心存质疑、追求证据、秉持客观--面对北极气候变化

气候变化是地球发生的重大环境事件。最近几十年来,科学家目睹了气候变化对全球环境产生的影响,得到世界各国政府的密切关注。在北极,情况也变得越来越严峻,冰雪在不断减少,而失去冰雪的北极就等于失去了灵魂。其实,在全球变暖过程中以北极变暖最为显著,这是科学界早就认识到的。尽管如此,真相仍超出人们预料:数据表明,北极地区的升温速度至少是全球平均值的2倍,这一剧烈的增暖现象被称为“北极放大效应”。

北极三维云结构的时空变化:季节变化

本文基于2007-2020年多年气候月平均的CALIPSO云量的三维空间数据,研究了北极云量三维结构的气候态及季节变化特征。结果表明,北极的云量主要分布在大气边界层和对流层中,从边界层向上云量递减;水平空间分布主要表现出显著的海陆差异,云量最大值出现在北极大西洋扇区;垂向结构表现出对流层上下同位相变化的正压结构和低空大气边界层与对流层中上层反位相变化的一阶斜压模结构,在边界层中北冰洋海洋上空的云量大于北极陆地上空的云量,而在对流层中上层则正好相反。北极云量主要呈现出单峰型的季节变化特征, 2-3月云量最少, 9月云量最多。北极云量的季节变化主要体现在低空大气边界层云量的两个时空主模态变化中,第一模态主要反映了北极融冰期(5-10月)和结冰期(11月至次年4月)云量的反位相变化,方差贡献为59.35%;第二模态则主要体现了深秋(10-11月)和初夏(6-7月)北极地区海陆差异的反位相变化特征,方差贡献为19.22%。

中国第1-10次北极科学考察走航自动气象站观测数据集(1999-2019年)

气象数据是地球系统科学重要的基础性数据之一。在1999–2019年间中国北极科学考察的10个航次中,利用船载自动气象站(Lica-701、Vaisala MILOS500、天诺CR3000和XZC6-1)采集了走航气象数据。本研究对中国第1–10次北极考察走航气象数据进行了标准化整理、质量控制和评估,形成本数据集,主要包括气温、相对湿度、气压、风向和风速5个气象要素,共有20个气象数据文件,数据时间分辨率为1小时。本数据集能够为深入了解北极区域气候变化、研究北极区域天气变化过程及评估气候变化对生态环境影响等研究提供数据支撑。

基于船基图像的北极冰面融池形态研究

基于中国第12次北极科学考察期间获取的船侧倾斜拍摄海冰图像,研究了北极冰面融池大小和形态参数的空间分布及统计特征。应用自动检测算法将图像划分为水、冰、融池三种表面类别,经倾斜校正后计算每种类别的面积分数及单个融池的大小和形态。结果显示,融池的面积分数随纬度升高先增大后减小,较短的融化时间和较早的再冻结导致高纬度地区融池面积分数一直较低。融池的面积、周长和平均钳测直径随纬度升高具有相似变化规律,均为先增大后减小。不同大小融池面积的频率分布与幂律函数相吻合,对应指数均在1.4~1.8范围内,具有一定相似性。融池的分形维数随纬度升高分布较均匀,而周长与面积比值随纬度变化较大。不同纬度融池边缘凸度与圆形的对应值π相差较大,而各纬度融池圆度平均值为2.39±0.23;融池圆度和凸度与其面积成正比,周长与面积比值则与融池面积成反比,表明融池边缘随着融池面积增加而变得更长更曲折。冰面融池变化引起的平均海表反照率空间差异较大,随着纬度升高在0.24~0.67之间变化,变化率为0.10(°N)^(-1)。本文研究的融池大小和形态参数可为融池演变模拟及遥感反演算法改进提供重要观测依据和地面验证。

Arctic Sea Ice Variations in the First Half of the 20th Century:A New Reconstruction Based on Hydrometeorological Data

The shrinking Arctic sea-ice area(SIA) in recent decades is a striking manifestation of the ongoing climate change.Variations of the Arctic sea ice have been continuously observed by satellites since 1979, relatively well monitored since the 1950s, but are highly uncertain in the earlier period due to a lack of observations. Several reconstructions of the historical gridded sea-ice concentration(SIC) data were recently presented based on synthesized regional sea-ice observations or by applying a hybrid model–empirical approach. Here, we present an SIC reconstruction for the period1901–2019 based on established co-variability between SIC and surface air temperature, sea surface temperature, and sea level pressure patterns. The reconstructed sea-ice data for March and September are compared to the frequently used Had ISST1.1 and SIBT1850 datasets. Our reconstruction shows a large decrease in SIA from the 1920 to 1940 concurrent with the Early 20th Century Warming event in the Arctic. Such a negative SIA anomaly is absent in Had ISST1.1 data. The amplitude of the SIA anomaly reaches about 0.8 mln km^(2) in March and 1.5 mln km^(2) in September. The anomaly is about three times stronger than that in the SIBT1850 dataset. The larger decrease in SIA in September is largely due to the stronger SIC reduction in the western sector of the Arctic Ocean in the 70°–80°N latitudinal zone. Our reconstruction provides gridded monthly data that can be used as boundary conditions for atmospheric reanalyses and model experiments to study the Arctic climate for the first half of the 20th century.

东西伯利亚陆架炭屑分布特征及其控制因素

炭屑是指示火灾事件的重要指标。全球变暖背景下,环北极地区野火频发,了解炭屑的产生、迁移和埋藏对理解北极气候变化的环境效应及陆源碳源汇过程具有重要意义,而前人对北极海域的炭屑研究十分匮乏。东西伯利亚陆架是全球最大的陆架区,接收和封存着巨量的陆源碳,也是海冰融化、沿岸侵蚀、周边野火频发最显著的地区,因此成为研究北极炭屑记录的重要区域。本文基于2016年首次中俄北极联合科学考察取得的表层沉积物样品,研究了东西伯利亚陆架区不同粒度炭屑的空间分布特征、输运方式及其控制因素。结果表明,东西伯利亚陆架区表层沉积物中炭屑总浓度为4.4×10^(4)~4.1×10^(6)粒·g^(–1),平均浓度为9.3×10^(5)粒·g^(–1)。沉积物中炭屑呈现近岸粗、远岸细的总体分布特征。由于受到水动力、大气等长距离搬运,研究区炭屑颗粒以超细粒为主(平均占83%)。河口水动力作用、沿岸侵蚀、大气传输、海冰搬运、水平向和垂向上的海流搬运等多重控制因素,可能共同影响炭屑的跨陆架输运过程。

A progress review of black carbon deposition on Arctic snow and ice and its impact on climate change

The rapid warming of the Arctic,accompanied by glacier and sea ice melt,has significant consequences for the Earth’s climate,ecosystems,and economy.Black carbon(BC)deposition on snow and ice can trigger a significant reduction in snow albedo and accelerate melting of snow and ice in the Arctic.By reviewing the published literatures over the past decades,this work provides an overview of the progress in both the measurement and modeling of BC deposition and its impact on Arctic climate change.In summary,the maximum value of BC deposition appears in the western Russian Arctic(26 ng·g^(–1)),and the minimum value appears in Greenland(3 ng·g^(–1)).BC records in the Arctic ice core already peaked in 1920s and 1970s,and shows a regional difference between Greenland and Canadian Arctic.The different temporal variations of Arctic BC ice core records in different regions are closely related to the large variability of BC emissions and transportation processes across the Arctic region.Model simulations usually underestimate the concentration of BC in snow and ice by 2–3 times,and cannot accurately reflect the seasonal and regional changes in BC deposition.Wet deposition is the main removal mechanism of BC in the Arctic,and observations show different seasonal variations in BC wet deposition in Ny-Ålesund and Barrow.This discrepancy may result from varying contributions of anthropogenic and biomass burning(BB)emissions,given the strong influence by BC from BB emissions at Barrow.Arctic BC deposition significantly influences regional climate change in the Arctic,increasing fire activities in the Arctic have made BB source of Arctic BC more crucial.On average,BC in Arctic snow and ice causes an increase of+0.17 W·m^(–2)in radiative forcing and 8 Gt·a^(–1)in runoff in Greenland.As stressed in the latest Arctic Monitoring and Assessment Programme report,reliable source information and long-term and high-resolution observations on Arctic BC deposition will be crucial for a more comprehensive understanding and a better mitigation strategy of Arctic BC.In the future,it is necessary to collect more observations on BC deposition and the corresponding physical processes(e.g.,snow/ice melting,surface energy balance)in the Arctic to provide reliable data for understanding and clarifying the mechanism of the climatic impacts of BC deposition on Arctic snow and ice.

Recent Ventures in Interdisciplinary Arctic Research:The ARCPATH Project

This paper celebrates Professor Yongqi GAO's significant achievement in the field of interdisciplinary studies within the context of his final research project Arctic Climate Predictions: Pathways to Resilient Sustainable Societies-ARCPATH(https://www.svs.is/en/projects/finished-projects/arcpath). The disciplines represented in the project are related to climatology, anthropology, marine biology, economics, and the broad spectrum of social-ecological studies. Team members were drawn from the Nordic countries, Russia, China, the United States, and Canada. The project was transdisciplinary as well as interdisciplinary as it included collaboration with local knowledge holders. ARCPATH made significant contributions to Arctic research through an improved understanding of the mechanisms that drive climate variability in the Arctic. In tandem with this research, a combination of historical investigations and social, economic, and marine biological fieldwork was carried out for the project study areas of Iceland, Greenland, Norway, and the surrounding seas, with a focus on the joint use of ocean and sea-ice data as well as social-ecological drivers. ARCPATH was able to provide an improved framework for predicting the near-term variation of Arctic climate on spatial scales relevant to society, as well as evaluating possible related changes in socioeconomic realms. In summary, through the integration of information from several different disciplines and research approaches, ARCPATH served to create new and valuable knowledge on crucial issues, thus providing new pathways to action for Arctic communities.

Spatiotemporal variation and freeze-thaw asymmetry of Arctic sea ice in multiple dimensions during 1979 to 2020

Arctic sea ice is broadly regarded as an indicator and amplifier of global climate change.The rapid changes in Arctic sea ice have been widely concerned.However,the spatiotemporal changes in the horizontal and vertical dimensions of Arctic sea ice and its asymmetry during the melt and freeze seasons are rarely quantified simultaneously based on multiple sources of the same long time series.In this study,the spatiotemporal variation and freeze-thaw asymmetry of Arctic sea ice were investigated from both the horizontal and vertical dimensions during 1979–2020 based on remote sensing and assimilation data.The results indicated that Arctic sea ice was declining at a remarkably high rate of–5.4×10^(4) km^(2)/a in sea ice area(SIA)and–2.2 cm/a in sea ice thickness(SIT)during 1979 to 2020,and the reduction of SIA and SIT was the largest in summer and the smallest in winter.Spatially,compared with other sub-regions,SIA showed a sharper declining trend in the Barents Sea,Kara Sea,and East Siberian Sea,while SIT presented a larger downward trend in the northern Canadian Archipelago,northern Greenland,and the East Siberian Sea.Regarding to the seasonal trend of sea ice on sub-region scale,the reduction rate of SIA exhibited an apparent spatial heterogeneity among seasons,especially in summer and winter,i.e.,the sub-regions linked to the open ocean exhibited a higher decline rate in winter;however,the other sub-regions blocked by the coastlines presented a greater decline rate in summer.For SIT,the sub-regions such as the Beaufort Sea,East Siberian Sea,Chukchi Sea,Central Arctic,and Canadian Archipelago always showed a higher downward rate in all seasons.Furthermore,a striking freeze-thaw asymmetry of Arctic sea ice was also detected.Comparing sea ice changes in different dimensions,sea ice over most regions in the Arctic showed an early retreat and rapid advance in the horizontal dimension but late melting and gradual freezing in the vertical dimension.The amount of sea ice melting and freezing was disequilibrium in the Arctic during the considered period,and the rate of sea ice melting was 0.3×10^(4) km^(2)/a and 0.01 cm/a higher than that of freezing in the horizontal and vertical dimensions,respectively.Moreover,there were notable shifts in the melting and freezing of Arctic sea ice in 1997/2003 and 2000/2004,respectively,in the horizontal/vertical dimension.

基于我国CMIP6模式的北极海冰厚度比较及评价

本文选取了第六次国际耦合模式比较计划(CMIP6)中的8个中国地球气候系统模式,将这些模式的北极海冰厚度与华盛顿大学的PIOMAS海冰厚度同化产品进行对比,评估了所选模式1980-2014年北极海冰厚度多年平均空间分布和长期趋势,并通过泰勒评分法对各模式的模拟能力进行了量化。结果表明,无论3月还是9月,所有模式均与PIOMAS存在差异,偏差位置主要集中在格陵兰岛北部、巴伦支海、白令海峡附近。模式均低估北极3月和9月海冰中心区域厚度,此外还普遍高估3月海冰边缘区厚度。其中空间分布与PIOMAS最为相近的模式为FIO-ESM-2-0,其次为FGOALS-f3-L模式。海冰厚度的长期趋势表明,海冰厚度整体呈下降趋势,并且9月的下降程度明显大于3月,与PIOMAS长期趋势空间分布最为相似的模式为NESM3。在此基础上,本文进一步对比了82°N以北3种大气再分析资料、1种卫星观测产品与8个CMIP6模式的辐射分量,再分析资料及模式间辐射分量有很大的差别,其中有两个模式的辐射存在明显的异常, FGOALS-f3-L模式3月上行短波辐射和CIESM模式9月上行短波辐射严重偏小,这可能是由于模式模拟存在误差。

Interdecadal change and projection of the relationship between spring Arctic Oscillation and summer precipitation in the Yangtze River valley in CMIP6 models

评估了20个CMIP6模式对春季北极涛动(AO)与长江流域夏季降水(YRP)关系的模拟能力.结果表明, 4个模式(ACCESS-ESM1-5, CMC-CM2-SR5, MRI-ESM2-0, NorESM2-LM))能合理模拟出1990年代后期AO-YRP关系的减弱. 1980-1998年,当春季AO位于正位相时,夏季东亚急流北移,长江流域为异常下沉运动,同时西太平洋副热带高压减弱,减少向长江流域的水汽输送,结果导致降水减少. 1999-2014年,上述大气环流与春季AO的联系不显著,从而减弱AO-YRP的关系.利用这四个模式进一步预估了RCP4.5情景下2015-2100年期间AO-YRP的关系.两者在2015-2040年为显著负相关关系,随后再次减弱.

北极冰层反射系数与Lamb波频散的关系

为获得北极冰层反射系数与Lamb波的关系,应用传递矩阵法分析了冰层反射系数实虚部、模值范围与冰层自由Lamb波、漏Lamb波频散的关系。获得了冰层自由Lamb波频散曲线与反射系数的对应关系;针对漏Lamb波相速度大于冰层纵波声速,振动模态无法识别的现象,通过调整冰−水界面耦合条件,得到改进后的漏Lamb波频散方程,获得小角度入射时冰层漏Lamb波振动模态与反射系数的关系,并结合北极跨冰层检波实验数据进行了验证。结果表明,反射系数小于1的频段声波激发了相应频段的冰层Lamb波。此外,根据改进的漏Lamb波频散方程进一步获得了多层冰层漏Lamb波频散曲线。

Methods for ice velocity mapping in West Antarctica using historical optical satellite images

The Antarctic Ice Sheet harbors more than 90%of the Earth ice mass,with significant losses experienced through dynamic thinning,particularly in West Antarctica.The crucial aspect of investigating ice mass balance in historical periods preceding 1990 hinges on the utilization of ice velocities derived from optical satellite images.We employed declassified satellite images and Landsat images with normalized cross correlation based image matching,adopting an adaptive combination of skills and methods to overcome challenges encountered during the mapping of historical ice velocity in West Antarctica.A basin-wide synthesis velocity map encompassing the coastal regions of most large-scale glaciers and ice shelves in West Antarctica has already been successfully generated.Our results for historical ice velocities cover over 70%of the grounding line in most of the West Antarctic basins.Through adjustments,we uncovered overestimations in ice velocity measurements over an extended period,transforming our ice velocity map into a spatially deterministic,temporally average version.Among all velocity measurements,Thwaites Glacier exhibited a notable spatial variation in the fastest ice flowline and velocity distribution.Overestimation distributions on Thwaites Glacier displayed a clear consistency with the positions of subsequent front calving events,offering insights into the instabilities of ice shelves.

Promoting China-U.S.Arctic education cooperation:challenges,opportunities and recommendations

Arctic education refers not only to the teaching,but also to research,communication,dissemination as well as popularization of knowledge related to the Arctic.This article reviews joint efforts between Chinese and American educators and researchers to promote cooperation and understanding in Arctic education and research,and examines the facing challenges of China-U.S.Arctic education cooperation which include current political or economic tensions between the two countries,the differing perspectives and priorities on Arctic policy,the disproportion in Arctic scientific research,different research methodologies and discourse system in social science.This article also argues that there are opportunities for the two countries to cooperate in Arctic education.Common goals and interests in the Arctic,Arctic-dedicated institutions with significant Arctic research capabilities and partnerships around the world provide foundations for Arctic education cooperation.The implementation of a new science-based Arctic treaty of the Arctic Council is an opportunity for China-U.S.Arctic education cooperation.As for future cooperation,it suggests that in addition to promoting the direct bilateral cooperation,cooperation within international cooperation platforms and mechanisms,especially within the Arctic Council also needs to be further promoted.

中国第12次北极科学考察队员医疗资料分析

为提高极地科学考察医疗保障水平,对北极科学考察医疗预防和救治方案提出针对性建议,本研究收集了搭乘“雪龙2”号极地考察船的中国第12次北极科学考察队员在航程中的医疗资料,包括统计就诊人数、各种疾病和外伤例数、各系统疾病和外伤例数及构成比,分析常见疾病和外伤的可能诱发因素。研究发现,在79 d航程期间(2021年7月12日—9月28日),100名中国第12次北极科学考察队员发生疾病和外伤并就诊的有76人(76%);共诊治疾病和外伤143人次(不含复诊),就诊例数前10的疾病和外伤依次为:皮肤损伤、咽炎(并列第1)、软组织损伤、胃炎、上呼吸道感染、手足皲裂或脱皮、失眠、口腔溃疡、视疲劳、痛风、皮癣(并列第10);根据发病系统和专科不同,就诊例数依次为创伤与骨关节疾病、皮肤疾病、耳鼻喉疾病、消化系统疾病、呼吸系统疾病、口腔疾病、眼科疾病、神经心理疾病、代谢与内分泌疾病、心血管疾病、泌尿生殖系统疾病。为此,建议进一步采取职业安全教育、加强安全防护和严格执行作业操作规范以及提高随队医生技能和加强远程医疗等措施。

北极监测与评估计划AMAP最新评估报告解读专栏•编者按

北极地区面积广袤,约有2000多万km2,绝大部分属于冰冻圈地区,包括冰川、冰盖、冻土、海冰、积雪、河湖冰等多种要素。北极变暖导致北极气候环境快速变化、极端事件频发,对人类社会健康福祉等的影响加剧。北极快速变化不仅影响北极地区的气候和生态环境,也影响到中低纬度的天气气候,并涉及到未来的能源资源安全以及北极航道的开发利用。

基于CMIP6模式分析北极典型海区浮游植物藻华模拟误差

在海冰覆盖的极地海区,浮游植物季节性藻华变化呈现典型的单峰特征。由于藻华过程受控于海冰、光照、混合层深度和营养盐供给等多个因素,其发生时间和强度在地球系统模式模拟结果中存在较大的不确定性。本研究选取11种CMIP6地球系统模式结果,以多种类型的观测资料和产品作为判断参考值,评估各模式结果能否准确模拟北极典型海区(巴伦支海、楚科奇海及白令海)浮游植物藻华动态的变化规律。通过计算能表征光照和营养盐限制的多个指标,分析表层叶绿素a浓度模拟结果的误差来源。结果表明,依据冰下光照时长、混合层变化速率、表层硝酸盐指标将11种模式分为3组,与参考值指标差异较小组别中的模式在藻华模拟方面明显占优,而其余模式在表层硝酸盐或混合层变化的模拟上存在较大误差,导致表层叶绿素a浓度峰值的发生时间延后且峰值浓度误差大。总体而言,地球系统模式配置中除要考虑光照和营养盐这两种基础限制条件外,也需关注由温盐控制的上混合层深度,从而准确模拟出表层叶绿素a浓度的季节性变化规律,上述研究为地球系统模式中相关参数化方案的改进提供了参考。

Seasonal variability of the mixed layer depth determined using an improved maximum angle method in the Arctic basins

To investigate the spatiotemporal variations in the mixed layer depth(MLD)in the Arctic basins,a new criterion to determine the MLD,called the improved maximum angle method(IMAM),was developed.A total of 45123 potential density profiles collected using Ice-Tethered Profilers(ITPs)in the Arctic basins during 2005-2021 were used to demonstrate the method’s effectiveness.By comparing the results obtained by the fixed threshold method(FTM),percentage threshold method(PTM),and maximum gradient method(MGM)for profiles in the Canada Basin,Makarov Basin,and Eurasian Basin,we determined that the quality index(1.0 for perfect identification of the MLD)of the IMAM regarding the assessment of the MLD determination method reached 0.94,which is much greater than those of other criteria.Moreover,two types of the density profiles were identified based on the mixed layer development stage.The MLDs of the typical profiles determined using the IMAM were found to have better consistency with the original definition.By utilizing the new mixed layer criterion,the seasonal variations and regional differences in the MLD in the Arctic basins were analyzed.Spatially,the summer and winter MLDs in the Canada Basin were the shallowest(13.55 m in summer,26.76 m in winter)than those in the Makarov(29.51 m in summer,49.08 m in winter)and Eurasian(20.36 m in summer,46.81 m in winter)basins due to the stable stratification in the upper ocean and the subsequent small effects of dynamic and thermodynamic processes(wind-driven stirring and brine rejection)in the Canada Basin.Seasonally,in the three Arctic basins,the average MLD was shallowest(22.77 m)in summer;it deepened through autumn and reached a winter maximum(41.12 m).

北极快速变化的生态环境响应

北冰洋由于其特殊的地理位置,成为全球变化响应最为敏感的地区。本文聚焦北极海冰变化幅度最大的西北冰洋,从营养盐、叶绿素、浮游植物群落和沉积碳埋藏等变化来讨论海洋生态环境对北极快速变化的响应。尽管太平洋北向流和北极周边河流输入加强可以增加西北冰洋上层营养盐储库,但由于夏季硅藻旺发向沉积物迁出大量生源元素,使得上层营养盐相对亏损,部分海域存在显著的氮限制和硅限制。随海冰减退,尽管夏末海盆区浮游植物呈现小型化趋势,但西北冰洋总体上浮游植物现存量和初级生产力呈现增高的趋势;伴随叶绿素极大层下移、北扩,以硅藻为代表的生物泵过程得以更高效的运转。在沉积物埋藏的有机碳中,除原先北冰洋生态系统占据重要比份的冰藻外,硅藻等藻类的有机碳埋藏也逐渐增加。西北冰洋海洋初级生产力的增加不仅促进了生物泵的运转和碳的埋藏,而且给海洋生态系统提供了更多的食物来源。北极海域目前已成为全球碳源汇格局变化最大、海洋生态系统改变最显著的地区之一。

基于CiteSpace的北极研究综述

以北极研究为中心,基于CNKI和Web of Sciences Core Collection数据库2000—2017数据,采用CiteSpace,系统展示了中国和国际(含中国)在北极科研领域的发展趋势、前沿、热点和机构合作特征。研究表明,国内的北极研究经历了由气候海冰—航运—北极治理的研究过程,发文量以北极航运为主导。国际针对北极的研究经历了三个逐步加速阶段:1990、2000和2005,北极八国和德、英、法是北极研究的主力军。北极科技合作仍主要以国家内部合作为主,但科研机构合作频率高度爆发且出现一批以“Helmholtz Centrefor Polar and Marine Research(德国)、The Arctic University of Norway(挪威)、Aarhus University(丹麦)和KoreaPolar Research Institute(韩国)”为代表的北极研究合作爆发单位;北极研究领域多样,呈现出以“arcticocean”、“climate”、“arctic temperature”、“variability”、“sea ice”、“model”等为重点的关键词,表明近年国际北极研究主要热点在气候变化、海冰、洋流等领域,这些领域相互交叉。通过对国内外北极通航经济性的系统综述分析得出:国内外学者均认为与北极海冰有关因素是制约北极通航的关键;国内学者对北极通航的经济效益较为乐观,而国外学者则较为辨证且谨慎。这与研究所考虑的角度有关,国内学者较多考虑北极通航的技术管理、人力资源、能耗、时间和政治等因素,而国外学者在这些因素的基础上,还侧重于贸易需求、通航意愿性和通航对气候的影响等因素。