Anatomy of a Dansgaard-Oeschger warming transition: High-resolution analysis of the North Greenland Ice Core Project ice core

Large and abrupt temperature oscillations during the last glacial period, known as Dansgaard‐Oeschger (DO) events, are clearly observed in the Greenland ice core record. Here we present a new high‐resolution chemical (2 mm) and stable isotope (20 mm) record from the North Greenland Ice Core Project (NGRIP) ice core at the onset of one of the most prominent DO events of the last glacial, DO‐8, observed ∼38,000 years ago. The unique, subannual‐resolution NGRIP record provides a true sequence of change during a DO warming with detailed annual layer counting of very high depth resolution geochemical measurements used to determine the exact duration of the transition. The continental ions, indicative of long‐range atmospheric loading and dustiness from East Asia, are the first to change, followed by the snow accumulation, the moisture source conditions, and finally the atmospheric temperature in Greenland. The sequence of events shows that atmospheric and oceanic source and circulation changes preceded the DO warming by several years

Exploring contested authenticity among speakers of a contested language: the case of ‘Francoprovençal'

This paper explores the notion of speaker authenticity in the context of obsolescent ‘Francoprovençal’: a highly fragmented grouping of Romance varieties spoken in parts of France, Italy, and Switzerland by less than 1% of the total regional population. While Francoprovençal has long been losing ground to the dominant language(s) with which it is in contact, new speakers have begun to emerge within the context of revitalisation movements and activities geared more favourable language planning policies and increased literacy. The emergence of these new speakers has polarised native-speaker communities, and has blurred the lines associated with the traditional view of sociolinguistic authenticity. Through an analysis of qualitative data collected in 2012, this article argues in particular that it may not be sufficient to simply examine contested authenticities from a native–non-native perspective, but rather it is important to consider how new speakers might themselves form a complex spectrum of speaker types with new sets of tensions as has been argued elsewhere

Glacial-interglacial modulation of the marine nitrogen cycle by high-latitude O2 supply to the global thermocline

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA4007, doi:10.1029/2003PA001000.An analysis of sedimentary nitrogen isotope records compiled from widely distributed marine environments emphasizes the global synchrony of denitrification changes and provides evidence for a strong temporal coupling of these variations to changes in nitrogen fixation as previously inferred. We explain the global coherence of these records by a simple physical control on the flux of dissolved oxygen to suboxic zones and the coupling to fixation via the supply of phosphorus to diazotrophs in suitable environments. According to our hypothesis, lower glacial-stage sea surface temperature increased oxygen solubility, while stronger winds in high-latitude regions enhanced the rate of thermocline ventilation. The resultant colder, rapidly flushed thermocline lessened the spatial extent of denitrification and, consequently, N fixation. During warm periods, sluggish circulation of warmer, less oxygen rich thermocline waters caused expansion of denitrification zones and a concomitant increase in N fixation. Local fluctuations in export productivity would have modulated this global signal.Financial support for this work was provided by the Natural Sciences and Engineering Research Council of Canada and by a WHOI postdoctoral fellowship to MK

Transitions dans le parcours de vie et construction des inégalités

Tout au long de leur existence, les individus suivent des chemins singuliers dont les trajectoires ne sont pas le simple fait de la seule volonté ou du hasard. Ces cheminements se révèlent souvent générateurs d'inégalités entre individus, notamment au cours des transitions des âges de la vie (enfance, adolescence, âge adulte, grand âge), ou lors de différentes étapes (mariage, divorce, deuil, etc). C'est afin de mieux comprendre les modalités et les combinaisons d'influence à l'origine des inégalités dans les parcours de vie, que les éditeurs de cet ouvrage ont réuni des chercheurs issus des sciences psychologiques, sociales et économiques, afin de croiser leurs regards sur la manière dont ces inégalités se creusent ou se réduisent au fil des trajectoires. Cet ouvrage interdisciplinaire met en relief la richesse d'une approche des inégalités dans la perspective dynamique du parcours de vie.Peer reviewe

The EPICA deep ice cores: first results and perspectives

Two deep ice cores are being drilled in Antarctica in the frame of the European Project for Ice Coring in Antarctica (EPICA). The Dome C ice core will provide more information about mechanisms of global climatic changes over several climatic cycles. The DML core, drilled at Kohnen station, will provide a detailed record over the last climatic cycle, which can be compared with Greenland records. The drilling at Dome C reached 3200 m depth during field season 2002/03, and the age of the ice at the bottom of the hole could be 900 000 years according to preliminary estimates. The depth at Kohnen station is 1564.6 m at present, corresponding to an age of about 55 000 years. Analyses along the top parts of both ice cores have provided interesting first results. A few selected results from these parts, mostly published already, are summarized. Only a few measurements are available from the deeper parts of both cores. Dielectric profiling and electrical conductivity measurements, performed in the field, provide continuous and high-resolution records concerning the acidity and the salt concentration of the ice. Continuous flow analyses and Fast Ion Chromatography also provide high-resolution records of several chemical compounds. These records give some clues as to the age scale of the EPICA Dome C ice core, but they also leave us with many open questions

High-resolution Holocene N2O ice core record and its relationship with CH4 and CO2

Nitrous oxide (N2O) concentration records exist for the last 1000 years and for time periods of rapid climatic changes like the transition from the last glacial to today's interglacial and for one of the fast climate variations during the last ice age. Little is known, however, about possible N2O variations during the more stable climate of the present interglacial (Holocene) spanning the last 11 thousand years. Here we fill this gap with a high-resolution N2O record measured along the European Project for Ice Coring in Antarctica (EPICA) Dome C Antarctic ice core. On the same ice we obtained high-resolution methane and carbon dioxide records. This provides the unique opportunity to compare variations of the three most important greenhouse gases (after water vapor) without any uncertainty in their relative timing. The CO2 and CH4 records are in good agreement with previous measurements on other ice cores. The N2O concentration started to decrease in the early Holocene and reached minimum values around 8 ka (<260 ppbv) before a slow increase to its preindustrial concentration of ∼265 ppbv

Evidence for substantial accumulation rate variability in Antarctica during the Holocene through synchronization of CO2 in the Taylor Dome , Dome C and DML ice cores

High resolution records of atmospheric CO2 concentration during the Holocene are obtained from the Dome Concordia and Dronning Maud Land (Antarctica) ice cores. These records confirm that the CO2 concentration varied between 260 and 280 ppmv in the Holocene as measured in the Taylor Dome ice core. However, there are differences in the CO2 records most likely caused by mismatches in timescales. Matching the Taylor Dome timescale to the Dome C timescale by synchronization of CO2 indicates that the accumulation rate at Taylor Dome increased through the Holocene by a factor two and bears little resemblance to the stable isotope record used as a proxy for temperature. This result shows that different locations experienced substantially different accumulation changes, and casts doubt on the often-used assumption that accumulation rate scales with the saturation vapor pressure as a function of temperature, at least for coastal locations