CMIP5模式对冬季北极涛动的模拟和预估

基于NCEP/NCAR再分析资料和CMIP5的19个模式结果,从异常模态、年代际趋势和周期特征等方面评估了CMIP5耦合模式对冬季北极涛动(Arctic Oscillation,AO)的模拟能力,并对未来RCP4.5、RCP8.5两种浓度路径下AO的可能变化趋势给出了定性的预估。CMIP5模式历史试验结果显示,大多数模式都能够模拟出AO模态的基本结构,但是对中心位置、强度的模拟存在较大的偏差,其中MPI-ESM-LR和Had GEM2-AO能较好地模拟出AO整体模态来。在历史演变和周期特征的刻画方面,模式的冬季海平面气压经验正交函数分解第一模态时间序列(Principal Component,PC1)基本能够反映出1950~1970年以来的减弱趋势,但对1970年以后的增长趋势模拟并不明显,而北半球环状模指数(Zonal Index,ZI)序列对两个阶段的趋势均可模拟出来,模式的PC1和ZI序列总体表现为正的变化趋势。有一半以上的模式对2~3 a高频周期模拟较好,但对20 a左右的周期模拟较差,其中仅有Can ESM2、CNRM-CM5、GFDL-ESM2G这3个模式对ZI指数的两个周期变化模拟较好。在RCP4.5和RCP8.5两种浓度路径下,ZI序列有显著的上升趋势,从长期趋势系数看RCP4.5路径下有14个模式呈现正的变化趋势,其中有10个模式通过了检验。RCP8.5浓度路径下,16个模式为正变化趋势,有11个模式通过了检验,集合平均结果正变化趋势较为显著。两种浓度路径下不同时段的海平面气压变化趋势表明,ZI序列的年代际变化明显,存在3个不同的变化阶段——2006~2039年、2070~2100年为两个上升阶段,2040~2069年为缓慢下降阶段。     

北极低空急流和低层逆温特征观测分析

利用北冰洋冰表面热量平衡计划1997年10月中旬至1998年10月上旬的探空气球探测结果,分析了北极地区近地层逆温和低空急流特征.结果表明,96％的观测时次(11:15和23:15,协调世界时)出现近地层逆温,其中22％的逆温为贴地逆温,70％的逆温厚度在250～850 m之间,冬半年贴地逆温发生频率、逆温层厚度和逆温层内的温度变化都明显要大于夏半年.全年间低空急流出现频率为41％,平均高度为520 m,最大频率出现在150 m附近,70％的急流出现在600m高度以下.急流平均风速为10.6m·s-1,风速在4～13 m·s-1范围内的急流约占总数的75％,东和东南方向为全年急流的主导风向.根据对急流核和地面风速之间转换角分布的分析,惯性震荡可能是北极低空急流的主要成因.     

HY-2卫星扫描微波辐射计数据反演北极海冰漂移速度

本文基于最大互相关法,利用海洋二号（HY-2）卫星扫描微波辐射计37 GHz通道多时相垂直极化亮温数据,获取了北极海冰漂移速度。采用2012年和2013年国际北极浮标计划海冰现场观测数据,对利用微波辐射计亮温资料反演的冬季北极海冰漂移速度进行了定量验证,结果表明:流速和流向均方根误差分别为1.12 cm/s和16.37°,从一定程度上说明了HY-2卫星扫描微波辐射计亮温数据反演海冰漂移速度的可行性。此外,使用美国国防气象卫星F-17搭载的专用微波成像仪91 GHz通道垂直极化亮温,采用高斯拉普拉斯滤波方法进行处理,结合最大互相关法反演的海冰漂移速度,优于法国海洋开发研究院海冰漂移速度产品。     

CMIP5气候模式模拟的北极海冰特征及其季节变化

This paper is focused on the seasonality change of Arctic sea ice extent(SIE) from 1979 to 2100 using newly available simulations from the Coupled Model Intercomparison Project Phase 5(CMIP5).A new approach to compare the simulation metric of Arctic SIE between observation and 31 CMIP5 models was established.The approach is based on four factors including the climatological average,linear trend of SIE,span of melting season and annual range of SIE.It is more objective and can be popularized to other comparison of models.Six good models(GFDL-CM3,CESM1-BGC,MPI-ESM-LR,ACCESS-1.0,Had GEM2-CC,and Had GEM2-AO in turn) are found which meet the criterion closely based on above approach.Based on ensemble mean of the six models,we found that the Arctic sea ice will continue declining in each season and firstly drop below 1 million km~2(defined as the ice-free state) in September 2065 under RCP4.5 scenario and in September 2053 under RCP8.5 scenario.We also study the seasonal cycle of the Arctic SIE and find out the duration of Arctic summer(melting season) will increase by about 100 days under RCP4.5 scenario and about 200 days under RCP8.5 scenario relative to current circumstance by the end of the 21 st century.Asymmetry of the Arctic SIE seasonal cycle with later freezing in fall and early melting in spring,would be more apparent in the future when the Arctic climate approaches to "tipping point",or when the ice-free Arctic Ocean appears.Annual range of SIE(seasonal melting ice extent) will increase almost linearly in the near future 30–40 years before the Arctic appears ice-free ocean,indicating the more ice melting in summer,the more ice freezing in winter,which may cause more extreme weather events in both winter and summer in the future years.     

Development of best practices for scientific research vessel operations in a changing Arctic: A case study for R/V Sikuliaq

Reduced sea ice has made the Arctic Ocean more accessible for vessel traffic. In turn, the heightened interest to better understand rapidly changing sea ice dynamics, ecosystems, and related ocean processes in the Arctic Ocean has led to closer interactions with and the need to avoid potential conflicts between scientific researchers and Indigenous coastal communities. In particular, researchers need to minimize spatial and temporal overlap of science activities with subsistence hunts as the Arctic is essential to Indigenous communities for their food security and cultural heritage. In this regard, a Community and Environmental Compliance Standard Operating Procedure (CECSOP) was recently developed for the R/V Sikuliaq, which is owned by the National Science Foundation and operated by the University of Alaska Fairbanks College of Fisheries and Ocean Sciences and is part of the University-National Oceanographic Laboratory System. The CECSOP was developed with input and guidance from Alaska Indigenous community groups, state and federal agencies, and sea-going scientists. Here the document's basic principles and procedures are described, as well as its utility in helping guide constructive discussions and interactions between scientific users of R/V Sikuliaq and subsistence hunting communities when research and subsistence hunt activities have spatial and temporal overlap. The CECSOP is a “living” document and subject to future modifications and improvements. It may serve as a model for other scientific, commercial and industrial vessel operators to ensure best practices between subsistence hunting communities and vessel operators in the Arctic.     

Review on Researches of Legacy POPs and Emerging POPs in the Arctic Regions

The specific geographic location and natural conditions of the Arctic region play a significant role in the global climate change. As a result of perennial low temperature, simple ecological structure, and fragile ecosystem and weak stability in the Arctic, Persistent Organic Pollutants (POPs) accumulating from the region of middle and low latitudes may cause tremendous pressure in the arctic ecological environment. Therefore, the research of POPs in the Arctic region is not only conducive to more in-depth understanding of POPs distribution and transformation process in the global range, but to reasonably assess the harm of human activities on the arctic ecological environment. Thus, in the past 40 years, especially after nine new kinds of emerging organic contaminants being added to the list of Stockholm Convention in 2009, more and more scientific community and general public have pay attention to the research of POPs in the Arctic region. At present, the understanding of legacy POPs in the Arctic is limited, and the research of emerging POPs is in the initial stage. This paper aimed to summarize some conclusions and implications of the research, and focused on the occurrence level, historical evolution, bioaccumulation and source of POPs in atmosphere, waters, sediments and organisms in the Arctic region. Finally, the future changes and key scientific problems of POPs in the Arctic region were proposed.     

The changes of pigment contents and their environmental implications in the lake sediments of Ny-(A)lesund, Svalbard, the Arctic

According to palaeoclimatic and modern instrumental data, numerous studies have indicated that the Arctic climate has undergone a significant warming during the past 100 years, and this may lead to significant impact on the fragile lake ecosystem. In this study, we collected a lake sediment core from the Ny-(A)lesund of Svalbard and determined the concentrations of four pigments including chlorophyll derivatives, total carotenoids, oscillaxanthin and myxoxanthophyll in the sediments. Combined with other physical and chemical proxies such as calcium carbonate, total organic carbon, biogenic silicon etc., we have reconstructed the historical changes of lacustrine primary productivity in Ny-(A)lesund, especially for the past 100 years. The results showed that during the period of Little Ice Age (LIA), the climate was unfavorable for the growth of the lake algae, and thus the lacustrine productivity declined. This result was supported by the relatively low contents of pigment and biogenic silica in the sediments. In contrast, the contents of total organic carbon (TOC) and sediment pigments increased significantly in the upper 5 cm (~1890AD), reflecting the rapid growth of the lake algae, thus the great increase of lacustrine primary productivity, corresponding to the warming climate after LIA. However, the biogenic silica in the upper sediments still had a relatively low level, and this might be related to the growth competition with other algae species. Over the past 100 years, the ratio of Osc/Myx in the sediments decreased continuously, indicative of durative increase of myxoxanthophyll in blue-green algal pigments, and this might imply that the human activity had enhanced the nutrition level of the lake in the Arctic region.     

A coupled regional Arctic sea ice-ocean model: configuration and application

A regional sea ice-ocean coupled model for the Arctic Ocean was developed, based on the MITgcm ocean circulation model and classical Hibler79 type two categorythermodynamics-dynamics sea ice model. The sea ice dynamics and thermodynamicswere considered based on Viscous-Plastic (VP) and Winton three-layer models, respectively. A detailed configuration of coupled model has been introduced. Special attention has been paid to the model grid setup, subgrid paramerization, ice-ocean coupling and open boundary treatment. The coupled model was then applied and two test run examples were presented. The first model run was a climatology simulation with 10 years (1992?002) averaged NCAR/NCEP reanalysis data as atmospheric forcing. The second model run was a seasonal simulation for the period of 1992?007. The atmospheric forcing was daily NCAR/NCEP reanalysis. The climatology simulation captured the general pattern of the sea ice thickness distribution of the Arctic, i.e., the thickest sea ice is situated around the CanadaArchipelago and the north coast of the Greenland. For the second model run, themodeled September Sea ice extent anomaly from 1992?007 was highly correlated with the observations, with a linear correlation coefficient of 0.88. Theminimum of the Arctic sea ice area in the September of 2007 was unprecedented. The modeled sea ice area and extent for this minimum was overestimated relative to the observations. However, it captured the general pattern of the sea ice retreat.     

On the potential for climate change impacts on marine anthropogenic radioactivity in the Arctic regions

Current predictions as to the impacts of climate change in general and Arctic climate change in particular are such that a wide range of processes relevant to Arctic contaminants are potentially vulnerable. Of these, radioactive contaminants and the processes that govern their transport and fate may be particularly susceptible to the effects of a changing Arctic climate. This paper explores the potential changes in the physical system of the Arctic climate system as they are deducible from present day knowledge and model projections. As a contribution to a better preparedness regarding Arctic marine contamination with radioactivity we present and discuss how a changing marine physical environment may play a role in altering the current understanding pertaining to behavior of contaminant radionuclides in the marine environment of the Arctic region.     

Rapid physically driven inversion of the air–sea ice CO2 flux in the seasonal landfast ice off Barrow,Alaska after onset of surface melt

The air–sea ice CO₂ flux was measured over landfast sea ice in the Chukchi Sea, off Barrow, Alaska in late May 2008 with a chamber technique. The ice cover transitioned from a cold early spring to a warm late spring state, with an increase in air temperature and incipient surface melt. During melt, brine salinity and brine dissolved inorganic carbon concentration (DIC) decreased from 67.3 to 18.7 and 3977.6 to 1163.5 μmol kg⁻¹, respectively. In contrast, the salinity and DIC of under-ice water at depths of 3 and 5 m below the ice surface remained almost constant with average values of 32.4±0.3 (standard deviation) and 2163.1±16.8 μmol kg⁻¹, respectively. The air–sea ice CO₂ flux decreased from +0.7 to −1.0 mmol m⁻² day⁻¹ (where a positive value indicates CO₂ being released to the atmosphere from the ice surface). During this early to late spring transition, brought on by surface melt, sea ice shifted from a source to a sink for atmospheric CO₂, with a rapid decrease of brine DIC likely associated with a decrease in the partial pressure of CO₂ of brine from a supersaturated to an undersaturated state compared to the atmosphere. Formation of superimposed ice coincident with melt was not sufficient to shut down ice–air gas exchange.