Oceanic sound channels around New Zealand     

D. M. Garner 《新西兰海洋与淡水研究杂志》2013,47(1):3-15

Configuration of major sound channels in the ocean around New Zealand is derived from the temperature and salinity data available from the region between latitudes 28°S and 56°S and between 158°E and 174°W. The “SOFAR channel” is established throughout the area northwards of the Antarctic Convergence, with its axis in a depth of about 1,300 m. Little variation in the depth of this axis was found except in the southern part of the subantarctie zone, where the weak vertical temperature stratification cannot maintain a velocity minimum; the axis of the SOFAR channel tends to decrease in depth as it loses its identity. In the northern part of the subantarctie region, a second channel was found at a depth of about 100 m. The depth of the axis of this “subantarctie channel” increases to about 500 m under the surface outcrop of the Subtropical Convergence. It loses its identity at about 400 m in the stronger vertical temperature stratification of the subtropical region. To the south of the Antarctic Convergence, an “antarctic channel” was found with its axis at a depth of some 400 m in a temperature inversion between Antarctic Winter Water and the underlying Pacific Deep Water.

Sound velocity on the surfaces defined by the channel axes is mapped. A ridge of maximum SOFAR velocity is defined extending east and west of the northern part of New Zealand. This feature does not seem to appear in the north Pacific and has been tentatively associated with the dynamics of east‐flowing subtropical currents in this region.  相似文献   

基于极化散射特征的极化合成孔径雷达海冰分类方法研究:以渤海海冰分类为例   总被引：4，自引：2，他引：2  

张晰  张杰  孟俊敏  苏腾飞  刘眉洁 《海洋学报》2013,35(5):95-101

海冰监视监测的关键是提取海冰类型,准确提取海冰类型对于评估海冰冰情、保证航海及海洋作业安全具有重要的意义。利全极化合成孔径雷达影像(SAR)的优势,提取海冰的极化散射特征;在此基础上结合二叉树分类思想,开展极化SAR海冰类型的分类算法研究,提高SAR海冰分类精度;与传统的海冰分类方法相比较,验证了本方法的有效性。  相似文献   

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  

LI Qun  ZHANG Zhanhai  WU Huiding 《海洋学报(英文版)》2013,32(3):54-62

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   

Severe winter weather as a response to the lowest Arctic sea-ice anomalies     

CHEN Hongxi  LIU N  ZHANG Zhanhai 《海洋学报(英文版)》2013,32(10):11-15

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   

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  

王钰涵  李辉  任慧龙  单鹏昊 《海洋工程》2013,31(4):68-73

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   

Wave–ice interactions in the marginal ice zone. Part 2: Numerical implementation and sensitivity studies along 1D transects of the ocean surface     

《Ocean Modelling》2013

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   

Fracture patterns at lava–ice contacts on Kokostick Butte, OR, and Mazama Ridge, Mount Rainier, WA: Implications for flow emplacement and cooling histories   总被引：1，自引：1，他引：0  

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   

Interrogating the time and processes of development of the Las Liebres rock glacier,central Chilean Andes,using a numerical flow model          下载免费PDF全文

Sébastien Monnier  Christophe Kinnard 《地球表面变化过程与地形》2016,41(13):1884-1893

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   

Evaluation of Arctic Sea Ice Drift and its Relationship with Near-surface Wind and Ocean Current in Nine CMIP6 Models from China     

Xiaoyong YU  Chengyan LIU  Xiaocun WANG  Jian CAO  Jihai DONG  Yu LIU 《大气科学进展》2022,39(6):903-926

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   

高含冰(水)量冻土的单轴抗压强度变化特性研究     

杜海民  张淑娟  马巍 《冰川冻土》2014,36(5):1213-1219

沿用已有的制样方法, 在统一了制样过程中冰、水比例及冰颗粒尺寸的基础上, 开展了高含冰(水)量粉质砂土的单轴抗压强度系统性测试. 结果表明: 高含冰(水)量冻土的单轴抗压强度随应变率的增加而非线性增大; 随温度升高而减小, 减小趋势与总含水量有关. 随含水量的增加, 强度先是非线性增大, 然后逐渐趋于重塑冰的强度, 这有别于早期类似研究的结果. 同时, 也对试样中加入冰颗粒以保证试样高含冰(水)量的制备方法合理性产生了质疑.  相似文献