Late Holocene climates of the Near East deduced from Dead Sea level variations and modern regional winter rainfall     

Yehouda Enzel  Revital Bookman  David Sharon  Haim Gvirtzman  Uri Dayan  Baruch Ziv  Mordechai Stein 《Quaternary Research》2003,60(3):263-273

The Dead Sea is a terminal lake of one of the largest hydrological systems in the Levant and may thus be viewed as a large rain gauge for the region. Variations of its level are indicative of the climate variations in the region. Here, we present the decadal- to centennial-resolution Holocene lake-level curve of the Dead Sea. Then we determine the regional hydroclimatology that affected level variations. To achieve this goal we compare modern natural lake-level variations and instrumental rainfall records and quantify the hydrology relative to lake-level rise, fall, or stability. To quantify that relationship under natural conditions, rainfall data pre-dating the artificial Dead Sea level drop since the 1960s are used. In this respect, Jerusalem station offers the longest uninterrupted pre-1960s rainfall record and Jerusalem rains serve as an adequate proxy for the Dead Sea headwaters rainfall. Principal component analysis indicates that temporal variations of annual precipitation in all stations in Israel north of the current 200 mm yr⁻¹ average isohyet during 1940–1990 are largely synchronous and in phase (70% of the total variance explained by PC1). This station also represents well northern Jordan and the area all the way to Beirut, Lebanon, especially during extreme drought and wet spells. We (a) determine the modern, and propose the past regional hydrology and Eastern Mediterranean (EM) climatology that affected the severity and length of droughts/wet spells associated with multiyear episodes of Dead Sea level falls/rises and (b) determine that EM cyclone tracks were different in average number and latitude in wet and dry years in Jerusalem. The mean composite sea level pressure and 500-mb height anomalies indicate that the potential causes for wet and dry episodes span the entire EM and are rooted in the larger-scale northern hemisphere atmospheric circulation. We also identified remarkably close association (within radiocarbon resolution) between climatic changes in the Levant, reflected by level changes, and culture shifts in this region.  相似文献   

U-Th dating of Lake Lisan (late Pleistocene dead sea) aragonite and implications for glacial east Mediterranean climate change     

Alexandra Haase-Schramm  Steven L. Goldstein  Mordechai Stein 《Geochimica et cosmochimica acta》2004,68(5):985-1005

U-series dating can be an effective means to obtain accurate and precise ages on Quaternary carbonates. However, most samples require a correction for U and Th in admixed detritus. This complication is often addressed through generation of U-Th isochrons, requiring analyses of several coeval samples. In addition, presence of water-derived (hydrogenous) Th in the carbonate can cause inaccuracies in isochron ages.This study reports a high-resolution U-series chronology of sediments deposited by Lake Lisan, the last glacial precursor of the Dead Sea. The strategy employed combines multiple measurements from a few stratigraphic heights and fewer analyses from many heights in a single described and measured section. The resulting chronology is based on ages at 22 heights in a ∼40-m-thick section covering the interval of ∼70-14 calendar ka BP. The effects of admixed detritus are evaluated using trace elements. Nearly pure aragonite samples, indicated by very low abundances of insoluble elements such as Nb and Zr, were found to contain hydrogenous Th, which causes the uncorrected U-²³⁰Th age of a modern sample to be ∼2.5 ka. Nevertheless, accurate ages have been obtained by correcting for the detrital and aqueous interferences. The resulting ages are in stratigraphic order, and their accuracy is evidenced by consistency of Lisan Formation U-series and ¹⁴C ages with the coral-based calendar-radiocarbon age calibration.The U-Th ages provide a context to unravel the limnological history of Lake Lisan. Boundaries between the Lower, Middle, and Upper stratigraphic units correspond to the MIS 4/3 and 3/2 transitions, respectively. During MIS 2 and 4 the lake generally showed a stable two-layer configuration and a positive fresh-water balance, reflected by deposition of laminated aragonite-detritus. Dry intervals during MIS 2 and 4 are indicated by thick gypsum layers and an inferred depositional hiatus, which are temporally associated with Heinrich events H1 at ∼17 ka and H6 at ∼65 ka, respectively. During MIS 3 the lake level was unstable with intermittent dry periods indicated by abundant clastic layers and a significant hiatus between ∼43-49 ka. Clastic layers are associated with Dansgaard-Oeschger events during MIS 3, and indicate lake level declines during abrupt Northern Hemisphere warmings. Overall, the climate of the Eastern Mediterranean region shows a strong linkage to the Northern Hemisphere climate, with increasing lake size and stability during cold periods, and fluctuations and dessication during warmings and Heinrich events.  相似文献   

Comments on “Earth's heat flux revised and linked to chemistry” by A.M. Hofmeister and R.E. Criss     

R. Von Herzen  E.E. Davis  A.T. Fisher  C.A. Stein  H.N. Pollack   《Tectonophysics》2005,409(1-4):193-198

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Sea-rain-lake relation in the Last Glacial East Mediterranean revealed by δO-δC in Lake Lisan aragonites     

Yehoshua Kolodny  Mordechai Stein 《Geochimica et cosmochimica acta》2005,69(16):4045-4060

We investigated the Sea-Rain-Lake relation during the Last Glacial-Holocene in the East Mediterranean region by comparing the δ¹⁸O and δ¹³C records of authigenic aragonite deposited in Lake Lisan, the Dead Sea, Mediterranean foraminifera, and speleothems. The Lisan Formation data display long- and short-term variations of δ¹⁸O, representing steady-state conditions of the lake (e.g., 5.6‰ ± 0.5‰ and 4.5‰ ± 1‰ in the Upper and Lower Members of the Lisan Formation, respectively), and short-term excursions reflecting large floods and droughts. The long-term (steady-state) δ¹⁸O values of the Lisan aragonites show similarity to the corresponding time-equivalent records of the Eastern Mediterranean foraminifera and Judea Mountain speleothems: The Last Glacial deposits are in all of them 2‰-3‰ heavier than the Holocene ones. We interpret this similarity as reflecting the significance of the source effect on the long-term behavior of isotopic reservoirs: Speleothem δ¹⁸O is strongly influenced by the marine reservoir that contributes its vapor to rain formation; the lake δ¹⁸O is dominated by the composition of the inflowing water. Short-term variations in the isotopic composition of rainfall are dominated by the amount effect and the temperature and those of the Lake’s upper water mass by the lake’s water balance.δ¹³C values are more variable than δ¹⁸O in the same Lisan sequences (e.g., δ¹³C in the Lower Member is 1.0‰ ± 1.7‰, whereas δ¹⁸O is 4.6‰ ± 0.7‰) and are 1‰ to 1.5‰ higher in the Upper Member than in the Lower and Middle Members of the Lisan Formation. These variations reflect significant increase in primary productivity of the lake and algal bloom activity. It appears that the hypersaline-saline lakes were not as “dead” as the Dead Sea is and that algal activity had an important impact upon the geochemistry of Lake Lisan.The δ¹⁸O data combined with independent geochemical and limnologic information (e.g., level fluctuations) indicate that Lisan time was characterized by high precipitation-high lake stands-high atmospheric humidity, whereas the Holocene Dead Sea shows the opposite behavior. This paleoclimatic reconstruction is consistent with independent evidence for significantly wetter conditions in the East Mediterranean region during the Last Glacial period.  相似文献   

Public attitudes towards flooding and property-level flood protection measures     

Seth Owusu  Grant Wright  Scott Arthur 《Natural Hazards》2015,77(3):1963-1978

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Estimation of daily stream water temperatures with a Bayesian regression approach          下载免费PDF全文

Mohammad M. Sohrabi  Rohan Benjankar  Daniele Tonina  Seth J. Wenger  Daniel J. Isaak 《水文研究》2017,31(9):1719-1733

Stream water temperature plays a significant role in aquatic ecosystems where it controls many important biological and physical processes. Reliable estimates of water temperature at the daily time step are critical in managing water resources. We developed a parsimonious piecewise Bayesian model for estimating daily stream water temperatures that account for temporal autocorrelation and both linear and nonlinear relationships with air temperature and discharge. The model was tested at 8 climatically different basins of the USA and at 34 sites within the mountainous Boise River Basin (Idaho, USA). The results show that the proposed model is robust with an average root mean square error of 1.25 °C and Nash–Sutcliffe coefficient of 0.92 over a 2‐year period. Our approach can be used to predict historic daily stream water temperatures in any location using observed daily stream temperature and regional air temperature data.  相似文献   

Computational model coupling mode II discrete fracture propagation with continuum damage zone evolution          下载免费PDF全文

Wencheng Jin  Hao Xu  Chloé Arson  Seth Busetti 《国际地质力学数值与分析法杂志》2017,41(2):223-250

We propose a numerical method that couples a cohesive zone model (CZM) and a finite element‐based continuum damage mechanics (CDM) model. The CZM represents a mode II macro‐fracture, and CDM finite elements (FE) represent the damage zone of the CZM. The coupled CZM/CDM model can capture the flow of energy that takes place between the bulk material that forms the matrix and the macroscopic fracture surfaces. The CDM model, which does not account for micro‐crack interaction, is calibrated against triaxial compression tests performed on Bakken shale, so as to reproduce the stress/strain curve before the failure peak. Based on a comparison with Kachanov's micro‐mechanical model, we confirm that the critical micro‐crack density value equal to 0.3 reflects the point at which crack interaction cannot be neglected. The CZM is assigned a pure mode II cohesive law that accounts for the dependence of the shear strength and energy release rate on confining pressure. The cohesive shear strength of the CZM is calibrated by calculating the shear stress necessary to reach a CDM damage of 0.3 during a direct shear test. We find that the shear cohesive strength of the CZM depends linearly on the confining pressure. Triaxial compression tests are simulated, in which the shale sample is modeled as an FE CDM continuum that contains a predefined thin cohesive zone representing the idealized shear fracture plane. The shear energy release rate of the CZM is fitted in order to match to the post‐peak stress/strain curves obtained during experimental tests performed on Bakken shale. We find that the energy release rate depends linearly on the shear cohesive strength. We then use the calibrated shale rheology to simulate the propagation of a meter‐scale mode II fracture. Under low confining pressure, the macroscopic crack (CZM) and its damaged zone (CDM) propagate simultaneously (i.e., during the same loading increments). Under high confining pressure, the fracture propagates in slip‐friction, that is, the debonding of the cohesive zone alternates with the propagation of continuum damage. The computational method is applicable to a range of geological injection problems including hydraulic fracturing and fluid storage and should be further enhanced by the addition of mode I and mixed mode (I+II+III) propagation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Early development of strike-slip faulting: palaeoseismic study along the Petersen Mountain fault,northern Walker Lane,Nevada     

Conni De Masi  Rich Koehler  Seth Dee  Amanda Keen-Zebert 《第四纪科学杂志》2021,36(3):403-414

Characterising youthful strike-slip fault systems within transtensional regimes is often complicated by the presence of tectonic geomorphic features produced by normal faulting associated with oblique extension. The Petersen Mountain fault in the northern Walker Lane tectonic province exhibits evidence of both normal and strike-slip faulting. We present the results of geologic and geomorphic mapping, and palaeoseismic trenching that characterise the fault's style and sense of deformation. The fault consists of two major traces. The western trace displaces colluvial, landslide, and middle to late Pleistocene alluvial fans and is associated with aligned range front saddles, linear drainages, and oversteepened range front slopes. The eastern trace is associated with a low linear bedrock ridge, a narrow graben, right deflected stream channels, and scarps in late Pleistocene alluvial fan deposits. A trench on the eastern trace of the fault exposed a clear juxtaposition of disintegrated granodiorite bedrock against sand and boulder alluvial fan deposits across a steeply east-dipping fault. The stratigraphic evidence supports the occurrence of at least one late Pleistocene earthquake with a component of lateral displacement. As such, the Petersen Mountain fault accommodates part of the ~7 mm/yr of dextral shear distributed across the northern Walker Lane.  相似文献   

Do southern Appalachian Mountain summer stream temperatures respond to removal of understory rhododendron thickets?     

Scott Raulerson  C. Rhett Jackson  Nathan D. Melear  Seth E. Younger  Maura Dudley  Katherine J. Elliott 《水文研究》2020,34(14):3045-3060

Dense understory thickets of the native evergreen shrub Rhododendron maximum expanded initially following elimination of American chestnut by the chestnut blight, and later in response to loss of the eastern hemlock due to hemlock woolly adelgid invasion. Rhododendron thickets often blanket streams and their riparian zones, creating cool, low-light microclimates. To determine the effect of such understory thickets on summer stream temperatures, we removed riparian rhododendron understory on 300 m reaches of two southern Appalachian Mountain headwater streams, while leaving two 300 m reference reaches undisturbed. Overhead canopy was left intact in all four streams, but all streams were selected to have a significant component of dead or dying eastern hemlock in the overstory, creating time-varying canopy gaps throughout the reach. We continuously monitored temperatures upstream, within and downstream of treatment and reference reaches. Temperatures were monitored in all four streams in the summer before treatments were imposed (2014), and for two summers following treatment (2015, 2016). Temperatures varied significantly across and within streams prior to treatment and across years for the reference streams. After rhododendron removal, increases in summer stream temperatures were observed at some locations within the treatment reaches, but these increases did not persist downstream and varied by watershed, sensor, and year. Significant increases in daily maxima in treatment reaches ranged from 0.9 to 2.6°C. Overhead canopy provided enough shade to prevent rhododendron removal from increasing summer temperatures to levels deleterious to native cold-water fauna (average summer temperatures remained below 16°C), and local temperature effects were not persistent.  相似文献   

Evaluation of dynamically downscaled extreme temperature using a spatially-aggregated generalized extreme value (GEV) model     

Jiali Wang  Yuefeng Han  Michael L. Stein  Veerabhadra R. Kotamarthi  Whitney K. Huang 《Climate Dynamics》2016,47(9-10):2833-2849

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