26 research outputs found
Three monthly coral Sr/Ca records from the Chagos Archipelago covering the period of 1950-1995 A.D.: reproducibility and implications for quantitative reconstructions of sea surface temperature variations
In order to assess the fidelity of coral Sr/Ca for quantitative reconstructions of sea surface temperature variations, we have generated three monthly Sr/Ca time series from Porites corals from the lagoon of Peros Banhos (71°E, 5°S, Chagos Archipelago). We find that all three coral Sr/Ca time series are well correlated with instrumental records of sea surface temperature (SST) and air temperature. However, the intrinsic variance of the single-core Sr/Ca time series differs from core to core, limiting their use for quantitative estimates of past temperature variations. Averaging the single-core data improves the correlation with instrumental temperature (r > 0.7) and allows accurate estimates of interannual temperature variations (~0.35°C or better). All Sr/Ca time series indicate a shift towards warmer temperatures in the mid-1970s, which coincides with the most recent regime shift in the Pacific Ocean. However, the magnitude of the warming inferred from coral Sr/Ca differs from core to core and ranges from 0.26 to 0.75°C. The composite Sr/Ca record from Peros Banhos clearly captures the major climatic signals in the Indo-Pacific Ocean, i.e. the El Niño–southern oscillation and the Pacific decadal oscillation. Moreover, composite Sr/Ca is highly correlated with tropical mean temperatures (r = 0.7), suggesting that coral Sr/Ca time series from the tropical Indian Ocean will contribute to multi-proxy reconstructions of tropical mean temperatures
SIMULISP : un banc d'essai de systèmes experts pour la commande des ateliers de production
ks Dates de conférence : janvier 1985 1985.International audienc
An expert system approach to industrial job-shop scheduling
ksInternational audienceThe first part of this paper is devoted to the presentation of a software system for jobshop scheduling of batches under due date constraints and time-table constraints on work-stations. It is based on a heuristic technique for sequencing the jobs. It is actually run in a real workshop. The second part of the parper deals with an expert system methodology currently under development for the same kind of problems. The idea is to be able to integrate two kinds of knowledge about the production process : theoretical knowledge (issued from scheduling theory) which achieves the management of time, and practical knowledge (provided by the shop-floor manager) about specific technological constraints which must be satisfied by the actual production process. These constraints are usually not taken into account at the theoretical level. The knowledge representation and processing techniques of Artificial Intelligence enable realistic schedules to be obtained by simultaneous use of both sources of information
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A Fiji multi-coral δ18O composite approach to obtaining a more accurate reconstruction of the last two centuries of the ocean-climate variability in the South Pacific Convergence Zone region
The limited availability of oceanographic data in the tropical Pacific Ocean prior to the satellite era makes coral-based climate reconstructions a key tool for extending the instrumental record back in time, thereby providing a much needed test for climate models and projections. We have generated a unique regional network consisting of five Porites coral δ18O time series from different locations in the Fijian archipelago. Our results indicate that using a minimum of three Porites coral δ18O records from Fiji is statistically sufficient to obtain a reliable signal for climate reconstruction, and that application of an approach used in tree ring studies is a suitable tool to determine this number. The coral δ18O composite indicates that while sea surface temperature (SST) variability is the primary driver of seasonal δ18O variability in these Fiji corals, annual average coral δ18O is more closely correlated to sea surface salinity (SSS) as previously reported. Our results highlight the importance of water mass advection in controlling Fiji coral δ18O and salinity variability at interannual and decadal time scales despite being located in the heavy rainfall region of the South Pacific Convergence Zone (SPCZ). The Fiji δ18O composite presents a secular freshening and warming trend since the 1850s coupled with changes in both interannual (IA) and decadal/interdecadal (D/I) variance. The changes in IA and D/I variance suggest a re-organization of climatic variability in the SPCZ region beginning in the late 1800s to period of a more dominant interannual variability, which could correspond to a southeast expansion of the SPCZ
A Fiji multi-coral delta O-18 composite approach to obtaining a more accurate reconstruction of the last two-centuries of the ocean-climate variability in the South Pacific Convergence Zone region
The limited availability of oceanographic data in the tropical Pacific Ocean prior to the satellite era makes coral-based climate reconstructions a key tool for extending the instrumental record back in time, thereby providing a much needed test for climate models and projections. We have generated a unique regional network consisting of five Porites coral O-18 time series from different locations in the Fijian archipelago. Our results indicate that using a minimum of three Porites coral O-18 records from Fiji is statistically sufficient to obtain a reliable signal for climate reconstruction, and that application of an approach used in tree ring studies is a suitable tool to determine this number. The coral O-18 composite indicates that while sea surface temperature (SST) variability is the primary driver of seasonal O-18 variability in these Fiji corals, annual average coral O-18 is more closely correlated to sea surface salinity (SSS) as previously reported. Our results highlight the importance of water mass advection in controlling Fiji coral O-18 and salinity variability at interannual and decadal time scales despite being located in the heavy rainfall region of the South Pacific Convergence Zone (SPCZ). The Fiji O-18 composite presents a secular freshening and warming trend since the 1850s coupled with changes in both interannual (IA) and decadal/interdecadal (D/I) variance. The changes in IA and D/I variance suggest a re-organization of climatic variability in the SPCZ region beginning in the late 1800s to period of a more dominant interannual variability, which could correspond to a southeast expansion of the SPCZ
Les rapports Mg/Ca et Sr/Ca des coraux profonds (Lophelia pertusa) : distribution en fonction des moicrostructures coralliennes et potentialité d'un thermomètre chimique des eaux de sub-surfaces et intermédiaires
Global warming in an independent record of the past 130 years
The thermometer-based global surface temperature time series (GST) commands a prominent role in the evidence for global warming, yet this record has considerable uncertainty. An independent record with better geographic coverage would be valuable in understanding recent change in the context of natural variability. We compiled the Paleo Index (PI) from 173 temperature-sensitive proxy time series (corals, ice cores, speleothems, lake and ocean sediments, historical documents). Each series was normalized to produce index values of change relative to a 1901–2000 base period; the index values were then averaged. From 1880 to 1995, the index trends significantly upward, similar to the GST. Smaller-scale aspects of the GST including two warming trends and a warm interval during the 1940s are also observed in the PI. The PI extends to 1730 with 67 records. The upward trend appears to begin in the early 19th century but the year-to-year variability is large and the 1730–1929 trend is small
Buffet and buffeting control in transonic flow
Communication to : ODAS 2003 Toulouse (France), June 04-06, 2003Available from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.2003 n.74 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc
Les rapports Mg/Ca et Sr/Ca des coraux profonds (Lophelia pertusa) : distribution en fonction des moicrostructures coralliennes et potentialité d'un thermomètre chimique des eaux de sub-surfaces et intermédiaires
Integration of ice-core, marine and terrestrial records for the Australian Last Glacial Maximum and Termination: a contribution from the OZ INTIMATE group
The degree to which Southern Hemisphere climatic changes during the end of the last glacial period and early Holocene (30-8 ka) were influenced or initiated by events occurring in the high latitudes of the Northern Hemisphere is a complex issue. There is conflicting evidence for the degree of hemispheric 'teleconnection' and an unresolved debate as to the principle forcing mechanism(s). The available hypotheses are difficult to test robustly, however, because the few detailed palaeoclimatic records in the Southern Hemisphere are widely dispersed and lack duplication. Here we present climatic and environmental reconstructions from across Australia, a key region of the Southern Hemisphere because of the range of environments it covers and the potentially important role regional atmospheric and oceanic controls play in global climate change. We identify a general scheme of events for the end of the last glacial period and early Holocene but a detailed reconstruction proved problematic. Significant progress in climate quantification and geochronological control is now urgently required to robustly investigate change through this period. Copyright (c) 2006 John Wiley & Sons, Ltd