Bridging the gap: linking climate-impacts research with adaptation planning and management

A critical challenge in supporting climate change adaptation is improving the linkage between climate-impacts and vulnerability research and public and private planning and management decisions. We highlight the need for bottom-up/top-down vulnerability assessment, bringing together bottom-up knowledge of existing vulnerabilities with top-down climate-impact projections, as a transparent basis for informing decisions intended to reduce vulnerability. This approach can be used to evaluate the likelihood of crossing identified thresholds of exposure, and to evaluate alternative adaptation strategies based on their ability to reduce sensitivity to projected changes in exposure and their robustness across uncertainty in future outcomes. By identifying thresholds for which adaptive capacity is limited in particular systems, adaptation and mitigation become complements where the magnitudes of climate change at which such thresholds cluster can help to define mitigation targets.     

Elastic thickness estimates at northeast passive margin of North America and its implications

Global estimates of the elastic thickness (Te) of the structure of passive continental margins show wide and varying results owing to the use of different methodologies. Earlier estimates of the elastic thickness of the North Atlantic passive continental margins that used flexural modelling yielded a Te value of ~20–100 km. Here, we compare these estimates with the Te value obtained using orthonormalized Hermite multitaper recovered isostatic coherence functions. We discuss how Te is correlated with heat flow distribution and depth of necking. The E–W segment in the southern study region comprising Nova Scotia and the Southern Grand Banks show low Te values, while the zones comprising the NE–SW zones, viz., Western Greenland, Labrador, Orphan Basin and the Northern Grand Bank show comparatively high Te values. As expected, Te broadly reflects the depth of the 200–400°C isotherm below the weak surface sediment layer at the time of loading, and at the margins most of the loading occurred during rifting. We infer that these low Te measurements indicate Te frozen into the lithosphere. This could be due to the passive nature of the margin when the loads were emplaced during the continental break-up process at high temperature gradients.     

Numerical simulations of interacting gas-rich barred galaxies: vertical impact of small companions

We investigate the dynamical effects of an interaction between an initially barred galaxy and a small spherical companion using an N -body/smoothed-particle-hydrodynamics algorithm. In the models described here the small companion passes through the disc of the larger galaxy nearly perpendicular to its plane. The impact positions and times are varied with respect to the phase of the bar and the dynamical evolution of the disc.
The interactions produce expanding ring structures, offset bars, spokes and other asymmetries in the stars and gas. These characteristic signatures of the interaction are present in the disc for about 1 Gyr. We find that in some cases it is possible to destroy the bar while keeping the disc structure. In general, the central impacts cause larger damage to the bar and the disc than the peripheral ones. The interaction tends to accelerate the transition from a strongly-barred galaxy to a weakly- or non-barred galaxy. The final disc morphology is determined more by the impact position relative to the bar rather than the impact time.     

The Two Fixed Centers: An Exceptional Integrable System

It is usually believed that we know everything to be known for any separable Hamiltonian system, i.e. an integrable system in which we can separate the variables in some coordinate system (e.g. see Lichtenberg and Lieberman 1992, Regular and Chaotic Dynamics, Springer). However this is not always true, since through the separation the solutions may be found only up to quadratures, a form that might not be particularly useful. A good example is the two-fixed-centers problem. Although its integrability was discovered by Euler in the 18th century, the problem was far from being considered as completely understood. This apparent contradiction stems from the fact that the solutions of the equations of motion in the confocal ellipsoidal coordinates, in which the variables separate, are written in terms of elliptic integrals, so that their properties are not obvious at first sight. In this paper we classify the trajectories according to an exhaustive scheme, comprising both periodic and quasi-periodic ones. We identify the collision orbits (both direct and asymptotic) and find that collision orbits are of complete measure in a 3-D submanifold of the phase space while asymptotically collision orbits are of complete measure in the 4-D phase space. We use a transformation, which regularizes the close approaches and, therefore, enables the numerical integration of collision trajectories (both direct and asymptotic). Finally we give the ratio of oscillation period along the two axes (the ‘rotation number’) as a function of the two integrals of motion. This revised version was published online in July 2006 with corrections to the Cover Date.     

青藏高原东北部地区的区域地壳现今构造形变系统——陆壳浅源构造地震成因的新认识

依据青藏高原东北部地区的大震（Ｍｓ≥７）,大震形变带、活动断裂和活动的构造体系的资料,以地球系统科学、地质力学、地震地质学、现代地震学的理论和方法为主线,对该区内大震的“共性”进行了探讨,提出了具有三维空间动态地壳现今构造形变系统的新概念,并对该区内地震的形成机制、分布规律等问题提出了新的见解。     

An efficient method of generating random permeability fields by the source point method

Aquifer properties, for example permeability and porosity, vary in space and may be characterized by their distributions. The property distribution is not totally random but shows some correlation structure. Because most of the values are not known, some rational method is required to generate credible aquifer distribution properties for inclusion in fluid transport models. This paper presents a numerically efficient method of generating geostatistical random fields, by the source Point Method (SPM). The SPM is a very efficient method and requires little computer time and relatively small data storage, as compared to other methods of generating random fields. In addition, the SPM is modified to include any desired amount of anisotropy in the property distribution of a system. By using conditional covariances, a formula for a two-dimensional anisotropic field is derived to prespecify the desired correlation length in any direction. Results show that for an anisotropic medium the correlation length can be pre-specified in any specific direction.     

Mach's principle and bundle of geometric quantities

It is shown that the bundle of geometric quantities σ(M) over a space-timeM is a strong anti-Machian element ofM.     

QUELQUES EXEMPLES D'APPLICATION DES MESURES DE RAYONNEMENT À LA DÉTERMINATION DE L'ÉVAPO-TRANSPIRATION EN CLIMAT TROPICAL

ABSTRACT

From data obtained at stations set up in Chad, the Central African Republic and Congo-Brazzaville, stretching from the desert to the equatorial zone, it has been possible to compare measurements of evapotranspiration and of evaporation with results obtained by using the energy-balance method. Several difficulties arise in these comparisons since the scale of the measurements (small evaporating surfaces) is generally different from that of the climatic characteristics on which evaporation is dependent.

After proposing a model to resolve this problem and fitting the empirical coefficients of Penman's formula, the author has applied this formula to some results derived for stations in Congo-Brazzaville; the potential evapotranspiration calculated in this way is in good agreement with water balance data.

At these stations the evapotranspiration energy may be a constant percentage of global short-wave radiation.

Finally, the energy-balance method has been used at Brazzaville to measure the actual evapotranspiration over grass during the dry season. The result is that actual and potential evapotranspiration were found to be closely related.

These results indicate the importance of solar readiation in the field of hydrometeorology.     

Geomagnetic secular variation in historical lavas from the Canary Islands

Summary. The age of historical lava flows on the Canary Islands can be traced back at least to 1585 ad . During the last 400 years eruptions occurred at fairly regular intervals. The palaeomagnetic directions of these lavas record the ambient field direction with high precision so that an historical secular variation curve (SVC) can be constructed for the Canaries which closely resembles the curve registered at Paris. The SVC can be used as a dating tool for historical eruptions of unknown age and can probably be extended into the last 4000–5000 yr of recent volcanic activity on the Canaries.