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27 results on '"Mitsudera, H."'

1. Mechanisms controlling dissolved iron distribution in the North Pacific: A model study

Author

Misumi, K., Tsumune, D., Yoshida, Y., Uchimoto, K., Nakamura, T., Nishioka, J., Mitsudera, H., Bryan, F. O, Lindsay, K., Moore, J. K, and Doney, S. C

Subjects
nitrogen-fixation, global ocean, world ocean, scavenging model, atlantic-ocean, kuril straits, cycle, sea, ligands, water
Abstract

Mechanisms controlling the dissolved iron distribution in the North Pacific are investigated using the Biogeochemical Elemental Cycling (BEC) model with a resolution of approximately 1° in latitude and longitude and 60 vertical levels. The model is able to reproduce the general distribution of iron as revealed in available field data: surface concentrations are generally below 0.2 nM; concentrations increase with depth; and values in the lower pycnocline are especially high in the northwestern Pacific and off the coast of California. Sensitivity experiments changing scavenging regimes and external iron sources indicate that lateral transport of sedimentary iron from continental margins into the open ocean causes the high concentrations in these regions. This offshore penetration only appears under a scavenging regime where iron has a relatively long residence time at high concentrations, namely, the order of years. Sedimentary iron is intensively supplied around continental margins, resulting in locally high concentrations; the residence time with respect to scavenging determines the horizontal scale of elevated iron concentrations. Budget analysis for iron reveals the processes by which sedimentary iron is transported to the open ocean. Horizontal mixing transports sedimentary iron from the boundary into alongshore currents, which then carry high iron concentrations into the open ocean in regions where the alongshore currents separate from the coast, most prominently in the northwestern Pacific and off of California.

Published
2011

4. Submesoscale eddies near the Kuril Straits: Asymmetric generation of clockwise and counterclockwise eddies by barotropic tidal flow

Author

Nakamura, T., Matthews, J. P., Awaji, T., Mitsudera, H., Nakamura, T., Matthews, J. P., Awaji, T., and Mitsudera, H.

Abstract

High spatial resolution thermal infrared (TIR) images derived by the LANDSAT Thematic Mapper (TM) sensors show the presence of numerous small-scale eddies near the Kuril Islands. As the diameters of these eddies range from around 2 to 30 km (i.e., submesoscale), they are much smaller than the eddies previously reported in this region (several tens to some hundreds of kilometers in diameter). Our simulations suggest that small-scale eddies similar to those observed in the satellite data are generated by diurnal barotropic tides. The eddy generation is well defined from Etorofu/Friza to the Onnekotan Straits, and it is caused by the effects of coastal boundaries and the stretching of water columns, which lead to eddy growth even after eddies have left the coast. We find that the counterclockwise eddies are generally larger in number and size and stronger in vorticity and surface height than the clockwise eddies in both the gradient and cyclostrophic wind balance regimes. The possible causes of such asymmetry are (1) the effect of planetary-vorticity tube stretching, which can be significant even when the final relative vorticity becomes much greater than planetary vorticity and (2) asymmetric advection by the rotating tidal flow, which advects counterclockwise eddies offshore but clockwise eddies onshore. These eddies induce strong stirring with a maximum apparent diffusivity of 10^[8] cm2 s^[-1]. The numbers, properties, and mixing effects of eddies vary greatly with the spring-neap cycle.

Published
2012

5. Submesoscale eddies near the Kuril Straits: Asymmetric generation of clockwise and counterclockwise eddies by barotropic tidal flow

Author

1000060400008, Nakamura, T., Matthews, J. P., Awaji, T., Mitsudera, H., 1000060400008, Nakamura, T., Matthews, J. P., Awaji, T., and Mitsudera, H.

Abstract

High spatial resolution thermal infrared (TIR) images derived by the LANDSAT Thematic Mapper (TM) sensors show the presence of numerous small-scale eddies near the Kuril Islands. As the diameters of these eddies range from around 2 to 30 km (i.e., submesoscale), they are much smaller than the eddies previously reported in this region (several tens to some hundreds of kilometers in diameter). Our simulations suggest that small-scale eddies similar to those observed in the satellite data are generated by diurnal barotropic tides. The eddy generation is well defined from Etorofu/Friza to the Onnekotan Straits, and it is caused by the effects of coastal boundaries and the stretching of water columns, which lead to eddy growth even after eddies have left the coast. We find that the counterclockwise eddies are generally larger in number and size and stronger in vorticity and surface height than the clockwise eddies in both the gradient and cyclostrophic wind balance regimes. The possible causes of such asymmetry are (1) the effect of planetary-vorticity tube stretching, which can be significant even when the final relative vorticity becomes much greater than planetary vorticity and (2) asymmetric advection by the rotating tidal flow, which advects counterclockwise eddies offshore but clockwise eddies onshore. These eddies induce strong stirring with a maximum apparent diffusivity of 10^[8] cm2 s^[-1]. The numbers, properties, and mixing effects of eddies vary greatly with the spring-neap cycle.

Published
2012

6. Implementing the Pacific Basin Extended Climate Study (PBECS)

Author

Davis, R., Kessler, W., Lukas, R., Weller, R., Behringer, D., Cayan, D., Chelton, D., Eriksen, C., Esbensen, S., Fine, R., Fukumori, I., Kiladis, G., Gregg, M., Harrison, E., Johnson, G., Lee, T., Mantua, N., McCreary, J., McPhaden, M., McWilliams, J., Miller, A., Mitsudera, H., Niiler, P., Qiu, B., Raymond, D., Roemmich, D., Rudnick, D., Schneider, N., Schopf, P., Stammer, D., Thompson, L., and White, W.

Abstract

The Pacific Basin Extended Climate Study (PBECS) is a basin-wide study of interannual-to-decadalclimate variability in and over the Pacifc Ocean. The report summarizes an implementation plan and enumerate recommendations to begin implementing PBECS.

Published
2000
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7. Simulations of chlorofluorocarbons in and around the Sea of Okhotsk : Effects of tidal mixing and brine rejection on the ventilation

Author

Uchimoto, K., Nakamura, T., Nishioka, J., Mitsudera, H., Yamamoto-Kawai, M., Misumi, K., Tsumune, D., Uchimoto, K., Nakamura, T., Nishioka, J., Mitsudera, H., Yamamoto-Kawai, M., Misumi, K., and Tsumune, D.

Abstract

Ventilation of waters in and around the Sea of Okhotsk was investigated using simulations of chlorofluorocarbons (CFCs) in the northwestern North Pacific. We used an ocean general circulation model coupled with a sea ice model. The model reproduces the distributions of CFCs similar to observed values and indicates the importance of tidal mixing along the Kuril Islands and brine rejection to ventilation of waters in and around the Sea of Okhotsk. To clarify the role of each process, numerical experiments excluding one of the two processes were carried out. Results show that brine rejection transports CFCs into the intermediate layer as deep as 200-400 m along the path of dense shelf water in the western Sea of Okhotsk, but hardly to other areas and layers. On the other hand, tidal mixing transports CFCs into the intermediate and deeper layers throughout the Sea of Okhotsk. We conclude that the tidal mixing has a greater influence than brine rejection on the ventilation of layers below the winter mixed layer.

Published
2011

8. Simulations of chlorofluorocarbons in and around the Sea of Okhotsk : Effects of tidal mixing and brine rejection on the ventilation

Author

1000010374646, Uchimoto, K., Nakamura, T., Nishioka, J., Mitsudera, H., Yamamoto-Kawai, M., Misumi, K., Tsumune, D., 1000010374646, Uchimoto, K., Nakamura, T., Nishioka, J., Mitsudera, H., Yamamoto-Kawai, M., Misumi, K., and Tsumune, D.

Abstract

Ventilation of waters in and around the Sea of Okhotsk was investigated using simulations of chlorofluorocarbons (CFCs) in the northwestern North Pacific. We used an ocean general circulation model coupled with a sea ice model. The model reproduces the distributions of CFCs similar to observed values and indicates the importance of tidal mixing along the Kuril Islands and brine rejection to ventilation of waters in and around the Sea of Okhotsk. To clarify the role of each process, numerical experiments excluding one of the two processes were carried out. Results show that brine rejection transports CFCs into the intermediate layer as deep as 200-400 m along the path of dense shelf water in the western Sea of Okhotsk, but hardly to other areas and layers. On the other hand, tidal mixing transports CFCs into the intermediate and deeper layers throughout the Sea of Okhotsk. We conclude that the tidal mixing has a greater influence than brine rejection on the ventilation of layers below the winter mixed layer.

Published
2011

9. Breaking of unsteady lee waves generated by diurnal tides

Author

Nakamura, T., Isoda, Y., Mitsudera, H., Takagi, S., Nagasawa, M., Nakamura, T., Isoda, Y., Mitsudera, H., Takagi, S., and Nagasawa, M.

Abstract

Diapycnal mixing caused through breaking of large-amplitude internal lee waves generated by sub-inertial diurnal tides, which are modulated with a 18.6-year period, is hypothesized to be fundamental to both the intermediate-layer ventilation and the bi-decadal oscillation around the North Pacific Ocean. The first observational evidence of such wave breaking is presented here. The breaking wave observed had ∼200 m height and ∼1 km width, and its associated diapycnal mixing was estimated to be ∼1.5 m2 s^[-1], with a temporal average ∼10^[4] times larger than typical values in the open oceans. Our estimate suggests that a similar mixing process occurs globally, particularly around the Pacific and Antarctic Oceans.

Published
2010

10. A science plan for regional arctic system modeling a report by the arctic research community for the National Science Foundation, Office of Polar Programs

Author

Roberts, A., Cassano, J., Döscher, R., Hinzman, L., Holland, M., Mitsudera, H., Sumi, A., Walsh, J. E., Alessa, L., Alexeev, V., Arendt, A., Altaweel, M., Bhatt, U., Cherry, J., Deal, C., Elliot, S., Follows, M., Hock, R., Kliskey, A., Lantuit, Hugues, Lawrence, D., Maslowski, W., McGuire, A. D., Overduin, Pier Paul, Overeem, I., Proshutinsky, A., Romanovsky, V., Sushama, L., Truffer, M., Roberts, A., Cassano, J., Döscher, R., Hinzman, L., Holland, M., Mitsudera, H., Sumi, A., Walsh, J. E., Alessa, L., Alexeev, V., Arendt, A., Altaweel, M., Bhatt, U., Cherry, J., Deal, C., Elliot, S., Follows, M., Hock, R., Kliskey, A., Lantuit, Hugues, Lawrence, D., Maslowski, W., McGuire, A. D., Overduin, Pier Paul, Overeem, I., Proshutinsky, A., Romanovsky, V., Sushama, L., and Truffer, M.

Published
2010

11. A Science Plan for Regional Arctic System Modeling, A report to the National Science Foundation from the International Arctic Science Community.

Author

Roberts, A., Cassano, J., Döscher, R., Hinzman, L., Holland, M., Mitsudera, H., Sumi, A., Walsh, J. E., Alessa, L., Alexeev, V., Arendt, A., Altaweel, M., Bhatt, U., Cherry, J., Deal, C., Elliot, S., Follows, M., Hock, R., Kliskey, A., Lantuit, Hugues, Lawrence, D., Maslowski, W., McGuire, A. D., Overduin, Pier Paul, Overeem, I., Proshutinsky, A., Romanovsky, V., Sushama, L., Truffer, M., Roberts, A., Cassano, J., Döscher, R., Hinzman, L., Holland, M., Mitsudera, H., Sumi, A., Walsh, J. E., Alessa, L., Alexeev, V., Arendt, A., Altaweel, M., Bhatt, U., Cherry, J., Deal, C., Elliot, S., Follows, M., Hock, R., Kliskey, A., Lantuit, Hugues, Lawrence, D., Maslowski, W., McGuire, A. D., Overduin, Pier Paul, Overeem, I., Proshutinsky, A., Romanovsky, V., Sushama, L., and Truffer, M.

Published
2010

21. Process Development of 4-[N-Methyl-N-(tetrahydropyran-4-yl)aminomethyl]aniline Dihydrochloride:  A Key Intermediate for TAK-779, a Small-Molecule Nonpeptide CCR5 Antagonist

Author

Hashimoto, H., Ikemoto, T., Itoh, T., Maruyama, H., Hanaoka, T., Wakimasu, M., Mitsudera, H., and Tomimatsu, K.

Abstract

A new and efficient synthesis of 4-[N-methyl-N-(tetrahydropyran-4-yl)aminomethyl]aniline dihydrochloride, a key intermediate for the CCR5 antagonist TAK-779, is described. Reductive alkylation of methylamine with tetrahydro-4H-pyran-4-one followed by alkylation of N-methyl-N-(tetrahydropyran-4-yl)amine with 4-nitrobenzylbromide and reduction of N-(4-nitrobenzyl)-N-(tetrahydropyran-4-yl)amine results in a 78% isolated yield from the starting materials by a scalable method, using only commercially available reagents.

Published
2002

22. Development of a New Synthetic Route of a Non-Peptide CCR5 Antagonist, TAK-779, for Large-Scale Preparation

Author

Ikemoto, T., Ito, T., Hashimoto, H., Kawarasaki, T., Nishiguchi, A., Mitsudera, H., Wakimasu, M., and Tomimatsu, K.

Abstract

A new large-scalable preparation of TAK-779 (1), a non-peptide CCR5 antagonist, has been developed. The route selection was focused on in the process research. The selective reduction of commercially available benzonitrile derivative (4) as the starting material with sodium bis(2-methoxyethoxy)aluminum hydride followed by the Wittig reaction, hydrogenation, and intramolecular acylation gave benzocycloheptanone (7) in good yield. The conversion of α,β-unsaturated carboxylic acid (8) led from 7 to benzyl alcohol (9) and shortened the number of steps using non-protected 4-aminobenzyl alcohol. The reductive alkylation of Me2NH and tetrahydro-4H-pyran-4-one (12) smoothly gave a tertiary amine (3). The coupling of 2 chlorinated 9, and 3 successfully led to an ammonium chloride (1). A new inexpensive preparation which did not require a chromatographic method was achieved.

Published
2000

27. Tidally modified western boundary current drives interbasin exchange between the Sea of Okhotsk and the North Pacific.

Author

Shu HW, Mitsudera H, Yamazaki K, Nakamura T, Kawasaki T, Nakanowatari T, Nishikawa H, and Sasaki H

Abstract

The interbasin exchange between the Sea of Okhotsk and the North Pacific governs the intermediate water ventilation and fertilization of the nutrient-rich subpolar Pacific, and thus has an enormous influence on the North Pacific. However, the mechanism of this exchange is puzzling; current studies have not explained how the western boundary current (WBC) of the subarctic North Pacific intrudes only partially into the Sea of Okhotsk. High-resolution models often exhibit unrealistically small exchanges, as the WBC overshoots passing by deep straits and does not induce exchange flows. Therefore, partial intrusion cannot be solely explained by large-scale, wind-driven circulation. Here, we demonstrate that tidal forcing is the missing mechanism that drives the exchange by steering the WBC pathway. Upstream of the deep straits, tidally-generated topographically trapped waves over a bank lead to cross-slope upwelling. This upwelling enhances bottom pressure, thereby steering the WBC pathway toward the deep straits. The upwelling is identified as the source of joint-effect-of-baroclinicity-and-relief (JEBAR) in the potential vorticity equation, which is caused by tidal oscillation instead of tidally-enhanced vertical mixing. The WBC then hits the island chain and induces exchange flows. This tidal control of WBC pathways is applicable on subpolar and polar regions globally.

Published
2021
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