Estimation of extreme wave heights using GEOSAT measurements     

Vijay Panchang  Liuzhi Zhao  Z. Demirbilek 《Ocean Engineering》1998,26(3):205-225

Satellite technology has yielded a large database of global ocean wave heights which may be used for engineering applications. However, the sampling protocol used by the satellite leads to some difficulties in making use of these data for practical applications. These difficulties and techniques to estimate extreme wave heights using satellite measurements are discussed. Significant wave heights for a 50-year return period are estimated using GEOSAT measurements for several regions around North America. Techniques described here may be used for estimation of wave heights associated with any specified return interval in regions where buoy data are not readily available.  相似文献   

生态模型在渔业管理中的应用   总被引：2，自引：1，他引：1  

张崇良  陈勇  韩东燕  邢磊  任一平 《海洋学报》2017,39(10):1-18

随着人们对于海洋生态的认识逐渐深入,渔业等人类活动的影响受到了更多的关注,"基于生态系统的渔业管理"（EBFM）这一概念被越来越多的研究者和国际组织所接受。生态模型为EBFM的实践提供了科学的评估方法和技术工具。与单鱼种评估模型相比,生态模型更多地考虑了系统内的各种生态过程和作用机制,栖息地等环境条件的变化,以及生态系统整体的结构和功能等,依此来反映生态系统的动态变化。由于生态模型是多样化的,关注和涉及不同的目标对象、机制过程、模型结构和参数,本文按照生态模型所关注的生态层次和组分将其分为多物种模型、群落结构模型和生态系统模型3个类型,分析了各类模型的优劣点。本文进一步阐述了生态模型在渔业管理中的应用领域,以管理策略评估为中心的应用方式,以及实践中模型选择和构建所需要注意的问题,还探讨了生态模型中降低不确定性和提高预测能力的方法。  相似文献   

High-resolution streamflow trend analysis applicable to annual decision calendars: a western United States case study   总被引：1，自引：0，他引：1  

Jong-Suk Kim  Shaleen Jain 《Climatic change》2010,102(3-4):699-707

Changes in the seasonality of streamflow in the western United States have important implications for water resources management and the wellbeing of coupled human-natural systems. An assessment of changes in the timing and magnitude of streamflow resolved at fine time scales (days to weeks and seasons) is highly relevant to adaptive management strategies that are responsive to changing hydrologic baselines. In this paper, we present a regional analysis of the changes in streamflow seasonality through a broad classification of streams and quantification of increases and decreases in flow, based on a quantile regression methodology. This analysis affords a useful research product to examine the diversity of trends across seasons for individual streams. The trend analysis methodology can identify windows of change, thus revealing vulnerabilities within decision calendars and species lifecycles, an important consideration for adaptation and mitigation efforts.  相似文献   

我国海洋绿潮生态动力学研究进展   总被引：2，自引：0，他引：2  

刘桂梅  李海  王辉  柴扉 《地球科学进展》2010,25(2):147-153

在近几年我国绿潮生态学研究的基础上,回顾了绿潮藻生活史,温度、盐度、光强和营养盐等对其生态行为的影响,以及绿潮成因、溯源和海洋生态模型方面取得的新进展。在现阶段取得的主要研究进展基础上,提出今后我国绿潮研究及其发展趋势应侧重于建立并完善海洋生态环境立体监测和观测系统,开展针对海洋绿潮问题的综合性研究,开发业务化的绿潮生态动力学数值预报预警系统。  相似文献   

Exploring former subglacial Hodgson Lake,Antarctica Paper I: site description,geomorphology and limnology     

Dominic A. Hodgson  Stephen J. Roberts  Michael J. Bentley  James A. Smith  Joanne S. Johnson  Elie Verleyen  Wim Vyverman  Andy J. Hodson  Melanie J. Leng  Andreas Cziferszky  Adrian J. Fox  David C.W. Sanderson 《Quaternary Science Reviews》2009,28(23-24):2295-2309

  相似文献   

The sensitivity of a 3D biogeochemical-like tracer model to advection schemes   总被引：1，自引：0，他引：1  

Guimei  Huijie Xue 《Ocean Modelling》2009,29(4):234-247

Multidimensional Positive Definite Advection Transport Algorithm (MPDATA) and Monotonic Upstream Schemes for Conservation Laws (MUSCL) are compared and evaluated in a biogeochemical-like tracer model. Based on the MUSCL scheme, an adapted scheme for σ-coordinate models (MUSCL_VD) is presented. These schemes are first implemented in idealized experiments configured for a closed channel with and without a seamount, and conservation is confirmed. MUSCL_VD and MUSCL generate the same results in the flat bottom case, while MUSCL_VD is the only scheme that avoids unphysical values in the seamount experiments. When implemented in a three-dimensional model of the Gulf of Maine (GoM) with realistic topography and real-time forcing, the modeled distributions of an inert tracer concentration are sensitive to the advection schemes. The experiment with MUSCL shows persistent overshoots. MPDATA and MUSCL_VD produce similar spatial distributions and seasonal cycles with MUSCL_VD being slightly more diffusive in the horizontal and less so in the vertical. These two schemes are about equally efficient in computation.  相似文献   

Coupling of deformation and reactions during mid-crustal shear zone development: an in situ frictional–viscous transition     

J. H. MARSH  S. E. JOHNSON  M. G. YATES  D. P. WEST JR 《Journal of Metamorphic Geology》2009,27(8):531-553

A well preserved strain and reaction gradient records the progressive transformation of a megacrystic Kfs+Cpx+Opx+Bt₁±Qtz syenitic pluton to a strongly sheared Kfs+Act+Bt₂+Ab+Qtz tectonite within the exhumed Norumbega Fault System, Maine, USA. Detailed microstructural analysis indicates that fracturing and localized fluid infiltration initiated the deconstruction of the existing K-feldspar and two-pyroxene load-bearing framework, and that feedback among metamorphic reactions, fabric development and enhanced permeability during progressive shearing led to the development of an interconnected, biotite- and actinolite-rich foliation. The activation of dislocation creep in biotite and quartz, and dissolution–precipitation creep in actinolite and feldspar, with increasing strain ultimately resulted in a transition from dominantly frictional to dominantly viscous deformation processes. Petrological data show that various scales of geochemical disequilibrium exist across the strain and reaction gradient, and that reaction progress was limited by slow chemical diffusion during the early stages of deformation. Petrological modelling results indicate that the existing plutonic assemblage was metastable at mid-crustal conditions, and that fluid infiltration and deformation allowed the product assemblage to advance towards chemical equilibration. Comparison of the observed microstructures and deformation mechanisms with experimental and numerical modelling results suggest that the development of an interconnected biotite-dominated fabric probably caused a major (up to three fold) reduction in bulk rock strength and localization of strain into the foliated margin.  相似文献   

Inactive and relict rock glaciers of the Deboullie Lakes Ecological Reserve,northern Maine,USA     

Aaron E. Putnam  David E. Putnam 《第四纪科学杂志》2009,24(7):773-784

Lobate talus slopes in the Deboullie Lakes Ecological Reserve (DLER) of northern Maine exhibit parabolic profiles characteristic of inactive and relict talus‐derived rock glaciers. Vegetated rock glacier surfaces suggest that the landforms are no longer active, and lobes comprising two DLER rock glaciers document periods of past growth. Observations of perennial subsurface ice are supported by datalogger temperature measurements, indicating that sporadic permafrost exists throughout the DLER. We compare the DLER rock glaciers, along with similar features elsewhere in New England and adjacent Québec, to the modern alpine permafrost distribution. Results indicate that a mean annual temperature cooling of ～6°C is required to promote active rock glacier growth. Ages of plant remains recovered from the basal sediments of a local pond constrain deglaciation to before 11 320 ¹⁴C a BP, and core stratigraphy and organic content reveal that a periglacial environment persisted during the early postglacial era. Thus, we hypothesise that the DLER rock glaciers were active during Lateglacial time despite the lack of glacier activity in the region. We take this to suggest that north‐eastern US rock glaciers formed in response to mean annual temperatures skewed towards the frigid winters of the Younger Dryas chronozone. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Building blocks from an old brickyard     

《Quaternary Science Reviews》2007,26(9-10):1194-1196

  相似文献   

Holocene climate and environmental history of East Greenland inferred from lake sediments     

Amanda R. Lusas  Brenda L. Hall  Thomas V. Lowell  Meredith A. Kelly  Ole Bennike  Laura B. Levy  William Honsaker 《Journal of Paleolimnology》2017,57(4):321-341

Prediction of future Arctic climate and environmental changes, as well as associated ice-sheet behavior, requires placing present-day warming and reduced ice extent into a long-term context. Here we present a record of Holocene climate and glacier fluctuations inferred from the paleolimnology of small lakes near Istorvet ice cap in East Greenland. Calibrated radiocarbon dates of organic remains indicate deglaciation of the region before ~10,500 years BP, after which time the ice cap receded rapidly to a position similar to or less extensive than present, and lake sediments shifted from glacio-lacustrine clay to relatively organic-rich gyttja. The lack of glacio-lacustrine sediments throughout most of the record suggests that the ice cap was similar to or smaller than present throughout most of the Holocene. This restricted ice extent suggests that climate was similar to or warmer than present, in keeping with other records from Greenland that indicate a warm early and middle Holocene. Middle Holocene magnetic susceptibility oscillations, with a ~200-year frequency in one of the lakes, may relate to solar influence on local catchment processes. Following thousands of years of restricted extent, Istorvet ice cap advanced to within 365 m of its late Holocene limit at ~AD 1150. Variability in the timing of glacial and climate fluctuations, as well as of sediment organic content changes among East Greenland lacustrine records, may be a consequence of local factors, such as elevation, continentality, water depth, turbidity, and seabirds, and highlights the need for a detailed spatial array of datasets to address questions about Holocene climate change.  相似文献