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1.
Ramzi Touchan Elena Xoplaki Gary Funkhouser Jürg Luterbacher Malcolm K. Hughes Nesat Erkan Ünal Akkemik Jean Stephan 《Climate Dynamics》2005,25(1):75-98
This study represents the first large-scale systematic dendroclimatic sampling focused on developing chronologies from different
species in the eastern Mediterranean region. Six reconstructions were developed from chronologies ranging in length from 115 years
to 600 years. The first reconstruction (1885–2000) was derived from principal components (PCs) of 36 combined chronologies.
The remaining five, 1800–2000, 1700–2000, 1600–2000, 1500–2000 and 1400–2000 were developed from PCs of 32, 18, 14, 9, and
7 chronologies, respectively. Calibration and verification statistics for the period 1931–2000 show good levels of skill for
all reconstructions. The longest period of consecutive dry years, defined as those with less than 90% of the mean of the observed
May–August precipitation, was 5 years (1591–1595) and occurred only once during the last 600 years. The longest reconstructed
wet period was 5 years (1601–1605 and 1751–1755). No long term trends were found in May–August precipitation during the last
few centuries. Regression maps are used to identify the influence of large-scale atmospheric circulation on regional precipitation.
In general, tree-ring indices are influenced by May–August precipitation, which is driven by anomalous below (above) normal
pressure at all atmospheric levels and by convection (subsidence) and small pressure gradients at sea level. These atmospheric
conditions also control the anomaly surface air temperature distribution which indicates below (above) normal values in the
southern regions and warmer (cooler) conditions north of around 40°N. A compositing technique is used to extract information
on large-scale climate signals from extreme wet and dry summers for the second half of the twentieth century and an independent
reconstruction over the last 237 years. Similar main modes of atmospheric patterns and surface air temperature distribution
related to extreme dry and wet summers were identified both for the most recent 50 years and the last 237 years. Except for
the last few decades, running correlation analyses between the major European-scale circulation patterns and eastern Mediteranean
spring/summer precipitation over the last 237 years are non-stationary and insignificant, suggesting that local and/or sub-regional
geographic factors and processes are important influences on tree-ring variability over the last few centuries. 相似文献
2.
Winter-to-spring temperature dynamics in Turkey derived from tree rings since AD 1125 总被引：2，自引：1，他引：1
Ingo Heinrich Ramzi Touchan Isabel Dorado Liñán Heinz Vos Gerhard Helle 《Climate Dynamics》2013,41(7-8):1685-1701
In the eastern Mediterranean in general and in Turkey in particular, temperature reconstructions based on tree rings have not been achieved so far. Furthermore, centennial-long chronologies of stable isotopes are generally also missing. Recent studies have identified the tree species Juniperus excelsa as one of the most promising tree species in Turkey for developing long climate sensitive stable carbon isotope chronologies because this species is long-living and thus has the ability to capture low-frequency climate signals. We were able to develop a statistically robust, precisely dated and annually resolved chronology back to AD 1125. We proved that variability of δ13C in tree rings of J. excelsa is mainly dependent on winter-to-spring temperatures (January–May). Low-frequency trends, which were associated with the medieval warm period and the little ice age, were identified in the winter-to-spring temperature reconstruction, however, the twentieth century warming trend found elsewhere could not be identified in our proxy record, nor was it found in the corresponding meteorological data used for our study. Comparisons with other northern-hemispherical proxy data showed that similar low-frequency signals are present until the beginning of the twentieth century when the other proxies derived from further north indicate a significant warming while the winter-to-spring temperature proxy from SW-Turkey does not. Correlation analyses including our temperature reconstruction and seven well-known climate indices suggest that various atmospheric oscillation patterns are capable of influencing the temperature variations in SW-Turkey. 相似文献
3.
Spatiotemporal drought variability in northwestern Africa over the last nine centuries 总被引：3，自引：1，他引：2
Ramzi Touchan Kevin J. Anchukaitis David M. Meko Mohamed Sabir Said Attalah Ali Aloui 《Climate Dynamics》2011,37(1-2):237-252
Changes in precipitation patterns and the frequency and duration of drought are likely to be the feature of anthropogenic climate change that will have the most direct and most immediate consequences for human populations. The latest generation of state-of-the-art climate models project future widespread drying in the subtropics. Here, we reconstruct spatially-complete gridded Palmer drought severity index values back to A.D. 1179 over Morocco, Algeria, and Tunisia. The reconstructions provide long-term context for northwest African hydroclimatology, revealing large-scale regional droughts prior to the sixteenth century, as well as more heterogeneous patterns in sixteenth, eighteenth, and twentieth century. Over the most recent decades a shift toward dry conditions over the region is observed, which is consistent with general circulation model projections of greenhouse gas forced enhanced regional subtropical drought. 相似文献
4.
Ramzi Gharsalli Taher Zouaghi Mohamed Soussi Riadh Chebbi Sami Khomsi Mourad Bédir 《Comptes Rendus Geoscience》2013,345(9-10):401-417
The Cap Bon Peninsula, belonging to northeastern Tunisia, is located in the Maghrebian Alpine foreland and in the North of the Pelagian block. By its paleoposition, during the Cenozoic, in the edge of the southern Tethyan margin, this peninsula constitutes a geological entity that fossilized the eustatic, tectonic and climatic interactions. Surface and subsurface study carried out in the Cap Bon onshore area and surrounding offshore of Hammamet interests the Miocene deposits from the Langhian-to-Messinian interval time. Related to the basin and the platform positions, sequence and seismic stratigraphy studies have been conducted to identify seven third-order seismic sequences in subsurface (SM1-SM7), six depositional sequences on the Zinnia-1 petroleum well (SDM1-SDM6), and five depositional sequences on the El Oudiane section of the Jebel Abderrahmane (SDM1–SDM5). Each sequence shows a succession of high-frequency systems tract and parasequences. These sequences are separated by remarkable sequence boundaries and maximum flooding surfaces (SB and MFS) that have been correlated to the eustatic cycles and supercycles of the Global Sea Level Chart of Haq et al. (1987). The sequences have been also correlated with Sequence Chronostratigraphic Chart of Hardenbol et al. (1998), related to European basins, allows us to arise some major differences in number and in size. The major discontinuities, which limit the sequences resulted from the interplay between tectonic and climatic phenomena. It thus appears very judicious to bring back these chronological surfaces to eustatic and/or local tectonic activity and global eustatic and climatic controls. 相似文献
5.
Solidification of Tank Bottom Sludge 总被引：1，自引：0，他引：1
Ramzi A. Taha Yahia E.-A. Mohamedzein Amer A. Al-Rawas Yahya Al-Suleimani 《Geotechnical and Geological Engineering》2010,28(1):15-25
Tank bottom oily sludge (S) is collected from tank bottoms during cleaning operations and contaminated soil is collected after
spills and leakages. Disposal of tank sludge is a significant item of tank maintenance for producers, refiners and transporters
of petroleum materials. The objective of this paper is to investigate the use of various additives in the solidification of
tank bottom sludge. The sludge was solidified using various combinations of additives including ordinary Portland cement (OPC),
cement by-pass dust (CBPD) and quarry fines (QF). Geotechnical and leachability properties of the mixtures were determined.
The use of OPC alone as a solidifying agent yielded the best results. This was followed by blends S:OPC:QF of 1:0.5:1.5 and
S:CBPD of 1:2. Economically, the latter two mixtures would be considered more cost-effective in solidifying the sludge as
the additives are waste by-product materials. The Toxicity Characteristic Leaching Procedure (TCLP) results indicated that
no extracts exceeded the threshold TCLP limits established by U.S. Environmental Protection Agency (USEPA). The solidified
material can be used in construction of roads, embankments and landfill layers. 相似文献
6.
Neogene sediment deformations and tectonic features of northeastern Tunisia: evidence for paleoseismicity 总被引：1，自引：1，他引：0
Taher Zouaghi Mourad Bédir Fetheddine Melki Hakim Gabtni Ramzi Gharsalli Aida Bessioud Fouad Zargouni 《Arabian Journal of Geosciences》2011,4(7-8):1301-1314
The Neogene stratigraphic series is characterized by predominant clayey facies alternated by other sand layers. The outcrop and subsurface studies show varied and complex styles of deformations and lead to relate the structures to paleoseismic events. The seismicity of eastern onshore and offshore Tunisian margin follows the master fault corridors oriented globally N–S, E–W, and NW–SE that correspond to the bordering faults of grabens and syncline corridors and associated faulted drag fold structures oriented NE–SW. Epicenters of magnitudes between 3 and 5 are located along these border fault corridors. The Neogene strata record brittle structures, including numerous and deep faults and fractures with straight and high-angle dipping planes. The structuring of NE–SW en echelon folds and synclines inside and outside NW–SE and E–W right lateral and N–S and NE–SW left lateral tectonic corridors indicates the strike-slip type of bordering faults and their seismogenic nature. Wrench fault movements that induce mud and salt diapirs, mud volcanoes, and intrusive ascensions are related to seismic shocks. Seismic waves caused by activity along one, or most likely, several tectonic structures would have propagated throughout the Quaternary cover producing seismites. The similarity of deposits, structuring, and seismites between the Tunis-Bizerte to the North and Hammamet-Mahdia to the South accredits the hypothesis that the seismic episodes might have affected sedimentation patterns along the Sahalian large geographic area. The paleoseismic events in northeastern Tunisia might be related to tectonic fault reactivations through time. This hypothesis is consistent with the geomorphologic context of the study area, characterized by several morphostructural lineaments with strong control on the sediment distribution, as well as uplifted and subsiding terrains. The estimated magnitude of the seismic events and the great regional tectonically affected areas demonstrate that the northeastern Tunisia experienced stress through the last geological episodes of its evolution. This Neogene kinematic reconstruction highlights the neotectonic system inducing the actual seismicity on this margin. Therefore, there is a straight relationship between deepseated faults and seismicity. 相似文献
7.
An October–June precipitation reconstruction was developed from a Pinus halepensis regional tree-ring chronology from four sites in northwestern Tunisia for the period of 1771–2002. The reconstruction is based on a reliable and replicable statistical relationship between climate and tree-ring growth and shows climate variability on both interannual and interdecadal time scales. Thresholds (12th and 88th percentiles) based on the empirical cumulative distribution of observed precipitation for the 1902–2002 calibration period were used to delineate dry years and wet years of the long-term reconstruction. The longest reconstructed drought by this classification in the 232-year reconstruction is 2 years, which occurred in the 19th century. Analysis of 500 mb height data for the period 1948–2002 suggests reconstructed extreme dry and wet events can provide information on past atmospheric circulation anomalies over a broad region including the Mediterranean, Europe and eastern Asia. 相似文献
8.
Dendrochronology is a valuable tool for the study of past climate and increases our knowledge of climate variability beyond the short period covered by instrumental data. Two annual tree-ring width chronologies were developed for northern Jordan (Pinus halepensis and Quercus aegilops), one chronology for Carmel Mountain, Israel (Pinus halepensis), and one chronology for southern Jordan (Juniperus phoenicia). The results of our study show that the northern site chronologies are significantly correlated, but the northern and southern sites are not. A relatively high correlation was shown between October–April precipitation and a Pinus halepensis chronology, and between October–May precipitation and Quercus aegilops, both in the north. October–May precipitation was reconstructed for the time span AD 1600 to 1995 from the Juniperus phoenicia tree-ring chronology. The longest reconstructed drought, defined as consecutive years below a threshold of 80% of the 1946–1995 mean observed October–May precipitation, was 4 years, compared with 3 years for the 1946–95 instrumental data. 相似文献
9.
A May–July precipitation nested reconstruction for the period AD 1415–2010 was developed from multi-century tree-ring records of Pinus nigra, Pinus brutia, and Cedrus brevifolia for Cyprus. Calibration and verification statistics for the period 1917–2010 show a good level of skill, and split-sample validation over 1917–2010 supports temporal stability of the tree-ring signal for precipitation. Smoothed annual time series of reconstructed precipitation and a tally of drought events in a moving time window indicate that the calibration period is not representative of the full range of drought variability. While convective precipitation in the warm season may be driven strongly by local factors, composite maps of geopotential height anomaly for dry years and wet years support large-scale atmospheric-flow influence related to height anomalies over the broader region of northeast Africa and the eastern Mediterranean. Emerging positive trend in reconstruction residuals may be an early sign of exacerbation of drought stress on trees by recent warming in May–July. Future warming expected from increases in greenhouse gases poses a threat to forest resources in Cyprus and elsewhere in the Mediterranean. 相似文献
10.
Spatio‐temporal dynamics and biomass of Cymodocea nodosa in Bekalta (Tunisia,Southern Mediterranean Sea) 
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下载免费PDF全文 Leaf growth, biomass and production of Cymodocea nodosa were measured from October 2006 to September 2007 in Monastir Bay (Tunisia). Shoot density showed a clear seasonal pattern, increasing during spring and summer and decreasing during fall and winter. Monthly mean shoot density ranged between 633 ± 48 and 704 ± 48 shoots?m?2. The monthly average total biomass ranged between 560 ± 37 and 646 ± 32 g dry weight (DW)?m?2. Total biomass varied significantly among stations and sampling times but did not show seasonal variation. Leaf plastochrone intervals varied seasonally, with an annual average of 28–30 days. Leaf productivity was highest in August (2.61 g DW?m?2?day?1) and lowest in February (0.35 g DW?m?2?day?1). Annual belowground primary production varied from 263 to 311 g DW?m?2?year?1. Annual leaf production was approximately equal for all the stations (from 264 to 289 g DW?m?2?year?1). Variability in water temperature, air temperature and salinity explained the annual variability in biological characteristics. Changes in belowground and total biomass were not correlated with seasonal variability in the environmental parameters monitored. Additionally, a literature review was conducted of C. nodosa features at other Mediterranean sites, encompassing 30 studies from 1985 to 2014. 相似文献