北冰洋次表层暖水形成机制的研究

分析了北冰洋加拿大海盆上层海水温度结构特征,针对在海冰覆盖区域普遍发生的次表层暖水现象,建立了冰海耦合的一维柱形模式,成功模拟了次表层暖水的垂向结构和形成机制,证明了太阳辐射加热和表层冷却是次表层暖水的成因。通过数值实验定量分析了形成次表层暖水各因子的作用,表明太阳辐射是形成次表层暖水的能量来源;长波辐射、气温和比湿等其他大气因子对次表层暖水强度有较大影响;在厚冰区不能形成次表层暖水,海冰越薄,水道面积越大,则冰下次表层海水温度升高得就越快,薄冰和冰间水道是形成次表层暖水的主要能量通道;通过模式的拟合给出湍扩散系数垂向变化的估值,冰下表层海水垂向湍扩散系数为5.0×10-3m2/s左右,而次表层垂向湍扩散系数却快速降低到1.0×10-6m2/s,表明跃层导致的稳定性增大是形成次表层暖水尖峰的关键因素。     

夏季北冰洋海冰边缘区海水温盐结构及其形成机理

利用1999年北极科学考察期间在海冰边缘区的三次考察数据，研究了北冰洋海冰边缘区的温度和盐度结构。将海冰边缘区分为机制不同的两大类，一类是暖水海冰边缘区，主要热源是外部暖水进入海冰边缘区携带的热量；另一类是冷水海冰边缘区，主要热源是太阳辐射加热。文中主要对冷水海冰边缘区进行了研究。虽然两个冷水海冰边缘区(R区与T区)温度结构不尽相同，但都存在表层以下水体中的温度极大值现象，R区的温度极大值位于20m左右，T区的位于40—50m左右的深度，可以认为是海冰边缘区的典型温度特征。作者认为，次表层暖水的热源是太阳辐射的直接加热，为此，建立了太阳加热引起海水次表层增暖的物理模型和简单的数学模型，获得了冰下海水在太阳辐射的作用下增暖的解析解。结果表明，部分太阳辐射能穿过海冰加热冰下海水，加热之初温度的极大值出现在近表层，随着时间的推移，海温极大值的位置向下移动，最终可以达到40m左右，证明了仅仅依靠太阳的短波辐射就可以形成中间暖的水层。文中阐明，开阔海水更多的是上混合层和跃层结构，冰下海水主要是次表层暖水结构；冷水海冰边缘区的海水主要带有冰下海水的特征。由于次表层暖水的形成与海冰厚度关系很大，近十几年北冰洋海冰厚度的显著减少势必加强次表层暖水，可能是北冰洋增暖的又一个重要现象，对全球气候变化有意义深远的影响。     

2008年加拿大海盆次表层暖水的精细结构的研究

自2004年以来,在加拿大海盆频繁发生的次表层暖水(near surface temperature maximum,NSTM)现象是北极快速变化响应的事实之一.采用2008年中国第3次北极科学考察的CTD数据和西北冰洋联合研究计划与美国波弗特环流观测系统计划2008年航次的CTD数据以及冰浮标ITP18数据,对加拿大...     

西风爆发、次表层暖水东移与厄尔尼诺现象

利用最近20 a的大气海洋资料,分析了厄尔尼诺事件与赤道太平洋西风异常以及赤道太平洋次表层海温之间的关系.结果表明,赤道西太平洋(5°S～5°N,120°～160°E)和赤道中东太平洋(5°S～5°N,160°E～160°W)西风异常都存在着与厄尔尼诺周期一致的年际变化,但前者还包含有显著的2～3个月季节内振荡.赤道西太平洋次表层冷暖水东移也呈现年和年际时间尺度的振荡周期.在厄尔尼诺发生前,赤道西太平洋次表层海水出现持续性增暖,赤道西太平洋西风异常频率加快,强度增强.随后赤道中太平洋(160°E～160°W)出现持续性(3个月以上)强西风异常(即西风爆发),并进一步向东扩展,同时次表层暖水沿着赤道波导东移到赤道东太平洋混合层,导致赤道东太平洋海表大面积异常增暖,形成一次厄尔尼诺现象.最后,模式模拟了1980～1984年赤道太平洋海温的变化,进一步证实了赤道纬向西风异常对暖水东移起着重要的作用.     

西太平洋暖池表层暖水的纬向运移

基于1950～2000年太平洋月平均SST资料,运用Morlet小波分析等方法研究了西太平洋暖池表层暖水的纬向运移特征.结果表明:暖池表层暖水纬向运移的年际(2～8a)和年代际(10～16a)变化都非常明显;表层暖水的纬向运移于1982年前后经历了一次气候跃变,跃变后暖水东界的平均位置比跃变前东移了10个经度;表层暖水的纬向运移对ENSO暖(ElNiño)、冷(LaNiña)事件的形成和发展具有直接的作用.     

萨马岛以东海域的一个次表层暖涡

通过对1988年和1989年由中国科学院海洋研究所“科学一号”船在菲律宾以东海域获得的CTD调查资料的分析,发现在萨马(Samar)岛以东海域200m层下存在着一个东西跨度约为3个经度、南北跨度约为3个纬度的次表层暖涡,本文简称为Samar暖涡。这个暖流的强度、位置及其所潜在的深度范围均有明显的年际变化。这些变化与棉兰老潜流的变化是一致的。当棉兰老潜流强时,Samar暖涡也强;反之它也弱。由此可以看出,棉兰老潜流和Samar暖涡两者之间存在着密切的关系。     

2003年夏季西北冰洋浮游动物群落结构和地理分布研究

根据西北冰洋43个调查站位的浮游动物种类组成和数量资料,分析了浮游动物的群落结构和地理分布特征,探讨了浮游动物群落与环境因子的关系.结果表明,在调查区域存在三种不同的浮游动物群落类型:楚科奇海台和加拿大海盆地区的高纬度深海群落;楚科奇海中部的陆架群落;阿拉斯加沿岸和楚科奇海北部的沿岸过渡群落.深海群落浮游动物数量较少,...     

夏季北极密集冰区范围确定及其时空变化研究

研究夏季北极密集冰区的范围变化是了解北极海冰融化过程的重要手段。密集冰区与海冰边缘区之间没有明确的分界线, 海冰密集度在两者之间平滑过渡, 确定密集冰区范围就需确定一个密集度阈值。文中依据分辨率为6.25 km的AMSR-E遥感数据, 发现不同密集度阈值所围范围在密集冰区边缘处的减小存在由快变慢的过程, 同时与周围格点的密集度差异变化在该处最为显著, 对这两个特征进行统计分析, 获得的阈值同为89%, 具有明确的物理意义和合理性。以此为基础, 运用腐蚀算法剔除海冰边缘区, 同时结合连通域法排除小范围密集冰的影响, 进而确定密集冰区的范围。结果表明, 2002-2006年密集冰区覆盖范围较大, 年际变化较小, 2007年以后明显减小, 2010年与2011年相继出现最小值, 其中2011年的范围最小值仅为2006年的64%。密集冰区范围的变化不同于海冰覆盖范围, 是具有独立特性的海冰变化参数, 反映出高密集度海冰区域的变化特征。海冰的融化与海冰边缘区的变化是导致密集冰区范围发生变化的两个主要因素, 受动力学因素的影响, 海冰边缘区发生伸展或收缩, 发生密集冰区与海冰边缘区互相转化。本文提出了一种研究北极海冰变化的新思路, 密集冰区覆盖范围的减小表明北极中央区域高密集度海冰正持续减少。     

2008年夏季西北冰洋观测区叶绿素a和初级生产力粒级结构

对2008年夏季在西北冰洋172°～143.6°W的楚科奇海及其北部海区对粒度分级叶绿素a和初级生产力现场观测资料,对观测区的空间分布特征进行了研究.结果表明,观测海区表层叶绿素a浓度为0.013～19.367 μg/dm3,平均值为0.677士2.2661 μg/dm3,次表层水叶绿素a浓度高于其它水层.水柱叶绿素a...     

西北冰洋表层沉积物中重金属的赋存形态研究

用连续提取法对选自西北冰洋的32个表层沉积物进行分析,测定了Cr、Cu、Pb在全样中及其在P1-2、P3、P4、P5中的含量.结果表明随着离岸距离增加,水深加深,Cr、Cu、Pb含量呈增高的趋势.研究区陆架沉积物中Cr、Cu、Pb含量分别为60.66、14.77、16.65μg/g;深海沉积物中Cr、Cu、Pb的含量分别为80.40、41.70、25.62μg/g.元素赋存形态分析表明,Cr、Cu、Pb主要赋存在残渣态,残渣态中三元素的含量平均值分别为64.97、19.67、17.56μg/g,占元素总量的比例分别为93.58%、75.02%和83.76%.三元素在各赋存形态中的含量分布是:Cu为残渣态>有机质和硫化物态>铁锰氧化态>可交换及碳酸盐态;Pb和Cr则为残渣态>铁锰氧化物态>有机质硫化物态>可交换态及碳酸盐态.研究区重金属元素在不同赋存形态中的含量分布与北太平洋深海沉积物中类似.     

海水物质平衡浮标对北冰洋中心区海冰温度与物质平衡的观测

利用中国第3次北极科学考察所布放海冰物质平衡浮标(Ice Mass-Balance buoy,IMB)的观测数据,分析了北冰洋中心区多年冰2008年8月-2009年7月温度与物质平衡的变化特征.结果表明,冰温廓线呈现明显的季节变化,秋季降温过程从海冰表面开始向冰体内部传播.海冰底部的生长/消融率受海水温度控制,随水温的...     

基于中国北极考察布放浮标观测和数值模拟的海冰和积雪厚度变化分析

Sea ice and the snow pack on top of it were investigated using Chinese National Arctic Research Expedition(CHINARE) buoy data.Two polar hydrometeorological drifters,known as Zeno? ice stations,were deployed during CHINARE 2003.A new type of high-resolution Snow and Ice Mass Balance Arrays,known as SIMBA buoys,were deployed during CHINARE 2014.Data from those buoys were applied to investigate the thickness of sea ice and snow in the CHINARE domain.A simple approach was applied to estimate the average snow thickness on the basis of Zeno~ temperature data.Snow and ice thicknesses were also derived from vertical temperature profile data based on the SIMBA buoys.A one-dimensional snow and ice thermodynamic model(HIGHTSI) was applied to calculate the snow and ice thickness along the buoy drift trajectories.The model forcing was based on forecasts and analyses of the European Centre for Medium-Range Weather Forecasts(ECMWF).The Zeno~ buoys drifted in a confined area during 2003–2004.The snow thickness modelled applying HIGHTSI was consistent with results based on Zeno~ buoy data.The SIMBA buoys drifted from 81.1°N,157.4°W to 73.5°N,134.9°W in 15 months during2014–2015.The total ice thickness increased from an initial August 2014 value of 1.97 m to a maximum value of2.45 m before the onset of snow melt in May 2015;the last observation was approximately 1 m in late November2015.The ice thickness based on HIGHTSI agreed with SIMBA measurements,in particular when the seasonal variation of oceanic heat flux was taken into account,but the modelled snow thickness differed from the observed one.Sea ice thickness derived from SIMBA data was reasonably good in cold conditions,but challenges remain in both snow and ice thickness in summer.     

融冰季节北极破碎冰区热通量的初步研究

利用航空遥感数字影像的解析结果和实测气象，海洋和海冰资料，定量研究了夏季融冰期北极破碎冰区的热通量，计算了海洋对大气的热贡献，结果表明，在北极夏季海冰融化时，短波辐射远远大于感热和潜热通量，是表面热通量的决定因素，海洋对大气的热贡献主要由长波辐射决定，在观测期间，海洋对大气的热贡献为38～104Wm^-2，这部分热量的大小与海冰的密集度有关，当海冰密集度小于0.8时，海洋对大气的热贡献随海冰密度度的增大而减小，而当海冰密集度超过0.8以后，该热通量将随海冰密集度的增大而增大。     

A double-halocline structure in the Canada Basin of the Arctic Ocean

1IntroductionAs a particular hydrographic feature,the upperArctic Ocean is salinity-stratified.A year-round halo-cline exists between the fresher,colder mixed Layerand the saltier,warmer middle layer(the Atlantic Lay-er),which is important to the permanent sea ice coverin the Arctic Ocean for it insulates the ice pack fromthe heat in the Atlantic Layer throughout the Arctic O-cean(Maykut and Untersteiner,1971).Characterizedby its vertically uniform temperature near freezingpoint,the haloc…     

On the future navigability of Arctic sea routes: High-resolution projections of the Arctic Ocean and sea ice

The rapid Arctic summer sea ice reduction in the last decade has lead to debates in the maritime industries on the possibility of an increase in cargo transportation in the region. Average sailing times on the North Sea Route along the Siberian Coast have fallen from 20 days in the 1990s to 11 days in 2012–2013, attributed to easing sea ice conditions along the Siberian coast. However, the economic risk of exploiting the Arctic shipping routes is substantial. Here a detailed high-resolution projection of ocean and sea ice to the end of the 21st century forced with the RCP8.5 IPCC emission scenario is used to examine navigability of the Arctic sea routes. In summer, opening of large areas of the Arctic Ocean previously covered by pack ice to the wind and surface waves leads to Arctic pack ice cover evolving into the Marginal Ice Zone. The emerging state of the Arctic Ocean features more fragmented thinner sea ice, stronger winds, ocean currents and waves. By the mid 21st century, summer season sailing times along the route via the North Pole are estimated to be 13–17 days, which could make this route as fast as the North Sea Route.     

Chlorophyll a Biomass of Netplankton in Surface Waters in the Pacific Sector of the Southern Ocean in Austral Summer

Chlorophyll a of total and particles retained on 30 μm mesh plankton net were both determined in surface waters along two cruise tracks ranging from the Subtropical water to the marginal ice zone in the Pacific sector of the Southern Ocean in austral summer. Total surface chlorophyll a in the study area was mostly less than 1 μg chl a 1⁻¹, and showed distributions with no obvious trend associated with different waters masses of the Antarctic and the Subantarctic, although total chlorophyll a concentrations changed greatly within each water mass. Particularly low concentrations of chlorophyll a were detected in the marginal ice zone. Chlorophyll a contained in 30 μm netplankton made up 5∼60% of total chlorophyll a: large near the marginal ice zone and becoming small with travel towards the north. High percentage shares of netplankton chlorophyll a were confirmed even in low total chlorophyll a concentrations in summer in the Southern Ocean. A positive relation was observed between the percentage of 30 μm netplankton and the “average total chlorophyll a”, although there was great scatter. This revised version was published online in August 2006 with corrections to the Cover Date.     

北极河流径流对北冰洋环流的影响

北极河流径流是北冰洋淡水的最大来源,其变化会对北冰洋中的诸多过程有重要影响。本文基于全球高分辨率海洋-海冰耦合模式的模拟结果,研究北冰洋温盐、海冰以及环流对北极河流径流的敏感性。通过对比有气候态北极河流径流输入的控制实验结果和径流完全关闭的敏感性实验结果,研究发现北极径流对北冰洋温度、盐度、海冰以及海洋环流等有显著的影响。关闭北极河流径流后,在河口附近的陆架上温度降低、盐度升高,且导致500 m深度处温度下降以及盐度升高;河口附近的陆架处,海冰密集度与海冰厚度增加。关闭北极河流径流也对北冰洋内的环流有影响:由于缺少来自欧亚大陆的北极径流的输入,穿极漂流与东格陵兰流流速减小且盐度增加;关闭北极径流导致近岸海表面高度降低,沿欧亚陆架的北冰洋边界流减弱,白令海入流增强。通过对比关闭北极径流实验与控制实验的温度和盐度剖面,发现关闭北极径流后大西洋层温度降低,各陆架海盐跃层的梯度减小,盐跃层厚度减小。     

Variation of diffuse attenuation coefficient of downwelling irradiance in the Arctic Ocean

The diffuse attenuation coefficient(Kd) for downwelling irradiance is calculated from solar irradiance data measured in the Arctic Ocean during 3rd and 4th Chinese National Arctic Research Expedition(CHINARE), including 18 stations and nine stations selected for irradiance profiles in sea water respectively. In this study, the variation of attenuation coefficient in the Arctic Ocean was studied, and the following results were obtained. First, the relationship between attenuation coefficient and chlorophyll concentration in the Arctic Ocean has the form of a power function. The best fit is at 443 nm, and its determination coefficient is more than 0.7. With increasing wavelength, the determination coefficient decreases abruptly. At 550 nm, it even reaches a value lower than 0.2. However, the exponent fitted is only half of that adapted in low-latitude ocean because of the lower chlorophyll-specific absorption in the Arctic Ocean. The upshot was that, in the case of the same chlorophyll concentration, the attenuation caused by phytoplankton chlorophyll in the Arctic Ocean is lower than in low-latitude ocean. Second, the spectral model, which exhibits the relationship of attenuation coefficients between 490 nm and other wavelength, was built and provided a new method to estimate the attenuation coefficient at other wavelength, if the attenuation coefficient at 490 nm was known. Third, the impact factors on attenuation coefficient, including sea ice and sea water mass, were discussed. The influence of sea ice on attenuation coefficient is indirect and is determined through the control of entering solar radiation. The linear relationship between averaging sea ice concentration(ASIC, from 158 Julian day to observation day) and the depth of maximum chlorophyll is fitted by a simple linear equation. In addition, the sea water mass, such as the ACW(Alaskan Coastal Water), directly affects the amount of chlorophyll through taking more nutrient, and results in the higher attenuation coefficient in the layer of 30–60 m. Consequently, the spectral model of diffuse attenuation coefficient, the relationship between attenuation coefficient and chlorophyll and the linear relationship between the ASIC and the depth of maximum chlorophyll, together provide probability for simulating the process of diffuse attenuation coefficient during summer in the Arctic Ocean.     

Distribution of Pacific-origin water in the region of the Chukchi Plateau in the Arctic Ocean in the summer of 2003

1Introduction Besidestheprecipitationandriverdischarges,the watersinthePacificOceanandtheAtlanticOceanare thesourcesoftheArcticOceanwater.TheAtlantic waterenterstheArcticOceanviatheFramStraitand theBarentsSea.Foritsdenserfeatureduetohigh salinity,mostofitsinkstothenorthofSvaldbardand circulatesinallthedeepbasinsintheArcticOcean, formingthedeepandbottomwatersoftheArcticO- cean(Aagaardetal.,1985;Rudelsetal.,1999).The BeringStraitistheonlychannelforthePacificwater toflowintotheArcticOce…     

2016年夏季北冰洋浮冰站近地层辐射和湍流通量观测

2016年8月7－14日中国第七次北极科学考察期间,在83°N附近设立的长期浮冰站开展了辐射和湍流通量观测研究。结果表明,观测期间反照率变化范围为0.64~0.92,平均反照率为0.78;基于现场观测数据评估了PW79、HIRHAM、ARCSYM和CCSM3 4种不同复杂度的反照率参数化方案在天气尺度的表现,最为复杂的CCSM3结果优于其他参数化方案,但不能体现降雪条件下的反照率快速增长。浮冰区冰雪面平均净辐射为18.10 W/m2,平均感热通量为1.73 W/m2,平均潜热通量为5.55 W/m2,海冰表面消融率为（0.30±0.22） cm/d,表明此时北冰洋浮冰正处于快速消融期。冰面的平均动量通量为0.098（kg·m/s）/（m2·s）,动量通量与风速有很好的对应关系,相关系数达0.80。