4,646 research outputs found
Bifurcations of the thermohaline circulation in a simplified three-dimensional model of the world ocean and the effects of inter-basin connectivity
No full textA coarse-resolution, global, three-dimensional, idealised model of the world ocean, based on the thermocline equations, is described. It is demonstrated that, at suitable resolution, such a model can be integrated for hundreds or thousands of millenia, and could therefore form a component of an earth system model designed to investigate climate change on these time scales. As in other ocean models, the thermohaline circulation is found to exhibit multiple stable states. The bifurcation structure of the model has been explored, as a function of surface saline forcing, and is found to depend on the inter-basin connectivity, the topography, and the form of the imposed wind forcing
Linear and double-diffusive-inertial instability at the equator
No full textMotivated by observations of interleaving in the equatorial Pacific, we consider the linear stability of a basic state on an equatorial [beta]-plane which is susceptible to both double-diffusive interleaving, driven by a meridional salinity gradient, and inertial instability driven by meridional shear. In a parameter regime compatible with the observations strong interaction can occur between the two processes, indicating that the stability of the system is dependent on the meridional gradients of both salinity and zonal velocity. Meridional shear is found to enhance the interleaving motion even for values of shear well below the cutoff for inertial instability. In the presence of diffusion inertial instability can also be excited by vertical shear, but only if the shear is comparable to the buoyancy frequency. When double-diffusive driving is weak relative to inertial driving the growth can be oscillatory, in which case the mechanism for instability is viscous–diffusive. In this case interleaving layers can slope downwards towards the fresh side of the front in the fingering regime, inhibiting their own growth
Parameter estimation in an intermediate complexity earth system model using an ensemble Kalman filter
No full textWe describe the development of an efficient method for parameter estimation and ensemble forecasting in climate modelling. The technique is based on the ensemble Kalman filter and is several orders of magnitude more efficient than many others which have been previously used to address this problem. As well as being theoretically (near-)optimal, the method does not suffer from the 'curse of dimensionality' and can comfortably handle multivariate parameter estimation. We demonstrate the potential of this method in identical twin testing with an intermediate complexity coupled AOGCM. The model's climatology is successfully tuned via the simultaneous estimation of 12 parameters. Several minor modifications arc described
by which the method was adapted to a steady state (temporally averaged) case. The method is relatively simple to implement, and with only O(50) model runs required, we believe that optimal parameter estimation is now accessible even to computationally demanding models
Poems / by M. Betham-Edwards Author Of "The White House By The Sea" ...
No full textPOEMS / BY M. BETHAM-EDWARDS AUTHOR OF "THE WHITE HOUSE BY THE SEA" ...
Poems / by M. Betham-Edwards Author Of "The White House By The Sea" ... (1)
Cover (1)
Title page (3)
Titelseite (5)
Widmung (7)
Note (8)
Contents (11)
Love (15)
Recollection - The Life That Is Life (17)
Religion (83)
The Praise Of Light - L'Envoi (85)
Nature (101)
Child's Summer Song - March Music (103)
Chapter (118)
The Work-A-Day World And Romance (119)
The Wife's Prayer - The English Shipwrecked Off Finistère (121)
Translations (187)
The Gascon's River - Verselets (189
Location of potential energy sources and the export of dense water from the Atlantic Ocean
No full textThe export of dense water from the Atlantic and into the Indo-Pacific oceans, and heat transport in the opposite direction, is traditionally attributed to the fact that dense water forms in the Atlantic but not the Pacific. Evidence from two models, presented here, suggests this is an incomplete explanation. It is found that dense water export from the Atlantic depends on a potential energy (PE) sink, associated with dense water downwelling in the Atlantic, that is not balanced by a PE source within the Atlantic. Therefore, increasing the Atlantic PE source reduces dense Atlantic water export. Tide models suggest that the Atlantic PE source may have been much higher at the last glacial maximum. This could have significantly reduced dense water export from the Atlantic Ocean, even if Atlantic overturning was stronger than it is today
An efficient climate forecasting method using an intermediate complexity Earth system model and the ensemble Kalman Filter
No full textWe present the implementation and results of a model tuning and ensemble forecasting experiment using an ensemble Kalman filter for the simultaneous estimation of 12 parameters in a low resolution coupled atmosphere-ocean Earth System Model by tuning it to realistic data sets consisting of Levitus ocean temperature/salinity climatology, and NCEP/NCAR atmospheric temperature/humidity reanalysis data. The resulting ensemble of tuned model states is validated by comparing various diagnostics, such as mass and heat transports, to observational estimates and other model results. We show that this ensemble has a very reasonable climatology, with the 3-D ocean in particular having comparable realism to much more expensive coupled numerical models, at least in respect of these averaged indicators. A simple global warming experiment is performed to investigate the response and predictability of the climate to a change in radiative forcing, due to 100 years of 1% per annum atmospheric CO2 increase. The equilibrium surface air temperature rise for this CO2 increase is 4.2±0.1°C, which is approached on a time scale of 1,000 years. The simple atmosphere in this version of the model is missing several factors which, if included, would substantially increase the uncertainty of this estimate. However, even within this ensemble, there is substantial regional variability due to the possibility of collapse of the North Atlantic thermohaline circulation (THC), which switches off in more than one third of the ensemble members. For these cases, the regional temperature is not only 3–5°C colder than in the warmed worlds where the THC remains switched on, but is also 1–2°C colder than the current climate. Our results, which illustrate how objective probabilistic projections of future climate change can be efficiently generated, indicate a substantial uncertainty in the long-term future of the THC, and therefore the regional climate of western Europe. However, this uncertainty is only apparent in long-term integrations, with the initial transient response being similar across the entire ensemble. Application of this ensemble Kalman filtering technique to more complete climate models would improve the objectivity of probabilistic forecasts and hence should lead to significantly increased understanding of the uncertainty of our future climate
Exploratory talk within collaborative small groups in mathematics
No full textThis report describes one aspect of a wider research study on exploratory talk within collaborative small groups in secondary mathematics lessons. It outlines students’ views of using collaborative activity to learn mathematics. The fuller research study explores the extent to which exploratory talk occurs in collaborative peer groups in secondary mathematics classrooms
The Scotsman, the Greek, the Mauritian company and the Internet: where on earth do things happen in cyberspace?
No full textThe author discusses the problems posed by internet jurisdiction, using the Bonnier Media case as an example. Edwards draws on legislative measures, in particular, the European Commission's Brussels 1 and 2 to expand the argument, and attempts to understand the complexities of the "where" in "where do things happen in cyberspace"
Incorporation of the C-GOLDSTEIN efficient climate model into the GENIE framework: "eb_go_gs" configurations of GENIE
No full textA computationally efficient, intermediate complexity ocean-atmosphere-sea ice model (C-GOLDSTEIN) has been incorporated into the Grid ENabled Integrated Earth system modelling (GENIE) framework. This involved decoupling of the three component modules that were re-coupled in a modular way, to allow replacement with alternatives and coupling of further components within the framework. The climate model described here (referred to as "eb_go_gs" for short) is the most basic version of GENIE in which atmosphere, ocean and sea ice all play an active role. Among improvements on the original C-GOLDSTEIN model, latitudinal grid resolution is generalized to allow a wider range of surface grids to be used. The ocean, atmosphere and sea-ice components of the "eb_go_gs" configuration of GENIE are individually described, along with details of their coupling. The setup and results from simulations using four different meshes are presented. The four alternative meshes comprise the widely-used 36 × 36 equal-area-partitioning of the Earth surface with 16 depth layers in the ocean, a version in which horizontal and vertical resolution are doubled, a setup matching the horizontal resolution of the dynamic atmospheric component available in the GENIE framework, and a setup with enhanced resolution in high-latitude areas. Results are presented for a spin-up experiment with a baseline parameter set and wind forcing typically used for current studies in which "eb_go_gs" is coupled with the ocean biogeochemistry module of GENIE, as well as for an experiment with a modified parameter set, revised wind forcing, and additional cross-basin transport pathways (Indonesian and Bering Strait throughflows). The latter experiment is repeated with the four mesh variants, with common parameter settings throughout, except for time-step length. Selected state variables and diagnostics are compared in two regards: (i) between simulations at lowest resolution that are obtained with the baseline and modified configurations, predominantly in order to evaluate the revision of the wind forcing, the modification of some key parameters, and the effect of additional transport pathways across the Arctic Ocean and the Indonesian Archipelago; (ii) between simulations with the four meshes, in order to explore various effects of mesh choice.<br/
Islam and politics in the contemporary world
No full textThe dreadful events of 11 September have brought Islam to the forefront of world politics. This authoritative new book provides the analysis for a far-reaching introduction to Islamic politics for those coming to the subject for the first time. This account provides a deep insight into dimensions of Muslim political life; from democracy to despots, women to world affairs and history to heresy. Milton-Edwards offers an account of key contemporary concepts and debates that focus on the relationship between Islam and topical issues including politics, protest and opposition, violence, the West, democracy, the state and women. Giving an broad global overview the author includes a range of first-hand interviews with major Islamic figures and leaders of movements. Milton-Edwards charts the development of a political trend in Islam throughout the twentieth century and explores its myriad dimensions. The author also explores the prospects for political Islam in the new millennium. With further reading suggestions, and a glossary, Islam and Politics in the Contemporary World is an indispensable introduction to the subject and will prove invaluable as a textbook for students of politics and religion
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