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Katrine K. Andersen Anders Svensson Sigfus J. Johnsen Sune O. Rasmussen Matthias Bigler Regine Rthlisberger Urs Ruth Marie-Louise Siggaard-Andersen Jrgen Peder Steffensen Dorthe Dahl-Jensen Bo M. Vinther Henrik B. Clausen 《Quaternary Science Reviews》2006,25(23-24):3246
The Greenland Ice Core Chronology 2005, GICC05, is extended back to 42 ka b2k (before 2000 AD), i.e. to the end of Greenland Stadial 11. The chronology is based on independent multi-parameter counting of annual layers using comprehensive high-resolution measurements available from the North Greenland Ice Core Project, NGRIP. These are measurements of visual stratigraphy, conductivity of the solid ice, electrolytical melt water conductivity and the concentration of Na+, Ca2+, SO42−, NO3−, NH4+. An uncertainty estimate of the time scale is obtained from identification of ‘uncertain’ annual layers, which are counted as 0.5±0.5 years. The sum of the uncertain annual layers, the so-called maximum counting error of the presented chronology ranges from 4% in the warm interstadial periods to 7% in the cold stadials. The annual accumulation rates of the stadials and interstadials are on average one-third and half of the present day values, respectively, and the onset of the Greenland Interstadials 2, 3, and 8, based on 20 year averaged δ18O values, are determined as 23,340, 27,780, and 38,220 yr b2k in GICC05. 相似文献
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Christopher Potter Peggy Gross Vanessa Genovese Marie-Louise Smith 《Carbon balance and management》2007,2(1):1-11
Background
A simulation model that relies on satellite observations of vegetation cover from the Landsat 7 sensor and from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate net primary productivity (NPP) of forest stands at the Bartlett Experiment Forest (BEF) in the White Mountains of New Hampshire.Results
Net primary production (NPP) predicted from the NASA-CASA model using 30-meter resolution Landsat inputs showed variations related to both vegetation cover type and elevational effects on mean air temperatures. Overall, the highest predicted NPP from the NASA-CASA model was for deciduous forest cover at low to mid-elevation locations over the landscape. Comparison of the model-predicted annual NPP to the plot-estimated values showed a significant correlation of R2 = 0.5. Stepwise addition of 30-meter resolution elevation data values explained no more than 20% of the residual variation in measured NPP patterns at BEF. Both the Landsat 7 and the 250-meter resolution MODIS derived mean annual NPP predictions for the BEF plot locations were within ± 2.5% of the mean of plot estimates for annual NPP.Conclusion
Although MODIS imagery cannot capture the spatial details of NPP across the network of closely spaced plot locations as well as Landsat, the MODIS satellite data as inputs to the NASA-CASA model does accurately predict the average annual productivity of a site like the BEF. 相似文献3.
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Anne-Marie Lézine Jean-François Saliège Christian Robert Frédéric Wertz Marie-Louise Inizan 《Quaternary Research》1998,50(3):290-299
Paleoecology and paleohydrology of the Ramlat as-Sab'atayn (Southern Arabia) are reconstructed from a comparative study including sedimentology, mineralogy, stable isotope ratios of carbonates, and palynology of lacustrine sediments recovered from the al-Hawa depression. The section dates from 8700 to 7200 yr B.P. and records an early phase of flooding followed by distinct lacustrine development from 7800 to 7200 yr B.P., coeval with maximum activity of the Indian monsoon. Comparison of the pollen record with modern pollen deposition suggests that regional vegetation was then already of desert type and was related to strong seasonal trade winds. 相似文献
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