2016年南极中山站固定冰冰厚观测分析

极区海冰是全球气候系统的重要组成部分,南极的固定冰普遍存在于其沿海地区,中山站周边固定冰一般在11月中下旬达到最厚。海冰厚度是海冰的重要参数之一,2016年在南极中山站附近3个站点(S1、S2、S3站点)共布放了4套温度链浮标,包括1套SIMBA (Snow and Ice Mass Balance Array)温度链浮标和3套太原理工大学温度链浮标(TY温度链浮标),SIMBA温度链浮标每天观测4次,TY温度链浮标每小时观测1次。利用浮标观测的温度剖面以及海冰和海水间不同介质温度差异计算得到海冰厚度。在S3站点,同时布放了SIMBA温度链浮标和TY温度链浮标。温度链浮标计算冰厚和人工钻孔观测冰厚比较结果显示,S1站点TY温度链浮标计算的海冰厚度平均误差和均方根误差分别为3.3 cm和14.7 cm,S2站点和S3站点分别为6.6 cm、6.9 cm以及4.0 cm、4.8 cm。S3站点的SIMBA温度链浮标计算冰厚和人工观测冰厚的平均误差和均方根误差为8.2 cm和9.7 cm。因而S3站点TY温度链浮标计算的海冰厚度更接近人工观测的结果。进一步对Stefan定律海冰生长模型进行对比,模型计算得到的海冰生长率为0.1～0.8 cm/d,生长率快于TY温度链浮标的结果,且受积雪影响明显。相比于卫星遥感反演冰厚的误差和观测时段的限制以及有限的人工观测,2种温度链浮标未来对于中山站附近海冰的长期监测均有重要的应用价值。     

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

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.     

WAVEWATCH Ⅲ不同海冰源项的海浪模拟效果对比

为了验证第三代海浪模式WAVEWATCH Ⅲ V5.16中不同海冰损耗源项在秋季波弗特海对海冰存在下海浪的模拟能力,建立自波弗特海至马更些河河口的两级嵌套海浪模型,对2014年8月1日至9月31日该海域北极风暴作用下的暴风浪有效波高进行模拟研究,并利用浮标实测数据对模拟结果进行对比分析。结果表明,在应用于大范围海域、缺乏海冰有效剪切模量、黏性系数等属性参数的前提下,离海冰较近、海浪能量受海冰控制作用较为明显的区域,各海冰源项中IC1源项表现最好,能够表现出更加符合波弗特海海域特定的冰情、冰况的能量耗散特征。     

Properties of sea ice and overlying snow in the Southern Sea of Okhotsk

The general properties of sea ice and overlying snow in the southern Sea of Okhotsk were examined during early February of 2003 to 2005 with the P/V “Soya”. Thin section analysis of crystal structure revealed that frazil ice (48% of total core length) was more prevalent than columnar ice (39%) and that stratigraphic layering was prominent with a mean layer thickness of 12 cm, indicating that dynamic processes are essential to ice growth. The mean thickness of ice blocks and visual observations suggest that ridging dominates the deformation process above thicknesses of 30 to 40 cm. As for snow, it was found that faceted crystals and depth hoar are dominant (78%), as which is also common in the Antarctic sea ice, and is indicative of the strong vertical temperature gradients within the snow. Stable isotope measurements (δ¹⁸O) indicate that snow ice occupies 9% of total core length and that the mass fraction of meteoric ice accounts for 1 to 2% of total ice volume, which is lower than the Antarctic sea ice. Associated with this, the effective fractionation coefficient during the freezing of seawater was also derived. Snow ice was characterized by lower density, higher salinity, and nearly twice the gas content of ice of seawater origin. In addition, it is shown that the surface brine volume fraction and freeboard are well correlated with ice thickness, indicating some promise for remote sensing approaches to the estimation of ice thickness.     

基于高光谱遥感的渤海海冰厚度半经验模型

Sea ice thickness is one of the most important input parameters for the prevention and mitigation of sea ice disasters and the prediction of local sea environments and climates. Estimating the sea ice thickness is currently the most important issue in the study of sea ice remote sensing. With the Bohai Sea as the study area, a semiempirical model of the sea ice thickness(SEMSIT) that can be used to estimate the thickness of first-year ice based on existing water depth estimation models and hyperspectral remote sensing data according to an optical radiative transfer process in sea ice is proposed. In the model, the absorption and scattering properties of sea ice in different bands(spectral dimension information) are utilized. An integrated attenuation coefficient at the pixel level is estimated using the height of the reflectance peak at 1 088 nm. In addition, the surface reflectance of sea ice at the pixel level is estimated using the 1 550–1 750 nm band reflectance. The model is used to estimate the sea ice thickness with Hyperion images. The first validation results suggest that the proposed model and parameterization scheme can effectively reduce the estimation error associated with the sea ice thickness that is caused by temporal and spatial heterogeneities in the integrated attenuation coefficient and sea ice surface. A practical semi-empirical model and parameterization scheme that may be feasible for the sea ice thickness estimation using hyperspectral remote sensing data are potentially provided.     

BCC_CSM对北极海冰的模拟:CMIP5和CMIP6历史试验比较

本文利用北京气候中心气候系统模式(BCC_CSM)在最近两个耦合模式比较计划(CMIP5和CMIP6)的历史试验模拟结果,对北极海冰范围和冰厚的模拟性能进行了比较,结果表明:(1) CMIP6改善了CMIP5模拟海冰范围季节变化过大的问题,总体上更接近观测结果;(2)两个CMIP试验阶段中BCC_CSM模拟的海冰厚度都偏小,但CMIP6试验对夏季海冰厚度过薄问题有所改进。通过对影响海冰生消过程的冰面和冰底热收支的分析,我们探讨了上述模拟偏差以及CMIP6模拟结果改善的成因。分析表明,8?9月海洋热通量、向下短波辐射和反照率对模拟结果的误差影响较大,CMIP6试验在这些方面有较大改善;而12月至翌年2月,CMIP5模拟的北极海冰范围偏大主要是海洋热通量偏低所导致,CMIP6模拟的海洋热通量较CMIP5大,但北大西洋表层海流的改善才是巴芬湾附近海冰外缘线位置改善的主要原因。CMIP试验模拟的夏季海冰厚度偏薄主要是因为6?8月海洋热通量和冰面热收支都偏大,而CMIP6试验模拟的夏季海冰厚度有所改善主要是由于海洋热通量和净短波辐射的改善。海冰模拟结果的改善与CMIP6海冰模块和大气模块参数化的改进有直接和间接的关系,通过改变短波辐射、冰面反照率和海洋热通量,使BCC_CSM模式对北极海冰的模拟性能也得到有效提高。     

Mechanism of sea ice formation based on comprehensive observation data in Liaodong Bay,China

Sea ice disaster is one of the principal natural hazards that affect some coastal areas of China,and the formation of ice cover in a wave field has important characteristics.However,analysis of the mechanism in which waves affect the thermodynamic process of sea ice is lacking,and the influence of waves is not taken into consideration in numerical models of sea ice,largely because of a lack of simultaneous observations of waves and sea ice.Using observational data of the sea ice cycle in the coastal waters of Liaodong Bay(China),we analyzed the characteristics of hydrology,meteorology,and sea ice thickness during the formation of sea ice,and explored the changes in the interrelationships among heat fluxes,waves,and sea ice under actual sea conditions.The results could provide a decision-making support as a reference to the establishment and improvement of China's early waming system to sea ice disasters,and the protection of ice drilling operations and production platform safety.     

基于Hough变换原理的海冰厚度识别方法

作为主要海冰参数之一的海冰厚度对海冰灾害评估和极地船舶与冰区海洋工程结构设计具有重要意义。采用船侧视频图像对海冰厚度进行自动识别是提取海冰参数的重要方式。本文采用基于Hough变换的机器视觉方法对海冰翻转过程中的表面轮廓线进行识别,从而自动获取海冰厚度参数。根据海冰图像特征制定了图像边缘识别-近似线段识别-海冰轮廓线段组识别的计算流程。在线段组识别过程中,根据海冰的几何特征建立了由夹角、长度及间距参数相关联的3个识别参数所组成的判断条件。为验证方法的可靠性,将该方法用于“雪龙”号第八次北极科考的走航实测数据中,结果表明,3个识别参数均具有最优阈值。当低于最优值时提高阈值可增加有效识别率;而高于最优值时提高阈值则会导致误判率增大,采用最优阈值可使冰厚识别率达到90%以上。因此,采用基于Hough变换的冰厚识别方法可实现对海冰厚度的实时监测。     

Thickness sensitivities in the CICE sea ice model

Passive microwave satellite observations of ice extent and concentration form the foundation of sea ice model evaluations, due to their wide spatial coverage and decades-long availability. Observations related to other model quantities are somewhat more limited but increasing as interest in high-latitude processes intensifies. Sea ice thickness, long judged a critical quantity in the physical system, is now being scrutinized more closely in sea ice model simulations as more expansive measurements become available. While albedo is often the first parameter chosen by modelers to adjust simulated ice thickness, this paper explores a set of less prominent parameters to which thickness is also quite sensitive. These include parameters associated with sea ice conductivity, mechanical redistribution, oceanic heat flux, and ice–ocean dynamic stress, in addition to shortwave radiation. Multiple combinations of parameter values can produce the same mean ice thickness using the Los Alamos Sea Ice Model, CICE. One of these “tuned” simulations is compared with a variety of observational data sets in both hemispheres. While deformed ice area compares well with the limited observations available for ridged ice, thickness measurements differ such that the model cannot agree with all of them simultaneously. Albedo and ice–ocean dynamic parameters that affect the turning of the ice relative to the ocean currents have the largest effect on ice thickness, of the parameters tested here. That is, sea ice thickness is highly sensitive to changes in external forcing by the atmosphere or ocean, and therefore serves as a sensitive diagnostic for high-latitude change.     

海冰对海浪影响研究综述

受全球气候变化的影响,极区海浪尤其是北极海浪在过去几十年发生了显著的变化,使得海冰边缘区海冰与海浪的相互作用愈发显著。本文从物理海洋学的角度出发,较系统地总结了海冰对海浪作用研究的国内外现状,从理论和实测的角度分别探讨了海冰对海浪能量的耗散及其引起的波动频散关系的变化,同时分析了当前海冰覆盖海域海浪的数值模拟与现场观测研究,指出了未来开展有冰海域海浪数值模拟与预报所面临的主要问题,并对该方向今后的研究做出展望。总体来看,尽管海冰对海浪作用的机理复杂且与海冰类型高度相关,但是海冰对海浪能量的衰减与传播距离基本呈指数关系,并且海冰会一定程度上影响海浪的传播速度。未来依然需要更多不同海冰类型下海浪的观测数据以开展进一步的机理分析、模型检验和参数校准,进而实现高精度的业务化预报。     

海冰动力过程的改进离散元模型及在渤海的应用

海冰的断裂、重叠和堆积等离散分布特性广泛地存在于极区和副极区的不同海域,并对海冰的生消、运移过程有着重要影响。针对海冰在不同尺度下的离散分布特点,发展海冰动力过程的离散元方法有助于完善海冰数值模式,提高海冰数值模拟的计算精度。为此,本文针对海冰生消运移过程中的非连续分布和形变特性,发展了适用于海冰动力过程的改进离散元模型(MDEM)。不同于传统离散元方法,该模型将海冰离散为具有一定厚度、尺寸和密集度的圆盘单元。海冰单元设为诸多浮冰块的集合体,其在运移和相互接触碰撞过程中,依照质量守恒发生单元尺寸、密集度和厚度的相应变化。基于海冰离散性和流变性的特点,该模型采用黏弹性接触本构模型计算单元间的作用力,并依据Mohr-Coulomb准则计算海冰法向作用下的塑性变形及切向摩擦力。为验证该模型的可靠性,本文对海冰在规则水域内的运移和堆积过程进行了分析,离散元计算结果与解析值相一致;此外,对旋转风场下海冰漂移规律的模拟进一步验证了本文方法的精确性。在此基础上,对渤海辽东湾的海冰动力过程进行了48h数值分析,计算结果与卫星遥感资料和油气作业区的海冰现场监测数据吻合良好。在下一步工作中将考虑海冰离散元模拟中的热力因素影响,发展具有冻结、断裂效应的海冰离散元模型,更精确地模拟海冰动力-热力耦合作用下的生消和运移过程。     

南港冰期海上漂浮式光伏技术试验研究

海上漂浮式光伏在北方冬季面临被海冰破坏的危险,冰期海洋环境对漂浮式光伏的影响尚处于研究初级阶段,因此非常有必要开展相关研究。为了有效防冰与抗冰,本文从水动力、波浪冲击性、支架稳定性、海水腐蚀、锚固方式等方面入手,首先对光伏方阵总环境载荷进行计算与仿真,然后对集装箱式漂浮防波堤、浮体方阵结构、支架、配件材料及锚固系统等进行优化设计,最后在潮汐变化显著的天津南港近海水域进行了冰期试验。试验数据与结果表明：浮式防波堤能有效阻挡围堰外海冰,消浪效果达到设计要求;塑料螺栓不仅可以有效避免因潮汐产生的浮体松动,而且能抵抗来自高盐高雾环境的腐蚀;设计的锚固系统能有效固定光伏方阵,使其漂移在可控范围内。该试验研究成果为优化北方冰期海上光伏技术方案提供了试验依据与理论支持。     

北极阿蒙森湾一年冰物理和光学性质的观测研究

利用加拿大环极冰间水道系统研究项目,作者对2007年11月24日至2008年1月26日北极群岛阿蒙森湾海域秋冬季节一年冰的物理和光学性质进行了观测研究。结果显示,观测期间的海冰厚度整体在27～108 cm范围内变化,积雪厚度仅为0～6 cm。海冰温度、盐度和密度在冰内的分布特征为:海冰表层最低温度为–22.4℃,底层最高温度为–2.2℃,冰内温度随深度单调增大;盐度变化范围为3.30～11.70,冰内盐度剖面呈现“C”形,即表层和底层盐度较大,而中间层盐度较小;海冰的平均密度略大,为（0.91±0.03）g/cm3。通过观测人造光源在海冰中的透射辐射谱分布,发现一年冰的光谱透射辐射在490 nm和589 nm处呈明显的双峰结构,但随着海冰厚度的增加,双峰结构逐渐减弱,体现了海冰对于不同谱段辐射能衰减作用的差异。在可见光范围内,裸冰和雪覆冰的吸收率最小值出现在490 nm,在443～490 nm范围内二者的吸收率随波长增大而降低,在490～683 nm范围内二者的吸收率随波长增大而升高,但雪覆冰的吸收率在可见光范围内基本保持不变,体现了雪覆冰吸收率的光谱独立性。一年冰的谱衰减系数随波长呈“U”字形分布,紫光和红光谱段的衰减系数较大,中间谱段的衰减系数较小,589 nm波长的衰减系数最小,为1.7 m–1。将谱衰减系数在可见光范围内积分,得到一年冰的积分漫射衰减系数约为2.3 m–1,略高于多年浮冰的漫射衰减系数1.5 m–1。阿蒙森湾一年冰与加拿大海盆北部多年浮冰辐射光学性质的差异,主要源于陆源物质输入引起的海冰内含物组分的改变,而不同组分对光谱的吸收和散射性质不同,进一步导致了光学性质的整体变化。     

Numerical modeling on hydrodynamic performance of a bottom-hinged flap wave energy converter

The hydrodynamic performance of a bottom-hinged flap wave energy converter(WEC) is investigated through a frequency domain numerical model.The numerical model is verified through a two-dimensional analytic solution,as well as the qualitative analysis on the dynamic response of avibrating system.The concept of "optimum density" of the bottom-hinged flap is proposed,and its analytic expression is derived as well.The frequency interval in which the optimum density exists is also obtained.The analytic expression of the optimum linear damping coefficient is obtained by a bottom-hinged WEC.Some basic dynamic properties involving natural period,excitation moment,pitch amplitude,and optimum damping coefficient are analyzed and discussed in detail.In addition,this paper highlights the analysis of effects on the conversion performance of the device exerted by some important parameters.The results indicate that "the optimum linear damping period of 5.0 s" is the most ideal option in the short wave sea states with the wave period below 6.0 s.Shallow water depth,large flap thickness and low flap density are advised in the practical design of the device in short wave sea states in order to maximize power capture.In the sea state with water depth of 5.0 m and wave period of 5.0 s,the results of parametric optimization suggest a flap with the width of 8.0 m,thickness of 1.6 m,and with the density as little as possible when the optimum power take-off(PTO) damping coefficient is adopted.     

渤海海域冰水共存期的波能流密度推算

为给寒区海域的波浪能估算提供科学依据,提出一种合理推算冰水共存海域波浪条件及波能流密度的方法,该方法将海冰模型与水动力学模型耦合模拟得到的冰浓度以线性修正函数的方式纳入波浪模型的海面摩阻风速方程中,并基于MCT (model coupling toolkit)耦合器将海冰模型、水动力学模型与波浪模型进行实时耦合。基于该方法模拟了渤海冬季寒潮大风期间的海冰以及波能流密度的演化。模拟结果表明,在2012年2月5~8日寒潮大风期间,结冰区域占到渤海总面积的1/3,约有76%的渤海海域的平均波能流密度受海冰影响减小,其中辽东湾近岸的波能流密度平均受冰影响最多减小了100%,而渤海湾和莱州湾近岸受冰影响最多分别减小了60%和50%。即使是无冰覆盖的老铁山水道,其波能流密度的最大值也受冰影响减少了14%。耦合模拟可以更为准确地对渤海冬季的波能流密度分布进行评估,为波浪能发电厂选址提供依据。     

Modeling the evolution of snow, snow ice and ice in the Baltic Sea

A numerical 1‐dimensional fine grid sea ice thermodynamic model is constructed accounting specially for: (1) slush formation via flooding and percolation of rain‐ and snow meltwater, (2) the consequent snow ice formation via slush freezing, and (3) the effects of snow compaction on heat diffusion in snow cover. The model simulations from ice winter period 1979–90 are viewed against corresponding observations at the Kemi fast ice station (65 °39.8' N, 24° 31.4' E). The 11‐year averaged model results show good overall consistency with corresponding total ice thickness observations. The model slightly overestimates the snow ice thickness and underestimates the snow thickness in February and March, which is mainly addressed to the model assumption of isostatic balance (i.e., slush formation via flooding), which was probably not fully satisfied at the coastal Kemi fast ice station. Supposing that this assumption is nevertheless generally valid away from the very coastal fast ice zone, an estimate for sea ice sensitivity to changes in winter precipitation rate is produced. Increased precipitation leads to an increase only in snow ice thickness with little change in total ice thickness, while a reduction in precipitation of more than {213}50% causes a significant increase in total ice thickness. The difference in modeled total ice thickness for the case of artificially neglecting snow ice physics is about 25%, which indicates the importance of including snow ice physics in a sea ice model dealing with the seasonal sea ice zone.     

基于岸基雷达数据的鲅鱼圈海域冰情基本特征

以2010~2015年的岸基雷达海冰监测数据为基础,简要分析了鲅鱼圈海域的冰期、冰型和冰厚等冰情基本特征。近年来的海冰监测数据表明,鲅鱼圈海域的冰期明显偏短,冰期内不同阶段的冰型变化较明显,鲅鱼圈海域部分时段海冰分布比例变化较大,这主要归因于该区域的海冰运动。针对目前岸基雷达海冰监测的技术发展现状,提出了岸基雷达海冰监测技术研发的主要问题是雷达像元回波值不稳定与海冰实测样本量匮乏。     

Geophysics of sea ice in the Baltic Sea: A review

With improved observation methods, increased winter navigation, and increased awareness of the climate and environmental changes, research on the Baltic Sea ice conditions has become increasingly active. Sea ice has been recognized as a sensitive indicator for changes in climate. Although the inter-annual variability in the ice conditions is large, a change towards milder ice winters has been detected from the time series of the maximum annual extent of sea ice and the length of the ice season. On the basis of the ice extent, the shift towards a warmer climate took place in the latter half of the 19th century. On the other hand, data on the ice thickness, which are mostly limited to the land-fast ice zone, basically do not show clear trends during the 20th century, except that during the last 20 years the thickness of land-fast ice has decreased. Due to difficulties in measuring the pack-ice thickness, the total mass of sea ice in the Baltic Sea is, however, still poorly known. The ice extent and length of the ice season depend on the indices of the Arctic Oscillation and North Atlantic Oscillation. Sea ice dynamics, thermodynamics, structure, and properties strongly interact with each other, as well as with the atmosphere and the sea. The surface conditions over the ice-covered Baltic Sea show high spatial variability, which cannot be described by two surface types (such as ice and open water) only. The variability is strongly reflected to the radiative and turbulent surface fluxes. The Baltic Sea has served as a testbed for several developments in the theory of sea ice dynamics. Experiences with advanced models have increased our understanding on sea ice dynamics, which depends on the ice thickness distribution, and in turn redistributes the ice thickness. During the latest decade, advance has been made in studies on sea ice structure, surface albedo, penetration of solar radiation, sub-surface melting, and formation of superimposed ice and snow ice. A high vertical resolution has been found as a prerequisite to successfully model thermodynamic processes during the spring melt period. A few observations have demonstrated how the river discharge and ice melt affect the stratification of the oceanic boundary layer below the ice and the oceanic heat flux to the ice bottom. In general, process studies on ice–ocean interaction have been rare. In the future, increasingly multidisciplinary studies are needed with close links between sea ice physics, geochemistry and biology.     

北冰洋高纬度区域海冰及气象特征分析

基于2018年8月至2019年5月布放在北极随海冰漂流的自动气象站和温度链浮标获取的观测数据,分析了北极高纬度区域的大气特征和海冰生消过程。根据海冰的漂移轨迹分为两个阶段分析,第1阶段,海冰主要向东南漂移;第2阶段,海冰主要向东北漂移。第1阶段观测的平均气温和平均相对湿度分别为–6.6℃和93%,第2阶段观测的平均气温和平均相对湿度分别为–29.3℃和76%,第2阶段平均气压高于第1阶段。海冰的漂移轨迹主要受到波弗特高压外围气流的影响。利用自动气象站漂移轨迹计算得到海冰漂移速度,与美国国家冰雪数据中心海冰漂移速度比较显示,两者纬向速度更为接近。海冰在第1阶段以融化为主,海冰厚度略有减小,8月份海冰生长率为–0.11 cm/d;海冰的生长过程主要发生在第2阶段,1–3月生长率均超过0.9 cm/d,2019年3月海冰生长最快,平均生长率为1.3 cm/d,海冰的增长一直持续至观测结束。     

两种盐度参数化方案在海冰模式中的应用比较

本文详细介绍了SIS海冰模式中引进两种盐度参数化方案即等盐度方案和盐度廓线方案对海冰模拟所存在的差异。利用盐度廓线方案导出的表征盐度与海冰温度间关系的方程比等盐度方案多出一项,将定义为盐度差异项。盐度差异项对海冰厚度的热力作用表现为：在海冰厚度增长季节（11月到次年5月）,盐度差异项通过升高海冰内部温度,抑制海冰增长;在消融的第一阶段（6．8月）,盐度差异项通过升高海冰内部温度加快海冰消融;在消融的第二阶段（9．10月）,盐度差异项通过降低海冰内部的温度抑制海冰消融。但尺度分析表明,盐度差异项要比方程中队海冰温度作用最大项小1．2个量级,如果采用一级近似,可以略去盐度差异项,因此盐度差异项对海冰增长和消融影响很小。同时利用冰洋耦合模式（ModularOceanModel,MOM4）,分别采用两种盐度参数化方案模拟北极海冰厚度和海冰密集度的季节性变化,模拟结果也表明两种方案模拟得到的海冰厚度和海冰密集度的季节性变化相差甚小。