific surface waters have been analyzed for carbonate, opal, quartz and several natural and man-made radioisotopes. The concentrations of particles range between 10 and 600 μg/kg. In the equatorial regions particle concentrations are low and similar in both the oceans. At higher latitudes (>30°N or S), the Atlantic waters, however, have higher concentrations of particles compared to those in the Pacific. The latitudinal distribution exhibits a north-south symmetry with higher concentrations in the 30°–60° belt. Based on the particulate abundance for CaCO 3 and opal and their sedimentation, we have estimated their production and in-situ integrated dissolution rates for a few regions. Radioisotopes having different source functions, namely 14C and 239Pu injected due to nuclear weapon tests, 234Th, 230Th and 228Th produced in-situ in seawater, 232Th which derives primarily from land, 210Pb introduced via wet precipitations and 226Ra introduced through diffusion from deep-sea sediments have been measured in the particulates. The relative enrichment factors for these nuclides in particles vary as Th ⋍ Pu > Pb > Ra. The atmospheric bomb fallout pattern is discernible in the surface particulates; the 239Pu concentration increases with latitude in both the hemispheres; however, the values are about a factor of two lower in the southern hemisphere. The distribution pattern of radioisotopes is found to be complex, even for 234Th whose source function in the oceans is uniform. In view of the differences in the source functions it becomes possible to delineate the principal geochemical/geophysical processes which determine the concentrations of these nuclides in surface waters.

Carbon dioxide partial pressures in North Pacific surface waters. 2. General late summer distribution

Observations of the equilibrium partial pressure of carbon dioxide in the surface waters of the North Pacific Ocean and Bering Sea indicate conditions of local upwelling or vertical mixing near the Aleutian Island passes, seasonal depletion of CO 2 in the sea surface by photosynthesis, and conditions of CO 2 supersaturation in the surface waters off the mouths of large rivers. Horizontal mixing has a large effect on the P CO 2 distribution. The area distribution of carbon dioxide in the surface waters of the Pacific Ocean from 19°N to 55°N latitude and in the Bering Sea is presented.

本邦河川水中のトリウム同位体含量

Concentrations of thorium isotopes 232Th,230Th and "sTh were determined in the river water collected at ten main rivers in Japan. The concentration of dissolved 232Th in river water was one order of magnitude higher than that in the Pacific surface waters. The weighted averages were 2.7x 10-8 g/l for 232Th and 2.8x 10-13 g/l for ""Th. The constancy in 232Th and 230Th concentration with time was observed, but the concentration of 228Th in river water was quite variable. Accordingly,228T h/232Th activity ratio showed a wide range of variation from 37 to 0.65 during the period of study.

Carbon dioxide partial pressures in North Pacific surface waters — Time variations

Observations were made of time variations of the carbon dioxide partial pressures (Pco2) of the atmosphere and surface sea waters in the Pacific subarctic region. Data were obtained on a cruise of the USC & GSSSURVEYOR in October, 1968 and on the TRANSPAC expedition of the CNAVENDEAVOUR in March–April, 1969. A rise in surface water Pco2 of 18×10−6 atm occurred in a period of 30–45 days in March–April due principally to spring warming of surface waters. An average increase of 60×10−6 atm occurred between October, 1968 and March, 1969 as a result mainly of cessation of summer phytoplankton production and the onset of winter-storm-driven vertical mixing. Because the air-sea Pco2 gradient not only changed appreciably in magnitude but also changed sign, there are important implications for calculations of air-sea exchange of carbon dioxide on the ocean wide scale.

Preliminary Results of Measurements of Deep Currents in the Pacific Ocean

FROM June 18 to August 5, 1968, the STYX expedition of the Scripps Institution of Oceanography made measurements of deep flow in the South Pacific Ocean. As early as 1871 (ref. 1) it had been suggested that the deep and bottom waters of the North Pacific Ocean are not formed by modification of North Pacific surface waters, but have flowed in through the South Pacific from other areas. Wust2 has traced the flow of cold bottom water (deeper than 4,000 m) from the Antarctic Circumpolar Current to the western North Pacific; the observed temperature variation beyond was too small to indicate a clear path. Other investigators3,4 have confirmed his results by the distributions of dissolved oxygen and salinity, and some further indirect evidence of a deep strong northward flow across 29° S has recently been submitted5,6.

Some data on the systematics of the family Limnoriidae (Isopoda) from northern and far eastern seas of the USSR : Kussakin O. G., 1963. Crustaceana, 5 (4): 281–292

The methane concentration and pCO2 in surface waters and the overlying marine air were continuously surveyed along the pathway of the Kuroshio, from the eastern coast of Honshu to Taiwan, and then across the eastern part of the East China and South China Seas in September of 1994. Off Honshu, the CH4 content was controlled by the confluence of the relatively CH4-poor waters of the Kuroshio and the Oyashio and the CH4-rich Tsugaru Warm Current, the latter carrying water into the Pacific Ocean with a methane content more than twice the equilibrium value with the atmospheric CH4 partial pressure. Along the Kuroshio, the surface water was supersaturated in methane with respect to the atmosphere by 10–15% and appears considerably enriched relative to open Pacific surface waters at same latitudes. The northeastern part of the South China Sea, part of the deep basin of this marginal sea, showed CH4 concentrations similar to those found in open-ocean waters. In contrast, highly variable oversaturations up to 700% were observed along the northwestern coast of Borneo, most probably related to known seepage from oil and gas deposits in this area.The pCO2 of surface water was higher than the atmospheric pCO2 throughout the area surveyed. However, the ΔpCO2 of the surface waters varied from close to 0 to more than 60 μatm. The observed oversaturation in areas influenced by the Kuroshio confirm that, during a short period in late summer, the surface waters of this current between Taiwan and Japan act as a moderate source for atmospheric CO2.

Correction [to “Tritium variations in North Pacific surface waters” by Arnold E. Bainbridge

Correction [to “Tritium variations in North Pacific surface waters” by Arnold E. Bainbridge