电磁感应技术在波罗的海海冰厚度探测中的应用研究

海冰作为冰雪圈的重要组成部分,对气候变化十分敏感,海冰物理过程研究需要得到精确的海冰厚度。本文介绍一种能够高效探测海冰厚度的电磁感应方法及其在波罗的海(Baltic Sea)的成功应用。该技术方法针对海冰和海水的电特性,利用电磁感应原理精确探测仪器至冰水交界面的距离,以实现海冰厚度的测定。通过电磁感应(EM)仪直接观测的视电导率与同点位钻孔测量数据对比分析,获得视电导率与海冰厚度的转换关系式,并对通过该关系式计算出的海冰厚度进行验证,表明电磁感应技术能够获得可靠的海冰厚度数据,平均相对误差仅为12%。对波西尼亚海湾(Bothnian Bay)海冰厚度探测剖面的统计结果表明,2007年春季该区域平整冰厚度范围在0.4-0.6m之间。     

中国第四次北极科学考察EM31-ICE走航海冰厚度数据分析

利用ＥＭ３１-ＩＣＥ电磁感应仪与激光测距仪、声纳等设备在中国第四次北极科学考察过程对海冰厚度进行走航观测,通过对数据预处理获得了海冰厚度数据,结合长期冰站上采集的多组冰厚样本,获得ＥＭ３１-ＩＣＥ的各项校正参数。同时通过对异常数据的分析以及小波去噪、统计处理等方法,得出最终的解释结果：在去程时海冰厚度主要分布在０．５-２．５ｍ之间,而返程时的海冰厚度有明显变薄的倾向,主要分布在０．５-２．０ｍ之间。在高纬度地区海冰厚度明显大于低纬度地区,并且在高纬度地区海冰厚度统计图中常出现两个波峰,而低纬度地区常是一个波峰。在整个去程与返程过程中,超过４ｍ厚的海冰不到１％。     

A coupled multi-category sea ice model and POM for Baffin Bay and the Labrador Sea

An overview of the seasonal variation of sea-ice cover in Baffin Bay and the Labrador Sea is given.A coupled ice-ocean model,CECOM,has been developed to study the seasonal variation and associated ice-ocean processes.The sea-ice component of the model is a multi-category ice model in which mean concentration and thickness are expressed in terms of a thickness distribution function.Ten categories of ice thickness are specified in the model.Sea ice is coupled dynamically and thermo-dynamically to the Princeton Ocean Model.Selected results from the model including the seasonal variation of sea ice in Baffin Bay,the North Water polynya and ice growth and melt over the Labrador Shelf are presented.     

Summer fast ice evolution off Zhongshan Station,Antarctica

Based on the field data acquired in the program of fast ice observation off Zhongshan Station,Prydz Bay,East Antarctica during the austral summer 2005/ 2006,physical properties evolution of fast ice during the ice ablation season is ana- lyzed in detail.Results show that the annual maximum ice thickness in 2005 occurred in later November,and then ice started to melt,and the ablation duration was 62 days;sea water under the ice became warmer synchronously;corresponding to the warming sea ice temperature,a"relative cold mid-layer"appeared in sea ice;the fast ice marginal line recoiled back to the shore observably,and the recoil distance was 20.9 km from 18 December 2005 through 14 January 2006.In addition,based on the data of sea ice thickness survey along the investigation course of MV Xuelong on December 18 of 2005,the ice thickness distribution paten in the marginal ice zone have been described:sea ice thickness increased,but the diversity of floe ice thick- ness decreased from open water to fast ice zone distinctly.     

泉州湾表层沉积物粒度指示的沉积动力端元解析

基于前期工作,采取粒度端元分析方法,结合沉积物粒度参数、研究区水深以及水动力等对福建省泉州湾海域采集的65个表层沉积物样品进行了沉积动力学解析判别,量化研究区表层沉积物复杂的沉积动力特征。结果表明：样品粒度数据中可以至少分离出4个不同的端元组分,其粒径范围大致分布在0.2~200、20~30、50~500、80~1 000 μm,可能分别代表了水动力较弱的滞流沉积作用环境、台风作用下的改造作用、潮汐作用下的较强的水动力以及人类活动作用下的扰动作用。由于沉积动力的持续进行及分选沉积作用,可能掩盖了粒度的物源效应,所以只呈现出不同的沉积动力学特点。     

Trends and variability of sea ice in Baffin Bay and Davis Strait, 1953–2001

The extent and duration of sea ice in Baffin Bay and Davis Strait has a major impact on the timing and strength of the marine production along West Greenland. The advance and retreat of the sea ice follows a predictable pattern, with maximum extent typically in March. We examine the area of sea ice in March in three overlapping study regions centred on Disko Bay on the west coast of Greenland. Sea ice concentration estimates derived from satellite passive microwave data are available for the years 1979-2001. We extend the record back in time by digitizing ice charts from the Danish Meteorological Institute, 1953-1981. There is reasonable agreement between the chart data and the satellite data during the three years of overlap: 1979-1981. We find a significant increasing trend in sea ice for the 49-year period (1953-2001) for the study regions that extend into Davis Strait and Baffin Bay. The cyclical nature of the wintertime ice area is also evident, with a period of about 8 to 9 years. Correlation of the winter sea ice concentration with the winter North Atlantic Oscillation (NAO) index shows moderately high values in Baffin Bay. The correlation of ice concentration with the previous winter's NAO is high in Davis Strait and suggests that next winter's ice conditions can be predicted to some extent by this winter's NAO index.     

2003年夏季东南印度洋上层海洋的水文特征

本文利用 2 0 0 3年 2月我国第 1 9次南极考察队在南极普里兹湾到澳大利亚弗里曼特尔南印度洋断面上获得的XBT和XCTD数据 ,分析了该断面上层的水团分布和锋面的特征 ,并讨论了极锋以南表层的淡水输入和热量输入与海冰、降水及平流之间的关系。南极夏季表层水(AASSW)、亚南极表层水 (SASW)、亚热带表层水 (STSW)分布于温盐跃层之上的混合层中 ,由南向北依次分布。AASSW之下是向北延伸的温度最小值层 ,即冬季水 (WW) ,其下则是涌升的上层南极饶及深层水 (UCDW)。南侵的高温高盐的亚热带表层水 (STSW)之下是温度和盐度相对均匀的亚南极模式水 (SAMW)。本航次发现 ,在 63.5°S ,79.7°E的 60 0m以深有低盐水体 (相对其周围水体 )存在 ,核心盐度 34.5 8,位于 80 0- 90 0m水深之间。这是历次考察在该断面所不曾观测到的现象。断面上的锋面从南向北依次为南极陆坡锋 (ASF)、极锋 (PF)、亚南极锋 (SAF)和亚热带锋 (STF)。ASF位于 65°S以南的 1 0 0m以深 ,等温线和等盐线向南倾斜 ;PF位于 5 4°S ,90 .4°E ;SAF位于 45 .3°- 47.5°S ,1 0 2 .5°- 1 0 4 .4°E之间 ,深达整个测量深度 ,温度具有两个高梯度核心 ;首次在该断面观测到双STF结构 ,位于 41 .9°- 42 .6°S,1 0 6.7°- 1 0 7.3°E和 37.7°- 38     

南北极海冰变化及其影响因素的对比分析

海冰是海洋-大气交互系统的重要组成部分,与全球气候系统间存在灵敏的响应和反馈机制。本文选用欧洲空间局发布的1992—2008年海冰密集度数据分析了南北极海冰在时间和空间上的变化规律与趋势,并结合由美国环境预报中心(National Centers for Environmental Prediction,NCEP)和美国大气研究中心(National Center for Atmospheric Research, NCAR)联合制作的NCEP/NCAR气温数据和ENSO指数探讨了南北极海冰变化的影响因素。结果表明,北极海冰面积呈明显的减少趋势,其中夏季海冰最小月的减少更快。北冰洋中央海盆区、巴伦支海、喀拉海、巴芬湾和拉布拉多海的减少最明显。南极海冰面积呈微弱增加趋势,罗斯海、太平洋扇区和大西洋扇区的海冰增加。北极海冰面积与气温有显著的滞后1个月的负相关关系(P0.01)。北极升温显著,北冰洋中央海盆区、喀拉海、巴伦支海、巴芬湾和楚科奇海升温趋势最大,海冰减少很明显。南极在南大西洋、南太平洋呈降温趋势,海冰增加。北极海冰减少与39个月之后ONI的下降、40个月之后SOI的上升密切相关;南极海冰增加与7个月之后ONI的下降、6个月之后SOI的上升存在很好的响应关系。南北极海冰变化与三次ENSO的强暖与强冷事件有很好的对应关系。     

2014年夏季北极东北航道冰情分析

使用2003—2014年6—9月份的AMSR-E和AMSR-2海冰密集度数据计算了北极海冰范围, 并获得海冰空间分布图。通过分析得出, 2014年北极夏季海冰范围在数值上与2003—2013年的多年平均值很接近, 在空间分布上与多年中值范围相比主要表现为两个方面的不同：(1)2014年夏季拉普捷夫海及其以北海域海冰明显少于多年中值范围, 9月份冰区最北边界超过了85°N;(2)巴伦支海北部斯瓦尔巴群岛至法兰士约瑟夫地群岛区域海冰范围明显多于多年中值范围, 而且海冰范围在8月份不减反增, 冰区边界较7月份往南扩张了约0.8个纬度。2014年夏季在拉普捷夫海以南风为主, 而在巴伦支海以北风为主。南风将俄罗斯大陆上温暖的空气吹向高纬地区, 造成高纬地区温度偏高, 促进拉普捷夫海海冰融化, 并使海冰往北退缩。北风将北冰洋上的冷空气吹向低纬地区, 造成巴伦支海的气温偏低, 不利于海冰的融化, 同时北风使海冰往南漂移扩散, 造成巴伦支海北部海冰范围在2014年偏多。2014年北地群岛航线开通时间范围大约在8月上旬到10月上旬, 时长约两个月。新西伯利亚群岛及附近海域的开通时间稍早于北地群岛, 但关闭时间比北地群岛晚, 所以 2014年东北航道全线开通的时间主要受制于北地群岛附近海冰变化。     

2011夏季南极普里兹湾营养盐与浮游植物生物量的分布

利用2011南极夏季在普里兹湾获取的海水样,检测了Chla、磷酸盐、硅酸盐、硝酸盐和铵盐的含量。结果表明,普里兹湾表层海水中Chla的含量普遍具有冰架边缘>陆架区>陆坡及深海区的分布特征,海冰的消融及水体的稳定性是影响表层海水Chla分布的主要原因。Chla含量的垂直分布与光照条件相关,具有上层水体含量高,随着深度逐渐降低的分布特征。磷酸盐、硅酸盐和硝酸盐的水平及垂直分布特征都与Chla的分布格局相反。表层海水中铵盐的分布特征与磷酸盐等主要营养盐的分布格局相反,冰架边缘、陆架区铵盐的垂直分布特征与陆坡及深海区不同,在冰架边缘和陆架区有机质降解过程主导着水柱中铵盐的浓度,而浮游植物吸收作用与有机质降解过程之间的平衡控制着陆坡及深海区铵盐的垂直分布。根据Chla与营养盐的浓度及分布特征,结合温度、盐度、溶解氧等水文要素,分析探讨了Chla深层最大值现象（DCM）的成因及67.5°S以南表层海水中铵盐对硝酸盐吸收的抑制作用。     

罗斯海和普里兹湾海域海冰范围变化对比分析

海冰范围的变化对气候变化、生态系统以及人类活动都会产生重大的影响,近年来极地海冰范围的变化受到广泛关注。对南极罗斯海与普里兹湾海域海冰范围进行时间序列分析,研究发现海冰范围季节性变化在罗斯海与普里兹湾海域差异较大,罗斯海地区表现出"快速缩小、迅速扩大"的特性,普里兹湾海域表现出"快速缩小、缓慢扩大"的特性。两地区的海冰范围在年际变化上都表现出扩大的趋势,2003—2014年罗斯海地区海冰变化趋势为(1.39±1.12)×104km2·a~(-1),普里兹湾海域海冰变化趋势为(0.61±0.26)×104km2·a~(-1)。罗斯海地区夏季的年际变化为减少趋势。     

Crustal thicknesses in Fennoscandia

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As a supplement to seismic profiling surveys, crustal thicknesses have been estimated for 11 Fennoscandian seismograph stations equipped with three-component long period instruments, using the so-called spectral ratio technique of Phinney. The largest Moho depths, of the order of 45 km, were found for stations located in the north-east areas of Norway and Sweden and in Finland, with a local maximum in the Bothnian Bay. The coastal area of south-east Norway and Zealand, Denmark exhibit crustal thicknesses in the range 28–33 km. The agreement between our results and those obtained by conventional refraction profiling is good, when this comparison is restricted to profiles of lengths 300 km or more, and when the associated crustal thickness estimate is averaged over the central parts of the profiles in question. Also, a comparison between our results and other available geophysical information gives that the oldest tectonic provinces of the Baltic Shield also are characterized by relatively modest heat flow, and exhibit the greatest crustal thicknesses. Post-glacial uplift data and large wavelength free air gravity data appear to be uncorrelated with crustal thickness. The same partly applies to Bouguer gravity anomalies, thus implying that the isostatic compensation mechanism in Fennoscandia is of both Airy and Pratt type.     

北冰洋海冰/气候系统及其对全球气候的影响

结合前人对北冰洋海冰、气候系统的研究成果和 1 999年 8月在北冰洋对海冰的现场观测 ,本文综述了海冰分布、厚度的变化 ,海冰表面特征、积雪变化及北冰洋天气、气候特征和分区。讨论了北极海冰与南极海冰的差异。文章认为 ,北冰洋与周围地区气候变化趋势的不一致 ,主要是由于夏季在北冰洋海冰与开阔水域的相间分布、海冰漂移、融化吸热 ,均衡了周围大气、海洋温度的变化。     

南极乔治王岛长城湾沿岸固定冰中有色层生态观察

自1988年11月至1989年3月,对南极乔治王岛的长城湾沿岸水域中的海洋生物和环境因子进行了调查,1988年11月20日在2号站采得的冰芯中部有一层约5cm的棕色层,而1988年11月17日、20日和26日在5号站采得的冰芯样中有二层棕色层。固定冰中叶绿素a浓度范围在2.55～56.8mg/m~3之间,而且大部分含量集中在海冰的中间层中,而不象其它海区如昭和、戴维斯、凯西和麦克默多等站,大部分叶绿素a集中在海冰的底部,造成这种差别的原因、可能是由于海冰的结构和形成过程不同所致。     

东南极普里兹湾1990年1—2月大风过程与气旋和锋面活动分析

本文用澳大利亚墨尔本气象中心,苏联南极青年站地面天气图和NOAA-10,NOAA-11极轨卫星云图确定了东南极普里兹湾及其附近海域1990年1—2月份气旋中心位置;讨论了这些气旋的活动特征。分析了实测大风对应的天气系统,天气形势和卫星云图特征,指出普里兹湾沿海存在气旋、锋面以及锋面云和气旋先后相继的影响。锋面及锋面、气旋先后相继影响与500hPa上的强高压脊天气形势、强风与锋面带中纹理非常不均匀区域有密切关系。     

Recovering magnetic susceptibility from electromagnetic data over a one-dimensional earth

While the inversion of electromagnetic data to recover electrical conductivity has received much attention, the inversion of those data to recover magnetic susceptibility has not been fully studied. In this paper we invert frequency-domain electromagnetic (EM) data from a horizontal coplanar system to recover a 1-D distribution of magnetic susceptibility under the assumption that the electrical conductivity is known. The inversion is carried out by dividing the earth into layers of constant susceptibility and minimizing an objective function of the susceptibility subject to fitting the data. An adjoint Green's function solution is used in the calculation of sensitivities, and it is apparent that the sensitivity problem is driven by three sources. One of the sources is the scaled electric field in the layer of interest, and the other two, related to effective magnetic charges, are located at the upper and lower boundaries of the layer. These charges give rise to a frequency-independent term in the sensitivities. Because different frequencies penetrate to different depths in the earth, the EM data contain inherent information about the depth distribution of susceptibility. This contrasts with static field measurements, which can be reproduced by a surface layer of magnetization. We illustrate the effectiveness of the inversion algorithm on synthetic and field data and show also the importance of knowing the background conductivity. In practical circumstances, where there is no a priori information about conductivity distribution, a simultaneous inversion of EM data to recover both electrical conductivity and susceptibility will be required.     

南极中山站附近海域固定冰的夏季变化

利用中国第21、22次南极科学考察(2004/2005、2005/2006)对中山站附近海域固定冰物理特性系统观测的结果,特别是依据其中2005年11月下旬至2006年1月下旬的现场实测数据详细分析了中山站附近海域固定冰消融过程物理性质的变化特征。结果表明:此区域固定冰从11月下旬开始消融,融冰期为62 d;同时,融冰期冰下水体温度迅速升高;在不断增强的太阳短波辐射和海洋热通量作用下,海冰温度也逐渐上升,并出现"相对冷中间层";热力和动力外强迫作用下,2005年12月18日-2006年1月14日期间此区域固定冰边缘线后退了20.9 km;另外,2005年12月18日固定冰边缘区走航冰厚监测结果还表明,边缘区海冰厚度在向岸方向有明显的增加趋势,并且随着接近海岸海冰厚度的离散程度逐渐减小。     

侧边界融化对北极海冰影响的数值模拟

对NCAR CSIM5 海冰模式中海冰侧边界融化参数化方案进行了详细阐述,并利用CSIM5模式模拟了侧边界融化对北极海冰厚度和海冰面积变化的影响,试验结果表明：（1）侧边界融化热力过程会增大海冰厚度和海冰面积的消融,海冰厚度消融最明显的区域分布在西伯利亚海和格陵兰海,海冰面积消融最明显区域分布海冰边缘地区;（2）侧边界融化过程对夏季海冰厚度影响比冬季更为明显,而对冬季海冰面积的影响要比夏季更为明显;（3）侧边界融化方案能更好地模拟出海冰面积的季节性变化;（4）海水表面温度（SST）是影响海冰侧边界融化过程的重要因子,侧边界融化率的大值区分布在SST零度线附近的狭窄区域。     

High resolution simulations of Arctic sea ice, 1979–1993

To evaluate improvements in modelling Arctic sea ice, we compare results from two regional models at 1/12° horizontal resolution. The first is a coupled ice-ocean model of the Arctic Ocean, consisting of an ocean model (adapted from the Parallel Ocean Program, Los Alamos National Laboratory [LANL]) and the "old" sea ice model. The second model uses the same grid but consists of an improved "new" sea ice model (LANL/CICE) with a simple ocean mixed layer. Both models are forced with European Centre for Medium-range Weather Forecasts reanalysis data for 1979–1993. A comparison of the two sea ice models focuses on the winter of 1987 to emphasize the internal ice stress and to minimize biases towards a particular Arctic climate regime. The "new" sea ice model gives improved ice deformation and drift fields. These improvements are associated at least in part with the multi-category representation of the ice thickness distribution and more realistic parameterization of the ice strength. Long, narrow features in ice divergence and shear fields resemble those observed in SAR imagery, except that their average width is overestimated, possibly due to insufficient horizontal resolution. We also compare the mean sea ice drift and its decadal variability in two "old" sea ice models at different horizontal resolutions: 18-km and 9-km. We find no significant change in ice drift between the two models, except in areas of significant ice-ocean interactions due to more realistic ocean currents and water mass properties in the 9-km model.     

极地海冰厚度探测方法及其应用研究综述

海冰是全球气候变化的敏感指示器,对全球热平衡、大气环流、海洋水循环和温盐平衡起到至关重要的作用。海冰厚度作为海冰中最重要的参数之一,也是最难探测的地球物理参数。在回顾和分析基于仰视声纳、走航观测、电磁感应、微波遥感等方法进行极地海冰厚度探测和应用研究的基础上,着重阐述近年来利用卫星测高技术估算极地海冰厚度的研究现状与趋势,为我国开展相关科研工作提供参考。