239, 240Pu,137Cs and90Sr in the central North Pacific

^{239, 240}Pu,¹³⁷Cs and⁹⁰Sr concentrations were determined in sea waters from the central and western North Pacific in 1980 and 1982. The results are consistent with those reported earlier for North Pacific waters. The profiles of⁹⁰Sr and¹³⁷Cs show a monotonic decrease with depth, whilst^{239, 240}Pu shows a distinct subsurface maximum at a depth between 400 and 1,000 m. The calculated inventories of these nuclides significantly exceed the global mean fallout inputs for these latitudes. This may be due to local fallout input to the ocean at times of large-scale nuclear weapon tests in the equatorial North Pacific. The existence of measurable amounts of¹³⁷Cs and^{239, 240}Pu in deep waters suggests that these nuclides are transported by sinking particulate matter from the surface to the deep ocean.     

Reconstruction of pH in the Surface Seawater over the North Pacific Basin for All Seasons Using Temperature and Chlorophyll-<Emphasis Type="Italic">a</Emphasis>

We found a simple function of pH that relates to sea surface temperature (SST, K) and chlorophyll-a (Chl, µg l⁻¹) using measured surface seawater pH, SST and Chl data sets over the North Pacific: pH (total hydrogen scale at 2°C) = 0.01325 SST − 0.0253 Chl + 4.150 (R² = 0.95, p < 0.0001, n = 483). Moreover, evaluating the seasonal variation of pH based on this algorithm, we compared the measured pH with the predicted pH at the observational time series stations in subpolar and subtropical regions. The average of ΔpH (measured - predicted, n = 52) was 0.006 ± 0.022 pH. Therefore, the combination of SST and Chl can allow us to determine the spatiotemporal distribution of pH over the North Pacific. Using the climatological data sets of SST and Chl with our pH algorithms, we have described the seasonal distributions of pH at 25°C (pH₍₂₅₎) and pH in situ temperature (pH_(T)) over the North Pacific surface water.     

Spatiotemporal Decreases of Nutrients and Chlorophyll-a in the Surface Mixed Layer of the Western North Pacific from 1971 to 2000

Using time series of hydrographic data in the wintertime and summertime obtained along 137°E from 1971 to 2000, we found that the average contents of nutrients in the surface mixed layer showed linear decreasing trends of 0.001∼0.004 μmol-PO₄ l⁻¹ yr⁻¹ and 0.01∼0.04 μmol-NO₃ l⁻¹ yr⁻¹ with the decrease of density. The water column Chl-a (CHL) and the net community production (NCP) had also declined by 0.27∼0.48 mg-Chl m⁻² yr⁻¹ and 0.08∼0.47 g-C-NCP m⁻² yr⁻¹ with a clear oscillation of 20.8±0.8 years. These changes showed a strong negative correlation with the Pacific Decadal Oscillation Index (PDO) with a time lag of 2 years (R = 0.89 ± 0.02). Considering the recent significant decrease of O₂ over the North Pacific subsurface water, these findings suggest that the long-term decreasing trend of surface-deep water mixing has caused the decrease of marine biological activity in the surface mixed layer with a bidecadal oscillation over the western North Pacific.     

A mechanism of Alpine lee cyclogenesis as revealed by a quasigeostrophic variational filter

Summary Mechanisms associated with Alpine lee cyclogenesis during the early phase of their generation are investigated using a variational quasigeostrophic filter technique. It was possible to extract the quasigeostrophic signal from the available analyzed real data set.The results presented here are for the 11–12 March 1982, an example of so-called orographically induced lee cyclogenesis. Non-quasigeostrophic fields, calculated as a difference between observations and the quasigeostrophic fields, show significant magnitudes indicating the possible importance of non-quasigeostrophic processes. A dipole structure in the residual geopotential field was observed, similar to the results of numerical model experiments. Also, a strong upper-level non-quasigeostrophic divergence was found in the Alpine region 24 hours prior to lee cyclogenesis, lasting for 6–12 hours. On the other hand, quasigeostrophic results indicate only a local effect of mountain slopes, suggesting possibly a dominant role of the low-level blocking. A hypothetical scenario of Alpine lee cyclogenesis is proposed, based on results obtained here.With 14 Figures     

Evolutionary tracks of the terrestrial planets

On the basis of the model proposed by Matsui and Abe, we will show that two major factors — distance from the Sun and the efficiency of retention of accretional energy — control the early evolution of the terrestrial planets. A diagram of accretional energy versus the optical depth of a proto-atmosphere provides a means to follow the evolutionary track of surface temperature of the terrestrial planets and an explanation for why the third planet in our solar system is an aqua-planet.     

Changes in the lower limit of mountain permafrost between 1973 and 2004 in the Khumbu Himal, the Nepal Himalayas

Because the Khumbu Himal of the Nepal Himalayas lacks long-term climate records from weather stations, mountain permafrost degradation serves as an important indicator of climate warming. In 1973, the permafrost lower limit was estimated to be 5200–5300 m above sea level (ASL) on southern-aspect slopes in this region. Using ground-temperature measurements, we examined the mountain permafrost lower limit on slopes with the same aspect in 2004. The results indicate that the permafrost lower limit was 5400–5500 m ASL in 2004. The permafrost lower limit was estimated to be 5400 to 5500 m on slopes with a southern aspect in the Khumbu Himal in 1991 using seismic reflection soundings. Thus, it is possible that the permafrost lower limit has risen 100–300 m between 1973 and 1991, followed by a stable limit of 5400 to 5500 m over the last decade. An increase in mean annual air temperature of approximately 0.2 to 0.4 °C from the 1970s to the 1990s has indicated a rise in the permafrost lower limit of 40 to 80 m at the Tibetan Plateau. The rise in the mountain permafrost lower limit in the Khumbu Himal exceeds that of the Tibetan Plateau, suggesting the possibility of greater climate warming in the Khumbu Himal.     

Paleomagnetism of the middle Cretaceous Iritono granite in the Abukuma region, northeast Japan

We have studied the paleomagnetism of the middle Cretaceous Iritono granite of the Abukuma massif in northeast Japan together with ⁴⁰Ar–³⁹Ar dating. Paleomagnetic samples were collected from ten sites of the Iritono granite (102 Ma ⁴⁰Ar–³⁹Ar age) and two sites of its associated gabbroic dikes. The samples were carefully subjected to alternating field and thermal demagnetizations and to rock magnetic analyses. Most of natural remanent magnetizations show mixtures of two components: (1) H component, high coercivity (B_c > 50–90 mT) or high blocking temperature (T_b > 350–560 °C) component and (2) L component, relatively low B_c or low T_b component. H component was obtained from all the 12 sites to give a mean direction of shallow inclination and northwesterly declination (I = 29.9°, D = 311.0°, α₉₅ = 2.7°, N = 12). This direction is different from the geocentric axial dipole field at the present latitude (I = 56.5°) and the typical direction of the Cenozoic remagnetization in northeast Japan. Since rock magnetic properties indicate that the H component of the Iritono granite is carried mainly by magnetite inclusions in plagioclase, this component probably retains a primary one. Thus the shallow inclination indicates that the Abukuma massif was located at a low latitude (16.1 ± 1.6°N) about 100 Ma and then drifted northward by about 20° in latitude. The northwesterly deflection is attributed mostly to the counterclockwise rotation of northeast Japan due to Miocene opening of the Japan Sea. According to this model, the low-pressure and high-temperature (low-P/high-T) metamorphism of the Abukuma massif, which has been well known as a typical location, would have not occurred in the present location. On the other hand, the L component is carried mainly by pyrrhotite and its mean direction shows a moderate inclination and a northwesterly declination (I = 42.8°, D = 311.5°, α₉₅ = 3.3°, N = 9). Since this direction is intermediate between the H component and early Cenozoic remagnetization in northeast Japan, some thermal event would have occurred at lower temperature than pyrrhotite Curie point ( 320 °C) during the middle Cretaceous to early Cenozoic time to have resulted in partial remagnetization.     

层积云覆盖的海洋边界层云详细微物理过程的数值模拟

文中建立了一个含显式分档的云微物理模式和辐射传输模式的一维 3阶湍流闭合模式 ,该模式可用于研究海洋边界层云中气溶胶和云的相互作用过程 ,同时提出了一种新的动力模式和微物理模式耦合方法 ,该方法可使动力模式中液态水相关项可以直接由微物理模式变量计算得到。作为模式的初步应用模拟了 2 0 0 1年APEX/ACE Asia在西太平洋上所观测到的一个个例。模拟结果和观测资料比较表明该模式基本上模拟出层积云覆盖的海洋边界层的基本结构     

Laumontization and Secondary Pores of Sandstones in the Paleogene and Upper Cretaceous Coal Measures, off Northeast Honshu, Japan

Abstract. Sandstones with high reservoir quality occur in the Paleogene and Upper Cretaceous coal measures off Sanriku and Sohma in the Pacific coast of northeast Honshu. The sandstone porosity was generally produced by the dissolution of calcite cement and clastic grains such as feldspar and glassy volcanics. The most probable cause of dissolution is the organic acids generated from the maturation of coal and coaly matter in the deeply subsiding source area prior to thermogenic hydrocarbon generation. The pore fluid including organic acids dissolved calcite and clastic silicates to form a small amount of laumontite and kaolinite at around 60C. The acidic and not neutralized pore fluid was responsible for the formation of kaoli-nite. On the other hand, laumontite was formed when the acidic pore fluid was neutralized and then made alkaline after the reaction with minerals such as plagioclase, glassy volcanics and calcite cement. Therefore, laumontite and kaolinite generally occur separately. Laumontite is 0.6–4.6 % by volume, whereas kaolinite is 0.6–9.8 % and the sandstone porosity remains from 10 to 22 %. This type of laumontization after the secondary pore formation might not give a severe damage to the reservoir property of the Paleogene and Upper Cretaceous coal measures in the Pacific coast of northeast Honshu and indicates further exploration possibility.