Shizuo Tsunogai

Increase in Total Carbonate in the Western North Pacific Water and a Hypothesis on the Missing Sink of Anthropogenic Carbon

Sea water samples were collected from various depths in the North Pacific (40–21°N) along 165°E in 1991. Their total carbonate (total dissolved carbonate species) contents were determined with random errors less than 0.2% by a coulometric method. The preformed carbonate contents defined by Chen (1982) were calculated from the obtained data and other observed data including potential temperature, salinity, dissolved oxygen and total alkalinity. The same calculation was done for the GEOSECS data obtained in nearly the same region in 1973. The difference between the two data sets reveals that the preformed carbonate has increased by 180±41 gC/m2 during the last 18 years. This value is comparable or somewhat larger than 150 gC/m2 obtained in the case that the ocean uptakes 3 GtC/yr for 18 years and distributes it equally among the world oceans. Based on the results, a hypothesis on the missing sink for the anthropogenic carbon dioxide is presented, in that the missing sink is the intermediate waters formed in the northern North Pacific and the Southern Ocean besides the deep waters formed in the North Atlantic and the Southern Ocean.

Formation of iodide-iodine in the ocean

Abstract A mechanism which accounts for the formation of iodide in the ocean has been demonstrated by bacterial and enzymatic experiments. Iodate can be reduced by those marine bacteria which are able to reduce nitrate and by extract from E. coli which contains nitrate reductase. Some reduced iodine may be excreted as free iodine from marine bacteria. Iodate seems to be reduced in surface-water by organisms having a nitrate reducing activity. The process plays a major role in the circulation of iodine through the atmosphere and the hydrosphere.

226Ra, 210Pb and 210Po disequilibria in the Western North Pacific

Abstract 226 Ra, 210 Pb and 210 Po were measured in oceanic profiles at two stations near the Bonin and Kurile trenches. 210 Po is depleted by 50% on average relative to 210 Pb in the surface water. In the deep water, 210 Pb is about 25% deficient relative to 226 Ra. Based on the deficiency, 210 Pb residence time with respect to removal by particulate matter was estimated to be less than 96 years in the deep water. 210 Pb deficiency in the bottom water was significantly greater than that of the adjacent deep water, indicating more effective removal near or at the bottom interface. 210 Pb, 210 Po and Th appear to have similar overall rate constants of particulate removal throughout the water column.

Seasonal and areal variation of continental aerosol in the surface air over the western North Pacific region

Weekly aerosol samples were collected for two years from 1981 at six stations in the western North Pacific region. The samples were analyzed for aluminum to determine the mineral dust concentration in the air. By combining our data with observations in the central and eastern North Pacific by a US research group, the following results and conclusions have been obtained. Spring peaks in atmospheric mineral dust were observed at all the stations accompanied byKosa episodes (hazes due to mineral dust of Chinese origin). The spring peaks, however, varied from year to year. The mean concentration of mineral dust depends not only on the distance from the Asian coast but also on the latitude of the sampling station. The half-decrease distance of the atmospheric mineral dust turned out to be 500–600 km for all latitudes in the western North Pacific. This indicates that the rate of deposition of mineral dust in the western North Pacific is much larger than that in the central and eastern North Pacific.

Tritium in the Japan Sea and the renewal time of the Japan Sea deep water

Watanabe, Y.W., Watanabe, S. and Tsunogai, S., 1991. Tritium in the Japan Sea and the renewal time of the Japan Sea deep water. Mar. Chem., 34: 97-108. In 1987 in the Japan Sea, the mean concentration of tritium below 200 m depth was !.2 T.U. (Tritium Unit= 10 ~8 times of the molar fraction of tritium in ordinary hydrogen (T/H X 10 iS) ), which was one third of that in the surface water from 0 to 200 m depth (3.6 T.U.). Tritium was even found near a depth of 2000 m at two stations; 0.5 and 0.9 T.U., values which were outside the analytical error ( _+0.3 T.U.). These results indicate that vertical mixing is more rapid in the Japan Sea than in the Pacific Ocean where the concentration of tritium decreases steeply with depth and is less than the detection limit for water below 1000 m depth. By introducing these data and the previously obtained 226Ra data into a three-box model, the turnover time of the Japan Sea deep water and the residence time of the water within the Japan Sea were calculated to be about 100 years and 1000 years, respectively. The exchange coefficient of CO2 at the air-sea interface was also estimated to be 1.4--3.3 m day-~ by coupling these data with the 14C data in the three-box model. This value which is smaller than the world mean value is probably due to the fact that the region producing the Japan Sea deep water of the northern Japan Sea near the Siberian coast has rather low windspeeds.

Hydrographic features of the deep water of the Bering Sea—the sea of Silica

Abstract The deep water of the Bering Sea contains concentrations of dissolved silicate up to 240 μg at. Sil−1. Nitrate concentrations are less than in the North Pacific at the depths with the same oxygen contents. The rates of chemical and biochemical reactions occurring in the deep water (below 2km) were estimated from hydrographic data by applying a modified one-dimensional model. Oxidation of organic matter in the oxygenated water column of the Bering Sea was twice that of the North Pacific. Silicate regeneration, or dissolution of biogenic opal and denitrification, or bacterial nitrate reduction to gaseous nitrogen, on and in the bottom sediments of the deep Bering Sea basin were calculated to be 212 and 20 mg at.m−2 yr−1, respectively. These values are consistent with the ones estimated from vertical profiles of dissolved silicate and nitrate in the interstitial water of the sediments. The chemical anomaly observed in deep water of the Bering Sea can be produced by these reactions in the bottom sediments. The decomposition of organic matter in anoxic sediments accounts for about 8% of the total organic matter decomposing in the water column below 2km and in the sediments.

Iodine in the surface water of the ocean

Iodine in sea water of the Pacific was determined with special interest in the relation between iodide and iodate in the surface water of the ocean. The result was discussed with reference to the mechanism of iodide formation proposed byTsunogai andSase. The concentration of iodide varies widely from the lower value than the detection limit to 0.21μg at./l, while the concentration of total iodine is nearly constant and the mean value is 0.41μg at./l. The vertical profile of iodide often shows the maximum in the surface layer. In the surface layer, the concentration of iodide is higher in warm water (0,10μg at./l on the average) than that in cold water of lower temperature than 20° C (0.03μg at/l). The highest concentration of iodide among the warm waters is found in the surface water of the equatorial area (0.13μg at./l) where the biological productivity is also high. Iodide is generally more enriched in the water having higher biological activity even in the cold water. These results are considered to be compatible with the mechanism of iodide formation proposed.

Complexometric titration of calcium in the presence of larger amounts of magnesium

A simple and accurate titrimetric determination of calcium in the presence of larger amounts of magnesium is proposed. Calcium is extracted into a small volume of organic solvent as its glyoxal-bis(2-hydroxyanil) complex, and the calcium is titrated with EGTA. The end-point is sharp, and occurs when the red colour of the organic layer vanishes. This method has been successfully applied to the determination of calcium in sea-water with an error less than 0.1%.

Compositional change of settling particles with water depth in the Japan Sea

Abstract Settling particles at five different water depths (890–3240 m) and a box core sample were collected in September 1984 in the Japan Sea (40°49.4′N, 138°40.7′E; 3350 m deep), and analyzed for major components and 25 elements. According to the vertical changes in elemental concentrations (Me) and elemental concentration ratios to aluminum (Me/Al), these elements are grouped into four types: (1) the elemental concentration increases with water depth and the Me/Al ratio remains almost constant vertically (Al, Sc, La, Th, Hf, V, Ta, K, Rb, and Cs); (2) both the elemental concentration and the Me/Al ratio decrease with depth (I, Ba, Ca, Sr); (3) both the elemental concentration and the Me/Al ratio increase with depth (Mn); and (4) the elemental concentration remains almost constant or increases a little with depth and the Me/Al ratio decreases with depth (As, Sb, Se, and Ag). These four types are named refractory, biogenic, scavenged, and biogenic-scavenged, respectively; the fourth type is recognized here for the first time. Fe, Co, Zn, and Br show maximum Me/Al ratios within the water column but are grouped as scavenged (Fe and Co) and biogenic-scavenged (Zn and Br) elements. The concentration changes of elements in the settling particles at 3240 m relative to the surface sediment suggest that elements except those of the refractory type are regenerated or liberated on or near the sea floor.

Biological effect on removal of Th-234, Po-210 and Pb-210 from surface water in Funka Bay, Japan

Abstract Vertical and temporal variations in the radioactivities of Th-234, Pb-210 and Po-210 were measured at a station in Funka Bay from April 1979 to February 1980. The inventory of Th-234 showed a minimum in early spring, when a spring bloom of phytoplankton was observed, then a steady increase to a maximum value in late summer, just before open sea water invaded the bay and a secondary phytoplankton bloom started. The inventories of Pb-210 and Po-210 also showed minima in early spring. These results suggest that the removal of these nuclides from sea water is accelerated by biological activity. The concentration of Th-234 decreased with depth, but those of Po-210 and Pb-210 were higher in the bottom water in August 1979 when the bay water was strongly stratified. This may be due to the supply of Pb-210 and Po-210 from the bottom. However, if the supply of these nuclides is expected in sediment particles, the concentrations of these nuclides in suspended matter were not sufficient to explain their increments in the bottom water. Residence times of Th, Pb and Po were estimated by applying a non-steady state model to the bay water when the water stayed in and the concentrations of these nuclides were changing. The mean residence time of Th is not significantly different from that of Pb, but is about half of that of Po, although the difference is much smaller than that obtained by applying a steady state model.