Статті в журналах: "Oceanic mixing"

1

Legg, Sonya. "Mixing by Oceanic Lee Waves." Annual Review of Fluid Mechanics 53, no. 1 (January 5, 2021): 173–201. http://dx.doi.org/10.1146/annurev-fluid-051220-043904.

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Oceanic lee waves are generated in the deep stratified ocean by the flow of ocean currents over sea floor topography, and when they break, they can lead to mixing in the stably stratified ocean interior. While the theory of linear lee waves is well established, the nonlinear mechanisms leading to mixing are still under investigation. Tidally driven lee waves have long been observed in the ocean, along with associated mixing, but observations of lee waves forced by geostrophic eddies are relatively sparse and largely indirect. Parameterizations of the mixing due to ocean lee waves are now being developed and implemented in ocean climate models. This review summarizes current theory and observations of lee wave generation and mixing driven by lee wave breaking, distinguishing between steady and tidally oscillating forcing. The existing parameterizations of lee wave–driven mixing informed by theory and observations are outlined, and the impacts of the parameterized lee wave–driven mixing on simulations of large-scale ocean circulation are summarized.

2

McWilliams, James C. "Oceanic Frontogenesis." Annual Review of Marine Science 13, no. 1 (January 3, 2021): 227–53. http://dx.doi.org/10.1146/annurev-marine-032320-120725.

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Frontogenesis is the fluid-dynamical processes that rapidly sharpen horizontal density gradients and their associated horizontal velocity shears. It is a positive feedback process where the ageostrophic, overturning secondary circulation in the cross-front plane accelerates the frontal sharpening until an arrest occurs through frontal instability and other forms of turbulent mixing. Several well-known types of oceanic frontal phenomena are surveyed, their impacts on oceanic system functioning are assessed, and future research is envisioned.

3

Zhu, Yuchao, Rong-Hua Zhang, and Jichang Sun. "North Pacific Upper-Ocean Cold Temperature Biases in CMIP6 Simulations and the Role of Regional Vertical Mixing." Journal of Climate 33, no. 17 (September 1, 2020): 7523–38. http://dx.doi.org/10.1175/jcli-d-19-0654.1.

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AbstractSubstantial model biases are still prominent even in the latest CMIP6 simulations; attributing their causes is defined as one of the three main scientific questions addressed in CMIP6. In this paper, cold temperature biases in the North Pacific subtropics are investigated using simulations from the newly released CMIP6 models, together with other related modeling products. In addition, ocean-only sensitivity experiments are performed to characterize the biases, with a focus on the role of oceanic vertical mixing schemes. Based on the Argo-derived diffusivity, idealized vertical diffusivity fields are designed to mimic the seasonality of vertical mixing in this region, and are employed in ocean-only simulations to test the sensitivity of this cold bias to oceanic vertical mixing. It is demonstrated that the cold temperature biases can be reduced when the mixing strength is enhanced within and beneath the surface boundary layer. Additionally, the temperature simulations are rather sensitive to the parameterization of static instability, and the cold biases can be reduced when the vertical diffusivity for convection is increased. These indicate that the cold temperature biases in the North Pacific can be largely attributed to biases in oceanic vertical mixing within ocean-only simulations, which likely contribute to the even larger biases seen in coupled simulations. This study therefore highlights the need for improved oceanic vertical mixing in order to reduce these persistent cold temperature biases seen across several CMIP models.

4

Whalen, Caitlin. "Measuring ocean mixing: From observing processes to quantifying impacts." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A151. http://dx.doi.org/10.1121/10.0015854.

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The impacts of ocean mixing are varied, ranging from the local across-isopycnal transport of heat, salt, and nutrients, to the global overturning circulation with implications for climate. A full understanding of turbulent mixing, from driving processes to impacts, spans all oceanic time and length scales. Turbulent mixing in the ocean occur on scales less than centimeters and timescales less than hours, yet the processes that drive this turbulence occurs on meters to 100s of km length scales and the impact of the turbulent mixing spans the full range of oceanic spatiotemporal scales. Here, we will discuss current approaches to measuring ocean mixing and explore how to bridge this scale gap to link the turbulence measurements to the processes that drive ocean mixing and the subsequent impacts. Intriguing examples of ocean mixing processes and their influence on ocean dynamics will be discussed throughout.

5

Huang, Rui Xin. "Mixing and Energetics of the Oceanic Thermohaline Circulation*." Journal of Physical Oceanography 29, no. 4 (April 1999): 727–46. http://dx.doi.org/10.1175/1520-0485(1999)029<0727:maeoto>2.0.co;2.

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6

Grant, Alan L. M., and Stephen E. Belcher. "Wind-Driven Mixing below the Oceanic Mixed Layer." Journal of Physical Oceanography 41, no. 8 (August 1, 2011): 1556–75. http://dx.doi.org/10.1175/jpo-d-10-05020.1.

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Abstract This study describes the turbulent processes in the upper ocean boundary layer forced by a constant surface stress in the absence of the Coriolis force using large-eddy simulation. The boundary layer that develops has a two-layer structure, a well-mixed layer above a stratified shear layer. The depth of the mixed layer is approximately constant, whereas the depth of the shear layer increases with time. The turbulent momentum flux varies approximately linearly from the surface to the base of the shear layer. There is a maximum in the production of turbulence through shear at the base of the mixed layer. The magnitude of the shear production increases with time. The increase is mainly a result of the increase in the turbulent momentum flux at the base of the mixed layer due to the increase in the depth of the boundary layer. The length scale for the shear turbulence is the boundary layer depth. A simple scaling is proposed for the magnitude of the shear production that depends on the surface forcing and the average mixed layer current. The scaling can be interpreted in terms of the divergence of a mean kinetic energy flux. A simple bulk model of the boundary layer is developed to obtain equations describing the variation of the mixed layer and boundary layer depths with time. The model shows that the rate at which the boundary layer deepens does not depend on the stratification of the thermocline. The bulk model shows that the variation in the mixed layer depth is small as long as the surface buoyancy flux is small.

7

MONAHAN, ADAM HUGH. "CORRELATION EFFECTS IN A SIMPLE STOCHASTIC MODEL OF THE THERMOHALINE CIRCULATION." Stochastics and Dynamics 02, no. 03 (September 2002): 437–62. http://dx.doi.org/10.1142/s0219493702000510.

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A simple model of the thermohaline circulation of the World Ocean is considered, in which fluctuations in internal oceanic mixing and in freshwater forcing are represented by stochastic processes. The effects on the stationary probability density function of correlations between fluctuations in mixing and freshwater forcing, and of finite autocorrelation time in oceanic mixing, are determined using a mixture of analytical and numerical techniques. The quantitative behaviour of the system is found to depend on the strength and correlation character of the noise processes, quite sensitively so in some regions of parameter space. The results of this analysis suggest the importance of accurately modelling high-frequency variability in nonlinear models of the climate system.

8

Heesterman, Aart. "Restoring or maintaining the vertical mixing of oceanic waters." International Journal of Scientific and Research Publications (IJSRP) 11, no. 6 (June 28, 2021): 787–93. http://dx.doi.org/10.29322/ijsrp.11.06.2021.p114102.

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9

Hsu, S. A., Robert Fett, and Paul E. La Violette. "Variations in atmospheric mixing height across oceanic thermal fronts." Journal of Geophysical Research 90, no. C2 (1985): 3211. http://dx.doi.org/10.1029/jc090ic02p03211.

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10

Gibson, Carl H. "Fossil turbulence and intermittency in sampling oceanic mixing processes." Journal of Geophysical Research 92, no. C5 (1987): 5383. http://dx.doi.org/10.1029/jc092ic05p05383.

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11

Chacón-Rebollo, T., M. Gómez-Mármol, and S. Rubino. "Numerical investigation of algebraic oceanic turbulent mixing-layer models." Nonlinear Processes in Geophysics 20, no. 6 (November 6, 2013): 945–54. http://dx.doi.org/10.5194/npg-20-945-2013.

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Abstract. In this paper we investigate the finite-time and asymptotic behaviour of algebraic turbulent mixing-layer models by numerical simulation. We compare the performances given by three different settings of the eddy viscosity. We consider Richardson number-based vertical eddy viscosity models. Two of these are classical algebraic turbulence models usually used in numerical simulations of global oceanic circulation, i.e. the Pacanowski–Philander and the Gent models, while the other one is a more recent model (Bennis et al., 2010) proposed to prevent numerical instabilities generated by physically unstable configurations. The numerical schemes are based on the standard finite element method. We perform some numerical tests for relatively large deviations of realistic initial conditions provided by the Tropical Atmosphere Ocean (TAO) array. These initial conditions correspond to states close to mixing-layer profiles, measured on the Equatorial Pacific region called the West-Pacific Warm Pool. We conclude that mixing-layer profiles could be considered as kinds of "absorbing configurations" in finite time that asymptotically evolve to steady states under the application of negative surface energy fluxes.

12

Abarzhi, S. I., and K. R. Sreenivasan. "Turbulent mixing and beyond." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 368, no. 1916 (April 13, 2010): 1539–46. http://dx.doi.org/10.1098/rsta.2010.0021.

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Turbulence is a supermixer. Turbulent mixing has immense consequences for physical phenomena spanning astrophysical to atomistic scales under both high- and low-energy-density conditions. It influences thermonuclear fusion in inertial and magnetic confinement systems; governs dynamics of supernovae, accretion disks and explosions; dominates stellar convection, planetary interiors and mantle-lithosphere tectonics; affects premixed and non-premixed combustion; controls standard turbulent flows (wall-bounded and free—subsonic, supersonic as well as hypersonic); as well as atmospheric and oceanic phenomena (which themselves have important effects on climate). In most of these circumstances, the mixing phenomena are driven by non-equilibrium dynamics. While each article in this collection dwells on a specific problem, the purpose here is to seek a few unified themes amongst diverse phenomena.

13

MacKinnon, Jennifer A., Zhongxiang Zhao, Caitlin B. Whalen, Amy F. Waterhouse, David S. Trossman, Oliver M. Sun, Louis C. St. Laurent, et al. "Climate Process Team on Internal Wave–Driven Ocean Mixing." Bulletin of the American Meteorological Society 98, no. 11 (November 1, 2017): 2429–54. http://dx.doi.org/10.1175/bams-d-16-0030.1.

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Abstract Diapycnal mixing plays a primary role in the thermodynamic balance of the ocean and, consequently, in oceanic heat and carbon uptake and storage. Though observed mixing rates are on average consistent with values required by inverse models, recent attention has focused on the dramatic spatial variability, spanning several orders of magnitude, of mixing rates in both the upper and deep ocean. Away from ocean boundaries, the spatiotemporal patterns of mixing are largely driven by the geography of generation, propagation, and dissipation of internal waves, which supply much of the power for turbulent mixing. Over the last 5 years and under the auspices of U.S. Climate Variability and Predictability Program (CLIVAR), a National Science Foundation (NSF)- and National Oceanic and Atmospheric Administration (NOAA)-supported Climate Process Team has been engaged in developing, implementing, and testing dynamics-based parameterizations for internal wave–driven turbulent mixing in global ocean models. The work has primarily focused on turbulence 1) near sites of internal tide generation, 2) in the upper ocean related to wind-generated near inertial motions, 3) due to internal lee waves generated by low-frequency mesoscale flows over topography, and 4) at ocean margins. Here, we review recent progress, describe the tools developed, and discuss future directions.

14

Fuhlbrügge, S., B. Quack, S. Tegtmeier, E. Atlas, H. Hepach, Q. Shi, S. Raimund, and K. Krüger. "The contribution of oceanic halocarbons to marine and free troposphere air over the tropical West Pacific." Atmospheric Chemistry and Physics Discussions 15, no. 13 (July 2, 2015): 17887–943. http://dx.doi.org/10.5194/acpd-15-17887-2015.

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Abstract. Emissions of halogenated very short lived substances (VSLS) from the tropical oceans contribute to the atmospheric halogen budget and affect tropospheric and stratospheric ozone. Here we investigate the contribution of natural oceanic VSLS emissions to the Marine Atmospheric Boundary Layer (MABL) and their transport into the Free Troposphere (FT) over the tropical West Pacific. The study concentrates in particular on ship and aircraft measurements of the VSLS bromoform, dibromomethane and methyl iodide and meteorological parameters during the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) campaign in the South China and Sulu Seas in November 2011. Elevated oceanic concentrations of 19.9 (2.80–136.91) pmol L−1 for bromoform, 5.0 (2.43–21.82) pmol L−1 for dibromomethane and 3.8 (0.55–18.83) pmol L−1 for methyl iodide in particular close to Singapore and at the coast of Borneo with high corresponding oceanic emissions of 1486 ± 1718 pmol m−2 h−1 for bromoform, 405 ± 349 pmol m−2 h−1 for dibromomethane and 433 ± 482 pmol m−2 h−1 for methyl iodide characterize this tropical region as a strong source of these compounds. Unexpectedly atmospheric mixing ratios in the MABL were relatively low with 2.08 ± 2.08 ppt for bromoform, 1.17 ± 1.17 ppt for dibromomethane and 0.39 ± 0.09 ppt for methyl iodide. We use meteorological and chemical ship and aircraft observations, FLEXPART trajectory calculations and source-loss estimates to identify the oceanic VSLS contribution to the MABL and to the FT. Our results show that a convective, well-ventilated MABL and intense convection led to the low atmospheric mixing ratios in the MABL despite the high oceanic emissions in coastal areas of the South-China and Sulu Seas. While the accumulated bromoform in the FT above the region origins almost entirely from the local South China Sea area, dibromomethane is largely advected from distant source regions. The accumulated FT mixing ratio of methyl iodide is higher than can be explained with the local oceanic or MABL contributions. Possible reasons, uncertainties and consequences of our observations and model estimates are discussed.

15

Mcphee, Miles G. "On the Turbulent Mixing Length in the Oceanic Boundary Layer." Journal of Physical Oceanography 24, no. 9 (September 1994): 2014–31. http://dx.doi.org/10.1175/1520-0485(1994)024<2014:ottmli>2.0.co;2.

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16

Odier, Philippe, Jun Chen, and Robert E. Ecke. "Entrainment and mixing in a laboratory model of oceanic overflow." Journal of Fluid Mechanics 746 (April 4, 2014): 498–535. http://dx.doi.org/10.1017/jfm.2014.104.

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AbstractWe present experimental measurements of a wall-bounded gravity current, motivated by characterizing natural gravity currents such as oceanic overflows. We use particle image velocimetry and planar laser-induced fluorescence to simultaneously measure the velocity and density fields as they evolve downstream of the initial injection from a turbulent channel flow onto a plane inclined at$10^\circ $with respect to horizontal. The turbulence level of the input flow is controlled by injecting velocity fluctuations upstream of the output nozzle. The initial Reynolds number based on the Taylor microscale of the flow,$R_{\lambda }$, is varied between 40 and 120, and the effects of the initial turbulence level are assessed. The bulk Richardson number$\mathit{Ri}$for the flow is${\sim }$0.3 whereas the gradient Richardson number$\mathit{Ri}_g$varies between 0.04 and 0.25, indicating that shear dominates the stabilizing effect of stratification. Kelvin–Helmholtz instability results in vigorous vertical transport of mass and momentum. We present baseline characterization of standard turbulence quantities and calculate, in several different ways, the fluid entrainment coefficient$E$, a quantity of considerable interest in mixing parameterization for ocean circulation models. We also determine the properties of mixing as represented by the flux Richardson number$\mathit{Ri}_f$as a function of$\mathit{Ri}_g$and diapycnal mixing parameter$K_{\rho }$versus the buoyancy Reynolds number$\mathit{Re}_b$. We find reasonable agreement with results from natural flows.

17

Nishioka, Jun, Takeshi Nakatsuka, Yutaka W. Watanabe, Ichiro Yasuda, Kenshi Kuma, Hiroshi Ogawa, Naoto Ebuchi, et al. "Intensive mixing along an island chain controls oceanic biogeochemical cycles." Global Biogeochemical Cycles 27, no. 3 (September 2013): 920–29. http://dx.doi.org/10.1002/gbc.20088.

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18

HOLLAND, DAVID M., RODOLFO R. ROSALES, DAN STEFANICA, and ESTEBAN G. TABAK. "Internal hydraulic jumps and mixing in two-layer flows." Journal of Fluid Mechanics 470 (October 31, 2002): 63–83. http://dx.doi.org/10.1017/s002211200200188x.

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Internal hydraulic jumps in two-layer flows are studied, with particular emphasis on their role in entrainment and mixing. For highly entraining internal jumps, a new closure is proposed for the jump conditions. The closure is based on two main assumptions: (i) most of the energy dissipated at the jump goes into turbulence, and (ii) the amount of turbulent energy that a stably stratified flow may contain without immediately mixing further is bounded by a measure of the stratification. As a consequence of this closure, surprising bounds emerge, for example on the amount of entrainment that may take place at the location of the jump. These bounds are probably almost achieved by highly entraining internal jumps, such as those likely to develop in dense oceanic over flows. The values obtained here are in good agreement with the existing observations of the spatial development of oceanic downslope currents, which play a crucial role in the formation of abyssal and intermediate waters in the global ocean.

19

Li, J., Z. Wang, G. Zhuang, G. Luo, Y. Sun, and Q. Wang. "Mixing of Asian mineral dust with anthropogenic pollutants and its impact on regional atmospheric environmental and oceanic biogeochemical cycles over East Asia: a model case study of a super-duststorm in March 2010." Atmospheric Chemistry and Physics Discussions 12, no. 1 (January 27, 2012): 2743–82. http://dx.doi.org/10.5194/acpd-12-2743-2012.

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Abstract. Mixing of Asian mineral dust with anthropogenic pollutants allows pollutants (e.g. sulfate and nitrate) to be transported over longer distances (e.g. to the northern Pacific, even to North America) along with dust particles. This mixing therefore affects the atmospheric and oceanic environment at local, regional and even continental scales. In this study, we used a three-dimensional regional chemical transport model (NAQPMS) to examine the degree of mixing between Asian mineral dust and anthropogenic pollutants in a super-duststorm event during 19–22 March 2010. Influences of the mixing processes on regional atmospheric environmental and oceanic biogeochemical cycles were also investigated. A comparison with measurements showed that the model reproduced well the trajectory of long-range dust transport, the vertical dust profile, and the chemical evolution of dust particles. We found that along-path mixing processes during the long-range transport of Asian dust led to increasingly polluted particles. As a result, ~60% of the sulfate and 70–95% of the nitrate in the downwind regions was derived from active mixing processes of minerals with pollutants sourced from the North China Plain and enhanced by transport over South China. This mixing had a significant impact on the regional-scale atmospheric composition and oceanic biogeochemical cycle. Surface HNO3, SO2 and O3 were decreased by up to 90%, 40% and 30%, respectively, due to the heterogeneous reactions on dust particles. Fe solubility rose from ~0.5% in the Gobi region to ~3–5% in the northwestern Pacific, resulting from oxidization of SO2 on dust particles. Total Fe(II) deposition in the ocean region of East Asia reached 327 tons during the 4-day dust event, and created a calculated primary productivity of ~520 mgC m−2 d−1 in the Kuril Islands, which can support almost 100% of the observed mean marine primary productivity in spring in this region (526 mgC m−2 d−1).

20

Li, J., Z. Wang, G. Zhuang, G. Luo, Y. Sun, and Q. Wang. "Mixing of Asian mineral dust with anthropogenic pollutants over East Asia: a model case study of a super-duststorm in March 2010." Atmospheric Chemistry and Physics 12, no. 16 (August 21, 2012): 7591–607. http://dx.doi.org/10.5194/acp-12-7591-2012.

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Abstract. Mixing of Asian mineral dust with anthropogenic pollutants allows pollutants (e.g. sulfate and nitrate) to be transported over longer distances (e.g. to the northern Pacific, even to North America) along with dust particles. This mixing therefore affects the atmospheric and oceanic environment at local, regional and even continental scales. In this study, we used a three-dimensional regional chemical transport model (Nested Air Quality Predicting Modeling System, NAQPMS) to examine the degree of mixing between Asian mineral dust and anthropogenic pollutants in a super-duststorm event during 19–22 March 2010. Influences of the mixing processes on regional atmospheric environmental and oceanic biogeochemical cycles were also investigated. A comparison with measurements showed that the model reproduced well the trajectory of long-range dust transport, the vertical dust profile, and the chemical evolution of dust particles. We found that along-path mixing processes during the long-range transport of Asian dust led to increasingly polluted particles. As a result, ~60% of the sulfate and 70–95% of the nitrate in the downwind regions was derived from active mixing processes of minerals with pollutants sourced from the North China Plain and enhanced by transport over South China. This mixing had a significant impact on the regional-scale atmospheric composition and oceanic biogeochemical cycle. Surface HNO3, SO2 and O3 were decreased by up to 90%, 40% and 30%, respectively, due to the heterogeneous reactions on dust particles. Fe solubility rose from ~0.5% in the Gobi region to ~3–5% in the northwestern Pacific, resulting from oxidization of SO2 on dust particles. Total Fe(II) deposition in the ocean region of East Asia reached 327 tons during the 4-day dust event, and created a calculated primary productivity of ~520 mgC m−2 d−1 in the Kuril Islands, which can support almost 100% of the observed mean marine primary productivity in spring in this region (526 mgC m−2 d−1).

21

Fu, Hongli, Jinkun Yang, Wei Li, Xinrong Wu, Guijun Han, Yuanfu Xie, Shaoqing Zhang, Xuefeng Zhang, Yingzhi Cao, and Xiaoshuang Zhang. "A Potential Density Gradient Dependent Analysis Scheme for Ocean Multiscale Data Assimilation." Advances in Meteorology 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/9315601.

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This study addresses how to maintain oceanic mixing along potential density surface in ocean data assimilation (ODA). It is well known that the oceanic mixing across the potential density surface is much weaker than that along the potential density surface. However, traditional ODA schemes allow the mixing across the potential density surface and thus may result in extra assimilation errors. Here, a new ODA scheme that uses potential density gradient information of the model background to rescale observational adjustment is designed to improve the quality of assimilation. The new scheme has been tested using a regional ocean model within a multiscale 3-dimensional variational framework. Results show that the new scheme effectively prevents the excessive unphysical projection of observational information in the direction across potential density surface and thus improves assimilation quality greatly. Forecast experiments also show that the new scheme significantly improves the model forecast skills through providing more dynamically consistent initial conditions

22

Kantha, Lakshmi, and Hubert Luce. "Mixing Coefficient in Stably Stratified Flows." Journal of Physical Oceanography 48, no. 11 (November 2018): 2649–65. http://dx.doi.org/10.1175/jpo-d-18-0139.1.

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AbstractTurbulent mixing in the interior of the oceans is not as well understood as mixing in the oceanic boundary layers. Mixing in the generally stably stratified interior is primarily, although not exclusively, due to intermittent shear instabilities. Part of the energy extracted by the Reynolds stresses acting on the mean shear is expended in increasing the potential energy of the fluid column through a buoyancy flux, while most of it is dissipated. The mixing coefficient χm, the ratio of the buoyancy flux to the dissipation rate of turbulence kinetic energy ε, is an important parameter, since knowledge of χm enables turbulent diffusivities to be inferred. Theory indicates that χm must be a function of the gradient Richardson number. Yet, oceanic studies suggest that a value of around 0.2 for χm gives turbulent diffusivities that are in good agreement with those inferred from tracer studies. Studies by scientists working with atmospheric radars tend to reinforce these findings but are seldom referenced in oceanographic literature. The goal of this paper is to bring together oceanographic, atmospheric, and laboratory observations related to χm and to report on the values deduced from in situ data collected in the lower troposphere by unmanned aerial vehicles, equipped with turbulence sensors and flown in the vicinity of the Middle and Upper Atmosphere (MU) radar in Japan. These observations are consistent with past studies in the oceans, in that a value of around 0.16 for χm yields good agreement between ε derived from turbulent temperature fluctuations using this value and ε obtained directly from turbulence velocity fluctuations.

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Mamberti, Marc, Henriette Lapierre, Delphine Bosch, Etienne Jaillard, Jean Hernandez, and Mireille Polvé. "The Early Cretaceous San Juan Plutonic Suite, Ecuador: a magma chamber in an oceanic plateau?" Canadian Journal of Earth Sciences 41, no. 10 (October 1, 2004): 1237–58. http://dx.doi.org/10.1139/e04-060.

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Sections through an oceanic plateau are preserved in tectonic slices in the Western Cordillera of Ecuador (South America). The San Juan section is a sequence of maficultramafic cumulates. To establish that these plutonic rocks formed in an oceanic plateau setting, we have developed criteria that discriminate intrusions of oceanic plateaus from those of other tectonic settings. The mineralogy and crystallization sequence of the cumulates are similar to those of intra-plate magmas. Clinopyroxene predominates throughout, and orthopyroxene is only a minor component. Rocks of intermediate composition are absent, and hornblende is restricted to the uppermost massive gabbros within the sequence. The ultramafic cumulates are very depleted in light rare-earth elements (LREE), whereas the gabbros have flat or slightly enriched LREE patterns. The composition of the basaltic liquid in equilibrium with the peridotite, calculated using olivine compositions and REE contents of clinopyroxene, contains between 16% and 8% MgO and has a flat REE pattern. This melt is geochemically similar to other accreted oceanic plateau basalts, isotropic gabbros, and differentiated sills in western Ecuador. The Ecuadorian intrusive and extrusive rocks have a narrow range of εNdi (+8 to +5) and have a rather large range of Pb isotopic ratios. Pb isotope systematics of the San Juan plutonic rocks and mineral separates lie along a mixing line between the depleted mantle (DMM) and the enriched-plume end members. This suggests that the Ecuadorian plutonic rocks generated from the mixing of two mantle sources, a depleted mid-oceanic ridge basalt (MORB) source and an enriched one. The latter is characterized by high (207Pb/204Pb)i ratios and could reflect a contamination by recycled either lower continental crust or oceanic pelagic sediments and (or) altered oceanic crust (enriched mantle type I, EMI). These data suggest that the San Juan sequence represents the plutonic components of an Early Cretaceous oceanic plateau, which accreted in the Late Cretaceous to the Ecuadorian margin.

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Williams, J. E., G. Le Bras, A. Kukui, H. Ziereis, and C. A. M. Brenninkmeijer. "The impact of the chemical production of methyl nitrate from the NO + CH3O2 reaction on the global distributions of alkyl nitrates, nitrogen oxides and tropospheric ozone: a global modeling study." Atmospheric Chemistry and Physics Discussions 13, no. 8 (August 2, 2013): 20111–63. http://dx.doi.org/10.5194/acpd-13-20111-2013.

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Abstract. The formation, abundance and distribution of organic nitrates are relevant for determining the production efficiency and resident mixing ratios of tropospheric ozone (O3) at both regional and global scales. Here we investigate the effect of applying the recently measured direct chemical production of methyl nitrate (CH3ONO2) during NOx recycling involving the methyl-peroxy radical on the global tropospheric distribution of CH3ONO2 and the perturbations introduced towards tropospheric NOx and O3 using the TM5 global chemistry transport model. By comparing against numerous observations we show that the global surface distribution of CH3ONO2 can be largely explained by introducing the chemical production mechanism using a branching ratio of 0.3%, when assuming a direct oceanic emission source of ~0.29 Tg N yr−1. The resident mixing ratios are found to be highly sensitive towards the dry deposition velocity of CH3ONO2 that is prescribed, where more than 50% of the direct oceanic emission of CH3ONO2 is lost near the source regions thereby mitigating subsequent effects on tropospheric composition due to long range and convective transport. For the higher alkyl nitrates (C2 and above) we find improvements in their simulated distribution in the tropics in TM5 improves when introducing direct oceanic emissions of ~0.17 Tg N yr−1. For the tropical upper troposphere (UT) a significant low model bias for all alkly nitrates occurs due to either missing transport pathways or chemical precursors, although measurements show significant variability in resident mixing ratios at high altitudes with respect to both latitude and longitude. For total reactive nitrogen (NOy) ~20% originates from alkyl nitrates in the tropical and extra-tropical UT, where the introduction of both direct oceanic emission sources and the chemical production of CH3ONO2 only increases NOy by ~5% when compared with aircraft observations. We find that the increases in tropospheric O3 due to direct oceanic emissions are mitigated by introducing the direct chemical production of CH3ONO2 resulting in rather moderate effects on nitrogen oxides and tropospheric O3.

25

Thomas, Jordan, Darryn Waugh, and Anand Gnanadesikan. "Relationship between Ocean Carbon and Heat Multidecadal Variability." Journal of Climate 31, no. 4 (February 2018): 1467–82. http://dx.doi.org/10.1175/jcli-d-17-0134.1.

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The global ocean serves as a critical sink for anthropogenic carbon and heat. While significant effort has been dedicated to quantifying the oceanic uptake of these quantities, less research has been conducted on the mechanisms underlying decadal-to-centennial variability in oceanic heat and carbon. Therefore, little is understood about how much such variability may have obscured or reinforced anthropogenic change. Here the relationship between oceanic heat and carbon content is examined in a suite of coupled climate model simulations that use different parameterization settings for mesoscale mixing. The differences in mesoscale mixing result in very different multidecadal variability, especially in the Weddell Sea where the characteristics of deep convection are drastically changed. Although the magnitude and frequency of variability in global heat and carbon content is different across the model simulations, there is a robust anticorrelation between global heat and carbon content in all simulations. Global carbon content variability is primarily driven by Southern Ocean carbon variability. This contrasts with global heat content variability. Global heat content is primarily driven by variability in the southern midlatitudes and tropics, which opposes the Southern Ocean variability.

26

Bennis, Anne-Claire, Tomas Chacón Rebollo, Macarena Gómez Mármol, and Roger Lewandowski. "Numerical modelling of algebraic closure models of oceanic turbulent mixing layers." ESAIM: Mathematical Modelling and Numerical Analysis 44, no. 6 (March 17, 2010): 1255–77. http://dx.doi.org/10.1051/m2an/2010025.

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27

Chacón Rebollo, T., M. Gómez Mármol, and S. Rubino. "Analysis of numerical stability of algebraic oceanic turbulent mixing layer models." Applied Mathematical Modelling 38, no. 24 (December 2014): 5836–57. http://dx.doi.org/10.1016/j.apm.2014.04.050.

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28

Gnanadesikan, Anand, Marie‐Aude Pradal, and Ryan Abernathey. "Isopycnal mixing by mesoscale eddies significantly impacts oceanic anthropogenic carbon uptake." Geophysical Research Letters 42, no. 11 (June 2, 2015): 4249–55. http://dx.doi.org/10.1002/2015gl064100.

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29

Brischoux, François, Cédric Cotté, Harvey B. Lillywhite, Frédéric Bailleul, Maxime Lalire, and Philippe Gaspar. "Oceanic circulation models help to predict global biogeography of pelagic yellow-bellied sea snake." Biology Letters 12, no. 8 (August 2016): 20160436. http://dx.doi.org/10.1098/rsbl.2016.0436.

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It is well recognized that most marine vertebrates, and especially tetrapods, precisely orient and actively move in apparently homogeneous oceanic environments. Here, we investigate the presumptive role of oceanic currents in biogeographic patterns observed in a secondarily marine tetrapod, the yellow-bellied sea snake ( Hydrophis [ Pelamis ] platurus ). State-of-the-art world ocean circulation models show how H. platurus , the only pelagic species of sea snake, can potentially exploit oceanic currents to disperse and maintain population mixing between localities that spread over two-thirds of the Earth's circumference. The very close association of these snakes with surface currents seems to provide a highly efficient dispersal mechanism that allowed this species to range extensively and relatively quickly well beyond the central Indo-Pacific area, the centre of origin, abundance and diversity of sea snakes. Our results further suggest that the pan-oceanic population of this species must be extraordinarily large.

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Löptien, Ulrike, and Heiner Dietze. "Reciprocal bias compensation and ensuing uncertainties in model-based climate projections: pelagic biogeochemistry versus ocean mixing." Biogeosciences 16, no. 9 (May 6, 2019): 1865–81. http://dx.doi.org/10.5194/bg-16-1865-2019.

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Abstract. Anthropogenic emissions of greenhouse gases such as CO2 and N2O impinge on the Earth system, which in turn modulates atmospheric greenhouse gas concentrations. The underlying feedback mechanisms are complex and, at times, counterintuitive. So-called Earth system models have recently matured to standard tools tailored to assess these feedback mechanisms in a warming world. Applications for these models range from being targeted at basic process understanding to the assessment of geo-engineering options. A problem endemic to all these applications is the need to estimate poorly known model parameters, specifically for the biogeochemical component, based on observational data (e.g., nutrient fields). In the present study, we illustrate with an Earth system model that through such an approach biases and other model deficiencies in the physical ocean circulation model component can reciprocally compensate for biases in the pelagic biogeochemical model component (and vice versa). We present two model configurations that share a remarkably similar steady state (based on ad hoc measures) when driven by historical boundary conditions, even though they feature substantially different configurations (parameter sets) of ocean mixing and biogeochemical cycling. When projected into the future the similarity between the model responses breaks. Metrics such as changes in total oceanic carbon content and suboxic volume diverge between the model configurations as the Earth warms. Our results reiterate that advancing the understanding of oceanic mixing processes will reduce the uncertainty of future projections of oceanic biogeochemical cycles. Related to the latter, we suggest that an advanced understanding of oceanic biogeochemical cycles can be used for advancements in ocean circulation modules.

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Pasquero, Claudia, and Eli Tziperman. "Statistical Parameterization of Heterogeneous Oceanic Convection." Journal of Physical Oceanography 37, no. 2 (February 1, 2007): 214–29. http://dx.doi.org/10.1175/jpo3008.1.

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Abstract A statistical convective adjustment scheme is proposed that attempts to account for the effects of mesoscale and submesoscale variability of temperature and salinity typically observed in the oceanic convective regions. Temperature and salinity in each model grid box are defined in terms of their mean, variance, and mutual correlations. Subgrid-scale instabilities lead to partial mixing between different layers in the water column. This allows for a smooth transition between the only two states (convection on and convection off) allowed in standard convective adjustment schemes. The advantage of the statistical parameterization is that possible instabilities associated with the sharp transition between the two states, which are known to occasionally affect the large-scale model solution, are eliminated. The procedure also predicts the generation of correlations between temperature and salinity and the presence of convectively induced upgradient fluxes that have been obtained in numerical simulations of heterogeneous convection and that cannot be represented by standard convective adjustment schemes.

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Prakash, Kumar Ravi, Tanuja Nigam, and Vimlesh Pant. "Estimation of oceanic subsurface mixing under a severe cyclonic storm using a coupled atmosphere–ocean–wave model." Ocean Science 14, no. 2 (April 3, 2018): 259–72. http://dx.doi.org/10.5194/os-14-259-2018.

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Abstract. A coupled atmosphere–ocean–wave model was used to examine mixing in the upper-oceanic layers under the influence of a very severe cyclonic storm Phailin over the Bay of Bengal (BoB) during 10–14 October 2013. The coupled model was found to improve the sea surface temperature over the uncoupled model. Model simulations highlight the prominent role of cyclone-induced near-inertial oscillations in subsurface mixing up to the thermocline depth. The inertial mixing introduced by the cyclone played a central role in the deepening of the thermocline and mixed layer depth by 40 and 15 m, respectively. For the first time over the BoB, a detailed analysis of inertial oscillation kinetic energy generation, propagation, and dissipation was carried out using an atmosphere–ocean–wave coupled model during a cyclone. A quantitative estimate of kinetic energy in the oceanic water column, its propagation, and its dissipation mechanisms were explained using the coupled atmosphere–ocean–wave model. The large shear generated by the inertial oscillations was found to overcome the stratification and initiate mixing at the base of the mixed layer. Greater mixing was found at the depths where the eddy kinetic diffusivity was large. The baroclinic current, holding a larger fraction of kinetic energy than the barotropic current, weakened rapidly after the passage of the cyclone. The shear induced by inertial oscillations was found to decrease rapidly with increasing depth below the thermocline. The dampening of the mixing process below the thermocline was explained through the enhanced dissipation rate of turbulent kinetic energy upon approaching the thermocline layer. The wave–current interaction and nonlinear wave–wave interaction were found to affect the process of downward mixing and cause the dissipation of inertial oscillations.

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Fuhlbrügge, Steffen, Birgit Quack, Susann Tegtmeier, Elliot Atlas, Helmke Hepach, Qiang Shi, Stefan Raimund, and Kirstin Krüger. "The contribution of oceanic halocarbons to marine and free tropospheric air over the tropical West Pacific." Atmospheric Chemistry and Physics 16, no. 12 (June 21, 2016): 7569–85. http://dx.doi.org/10.5194/acp-16-7569-2016.

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Abstract. Emissions of halogenated very-short-lived substances (VSLSs) from the oceans contribute to the atmospheric halogen budget and affect tropospheric and stratospheric ozone. Here, we investigate the contribution of natural oceanic VSLS emissions to the marine atmospheric boundary layer (MABL) and their transport into the free troposphere (FT) over the tropical West Pacific. The study concentrates on bromoform, dibromomethane and methyl iodide measured on ship and aircraft during the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) campaign in the South China and Sulu seas in November 2011. Elevated oceanic concentrations for bromoform, dibromomethane and methyl iodide of on average 19.9, 5.0 and 3.8 pmol L−1, in particular close to Singapore and to the coast of Borneo, with high corresponding oceanic emissions of 1486, 405 and 433 pmol m−2 h−1 respectively, characterise this tropical region as a strong source of these compounds. Atmospheric mixing ratios in the MABL were unexpectedly relatively low with 2.08, 1.17 and 0.39 ppt for bromoform, dibromomethane and methyl iodide. We use meteorological and chemical ship and aircraft observations, FLEXPART trajectory calculations and source-loss estimates to identify the oceanic VSLS contribution to the MABL and to the FT. Our results show that the well-ventilated MABL and intense convection led to the low atmospheric mixing ratios in the MABL despite the high oceanic emissions. Up to 45 % of the accumulated bromoform in the FT above the region originates from the local South China Sea area, while dibromomethane is largely advected from distant source regions and the local ocean only contributes 20 %. The accumulated methyl iodide in the FT is higher than can be explained with local contributions. Possible reasons, uncertainties and consequences of our observations and model estimates are discussed.

34

St. Laurent, Louis, and Harper Simmons. "Estimates of Power Consumed by Mixing in the Ocean Interior." Journal of Climate 19, no. 19 (October 1, 2006): 4877–90. http://dx.doi.org/10.1175/jcli3887.1.

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Abstract Much attention has focused on the power required for driving mixing processes in the ocean interior, the thermohaline circulation, and the related meridional overturning circulation (MOC). Recent estimates range from roughly 0.5 to 2 TW (1 TW = 1 × 1012 W), based on differing arguments for the closure of the MOC mass budget. While these values are both O(1) TW, the thermodynamic implications of the estimates are significantly different. In addition, these numbers represent an integral constraint on the global circulation, and the apparent discrepancy merits careful examination. Through basic thermodynamic considerations on water mass mixing, a mechanical power consumption of 3 ± 1 TW is found to be consistent with a basic knowledge of the distribution and magnitude of oceanic turbulence diffusivities. This estimate is somewhat independent of any specific model for mass closure of the MOC. In addition, this estimate is based on a thermocline diffusivity of only 0.1 cm2 s−1, with enhanced diffusivities acting only in the deep and bottom waters. Adding enhanced diffusivities in the upper ocean, or lowering the mixing efficiency below 20%, will increase the power estimate. Moreover, 3 TW is a reasonable estimate for the power availability to processes acting beneath the oceanic mixed layer.

35

Byrne, David, Lukas Papritz, Ivy Frenger, Matthias Münnich, and Nicolas Gruber. "Atmospheric Response to Mesoscale Sea Surface Temperature Anomalies: Assessment of Mechanisms and Coupling Strength in a High-Resolution Coupled Model over the South Atlantic*." Journal of the Atmospheric Sciences 72, no. 5 (May 1, 2015): 1872–90. http://dx.doi.org/10.1175/jas-d-14-0195.1.

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Abstract Many aspects of the coupling between the ocean and atmosphere at the mesoscale (on the order of 20–100 km) remain unknown. While recent observations from the Southern Ocean revealed that circular fronts associated with oceanic mesoscale eddies leave a distinct imprint on the overlying wind, cloud coverage, and rain, the mechanisms responsible for explaining these atmospheric changes are not well established. Here the atmospheric response above mesoscale ocean eddies is investigated utilizing a newly developed coupled atmosphere–ocean regional model [Consortium for Small-Scale Modeling–Regional Ocean Modelling System (COSMO-ROMS)] configured at a horizontal resolution of ~10 km for the South Atlantic and run for a 3-month period during austral winter of 2004. The model-simulated changes in surface wind, cloud fraction, and rain above the oceanic eddies are very consistent with the relationships inferred from satellite observations for the same region and time. From diagnosing the model’s momentum balance, it is shown that the atmospheric imprint of the oceanic eddies are driven by the modification of vertical mixing in the atmospheric boundary layer, rather than secondary flows driven by horizontal pressure gradients. This is largely due to the very limited ability of the atmosphere to adjust its temperature over the time scale it takes for an air parcel to pass over these mesoscale oceanic features. This results in locally enhanced vertical gradients between the ocean surface and the overlying air and thus a rapid change in turbulent mixing in the atmospheric boundary layer and an associated change in the vertical momentum flux.

36

Károly, György, Rudolf Dániel Prokaj, István Scheuring, and Tamás Tél. "Climate change in a conceptual atmosphere–phytoplankton model." Earth System Dynamics 11, no. 3 (July 16, 2020): 603–15. http://dx.doi.org/10.5194/esd-11-603-2020.

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Abstract. We develop a conceptual coupled atmosphere–phytoplankton model by combining the Lorenz'84 general circulation model and the logistic population growth model under the condition of a climate change due to a linear time dependence of the strength of anthropogenic atmospheric forcing. The following types of couplings are taken into account: (a) the temperature modifies the total biomass of phytoplankton via the carrying capacity; (b) the extraction of carbon dioxide by phytoplankton slows down the speed of climate change; (c) the strength of mixing/turbulence in the oceanic mixing layer is in correlation with phytoplankton productivity. We carry out an ensemble approach (in the spirit of the theory of snapshot attractors) and concentrate on the trends of the average phytoplankton concentration and average temperature contrast between the pole and Equator, forcing the atmospheric dynamics. The effect of turbulence is found to have the strongest influence on these trends. Our results show that when mixing has sufficiently strong coupling to production, mixing is able to force the typical phytoplankton concentration to always decay globally in time and the temperature contrast to decrease faster than what follows from direct anthropogenic influences. Simple relations found for the trends without this coupling do, however, remain valid; just the coefficients become dependent on the strength of coupling with oceanic mixing. In particular, the phytoplankton concentration and its coupling to climate are found to modify the trend of global warming and are able to make it stronger than what it would be without biomass.

37

Xu, Suqing, Keyhong Park, Yanmin Wang, Liqi Chen, Di Qi, and Bingrui Li. "Variations in the summer oceanic pCO2 and carbon sink in Prydz Bay using the self-organizing map analysis approach." Biogeosciences 16, no. 3 (February 13, 2019): 797–810. http://dx.doi.org/10.5194/bg-16-797-2019.

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Abstract. This study applies a neural network technique to produce maps of oceanic surface pCO2 in Prydz Bay in the Southern Ocean on a weekly 0.1∘ longitude × 0.1∘ latitude grid based on in situ measurements obtained during the 31st CHINARE cruise from February to early March 2015. This study area was divided into three regions, namely, the “open-ocean” region, “sea-ice” region and “shelf” region. The distribution of oceanic pCO2 was mainly affected by physical processes in the open-ocean region, where mixing and upwelling were the main controls. In the sea-ice region, oceanic pCO2 changed sharply due to the strong change in seasonal ice. In the shelf region, biological factors were the main control. The weekly oceanic pCO2 was estimated using a self-organizing map (SOM) with four proxy parameters (sea surface temperature, chlorophyll a concentration, mixed Layer Depth and sea surface salinity) to overcome the complex relationship between the biogeochemical and physical conditions in the Prydz Bay region. The reconstructed oceanic pCO2 data coincide well with the in situ pCO2 data from SOCAT, with a root mean square error of 22.14 µatm. Prydz Bay was mainly a strong CO2 sink in February 2015, with a monthly averaged uptake of 23.57±6.36 TgC. The oceanic CO2 sink is pronounced in the shelf region due to its low oceanic pCO2 values and peak biological production.

38

Luo, G., та F. Yu. "A numerical evaluation of global oceanic emissions of α-pinene and isoprene". Atmospheric Chemistry and Physics 10, № 4 (19 лютого 2010): 2007–15. http://dx.doi.org/10.5194/acp-10-2007-2010.

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Abstract. A numerical evaluation of global oceanic emissions of α-pinene and isoprene based on both "bottom-up" and "top-down" methods is presented. We infer that the global "bottom-up" oceanic emissions of α-pinene and isoprene are 0.013 TgC yr−1 and 0.32 TgC yr−1, respectively. By constraining global chemistry model simulations with the shipborne measurement of Organics over the Ocean Modifying Particles in both Hemispheres summer cruise, we derived the global "top-down" oceanic α-pinene source of 29.5 TgC yr−1 and isoprene source of 11.6 TgC yr−1. Both the "bottom-up" and "top-down" values are subject to large uncertainties. The incomplete understanding of the in-situ phytoplankton communities and their range of emission potentials significantly impact the estimated global "bottom-up" oceanic emissions, while the estimated total amounts of the global "top-down" oceanic sources can be influenced by emission parameterizations, model and input data spatial resolutions, boundary layer mixing processes, and the treatments of chemical reactions. The global oceanic α-pinene source and its impact on organic aerosol formation is significant based on "top-down" method, but is negligible based on "bottom-up" approach. Our research highlights the importance of carrying out further research (especially measurements) to resolve the large offset in the derived oceanic organic emission based on two different approaches.

39

Ku, Teh-Lung, and Shangde Luo. "New appraisal of radium 226 as a large-scale oceanic mixing tracer." Journal of Geophysical Research 99, no. C5 (1994): 10255. http://dx.doi.org/10.1029/94jc00089.

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40

TAKATA, Masashi, Toru YAMASHIRO, Kazuyoshi JYOMOTO, Hirohiko NAKAMURA, Masaki UCHIYAMA, Ryuji FUKUDA, and Ayako NISHINA. "CHARACTERISTICS OF OCEANIC WATER INFLOW INTO KAGOSHIMA BAY DURING WINTER-MIXING PERIOD." Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 67, no. 2 (2011): I_715—I_720. http://dx.doi.org/10.2208/jscejoe.67.i_715.

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41

Austin, Jill, and John Green. "The role of baroclinic eddies in mixing tritium into the oceanic gyres." Tellus B: Chemical and Physical Meteorology 37, no. 3 (May 1985): 182–85. http://dx.doi.org/10.3402/tellusb.v37i3.15018.

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42

Huisman, Jef, Nga N. Pham Thi, David M. Karl, and Ben Sommeijer. "Reduced mixing generates oscillations and chaos in the oceanic deep chlorophyll maximum." Nature 439, no. 7074 (January 2006): 322–25. http://dx.doi.org/10.1038/nature04245.

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43

Simó, Rafel, and Carlos Pedrós-Alió. "Role of vertical mixing in controlling the oceanic production of dimethyl sulphide." Nature 402, no. 6760 (November 1999): 396–99. http://dx.doi.org/10.1038/46516.

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44

Rutgersson, A., A. Smedman, and E. Sahlée. "Oceanic convective mixing and the impact on air-sea gas transfer velocity." Geophysical Research Letters 38, no. 2 (January 2011): n/a. http://dx.doi.org/10.1029/2010gl045581.

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45

AUSTIN, JILL, and JOHN GREEN. "The role of baroclinic eddies in mixing tritium into the oceanic gyres." Tellus B 37B, no. 3 (July 1985): 182–85. http://dx.doi.org/10.1111/j.1600-0889.1985.tb00066.x.

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46

Morel, Yves, and James McWilliams. "Effects of Isopycnal and Diapycnal Mixing on the Stability of Oceanic Currents." Journal of Physical Oceanography 31, no. 8 (August 2001): 2280–96. http://dx.doi.org/10.1175/1520-0485(2001)031<2280:eoiadm>2.0.co;2.

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47

ALDANMAZ, E., M. K. YALINIZ, A. GÜCTEKIN, and M. C. GÖNCÜOĞLU. "Geochemical characteristics of mafic lavas from the Neotethyan ophiolites in western Turkey: implications for heterogeneous source contribution during variable stages of ocean crust generation." Geological Magazine 145, no. 1 (November 30, 2007): 37–54. http://dx.doi.org/10.1017/s0016756807003986.

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AbstractThe Late Triassic to Late Cretaceous age mafic lavas from the Neotethyan suture zone ophiolites in western Turkey exhibit a wide diversity of geochemical signatures, indicating derivation from extremely heterogeneous mantle sources. The rocks as a whole can be divided into three broad subdivisions based on their bulk-rock geochemical characteristics: (1) mid-ocean ridge basalts (MORB) that range in composition from light rare earth element (LREE)-depleted varieties (N-MORB; (La/Sm)N<1) through transitional MORB to LREE enriched types (E-MORB; (La/Sm)N>1); (2) the ocean island basalt (OIB)-type alkaline volcanic rocks with significant enrichment in LILE, HFSE and L-MREE, and a slight depletion in HREE, relative to normal mid-ocean ridge basalts (N-MORB); and (3) the supra-subduction zone (SSZ)-type tholeiites originated from arc mantle sources that are characterized by selective enrichments in fluid-soluble large ion lithophile elements (LILE) and LREE relative to the high field strength elements (HFSE). The formation of MORB tholeiites with variable enrichments and depletions in incompatible trace elements is probably related to the processes of crust generation along an oceanic spreading system, and the observed MORB–OIB associations can be modelled by heterogeneous source contribution and mixing of melts from chemically discrete sources from sub-lithospheric reservoirs. Evaluation of trace element systematics shows that the inferred heterogeneities within the mantle source regions are likely to have originated from continuous processes of formation and destruction of enriched mantle domains by long-term plate recycling, convective mixing and melt extraction. The origin of SSZ-type tholeiites with back-arc basin affinities, on the other hand, can be attributed to the later intra-oceanic subduction and plate convergence which led to the generation of supra-subduction-type oceanic crust as a consequence of imparting a certain extent of subduction component into the mantle melting region. Mixing of melts from a multiply depleted mantle source, which subsequently received variable re-enrichment with a subduction component, is suggested to explain the generation of supra-subduction-type oceanic crust. The geodynamic setting in which much of the SSZ-type ophiolitic extrusive rocks from western Turkey were generated can be described as an arc-basin system that is characterized by an oceanic lithosphere generation most probably associated with melting of mantle material along a supra-subduction-type spreading centre.

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Stevens, C. L., C. L. Stewart, N. J. Robinson, M. J. M. Williams, and T. G. Haskell. "Flow and mixing around a glacier tongue." Ocean Science Discussions 7, no. 4 (August 11, 2010): 1439–67. http://dx.doi.org/10.5194/osd-7-1439-2010.

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Abstract. A glacier tongue floating in the coastal ocean presents a significant obstacle to the local flow and influences oceanic mixing and transport processes. Here ocean shear microstructure observations at a glacier tongue side-wall show tidally-induced flow pulses and vortices as well as concomitant mixing. Flow speeds within the pulses reached around three times that of the ambient tidal flow amplitude and generated vertical velocity shear as large as 3×10−3 s−1. During the maximum flow period turbulent energy dissipation rates reached a maximum of 10−5 m2 s−3, around three decades greater than local background levels. This is in keeping with estimates of the gradient Richardson Number which dropped to around unity. Associated vertical diffusivities are higher that expected from parameterization, possibly reflecting the proximity of the cryotopography.

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Gačić, Miroslav, and Manuel Bensi. "Ocean Exchange and Circulation." Water 12, no. 3 (March 20, 2020): 882. http://dx.doi.org/10.3390/w12030882.

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The great spatial and temporal variability, which characterizes the marine environment, requires a huge effort to be observed and studied properly since changes in circulation and mixing processes directly influence the variability of the physical and biogeochemical properties. A multi-platform approach and a collaborative effort, in addition to optimizing both data collection and quality, is needed to bring the scientific community to more efficient monitoring and predicting of the world ocean processes. This Special Issue consists of nine original scientific articles that address oceanic circulation and water mass exchange. Most of them deal with mean circulation, basin and sub-basin-scale flows, mesoscale eddies, and internal processes (e.g., mixing and internal waves) that contribute to the redistribution of oceanic properties and energy within the ocean. One paper deals with numerical modelling application finalized to evaluate the capacity of coastal vegetated areas to mitigate the impact of a tsunami. The study areas in which these topics are developed include both oceanic areas and semi-enclosed seas such as the Mediterranean Sea, the Norwegian Sea and the Fram Strait, the South China Sea, and the Northwest Pacific. Scientific findings presented in this Special Issue highlight how a combination of various modern observation techniques can improve our understanding of the complex physical and biogeochemical processes in the ocean.

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Sokolov, Andrei P., Chris E. Forest, and Peter H. Stone. "Comparing Oceanic Heat Uptake in AOGCM Transient Climate Change Experiments." Journal of Climate 16, no. 10 (May 15, 2003): 1573–82. http://dx.doi.org/10.1175/1520-0442-16.10.1573.

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Abstract The transient response of both surface air temperature and deep ocean temperature to an increasing external forcing strongly depends on climate sensitivity and the rate of the heat mixing into the deep ocean, estimates for both of which have large uncertainty. In this paper a method for estimating rates of oceanic heat uptake for coupled atmosphere–ocean general circulation models from results of transient climate change simulations is described. For models considered in this study, the estimates vary by a factor of 2½. Nevertheless, values of oceanic heat uptake for all models fall in the range implied by the climate record for the last century. It is worth noting that the range of the model values is narrower than that consistent with observations and thus does not provide a full measure of the uncertainty in the rate of oceanic heat uptake.

Статті в журналах з теми "Oceanic mixing"

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