Atoll d'Eniwetok, Système géothermique insulaire à l'état naturel

Samaden, G.; Dallot, P.; Roche, R.

doi:10.1051/lhb/1985006

Cited by 12 publications

(5 citation statements)

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“…Therefore, λ r = 2.4 ± 0.4 W/(mK), if one considers that the thermal conductivity of water under condition is λ w = 0.6 ± 0.1 W/(mK). This value is in agreement with the empirical model of Samaden et al [8] and fits in the range of conductivity of most parts of rocks [10].…”

Section: Resultssupporting

confidence: 91%

“…From the temperature field data, thermal conductivity can be assessed by Fourier's law models, Ohm's law models, or by empirical model. Samaden et al [8] used Darcy's law, the continuity equation, and the heat equation to develop a semiempirical multilayer model of the Eniwetak atoll. They estimated the thermal conductivity of the Eniwetok atoll to be between 2.5 to 5 W/(mK).…”

Section: Introductionmentioning

confidence: 99%

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A Model to Evaluate the Thermal Conductivity of the Coral Reef in Tahiti

Guarino

2011

Physics Research International

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Ohm's law models have been used in several works in geophysical prospecting but have never been used for coral reef. We adapted such a model to the barrier reef of Papeete (Tahiti island) in order to estimate of its thermal conductivity. We found the thermal conductivity of the barrier reef is about four times greater than that of the water. The results are then validated by the mean of experimental measurements.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

A Model to Evaluate the Thermal Conductivity of the Coral Reef in Tahiti

Guarino

2011

Physics Research International

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“…In summary, these results with a homogeneous reef show that density-driven flows occur inside atoll carbonate platforms, in agreement with previous work by Samaden et al (1985) and Henry et al (1996). These flows result from the thermal boundary conditions (assigned temperatures and geothermal flux) and from coupling between hydraulic and thermal regimes.…”

Section: Symbolsupporting

confidence: 91%

“…The carbonate platform lies upon a basaltic bedrock ( Fig. 1), which has a hydraulic conductivity almost three orders of magnitude lower than that of the carbonate (Samaden et al 1985;Guille et al 1993). Henry et al (1996) modeled Mururoa atoll with both of the geological domains to evaluate water residence time inside the volcanic bedrock and to check that velocities were small enough to prevent any hazardous radioactive leakage.…”

Section: Equations and Modelingmentioning

confidence: 99%

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Density‐induced water circulations in atoll coral reefs: A numerical study

Leclerc¹,

Jean‐Baptiste²,

Texier³

et al. 1999

Limnology & Oceanography

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Groundwater flow in an idealized atoll platform is simulated with CASTEM 2000, a computer code developed at the CEA (Commissariat à l'Energie Atomique). Darcy's law and a coupled solute transport equation (diffusion-dispersion-convection) is solved by the mixed-hybrid finite-element method. Inward and upward circulations of oceanic water are shown to occur. These steady-state circulations result from temperature and, to a lesser extent, salinity gradients. Inclusion of a karstified dolomitic horizon, observed at the base of the carbonate structure of certain atolls, is necessary to account for the negative vertical temperature gradient indicated by field data. The position of the platform in relation to the oceanic temperature and salinity distributions exerts a significant control on the interstitial hydraulic regime. The effect of a secondary karstic layer closer to sea surface is also modeled. In this case, calculations show that the near-surface carbonate edifice is deprived of a significant portion of the flow. Finally, an upper limit on the possible flow rate through the platform is calculated. This upper estimate is shown to be independent of the possible uncertainties on the hydraulic conductivity of the system. Corresponding upper limits on the nutrient fluxes of PO and NO are evaluated. A comparison with 3Ϫ Ϫ 4 3 current import and export data for the surface ecosystem indicates that in every case, nutrient fluxes hardly reach a few percent of the exports. Therefore, the deep oceanic nutrient pool brought to the surface by thermally driven interstitial circulation is only a minor nutrient source for the reef ecosystem.The composition and circulation of interstitial waters in the porous carbonate framework of coral reefs are central to our understanding of reef development and geological evolution. Atoll reef hydrology is also of prime importance to the management of fresh groundwater for communities on these islands.Hydrogeological studies of coral reefs were spurred by the American and French underground nuclear tests in Pacific atolls (Buddemeier and Holladay 1977;Wheatcraft and Buddemeier 1981). Cores drilled in atolls revealed that coral reefs are complex porous media with both horizontal and vertical heterogeneity over a wide range of spatial scales, including cracks, karsts, and strata of composite materials with different permeabilities. The occurrence of large dolomitized horizons also led geologists to suggest that reefs should be regarded as hydrologically active environments, as dolomitization requires the passage of large volumes of seawater in order to supply the necessary magnesium (Buddemeier and Oberdorfer 1986 AcknowledgmentsWe thank the Programme National pour les Récifs Coralliens (PNRCO) for financial support and the Laboratoire de Transferts Thermiques et Mécanique des Fluides (CEA) for providing us with computing facilities. We thank Jean-Pierre Gattuso for his fruitful remarks about the nutrient budget and Bernard Boudreau and two other anonymous reviewers for their help...

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Purser

Schroeder

1986

Reef Diagenesis

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Atoll d'Eniwetok, Système géothermique insulaire à l'état naturel

Cited by 12 publications

References 0 publications

A Model to Evaluate the Thermal Conductivity of the Coral Reef in Tahiti

A Model to Evaluate the Thermal Conductivity of the Coral Reef in Tahiti

Density‐induced water circulations in atoll coral reefs: A numerical study

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