Open Access Publications of the European Geosciences Union (EGU) with examples from Climate of the Past Facts, Innovative Approaches, Dissemination

This is the presentation of the EGU open access journals and how they are working using my experience of Co-editor in chief of Climate of the Past. I gave this lecture in Montpellier, France, 10 January 201

Rigorous Asymptotic Study of the Screened Electrostatic Potential in a Thin Dielectric Slab

The screened Coulomb potential plays a crucial role in the binding energies of excitons in a thin dielectric slab. The asymptotic behavior of this potential is studied when the thickness of the slab is very small as compared to the exciton Bohr radius. A regularized expression is given and the exact effective 2D potential is derived. These expressions may be useful for the computation of the exciton binding energy in 2D or quasi‐2D materials

Abrupt Climate changes Recorded in Loess Sequences

The terrestrial sediments known as "loess" represent an important archive of paleoclimatic variability. Mineral material mobilized by wind at the ground surface was transported over distances from a few hundred to thousands of kilometers and deposited back on the ground where it underwent a gradual transformation into loess sediment. The largest loess deposits are found in the Northern Hemisphere, primarily because the continental surface is much larger than the Southern Hemisphere. Depending on their location on the globe, the deposits have formed under the influence of different climate factors, and contain more or less detailed records of regional climate change. here we review the current knowledge about the three main loess regions of the Northern Hemisphere. The many underlying references are provided in an extensive online archive of references, listed by regions

A single layer representation of the scattered field for multiple scattering problems

The scattering of scalar waves by a set of scatterers is considered. It is proven that the scattered field can be represented as the integral of a density over an arbitrary smooth surface enclosing the scatterers. This is a generalization of the series expansion over spherical harmonics and spherical Bessel functions for spherical geometries. It allows an extension of the Fast Multiple Algorithm to non spherical domains.Comment: 15 pages, 10 figure

A Punctuated Equilibrium Analysis of the Climate Evolution of Cenozoic: Hierarchy of Abrupt Transitions

The Earth's climate has experienced numerous critical transitions during its history, which have often been accompanied by massive and rapid changes in the biosphere. Such transitions are evidenced in various proxy records covering different timescales. The goal is then to identify, date, and rank past critical transitions in terms of importance, thus possibly yielding a more thorough perspective on climatic history. To illustrate such an angle, which inspired the punctuated equilibrium angle on the theory of evolution, we have analyzed 2 key high-resolution datasets: the CENOGRID marine compilation (past 66 Myr), and North Atlantic U1308 record (past 3.3 Myr). By combining recurrence analysis of the individual time series with a multivariate representation of the system based on the theory of the quasi-potential, we identify the key abrupt transitions associated with major regime changes that differentiate various clusters of climate variability. This allows interpreting the time-evolution of the system as a trajectory taking place in a dynamical landscape, whose multiscale features are associated with a hierarchy of tipping points.Comment: 27 pages, 5 figures plus supplementary materia

Mineral magnetic characterization of the Upper Pleniglacial Nussloch loess sequence (Germany): an insight into local environmental processes

International audience(1) First comprehensive environmental magnetism study of the Nussloch (Rhine River Valley, Germany) loess/palaeosol deposit. (2) Bulk ferrimagnetic concentration parameters are dominantly controlled by variations in coarse-grained MD ferrimagnetic particles of detrital aeolian origin. (3) The imprint of waterlogging-induced redoxomorphic processes on the magnetic record is observed by dissolution of fine-grained magnetic minerals. (4) The interpretation of magnetic susceptibility variations alone within loess and palaeosol deposits following the wind-vigour or pedogenic enhancement models will be hindered by waterlogging-induced redoxomorphic processes, if present. S U M M A R Y Presently, most loess/palaeosol magnetic susceptibility records are interpreted as following either the wind-vigour model or the pedogenic enhancement model. However redoxomorphic processes induced by waterlogging, often referred to gleying in the loess literature, are also known to alter loess deposits but their impact on loess/palaeosol magnetic susceptibility records has received little attention. The reported rock magnetic study aims to characterize the mineral magnetic response of loess to waterlogging-induced redoxomorphic processes, thus improving our understanding of mineral magnetic changes within loess deposits with respect to environmental and climate conditions. The Nussloch loess-palaeosol deposit (Rhine Valley, Germany) was targeted because it is one of the best-studied Pleniglacial deposits for Western Europe in which numerous tundra gley intervals have been identified. Moreover, a comprehensive high-resolution environmental magnetism study has never been undertaken for this site. Various rock magnetism experiments were conducted at both room and low temperatures to characterise the composition, concentration and relative magnetic grain size of the mineral magnetic assemblage. The relative changes in magnetic parameters within the investigated loess interval are primarily controlled by (1) varying concentrations of coarse-grained ferri-magnetic particles of detrital (aeolian) origin and (2) dissolution of fine-grained ferrimagnetic particles related to in situ post-depositional alteration promoted by waterlogging-induced re-doxomorphic processes. Goethite is found to be ubiquitous throughout the studied interval and is argued to have both a primary (aeolian) and secondary (in situ) origin. We conclude, that redoxomorphic processes induced by waterlogging, if present, will hinder the interpretation of magnetic susceptibility variations within loess and palaeosol deposits following the expected relationships dictated by the wind-vigour and the pedogenic enhancement magnetism models