秋季北极海冰与欧亚冬季气温在年代际和年际尺度上的不同联系

北极海冰的急剧消融在近年来欧亚大陆频发的低温事件中扮演着关键角色.秋季北极海冰的偏少对应着冬季欧亚大陆的低温天气,然而二者的联系在年代际和年际两种时间尺度上存在显著区别.本文运用1979—2012年哈德莱中心第一套海冰覆盖率(HadISST1)、欧洲中心(ERA_Interim)的2m温度、风场、海平面气压场、高度场等资料,分别研究了年代际和年际时间尺度上前期秋季北极海冰与欧亚冬季气温的联系.结果表明,欧亚和北极地区(0°—160°E,15°N—90°N)的冬季气温具有显著的年代际和年际变化.在年代际尺度上,温度异常分布在21世纪初由北极冷-大陆暖转为北极暖-大陆冷.这一年代际转折与前期秋季整个北极地区的海冰年代际减少联系密切.秋季北极全区海冰年代际偏少对应冬季欧亚大陆中高纬地区的高压异常,有利于北大西洋的暖湿气流北上和北极的冷空气南侵,造成北极暖-大陆冷的温度分布;在年际时间尺度上,温度异常分布主要由第一模态的年际变化部分和第二模态组成,且第一模态包含的年际变率信号也存在显著的年代际变化.年际尺度上全区北极海冰对欧亚冬季气温的影响远不及位于北冰洋西南边缘的巴伦支海、喀拉海和拉普捷夫海西部(30°E—120°E,75°N—85°N)的关键区海冰影响显著.关键区内海冰的偏少会引发冬季的北大西洋涛动负位相,导致北大西洋吹往欧亚大陆的暖湿气流减弱和欧亚大陆中高纬地区的气温偏低.     

2012-2013年中国西南地区秋、冬、春季持续干旱的成因

利用多种资料从大尺度大气环流、水汽输送、热带海表温度、北极涛动、平流层极涡等方面分析了2012-2013年中国西南地区秋、冬、春季持续干旱的成因。结果表明, 西南水汽输送偏弱、高纬度地区南下冷空气路径偏东、冷暖空气难以在西南地区上空交汇, 是此次持续干旱的直接原因。这段时间西南地区大都受平直西风气流控制, 孟加拉湾和中南半岛地区位势高度较常年偏高, 不利于这些地区气旋性环流的发展;热带海表温度异常变化,特别是冬春季印度洋海表温度的持续偏高, 使得菲律宾地区上空低层反气旋异常环流增强。这些都导致了西南向水汽输送偏弱。此外, 北极涛动异常变化对西南地区的干旱也有重要影响, 北极涛动持续处于负位相, 不仅使南支槽减弱变浅, 西南水汽输送减少, 还导致贝加尔湖高压脊偏弱, 使北方南下冷空气主体偏东。冬季平流层极涡强度的变化在各个高度的位势高度场和位势涡度场上都有体现, 其变化对冷空气的强度及路径有明显影响。     

当今北极地缘政治格局特征分析

冷战结束后,北极地区逐渐发展为世界政治的一个热点,北极地缘政治局势处在快速的变化发展之中。地缘政治格局是控制地缘政治形势发展的一个结构因素,分析地缘政治格局有助于我们认识和理解复杂的、变动的地缘政治现实关系。本文在地缘政治格局概念基础上,提出了地缘政治格局的基本分析方法,并以此分析了冷战后北极地区的地缘政治格局的主要特征。     

SIS海冰模式中两种盐度参数化方案的差异

详细介绍了Sea Ice Simulator(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,将该项定义为盐度差异项。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对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,因此盐度差异项对与海冰增长和消融影响很小。同时利用GFDL中心研制的冰-洋耦合模式Modular Ocean Model(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。     

Winter climate change at different temporal scales in Vaccinium myrtillus, an Arctic and alpine dwarf shrub

Snow cover strongly influences plant growth in Arctic and alpine ecosystems. Snow characteristics and snowmelt timing are likely to change in a warmer climate. We studied year rings and shoot growth of the dwarf shrub bilberry ( Vaccinium myrtillus ), and species abundances of the vegetation, in response to early or late snowmelt at a study site in the Central Alps, near Davos, Switzerland. Snowmelt was manipulated on experimental plots for 3 and 30 years. Additional plots were set up along a natural snowmelt gradient, and at high and low elevation. Growth ring data showed an increasing trend in annual growth increment over the last 20 years, especially in the extraordinarily hot summer of 2003. Comparing high and low elevation sites, growth rings were wider at low elevation, but only in cold years. In years with relatively cold summers, however, xylem ring width was greater in plots with late rather than early snowmelt along the natural snowmelt gradient, possibly indicating drought stress in early snowmelt plots. Snow cover had a strong influence on species abundances along the natural snowmelt gradient, and change (not yet significant) was beginning to be seen in plots with 30 years of snow manipulation. Our results indicate that beneficial effects of early snowmelt for shrub growth may be offset in cold summers. Although early snowmelt prolongs the growing season, harsh conditions and frost events early in the growing season may become more likely, and hamper plant growth, and this could affect plant growth in all Arctic and alpine snow-dominated ecosystems.     

北极楚克奇海上空臭氧垂直变化的探测与分析

1999年夏季,中国首次组织北极地区科学考察.分析此次考察中楚克奇海海域上空获得的大气结构和臭氧探空资料,结合臭氧总量观测光谱仪(TOMS)臭氧总量和NCEP大气环流资料,指出:考察期间楚克奇海海域上空臭氧总量与13 km以下臭氧含量关系密切,而在20 km附近最大臭氧浓度处的臭氧变化与大气臭氧总量关系较差,表明整层臭氧总量的变化主要受低层大气臭氧变化的影响.大气臭氧总量呈高-低-高变化,对流层顶高度呈低-高-低变化,分析500hPa高度场表明:考察期间的天气系统可能是造成局地臭氧变化的主要原因.     

A Technique for Estimating Polar Ozone Loss: Results for the Northern 1991/92 Winter Using EASOE Data

In this paper we describe a technique for estimating chemical ozone loss in the Arctic vortex. Observed ozone and temperature profiles are combined with the model potential vorticity field to produce time series of vortex averaged ozone mixing ratios on chosen isentropic surfaces. Model-derived radiative heating rates and observed vertical gradients of ozone are then used to estimate the change in ozone that would occur due to diabatic descent. Discrepancies with the observed ozone are interpreted as being of chemical origin, assuming that there is negligible horizontal transport or mixing of air into the vortex. The technique is illustrated using ozone sonde measurements collected during the 1991/92 European Arctic Stratospheric Ozone Experiment (EASOE), meteorological analyses from the European Centre for Medium-range Weather Forecasts (ECMWF) and radiative heating rates extracted from the Global Atmospheric Modelling Programme (UGAMP) 3D General Circulation Model. Our results show that there was photochemical ozone destruction inside the Arctic vortex in early 1992 with a loss between 475 K and 550 K (around 20 km) of 0.32±0.15 ppmv in the first 20 days of January, equivalent to a rate of 0.51±0.24%/day (at the 95% confidence level).     

Polycyclic Aromatic Hydrocarbons in the Arctic: Ob and Yenisei Estuaries and Kara Sea Shelf

Suspended matter (SM) and surface sediments were analysed for polycyclic aromatic hydrocarbons (PAH) throughout the Ob and Yenisei River estuaries and in the Kara Sea in order to evaluate the contamination of Arctic shelves by these two major Siberian rivers. PAH concentrations were extremely low, among the lowest measured up to now in the Arctic region. Particle-associated PAH were in many cases non-detectable. A total PAH maximum value of 3·2ngl ^{− 1}was found in surface waters. In surficial sediments, they spanned a range from 24 to 115ngg ^{− 2}in the Ob River, from 40 to 131ngg ^{− 2}in the Yenisei and from 16 to 94ngg ^{− 2}in the Kara Sea. Compositional features revealed a contribution of detrital material eroded from soils of the drainage basins and inputs from airborne pyrolytic PAH emitted at lower latitudes and from industrial complexes in Siberia. Particulate and sedimentary PAH distributions were highly variable both in type and concentration. The Ob and Yenisei estuaries are geographically large features where hydro-dynamical and sedimentary processes are complex. As a consequence, inhomogeneities—in the form of patch-structures—develop and make it difficult to resolve the fate of riverborne constituents based on ship measurements only. Remote sensing in conjunction with oceanographic observations may provide further guidance to study large river systems.     

基于ScienceDirect数据库的国外北极问题研究综述（2007—2021年）

随着北极海冰融化的加剧,北极问题研究的重要性逐渐凸显。文章以ScienceDirect数据库为主要搜索范围,系统梳理了2007—2021年国外北极问题研究文献,从北极航线、北极经济、北极政治和北极环境4个方面对国外北极问题研究现状进行了分析。认为未来的国外北极问题研究中,北极航线相关问题研究将聚焦于北极航线运营模式的研究;北极经济问题研究将注重区域经济和北极产业发展;北极政治研究依然会着力探讨如何在北极治理中的合作问题,虽然目前的北极政治研究中定性分析和描述性分析较多,但未来将增加定量分析和理论创新的研究;北极环境问题研究将注重北极经济开发和环境保护的平衡,进一步关注北极的可持续发展问题。