基于冰基浮标数据的2018−2019年北极海冰运动特性时空变化分析

海冰运动是影响北极海冰平流输运和物质平衡空间重新分布的重要因素。本研究基于2018年9月至2019年8月期间北冰洋66个冰基浮标位置记录数据,结合大气再分析数据,计算得到了海冰运动速度、冰速与风速的比值和海冰运动惯性强度,以刻画北极海冰运动学特征参数在一个冰季的时空变化,并讨论了不同区域冰速与风速比与海冰密集度的关联性。海冰漂移速度在波弗特–楚科奇海、东北极中央区和西北极中央区呈秋冬降低春夏升高的季节变化特征。格陵兰海月均海冰漂移速度((0.32±0.06)m/s)最大,其次是弗拉姆海峡((0.17±0.07)m/s)和波弗特–楚科奇海((0.14±0.05)m/s),而东北极中央区((0.09±0.02)m/s)和西北极中央区((0.07±0.03)m/s)较低。在月尺度上,冰漂移速度与风速的比值主要受海冰漂移速度支配。弗拉姆海峡和格陵兰海受较强的表层海流影响,冰速与风速比值较大,西北极中央区、东北极中央区和波弗特–楚科奇海的冰速与风速比值随着海冰密集度的增加趋近,并分布在0~0.02之间。所有浮标的月平均惯性运动指数为0.158±0.144,秋冬季过渡期间,海冰对风的响应以及海冰运动的惯性信号逐渐减弱,春–夏季随着海冰融化又开始增强,因此上述两个参数都可以作为指示海冰冰场固结程度的重要指标。

Arctic summertime anticyclonic circulation mode and its influence on substantial sea ice depletion:a review

The summertime anticyclonic circulation mode(SACM)is related to recent substantial loss of sea ice in the Arctic.This review outlines the potential causes of the SACM and considers its influence on sea ice depletion.Local triggers(i.e.,sea ice loss and sea surface temperature(SST)variation)and spatiotemporal teleconnections(i.e.,extratropical cyclone intrusion,tropical and mid-latitude SST anomalies,and winter atmospheric circulation preconditions)are discussed.The influence of the SACM on the dramatic loss of sea ice is emphasized through inspection of relevant dynamic(i.e.,Ekman drift and export)and thermodynamic(i.e.,moisture content,cloudiness,and associated changes in radiation)mechanisms.Moreover,the motivation for investigation of the underlying physical mechanisms of the SACM in response to the recent substantial sea ice depletionis also clarified through an attempt to better understand the shifting ice-atmosphere interaction in the Arctic during summer.Therecord low extent of sea ice in September 2012 could be reset in the near future if the SACM-like scenario continues to exist during summer in the Arctic troposphere.

融冰期北极海冰单轴压缩强度的试验研究

为了评估融冰期北极海冰的单轴压缩强度,其中在中国第七次北极科学考察期间,现场钻取冰芯,测量冰层温度、盐度、密度和晶体结构;在低温实验室内将冰芯加工成标准试样并测量单轴压缩强度,其中试验应变速率为10^(-7)～10^(-2)s^(-1),温度分别为-3℃、-6℃和-9℃,加载方向为垂直冰面加载。试验结果表明:融冰期北极海冰表现出高温、低盐、低密度的物理性质;随应变速率增加,单轴压缩强度先增加再降低最后稳定,试样破坏形态由主裂缝贯穿转变为产生较多微裂缝;随孔隙率增加,单轴压缩强度降低。试验建立了以应变速率和孔隙率评估海冰单轴压缩强度的计算模型,通过冰层物理参数计算孔隙率,给出了融冰期北极冰层垂直方向的极限单轴压缩强度参考值。

中国物理海洋学研究70年：发展历程、学术成就概览

本文概略评述新中国成立70年来物理海洋学各分支研究领域的发展历程和若干学术成就。中国物理海洋学研究起步于海浪、潮汐、近海环流与水团,以及以风暴潮为主的海洋气象灾害的研究。随着国力的增强,研究领域不断拓展,涌现了大量具有广泛影响力的研究成果,其中包括:提出了被国际广泛采用的“普遍风浪谱”和“涌浪谱”,发展了第三代海浪数值模式;提出了“准调和分析方法”和“潮汐潮流永久预报”等潮汐潮流的分析和预报方法;发现并命名了“棉兰老潜流”,揭示了东海黑潮的多核结构及其多尺度变异机理等,系统描述了太平洋西边界流系;提出了印度尼西亚贯穿流的南海分支(或称南海贯穿流);不断完善了中国近海陆架环流系统,在南海环流、黑潮及其分支、台湾暖流、闽浙沿岸流、黄海冷水团环流、黄海暖流、渤海环流,以及陆架波方面均取得了深刻的认识;从大气桥和海洋桥两个方面对太平洋–印度洋–大西洋洋际相互作用进行了系统的总结;发展了浅海水团的研究方法,基本摸清了中国近海水团的分布和消长特征与机制,在大洋和极地水团分布及运动研究方面也做出了重要贡献;阐明了南海中尺度涡的宏观特征和生成机制,揭示了中尺度涡的三维结构,定量评估了其全球物质与能量输运能力;基本摸清了中国近海海洋锋的空间分布和季节变化特征,提出了地形、正压不稳定和斜压不稳定等锋面动力学机制;构建了“南海内波潜标观测网”,实现了对内波生成–演变–消亡全过程机理的系统认识;发展了湍流的剪切不稳定理论,提出了海流“边缘不稳定”的概念,开发了海洋湍流模式,提出了湍流混合参数化的新方法等;在海洋内部混合机制和能量来源方面取得了新的认识,并阐述了混合对海洋深层环流、营养物质输运等过程的影响;研发了全球浪–潮–流耦合模式,推出一系列海洋与气候模式;发展了可同化主要海洋观测数据的海洋数据同化系统和用于ENSO预报的耦合同化系统;建立了达到国际水准的非地转(水槽/水池)和地转(旋转平台)物理模型实验平台;发展了ENSO预报的误差分析方法,建立了海洋和气候系统年代际变化的理论体系,揭示了中深层海洋对全球气候变化的响应;初步建成了中国近海海洋观测网;持续开展南北极调查研究;建立了台风、风暴潮、巨浪和海啸的业务化预报系统,为中国气象减灾提供保障;突破了国外的海洋技术封锁,研发了万米水深的深水水听器和海洋光学特性系列测量仪器;建立了溢油、危险化学品漂移扩散等预测模型,为伴随海洋资源开发所带来的风险事故的应急处理和预警预报提供科学支撑。文中引用的大量学术成果文献(每位第一作者优选不超过3篇)显示,经过70年的发展,中国物理海洋学研究培养了一支实力雄厚的科研队伍,这是最宝贵的成果。这支队伍必将成为中国物理海洋学研究攀登新高峰的主力军。

适应极地快速变化海冰模式的研发与挑战

极地海冰是地球气候系统的重要组成部分,也是气候环境变化的指示器和放大器。极地海冰复杂的多尺度物理过程和极地观测资料的匮乏,给海冰模式的研发带来了巨大的挑战。在过去的半个多世纪中,大气-海冰-海洋的复杂相互作用和冰内物理过程在海冰模式中的数学描述取得了重大的进展,但海冰模式对一些重要物理过程的描述仍很不完善,尤其是近年来极地海冰的快速变化及其物理特性的变化,极大地增加了海冰模式物理参数化方案和模拟结果的不确定性。因此,迫切需要具备完善物理过程、适应海冰多尺度快速变化的高分辨率海冰模式,并应用于全球气候变化的研究和预测以及极地的开发利用。本文从海冰模式的发展历程和现状、极地海冰快速变化给海冰模式带来的挑战以及适应极地快速变化海冰模式的改进和发展研究方向三个方面进行了阐述和讨论。

基于BIM技术的施工成本控制研究

将BIM技术引入到建设项目施工成本控制中,构建基于BIM技术的成本控制体系。依据某市文化馆项目的实际情况,建立5D BIM模型,并在此基础上构建基于BIM技术的施工成本控制系统模型,设计成本监控、成本预警及成本预测的系统功能,以期提高工程项目的资源利用率。

The physical structures of snow and sea ice in the Arctic section of 150°-180°W during the summer of 2010

The physical structures of snow and sea ice in the Arctic section of 150°-180°W were observed on the basis of snow-pit, ice-core, and drill-hole measurements from late July to late August 2010. Almost all the in- vestigated floes were first-year ice, except for one located north of Alaska, which was probably multi-year ice transported from north of the Canadian Arctic Archipelago during early summer. The snow covers over all the investigated floes were in the melting phase, with temperatures approaching 0℃and densities of 295-398 kg/m3. The snow covers can be divided into two to five layers of different textures, with most cases having a top layer of fresh snow, a round-grain layer in the middle, and slush and/or thin icing layers at the bottom. The first-year sea ice contained about 7%-17% granular ice at the top. There was no granular ice in the lower layers. The interior melting and desalination of sea ice introduced strong stratifications of temper- ature, salinity, density, and gas and brine volume fractions. The sea ice temperature exhibited linear cooling with depth, while the salinity and the density increased linearly with normalized depth from 0.2 to 0.9 and from 0 to 0.65, respectively. The top layer, especially the freeboard layer, had the lowest salinity and density, and consequently the largest gas content and the smallest brine content. Both the salinity and density in the ice basal layer were highly scattered due to large differences in ice porosity among the samples. The bulk average sea ice temperature, salinity, density, and gas and brine volume fractions were -0.8℃, 1.8, 837 kg/m3, 9.3% and 10.4%, respectively. The snow cover, sea ice bottom, and sea ice interior show evidences of melting during mid-August in the investigated floe located at about 87°N, 175°W.

Crucial physical characteristics of sea ice in the Arctic section of 143°–180°W during August and early September 2008

Sea-ice physical characteristics were investigated in the Arctic section of 143^-180~W during Au- gust and early September 2008. Ship-based observations show that both the sea-ice thickness and concentration recorded during southward navigation from 30 August to 6 September were remark- ably less than those recorded during northward navigation from 3 to 30 August, especially at low latitudes. Accordingly, the marginal ice zone moved from about 74.0~N to about 79.5~N from mid-August to early September. Melt-pond coverage increased with increasing latitude~ peaking at 84.4~N, where about 27% of ice was covered by melt ponds. Above this latitude, melt-pond coverage decreased evidently as the ice at high latitudes experienced a relatively short melt season and commenced its growth stage by the end of August. Regional mean ice thickness increased from 0.8 （~=0.5） m at 75.0~N to 1.5 （＋0.4） m at 85.0~N along the northward navigation while it decreased rapidly to 0.6 （-t-0.3） m at 78.0~N along the southward navigation. Because of relatively low ice concentration and thin ice in the investigated Arctic sector, both the short-term ice stations and ice camp could only be set up over multiyear sea ice. Observations of ice properties based on ice cores collected at the short-term ice stations and the ice camp show that all investigated floes were essentially isothermal with high temperature and porosity, and low density and salinity. Most ices had salinity below 2 and mean density of 800-860 kg/m3. Significant ice loss in the investigated Arctic sector during the last 15 a can be identified by comparison with the previous observations.

The uniaxial compressive strength of the Arctic summer sea ice

The results on the uniaxial compressive strength of Arctic summer sea ice are presented based on the sam- ples collected during the fifth Chinese National Arctic Research Expedition in 2012 （CHINARE-2012）. Exper- imental studies were carried out at different testing temperatures （-3, -6 and -9℃）, and vertical samples were loaded at stress rates ranging from 0.001 to 1 MPa/s. The temperature, density, and salinity of the ice were measured to calculate the total porosity of the ice. In order to study the effects of the total porosity and the density on the uniaxial compressive strength, the measured strengths for a narrow range of stress rates from 0.01 to 0.03 MPa/s were analyzed. The results show that the uniaxial compressive strength decreases linearly with increasing total porosity, and when the density was lower than 0.86 g/cm3, the uniaxial com- pressive strength increases in a power-law manner with density. The uniaxial compressive behavior of the Arctic summer sea ice is sensitive to the loading rate, and the peak uniaxial compressive strength is reached in the brittle-ductile transition range. The dependence of the strength on the temperature shows that the calculated average strength in the brittle-ductile transition range, which was considered as the peak uniaxial compressive strength, increases steadily in the temperature range from -3 to -9℃.

中国第9次北极科学考察简报

中国第9次北极科学考察是自然资源部组建后组织实施的第一次极地考察。本次考察队共有131名队员组成,包括1名来自美国特拉华大学的科学家和2名来自法国巴黎第6大学的科学家。2018年7月20日,雪龙船离开上海码头,至9月26日考察结束,历时69天。

Review of research on Arctic sea ice physics based on the Chinese National Arctic Research Expedition

China launched its Arctic research program and organized the first Chinese National Arctic Research Expedition （CHINARE-Arctic） in 1999. By 2016, six further expeditions had been conducted using the R/V Xuelong. The main region of the expeditions has focused on the Pacific sector of the Arctic Ocean for sea ice observations. The expeditions have used icebreaker, helicopter, boat, floe, and buoy platforms to perform these observations. Some new technologies have been developed, in particular, the underway auto-observing system for sea ice thickness using an electromagnetic instrument. The long-term measurement systems, e.g., the sea ice mass balance buoy, allow observations to extend from summer to winter. Some international cooperation projects have been involved in CHINARE-Arctic, especially the ＂Developing Arctic Modeling and Observing Capabilities for Long-Term Environmental Studies＂ project funded by the European Union during the International Polar Year. Arctic sea ice observations have been used to verify remote sensing products, identify changes in Arctic sea ice, optimize the parameterizations of sea ice physical processes, and assess the accessibility of ice-covered waters, especially around the Northeast Passage. Recommendations are provided as guidance to future CHINARE-Arctic projects. For example, a standardized operation system of sea ice observations should be contracted, and the observations of sea ice dynamics should be enhanced. The upcoming launch of a new Chinese icebreaker will allow increased ship time in support of future CHINARE Arctic oceanographic investigations.

中国第9次北极考察概述

中国第9次北极考察航次于2018年7月20日至9月26日执行,在白令海、楚科奇海、楚科奇海台、门捷列夫海岭和加拿大海盆开展了物理海洋、海洋气象、海冰、海洋化学、海洋生物、海洋生态、地质和地球物理等多学科综合考察。本文对中国第9次北极考察取得的主要成果进行了概述。

Investigation of the thermodynamic processes of a floe-lead system in the central Arctic during later summer

Thermodynamic processes of a system involving a floe and a small lead in the central Arctic were investigated during the ice-camp period of the third Chinese National Arctic Research Expedition from 20 to 28 August, 2008. The measurements included surface air temperatures above the floe, spectral albedo of the lead, seawater temperatures in the lead and under the ice cover, and the lateral and bottom mass balance of the floe. The surface air temperature at 1.15 m remained below 0~Cthroughout the observation period and sea ice had commenced its annual cycle of growth in response to autumn cooling during the study. The surface of the lead was frozen by 23 August, after which the spectral albedo of the thin-ice-covered lead in the band of 320-950 nm was 0.46 -0.03, the seawater temperatures both in the lead and under the ice cover, as well as the vertical seawater-temperature gradient in the lead decreased gradually, and the oceanic heat under the ice was maintained at a low level approaching 0 W/m2. By the end of the measurement, the thickness of the investigated floe had reached its annual minimum, while the lateral of the floe was still in the melting phase, with a mean melting rate of 1.0±0.3 cm/d during the measurement, responding to an equivalent latent heat flux of 21 ±6 W/m2. The lateral melting of the floe had made a more significant contribution to the sea-ice mass balance than the surface and bottom melting in the end of August.

A concept for autonomous and continuous observation of melt pond morphology: Instrument design and test trail during the 4th CHINARE-Arctic in 2010

Accelerated decline of summer and winter Arctic sea ice has been demonstrated progressively. Melt ponds play a key role in enhancing the feedback of solar radiation in the ice/ocean-atmosphere system, and have thus been a focus of researchers and modelers. A new melt pond investigation system was designed to determine morphologic and hydrologic features, and their evolution. This system consists of three major parts： Temperature-salinity measuring, surface morphology monitoring, and water depth monitoring units. The setup was deployed during the ice camp period of the fourth Chinese National Arctic Research Expedition in summer 2010. The evolution of a typical Arctic melt pond was documented in terms of pond depth, shape and surface condition. These datasets are presented to scientifically reveal how involved parameters change, contributing to better understanding of the evolution mechanism of the melt pond. The main advantage of this system is its suitability for autonomous and long-term observation, over and within a melt pond. Further, the setup is portable and robust. It can be easily and quickly installed, which is most valuable for deployment under harsh conditions.

冬季白令海海冰范围变化及其对大气响应机制研究

白令海是冬季北极海冰变化最明显的区域之一,该区域海冰的季节和长期变化与局地的气候、水文环境和生态系统密切相关,并会影响我国的天气气候过程。为了识别该区冬季海冰的长期变化,基于Hadley中心数据,采用滑动t检验和线性回归分析方法对白令海1960–2020年海冰范围的变化趋势及其空间差异进行分析,并分析了海冰变化对大气环流等大气强迫的影响。结果表明:白令海冬季海冰范围在1960–2020年显著减小,20世纪70年代和2000年前后白令海海冰范围存在显著的均值突变。其过程中伴随着阿留申低压中心低压加强、核心位置向白令海西部偏移以及对应风场分布的变化,这个过程存在一个近20 a周期的振荡。同时,太平洋年代际震荡的相位变化可以通过改变海平面气压来调节经向风,改变进入白令海的热平流,进而影响白令海冬季海冰范围。因此,阿留申低压系统和北太平洋年代际振荡对冬季白令海海冰的变化起到重要的调节作用。

Aerial observations of sea ice and melt ponds near the North Pole during CHINARE2010

An aerial photography has been used to provide validation data on sea ice near the North Pole where most polar orbiting satellites cannot cover. This kind of data can also be used as a supplement for missing data and for reducing the uncertainty of data interpolation. The aerial photos are analyzed near the North Pole collected during the Chinese national arctic research expedition in the summer of 2010（CHINARE2010）. The result shows that the average fraction of open water increases from the ice camp at approximately 87°N to the North Pole, resulting in the decrease in the sea ice. The average sea ice concentration is only 62.0% for the two flights（16 and 19 August 2010）. The average albedo（0.42） estimated from the area ratios among snow-covered ice,melt pond and water is slightly lower than the 0.49 of HOTRAX 2005. The data on 19 August 2010 shows that the albedo decreases from the ice camp at approximately 87°N to the North Pole, primarily due to the decrease in the fraction of snow-covered ice and the increase in fractions of melt-pond and open-water. The ice concentration from the aerial photos and AMSR-E（The Advanced Microwave Scanning Radiometer-Earth Observing System） images at 87.0°–87.5°N exhibits similar spatial patterns, although the AMSR-E concentration is approximately 18.0%（on average） higher than aerial photos. This can be attributed to the 6.25 km resolution of AMSR-E, which cannot separate melt ponds/submerged ice from ice and cannot detect the small leads between floes. Thus, the aerial photos would play an important role in providing high-resolution independent estimates of the ice concentration and the fraction of melt pond cover to validate and/or supplement space-borne remote sensing products near the North Pole.

Features of sea ice motion observed with ice buoys from the central Arctic Ocean to Fram Strait

Using six ice-tethered buoys deployed in 2012,we analyzed sea ice motion in the central Arctic Ocean and Fram Strait.The two-hourly buoy-derived ice velocities had a magnitude range of 0.010.80 m s 1,although ice velocities within the Arctic Basin were generally less than 0.4 m s 1.Complex Fourier transformation showed that the amplitudes of the sea ice velocities had a non-symmetric inertial oscillation.These inertial oscillations were characterized by a strong peak at a frequency of approximately 2 cycle d 1 on the Fourier velocity spectrum.Wind was a main driving force for ice motion,characterized by a linear relationship between ice velocity and 10-m wind speed.Typically,the ice velocity was about 1.4%of the 10-m wind speed.Our analysis of ice velocity and skin temperature showed that ice velocity increased by nearly 2%with each 10℃increase in skin temperature.This was likely related to weakened ice strength under increasing temperature.The ice-wind turning angle was also correlated with 10-m wind speed and skin temperature.When the wind speed was less than 12 m s 1 or skin temperature was less than 30℃,the ice-wind turning angle decreased with either increasing wind speed or skin temperature.Clearly,sea ice drift in the central Arctic Ocean and Fram Strait is dependent upon seasonal changes in both temperature and wind speed.

Thermodynamic processes of lake ice and landfast ice around Zhongshan Station, Antarctica

Thermodynamic processes of ice in three lakes and landfast ice around Zhongshan Station, Antarctica, were observed in 2006. The mass balance of lake ice was compared with that of landfast ice. The responses of lake ice and sea ice temperatures to the local surface air temperature are explored. Vertical conductive heat fluxes at varying depths of lake ice and sea ice were derived from vertical temperature profiles. The freeze up of lake ice and landfast ice occurred from late February to early March. Maximum lake ice thicknesses occurred from late September to early October, with values of 156-177 cm. The maximum sea ice thicknesses of 167-174 cm occurred relatively later, from late October to late November. Temporal variations of lake ice and landfast ice internal temperatures lagged those of air temperatures. High-frequency variations of air temperature were evidently attenuated by ice cover. The temporal lag and the high-frequency attenuation were greater for sea ice than for lake ice, and more distinct for the deeper ice layer than for the upper ice layer. This induced a smaller conductive heat flux through sea ice than lake ice, at the same depth and under the same atmospheric forcing, and a smoother fluctuation in the conductive heat flux for the deeper ice layer than for the upper ice layer. Enhanced desalination during the melt season increased the melting point temperature within sea ice, making it different from fresh lake ice.

Physics of Arctic landfast sea ice and implications on the cryosphere: an overview

Landfast sea ice(LFSI)is a criticalcomponent of the Arctic sea ice cover,and is changing as a result of Arctic amplification of climate change.Located in coastal areas,LFSI is of great significance to the physical and ecological systems of the Arctic shelf and in local indigenous communities.We present an overview of the physics of Arctic LFSI and the associated implications on the cryosphere.LFSI is kept in place by four fastenmechanisms.The evolution of LFSI is mostly determined by thermodynamic processes,and can therefore be usedas an indicator of local climate change.We also present the dynamic processes that are active prior to the formation of LFSI,and those that are involved in LFSI freeze-up and breakup.Season length,thickness and extent of Arctic LFSI are decreasing andshowing different trends in different seas,and therefore,causing environmental and climatic impacts.An improved coordination of Arctic LFSI observation is needed with a unified and systematic observation network supported by cooperation between scientists and indigenous communities,as well as a better application of remote sensing data to acquire detailed LFSI cryosphere physical parameters,hence revolving both its annual cycle and long-term changes.Integrated investigations combining in situ measurements,satellite remote sensing and numerical modeling are needed to improve our understanding of the physical mechanisms of LFSI seasonal changes and their impacts on the environment and climate.

An outstanding example of cooperation between Arctic and non-Arctic countries in cryosphere and climate research: Sino-Finnish cooperation for more than 30 years

The cryosphere is interconnected with other components of the climate system through global exchange of water,energy,and carbon.Long-term sustainable and pragmatic scientific and technological cooperation on the cryosphere and climatology in polar and sub-polar regions between China and Finland began in the 1980s.The fields of bilateral cooperation include joint training of young scientists,joint field observations,climatological and ecological researches of polar and sub-polar sea ice,glaciers and frozen lakes,etc.The year 2020 marked the 70th anniversary of the establishment of diplomatic relations between China and Finland.In order to celebrate the great achievements by Chinese and Finnish scientists in the fieldsof cryosphere and climate research,the Advances in Polar Science invited scientists from both sides to jointly organize a Special Issue entitled“Sino-Finnish cooperation on cryosphere and climatology in polar and sub-polar regions”.In this Special Issue,we have collected 10 papers,with most papers created jointly by scientists of both sides.The fruitful scientific achievement is strongly benefited from the sustainability of cooperation.Monitoring,research,prediction,mitigation,and adaptation to the climate change in the polar and sub-polar regions will definitively stay in the focus for many decades to come.A new era of Finnish-Chinese scientific collaboration on cryosphere has begun.