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271.
近1000年来西格陵兰荷尔斯泰因斯堡港生物硅指示的海洋生产力变化 总被引:1,自引:1,他引:0
We analyzed the biogenic silica(BSi) content and produced a diatom-based summer sea-surface temperature(SST) reconstruction for sediment core GC4 from the Holsteinsborg Dyb, West Greenland. Our aim was to reconstruct marine productivity and climatic fluctuations during the last millennium. Increased BSi content and diatom abundance suggest relatively high marine productively during the interval of AD 1000–1400, corresponding in time to the Medieval Warm Period(MWP). The summer SST reconstruction indicates relatively warm conditions during AD 900–1100, followed by cooling after AD 1100. An extended cooling period during AD 1400–1900 is characterized by prolonged low in reconstructed SST and high sea-ice concentration. The BSi values fluctuated during this period, suggesting varying marine productivity during the Little Ice Age(LIA).There is no significant correlation between the BSi content and SST during the last millennium, suggesting that the summer SST has little influence on marine productively in the Holsteinsborg Dyb. A good correspondence between the BSi content and the element Ti counts in core GC4 suggests that silicate-rich meltwater from the Greenland ice sheet was likely responsible for changes in marine productively in the Holsteinsborg Dyb. 相似文献
272.
In this paper, a time series from 1999 to 2007 of absolute total electron content (TEC) values has been computed and analyzed
using singular value decomposition (SVD). The data set has been computed using a Kalman Filter and is based on dual frequency
GPS data from three reference stations in Denmark located in the midlatitude region. The station separation between the three
stations is 132–208 km (the time series of the TEC can be freely downloaded at ). For each year, a SVD has been performed on the TEC time series in order to identify the three time varying (daily, yearly,
and 11 yearly) characteristics of the ionosphere. The applied SVD analysis provides a new method for separating the daily
from the yearly components. The first singular value is very dominant (approximately six times larger than the second singular
value), and this singular value corresponds clearly to the variation of the daily cycle over the year. The second singular
value corresponds to variations of the width of the daily peak over the year, and the third singular value shows a clear yearly
variation of the daily signal with peaks around the equinoxes. The singular values for each year show a very strong correlation
with the sunspot number for all the singular values. The correlation coefficients for the first 5 sets of singular values
are all above 0.96. Based on the SVD analysis yearly models of the TEC in the ionosphere can be recomposed and illustrate
the three time varying characteristics of the ionosphere very clearly. By prediction of the yearly mean sunspot number, future
yearly models can also be predicted. These can serve as a priori information for a real time space weather service providing
information of the current status of the ionosphere. They will improve the Kalman filter processing making it more robust,
but can also be used as starting values in the initialization phase in case of gaps in the data stream. Furthermore, the models
can be used to detect variations from the normal local ionospheric activity. 相似文献
273.
Biodiversity Conservation in the REDD 总被引:1,自引:0,他引:1
Gary D Paoli Philip L Wells Erik Meijaard Matthew J Struebig Andrew J Marshall Krystof Obidzinski Aseng Tan Andjar Rafiastanto Betsy Yaap JW Ferry Slik Alexandra Morel Balu Perumal Niels Wielaard Simon Husson Laura D'Arcy 《Carbon balance and management》2010,5(1):1-9