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International audience; The Dansgaard-Oeschger (DO) event 25 initiates the millennial-scale climatic variability of the Northern Hemisphere during the last glacial period. This first rapid event is identified in the NorthGRIP ice core (Greenland - 75.10 °N, 42.32 °W, elevation 2917 m. a. s.l., modern accumulation rate 17.5 cm w.e.yr-1) δ18Oice record as a sharp 2.3‰ increase (half of a “classical” DO interstadial magnitude) occurring at ~112 ka (EDC3 age scale). While DO event 25 remained so far poorly studied, the other DO events of the glacial period have revealed (1) large amplitudes of temperature change over Greenland (8-16°C) (2) synchronous rapid increases of methane (CH4) and Greenland temperature (3) seesaw behaviour with Antarctic temperatures increasing slowly 300-3400 yrs before the rapid Greenland abrupt temperature changes. Thus, investigating in detail the first DO event is of primary importance to understand the onset of the climatic variability of the glacial period. To provide a complete description of DO event 25, we present new results from the EPICA Dronning Maud Land (EDML, Antarctica - 75.00 °S, 0.07 °E, 2882 m a.s.l., 6.4 cm w.e.yr1) and the NorthGRIP ice cores. We use high-resolution measurements of the isotopic composition of air nitrogen (δ15N) as a temperature proxy in the gas phase to infer the amplitude of temperature changes over Greenland. These data moreover allow determining precisely the phasing between temperature and CH4 concentration in the air trapped in the ice. Finally, the combination of new high-resolution CH4 measurements on the NorthGRIP ice core and δ18Oatm records over this first rapid event permits to propose the first accurate common timescale between EDML and NorthGRIP over DO event 25 and to discuss the bipolar seesaw pattern at the onset of the last glacial period.

Building on the account of a pattern-theory of self introduced by Shaun Gallagher, this article investigates the unique role of the narrative dimension of the self within the self-pattern. According to a pattern-theory, the self is constituted by a cluster of dimensions that interact with each other. A particular variation of this pattern constitutes a self. This article advances the argument that for selves who narrate, the narrative dimension of the self takes a special role that cuts across the other dimensions. First, the pattern-theory of self is introduced and a conceptual and ethical argument for employing a pattern-theory is developed. Second, the distinct role of the narrative dimension of the self is analysed. Through the narrative dimension of the self, we engage in self-definition, integrate and connect the other dimensions of the self, make them intelligible, and ascribe personal meaning to them. And third, the narrator type of self is characterized. Organizing one’s experiences through a self-narrative changes the self. Narrators constitute a unified self, they can actively plan and lead a life and engage in forensic practices, and they integrate the subjective and objective nature of the self.

Novel and emerging technologies can provide users with new kinds and unprecedented amounts of information about themselves, such as autobiographical information, neurodata, health information, or characteristics inferred from online behavior. Technology providing extensive personal information (PI technology) can impact who we take ourselves to be, how we constitute ourselves, and indeed who we are. This paper analyzes how the external, quantified perspective on us offered by PI technology affects identity based on a narrative identity theory. Disclosing the intimate relationship between PI technology and identity sheds light on a whole new range of ethical issues that have so far not received sufficient attention. Personal information provided by technology is not just information that belongs to individuals but that changes them.

24 European annually resolved stable isotope chronologies have been constructed from tree ring cellulose for the last 400 years (1600CE – 2003CE) for carbon and oxygen and for the last 100 years for hydrogen. Data was produced within the ISONET project (400 Years of Annual Reconstructions of European Climate Variability Using a Highly Resolved Isotopic Network,) to initiate an extensive spatiotemporal tree-ring stable isotope network across Europe funded as part of the fifth EC Framework Programme “Energy, Environment and Sustainable Development”. This data set comprises the ISONET δ13C records.

24 European annually resolved stable isotope chronologies have been constructed from tree ring cellulose for the last 400 years (1600CE – 2003CE) for carbon and oxygen and for the last 100 years for hydrogen. Data was produced within the ISONET project (400 Years of Annual Reconstructions of European Climate Variability Using a Highly Resolved Isotopic Network,) to initiate an extensive spatiotemporal tree-ring stable isotope network across Europe funded as part of the fifth EC Framework Programme “Energy, Environment and Sustainable Development”. This data set comprises the ISONET δ18O records.

This is the first Europe-wide comprehensive assessment of the climatological and physiological information recorded by hydrogen isotope ratios in tree-ring cellulose (δ2Hc) based on a unique collection of annually resolved 100-year tree-ring records of two genera (Pinus and Quercus) from 17 sites (36°N to 68°N). We observed that the high-frequency climate signals in the δ2Hc chronologies were weaker than those recorded in carbon (δ13Cc) and oxygen isotope signals (δ18Oc) but similar to the tree-ring width ones (TRW). The δ2Hc climate signal strength varied across the continent and was stronger and more consistent for Pinus than for Quercus. For both genera, years with extremely dry summer conditions caused a significant 2H-enrichment in tree-ring cellulose.\ud \ud The δ2Hc inter-annual variability was strongly site-specific, as a result of the imprinting of climate and hydrology, but also physiological mechanisms and tree growth. To differentiate between environmental and physiological signals in δ2Hc, we investigated its relationships with δ18Oc and TRW. We found significant negative relationships between δ2Hc and TRW (7 sites), and positive ones between δ2Hc and δ18Oc (10 sites). The strength of these relationships was nonlinearly related to temperature and precipitation. Mechanistic δ2Hc models performed well for both genera at continental scale simulating average values, but they failed on capturing year-to-year δ2Hc variations. Our results suggest that the information recorded by δ2Hc is significantly different from that of δ18Oc, and has a stronger physiological component independent from climate, possibly related to the use of carbohydrate reserves for growth. Advancements in the understanding of 2H-fractionations and their relationships with climate, physiology, and species-specific traits are needed to improve the modelling and interpretation accuracy of δ2Hc. Such advancements could lead to new insights into trees' carbon allocation mechanisms, and responses to abiotic and biotic stress conditions.

Past climates and environments experienced by the Saharo-Arabian desert belt are of prime importance for palaeoclimatic and palaeoanthropological research. On orbital timescales transformations of the desert into a savannah-like landscape in response to higher precipitation provided “windows of opportunity” for hominin dispersal from Africa into Eurasia. On long timescales, palaeoenvironmental reconstructions for the region are predominantly derived from marine sediments and available terrestrial records from the Arabian Peninsula are limited to 450 ka before present (BP). Here, we present a new stalagmite-based palaeoclimate record from Mukalla Cave in Yemen which extends back to ~1.1 million years BP or Marine Isotope Stage (MIS) 31, as determined by Uranium-lead dating. Stalagmite Y99 grew only during peak interglacial periods and warm substages back to ~1.1 Ma. Stalagmite calcite oxygen isotope (δ18O) values show that every past interglacial humid period was wetter than the Holocene, a period in which large lakes formed in the now arid areas of southern Arabia. Carbon isotope (δ13C) values indicate habitable savannah-like environments developed during these pluvial periods. A total of 21 pluvial periods with precipitation of more than 300 mm yr-1 occurred since ~1.1 Ma and thus numerous opportunities for hominin dispersals occurred throughout the Pleistocene. New determinations of hydrogen (δDFI) and oxygen (δ18OFI) isotopes in stalagmite fluid inclusion water demonstrates that enhanced precipitation in Southern Arabia was brought by the African and Indian Summer Monsoons. When combined with sub-annual calcite analysis of δ18O and δ13C, these data reveal a distinct wet (summer) and dry (winter) seasonality.

While there are no indications of mixing back to 800 000 years in the EPICA Dome C ice core record, comparison with marine sediment records shows significant differences in the timing and duration of events prior to stage 11 (~430 ka, thousands of years before 1950). A relationship between the isotopic composition of atmospheric oxygen (δ18O of O2, noted δ18Oatm) and daily northern hemisphere summer insolation has been observed for the youngest four climate cycles. Here we use this relationship with new δ18O of O2 measurements to show that anomalous flow in the bottom 500 m of the core distorts the duration of events by up to a factor of 2. By tuning δ18Oatm to orbital precession we derive a corrected thinning function and present a revised age scale for the interval corresponding to Marine Isotope Stages 11–20 in the EPICA Dome C ice core. Uncertainty in the phasing of δ18Oatm with respect to insolation variations in the precession band limits the accuracy of this new agescale to ±6 kyr (thousand of years). The previously reported ~30 kyr duration of interglacial stage 11 is unchanged. In contrast, the duration of stage 15.1 is reduced by a factor of 2, from 31 to 16 kyr.

Isotope labelling is a powerful tool to study elemental cycling within terrestrial ecosystems. Here we describe a new multi-isotope technique to label organic matter (OM). We exposed poplars (Populus deltoides × nigra) for 14 days to an atmosphere enriched in 13CO2 and depleted in 2H218O. After 1 week, the water-soluble leaf OM (δ13C = 1346 ± 162‰) and the leaf water were strongly labelled (δ18O = −63 ± 8, δ2H = −156 ± 15‰). The leaf water isotopic composition was between the atmospheric and stem water, indicating a considerable back-diffusion of vapour into the leaves (58–69%) in the opposite direction to the net transpiration flow. The atomic ratios of the labels recovered (18O/13C, 2H/13C) were 2–4 times higher in leaves than in the stems and roots. This could be an indication of the synthesis of more condensed compounds in roots and stems (e.g. lignin vs. cellulose) or might be the result of O and H exchange and fractionation processes during phloem transport and biosynthesis. We demonstrate that the three major OM elements (C, O, H) can be labelled and traced simultaneously within the plant. This approach could be of interdisciplinary interest in the fields of plant physiology, palaeoclimatic reconstruction or soil science.

© 2017, National Academy of Sciences. All rights reserved. Photosynthetic organisms use various photoprotective mechanisms to dissipate excess photoexcitation as heat in a process called nonphotochemical quenching (NPQ). Regulation of NPQ allows for a rapid response to changes in light intensity and in vascular plants, is primarily triggered by a pH gradient across the thylakoid membrane (ΔpH). The response is mediated by the PsbS protein and various xanthophylls. Time-correlated single-photon counting (TCSPC) measurements were performed on Arabidopsis thaliana to quantify the dependence of the response of NPQ to changes in light intensity on the presence and accumulation of zeaxanthin and lutein. Measurements were performed on WT and mutant plants deficient in one or both of the xanthophylls as well as a transgenic line that accumulates lutein via an engineered lutein epoxide cycle. Changes in the response of NPQ to light acclimation in WT and mutant plants were observed between two successive light acclimation cycles, suggesting that the character of the rapid and reversible response of NPQ in fully dark-acclimated plants is substantially different from in conditions plants are likely to experience caused by changes in light intensity during daylight. Mathematical models of the response of zeaxanthin- and lutein-dependent reversible NPQ were constructed that accurately describe the observed differences between the light acclimation periods. Finally, the WT response of NPQ was reconstructed from isolated components present in mutant plants with a single common scaling factor, which enabled deconvolution of the relative contributions of zeaxanthin- and lutein-dependent NPQ.

Correct estimation of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice core studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: outputs of a firn densification model, and measurements of δ15N of N2 in air trapped in ice core, assuming that δ15N is only affected by gravitational fractionation in the firn column. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi-coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available ice core air-δ15N measurements from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rates and temperature conditions. Our δ15N profiles reveal a heterogeneous response of the firn structure to glacial–interglacial climatic changes. While firn densification simulations correctly predict TALDICE δ15N variations, they systematically fail to capture the large millennial-scale δ15N variations measured at BI and the δ15N glacial levels measured at JRI and EDML – a mismatch previously reported for central East Antarctic ice cores. New constraints of the EDML gas–ice depth offset during the Laschamp event (~41 ka) and the last deglaciation do not favour the hypothesis of a large convective zone within the firn as the explanation of the glacial firn model–δ15N data mismatch for this site. While we could not conduct an in-depth study of the influence of impurities in snow for firnification from the existing datasets, our detailed comparison between the δ15N profiles and firn model simulations under different temperature and accumulation rate scenarios suggests that the role of accumulation rate may have been underestimated in the current description of firnification models.

We present results from an intercomparison program of CO2, delta(O-2/N-2) and delta(CO2)-C-13 measurements from atmospheric flask samples. Flask samples are collected on a biweekly basis at the High Altitude Research Station Jungfraujoch in Switzerland for three European laboratories: the University of Bern, Switzerland, the University of Groningen, the Netherlands and the Max Planck Institute for Biogeochemistry in Jena, Germany. Almost 4 years of measurements of CO2, delta(O-2/N-2) and delta(CO2)-C-13 are compared in this paper to assess the measurement compatibility of the three laboratories. While the average difference for the CO2 measurements between the laboratories in Bern and Jena meets the required compatibility goal as defined by the World Meteorological Organization, the standard deviation of the average differences between all laboratories is not within the required goal. However, the obtained annual trend and seasonalities are the same within their estimated uncertainties. For delta(O-2/N-2) significant differences are observed between the three laboratories. The comparison for delta(CO2)-C-13 yields the least compatible results and the required goals are not met between the three laboratories. Our study shows the importance of regular intercomparison exercises to identify potential biases between laboratories and the need to improve the quality of atmospheric measurements.

Transport of salt in the Irminger Current, the northern branch of the Atlantic Subpolar Gyre coupling the eastern and western subpolar North Atlantic, plays an important role for climate variability across a wide range of time scales. High-resolution ocean modeling and observations indicate that salinities in the eastern subpolar North Atlantic decrease with enhanced circulation of the North Atlantic subpolar gyre (SPG). This has led to the perception that a stronger SPG also transports less salt westward. In this study, we analyze a regional ocean model and a comprehensive global coupled climate model, and show that a stronger SPG transports more salt in the Irminger Current irrespective of lower salinities in its source region. The additional salt converges in the Labrador Sea and the Irminger Basin by eddy transports, increases surface salinity in the western SPG, and favors more intense deep convection. This is part of a positive feedback mechanism with potentially large implications for climate variability and predictability.