Capture, representation, and "composition" of the instrumental gesture

International audienceIn designing and constructing a computer tool for musical creation, the instrumental gesture is especially relevant for real time control of the sound synthesis processes by simulation of instrumental mechanisms. This study is based on the implementation of a complete system to enable the capture and memorisation of the instrumental gesture during play, i.e. when instrumentalist/instrument relationship is established

Heinrich event 1: an example of dynamical ice-sheet reaction to oceanic changes

Heinrich events, identified as enhanced ice-rafted detritus (IRD) in North Atlantic deep sea sediments (Heinrich, 1988; Hemming, 2004) have classically been attributed to Laurentide ice-sheet (LIS) instabilities (MacAyeal, 1993; Calov et al., 2002; Hulbe et al., 2004) and assumed to lead to important disruptions of the Atlantic meridional overturning circulation (AMOC) and North Atlantic deep water (NADW) formation. However, recent paleoclimate data have revealed that most of these events probably occurred after the AMOC had already slowed down or/and NADW largely collapsed, within about a thousand years (Hall et al., 2006; Hemming, 2004; Jonkers et al., 2010; Roche et al., 2004), implying that the initial AMOC reduction could not have been caused by the Heinrich events themselves. Here we propose an alternative driving mechanism, specifically for Heinrich event 1 (H1; 18 to 15 ka BP), by which North Atlantic ocean circulation changes are found to have strong impacts on LIS dynamics. By combining simulations with a coupled climate model and a three-dimensional ice sheet model, our study illustrates how reduced NADW and AMOC weakening lead to a subsurface warming in the Nordic and Labrador Seas resulting in rapid melting of the Hudson Strait and Labrador ice shelves. Lack of buttressing by the ice shelves implies a substantial ice-stream acceleration, enhanced ice-discharge and sea level rise, with peak values 500–1500 yr after the initial AMOC reduction. Our scenario modifies the previous paradigm of H1 by solving the paradox of its occurrence during a cold surface period, and highlights the importance of taking into account the effects of oceanic circulation on ice-sheets dynamics in order to elucidate the triggering mechanism of Heinrich events.Peer reviewe

Orbitally forced ice sheet fluctuations during the Marinoan Snowball Earth glaciation

Two global glaciations occurred during the Neoproterozoic. Snowball Earth theory posits that these were terminated after millions of years of frigidity when initial warming from rising atmospheric CO2 concentrations was amplified by the reduction of ice cover and hence a reduction in planetary albedo. This scenario implies that most of the geological record of ice cover was deposited in a brief period of melt-back. However, deposits in low palaeo-latitudes show evidence of glacial–interglacial cycles. Here we analyse the sedimentology and oxygen and sulphur isotopic signatures of Marinoan Snowball glaciation deposits from Svalbard, in the Norwegian High Arctic. The deposits preserve a record of oscillations in glacier extent and hydrologic conditions under uniformly high atmospheric CO2 concentrations. We use simulations from a coupled three-dimensional ice sheet and atmospheric general circulation model to show that such oscillations can be explained by orbital forcing in the late stages of a Snowball glaciation. The simulations suggest that while atmospheric CO2 concentrations were rising, but not yet at the threshold required for complete melt-back, the ice sheets would have been sensitive to orbital forcing. We conclude that a similar dynamic can potentially explain the complex successions observed at other localities

Analyse, représentation et traitement du geste instrumental : application aux instruments à clavier

This thesis is part of the design and achievement of a computer tool for musical creation. It deals with the question of instrumental gesture in order to control in real time sound synthesis processes by means of simulating instrumental mechanisms, and to study its relation with musical composition. We pose the problem of segmentation to describe and classify the instrumental gesture, assimilated as a sequence of gestural events, received and memorized in form of sampled signals. We consider the play with keyboard instrument, we propose elements of a gestural syntax, and deduce criteria for an automatic segmentation. Then we take interest to the graphical representation of the segmented gestural events, and to their transformation and composition. We define several levels of representation and, for each level, manual processing procedures or compositional models procedures, in full or in part. The gesture editor, integrated in the sound synthesis system CORDIS-ANIMA, combines all these possibilities.Dans le cadre de la conception et de la réalisation d'un outil informatique pour la création musicale, on s'intéresse au geste instrumental pour contrôler en temps réel des processus de synthèse sonore par simulation de mécanismes instrumentaux et pour étudier sa relation à la composition musicale. Pour décrire et classifier le geste instrumental, assimilé à une séquence d'événements gestuels, capté et mémorisé sous la forme de signaux échantillonnés, nous posons le probleme de la segmentation. En considérant le jeu instrumental sur clavier, nous proposons des éléments de syntaxe gestuelle et en déduisons des critères pour la segmentation automatique. Nous nous intéressons ensuite à la représentation graphique des événements gestuels segmentés et a leur composition et transformation. Nous définissons plusieurs niveaux de représentation et, pour chacun d'eux, des procédures de traitement manuel ou pris en charge, tout ou en partie, par des modèles de composition. L'éditeur de geste, intégré dans le système de synthèse sonore CORDIS-ANIMA, synthétise l'ensemble de ces possibilités

Investigation of the Impact of a Heinrich-Event-like Abrupt Event Superimposed Onto the RCP 8.5 Scenario

International audienceThe CMIP5/IPCC (AR5) projections of climate change showed the temperatures should increase by between 1.3 °C and 4.4 °C by 2100 and the sea level rise between 26 cm and 82 cm on average. Superimposed on these climatic and hydrologic trends associated with the RCP 8.5 most pessimistic scenario, it is important to investigate the possible effect of an abrupt event like an ice-sheet surge. This is first justified by the recent collapse of the Larsen B ice shelf which illustrates that a non-linear response of the cryosphere may occur in a warming world. Furthermore, in glacial periods, ice-sheets have been unstable and huge surges of icebergs did occur and deeply modified the climate. The aim of this presentation is to show the hypothetical climatic consequences of such a Heinrich-type event on future climate change. To achieve this goal, 3 scenarios of rapid ice-sheet deglaciation have been designed, corresponding to an additional sea level rise of around 3 m : - S1 corresponds to a contribution from Greenland only; - S2 from West-Antarctica only; - S3 from both ice-sheets. We use the global atmosphere-ocean general circulation model (OAGCM) IPSL-CM5A-LR. The freshwater perturbation is applied near the ice-sheet(s) during 20 years from 2050 to 2070 during an RCP8.5 perturbation. The RCP8.5 scenario is then continued until 2100 (without freshwater). For these types of scenarios, previous experiments for paleoclimatic cases help us diagnose the most vulnerable areas. The North Atlantic and the collapse of thermohaline circulation is one key issue, but far field teleconnections with the Asian monsoon will also be explored. We will investigate the timing and amplitude of the climate impacts due to the perturbations, which may be quite different in our 3 scenarios. These abrupt events consequences can be important for the populations and the consideration of rapid changes should improve the reliability of IPCC predictions

Analyse, representation et traitement du geste instrumental

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 80770 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Evolution of the Antarctic ice sheet throughout the last deglaciation: A study with a new coupled climate—north and south hemisphere ice sheet model

International audienceThe aim of this paper is to assess, through the understanding of deglaciation processes, the contribution of the Antarctic ice sheet to sea-level rise during the last deglaciation. To achieve this goal, we use an Earth System model in which the interactions between the atmosphere, the ocean, the vegetation and the northern and Antarctic ice sheets are represented. This new tool allows the simulation of the evolution of the Antarctic ice volume, which starts to decrease at around 15 ka. At the end of deglaciation, the melting of the Antarctic ice sheet contributes to an ice-equivalent sea-level rise of 9.5 m in the standard experiment and 17.5 m in a more realistic sensitivity experiment accounting for a different bathymetry in the Weddell Sea which succeeds in producing both major ice shelves (Ross and Ronne-Filchner). In both experiments, the melting of all ice sheets contributes to 121.5 m and 129.5 m, respectively, which is very consistent with data. The new coupled model provides a timing and amplitude of the Antarctic deglaciation different from those previously obtained by prescribing the temperature record from the Vostok Antarctic ice core (78°27′S 106°52′E) as a uniform temperature forcing. Sensitivity experiments have also been performed to analyse the impact of the parameters at the origin of the deglaciation process: insolation changes, atmospheric CO2 variation, basal melting and sea-level rise. All those parameters have an influence on the timing of the deglaciation. The prescribed global sea level rise is shown to be a major forcing factor for the evolution of the Antarctic ice volume during the last deglaciation. We quantify the direct effect of the sea-level rise due to the northern hemisphere ice sheet melting on the grounding line retreat which, in turn, favours enhancement of grounded ice flow by lowering the buttressing effect of ice shelves

Modelling a Modern-like-pCO 2 Warm Period (MIS KM5c) with Two Versions of IPSL AOGCM

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Dynamic Greenland ice sheet driven by pCO2 variations across the Pliocene Pleistocene transition

International audienceIt is generally considered that the perennial glaciation of Greenland lasting several orbital cycles began around 2.7 Ma along with the intensification of Northern Hemisphere glaciation (NHG). Both data and model studies have demonstrated that a decline in atmospheric pCO2 was instrumental in establishing a perennial Greenland ice sheet (GrIS), yet models have generally used simplistic pCO2 constraints rather than data-inferred pCO2 evolution. Here, using a method designed for the long-term coupling of climate and cryosphere models and pCO2 scenarios from different studies, we highlight the pivotal role of pCO2 on the GrIS expansion across the Plio-Pleistocene Transition (PPT, 3.0–2.5 Ma), in particular in the range between 280 and 320 ppm. Good qualitative agreement is obtained between various IRD reconstructions and some of the possible evolutions of the GrIS simulated by our model. Our results underline the dynamism of the GrIS waxing and waning under pCO2 levels similar to or lower than today, which supports recent evidence of a dynamic GrIS during the Plio-Pleistocene