冰激直立腿海洋平台疲劳寿命分析

由于渤海特殊环境条件与油藏分布决定了该海域导管架油气平台属于典型的柔性抗冰结构。多年现场观测发现,该类结构存在显著的冰激振动现象。冰振不仅能激起较大的甲板加速度响应,还会引起明显的导管架管节点交变应力。在结构设计与安全保障中进行疲劳分析及寿命估计是必要的。对于直立腿抗冰结构,精确的冰激疲劳寿命计算方法还不成熟。基于多年的现场监测,首先分析了冰与直立腿抗冰结构相互作用过程;其次,提出了冰激直立腿平台的疲劳寿命分析流程;最后,选取渤海某典型直立腿平台,利用ANSYS数值模拟,对比了稳态冰力和随机冰力下结构的疲劳损伤,进而计算出疲劳寿命。本研究为寒区柔性结构抗冰设计与安全保障提供了理论基础。     

CryoSat-2卫星海冰区域波形识别及海冰干舷高确定

利用40%阈值法对CryoSat-2卫星波形数据进行重跟踪,将波形特征参数和海冰浓度相结合,对海冰和Lead(浮冰之间的开阔水域)进行有效识别。利用沿轨前后搜索算法计算海冰干舷高,并引用AWI结果,绘制2011~2013年北冰洋多年冰区域和一年冰区域平均海冰干舷高变化趋势图。比较本文结果与AWI结果的各年同期数据,验证本文结果的可靠性。     

Microbial life in martian ice: A biotic origin of methane on Mars?

Despite the fact that microbial cells are unlikely to be found in the Martian soil in the near future, this paper is written on the assumption that some of the seasonally varying concentration of Martian methane is due to ongoing methanogenesis. It is first pointed out that life might have arisen on Mars first and been transported to Earth later. A case is made that an icy origin of life is more likely than a hot origin, especially if biomolecules take advantage of the high encounter rates and stability against hydrolysis, and that microorganisms feed on the ions that comprise eutectic solutions in ice. Although certain difficulties are avoided if RNA and DNA grow while adsorbed on clay grains, double strand-breaks of microbial DNA due to alpha radioactivity are a far greater threat to microbial survival on clay or other rock types than in ice. Developing a relation between the rate of microbial metabolism in ice and the experimentally determined rate of production of trapped gases of microbial origin, one can estimate the concentration of methanogens that could account for the methane production rate as a function of temperature of their habitat. The result, of order 1 cell cm⁻³ in the Martian subsurface, seems an attainable goal provided samples are taken from at least 1 or 2 m below the hostile surface of Mars. Instruments on NASA’s 2011 Mars Science Lab will measure stable isotopes for methane, water, and carbon dioxide, which on Earth served to distinguish abiotic, thermogenic, and microbial origins. Future measurements of chirality of biomolecules might also provide evidence for Martian life.     

On the recent warming of the southeastern Bering Sea shelf

During the last decade, the southeastern Bering Sea shelf has undergone a warming of 3 °C that is closely associated with a marked decrease of sea ice over the area. This shift in the physical environment of the shelf can be attributed to a combination of mechanisms, including the presence over the eastern Bering Sea shelf of a relatively mild air mass during the winter, especially from 2000 to 2005; a shorter ice season caused by a later fall transition and/or an earlier spring transition; increased flow through Unimak Pass during winter, which introduces warm Gulf of Alaska water onto the southeastern shelf; and the feedback mechanism whereby warmer ocean temperatures during the summer delay the southward advection of sea ice during winter. While the relative importance of these four mechanisms is difficult to quantify, it is evident that for sea ice to form, cold arctic winds must cool the water column. Sea ice is then formed in the polynyas during periods of cold north winds, and this ice is advected southward over the eastern shelf. The other three mechanisms can modify ice formation and melt, and hence its extent. In combination, these four mechanisms have served to temporally and spatially limit ice during the 5-year period (2001–2005). Warming of the eastern Bering Sea shelf could have profound influences on the ecosystem of the Bering Sea—from modification of the timing of the spring phytoplankton bloom to the northward advance of subarctic species and the northward retreat of arctic species.     

Periglacial climate at the 2.5 Ma onset of Northern Hemisphere glaciation inferred from the Whippoorwill Formation, northern Missouri, USA

The Whippoorwill Formation is a gleyed diamicton that is present locally within bedrock depressions beneath the oldest glacial till in northern Missouri, USA. Stratigraphy, paleomagnetism, and cosmogenic-nuclide burial ages show that it was deposited between the Matuyama-Gauss magnetostratigraphic boundary at 2.58 Ma and the first advance of the Laurentide ice sheet into Missouri at 2.47 ± 0.19 Ma. High cosmogenic-nuclide concentrations also show that the constituents of the Whippoorwill Formation experienced long exposure at a stable landscape surface with erosion rates of 1-2 m/Ma. However, cosmogenic-nuclide concentrations are invariant with depth below the Whippoorwill Formation surface, indicating active mixing of the soil profile shortly before burial by till. The Whippoorwill Formation retains numerous features indicative of cryoturbation. Therefore, we interpret it as a buried Gelisol, a soil formed under periglacial conditions in the presence of permafrost. At the onset of Northern Hemisphere glaciation, climate cooling established permafrost conditions and accelerated erosion by inducing landscape instability. Thus, weathered regolith materials were mobilized and redeposited by gelifluction shortly before the ice sheet overrode the landscape.     

基于GPS反射信号的岸基海冰探测的研究

本文论述了全球导航卫星系统反射信号测量（GNSS-R）在海冰介电常数和海冰密集程度方面的潜在的研究价值,对欧洲空间局在格林兰岛迪斯科海岸采集的海冰数据进行分析,处理了两种反射信号的幅度的量化关系,同时跟踪多颗GNSS卫星并且保证了数据处理时间的连续性和有效性。根据双极化反射信号的幅度极化比和模拟海冰表面复介电常数得出结论, 幅度极化比和海冰表面的介电常数变化有联系。     

Greenland Ice Sheet surface melt: A review

Surface melt has great impacts on the Greenland Ice Sheet （GrlS） mass balance and thereby has become the focus of significant GrlS research in recent years. The production, transport, and release processes of surface meltwater are the keys to understanding the poten- tial impacts of the GrlS surface melt. These hydrological processes can elucidate the following scientific questions： How much melt- water is produced atop the GrlS？ What are the characteristics of the meltwater-formed supraglacial hydrological system？ How does the meltwater influence the GrlS motion？ The GrlS supraglacial hydrology has a number of key roles and yet continues to be poorly understood or documented. This paper summarizes the current understanding of the GrlS surface melt, emphasizing the three essential supraglacial hydrological processes： （1） meltwater production： surface melt modeling is an important approach to acquire surface melt information, and areas, depths, and volumes of supraglacial lakes extracted from remotely sensed imagery can also provide surface melt information; （2） meltwater transport： the spatial distributions of supraglacial lakes, supraglacial sarams, moulins, and crevasses demonstrate the characteristics of the supraglacial hydrological system, revealing the meltwater transport process; and （3） meltwater release： the release of meltwater into the englacial and the subglacial ice sheet has important but undetermined impacts on the GrlS motion. The correlation between surface runoff and the GrlS motion speed is employed to understand these influences.     

Sea ice volume and age: Sensitivity to physical parameterizations and thickness resolution in the CICE sea ice model

New dynamics parameterizations in Version 5 of the Los Alamos Sea Ice Model, CICE, feature an anisotropic rheology and variable drag coefficients. This study investigates their effect on Arctic sea ice volume and age simulations, along with the effects of several pre-existing model options: a parameter that represents the mean cumulative area of ice participating in ridging, the resolution of the ice thickness distribution, and the resolution of the vertical temperature and salinity profiles.By increasing shear stress between floes, the anisotropic rheology slows the ice motion, producing a thicker, older ice pack. The inclusion of variable drag coefficients, which depend on modeled roughness elements such as deformed ice and melt pond edges, leads to thinner ice and a more realistic simulation of sea ice age. Several feedback processes act to enhance differences among the runs. Notably, if less open water is produced mechanically through ice deformational processes, the simulated ice thins relative to runs with more mechanically produced open water. Thermodynamic processes can have opposing effects on ice age and volume; for instance, growth of new ice increases the volume while decreasing the age of the pack. Therefore, age data provides additional information useful for differentiating among process parameterization effects and sensitivities to other model parameters.Resolution of thicker ice types is crucial for proper modeling of sea ice volume, because the volume of ice in the thicker ice categories determines the total ice volume. Model thickness categories tend to focus resolution for thinner ice; this paper demonstrates that 5 ice thickness categories are not enough to accurately resolve the ice thickness distribution for simulations of ice volume.     

The seasonal foot printing mechanism of spring Arctic sea ice in the Bergen climate models

The influence of spring Arctic sea ice variability on the Pacific Decadal Oscillation(PDO) like sea surface temperature(SST) variability is established and investigated using an Atmosphere Ocean General Circulation Model(AOGCM) of the Bergen Climate Model version 2(BCM2). The spring Arctic sea ice variability affects the mid-latitudes and tropics through the propagation of the anomalous Eliassen-Palm(E-P) flux from the polar region to mid- and low-latitudes during boreal spring. The pathway includes anomalous upward wave activity, which propagates to the high troposphere from near the surface of the polar region, turns southward between 500 h Pa and 200 h Pa and extends downward between 50°N and 70°N, influencing the near surface atmospheric circulation. The alteration of the near surface atmospheric circulation then causes anomalous surface ocean circulation. These circulation changes consequently leads to the SST anomalies in the North Pacific which may persist until the following summer, named seasonal "foot printing" mechanism(SFPM).     

Seasonal changes in sea ice conditions along the Northeast Passage in 2007 and 2012

Remote sensing data from passive microwave and satellite-based altimeters, associated with the data measured underway, were used to characterize seasonal and spatial changes in sea ice conditions along...