An ice-core based history of Siberian forest fires since AD 1250     

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   

Eastern Himalayan alpine plant ecology,Tibetan ethnobotany,and climate change     

Jan Salick  Anja Byg 《Global Environmental Change》2009,19(2):147-155

Tibetan culture and livelihoods depend on native plants for medicine, food, grazing, wood, as well as cash from market sales. The Medicine Mountains (part of the Hengduan Mountains) of the eastern Himalayas, with tremendous plant diversity derived from steep gradients of both elevation and precipitation, have traditionally been an important source of Tibetan medicinal plants. We examine climate change in this area and vegetation patterns influenced by biogeography, precipitation and elevation (NMS and CCA ordinations of GLORIA plots). The Alpine environment has the highest plant diversity and most useful plants and is the most susceptible to climate change with impacts on traditional Tibetan culture and livelihoods—particularly Tibetan medicine and herding.  相似文献   

Tsunami imprints on the Leeward Netherlands Antilles (Aruba, Curaçao, Bonaire) and their relation to other coastal problems     

Anja Scheffers 《Quaternary International》2004,120(1):163

Tsunami are one of the major natural hazards in the Caribbean. The historical record lists 88 tsunami, from local events to teletsunami, in the time period from 1489 to 1998. This study focuses on the spatial distribution and geomorphologic evidence related to coarse littoral sediment and boulder deposition by tsunami events of Holocene age in the Southern Caribbean. At a worldwide scale, these debris deposits represent the most extensive and impressive records of Holocene paleo-tsunami so far studied. Hitherto, the Leeward Lesser Antilles, consisting of the islands of Aruba, Curaçao and Bonaire, were not known to have had tsunami affecting their coastlines. The possible contribution of tsunami to configuring coastlines (e.g. the questions of embayment development, the coastal environment changes, and the absence of Holocene fringing reefs along the windward coasts) is discussed.  相似文献   

Small-Scale Variability in the Coastal Atmospheric Boundary Layer     

Branko Grisogono  Linda Ström  Michael Tjernström 《Boundary-Layer Meteorology》1998,88(1):23-46

The influence of the main large-scale wind directions on thermally driven mesoscale circulations at the Baltic southwest coast, southeast of Sweden, is examined. The aim of the study is to highlight small-scale alterations in the coastal atmospheric boundary layer. A numerical three-dimensional mesoscale model is used in this study, which is focused on an overall behaviour of the coastal jets, drainage flows, sea breezes, and a low-level eddy-type flow in particular. It is shown that synoptic conditions, together with the moderate terrain of the southeast of Sweden (max. height h₀ 206 m), governs the coastal mesoscale dynamics triggered by the land-sea temperature difference T. The subtle nature of coastal low-level jets and sea breezes is revealed; their patterns are dictated by the interplay between synoptic airflow, coastline orientation, and T.The simulations show that coastal jets typically occur during nighttime and vary in height, intensity and position with respect to the coast; they interact with downslope flows and the background wind. For the assigned land surface temperature (varying ±8 K from the sea temperature) and the opposing constant geostrophic wind 8 m s^-1, the drainage flow is more robust to the opposing ambient flow than the sea breeze later on. Depending on the part of the coast under consideration, and the prevailing ambient wind, the sea breeze can be suppressed or enhanced, stationary at the coast or rapidly penetrating inland, locked up in phase with another dynamic system or almost independently self-evolving. A low-level eddy structure is analyzed. It is governed by tilting, divergence and horizontal advection terms. The horizontal extent of the coastal effects agrees roughly with the Rossby radius of deformation.  相似文献   

A Comparison of the Sequential Gaussian and Markov-Bayes Simulation Methods for Small Samples     

Anja Kannengieser Fredericks  Ken B. Newman 《Mathematical Geology》1998,30(8):1011-1032

We compared the performance of sequential Gaussian simulation (sGs) and Markov-Bayes simulation (MBs) using relatively small samples taken from synthetic datasets. A moderate correlation (approximately r = 0.70) existed between a continuous primary variable and a continuous secondary variable. Given the small sample sizes, our objective was to determine whether MBs, with its ability to incorporate the secondary information, would prove superior to SgS. A split-split-plot computer experiment was conducted to compare the two simulation methods over a variety of primary and secondary sample sizes as well as spatial correlations. Using average mean square prediction error as a measure of local performance, sGs and MBs were roughly equivalent for random fields with short ranges (2 m). As range increased (15 m) the average mean square prediction error for sGs was less than or equal to that for MBs, even when number of noncollocated secondary observations was twice the number of collocated observations. Median variance within nonoverlapping subregions was used as a measure of the local heterogeneity or surface texture of the image. In most situations sGs images more faithfully reflected the true local heterogeneity, while MBs was more erratic, sometimes oversmoothing and sometimes undersmoothing.  相似文献   

A Fully Depleted pn-Junction CCD for Infrared-, UV- and X- ray detection     

C. von Zanthier  H. Bräuninger  K. Dennerl  R. Hartmann  G. Hartner  H. Hippmann  A. Kaltenberger  E. Kastelic  W. Kink  N. Krause  N. Meidinger  G. Metzner  E. Pfeffermann  M. Popp  C. Reppin  J. Riedl  D. Stötter  L. Strüder  J. Trümper  W. Weber  D. Carathanassis  S. Engelhard  Th. Gebhart  D. Hauff  G. Lutz  R. H. Richter  H. Seitz  P. Solc  E. Biehler  H. Böttcher  E. Kendziorra  J. Krämer  B. Pflüger  R. Staubert  P. Holl  J. Kemmer  P. Lechner  B. Maier  H. Soltau  R. Stötter  E. Bihler 《Experimental Astronomy》1998,8(1):89-96

This paper describes the performance of the Fully Depleted pn-junction CCD (pn-CCD) system, developed for ESA's XMM-satellite mission for soft x-ray imaging and spectroscopy in the single photon counting mode in the 100 eV to 10 keV photon range. The 58 mm x 60 mm large pn-CCD array, designed and fabricated at the Semiconductor Lab (Halbleiterlabor) of the Max-Planck-Institut, uses pn-junctions for registers and as backside structure. This concept naturally enables full depletion of the detector volume independent of the silicon wafer's resistivity and thickness, and as such make it an efficient detector for the x-ray region and the infrared. For high detection efficiency in the soft x-ray region and UV, an ultrathin pn-CCD backside deadlayer has been realized. Each pn-CCD-channel is equipped with its own on-chip JFET amplifier which, in combination with the CAMEX-amplifier and multiplexing chip, facilitates parallel readout and fast data rate: the cooled pn-CCD system can be read out at a data rate up to 3 MHz with an electronic noise floor of ENC < 5 e-.  相似文献   

The ice winter of 1996/97 on the German coasts between ems and oder with a survey of the entire Baltic Area     

Klaus Strübing 《Ocean Dynamics》1996,48(2):185-195

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The drainage pattern of Hansbreen and Werenskioldbreen, two polythermal glaciers in Svalbard   总被引：2，自引：0，他引：2  

Anja Pälli  John C. Moore  Jacek Jania  Leszek Kolondra  Piotr Glowacki 《Polar research》2003,22(2):355-371

To improve our understanding of Svalbard-type polythermal glacier drainage, hydraulic geometry models of the subglacial hydrology of two contrasting glaciers in Svalbard have been constructed. The models are tested against a uniquely long and rich set of field observations spanning 45 years. Digital elevation models (DEMs) were constructed from bedrock data measured with ground penetrating radar and surface data of two medium-sized polythermal glaciers, Hansbreen and Werenskioldbreen, in south-west Spitsbergen. Hansbreen has a low angle bed with over-deepenings and a calving front, while Werenskioldbreen has steeper bed and terminates on land. Together they are representative of many Svalbard glaciers. The DEMs were used to derive maps of hydraulic potential and subglacial drainage networks. Validation of the models was done using field observations including location mapping and speleological exploration of active moulins, positions of main river outflows, dyetracing and water chemistry studies, and observations of water pressure inside moulins. Results suggest that the water pressure is generally close to ice overburden pressure but varies greatly depending on local conditions such as bed location, the thickness of cold ice layer, the thickness of the glacier and seasonal changes in meltwater input.  相似文献   

Holocene paleoenvironmental change inferred from two sediment cores collected in the Tibetan lake Taro Co     

Laug  Andreas  Haberzettl  Torsten  Pannes  Andre  Schwarz  Anja  Turner  Falko  Wang  Junbo  Engels  Stefan  Rigterink  Sonja  Börner  Nicole  Ahlborn  Marieke  Ju  Jianting  Schwalb  Antje 《Journal of Paleolimnology》2021,66(3):171-186

Journal of Paleolimnology - The Tibetan Plateau, also known as the “Water Tower of Asia” because of its function as a water storage and supply region, responds dramatically to modern...  相似文献   

Abundance and size distribution of transparent exopolymer particles (TEP) in a coccolithophorid bloom in the northern Bay of Biscay     

Jérôme Harlay  Caroline De Bodt  Anja Engel  Sandra Jansen  Quentin d’Hoop  Judith Piontek  Nicolas Van Oostende  Steve Groom  Koen Sabbe  Lei Chou 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(8):1251-1265

The distribution of transparent exopolymer particles (TEP) was investigated during a coccolithophorid bloom in the northern Bay of Biscay (North Atlantic Ocean) in early June 2006. MODIS chlorophyll-a (Chl-a) and reflectance images before and during the cruise were used to localize areas of important biological activity and high reflectance (HR). TEP profiles along the continental margin, determined using microscopic (TEP_micro) and colorimetric (TEP_color) methods, showed abundant (6.1×10⁶–4.4×10⁷ L^?1) and relatively small (0.5–20 μm) particles, leading to a low total volume fraction (0.05–2.2 ppm) of TEP_micro and similar vertical profiles of TEP_color. Estimates of carbon content in TEP (TEP-C) derived from the microscopic approach yielded surface concentration of 1.50 μmol C L^?1. The contribution of TEP-C to particulate organic carbon (POC) was estimated to be 12% (molar C ratio) during this survey. Our results suggest that TEP formation is a probable first step to rapid and efficient export of C during declining coccolithophorid blooms.  相似文献