Reconciling two alternative mechanisms behind bi-decadal variability in the North Atlantic
Understanding the preferential timescales of variability in the North Atlantic, usually associated with the Atlantic meridional overturning circulation (AMOC), is essential for the prospects for decadal prediction. However, the wide variety of mechanisms proposed from the analysis of climate simulations, potentially dependent on the models themselves, has stimulated the debate of which processes take place in reality. One mechanism receiving increasing attention, identified both in idealized models and observations, is a westward propagation of subsurface buoyancy anomalies that impact the AMOC through a basin-scale intensification of the zonal density gradient, enhancing the northward transport via thermal wind balance. In this study, we revisit a control simulation from the Institut Pierre-Simon Laplace Coupled Model 5A (IPSL-CM5A), characterized by a strong AMOC periodicity at 20 years, previously explained by an upper ocean–atmosphere–sea ice coupled mode driving convection activity south of Iceland. Our study shows that this mechanism interacts constructively with the basin-wide propagation in the subsurface. This constructive feedback may explain why bi-decadal variability is so intense in this coupled model as compared to others.
(Progress in Oceanography. vol. 137, n° 0079-6611, pp. 237–249, 01/09/2015)
LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PARVATI, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, OCCR, UNIBE, NOC, UOR
The sedimentary record of the 1960 tsunami in two coastal lakes on Isla de Chiloé, south central Chile
This study describes sediments deposited by the tsunami following the 1960 Great Chilean Earthquake (MW 9.5) in two coastal lakes, Lakes Cucao and Huelde, on thewest coast of Isla de Chiloé, south central Chile (42.6°S). Subbottom profiles and side scan sonar mosaics illustrate the sedimentary context of transects of gravity cores. The stratigraphy of both lakes features gyttja sedimentation, interrupted by the abrupt emplacement of a sandy layer with mud rip-up clasts and a mud cap. This sandy layer reflects a sudden change in sedimentary environment, most probably caused by a high-energy inundation. Radionuclide analyses (137Cs and 210Pb) date the inundation deposit to shortly before the mid 1960s. The only known event that matches the sedimentological and chronological criteria is the AD 1960 tsunami. Using grain size analysis and comparisonswith samples frommodern environments, we demonstrate that the proximal (seaward) part of the deposit consists of a mixture of sand derived from subaerial sources and reworked gyttja lake sediment. In the distal (landward) part of Lake Cucao, the sand component is lost and the deposit consists entirely of remobilised lake sediments. The repetition of tsunami deposit sequences in Lake Huelde suggests a minimumof three inundatingwaves. Sub-bottom profiles and side scan sonar mosaics reveal tsunami inundation over the barrier and more prominently through the outlet river channel. The dominant role of the river channel as a pathway for sediment transport is also described in core samples by tsunami deposits that fine away from the channel mouth. The identification and description of the deposit left by a known tsunami provide important insights into tsunami sedimentation in coastal lakes and have the potential to help in the search for paleotsunami evidence.
(Sedimentary Geology. vol. 328, n° 0037-0738, pp. 73-86, 30/08/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Reply to 'Sources of uncertainties in cod distribution models
Ingvaldsen et al.1 comment on our study assessing global fish interchanges between the North Atlantic and Pacific oceans for more than 500 species during the entire twenty-first century2. They propose that discrepancies between our model projections and observed data for cod in the Barents Sea are the result of the choice of atmosphere–ocean general circulation models (AOGCMs). We address this assertion here, re-running the cod model with additional observation data from the Barents Sea1,3, and show that the lack of open-access archived data for the Barents Sea was the primary cause of local prediction mismatch. This finding highlights the importance of systematic deposit of biodiversity data in global databases.
(Nature Climate Change. vol. 5, n° 1758-678X, pp. 790-791, 21/08/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
COST action TD1407: network on technology-critical elements (NOTICE)—from environmental processes to human health threats
The current socio-economic, environmental and public health challenges that countries are facing clearly need common-defined strategies to inform and support our transition to a sustainable economy. Here, the technology-critical elements (which includes Ga, Ge, In, Te, Nb, Ta, Tl, the Platinum Group Elements and most of the rare-earth elements) are of great relevance in the development of emerging key technologies—including renewable energy, energy efficiency, electronics or the aerospace industry. In this context, the increasing use of technology-critical elements (TCEs) and associated environmental impacts (from mining to end-of-life waste products) is not restricted to a national level but covers most likely a global scale. Accordingly, the European COST Action TD1407: Network on Technology-Critical Elements (NOTICE)—from environmental processes to human health threats, has an overall objective for creating a network of scientists and practitioners interested in TCEs, from the evaluation of their environmental processes to understanding potential human health threats, with the aim of defining the current state of knowledge and gaps, proposing priority research lines/activities and acting as a platform for new collaborations and joint research projects. The Action is focused on three major scientific areas: (i) analytical chemistry, (ii) environmental biogeochemistry and (iii) human exposure and (eco)-toxicology.
(Environmental Science and Pollution Research. vol. 22, n° 0944-1344, pp. 15188–15194, 20/08/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The effects of foundation species on community assembly: a global study on alpine cushion plant communities
Foundation species can change plant community structure by modulating important ecological processes such as community assembly, yet this topic is poorly understood. In alpine systems, cushion plants commonly act as foundation species by ameliorating local conditions. Here, we analyze diversity patterns of species' assembly within cushions and in adjacent surrounding open substrates (83 sites across five continents) calculating floristic dissimilarity between replicate plots, and using linear models to analyze relationships between microhabitats and species diversity. Floristic dissimilarity did not change across biogeographic regions, but was consistently lower in the cushions than in the open microhabitat. Cushion plants appear to enable recruitment of many relatively stress-intolerant species that otherwise would not establish in these communities, yet the niche space constructed by cushion plants supports a more homogeneous composition of species than the niche space beyond the cushion's influence. As a result, cushion plants support higher α-diversity and a larger species pool, but harbor assemblies with lower ?-diversity than open microhabitats. We conclude that habitats with and without dominant foundation species can strongly differ in the processes that drive species recruitment, and thus the relationship between local and regional species diversity.
(Ecology. vol. 96, n° 0012-9658, pp. 2064-2069, 01/08/2015)
UdeC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR AMAP, Cirad, INRA, UM, CNRS, IRD [Occitanie], IRD, WSL, WSL, IEU, UZH
École doctorale des Sciences Chimiques
(24/07/2015)
École doctorale Sciences et Environnements
(24/07/2015)
Automatic spawning detection in oysters: a fault detection approach
Using measurements of valve activity in a population of bivalves under natural environmental condition (16 oysters in the Bay of Arcachon, France), an algorithm for the automatic detection of spawning period of oysters is proposed. The algorithm is based on the fault detection approach and it works through the estimation of velocity of valves movement activity, which can be obtained by calculating the time derivative of the valves distance. A summarized description on the method used for the derivative estimation is provided, followed by the associated signal processing and decision making algorithm to determine spawning from the velocity signal. A protection from false spawning detection is also considered by analyzing the synchronicity in spawning. Through this study, it is shown that spawning in a population of oysters living in their natural habitat (i.e. in the sea) can be automatically detected without any human expertise, like visual analysis.
(17/07/2015)
NON-A, Inria, CRIStAL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Pinus nigra (European black pine) as the dominant species of the last glacial pinewoods in south-western to central Iberia: a morphological study of modern and fossil pollen
AimOur aim was to discriminate different species ofPinusvia pollen analysisin order to assess the responses of particular pine species to orbital and millen-nial-scale climate changes, particularly during the last glacial period.LocationModern pollen grains were collected from current pine populationsalong transects from the Pyrenees to southern Iberia and the Balearic Islands.Fossil pine pollen was recovered from the south-western Iberian margin coreMD95-2042.MethodsWe measured a set of morphological traits of modern pollen fromthe Iberian pine speciesPinus nigra,P. sylvestris,P. halepensis,P. pineaandP. pinasterand of fossil pine pollen from selected samples of the last glacialperiod and the early to mid-Holocene. Classification and regression tree(CART) analysis was used to establish a model from the modern dataset thatdiscriminates pollen from the different pine species and allows identification offossil pine pollen at the species level.ResultsThe CART model was effective in separating pollen ofP. nigraandP. sylvestrisfrom that of the Mediterranean pine group (P. halepensis,P. pineaandP. pinaster). The pollen ofPinus nigradiverged from that ofP. sylvestrisby having a more flattened corpus. Predictions using this model suggested thatfossil pine pollen is mainly fromP. nigrain all the samples analysed.Pinus syl-vestriswas more abundant in samples from Greenland stadials than Heinrichstadials, whereas Mediterranean pines increased in samples from Greenland in-terstadials and during the early to mid-Holocene.Main conclusionsMorphological parameters can be successfully used toincrease the taxonomic resolution of fossil pine pollen at the species level forthe highland pines (P. nigraandP. sylvestris) and at the group of species levelfor the Mediterranean pines. Our study indicates thatP. nigrawas the domi-nant component of the last glacial south-western/central Iberian pinewoods,although the species composition of these woodlands varied in response toabrupt climate changes.
(Journal of Biogeography. vol. 42, n° 0305-0270, pp. 1998-2009, 08/07/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS