Late Holocene lake level dynamics inferred from magnetic susceptibility and stable oxygen isotope data: Lake Elsinore, southern California (USA)     

Matthew E. Kirby  Christopher J. Poulsen  Steve P. Lund  William P. Patterson  Liam Reidy  Douglas E. Hammond 《Journal of Paleolimnology》2004,31(3):275-293

Southern California faces an imminent freshwater shortage. To better assess the future impact of this water crisis, it is essential that we develop continental archives of past hydrological variability. Using four sediment cores from Lake Elsinore in Southern California, we reconstruct late Holocene (3800 calendar years B.P.) hydrological change using a twentieth-century calibrated, proxy methodology. We compared magnetic susceptibility from Lake Elsinore deep basin sediments, lake level from Lake Elsinore, and regional winter precipitation data over the twentieth century to calibrate the late Holocene lake sediment record. The comparison revealed a strong positive, first-order relationship between the three variables. As a working hypothesis, we suggest that periods of greater precipitation produce higher lake levels. Greater precipitation also increases the supply of detritus (i.e., magnetic-rich minerals) from the lake's surrounding drainage basin into the lake environment. As a result, magnetic susceptibility values increase during periods of high lake level. We apply this modern calibration to late Holocene sediments from the lake's littoral zone. As an independent verification of this hypothesis, we analyzed ¹⁸O_(calcite), interpreted as a proxy for variations in the precipitation:evaporation ratio, which reflect first order hydrological variability. The results of this verification support our hypothesis that magnetic susceptibility records regional hydrological change as related to precipitation and lake level. Using both proxy data, we analyzed the past 3800 calendar years of hydrological variability. Our analyses indicate a long period of dry, less variable climate between 3800 and 2000 calendar years B.P. followed by a wet, more variable climate to the present. These results suggest that droughts of greater magnitude and duration than those observed in the modern record have occurred in the recent geological past. This conclusion presents insight to the potential impact of future droughts on the over-populated, water-poor region of Southern California.  相似文献   

Modelling the sensitivity of wheat growth and water balance to climate change in Southeast Australia   总被引：3，自引：0，他引：3  

Jing Wang  Enli Wang  Qunying Luo  Mac Kirby 《Climatic change》2009,96(1-2):79-96

A simulation study was carried out to assess the potential sensitivity of wheat growth and water balance components to likely climate change scenarios at Wagga Wagga, NSW, Australia. Specific processes considered include crop development, growth rate, grain yield, water use efficiency, evapotranspiration, runoff and deep drainage. Individual impacts of changes in temperature, rainfall and CO₂ concentration ([CO₂]) and the combined impacts of these three variables were analysed for 2050 ([CO₂] = 570 ppm, T +2.3°C, P ?7%) and 2070 ([CO₂] = 720 ppm, T +3.8°C, P ?10%) conditions. Two different rainfall change scenarios (changes in rainfall intensity or rainfall frequency) were used to modify historical rainfall data. The Agricultural Production Systems Simulator (APSIM) was used to simulate the growth and water balance processes for a 117 year period of baseline, 2050 and 2070 climatic conditions. The results showed that wheat yield reduction caused by 1°C increase in temperature and 10% decrease in rainfall could be compensated by a 266 ppm increase in [CO₂] assuming no interactions between the individual effects. Temperature increase had little impact on long-term average water balance, while [CO₂] increase reduced evapotranspiration and increased deep drainage. Length of the growing season of wheat decreased 22 days in 2050 and 35 days in 2070 conditions as a consequence of 2.3°C and 3.8°C increase in temperature respectively. Yield in 2050 was approximately 1% higher than the simulated baseline yield of 4,462 kg ha^???1, but it was 6% lower in 2070. An early maturing cultivar (Hartog) was more sensitive in terms of yield response to temperature increase, while a mid-maturing cultivar (Janz) was more sensitive to rainfall reduction. Janz could benefit more from increase in CO₂ concentration. Rainfall reduction across all rainfall events would have a greater negative impact on wheat yield and WUE than if only smaller rainfall events reduced in magnitude, even given the same total decrease in annual rainfall. The greater the reduction in rainfall, the larger was the difference. The increase in temperature increased the difference of impact between the two rainfall change scenarios while increase in [CO₂] reduced the difference.  相似文献   

Late Holocene hydroclimatic variability linked to Pacific forcing: evidence from Abbott Lake,coastal central California     

Christine A. Hiner  Matthew E. Kirby  Nicole Bonuso  William P. Patterson  Jennifer Palermo  Emily Silveira 《Journal of Paleolimnology》2016,56(4):299-313

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Modeling coastal tsunami hazard from submarine mass failures: effect of slide rheology,experimental validation,and case studies off the US East Coast     

Grilli  Stéphan T.  Shelby  Mike  Kimmoun  Olivier  Dupont  Guillaume  Nicolsky  Dmitry  Ma  Gangfeng  Kirby  James T.  Shi  Fengyan 《Natural Hazards》2017,86(1):353-391

Natural Hazards - We perform numerical simulations to assess how coastal tsunami hazard from submarine mass failures (SMFs) is affected by slide kinematics and rheology. Two types of two-layer SMF...  相似文献   

Towards an integral strategy for modelling uncertain geospatial data     

Zhang Jingxiong  R. Kirby  Lu Jiangbin 《地球空间信息科学学报》2013,16(1):42-48

This paper endeavours to put the discussion on errors and uncertainties in geographical information systems (GISs) in a more systematic way by examining the strength and weakness of discrete objects and continous fields, the two distinct schools of spatial data modelling. In doing so, it argues that neither discrete objects nor continous fields alone provide objective and complete representations of highly complex geographical phenomena, though there are good reasons for asserting that continuous fields are better suited to modelling spatial dependence, heterogeneity and fuzzines significant in geographical reality than discrete objects. Thus, there seems to be merit in adopting an integrated model incorporating analytical capabilities of fields and generalization functions of objects, for which extended TIN (triangulated irregular network) models along with their duals (Voronoi diagrams) provide a pragmatical solution.  相似文献   

A comparison of alternative criteria for defining fuzzy boundaries on fuzzy categorical maps     

Zhang Jingxiong  Roger Kirby 《地球空间信息科学学报》2013,16(2):26-34

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<Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar dating of tuff vents in the Campi Flegrei caldera (southern Italy): toward a new chronostratigraphic reconstruction of the Holocene volcanic activity   总被引：1，自引：0，他引：1  

L. Fedele  D. D. Insinga  A. T. Calvert  V. Morra  A. Perrotta  C. Scarpati 《Bulletin of Volcanology》2011,73(9):1323-1336

The Campi Flegrei hosts numerous monogenetic vents inferred to be younger than the 15 ka Neapolitan Yellow Tuff. Sanidine crystals from the three young Campi Flegrei vents of Fondi di Baia, Bacoli and Nisida were dated using ⁴⁰Ar/³⁹Ar geochronology. These vents, together with several other young edifices, occur roughly along the inner border of the Campi Flegrei caldera, suggesting that the volcanic conduits are controlled by caldera-bounding faults. Plateau ages of ∼9.6 ka (Fondi di Baia), ∼8.6 ka (Bacoli) and ∼3.9 ka (Nisida) indicate eruptive activity during intervals previously interpreted as quiescent. A critical revision, involving calendar age correction of literature ¹⁴C data and available ⁴⁰Ar/³⁹Ar age data, is presented. A new reference chronostratigraphic framework for Holocene Phlegrean activity, which significantly differs from the previously adopted ones, is proposed. This has important implications for understanding the Campi Flegrei eruptive history and, ultimately, for the evaluation of related volcanic risk and hazard, for which the inferred history of its recent activity is generally taken into account.  相似文献   

Distributed deformation around the eastern tip of the Kunlun fault   总被引：3，自引：0，他引：3  

Eric Kirby  Nathan Harkins 《International Journal of Earth Sciences》2013,102(7):1759-1772

Whether active strain within the Indo-Asian collision zone is primarily localized along major strike-slip fault systems or is distributed throughout the intervening crust between faults remains uncertain. Despite refined estimates of slip rates along many of the major fault zones, relatively little is known about how displacement along these structures is accommodated at fault terminations. Here, we show that a systematic decrease in left-lateral slip rates along the eastern ~200 km of the Kunlun fault, from >10 mm/year to <1 mm/year, is coincident with high topography in the Anyemaqen Shan and with a broad zone of distributed shear and clockwise vorticity within the Tibetan Plateau. Geomorphic analysis of river longitudinal profiles, coupled with inventories of cosmogenic radionuclides in fluvial sediment, reveal correlated variations in fluvial relief and erosion rate across the Anyemaqen Shan that reflect ongoing differential rock uplift across the range. Our results imply that the termination of the Kunlun fault system is accommodated by a combination of distributed crustal thickening and by clockwise rotation of the eastern fault segments.  相似文献   

Postshield stage transitional volcanism on Mahukona Volcano, Hawaii     

David A. Clague  Andrew T. Calvert 《Bulletin of Volcanology》2009,71(5):533-539

Age spectra from ⁴⁰Ar/³⁹Ar incremental heating experiments yield ages of 298 ± 25 ka and 310 ± 31 ka for transitional composition lavas from two cones on submarine Mahukona Volcano, Hawaii. These ages are younger than the inferred end of the tholeiitic shield stage and indicate that the volcano had entered the postshield alkalic stage before going extinct. Previously reported elevated helium isotopic ratios of lavas from one of these cones were incorrectly interpreted to indicate eruption during a preshield alkalic stage. Consequently, high helium isotopic ratios are a poor indicator of eruptive stage, as they occur in preshield, shield, and postshield stage lavas. Loihi Seamount and Kilauea are the only known Hawaiian volcanoes where the volume of preshield alkalic stage lavas can be estimated. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

2008年汶川地震造成的应力变化和四川盆地地震危险性增加   总被引：1，自引：0，他引：1  

T.Parsons  E.Kirby  张效亮 《世界地震译丛》2009,(1):17-20

2008年5月12日,灾难性的汶川7．9级大地震袭击了青藏高原东缘,造成四川盆地西部多个大城市房屋倒塌和大量人员伤亡。如此大的地震之后,地壳应力的重新调整通常会导致破坏性地震发生（Stein et al,1997;Stein,1999;McCloskey et al,2005;Parsons et al,2000;Parsons,2002）。5月12日地震的主震造成龙门山和四川盆地连接处最大位错量达9m,说明复杂的走滑和逆冲运动（Jiand Hayes,2008）为该地区的特征（Burchfiel et al,1995;Densmore et al,2007）。四川盆地及其周边也有其他活跃的走滑和逆冲断层相互交错。本文利用地震断层模型计算了由2008年5月12日汶川地震引起的同震应力变化,结果显示很多地区应力显著增加。快速给出这种应力变化图像有助于确定未来可能发生强余震的断层段。  相似文献