Evaluation of coastal perturbations: A new mathematical procedure to detect changes in the reference state of coastal systems
he pressure exerted by human activities on living systems has become so intense that it is inspiring the inception of a global network of monitoring of the biosphere and the use of robust statistical procedures to detect potential changes. Here, we propose a new multivariate non-parametric procedure, based on the Mahalanobis generalised distance and a simplification of the multiple response permutation procedure to identify rapidly changes in any natural systems. The procedure can be virtually coupled on all monitoring programmes and is not influenced by missing data, a common feature found in many ecological databases. In France, physical, chemical and biological variability of coastal waters have been monitored since 1997 by the SOMLIT Network. Applied to this data set, this technique enabled a first quantification of the impacts of human disturbance through changes in the concentration of nutrients. Our results revealed how climate may interact with anthropogenic pressure to alter coastal marine systems and suggest a synergism between nutrient enrichment, human activities and local climatic conditions. Indeed some effects of climate (e.g. insolation duration - increase in duration of daylight) may attenuate the fertility of coastal systems, while some others (e.g. precipitation) amplify the human signals.
(Ecological Indicators. vol. 11, n° 1470-160X, pp. 1290-1300, 01/09/2011)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS
The monsoon imprint during the ‘atypical’ MIS 13 as seen through north and equatorial Indian Ocean records
(Quaternary Research. vol. 76, n° 0033-5894, pp. 285-293, 01/09/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Atmospheric Chemistry of 2,3-Pentanedione: Photolysis and Reaction with OH Radicals
(Journal of Physical Chemistry A. vol. 115, n° 1089-5639, pp. 9160-9168, 25/08/2011)
CERI EE - IMT Nord Europe, IMT Nord Europe, IMT, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PC2A, CNRS
Assessment of sea surface temperature changes in the Gulf of Cadiz during the last 30 ka: implications for glacial changes in the regional hydrography
New dinocyst analyses were conducted on core MD99-2339 retrieved from the central Gulf of Cadiz. Dinocyst and foraminiferal assemblages from this core are combined with existing data off SW Portugal and NW Morocco to investigate past hydrological and primary productivity regimes in the subtropical NE Atlantic Ocean over the last 30 ka. Our results have revealed highest upwelling intensity during Heinrich Stadial 1 (HS 1) and the Younger Dryas and weaker upwelling cells during the Last Glacial Maximum (LGM) and HS 2, off the SW Iberian and NW Moroccan margins. Similar assemblages between the Gulf of Cadiz and the NW Moroccan margin, and distinct species off Portugal, were observed during the cold climatic extremes that punctuated the last 30 ka. This pattern has been linked to the occurrence of a hydrological structure between SW Iberia and Cadiz during the last glacial period, perhaps similar to the modern Azores Front. This front was probably responsible locally for heterotrophic dinocysts found in the Gulf of Cadiz during the last glacial period, even if this sector is not conductive to upwelling phenomena by Ekman transport. Regional reconstructions of paleo-sea-surface temperatures (SSTs) using dinocyst and foraminiferal transfer functions, as well as alkenones, are also discussed and depict coherent scenarios over the last 30 ka. Seasonal reconstructions of LGM SSTs obtained with this multi-proxy panel are discussed jointly with model outputs in order to contribute to ongoing efforts in model-data comparison.
(Biogeosciences. vol. 8, n° 1726-4170, pp. 2295-2316, 23/08/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Stratigraphic, sedimentological and palaeoenvironmental constraints on the rise of the Urgonian platform in the western Swiss Jura" by A. Godet et al. (2010) Sedimentology 57, 1088-1125: Discussion
(Sedimentology. vol. 59, n° 0037-0746, pp. 1121-1125, 08/08/2011)
LDO, INSU - CNRS, UBO EPE, CNRS, UNIGE, UNIMI, CR2P, MNHN, UPMC, CNRS, UniCa, SGN
Contrasting rainfall patterns over North America during the Holocene and Last Interglacial as recorded by sediments of the northern Gulf of Mexico
The comparison of geochemical and mineralogical characteristics of terrigenous sediments deposited in the northern Gulf of Mexico (GoM) during the Holocene and Last Interglacial (LIG) is used to document the impact of slight differences in insolation and ice-sheet retreat rates on moisture transfer and precipitation patterns over central North America. The records indicate distinct sedimentological signatures over the two time periods, which likely reflect a modification of the main detrital provenance during the LIG compared to the Holocene. Here we postulate that the observed differences in the terrigenous supply during the LIG relative to the Holocene reflect a northeast migration of the main precipitation belt over the Mississippi River watershed likely in response to deglaciation of the Laurentide Ice Sheet prior to the peak in boreal summer insolation and the overall greater increase in boreal summer insolation relative to the Holocene. These combined effects allowed more northward migration of the Jet Stream, Atlantic Warm Pool and Intertropical Convergence Zone than during the Holocene, which may have also forced the Bermuda High farther to the northeast of its present position, thereby pumping more moisture from the GoM and the Caribbean region into both the Upper Mississippi River and northeast Great Lakes area. Citation: Montero-Serrano, J.-C., et al. (2011), Contrasting rainfall patterns over North America during the Holocene and Last Interglacial as recorded by sediments of the northern Gulf of Mexico
(Geophysical Research Letters. vol. 38, n° 0094-8276, pp. L14709, 29/07/2011)
UNIL, LCE, CNRS, UFC, UBFC, LDO, INSU - CNRS, UBO EPE, CNRS, USF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Fluvial transport of suspended sediment and organic carbon during flood events in a large agricultural catchment in southwest France.
Water draining from a large agricultural catchment of 1 110 km2 in southwest France was sampled over an 18-month period to determine the temporal variability in suspended sediment (SS) and dissolved (DOC) and particulate organic carbon (POC) transport during flood events, with quantification of fluxes and controlling factors, and to analyze the relationships between discharge and SS, DOC and POC. A total of 15 flood events were analyzed, providing extensive data on SS, POC and DOC during floods. There was high variability in SS, POC and DOC transport during different seasonal floods, with SS varying by event from 513 to 41 750 t; POC from 12 to 748 t and DOC from 9 to 218 t. Overall, 76 and 62% of total fluxes of POC and DOC occurred within 22% of the study period. POC and DOC export from the Save catchment amounted to 3090 t and 1240 t, equivalent to 1·8 t km−2 y−1 and 0·7 t km−2 y−1, respectively. Statistical analyses showed that total precipitation, flood discharge and total water yield were the major factors controlling SS, POC and DOC transport from the catchment. The relationships between SS, POC and DOC and discharge over temporal flood events resulted in different hysteresis patterns, which were used to deduce dissolved and particulate origins. In both clockwise and anticlockwise hysteresis, POC mainly followed the same patterns as discharge and SS. The DOC-discharge relationship was mainly characterized by alternating clockwise and anticlockwise hysteresis due to dilution effects of water originating from different sources in the whole catchment.
(Hydrological Processes. vol. 25, n° 0885-6087, pp. 2365-2378, 15/07/2011)
LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
New Arabian Sea records help decipher orbital timing of Indo-Asian monsoon
A recent study suggested that Indian monsoonal proxies commonly used in the Arabian Sea, in general productivity proxies, could be impacted by changes in the Atlantic overturning rate (AMOC) throughout a control on the nutrient delivery into the euphotic zone. This oceanic mechanism could lead to a misunderstanding between the Indian summer monsoon (SM) and orbital forcing and could confuse a direct comparison with other archives derived from other monsoonal sub-systems (such as East-Asian or African records). Here we analyze three independent proxies (bromine, foraminifera assemblages and grain size) extracted from a marine sediment core (MD04-2861) covering the last 310 ka, and retrieved in the northern Arabian Sea near the Makran margin, an area influenced by summer and winter Indian monsoon. The grain size proxy deals with the regional continental climate through fluvial and eolian processes. It cannot be linked to changes in nutrient content of AMOC and present the same phase relationship (timing) than the other SM proxies. This demonstrates that the productivity signals (Bromine) in the northern Arabian Sea are mainly controlled by SM dynamics and not AMOC modulated nutrients at orbital scale changes. We thus build a multi-proxy record of SM variability (i.e. SM stack) using statistical tools (principal component analysis) further compiled on an age model constructed independently from orbital tuning. We find that strong SM lag by 9 ± 1 ka the NH summer insolation maximum (minimum of precession, June 21 perihelion and obliquity maximum) in the precession band, and by 6 ± 1.3 ka in the Obliquity band. These results are consistent with previous studies based on marine and terrestrial records in both Indian and Asian regions, except Asian speleothems. Our study supports the hypothesis that internal climate forcing (decreased ice volume together with the increase of latent heat export from the southern Indian Ocean) set the timing of strong Indo-Asian summer monsoons within both the precession and obliquity cycle. The external forcing (direct sensible heating) initiate monsoonal circulation. Strong Indian winter monsoon (WM) occurs between ice maxima and northern hemisphere sensible heat minima, indicating that both act to strengthen WM circulation. The summer and winter monsoons are in antiphase in the precession band suggesting that the two systems are dynamically linked.
(Earth and Planetary Science Letters. vol. 308, n° 0012-821X, pp. 433 - 444, 13/07/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Recent advances in Serre-Green Naghdi modelling for wave transformation, breaking and runup processes
To describe the strongly nonlinear dynamics of waves propagating in the final stages of shoaling and in the surf and swash zones, fully nonlinear models are required. The ability of the Serre or Green Naghdi (S-GN) equations to reproduce this nonlinear processes is reviewed. Two high-order methods for solving S-GN equations, based on Finite Volume approaches, are presented. The first one is based on a quasi-conservative form of the S-GN equations, and the second on a hybrid Finite Volume/Finite Difference method. We show the ability of these two approaches to accurately simulate nonlinear shoaling, breaking and runup processes.
(European Journal of Mechanics - B/Fluids, n° 0997-7546, pp. doi:10.1016/j.euromechflu.2011.02.005, 06/07/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGI, UJF, Grenoble INP, CNRS, IMT, UT Capitole, Comue de Toulouse, INSA Toulouse, INSA, Comue de Toulouse, UT2J, Comue de Toulouse, UT3, Comue de Toulouse, CNRS, PUC, DMA, ENS-PSL, PSL, CNRS, I3M, UM2, UM, CNRS
Relationship between valve activity, microalgae concentration in the water and toxin accumulation in the digestive gland of the Pacific oyster Crassostrea gigas exposed to Alexandrium minutum.
The complexity of the relationships between Alexandrium minutum (A.m.) concentration in the water ([A.m.]w), Paralytic Shellfish Poisoning contamination in the digestive gland ([PSP]dg) and valve behavior was explored in oysters Crassostrea gigas. Two experiments were conducted, during which oysters' valve behaviour were analyzed. Oysters, first acclimated for 10-days with the non harmful microalgae Heterocapsa triquetra (H.t.) were exposed to 4 microalgae mixtures at constant total concentrations of 10∙103 cells.ml-1 (experiment-1) and 5∙103 cells.ml-1 (experiment-2): 100% A.m.; 50% A.m.-50% H.t.; 25% A.m.-75% H.t.; 100% H.t. At the end of experiment-2, [PSP]dg were measured. At 10∙103 cells.ml-1, the microalgal ingestion decreased (p < 0.05) with increasing [A.m.]w but not at 5∙103 cells.ml-1 (p > 0.05). The frequency of microclosures specifically increased with [A.m.]w (p < 0.05) and the opening duration with [PSP]dg (p < 0.0001). Oysters exhibiting the maximum increase in opening duration also exhibited the highest [PSP]dg. The results are discussed in terms of oyster physiology and origin of the behavioral response.
(Marine Pollution Bulletin. vol. 62, n° 0025-326X, pp. 1191-1197, 01/07/2011)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, UEB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PHYC, DYNECO, IFREMER