基于改进FCLS算法的南极海冰密集度估算及算法比较

海冰具有良好的热力隔绝效应,它通过影响海洋和大气的热交换进而影响全球的气候变化。海冰密集度是极区海冰研究的重要指标之一。为实现高空间分辨率多类型海冰密集度的估算,本文将亮温极化梯度率和光谱梯度率引入基于全约束最小二乘法(fully constrained least squares,FCLS)的海冰密集度估算方法,并利用南极海冰过程与气候计划(Antarctic Sea Ice Processes and Climate,ASPe Ct)对改进方法的精度进行验证,然后与NASA Team2(NT2)算法和ARTIST Sea Ice(ASI)算法获得的海冰密集度结果进行了对比分析。结果显示,3种算法中本研究的方法精度最高,全年均方差13.8%,偏差为-0.7%;改进的方法对多年冰的估算精度优于一年冰。     

我国极地航运能力建设和高冰级船队发展对策分析

我国在南极和北极的活动日益增多,参与南北极事务和争取极地资源的利用已经成为国家未来向外扩展的重要举措之一。随着气候变暖,极地冰融速度加快,尤其是北极航运窗口期越来越长,两极资源利用和科考活动的需求量越来越大。而目前我国用于航行两极,尤其是北极的高冰级商业化船队十分缺乏,航运的陆基支持保障能力缺少,这将严重影响我国极地事业和商业航运运营的发展。本文通过对不同冰级船舶的保有量、建造技术能力、船舶运营和极地港口设施等各环节的分析,得出我国缺乏带较高等级冰级符号且可抗浮冰厚度1m及以上的极地航行船舶、相应极地航运能力不足的结论,并提出了我国建设极地航运能力的对策建议,为我国建设一支能在极地航行且带较高等级冰级符号船舶的船队、破冰船队以及建设极地陆基航运支持保障能力等提供决策参考。     

High-resolution mass spectrometric characterization of dissolved organic matter from warm and cold periods in the NEEM ice core

Dissolved organic matter(DOM) is an important component of ice cores but is currently poorly characterized. DOM from one Holocene sample(HS, aged at 1600–4500 B.P.) and one Last Glacial Maximum sample(LS, aged at 21000–25000 B.P.) from the North Greenland Eemian Ice Drilling(NEEM) ice core were analyzed by ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR-MS). CHO compounds contributed 50% of the compounds identified in negative-ionization mode in these two samples, with significant contributions from organic N, S, and P compounds, likely suggesting that marine DOM was an important source in these samples. Overall, the chemical compositions are similar between these two samples, suggesting their consistent DOM sources. However, subtle differences in the DOM between these two samples are apparent and could indicate differences in source strength or chemistry occurring through both pre-and post-depositional processes. For example, higher relative amounts of condensed carbon compounds in the HS DOM(5%), compared to the LS DOM(2%), suggest potentially important contributions from terrestrial sources. Greater incorporation of P in the observed DOM in the LS DOM(22%), compared to the HS DOM(13%), indicate more active microbiological processes that likely contribute to phosphorus incorporation into the DOM pool. Although these two samples present only a preliminary analysis of DOM in glacial/interglacial periods, the data indicate a need to expand the analysis into a broader range of ice-core samples, geographical locations, and glacial/interglacial periods.     

Record Low Sea-Ice Concentration in the Central Arctic during Summer 2010

The Arctic sea-ice extent has shown a declining trend over the past 30 years. Ice coverage reached historic minima in 2007 and again in 2012. This trend has recently been assessed to be unique over at least the last 1450 years. In the summer of 2010, a very low sea-ice concentration(SIC) appeared at high Arctic latitudes—even lower than that of surrounding pack ice at lower latitudes. This striking low ice concentration—referred to here as a record low ice concentration in the central Arctic(CARLIC)—is unique in our analysis period of 2003–15, and has not been previously reported in the literature. The CARLIC was not the result of ice melt, because sea ice was still quite thick based on in-situ ice thickness measurements.Instead, divergent ice drift appears to have been responsible for the CARLIC. A high correlation between SIC and wind stress curl suggests that the sea ice drift during the summer of 2010 responded strongly to the regional wind forcing. The drift trajectories of ice buoys exhibited a transpolar drift in the Atlantic sector and an eastward drift in the Pacific sector,which appeared to benefit the CARLIC in 2010. Under these conditions, more solar energy can penetrate into the open water,increasing melt through increased heat flux to the ocean. We speculate that this divergence of sea ice could occur more often in the coming decades, and impact on hemispheric SIC and feed back to the climate.     

CLOUD RADIATIVE AND MICROPHYSICAL EFFECTS ON THE RELATION BETWEEN SPATIAL MEAN RAIN RATE, RAIN INTENSITY AND FRACTIONAL RAINFALL COVERAGE

Cloud radiative and microphysical effects on the relation between spatial mean rain rate, rain intensity and fractional rainfall coverage are investigated in this study by conducting and analyzing a series of two-dimensional cloud resolving model sensitivity experiments of pre-summer torrential rainfall in June 2008. The analysis of time-mean data shows that the exclusion of radiative effects of liquid clouds reduces domain mean rain rate by decreasing convective rain rate mainly through the reduced convective-rainfall area associated with the strengthened hydrometeor gain in the presence of radiative effects of ice clouds, whereas it increases domain mean rain rate by enhancing convective rain rate mainly via the intensified convective rain intensity associated with the enhanced net condensation in the absence of radiative effects of ice clouds. The removal of radiative effects of ice clouds decreases domain mean rain rate by reducing stratiform rain rate through the suppressed stratiform rain intensity related to the suppressed net condensation in the presence of radiative effects of liquid clouds, whereas it increases domain mean rain rate by strengthening convective rain rate mainly via the enhanced convective rain intensity in response to the enhanced net condensation in the absence of radiative effects of liquid clouds. The elimination of microphysical effects of ice clouds suppresses domain mean rain rate by reducing stratiform rain rate through the reduced stratiform-rainfall area associated with severely reduced hydrometeor loss.     

δ~(18)O, δD and d-excess signatures of ground ice in permafrost in the Beiluhe Basin on the Qinghai-Tibet Plateau,China

In this paper, stable isotope(δ~(18)O, δD) investigations were completed in ground ice from a deep borehole in the Beiluhe Basin on northern Qinghai-Tibet Plateau to unravel the isotopic variations of ground ice and their possible source water. The δ~(18)O and δD of ground ice show distinctive characteristics compared with precipitation and surface water. The near-surface ground ice is highly enriched in heavier isotopes(δ~(18)O and δD), which were gradually depleted from top to bottom along the profile. It is suggestive of different origin and ice formation process. According to isotopic variations, the ice profile was divided into three sections: the near-surface ground ice at 2.5 m is frozen by the active-layer water which suffered evaporation. It is possible that ground ice between 3 and 4.2 m is recharged by the infiltration of snowmelt. From 5 to 6 m, the ground ice show complex origin and formation processes. Isotopic variations from 6 to 11.1 m and 20.55 m indicate different replenishment water. The calculated slope of freezing line(S=6.4) is larger than the experimental value(5.76), and is suggestive of complex origin and formation process of ground ice.     

“雪龙”号科考船在冰区航行的船体振动测量研究

船舶在冰区航行时,船体会受到多种类型激振力的作用而产生不同程度的结构振动。船体振动会对船体结构安全以及船上人员的正常工作产生不利影响。船体结构振动的现场测量可较为准确地分析船体振动的基本特性,确定船体振动与外界荷载因素的对应关系。在2015—2016年中国第32次南极科学考察过程中,对"雪龙"号极地科学考察船的冰激振动开展了现场测量。本研究对比了船体在无冰区和冰区航行过程中的船体振动变化,分析了船体在不同航速、冰厚以及不同破冰航行方式下的振动规律。测量结果表明:船体冰激振动随着航速和冰厚的增加而显著增大;在船体采用冲撞式破冰时横向振动最为明显,而在连续式破冰时,垂向振动最为明显。以上研究可为冰区航行中船体振动的现场监测技术提供有益参考,并有助于分析海冰对船体振动规律的影响。     

平面冰层覆盖下水中声传播损失特性分析

理论计算了冰层的声波反射系数,分析了平面冰层覆盖下水中声传播损失特性。将冰层视作平面覆盖层,建立了"空气-冰层-水"结构的冰层反射物理模型,结合冰中的物理声学参数,得到冰层反射系数;利用Bellhop海洋声学传播模型得到冰层覆盖下声场的传播损失,对比分析了传播损失与声波频率、声源深度的关系;结合冰层反射系数计算结果,解释了冰下信道具有频率选择性的原因。结果表明,冰层覆盖下声场传播具有明显的频率选择性,这种频率选择性是由声波频率和冰层厚度共同决定的。     

冰力学参数的超声波测试研究

利用非线性高能超声测试设备及超声波(纵波、横波)波速与物体力学参数的关系,对人造冰样进行了冰样力学参数(杨氏模量、泊松比、剪切模量、体积模量)随温度变化的研究。通过MATLAB进行所测数据曲线拟合,得到超声波波速在人造冰样中随温度的变化规律,进而由理论公式推导所测人造冰样力学参数随温度的变化规律。结果表明:冰样中超声波波速随温度降低而升高,冰样的杨氏模量、泊松比、剪切模量、体积模量也都随温度降低而升高。本研究有助于超声波检测法在冰样物理力学性质测量中的应用,为开展南极冰盖、海冰以及终年冻土等力学及流动特性研究提供理论模型和实验数据。     

不同月海冰边界提取算法对南极海冰变化的影响分析

海冰与海水的交界地带是海-冰-气相互作用的重要区域,其变化会影响海洋生物栖息地的联通状态和海洋、大气的交换,确定海冰边界对于分析海冰动态变化具有重要意义[1-2]。被动微波传感器为长期监测海冰变化提供了大尺度的连续观测数据。从经典统计、随机集理论出发,应用三种由被动微波日均海冰密集度数据提取月均海冰边界的方法,分析三种月均边界的差异,以及不同月均边界提取方法对海冰长期变化分析的影响。