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。     

一个北极区域冰海耦合模式的设置与应用

介绍了一个北极区域冰-海耦合数值模式的设置与应用。海洋模式基于MIT海洋环流数值模式,海冰动力学过程由Hibler的粘-塑模型发展而来。海冰的热力过程基于Winton提出的三层热力学模型。给出了耦合模式的基本框架,重点介绍了区域冰-海耦合系统中较为重要的程序包,如正交网格生成技术,中尺度涡的参数化,冰-海耦合及开边界处理等。以NCEP再分析资料为大气强迫场,模拟研究了北极夏季海冰范围异常的变化特征(1992—2007),模拟得到的海冰面积变化趋势与SSM/I观测资料进行了对比,两者相关系数达到0.88,模式基本反映了海冰的年际变化特征。以2007年为例,对比分析了9月份海冰密集度分布特征,模式结果得到的海冰范围略大于观测,但基本反映了2007年夏季海冰范围的衰减形态。     

北极海冰厚度的热力学和动力学影响因素研究评述

全球变化背景下,在过去的40年中,北极海冰范围快速减少,厚度显著变薄,同时多年冰向一年冰转化,这对区域乃至全球气候系统具有重要影响。海冰厚度作为气候变化的指示器,在大气-海冰-海洋之间的物质和能量交换过程中起着重要作用。本文通过综述国内外北极海冰厚度影响因子的研究进展,对影响北极海冰厚度的热力学和动力学过程进行了梳理和总结。在热力学方面,海冰厚度会受到大气-海冰和海冰-海洋两个界面处的热通量影响,其中,大气-海冰热力学过程的影响因素包括冰面特征、气温、水汽、降雨/降雪和云量等,主要通过海冰表面辐射收支和湍流热交换(感热和潜热)产生影响;而海冰-海洋界面处的热通量作为海冰厚度的重要影响因素,主要受太阳辐射对上层海洋的加热、风应力导致的垂向混合以及中低纬暖流输送的影响。在动力学方面,海冰厚度变化主要通过风和海流的共同驱动引起海冰输运和海冰的形变。大尺度环流异常也会通过大气-海冰-海洋相互作用对北极冰厚的热力学和动力学过程产生显著影响。     

2009年春夏季北极海冰运动及其变化监测

极地海冰对全球气候变化具有指示作用,北极海冰监测对全球气候环境变化研究意义重大。利用中国第3次北极科学考察（CHINARE-2008）长期冰站获取的海冰物质平衡浮标数据和MODIS影像对北极海冰运动及其变化进行监测。结果表明MODIS影像分类得到的海冰密集度效果较好,海冰与海水之间界线清晰。4月16日至30日长期冰站在自西北向东南的漂移过程中,海冰逐渐分裂,密集度下降,速度总体上不断减小。4月30日至5月19日期间海冰密集度变化比较大,尤其是5月8日,海冰密集度突然升高。结合对漂移轨迹的分析发现,这可能是受大风、洋流等因素影响,海冰产生回旋运动导致的。5月19日至7月6日海冰密集度上升,在格陵兰岛附近海冰运动受地形影响产生聚集现象,因此在该区域海冰密集度呈现上升趋势。     

海冰模式中融池参数化方案的伴随模式参数估计

融池是影响北南海冰变化的重要因子.但在目前广泛使用的海冰模式CICE6.0中,融池模拟与观测存在较大差异.CICE6.0中的CESM融池参数化方案可以计算融池覆盖率与深度,但其中的部分重要参数存在一定的经验性,影响了融池模拟.本南南为CICE6.0海冰模式的CESM融池参数化方案开发了伴随模式,利用CICE6.0海冰模...     

不同月海冰边界提取算法对南极海冰变化的影响分析

海冰与海水的交界地带是海-冰-气相互作用的重要区域,其变化会影响海洋生物栖息地的联通状态和海洋、大气的交换,确定海冰边界对于分析海冰动态变化具有重要意义[1-2]。被动微波传感器为长期监测海冰变化提供了大尺度的连续观测数据。从经典统计、随机集理论出发,应用三种由被动微波日均海冰密集度数据提取月均海冰边界的方法,分析三种月均边界的差异,以及不同月均边界提取方法对海冰长期变化分析的影响。     

基于GPS反射信号的岸基海冰探测研究

论述了全球导航卫星系统反射信号测量(GNSS-R)在海冰介电常数和海冰密集度方面的潜在的研究价值,对欧洲空间局在格林兰岛迪斯科海岸采集的海冰数据进行分析,处理了两种反射信号的幅度的量化关系,同时跟踪多颗GNSS卫星并且保证了数据处理时间的连续性和有效性。根据双极化反射信号的幅度极化比和模拟海冰表面复介电常数得出幅度极化比和海冰表面的介电常数变化之间的联系。     

1979—2015 年罗斯海海冰运动速度变化

基于美国冰雪数据中心的月平均海冰运动和海冰密集度数据, 建立了1979—2015 年罗斯海海冰运动 速度时间变化序列, 揭示了海冰运动速度的年际和季节变化特征, 探讨了海冰运动速度和海冰范围之间可 能存在的联系, 最后对影响海冰运动速度变化的因素进行了分析。结果表明, 1979—2015 年罗斯海海冰运动 速度总体呈现加快趋势, 海冰运动速度增加趋势最快的季节为秋季, 其次是冬季、春季和夏季。冬季海冰平 均运动速度最大, 依次是秋季、春季和夏季。海冰运动速度与海冰范围在37 年间均呈现上升趋势, 海冰范 围变化滞后海冰运动速度1—2 个月, 两者呈显著正相关关系, 海冰运动速度的增加导致罗斯海海冰范围不 断扩张, 进而影响南极整体海冰分布。罗斯海海冰运动速度与风速之间存在显著正相关关系, 风场是影响海 冰运动速度的一个直接因素。除此之外, 海冰运动还受到包括气压场、洋流场以及海洋阻力系数等的影响。     

基于GPS反射信号的岸基海冰探测的研究

本文论述了全球导航卫星系统反射信号测量（GNSS-R）在海冰介电常数和海冰密集程度方面的潜在的研究价值,对欧洲空间局在格林兰岛迪斯科海岸采集的海冰数据进行分析,处理了两种反射信号的幅度的量化关系,同时跟踪多颗GNSS卫星并且保证了数据处理时间的连续性和有效性。根据双极化反射信号的幅度极化比和模拟海冰表面复介电常数得出结论, 幅度极化比和海冰表面的介电常数变化有联系。     

南极海冰问题评述:观测

海冰通过其对地面反照率的作用以及对大气和海洋之间热交换的局地障碍和对世界海洋环流的作用在全球热平衡和气候变化中起着重要的作用。南极海冰又因其极为显著的时空变化引起越来越多的关注。海冰的观测是海冰研究的重要内容 ,本文综述了南极海冰观测的发展过程 ,着重介绍了卫星在探测南极海冰方面的重要进展 .     

基于CryoSat-2测高数据的北极格陵兰海海冰干舷高提取研究

北极是全球气候和环境变化的驱动器之一,获取北极海冰的时空特征和变化规律对研究北极以及全球气候变化意义重大。格陵兰海是北极海冰剧烈变化的区域之一,采用CryoSat-2的雷达测高数据,获取了格陵兰海的海冰干舷高分布,并利用波弗特环流计划(BGEP)仰视声呐(ULS)数据进行了验证。研究结果表明,格陵兰海海冰干舷高和分布范围存在明显的季节性变化特征,具体体现在格陵兰海海冰从10月份进入冻结期开始,海冰分布范围不断扩张,海冰干舷高也逐渐增大,2月份平均干舷高达到最大(0.2 m),之后格陵兰海海冰开始消融,覆盖范围不断内缩,9月海冰干舷高降至最小(0.13 m)。     

Variability of the ice export through Fram Strait in 1993–98: the winter 1994/95 anomaly

The origin of the large positive anomaly of the Fram Strait sea ice export which occurred in winter 1994/95 is analysed on the basis of a model simulation of the Arctic sea ice cover over the period 1993-98. The overall intra-annual and interannual variability in the model is in good agreement with observational estimates and the 1994/95 anomaly is well reproduced with an amplitude amounting to half of the mean winter value. Model results suggest that, concomitant to anomalous export velocities, larger than usual ice thickness in the strait contributes to the outstanding amplitude of the anomaly. Analysis on the ice thickness evolution in the strait indicates that the thick ice advected in Fram Strait at the end of the fall of 1994 originates in the anomalous cyclonic wind stress which prevailed during the preceding summer. This anomalous wind stress resulted in persistent convergence of the ice flow against the northern coasts of Canada and Greenland and in the formation of a large thickness anomaly north of Greenland. The anomaly then feeds the Fram Strait ice flow during those following winter months when the local wind forcing in the strait favours ice drift from the north-west. Our results suggest that short-term wind stress variations resulting in local thickness changes to the north of Fram Strait can lead to substantial variability of the Fram Strait ice export.     

Particle-laden Eurasian Arctic sea ice: observations from July and August 1987

During the summer 1987 expedition of the polar research vessel'Polarstern'in the Eurasian Basin of the Arctic Ocean, sea ice at about 84-86°N and 20-30°E was found to have high concentrations of particulate material. The particle-laden ice occurred in patches which often darkened more than half the ice surface at our northernmost positions. Much of this ice appeared to be within the Siberian Branch of the Transpolar Drift stream, which transports deformed, multi-year ice from the Siberian shelves westward across the Eurasian Basin. Lithogenic sediment, which is the major component of the particulate material, may have been incorporated during ice formation on the shallow Siberian seas. Diatoms collected from the particle-rich ice surfaces support this conclusion, as assemblages were dominated by a marine benthic species similar to that reported from sea ice off the coast of northeast Siberia. Based on drift trajectories of buoys deployed on the ice it appears that much of the particle-laden ice exited the Arctic Ocean through the Fram Strait and joined the East Greenland Current.
Very different sea ice characteristics were found east of the Yermak Plateau and north of Svalbard and Frans Josef Land up to about 83-84°N. Here sea ice was thinner, less deformed, with lower amounts of lithogenic sediment and diatoms. The diatom assemblage was dominated by planktonic freshwater species. Trajectories of buoys deployed on sea ice in this region indicated a tendency for southward transport to the Yermak Plateau or into the Barents Sea.     

The role of declining Arctic sea ice in recent decreasing terrestrial Arctic snow depths

The dramatic decline in Arctic sea ice cover is anticipated to influence atmospheric temperatures and circulation patterns. These changes will affect the terrestrial climate beyond the boundary of the Arctic, consequently modulating terrestrial snow cover. Therefore, an improved understanding of the relationship between Arctic sea ice and snow depth over the terrestrial Arctic is warranted. We examined responses of snow depth to the declining Arctic sea ice extent in September, during the period of 1979–2006. The major reason for a focus on snow depth, rather than snow cover, is because its variability has a climatic memory that impacts hydrothermal processes during the following summer season. Analyses of combined data sets of satellite measurements of sea ice extent and snow depth, simulated by a land surface model (CHANGE), suggested that an anomalously larger snow depth over northeastern Siberia during autumn and winter was significantly correlated to the declining September Arctic sea ice extent, which has resulted in cooling temperatures, along with an increase in precipitation. Meanwhile, the reduction of Arctic sea ice has amplified warming temperatures in North America, which has readily offset the input of precipitation to snow cover, consequently further decreasing snow depth. However, a part of the Canadian Arctic recorded an increase in snow depth driven locally by the diminishing September Arctic sea ice extent. Decreasing snow depth at the hemispheric scale, outside the northernmost regions (i.e., northeastern Siberia and Canadian Arctic), indicated that Arctic amplification related to the diminishing Arctic sea ice has already impacted the terrestrial Arctic snow depth. The strong reduction in Arctic sea ice anticipated in the future also suggests a potential long-range impact on Arctic snow cover. Moreover, the snow depth during the early snow season tends to contribute to the warming of soil temperatures in the following summer, at least in the northernmost regions.     

北半球夏季中高纬度大气阻塞对北极海冰变化的影响

利用NCEP/NCAR再分析逐日500 h Pa高度场资料,对北半球夏季中高纬度大气阻塞特征进行统计分析,发现大气阻塞活动频率高的地区主要集中在白令海峡区域、鄂霍次克海区域、欧亚大陆区域及格陵兰区域。而通过NSIDC提供的卫星观测资料发现近30年夏季海冰容易减少的区域正好对应阻塞活动北部的高纬度地区。分别通过对以上4个区域有阻塞发生相对没有阻塞发生时的500 h Pa位势高度场、地面温度场、850 h Pa经向瞬变热通量输送和平流输送等异常变化场进行对比分析,结果发现夏季中高纬度阻塞频率的增加对海冰的减少有显著影响,主要体现在阻塞的发生发展可通过增加高纬度地面温度、对极地的热量输送和暖平流输送来加快海冰的融化。这种阻塞引起的热力作用在鄂霍次克海和欧亚大陆区域效果更为显著。     

基于锚系观测的北冰洋加拿大海盆中层水变化研究

20世纪90年代以来,北极进入了以海冰快速减少为显著特征的快速变化时期。通过分析“波弗特流涡观测计划”在北冰洋加拿大海盆的4个站点上布放剖面观测系统所获得的2003—2011年的温度、盐度剖面观测数据,研究了加拿大海盆北极中层水的变化特征。在观测期间,加拿大海盆中央区中层水核心温度变化较小,楚科奇海台地区有明显下降特征,海盆中央区以北以及加拿大群岛陆坡边缘区核心温度呈持续升高趋势。北极中层水核心深度在4个站点都有不同程度的加深趋势,加深的程度和参与分析的表层淡水含量以及因海冰消失导致的风应力变化有一定的对应特征。4个站点表层(75—200 m)的热含量在无冰海域有明显的增长,在有冰海域热含量较稳定;加拿大海盆200—400 m和400—800 m深度范围内的热含量变化情况与中层水核心深度的变化情况一致,伴随着中层水核心深度加深至400 m乃至更深处,中层水的能量也逐渐下移,造成200—400 m水层能量普遍降低而400—800 m水层能量普遍增加。加拿大海盆4个观测站点因背景环境条件和所受影响的不同,造成了中层水的变化和响应趋势的差异。     

Snow and sea ice thermodynamics in the Arctic:Model validation and sensitivity study against SHEBA data

Evolution of the Arctic sea ice and its snow cover during the SHEBA year were simulated by applying a high-resolution thermodynamic snow/ice model (HIGHTSI).Attention was paid to the impact of albedo on snow and sea ice mass balance,effect of snow on total ice mass balance,and the model vertical resolution. The SHEBA annual simulation was made applying the best possible external forcing data set created by the Sea Ice Model Intercomparison Project.The HIGHTSI control run reasonably reproduced the observed snow and ice thickness.A number of albedo schemes were incorporated into HIGHTSI to study the feedback processes between the albedo and snow and ice thickness.The snow thickness turned out to be an essential variable in the albedo parameterization.Albedo schemes dependent on the surface temperature were liable to excessive positive feedback effects generated by errors in the modelled surface temperature.The superimposed ice formation should be taken into account for the annual Arctic sea ice mass balance.     

Contribution of a pathway through the Arctic Ocean to the recent reduction in the ice cover

The sea ice cover in the Arctic Ocean has been reducing and hit the low record in the summer of 2007.The anomaly was extremely large in the Pacific sector. The sea level height in the Bering Sea vs.the Greenland Sea has been analyzed and compared with the current meter data through the Bering Strait.A recent peak existed as a consequence of atmospheric circulation and is considered to contribute to inflow of the Pacific Water into the Arctic Basin.The timing of the Pacific Water inflow matched with the sea ice reduction in the Pacific sector and suggests a significant increase in heat flux.This component should be included in the model prediction for answering the question when the Arctic sea ice becomes a seasonal ice cover.     

西北冰洋楚科奇海台08P23孔氧同位素3期以来的古海洋与古气候记录

通过中国第三次北极科学考察在北冰洋楚科奇海台采集的08P23孔样品的多项指标分析以及与其他孔的沉积记录综合对比,将08P23孔沉积物初步分为氧同位素3期(MIS 3)-MIS 1的沉积序列。MIS 3以来,楚科奇海台08P23孔可以识别出5个显著的冰筏碎屑(Ice-Rafted Detritus,IRD)事件,分别出现在MIS 2和MIS 3。其中,MIS 3的IRD事件中碎屑碳酸盐岩主要来自于加拿大北极群岛分布广泛的古生代碳酸盐岩露头,MIS 2的IRD事件中碎屑石英可能来源于欧亚大陆边缘。该孔大部分层位浮游有孔虫左旋厚壁新方球虫Neogloboquadrina pachyderma(sinistral)(Nps)的δ18O和δ13C都轻于表层沉积物中的平均值。MIS 3中两个褐色层中偏轻的Nps-δ18O和Nps-δ13C值是由冰融水造成;MIS 1和MIS 3灰色层中偏轻的Nps的δ18O和δ13C值指示海冰形成速率的提高,导致轻同位素卤水的生产和下沉。MIS 2的Nps的δ18O和δ13C值变化趋势相反,是因为温度急剧降低导致Nps-δ18O变重,海水冻结成冰,海气交换明显降低使得Nps-δ13C偏轻。MIS 1和MIS 3的Nps的δ18O和δ13C受到融冰水或轻同位素卤水影响导致同时偏轻。     

Effect of shipping activity on warming trends in the Canadian Arctic

This paper presents a detailed account of the effect of shipping activity on the increasing trends of air temperatures in the Canadian Arctic region for the period of 1980–2018. Increasing trend of temperature has gained significant attention with respect to shipping activities and sea ice area in the Canadian Arctic. Temperature, sea ice area and shipping traffic datasets were investigated, and simple linear regression analyses were conducted to predict the rate of change(per decade) of the average temperature, considering winter(January) and summer(July) seasons. The results indicate that temperature generally increased over the studied region. Significant warming trend was observed during July, with an increase of up to 1℃, for the Canadian Arctic region. Such increasing trend of temperature was observed during July from the lower to higher latitudes. The increase in temperature during July is speculated to increase the melting of ice. Results also show a decline in sea ice area has a significant positive effect on the shipping traffic, and the numbers of marine vessel continue to increase in the region. The increase in temperature causes the breaking of sea ice due to shipping activities over northern Arctic Canada.