Continuum-mechanical, Anisotropic Flow model for polar ice masses, based on an anisotropic Flow Enhancement factor

A complete theoretical presentation of the Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor (CAFFE model) is given. The CAFFE model is an application of the theory of mixtures with continuous diversity for the case of large polar ice masses in which induced anisotropy occurs. The anisotropic response of the polycrystalline ice is described by a generalization of Glen's flow law, based on a scalar anisotropic enhancement factor. The enhancement factor depends on the orientation mass density, which is closely related to the orientation distribution function and describes the distribution of grain orientations (fabric). Fabric evolution is governed by the orientation mass balance, which depends on four distinct effects, interpreted as local rigid body rotation, grain rotation, rotation recrystallization (polygonization) and grain boundary migration (migration recrystallization), respectively. It is proven that the flow law of the CAFFE model is truly anisotropic despite the collinearity between the stress deviator and stretching tensors.Comment: 22 pages, 5 figure

Lessons and challenges in land change modeling derived from synthesis of cross-case comparisons

This chapter presents the lessons and challenges in land change modeling that emerged from years of reflection and numerous panel discussions at scientific conferences concerning a collaborative cross-case comparison in which the authors have participated. We summarize the lessons as nine challenges grouped under three themes: mapping, modeling, and learning. The mapping challenges are: to prepare data appropriately, to select relevant resolutions, and to differentiate types of land change. The modeling challenges are: to separate calibration from validation, to predict small amounts of change, and to interpret the influence of quantity error. The learning challenges are: to use appropriate map comparison measurements, to learn about land change processes, and to collaborate openly. To quantify the pattern validation of predictions of change, we recommend that modelers report as a percentage of the spatial extent the following measurements: misses, hits, wrong hits and false alarms. The chapter explains why the lessons and challenges are essential for the future research agenda concerning land change modeling. (Résumé d'auteur

Beeswax rock art from Limmen National Park (Northern Territory), northern Australia: new insights into technique-based patterning and absence in the rock art record

The known geographic distribution of beeswax rock art is largely restricted to the Arnhem Land plateau and Kimberley regions of northern Australia. While considerable research has focussed on the antiquity and meaning of beeswax rock art, much less attention has been directed to the nature and extent of the distribution pattern for this unique motif production technique. In this article, we present details of two beeswax motifs recently discovered in Marra Country at Limmen National Park (southwest Gulf of Carpentaria, Northern Territory). In the first instance, the motifs are explored in the context of their meaning, drawing on ethnography collected in the region over the last 40 years. The motifs are then used as a platform to engage with questions around the low frequency, and in some cases complete absence, of beeswax rock art across other areas of northern Australia. While it is highly unlikely there is one single, homogenous explanation for this in the Gulf country and northeastern Australia, we suggest that exploring the social, cultural and relational understandings of beeswax in these areas offers considerable potential to understand better how people engaged with and inscribed their cultural landscapes