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941.
942.
Interaction of an anticyclonic eddy with sea ice in the western Arctic Ocean: an eddy-resolving model study 总被引:1,自引:0,他引:1
The dramatic decline of summer sea ice extent and thickness has been witnessed in the western Arctic Ocean in recent decades, which hasmotivated scientists to search for possible factors driving the sea ice variability. An eddy-resolving, ice-ocean coupled model covering the entire Arctic Ocean is implemented, with focus on the western Arctic Ocean. Special attention is paid to the summer Alaskan coastal current (ACC), which has a high temperature (up to 5℃ ormore) in the upper layer due to the solar radiation over the open water at the lower latitude. Downstream of the ACC after Barrow Point, a surface-intensified anticyclonic eddy is frequently generated and propagate towards the Canada Basin during the summer season when sea ice has retreated away from the coast. Such an eddy has a warm core, and its source is high-temperature ACC water. A typical warm-core eddy is traced. It is trapped just below summer sea ice melt water and has a thickness about 60 m. Temperature in the eddy core reaches 2-3℃, and most water inside the eddy has a temperature over 1℃. With a definition of the eddy boundary, an eddy heat is calculated, which can melt 1 600 km2 of 1mthick sea ice under extreme conditions. 相似文献
943.
Possible impact of reduced Arctic sea-ice on winter severe weather in China is investigated regarding the snowstorm over southern China in January 2008. The sea-ice conditions in the summer (July-September) and fall (September-November) of 2007 show that the sea-ice is the lowest that year. During the summer and fall of 2007, sea ice displayed a significant decrease in the East Siberian, the northern Chukchi Sea, the western Beaufort Sea, the Barents Sea, and the Kara Sea. A ECHAM5.4 atmospheric general circula- tion model is forced with realistic sea-ice conditions and strong thermal responses with warmer surface air temperature and higher-than-normal heat flux associated with the sea-ice anomalies are found. The model shows remote atmospheric responses over East Asia in January 2008, which result in severe snowstorm over southern China. Strong water-vapor transported from the Bay of Bengal and from the Pacific Ocean related to Arctic sea-ice anomalies in the fall (instead of summer) of 2007 is considered as one of the main causes of the snowstorm formation. 相似文献
944.
连续破冰模式下破冰船的冰力研究 总被引:4,自引:1,他引:3
由于破冰船航行区域及工作任务的特殊性,对于海冰与船体的相互作用越来越受到重视。在一定理想化假设的基础上对破冰船在直行情况下的连续破冰模式运用数值方法进行模拟,然后得到破冰船破冰过程中的冰力时历曲线,并分析了相关破冰参数对连续破冰作用下破冰形状及平均冰力的影响程度。模拟结果表明:冰厚、破冰速度与离散间隔都对破冰半径和冰力有一定的影响;而冰厚则是影响破冰形状及冰力最为关键的因素;得到的连续破冰形状基本符合实际,可以为后续研究破冰船在冰区航行时的运动及破冰能力提供基础。 相似文献
945.
The theoretical foundation of a wave–ice interaction model is reported in Part 1 of this study. The model incorporates attenuation of ocean surface waves by sea ice floes and the concomitant breaking of the floes by waves that determines the structure of the marginal ice zone (MIZ). A numerical implementation of the method is presented here. Convergence of the numerical method is demonstrated, as temporal and spatial grids are refined. A semi-analytical method, which does not require time-stepping, is also developed to validate the numerical results, when dispersion is neglected. The wave energy lost during ice breakage is parameterized, as part of the numerical method. Sensitivity studies are conducted in relation to the energy loss and also dispersive effects, the choice of the attenuation model, the properties of the wave field, and sea ice properties such as concentration, thickness and breaking strain. Example simulations intended to represent conditions in the Fram Strait in 2007, which exploit reanalyzed wave and ice model data, are shown to conclude the results section. These are compared to estimates of MIZ widths based on a concentration criteria, and obtained from remotely-sensed passive microwave images. 相似文献
946.
Robert W.D. Lodge David T. Lescinsky 《Journal of Volcanology and Geothermal Research》2009,185(4):298-310
Cooling lava commonly develop polygonal joints that form equant hexagonal columns. Such fractures are formed by thermal contraction resulting in an isotropic tensional stress regime. However, certain linear cooling fracture patterns observed at some lava–ice contacts do not appear to fit the model for formation of cooling fractures and columns because of their preferred orientations. These fracture types include sheet-like (ladder-like rectangular fracture pattern), intermediate (pseudo-aligned individual column-bounding fractures), and pseudopillow (straight to arcuate fractures with perpendicular secondary fractures caused by water infiltration) fractures that form the edges of multiple columns along a single linear fracture. Despite the relatively common occurrence of these types of fractures at lava–ice contacts, their significance and mode of formation have not been fully explored. This study investigates the stress regimes responsible for producing these unique fractures and their significance for interpreting cooling histories at lava–ice contacts.Data was collected at Kokostick Butte dacite flow at South Sister, OR, and Mazama Ridge andesite flow at Mount Rainier, WA. Both of these lava flows have been interpreted as being emplaced into contact with ice and linear fracture types have been observed on their ice-contacted margins. Two different mechanisms are proposed for the formation of linear fracture networks. One possible mechanism for the formation of linear fracture patterns is marginal bulging. Melting of confining ice walls will create voids into which flowing lava can deform resulting in margin-parallel tension causing margin-perpendicular fractures. If viewed from the ice-wall, these fractures would be steeply dipping, linear fractures. Another possible mechanism for the formation of linear fracture types is gravitational settling. Pure shear during compression and settling can result in a tensional environment with similar consequences as marginal inflation. In addition to this, horizontally propagating cooling fractures will be directly influenced by viscous strain caused by the settling of the flow. This would cause preferential opening of fractures horizontally, resulting in vertically oriented fractures.It is important to note that the proposed model for the formation of linear fractures is dependent on contact with and confinement by glacial ice. The influence of flow or movement on cooling fracture patterns has not been extensively discussed in previous modeling of cooling fractures. Rapid cooling of lava by the interaction with water and ice will increase the ability to the capture and preserve perturbations in the stress regime. 相似文献
947.
盐穴储气库破坏后地表沉陷规律数值模拟研究 总被引:3,自引:0,他引:3
地下盐穴储气库在天然气调峰和保障供气安全上具有不可替代的作用。地下盐穴储气库达到设计年限后,将报废而逐步垮塌,必然引起严重的地表沉陷。因此,对盐穴储气库破坏后地表沉陷规律进行研究具有十分重要的意义。考虑到目前的数值分析软件进行地表沉陷分析的不足,开发了用于盐穴储气库破坏后地表沉陷数值模拟的有限元专用软件-2D-Sink,该软件具有处理破碎岩块的能力。应用2D-Sink对盐穴储气库破坏后引起的地表沉陷规律进行了系统的研究,共建立了6种模型进行数值模拟,分别研究了地表沉陷层理效应、地表沉陷的岩层倾斜效应、地表沉陷的断层效应和多盐穴地表沉陷规律。对多溶腔地表变形曲线与单溶腔叠加的地表变形曲线进行比较,验证了地表沉陷叠加原理的正确性。研究成果为盐穴储气库报废后地表沉陷灾害控制提供了理论基础。 相似文献
948.
Interrogating the time and processes of development of the Las Liebres rock glacier,central Chilean Andes,using a numerical flow model
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The Las Liebres rock glacier is a large (~2.2 km long) Andean rock glacier whose internal composition and kinematics are known from previous studies. We investigate its development by posing and testing the following null hypothesis: the rock glacier has developed from a constant supply of debris and ground ice in periglacial conditions and resulting creep of the ice‐rock mixture. A rheological model was formulated based on recent advances in the study of ice‐rock mixture rheology, and calibrated on the known surface velocities and internal composition of the rock glacier. We show that the rock glacier viscosity is inversely related to both water and debris fractions, in agreement with recent field and theoretical studies of ice‐rock mixture rheology. Taking into account the possible variations in water fraction, the model was used to estimate the time spans of development (0.91–7.11 ka), rates of rock wall retreat (0.44–4.18 mm/a), and rates of ground ice formation (0.004–0.026 m/a) for the rock glacier. These results support the null hypothesis of a periglacial origin of the Las Liebres rock glacier. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
949.
The simulated Arctic sea ice drift and its relationship with the near-surface wind and surface ocean current during 1979-2014 in nine models from China that participated in the sixth phase of the Coupled Model Intercomparison Project(CMIP6)are examined by comparison with observational and reanalysis datasets.Most of the models reasonably represent the Beaufort Gyre(BG)and Transpolar Drift Stream(TDS)in the spatial patterns of their long-term mean sea ice drift,while the detailed location,extent,and strength of the BG and TDS vary among the models.About two-thirds of the models agree with the observation/reanalysis in the sense that the sea ice drift pattern is consistent with the near-surface wind pattern.About the same proportion of models shows that the sea ice drift pattern is consistent with the surface ocean current pattern.In the observation/reanalysis,however,the sea ice drift pattern does not match well with the surface ocean current pattern.All nine models missed the observational widespread sea ice drift speed acceleration across the Arctic.For the Arctic basin-wide spatial average,five of the nine models overestimate the Arctic long-term(1979-2014)mean sea ice drift speed in all months.Only FGOALS-g3 captures a significant sea ice drift speed increase from 1979 to 2014 both in spring and autumn.The increases are weaker than those in the observation.This evaluation helps assess the performance of the Arctic sea ice drift simulations in these CMIP6 models from China. 相似文献
950.