Terrestrial heat flow in the Celebes and Sulu Seas

Five heat flow measurements were made in the Asiatic Mediterranean Sea; two in the Celebes Sea and three in the Sulu Sea. The mean of all five values of 2.0 cal/cm² sec is significantly greater than the over-all mean heat flow value for the oceans and is close to the mean value for marginal seas. The measurement indicate that there may be a difference in the flow of heat through the two seas.Contribution of the Scripps Institution of Oceanography, new series.     

Possible source of the antarctic bottom water in the Prydz Bay Region

It has been inferred that the Prydz Bay region is one of the source regions of Antarctic Bottom Water (AABW) based on rather indirect evidence. In order to examine this inference, we investigate the hydrographic condition of the bay based mainly on XCTD data obtained during the Japanese Whale Research Program in the Antarctic (JARPA). The JARPA hydrographic data reveal Circumpolar Deep Water (CDW), which is a salty, warm water mass approaching the shelf break, and capture Modified CDW (MCDW) intruding into the shelf water. AABW production requires mixing of CDW and cold shelf water saltier than 34.6 psu, which is a saltier type of Low Salinity Shelf Water (LSSW). Saltier LSSW is observed near the bottom over the shelf, being mixed with MCDW. We further identify saltier LSSW near the shelf break. This saltier LSSW appears close enough to unmodified CDW to be mixed with it over the continental slope, indicating a possible source of AABW in Prydz Bay.     

On nonlinear planetary waves: A class of solutions missed by the traditional quasi-geostrophic approximation

Weakly nonlinear quasi-geostrophic planetary waves on a beta-plane and topographic waves over a linearly inclined bottom are examined by use of shallow water equations for a small beta parameter. Long solitary wave solutions missed by the use of the traditional quasi-geostrophic approximation are found in a channel ocean with neither a sheared current nor a curved (non-linearly inclined) bottom topography. The solutions are missed in the traditional approach because the irrotational motion associated with the geostrophic divergence is neglected by the quasi-geostrophic approximation. Another example which calls attention to the limitation of the traditional quasi-geostrophic approximation is the nonlinear evolution of divergent planetary eddies whose scale is much larger than the Rossby's radius of deformation. Some aspects of a new evolution equation are briefly discussed.     

Subtropical Mode Water south of Honshu,Japan in the spring of 1988 and 1989

The distribution and characteristics of Subtropical Mode Water (STMW) south of Honshu, the main island of Japan, were investigated using CTD, XBT, and dissolved oxygen data taken by the research vessels in the spring of 1988 and 1989. A comparatively low inventory of STMW was shown in spring 1988 during the large-meander period of the Kuroshio south of Honshu, while in spring 1989 during the non-large-meander period, the observation showed a considerable inventory of STMW which had outcropped east of 140°E in the preceding winter. These observations, together with published temperature maps, surface current charts, time series of vertical temperature profiles along 140°E, and wintertime Monsoon Index consistently support the climatology of the STMW circulation recently presented by the authors. That is, the change of the Kuroshio Countercurrent associated with the large meander of the Kuroshio most likely cuts off the westward/southwestward advection of STMW from its formation area east of 140°E.     

Gallium content in seaweeds

Analyses of gallium content were made by the fluorometric method on 57 samples of seaweeds which were composed of 30 species. As the result of it, the gallium content was found ranging from 0.02 to 0.64g g^–1 and the average was 0.14g g^–1 in the dried seaweeds.Generally, the gallium content in seaweeds had a close relationship to the aluminium and iron contents. The average weight ratio of Ga/Al was 3.8×10^–4 and one of Ga/Fe was 4.0×10^–4. The average Ga/Al weight ratio (3.8×10^–4) was very similar to that reported for shallow-water deposits (2.1×10^–4), but was definitely lower than that in sea water (1.5×10^–2).     

Temporal variability of winter mixed layer in the mid-to high-latitude North Pacific

Temperature and salinity data from 2001 through 2005 from Argo profiling floats have been analyzed to examine the time evolution of the mixed layer depth (MLD) and density in the late fall to early spring in mid to high latitudes of the North Pacific. To examine MLD variations on various time scales from several days to seasonal, relatively small criteria (0.03 kg m⁻³ in density and 0.2°C in temperature) are used to determine MLD. Our analysis emphasizes that maximum MLD in some regions occurs much earlier than expected. We also observe systematic differences in timing between maximum mixed layer depth and density. Specifically, in the formation regions of the Subtropical and Central Mode Waters and in the Bering Sea, where the winter mixed layer is deep, MLD reaches its maximum in late winter (February and March), as expected. In the eastern subarctic North Pacific, however, the shallow, strong, permanent halocline prevents the mixed layer from deepening after early January, resulting in a range of timings of maximum MLD between January and April. In the southern subtropics from 20° to 30°N, where the winter mixed layer is relatively shallow, MLD reaches a maximum even earlier in December–January. In each region, MLD fluctuates on short time scales as it increases from late fall through early winter. Corresponding to this short-term variation, maximum MLD almost always occurs 0 to 100 days earlier than maximum mixed layer density in all regions.     

Evolution of an isolated eddy near a coast and its relevance to the “Kyucho”

The evolution of an isolated meso-scale eddy near a coast is studied numerically. In particular, it is found that the translation speed of the adjusted eddy is estimated well by the mutual induction mechanism adapted to a rotating stratified fluid. The nonlinear Kelvin wave excited during the adjustment process is also discussed in connection with the Kyucho, the sudden warming of coastal waters associated with swift currents.     

Energy spectrum and pitch angle distribution of particles reflected by MHD shock waves of fast mode

To study the macroscopic acceleration process for non-thermal particles at the front of MHD shock waves, two limiting treatments, namely the “adiabatic” and the “kink” treatments have been developed. They correspond to cases of (particle gyroradius)/(width of shock transition region) ? 1 and ? 1, respectively. The effects of the acceleration process on energy and pitch angle distributions of reflected particles are examined by using each of these treatments and results are compared. It is shown that these two treatments give almost the same energy and pitch angle distribution in the case of nearly-perpendicular shock waves. In the case of nearly-parallel shock waves, the pitch angle distributions differ significantly, there being reflected particles in the adiabatic loss cone when the kink treatment is employed, while the ranges of the energy distribution for these two treatments do not differ greatly. Analytic representation for the acceleration in the adiabatic treatment is given for the later usage.     

Mechanisms for anhydrite and gypsum formation in the Kuroko massive sulfide–sulfate deposits,north Japan

The Sr, Ba, and rare earth elements (REEs) concentrations and Sr isotopic composition of anhydrite and gypsum have been determined for samples from the Matsumine, Shakanai, and Hanaoka Kuroko-type massive sulfide–sulfate deposits of northern Japan to evaluate the mechanisms of sekko (anhydrite and gypsum) ore formation. The Sr isotopic compositions of the samples fall in the range of 0.7077–0.7087, intermediate between that for middle Miocene (13–15 Ma) seawater (0.7088) (Peterman et al., Geochim Cosmochim Acta, 34:105–120, 1970) and that for country rocks (e.g., 0.7030–0.7050) (Shuto, Assn Geol Collab Japan Monograph 18:91–105, 1974). The Kuroko anhydrite samples exhibit two types of chondrite-normalized REE patterns: one with a decrease from light REEs (LREEs) to heavy REEs (HREEs) (type I), and another with a LREE-depleted pattern (type II). Based on the Sr content and isotopic ratio (assuming an Sr/Ca (mM/M) of 8.7 for seawater), anhydrite is considered to have formed by mixing of preheated seawater with a hydrothermal solution of Sr/Ca (mM/M) = ca. 0.59–1.36 under the condition in which the partition coefficient (Kd) ranges between ca. 0.5 and 0.7. This results in the formation of anhydrite with higher Sr content with an Sr isotopic value close to that of seawater under seawater-dominant conditions. Larger crystals of type II anhydrite are partly replaced by smaller ones, indicating that anhydrite dissolution and recrystallization occurred after or during the formation of sekko ore. Gypsum, which partially replaces anhydrite in the Kuroko deposits, also exhibits two distinct chondrite-normalized REE patterns. Because LREEs are likely to be more readily mobilized during dissolution and recrystallization, it is hypothesized that LREEs are leached from type I anhydrite, resulting in the formation of type II anhydrite with LREE-depleted profiles.