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Olga V. Sidorova Matthias Saurer Vladimir S. Myglan Anja Eichler Margit Schwikowski Aleksander V. Kirdyanov Marina V. Bryukhanova Oksana V. Gerasimova Ivan A. Kalugin Andrey V. Daryin Rolf T. W. Siegwolf 《Climate Dynamics》2012,38(1-2):175-188
For the first time we present a multi-proxy data set for the Russian Altai, consisting of Siberian larch tree-ring width (TRW), latewood density (MXD), δ13C and δ18O in cellulose chronologies obtained for the period 1779–2007 and cell wall thickness (CWT) for 1900–2008. All of these parameters agree well between each other in the high-frequency variability, while the low-frequency climate information shows systematic differences. The correlation analysis with temperature and precipitation data from the closest weather station and gridded data revealed that annual TRW, MXD, CWT, and δ13C data contain a strong summer temperature signal, while δ18O in cellulose represents a mixed summer and winter temperature and precipitation signal. The temperature and precipitation reconstructions from the Belukha ice core and Teletskoe lake sediments were used to investigate the correspondence of different independent proxies. Low frequency patterns in TRW and δ13C chronologies are consistent with temperature reconstructions from nearby Belukha ice core and Teletskoe lake sediments showing a pronounced warming trend in the last century. Their combination could be used for the regional temperature reconstruction. The long-term δ18O trend agrees with the precipitation reconstruction from the Teletskoe lake sediment indicating more humid conditions during the twentieth century. Therefore, these two proxies could be combined for the precipitation reconstruction. 相似文献
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The Most Frequent Value Method (MFV) is applied to groundwater modeling as a robust and effective geostatistical method. The Most Frequent Value method is theoretically derived from the minimization of the information loss called the I-divergence. The MFV algorithm is then coupled with global optimization (Very Fast Simulated Annealing) to provide a powerful method for solving the inverse problems in groundwater modeling. The advantages and applicability of this new approach are illustrated by means of theoretical investigations and case studies. It is demonstrated that the MFV method has certain advantages over the conventional statistical methods derived from the maximum likelihood principle.
Resumen El Método del Valor Mas Frecuente (VMF), es aplicado al modelamiento de agua subterránea, como un método geoestadístico simple y efectivo. Este método es derivado teóricamente de la acción de reducir al mínimo la pérdida de información, llamada así divergencia – I. El algoritmo del VMF es entonces acoplado con optimización global(Very Fast Simulated Annealing), para obtener así un método efectivo que resuelva los problemas inversos en el modelamiento de aguas subterráneas. Las ventajas y aplicabilidad de esta aproximación nueva son ilustradas a través de investigaciones teóricas y estudios de caso. Se demuestra que el método VMF tiene ciertas ventajas sobre los métodos estadísticos convencionales derivados del principio de la probabilidad máxima.
Résumé On a appliqué la méthode de la valeur la plus fréquente (VPF) comme une méthode géostatistique robuste et efficace pour modéliser les eaux souterraines. Du point de vue théorique, la méthode de VPF part de la minimisation de linformation perdue, dénommée I-divergence. On couple après lalgorithme de la méthode de VPF avec la méthode doptimisation globale affin de réaliser une méthode performante pour résoudre le problème inverse dans le domaine des eaux souterraine. Les avantages et les possibilités dapplication de cette nouvelle approche sont illustrées par des investigations théoriques, ainsi que par des études de cas. On montre que la méthode de VPF présente certains avantages par rapport des méthodes statistiques conventionnelles basées sur le principe de la probabilité maximale.相似文献
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Anja Eichler Willy Tinner Sabina Brütsch Susanne Olivier Tatyana Papina Margit Schwikowski 《Quaternary Science Reviews》2011,30(9-10):1027-1034
Forest fires play a key role in the global carbon cycle and thus, can affect regional and global climate. Although fires in extended areas of Russian boreal forests have a considerable influence on atmospheric greenhouse gas and soot concentrations, estimates of their impact on climate are hampered by a lack of data on the history of forest fires. Especially regions with strong continental climate are of high importance due to an intensified development of wildfires. In this study we reconstruct the fire history of Southern Siberia during the past 750 years using ice-core based nitrate, potassium, and charcoal concentration records from Belukha glacier in the continental Siberian Altai. A period of exceptionally high forest-fire activity was observed between AD 1600 and 1680, following an extremely dry period AD 1540–1600. Ice-core pollen data suggest distinct forest diebacks and the expansion of steppe in response to dry climatic conditions. Coherence with a paleoenvironmental record from the 200 km distant Siberian lake Teletskoye shows that the vegetational shift AD 1540–1680, the increase in fire activity AD 1600–1680, and the subsequent recovery of forests AD 1700 were of regional significance. Dead biomass accumulation in response to drought and high temperatures around AD 1600 probably triggered maximum forest-fire activity AD 1600–1680. The extreme dry period in the 16th century was also observed at other sites in Central Asia and is possibly associated with a persistent positive mode of the Pacific Decadal Oscillation (PDO). No significant increase in biomass burning occurred in the Altai region during the last 300 years, despite strongly increasing temperatures and human activities. Our results imply that precipitation changes controlled fire-regime and vegetation shifts in the Altai region during the past 750 years. We conclude that high sensitivity of ecosystems to occasional decadal-scale drought events may trigger unprecedented environmental reorganizations under global-warming conditions. 相似文献
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A recent historical marine ecological case study (cod in the eastern Baltic Sea) is used to show how long-term data and knowledge of fluctuations can contribute to revisions of fishery management policy. The case study first developed new longer analytical time series of spawner biomass and recruitment back to the 1920s, which extended knowledge of population dynamics into a time period when ecosystem state was characterized by temporally varying combinations of exploitation, climate-hydrographic conditions, marine mammal predation and eutrophication. Recovery of spatially resolved historical catch data from the late 1500s to early 1600s also contributed new perspectives to cod population dynamics under alternative ecosystem forcings. These new perspectives have contributed, and will likely continue to contribute to new management policies (e.g., revision of fishery management reference points), which should lead to higher sustainability of the population and fishery yields, and improved overall ecosystem health. These perspectives will likely continue to provide baseline information as ICES and the EU develop new policies based on maximum sustainable yield concepts. 相似文献
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The Eastern Baltic cod stock was until recently below safe biological limits and suffered from high fishing pressure. In most recent years, fishing mortality substantially declined and spawner biomass more than tripled. Similar developments have not been observed for any other depleted cod stock in the North Atlantic during the last few decades. This paper investigates relative impacts of changes in different ecological and management-related drivers, which could have contributed to the rapid recovery of the Eastern Baltic cod. The results show that the success to reduce fishing mortality below management target in 2008 was due to a combination of increased recruitment and improved compliance with TAC. The reversal of the negative trend in biomass and rebuilding of the stock to the present level were largely driven by increased recruitment. Harvest control rules of the multi-annual management plan for setting TACs currently maintain the fishing mortality at a low level, which allows the stock to accumulate biomass and further accelerate its recovery. Relatively strong incoming year-classes and recently better control over removals distinguish the Eastern Baltic cod from other depleted European cod stocks, which have not shown similar positive trends in recent years. Sound management measures and compliance to those as well as favourable biological conditions are required for a successful stock recovery. 相似文献
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Relationships between environmental and social factors have long been studied by geographers.Nowadays,GIS-aided statistical analysis provides new tools to explore these relationships.In order to detect the impact of topography on social factors,we selected the country of Montenegro as a case example due to its high topographic variability.We compared the spatial pattern of population,settlements and ethnic minorities to physical geographic factors,especially to topography,but lithology and land cover data were also taken into consideration.We found that certain factors are closely correlated,e.g.the settlement density linearly decreases with elevation,while the characteristic settlement area shows an exponential increase upwards.The population density is not related to absolute elevation,but it is in close correlation with height（i.e.elevation relative to the local minimum）.Population change and illiteracy are also topography-related social factors.On the contrary,the variable ethnic pattern of Montenegro is influenced by historical,political and economic effects rather than by environmental factors or topographic features.As a conclusion we state that in the scale of a country or a region,the environment can strongly impact some social factors. 相似文献