Woods Hole Oceanographic Institution

About: Woods Hole Oceanographic Institution is a nonprofit organization based out in Falmouth, Massachusetts, United States. It is known for research contribution in the topics: Population & Mantle (geology). The organization has 5685 authors who have published 18396 publications receiving 1202050 citations. The organization is also known as: WHOI.

Sensitivity of decomposition rates of soil organic matter with respect to simultaneous changes in temperature and moisture

Abstract: The sensitivity of soil organic matter decomposition to global environmental change is a topic of prominent relevance for the global carbon cycle. Decomposition depends on multiple factors that are being altered simultaneously as a result of global environmental change; therefore, it is important to study the sensitivity of the rates of soil organic matter decomposition with respect to multiple and interacting drivers. In this manuscript, we present an analysis of the potential response of decomposition rates to simultaneous changes in temperature and moisture. To address this problem, we first present a theoretical framework to study the sensitivity of soil organic matter decomposition when multiple driving factors change simultaneously. We then apply this framework to models and data at different levels of abstraction: (1) to a mechanistic model that addresses the limitation of enzyme activity by simultaneous effects of temperature and soil water content, the latter controlling substrate supply and oxygen concentration for microbial activity; (2) to different mathematical functions used to represent temperature and moisture effects on decomposition in biogeochemical models. To contrast model predictions at these two levels of organization, we compiled different data sets of observed responses in field and laboratory studies. Then we applied our conceptual framework to: (3) observations of heterotrophic respiration at the ecosystem level; (4) laboratory experiments looking at the response of heterotrophic respiration to independent changes in moisture and temperature; and (5) ecosystem-level experiments manipulating soil temperature and water content simultaneously.

Warm-Bodied Fish

Abstract: SYNOPSIS. Two groups of fishes, the tuna and the lamnid sharks, have evolved ounter-currentheat-exchange mechanisms for conserving metabolic heat and raising their body temperatures. Warm muscle can produce more power, and considering the other adaptations for fast swimming in these fish, it seems likely that the selective advantages of greater speed made possible by the warm muscle were important in the evolution of this system. Some tunas such as the yellowfin and skip jack are at a fixed temperature difference above the water, but bluefin tuna can thermoregulate. Telemetry experiments show that the bluefin tuna can maintain a constant deep body temperature during marked changes in the temperature of its environment.

Mixing in the Romanche Fracture Zone

Abstract: The Romanche Fracture Zone is a major gap in the Mid-Atlantic Ridge at the equator, which is deep enough to allow significant eastward flows of Antarctic Bottom Water from the Brazil Basin to the Sierra Leone and Guinea Abyssal Plains. While flowing through the Romanche Fracture Zone, bottom-water properties are strongly modified due to intense vertical mixing. The diapycnal mixing coefficient in the bottom water of the Romanche Fracture Zone is estimated by using the finestructure of CTD profiles, the microstructure of high-resolution profiler data, and by constructing a heat budget from current meter data. The finestructure of density profiles is described using the Thorpe scalesLT. It is shown from microstructure data taken in the bottom water that the Ozmidov scale LO is related to LT by the linear relationship LO 5 0.95LT, similar to other studies, which allows an estimate of the diapycnal mixing coefficient using the Osborn relation. The Thorpe scale and the diapycnal mixing coefficient estimates show enhanced mixing downstream (eastward) of the main sill of the Romanche Fracture Zone. In this region, a mean diapycnal mixing coefficient of about 1000 3 1024 m2 s21 is found for the bottom water. Estimates of cross-isothermal mixing coefficient derived from the heat budgets constructed downstream of the current meter arrays deployed in the Romanche Fracture Zone and the nearby Chain Fracture Zone are in agreement with the finestructure estimates of the diapycnal mixing coefficient within the Romanche Fracture Zone. Although the two fracture zones occupy only 0.4% of the area covered by the Sierra Leone and Guinea Abyssal Plains, the diffusive heat fluxes across the 1.4 8C isotherm in the Romanche and Chain Fracture Zones are half that found over the abyssal plains across the 1.88C isotherm, emphasizing the role of these passages for bottom-water property modifications.

The influence of water on the petrogenesis of subductionrelated igneous rocks

Abstract: THE presence of dissolved water can significantly change the sequence in which different minerals crystallize from a silicate magma1–3. This will alter the compositional path followed by residual liquids (the liquid line of descent'), and modify the types and compositions of crystals that accumulate at the site of cooling. The sharp decrease in the solubility of water in silicate melts with decreasing pressure makes direct measurements of pre-eruptive concentrations in magmas difficult because much of the dissolved water boils off before eruption. Here we report experimental results on the crystallization of basalts that contain substantial dissolved water (up to 6 wt%), and show how the results can be used to infer the amount of dissolved H2O involved in the petrogenesis of lavas that preserve a record of their liquid lines of descent, or the accumulated minerals left behind after solidification. The presence of abundant magmatic water is a signature of subduction-zone volcanism4, and can be used to associate a suite of magmas or igneous cumulates with a convergent-margin, back-arc or interarc tectonic setting.

Outline of a theory of turbulent shear flow

Abstract: In this paper the spatial variations and spectral structure of steady-state turbulent shear flow in channels are investigated without the introduction of empirical parameters. This is made possible by the assumption that the non-linear momentum transport has only stabilizing effects on the mean field of flow. Two constraints on the possible momentum transport are drawn from this assumption: first, that the mean flow will be statistically stable if an Orr-Sommerfeld type equation is satisfied by fluctuations of the mean; second, that the smallest scale of motion that can be present in the spectrum of the momentum transport is the scale of the marginally stable fluctuations of the mean. Within these two constraints, and for a given mass transport, an upper limit is sought for the rate of dissipation of potential energy into heat. Solutions of the stability equation depend upon the shape of the mean velocity profile. In turn, the mean velocity profile depends upon the spatial spectrum of the momentum transport. A variational technique is used to determine that momentum transport spectrum which is both marginally stable and produces a maximum dissipation rate. The resulting spectrum determines the velocity profile and its dependence on the boundary conditions. Past experimental work has disclosed laminar, ‘transitional’, logarithmic and parabolic regions of the velocity profile. Several experimental laws and their accompanying constants relate the extent of these regions to the boundary conditions. The theoretical profile contains each feature and law that is observed. First approximations to the constants are found, and give, in particular, a value for the logarithmic slope (von Karman's constant) which is within the experimental error. However, the theoretical boundary constant is smaller than the observed value. Turbulent channel flow seems to achieve the extreme state found here, but a more decisive quantitative comparison of theory and experiment requires improvement in the solutions of the classical laminar stability problem.