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Study on Nonlinear Transport Properties in Ca2RuO4 Epitaxial Thin Films Induced by the Quantum Phase Transitions [an abstract of dissertation and a summary of dissertation review]
No full textDissolved iron concentrations in various rivers in Hokkaido, Japan.
Get PDF海洋表層において植物プランクトンの光合成に利用される溶存鉄の供給源は多様であるが，その一部は河川から流入する．本研究は，北海道の河川を対象に，異なる土地被覆・土地利用状況にある流域において，時間・空間的に河川水中の溶存鉄濃度がどのように変化するかを多地点における季節を通じた採水・分析によって明らかにした．その結果，湿原を有する流域で溶存鉄濃度が高く，森林を主体とした流域では濃度が低いことが判明した．一方，農地を起源とする溶存鉄も存在する可能性があることがわかった．季節的には，夏期に溶存鉄濃度が上昇するという先行研究の成果を追認した．The dissolved iron utilized in photosynthesis by phytoplankton in the surface layer of the ocean includes various sources, but a certain amount of the dissolved iron is supplied from rivers. In this study, focusing on rivers in Hokkaido, we elucidated how the dissolved iron concentration in river water changes over time and space in different land cover and land use conditions in the watershed. This was achieved through seasonal sampling and analysis at multiple locations. The results revealed that areas with wetlands in low-lying watersheds had higher dissolved iron concentrations, while watersheds dominated by mountain forests showed lower concentrations. On the other hand, it was found that dissolved iron of agricultural origin might also be present. Seasonally, the study confirmed previous research findings that dissolved iron concentrations increase during the summer
Study on the biogeochemical cycles in the Pan-Okhotsk region
Get PDF環オホーツク観測研究センターでは，発足後の20年間に，北太平洋およびオホーツク海やベーリング海を含む環オホーツク海域を対象とした海洋循環・物質循環の研究を精力的に進めてきた．この海域を理解するにはデータの空白域であるロシアの排他的経済水域の観測が不可欠であり，同センターではロシア極東海洋気象学研究所との共同研究を積極的に推進してきた．結果，この海域の海洋循環・物質循環の知見は飛躍的に進み，北太平洋亜寒帯域における微量元素である鉄(Fe)を中心とした栄養物質供給プロセスと生物生産を生み出す仕組みについて鍵となる知見を明らかにしてきた．本稿では，環オホーツク観測研究センター発足後の20年間で進められてきた環オホーツク海域における海洋循環・物質循環研究を概観する．Over the past 20 years, the Pan-Okhotsk Research Center has actively studied ocean circulation and material circulation in the North Pacific and its marginal seas, including the Sea of Okhotsk and the Bering Sea. Observation of the Russian EEZ area was essential to understanding this area, the Pan-Okhotsk Research Center had actively promoted joint research expeditions with the Far Eastern Hydrometeorological Research Institute, Russia. During this period, our knowledge of ocean circulation and biogeochemistry in the Pan-Okhotsk region has advanced dramatically, and we have clarified key findings regarding nutrient and iron supply processes that fuel biological production in the North Pacific. This paper provides an overview of the study which conducted over the past 20 years
Turbulent mixing and heat/salt balance in the ice-ocean boundary layer
Get PDF本研究は，海氷-海洋境界層における乱流による熱塩輸送と海氷の成長・融解について，北極海中央海盆域で現地調査を実施した．この観測では，海氷とともに砕氷船を漂流させながら海氷直下の観測を継続的に行い，海氷運動による境界層内の水温，塩分の時空間構造，および，乱流混合に関する知見を得た．多層式流向流速計を用いた調査では，水平流速が深さとともに時計回りに回転するエクマン螺旋の構造を捉えた．乱流エネルギー（TKE）の生成項を計算し，乱流計により得られたTKEの散逸率と比較すると，TKEの生成項と散逸項が混合層上部で均衡する結果を得た．一方，混合層下部ではTKEの散逸項が生産項を大きく上回っており，海氷の慣性振動による海洋上層での内部重力波の発生が要因として考えられる．We conducted on-site investigations in the central Arctic Ocean about turbulent mixing and heat and salt transport in the sea ice-ocean boundary layer, related to the growth and melting of sea ice. During these observations, continuous measurements were performed beneath the sea ice while drifting with the icebreaker, RV Polarstern, providing insights into the spatiotemporal structure of water temperature, salinity, and turbulent mixing in the boundary layer associated with the periodic sea ice drift. Using an acoustic Doppler current profiler, the survey clearly captured the Ekman spiral in horizontal currents which rotate clockwise with the depth. The direct measurement of microscale current shear was conducted to estimate the production and dissipation terms of turbulent kinetic energy in the mixed layer. In its upper part, the two terms were well balanced. Meanwhile, in the lower part, the dissipation term significantly exceeded the production term, attributing to the near-inertial internal waves generated by the inertial oscillations of sea ice
