Influence of Persistent Wind Scour on the Surface Mass Balance of Antarctica

Accurate quantification of surface snow accumulation over Antarctica is a key constraint for estimates of the Antarctic mass balance, as well as climatic interpretations of ice-core records. Over Antarctica, near-surface winds accelerate down relatively steep surface slopes, eroding and sublimating the snow. This wind scour results in numerous localized regions (< or = 200 sq km) with reduced surface accumulation. Estimates of Antarctic surface mass balance rely on sparse point measurements or coarse atmospheric models that do not capture these local processes, and overestimate the net mass input in wind-scour zones. Here we combine airborne radar observations of unconformable stratigraphic layers with lidar-derived surface roughness measurements to identify extensive wind-scour zones over Dome A, in the interior of East Antarctica. The scour zones are persistent because they are controlled by bedrock topography. On the basis of our Dome A observations, we develop an empirical model to predict wind-scour zones across the Antarctic continent and find that these zones are predominantly located in East Antarctica. We estimate that approx. 2.7-6.6% of the surface area of Antarctica has persistent negative net accumulation due to wind scour, which suggests that, across the continent, the snow mass input is overestimated by 11-36.5 Gt /yr in present surface-mass-balance calculations

Extensive Liquid Meltwater Storage in Firn Within the Greenland Ice Sheet

The accelerating loss of mass from the Greenland ice sheet is a major contribution to current sea level rise. Increased melt water runoff is responsible for half of Greenlands mass loss increase. Surface melt has been increasing in extent and intensity, setting a record for surface area melt and runoff in 2012. The mechanisms and timescales involved in allowing surface melt water to reach the ocean where it can contribute to sea level rise are poorly understood. The potential capacity to store this water in liquid or frozen form in the firn (multi-year snow layer) is significant, and could delay its sea-level contribution. Here we describe direct observation of water within a perennial firn aquifer persisting throughout the winter in the southern ice sheet,where snow accumulation and melt rates are high. This represents a previously unknown storagemode for water within the ice sheet. Ice cores, groundairborne radar and a regional climatemodel are used to estimate aquifer area (70 plue or minus 10 x 10(exp 3) square kilometers ) and water table depth (5-50 m). The perennial firn aquifer represents a new glacier facies to be considered 29 in future ice sheet mass 30 and energy budget calculations

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Le développement séculaire de la mortalité aux jeunes âges dans le territoire du Bénélux

The authors attempt to study juvenile (and, more specifically, infant) mortality in XIXth and early XXth-century Bénélux. Using numerous observations, they are able to highlight the trends, regional and social variations and even take into account the environment. The main deadly determinant was artificial feeding which accounted for more deaths amongst the common people than in other categories where it was, moreover, more frequently used. This is especially clear in areas where the mother's work made it necessary to resort to paid help. This phenomenon explains the increase in infant mortality observed here and there during the XIXth century.Les auteurs s'appliquent à étudier la mortalité des jeunes (et tout particulièrement la mortalité infantile) dans le Bénélux du XIXe siècle et du début du XXe. Partant de nombreuses observations, ils peuvent mettre en valeur les évolutions, les différences régionales et sociales et même tenir compte de l'environnement. Le rôle néfaste de l'allaitement artificiel constitue le facteur capital. Il est plus meurtrier dans les classes populaires que dans les autres milieux, et en outre, il y est plus employé. Ce fait est particulièrement net dans les zones où le travail de la mère impose le recours à l'élevage mercenaire. Ce phénomène explique l'aggravation notée ici ou là de la mortalité infantile au cours du XIXe siècle.Vandenbroeke Christian, van Poppel Frans, Van der Woude A. M. Le développement séculaire de la mortalité aux jeunes âges dans le territoire du Bénélux. In: Annales de démographie historique, 1983. Mères et nourrissons. pp. 257-289