[Without Title]     

Travis Hudson  Anne-Marie de Grosbois 《Environmental Geology》2006,49(7):1081-1087

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Late Holocene paleoenvironment in northern New Caledonia, southwestern Pacific, from a multiproxy analysis of lake sediments     

Denis Wirrmann  Anne-Marie Sémah 《Quaternary Research》2006,66(2):213-232

Lithostratigraphic and palynological analysis of two cores recovered from the ‘Grand Lac’ (New Caledonia), combined with 35 ¹⁴C AMS dates, yields a paleoenvironmental record spanning the last 2000 yr. The lithology is represented mainly by clayey or laminated layers. A catastrophic event, which is marked by very coarse deposits, occurred probably between ca 1070-960 cal yr B.P. and possibly is associated with an unusually severe La Niña event. Before and after this event, a similar combination of the two main sediment types is recorded. The repeated alternation of laminated and clayey layers is interpreted as the response to local hydrologic forcing, which may reflect a shift from relatively wet to relatively drier conditions, respectively. Variable amount of micro-charcoal is detected all along the profile. Without additional evidence, notwithstanding the initial local human settlement documented since ca 2900 ¹⁴C yr B.P., micro-charcoal occurrence and variability cannot be linked directly to an anthropogenic origin. No distinct palynological zonations in relation to the lithology are observed, and the vegetation changes may only represent minor transitions across environmental limits.  相似文献   

Internal and forced variability along a section between Greenland and Portugal in the CLIPPER Atlantic model     

Anne Marie Treguier  Claire Gourcuff  Pascale Lherminier  Herle Mercier  Bernard Barnier  Gurvan Madec  Jean-Marc Molines  Thierry Penduff  Lars Czeschel  Claus Böning 《Ocean Dynamics》2006,56(5-6):568-580

Numerical models are used to estimate the meridional overturning and transports along the paths of two hydrographic cruises, carried out in 1997 and 2002 from Greenland to Portugal. We have examined the influence of the different paths of the two cruises and found that it could explain 0.4 to 2 Sv of difference in overturning (the precise value is model-dependent). Models show a decrease in the overturning circulation between 1997 and 2002, with different amplitudes. The CLIPPER ATL6 model reproduces well the observed weakening of the overturning in density coordinates between the cruises; in the model, the change is due to the combination of interannual and high-frequency forcing and internal variability associated with eddies and meanders. Examination of the -coordinate overturning reveals model–data discrepancies: the vertical structure in the models does not change as much as the observed one. The East Greenland current variability is mainly wind-forced in the ATL6 model, while fluctuations due to eddies and instabilities explain a large part of the North Atlantic Current variability. The time-residual transport of dense water and heat due to eddy correlations between currents and properties is small across this section, which is normal to the direction of the main current.  相似文献