1972-2013年北欧海深层水增暖

The warming of deep waters in the Nordic seas is identified based on observations during Chinese 5th Arctic Expedition in 2012 and historical hydrographic data. The most obvious and earliest warming occurrs in the Greenland Basin(GB) and shows a coincident accelerated trend between depths 2 000 and 3 500 m. The observations at a depth of 3 000 m in the GB reveal that the potential temperature had increased from-1.30°C in the early 1970 s to-0.93°C in 2013, with an increase of about 0.37°C(the maximum spatial deviation is 0.06°C) in the past more than 40 years. This remarkable change results in that deep waters in the center of the Lofton Basin(LB) has been colder than that in the GB since the year 2007. As for the Norwegian Basin(NB), only a slight trend of warming have been shown at a depth around 2 000 m since the early 1980 s, and the warming amplitude at deeper waters is just slightly above the maximum spatial deviation, implying no obvious trend of warming near the bottom. The water exchange rate of the Greenland Basin is estimated to be 86% for the period from 1982 to 2013, meaning that the residence time of the Greenland Sea deep water(GSDW) is about 35 years. As the weakening of deep-reaching convection is going on, the abyssal Nordic seas are playing a role of heat reservoir in the subarctic region and this may cause a positive feedback on the deep-sea warming in both the Arctic Ocean and the Nordic seas.     

The Beaufort Gyre variation and its impacts on the Canada Basin in 2003–2012

The Beaufort Gyre (BG) was spun up in the last decade which is an important factor in regulating the variation of the upper ocean. The heat content and freshwater content of the upper ocean increased g...     

2012年夏季挪威海和格陵兰海水文特征分析

利用2012年夏季在北欧海(挪威海和格陵兰海)的水文考察数据,对调查区域内海洋水团性质和分布进行了分析,并对北欧海冷却对流的发展加深过程进行了研究。在上层,从东侧暖而咸的大西洋水跨越锋区至西侧低温低盐的格陵兰海盆上层水体,温度和盐度的变化分别可以达到8℃和0.4 psu。中层与深层水体的性质则相对均匀和稳定,3个海盆内从浅至深依次分布着北极中层水、海盆深层水、北极深层水以及海盆底层水。格陵兰海盆中深层水体在3 500 m深度上位温约为-0.97℃,相比较1970s观测到的-1.30℃,升温幅度超过了0.3℃,表明海盆深层存储的热量显著增加。在只考虑局地表面冷却的简化条件下,当前格陵兰海内部通过冷却对流混合至季节性跃层下界需要向大气释放0.9×109~1.2×109J的热量,这一过程至少需要2个月的时间而不利于对流向深层的发展。大量的热量被存储于北欧海深海盆中使得北欧海已经成为北半球高纬海域的热量存储器,对当前北极气候变化的影响有待深入研究。     

白令海楚科奇海的海冰范围变化特征

白令海和楚科奇海位于北极太平洋一侧的海冰外缘线附近,具有较强烈的气冰海相互作用.采用滑动t检验和小波分析方法对白令海和楚科奇海1953—2004年海冰范围的年际变化、年代际变化和总体趋势变化进行分析.结果表明:20世纪70年代后期,海冰范围在白令海存在显著的均值突变现象,而楚科奇海在对应阶段则表现为更明显的变频现象;在突变点前后两个时段里,阿留申低压中心低压加强、核心位置偏移以及对应风场分布的变化是导致白令海海冰范围明显缩小的主要动力原因.楚科奇海海冰范围的年际变化中存在由低频向高频变化的现象,该现象除了在局地气温变化中存在之外,在北冰洋区域风涡度、波弗特海纬向风、东西伯利亚海经向风等动力因素中也有所体现.因此,除热力因素外,动力因素引起的海冰的平流与该变频现象也存在一定的联系.     

火山活动对南半球平流层气候异常变化的影响

文中利用逐次滤波法分析结果表明 ,火山活动能引起平流层较大幅度增温 ,对于南半球 70hPa高空气候异常变化的影响超过了总方差的 1 6 % ;火山活动影响最显著的高度是平流层 70hPa约1 5～ 2 2km高空 ,由此高度向上或向下 ,火山活动的影响都逐渐减小 ;火山活动引起平流层大气升温的同时还将引起对流层大气降温 ,其分界线大致位于对流层顶 30 0hPa附近。平流层高空气候异常变化还具有显著的 2 2a变化周期和 1 1a变化周期 ,分析认为是大气温度场对太阳磁场磁性 2 2a周期和太阳黑子 1 1a周期变化的响应 ,其方差贡献率超过 8%。     

Radiation of lamp and optimized experiment using artificial light in the Arctic Ocean

A winter optical experiment by an artificial lamp was conducted in the Amundsen Bay of Arctic Ocean from November of 2007 to January of 2008.The radiation field emitted from an artificial lamp was measured and is introduced in this paper ,and the optimized experiment project is discussed.It is demonstrated that the minimum size allowed of the lamp is determined by both the field of view(FOV) of optical instrument and the measuring distance from the lamp.Some problems that might influence on the experiment result often occur for a simple fluorescent lamp, such as instability,spatial nonuniformity,light divergence,effect of lamp temperature ,etc.By the analysis of the light radiation,three kind of measures are proposed to control the quality of the experiment,i.e.keeping consistency of lamp size with FOV of instrument,calibrating in situ downwind,and conducting measurement in effective range.Among them,the downwind calibration is the key step to overcome most problems arose by the lamp.The experiment indicated that the reliable results can be obtained only when the optical measurement is coordinated with the radiation field of artificial lamp.The measured radiation property of the lamp was used to advise the field experiment to minimize measuring error.As the experiment by artificial lamp was the first attempt in the Arctic Ocean,the experience given by this paper is a valuable reference to the correlative studies.     

北极迅速变暖条件下西北航道的海冰分布变化特征

北极近年迅速变暖使西北航道的通航成为可能。本文利用AMSR-E的6.25km分辨率日平均海冰密集度卫星数据研究了2002-2008年北极西北航道的海冰密集度变化特征。通过统计分析沿西北航线冰障关键流段代表站点的融化期、轻冰期、无冰期、无冰天数和轻冰天数,以及海冰分布和变化的某些细节,加深了对西北航道海冰季节变化和年际变化以及空间分布的主要特征,特别是与通航相关的冰情信息的了解。研究指出西北航道南路比北路容易开通;各线路冰障流段存在的时间呈减小趋势,整条线路无冰/轻冰天数呈增加趋势;冰间湖和冰间水道的产生和发展在很大程度上可能会影响到整个航路的融冰开始时间。     

北欧海海面高度上升减缓及其机理研究

A slowdown of sea surface height(SSH) rise occurred in the Nordic(GIN) seas around 2004.In this study,SSH satellite data and constructed steric height data for the decades before and after 2004(i.e.,May 1994 to April 2014)were used for comparative analysis.The findings indicate that the rate of slowdown of SSH rises in the GIN seas(3.0 mm/a) far exceeded that of the global mean(0.6 mm/a).In particular,the mean steric height of the GIN seas increased at a rate of 4.5 mm/a and then decreased at a slower pace.This was the main factor responsible for the stagnation of the SSH rises,while the mass factor only increased slightly.The Norwegian Sea particularly experienced the most prominent slowdown in SSH rises,mainly due to decreased warming of the 0–600 m layer.The controlling factors of this decreased warming were cessation in the increase of volume of the Atlantic inflow and stagnation of warming of the inflow.However,variations in air-sea thermal flux were not a major factor.In the recent two decades,mean halosteric components of the GIN seas decreased steadily and remained at a rate of 2 mm/a or more because of increased flow and salinity of the Atlantic inflow during the first decade,and reduction in freshwater inputs from the Arctic Ocean in the second decade.     

2003年与1999年楚科奇海海冰的差异及其发生原因

我国在1999年和2003年进行了两次北极考察,这两年海冰的冰情差别很大,分别对应冰情较重和较轻的年份。本文利用卫星遥感资料对1999年和2003年的海冰分布状况及其差异进行了全面的分析,并利用气温和风场资料深入研究形成这种差异的动力学原因。结果表明, 2003年的海冰冰情与1999年相比要轻很多,海冰面积在春季融冰季节和秋季冻结季节显著减小。2003年春季,来自白令海的海水提早半个月进入楚科奇海,导致海冰大范围融化。但是,到了夏季,海冰的面积减少过程停滞下来。而秋季楚科奇海封冻过程比1999年晚半个月。以上这些特征形成了2003年与1999年海冰的显著差异。研究结果表明, 2003年春季和秋季的气温比1999年要明显增高,最大月平均温差接近18°C,显著的高温为海冰融化的加剧和冻结的推迟提供了热量。直接影响海冰分布的是海面风场,两年风场的差异产生了来自白令海的太平洋入流的差异,对春季海冰融化的提前、夏季入流的减弱和秋季冻结过程的推迟起到关键的作用。季节性气象要素的年际差异可以归因于整个北极的AO系统变化, 2003年AO指数是正值, 1999年为负值,成为楚科奇海局地海冰变化的气候背景。