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Libe Washburn - One of the best experts on this subject based on the ideXlab platform.

  • The island-scale internal wave climate of Moorea, French Polynesia
    Journal of Geophysical Research: Oceans, 2012
    Co-Authors: James J. Leichter, James L. Hench, Jan Witting, M. Dale Stokes, Libe Washburn
    Abstract:

    Analysis of five-year records of Temperatures and currents collected at Moorea reveal strong internal wave activity at predominantly semi-Diurnal frequencies impacting reef slopes at depths 30m around the entire island. Temperature changes of 1.5C to 3C are accompanied by surges of upward and onshore flow and vertical shear in onshore currents. Superimposed on annual Temperature changes of approximately 3C, internal wave activity is high from Oct-May and markedly lower from Jun-Sep. The offshore pycnocline is broadly distributed with continuous stratification to at least 500m depth, and a subsurface fluorescence maximum above the strong nutricline at approximately 200m. Minimum buoyancy periods range from 4.8 to 6min, with the maximum density gradient occurring at 50 to 60m depth in summer and deepening to approximately 150 to 200m in winter. The bottom slope angle around all of Moorea is super-critical relative to the vertical stratification angle suggesting that energy propagating into shallow water is only a portion of total incident internal wave energy. Vertical gradient Richardson numbers indicate dominance by density stability relative to current shear with relatively limited diapycnal mixing. Coherence and lagged cross-correlation of semi-Diurnal Temperature Variation indicate complex patterns of inter-site arrival of internal waves and no clear coherence or lagged correlation relationships among island sides. Semi-Diurnal and high frequency internal wave packets likely arrive on Moorea from a combination of local and distant sources and may have important impacts for nutrient and particle fluxes in deep reef environments. © 2012 American Geophysical Union. All Rights Reserved

  • the island scale internal wave climate of moorea french polynesia
    Journal of Geophysical Research, 2012
    Co-Authors: James J. Leichter, James L. Hench, Jan Witting, Dale M Stokes, Libe Washburn
    Abstract:

    [1] Analysis of five-year records of Temperatures and currents collected at Moorea reveal strong internal wave activity at predominantly semi-Diurnal frequencies impacting reef slopes at depths ≥30 m around the entire island. Temperature changes of 1.5°C to 3°C are accompanied by surges of upward and onshore flow and vertical shear in onshore currents. Superimposed on annual Temperature changes of approximately 3°C, internal wave activity is high from Oct–May and markedly lower from Jun–Sep. The offshore pycnocline is broadly distributed with continuous stratification to at least 500 m depth, and a subsurface fluorescence maximum above the strong nutricline at approximately 200 m. Minimum buoyancy periods range from 4.8 to 6 min, with the maximum density gradient occurring at 50 to 60 m depth in summer and deepening to approximately 150 to 200 m in winter. The bottom slope angle around all of Moorea is super-critical relative to the vertical stratification angle suggesting that energy propagating into shallow water is only a portion of total incident internal wave energy. Vertical gradient Richardson numbers indicate dominance by density stability relative to current shear with relatively limited diapycnal mixing. Coherence and lagged cross-correlation of semi-Diurnal Temperature Variation indicate complex patterns of inter-site arrival of internal waves and no clear coherence or lagged correlation relationships among island sides. Semi-Diurnal and high frequency internal wave packets likely arrive on Moorea from a combination of local and distant sources and may have important impacts for nutrient and particle fluxes in deep reef environments.

  • The island‐scale internal wave climate of Moorea, French Polynesia
    Journal of Geophysical Research, 2012
    Co-Authors: James J. Leichter, James L. Hench, Jan Witting, M. Dale Stokes, Libe Washburn
    Abstract:

    [1] Analysis of five-year records of Temperatures and currents collected at Moorea reveal strong internal wave activity at predominantly semi-Diurnal frequencies impacting reef slopes at depths ≥30 m around the entire island. Temperature changes of 1.5°C to 3°C are accompanied by surges of upward and onshore flow and vertical shear in onshore currents. Superimposed on annual Temperature changes of approximately 3°C, internal wave activity is high from Oct–May and markedly lower from Jun–Sep. The offshore pycnocline is broadly distributed with continuous stratification to at least 500 m depth, and a subsurface fluorescence maximum above the strong nutricline at approximately 200 m. Minimum buoyancy periods range from 4.8 to 6 min, with the maximum density gradient occurring at 50 to 60 m depth in summer and deepening to approximately 150 to 200 m in winter. The bottom slope angle around all of Moorea is super-critical relative to the vertical stratification angle suggesting that energy propagating into shallow water is only a portion of total incident internal wave energy. Vertical gradient Richardson numbers indicate dominance by density stability relative to current shear with relatively limited diapycnal mixing. Coherence and lagged cross-correlation of semi-Diurnal Temperature Variation indicate complex patterns of inter-site arrival of internal waves and no clear coherence or lagged correlation relationships among island sides. Semi-Diurnal and high frequency internal wave packets likely arrive on Moorea from a combination of local and distant sources and may have important impacts for nutrient and particle fluxes in deep reef environments.

Seong Chu Lim - One of the best experts on this subject based on the ideXlab platform.

  • Torsional Actuator Powered by Environmental Energy Harvesting from Diurnal Temperature Variation
    ACS Sustainable Chemistry and Engineering, 2016
    Co-Authors: Dong Seok Suh, T.k. Truong, Seong Chu Lim
    Abstract:

    Inspired by phase-change technology storing thermal energy in the form of latent heat, direct conversion of environmental Temperature Variation into a useful form of mechanical work is achieved using the drastic volume change of a phase-change material during solid-liquid phase transformation. A twisted carbon nanotube yarn in combination with a phase-change material functions as a backbone of torsional actuator, powered by the change of environmental Temperature, because nanopores among carbon nanotubes or their bundles are completely filled with the phase-change material. By the proper selection of infiltrated material whose melting Temperature lies within a Diurnal Temperature range, this hybrid yarn can be applied in an autonomous system using naturally abundant low-grade thermal energy flow.

James J. Leichter - One of the best experts on this subject based on the ideXlab platform.

  • The island-scale internal wave climate of Moorea, French Polynesia
    Journal of Geophysical Research: Oceans, 2012
    Co-Authors: James J. Leichter, James L. Hench, Jan Witting, M. Dale Stokes, Libe Washburn
    Abstract:

    Analysis of five-year records of Temperatures and currents collected at Moorea reveal strong internal wave activity at predominantly semi-Diurnal frequencies impacting reef slopes at depths 30m around the entire island. Temperature changes of 1.5C to 3C are accompanied by surges of upward and onshore flow and vertical shear in onshore currents. Superimposed on annual Temperature changes of approximately 3C, internal wave activity is high from Oct-May and markedly lower from Jun-Sep. The offshore pycnocline is broadly distributed with continuous stratification to at least 500m depth, and a subsurface fluorescence maximum above the strong nutricline at approximately 200m. Minimum buoyancy periods range from 4.8 to 6min, with the maximum density gradient occurring at 50 to 60m depth in summer and deepening to approximately 150 to 200m in winter. The bottom slope angle around all of Moorea is super-critical relative to the vertical stratification angle suggesting that energy propagating into shallow water is only a portion of total incident internal wave energy. Vertical gradient Richardson numbers indicate dominance by density stability relative to current shear with relatively limited diapycnal mixing. Coherence and lagged cross-correlation of semi-Diurnal Temperature Variation indicate complex patterns of inter-site arrival of internal waves and no clear coherence or lagged correlation relationships among island sides. Semi-Diurnal and high frequency internal wave packets likely arrive on Moorea from a combination of local and distant sources and may have important impacts for nutrient and particle fluxes in deep reef environments. © 2012 American Geophysical Union. All Rights Reserved

  • the island scale internal wave climate of moorea french polynesia
    Journal of Geophysical Research, 2012
    Co-Authors: James J. Leichter, James L. Hench, Jan Witting, Dale M Stokes, Libe Washburn
    Abstract:

    [1] Analysis of five-year records of Temperatures and currents collected at Moorea reveal strong internal wave activity at predominantly semi-Diurnal frequencies impacting reef slopes at depths ≥30 m around the entire island. Temperature changes of 1.5°C to 3°C are accompanied by surges of upward and onshore flow and vertical shear in onshore currents. Superimposed on annual Temperature changes of approximately 3°C, internal wave activity is high from Oct–May and markedly lower from Jun–Sep. The offshore pycnocline is broadly distributed with continuous stratification to at least 500 m depth, and a subsurface fluorescence maximum above the strong nutricline at approximately 200 m. Minimum buoyancy periods range from 4.8 to 6 min, with the maximum density gradient occurring at 50 to 60 m depth in summer and deepening to approximately 150 to 200 m in winter. The bottom slope angle around all of Moorea is super-critical relative to the vertical stratification angle suggesting that energy propagating into shallow water is only a portion of total incident internal wave energy. Vertical gradient Richardson numbers indicate dominance by density stability relative to current shear with relatively limited diapycnal mixing. Coherence and lagged cross-correlation of semi-Diurnal Temperature Variation indicate complex patterns of inter-site arrival of internal waves and no clear coherence or lagged correlation relationships among island sides. Semi-Diurnal and high frequency internal wave packets likely arrive on Moorea from a combination of local and distant sources and may have important impacts for nutrient and particle fluxes in deep reef environments.

  • The island‐scale internal wave climate of Moorea, French Polynesia
    Journal of Geophysical Research, 2012
    Co-Authors: James J. Leichter, James L. Hench, Jan Witting, M. Dale Stokes, Libe Washburn
    Abstract:

    [1] Analysis of five-year records of Temperatures and currents collected at Moorea reveal strong internal wave activity at predominantly semi-Diurnal frequencies impacting reef slopes at depths ≥30 m around the entire island. Temperature changes of 1.5°C to 3°C are accompanied by surges of upward and onshore flow and vertical shear in onshore currents. Superimposed on annual Temperature changes of approximately 3°C, internal wave activity is high from Oct–May and markedly lower from Jun–Sep. The offshore pycnocline is broadly distributed with continuous stratification to at least 500 m depth, and a subsurface fluorescence maximum above the strong nutricline at approximately 200 m. Minimum buoyancy periods range from 4.8 to 6 min, with the maximum density gradient occurring at 50 to 60 m depth in summer and deepening to approximately 150 to 200 m in winter. The bottom slope angle around all of Moorea is super-critical relative to the vertical stratification angle suggesting that energy propagating into shallow water is only a portion of total incident internal wave energy. Vertical gradient Richardson numbers indicate dominance by density stability relative to current shear with relatively limited diapycnal mixing. Coherence and lagged cross-correlation of semi-Diurnal Temperature Variation indicate complex patterns of inter-site arrival of internal waves and no clear coherence or lagged correlation relationships among island sides. Semi-Diurnal and high frequency internal wave packets likely arrive on Moorea from a combination of local and distant sources and may have important impacts for nutrient and particle fluxes in deep reef environments.

Peter Millard - One of the best experts on this subject based on the ideXlab platform.

  • Temperature sensitivity of decomposition decreases with increasing soil organic matter stability
    Science of the Total Environment, 2020
    Co-Authors: Gabriel Y. K. Moinet, Matthias Moinet, John E. Hunt, Cornelia Rumpel, Abad Chabbi, Peter Millard
    Abstract:

    Evaluation of the Temperature sensitivity of soil organic matter (SOM) decomposition is critical for forecasting whether soils in a warming world will lose or gain carbon and, therefore, accelerate or mitigate climate warming. It is usually described, using Arrhenius kinetics, as increasing with the stability of the substrate in laboratory conditions, where substrate availability is non-limiting and where chemical recalcitrance, therefore, predominantly regulates stability. However, conditions of non-limiting subtrate availability are rare in the undisturbed soil, where physicochemical protection of substrates may control their stability. The aim of this study was to assess the Temperature sensitivity of decomposition of SOM with contrasting stability in the field. Our conceptual approach was based on in situ measurements of soil CO2 efflux at a range of Temperatures from root exclusion plots of increasing age (1 month and three decades) and, therefore, with SOM of increasing stability. From a set of short-term measurements in spring, using Diurnal Temperature Variation, the relative Temperature sensitivity of SOM decomposition decreased significantly (p < 0.0001) with increasing SOM stability, and was weak (Q(10) < 1.3) in long-term root exclusion plots. This result was confirmed in a similar set of short-term measurements repeated later in the year, in summer, as well as from an analysis perfomed at the seasonal timscale. We provide direct field evidence that the Temperature sensitivity of SOM decomposition decreases with increasing stability, in direct contrast with Arrhenius kinetics prediction, and therefore show that stability of SOM in the field cannot be the sole result of chemical recalcitrance. We conclude that the physicochemical protection of SOM, which controls SOM stability in the field, constrains the Temperature sensitivity of SOM decomposition under field conditions. (C) 2019 The Author(s).

Subhasis Ghoshal - One of the best experts on this subject based on the ideXlab platform.

  • Effects of Diurnal Temperature Variation on microbial community and petroleum hydrocarbon biodegradation in contaminated soils from a sub-Arctic site.
    Environmental microbiology, 2015
    Co-Authors: Ali Akbari, Subhasis Ghoshal
    Abstract:

    Summary Contaminated soils are subject to Diurnal and seasonal Temperature Variations during on-site ex-situ bioremediation processes. We assessed how Diurnal Temperature Variations similar to that in summer at the site from which petroleum hydrocarbon-contaminated soil was collected affect the soil microbial community and the extent of biodegradation of petroleum hydrocarbons compared with constant Temperature regimes. Microbial community analyses for 16S rRNA and alkB genes by pyrosequencing indicated that the microbial community for soils incubated under Diurnal Temperature Variation from 5°C to 15°C (VART5-15) evolved similarly to that for soils incubated at constant Temperature of 15°C (CST15). In contrast, under a constant Temperature of 5°C (CST5), the community evolved significantly different. The extent of biodegradation of C10–C16 hydrocarbons in the VART5-15 systems was 48%, comparable with the 41% biodegradation in CST15 systems, but significantly higher than CST5 systems at 11%. The enrichment of Gammaproteobacteria was observed in the alkB gene-harbouring communities in VART5-15 and CST15 but not in CST5 systems. However, the Actinobacteria was abundant at all Temperature regimes. The results suggest that changes in microbial community composition as a result of Diurnal Temperature Variations can significantly influence petroleum hydrocarbon bioremediation performance in cold regions.