Review on Researches of Aragonite Saturation State in the Southern Ocean:A Key Parameter of Southern Ocean Acidification

The Southern Ocean is a strong sink for atmospheric CO₂, making it especially vulnerable to ocean acidification (OA). The aragonite saturation state (Ω_arg) of seawater has been used as an index for the estimation of OA, which plays a critical role in evaluating the living environment of marine calcified organisms. However, it is very difficult to perform the studies of OA and Ω_arg in the Southern Ocean due to its harsh climate. Therefore, in order to better understand the OA and its further influences, the advances of Ω_arg studies were summarized in the oceans surrounding the Antarctica. Significant spatial and temporal variations of surface seawater Ω_arg are demonstrated in the Southern Ocean. In general, the surface seawater Ω_arg shows a lower value in the off-shore areas than in the open oceans. And, Ω_arg also exhibits a strong seasonal cycle with a higher value in summer than in winter. The distributions of Ω_arg in vertical water column generally present a declining tendency from surface to bottom. In addition, the shoaling of Ω_arg horizon at high latitude could be attributed to the ventilation and upwelling of deep waters in the Southern Ocean. There are many factors that could impact the Ω_arg in the Southern Ocean, including sea ice melting, sea-air CO₂ exchange, biological activities and hydrological processes, etc. Finally, the future changes and key scientific problems of OA in the Southern Ocean are proposed.     

Controls of dimethyl sulphide in the Bay of Bengal during BOBMEX-Pilot cruise 1998

The air-sea exchange is one of the main mechanisms maintaining the abundances of trace gases in the atmosphere. Some of these, such as carbon dioxide and dimethyl sulphide (DMS), will have a bearing on the atmospheric heat budget. While the former facilitates the trapping of radiation (greenhouse effect) the latter works in the opposite direction through reflectance of radiation back into space by sulphate aerosols that form from oxidation of DMS in atmosphere. Here we report on the first measurements made on DMS in the Bay of Bengal and the factors regulating its abundance in seawater. Phytoplankton alone does not seem to control the extent of DMS concentrations. We find that changes in salinity could effectively regulate the extent of DMSP production by marine phytoplankton. In addition, we provide the first ever evidence to the occurrence of DMS precursor, DMSP, in marine aerosols collected in the boundary layer. This suggests that the marine aerosol transport of DMSP will supplement DMS gaseous evasion in maintaining the atmospheric non-sea salt sulphur budget.     

海洋中溶存甲烷研究进展

CH₄是大气中的重要微量气体，对全球变暖和大气化学有重要作用。海洋是大气甲烷的重要源和汇。开展海洋中溶存甲烷的研究，有助于了解海洋对大气甲烷和全球变化的贡献。综述了海洋中溶存甲烷的研究现状，着重介绍了海洋中溶存甲烷的分布特征、海气交换通量的估算及其生物地球化学循环，并探讨了该领域研究中存在的问题。     

Methyl bromide: ocean sources, ocean sinks, and climate sensitivity

The oceans play an important role in the geochemical cycle of methyl bromide (CH3Br), the major carrier of O3-destroying bromine to the stratosphere. The quantity of CH3Br produced annually in seawater is comparable to the amount entering the atmosphere each year from natural and anthropogenic sources. The production mechanism is unknown but may be biological. Most of this CH3Br is consumed in situ by hydrolysis or reaction with chloride. The size of the fraction which escapes to the atmosphere is poorly constrained; measurements in seawater and the atmosphere have been used to justify both a large oceanic CH3Br flux to the atmosphere and a small net ocean sink. Since the consumption reactions are extremely temperature-sensitive, small temperature variations have large effects on the CH3Br concentration in seawater, and therefore on the exchange between the atmosphere and the ocean. The net CH3Br flux is also sensitive to variations in the rate of CH3Br production. We have quantified these effects using a simple steady state mass balance model. When CH3Br production rates are linearly scaled with seawater chlorophyll content, this model reproduces the latitudinal variations in marine CH3Br concentrations observed in the east Pacific Ocean by Singh et al. [1983] and by Lobert et al. [1995]. The apparent correlation of CH3Br production with primary production explains the discrepancies between the two observational studies, strengthening recent suggestions that the open ocean is a small net sink for atmospheric CH3Br, rather than a large net source. The Southern Ocean is implicated as a possible large net source of CH3Br to the atmosphere. Since our model indicates that both the direction and magnitude of CH3Br exchange between the atmosphere and ocean are extremely sensitive to temperature and marine productivity, and since the rate of CH3Br production in the oceans is comparable to the rate at which this compound is introduced to the atmosphere, even small perturbations to temperature or productivity can modify atmospheric CH3Br. Therefore atmospheric CH3Br should be sensitive to climate conditions. Our modeling indicates that climate-induced CH3Br variations can be larger than those resulting from small (+/- 25%) changes in the anthropogenic source, assuming that this source comprises less than half of all inputs. Future measurements of marine CH3Br, temperature, and primary production should be combined with such models to determine the relationship between marine biological activity and CH3Br production. Better understanding of the biological term is especially important to assess the importance of non-anthropogenic sources to stratospheric ozone loss and the sensitivity of these sources to global climate change.     

The Air-Coastal Sea Chemical Exchange: A Case Study on the New Jersey Coast

The coastal marine atmosphere adjacent to large urban and industrial centers is in general strongly impacted by pollution emissions, resulting in high loading of pollutants in the ambient air. Among the airborne substances are certain trace elements from a variety of emission sources that can serve as micronutrients to marine organisms in coastal waters. High concentrations of such elements in coastal air can result in enhanced air-to-sea deposition fluxes to coastal waters. They could also be transported over the open ocean, affecting the composition of the remote marine atmosphere and then ocean ecosystems. To provide better understanding of the extent of air-to-sea deposition processes on the New Jersey coast, a heavily polluted coastal region on the US East Coast, a synthesis of observation data was carried out for selected trace elements, including Fe, Cd, Cr and Cu, derived from measurements of both size-segregated and bulk aerosol particles, as well as precipitation around the New Jersey coast. The atmospheric input of Hg was also estimated based on measurement data. Results indicated that the total deposition fluxes of most trace elements were higher in Northern coastal NJ compared to Southern coastal NJ, reflecting the differences in the source strengths of these element emissions between the two coastal regions. Dry deposition processes were more significant for common dust-derived elements, particularly Fe and Al, compared with their wet deposition fluxes. However, the processes of precipitation scavenging appeared to be more important for the elements that were often enriched in fine particles including Zn, Cu, Pb and Ni. The removal of Hg from the ambient air was overwhelmingly dominated by atmospheric wet deposition. In the future, atmospheric measurements at more sites on the NJ coast should be performed simultaneously to reduce the spatial and temporal uncertainties associated with atmospheric deposition fluxes estimated in this study.     

南极海冰与气候

在极区,海冰的形成在海洋上部和大气下部之间构成了新的交界面,改变了大洋表面的辐射平衡和能量平衡,隔离了海洋与大气之间的热交换和水汽交换;海冰冻融过程影响着大洋温、盐流的形成和强度;海冰对南大洋和南极大陆气象、气候有重要的影响,在气候环境系统中起着重要的作用。南极海冰作用区约占南半球雪冰作用区面积的58%,约占地球表面积的3.58%。其中,一年生海冰约占南极海冰区分布面积的83%;其分布面积从夏末2月份最小时的3×106 km2左右,到9月份冬末最大时的18×106 km2左右,一年中季节变化幅度可达15×106 km2,季节变化率>500%。海冰分布区域的年际变化较大。南极海冰区是影响季节和年际全球气候环境变化的重要区域。当前,国际南极海冰与气候研究的核心问题是海冰物理过程和在海冰区的海洋—大气相互作用。结合目前承担的研究课题,对国际南极海冰与气候研究的前沿动态和相关的国际计划进行了综述。     

古海水pH值代用指标——海洋碳酸盐硼同位素研究进展

仪器测量的海水pH记录太短，无法评估海水pH自然变化的频率和幅度,并预测未来大气CO₂急剧增加后海水酸度的响应。海相碳酸盐的硼同位素是目前恢复古海洋pH的有效途径，倍受古气候—环境学家的重视。评述了近年来海洋碳酸盐的硼同位素的最新研究成果和研究现状，重点探讨了海相碳酸盐的硼同位素的测定方法、硼同位素—pH模型和古海水pH恢复等前沿内容，旨在提供一个系统的海洋碳酸盐硼同位素—pH系统的基本概念及研究思路，以利于气候学、地质学界了解这一交叉领域的发展动态。     

Research Progress of Long-term Ocean Temperature Changes in the Southern Ocean

In the recent decades， a large amount of anthropogenic heat has been absorbed and stored in the Southern Ocean. Results from observations and climate models' simulations both show that the Southern Ocean displays large warming in the upper and subsurface ocean that maximizes at 45°~40°S. However， the underlying mechanisms and evolution processes of the Southern Ocean temperature changes remain unclear， leaving the Southern Ocean to be a hotspot of climate change studies in the recent years. The present study summarized the current progress in the observations and numerical modeling of long-term temperature changes in the Southern Ocean. The effects of changes in wind， surface heat flux， sea-ice and other factors on the ocean temperature changes were presented， along with the introduction to the role of oceanic mean circulation and eddies. The present study further proposed that a deepening of the understanding in the Southern Ocean temperature change may be achieved by investigating the fast and slow responses of the Southern Ocean to external radiative forcing， which are respectively associated with the fast adjustments of the ocean mixed-layer and the slow evolution of the deep ocean. Specifically， the striking and fast mixed-layer ocean warming north of 50°S is tightly related to the surface heat absorption over upwelling regions and wind-driven meridional heat transport， resulting in enhanced warming around 45°S. While in the slow response of the Southern Ocean temperature， the enhanced ocean warming shifts southward and downward， mainly associating with the heat transfer from oceanic eddies. The Southern Ocean temperature has pronounced climatic effects on many aspects， such as global energy balance， sea-level rise， ocean stratification changes， regional surface warming and atmospheric circulation changes. However， large model biases/deficiencies in simulating the present-day climatology and essential ocean dynamic processes last in generations of climate models， which are the main challenge in advancing our understanding in the mechanisms for the Southern Ocean climate changes. Therefore， to achieve reliable future projections of the Southern Ocean climate， substantial efforts will be needed to improve the model performances and physical understanding in the relative role of various processes in ocean temperature changes at different time scales.     

ENSO循环过程与南极海冰变化

应用1951-2001年ENSO特征指数(NINO1+2、NINO3、NINO4、NINO3.4、SOI)和1973-1998年南极海冰北界范围以及1950-2001年SODA海洋温度资料,分析探讨了ENSO循环过程与南极海冰之间的关系,研究了南大洋和太平洋海表温度与南极海冰之间的内在联系。结果表明,南极海冰变化与ENSO循环过程存在一定联系,特别是东南极海冰的变化与ENSO循环过程较为密切。这种遥相关关系表明,ENSO循环过程不仅与热带海洋自身的海 气相互作用存在密切关系,而且与南极海冰之间也存在一定的联系。当东南极海冰范围出现异常增大和减小时,在时滞一年之后,NINO循环指数将出现减弱和加强,而南方涛动指数将出现加强和减弱。这种相关关系的机制是通过大洋环流这一载体将异常海温向北输送来实现的。南极海冰范围的异常增加或减少,会直接影响南极绕极流的冷暖结构进而影响经向水体输送的异常,从而导致热带和副热带太平洋上层海温场的异常变化,对ElNino和LaNina事件的发生起到推动作用。     

Review on researchesof nitrous oxide inthe Southern Oceanand relative new technologies

Nitrous oxide is an important greenhouse gas,which has a long lifetime of about 120 years and has a 310 times greenhouse effect than CO₂. Since the industrial revolution, the atmospheric N₂O concentration has increased significantly by 20%. Ocean is a net source, about 1/3 of total oceanic souce. Southern Ocean is an important part of the global ocean system, has a unique hydrological characteristics. So far it is regarded as a significant natural source to the global N₂O flux according to the model studies. However,the field work is very limit, due to the fierce in situ conditions. The importance of N₂O reseaches of Southern Ocean, progresses of nitrous oxide researches, especially new technologies applied to underway N₂O measurements in the Southern Ocean are reviewed. The advance of field, model studies and their problems or uncertainties that need to be resolved are also discussed. The using of stable isotope methods will provide powerful tools for marine N₂O mechanism. Development of high precision monitoring technology is generally the driving force of future research. Developing techniques of laser spectroscopy in marine N₂O studies and measurment of N₂O in sea ice will provide powerful tools to differeciate the N₂O source sink characteristic, constrain their budget and formation mechanism in region such as Southern Ocean.     

上层海洋-低层大气科学研究计划

海洋和大气是地球系统的重要组成部分，其在全球气候变化中具有重要作用。上层海洋与低层大气研究（SOLAS）作为IGBPII第一个新的核心计划，以海洋中深度在100 m以上的水层和 1 000 m以下的大气边界层为主要研究对象，通过多学科的交叉研究，以揭示海洋与大气相互作用的物理和生物地球化学过程耦合及其在气候变化中的作用。SOLAS科学计划得到了世界各国的积极响应，已有16个国家向国际SOLAS科学委员会提交了SOLAS进展状况的国家报告。我国也制定了自己的科学研究计划重点研究中国近海的大气物质入海、海洋温室气体排放、海-气界面上的物质和能量交换过程及其对气候和环境的影响和反馈。     

全球冰-海洋耦合模式的海冰模拟

海冰是全球气候系统的重要分量 ,与大气和海洋的相互作用 ,直接影响大气环流和海洋环流 ,对气候及其变化具有重要影响。文中依据冰、海洋间的热力、动力耦合相互作用 ,改进冰海洋热力耦合方案 ,利用由中国科学院大气物理研究所的 30层海洋模式和基于Flato空化流体流变学的海冰动力模式和Hibler表面热收支平衡的零层海冰热力模式 ,建立全球冰海洋耦合模式。利用大气月平均气候资料 ,利用冰海洋耦合模式对全球海冰的分布及其季节性变化、海冰漂移进行了耦合模拟和分析。模拟的南半球海冰分布及季节变化与实际分析资料非常接近 ,比 2 0层冰海洋耦合模式的结果有显著改进。北半球海冰范围偏小 ,但季节变化的量值与实际相当一致。模拟的海冰速度场反映了南、北半球海冰漂移的主要特征 ,如北极的穿极漂流和南大洋的绕极环流等。对海冰密集度的分析表明 ,模拟结果得以改进原因在于改进的冰海洋热力耦合方案增强了融冰期冰海洋耦合系统海洋热通量增加—密集度减小—能量收支增加的正反馈机制。     

北极海冰减退引起的北极放大机理与全球气候效应

自20世纪70年代以来,全球气温持续增高,对北极产生了深刻的影响。21世纪以来,北极的气温变化是全球平均水平的2倍,被称为"北极放大"现象。北极海冰覆盖范围呈不断减小的趋势,2012年北极海冰已经不足原来的40%,如此大幅度的减退是过去1 450年以来独有的现象。科学家预测,不久的将来,将会出现夏季无冰的北冰洋。全球变暖背景下北极内部发生的正反馈过程是北极放大现象的关键,不仅使极区的气候发生显著变化,而且对全球气候产生非常显著的影响,导致很多极端天气气候现象的发生。北极科学的重要使命之一是揭示这些正反馈过程背后的机理。北极放大有关的重大科学问题主要与气—冰—海相互作用有关,海冰是北极放大中最活跃的因素,要明确海冰结构的变化,充分考虑融池、侧向融化、积雪和海冰漂移等因素,将海冰热力学特性的改变定量表达出来。海洋是北极变化获取能量的关键因素,是太阳能的转换器和储存器,要认识海洋热通量背后的能量分配问题,即能量储存与释放的联系机理,认识淡水和跃层结构变化对海气耦合的影响。全面认识北极气候系统的变化是研究北极放大的最终目的,要揭示气—冰—海相互作用过程、北极海洋与大气之间反馈的机理、北极变化过程中的气旋和阻塞过程、北极云雾对北极变化的影响。在对北极海冰、海洋和气候深入研究的基础上,重点研究极地涡旋罗斯贝波的核心作用,以及罗斯贝波变异的物理过程,深入研究北极变化对我国气候影响的主要渠道、关键过程和机理。     

Intermediate-scale sea ice — Atmosphere interactions over high southern latitudes in winter

Associations between polar air cloud vortices (polar lows), as an indicator of intermediate-scale atmospheric activity, and the Antarctic sea ice, are examined for the Southern Hemisphere winter (June–September). Seven consecutive winters, spanning a period of marked interannual variability of the atmospheric circulation and sea ice (1977–83), are analyzed using sets of DMSP (Defense Meteorological Satellite Program) imagery. Relatively high frequencies of polar lows are found in ice-edge and adjacent ocean latitudes. There is some evidence for an equatorward shift in the latitude of maximum monthly polar low occurrence during the June to September period. Polar low incidence over the Southern Hemisphere on interannual time scales shows a close association with positive sea ice anomalies in the longitudes of more frequent cold air outbreaks from higher latitudes. This is particularly apparent for winters of strongly anomalous circulation, such as FGGE (1979) and the major ENSO of 1982–83. However, for individual cases on daily to weekly time scales, the feedback of cold air — sea ice advance — polar low development is not always evident, and implies that additional processes may contribute to polar air cyclogenesis in the marginal ice zone.     

Potential for Southern Hemisphere climate surprises

Climate model results suggest that future climate change in Antarctica will be accompanied by continued strengthening and poleward contraction of the Southern Ocean westerly wind belt. Paleoclimate records suggest past changes in the westerly winds can be abrupt and that healing of the Antarctic ozone hole could lead to poleward contraction of the westerlies and increased meridional atmospheric transport of warm air regionally into Antarctica. An abrupt shift to more meridional circulation could lead to notable changes in moisture availability for extra‐Antarctic regions, increased Antarctic ice sheet disintegration and more rapid sea‐level rise.     

海洋中氟氯烃的研究进展

研究海洋中的氟氯烃对全球气候变化和海洋环流的研究有重要意义.氟氯烃不仅是温室气体,还破坏大气平流层中的臭氧,也是近代海洋科学研究的有效工具,可以作为化学示踪剂,广泛用于示踪海洋环流、水团运动混合过程、海洋通风过程,测定水团年龄、海水混合和循环速率以及海气交换速率等的研究.对过去几十年海洋中氟氯烃的研究进展进行了评述,介绍了海水中氟氯烃的分布特征与通量研究、氟氯烃在海洋中的应用及分析方法,同时简述了大气中氟氯烃的分布特征.概述了该研究领域有待进一步研究的问题.     

大气、海洋与固体地球的能量交换

通过对南极气温资料、南极臭氧资料、环南极海冰资料、太平洋海温资料、地球自转速度变化资料、厄尔尼诺和拉尼娜资料的模拟验证，发现厄尔尼诺事件发生与德雷克海峡海冰减少在时间上有一一对应关系。南极半岛海冰减少是太平洋环流速度减慢的原因，德雷克海峡的海冰起重要作用。大气、海洋与固体地球的角动量交换在南、北半球有不同的形式。强震起源于海平面振荡。     

Review of the Atmospheric Response to the Ocean Mesoscale Eddies

As one of the most important mesoscale ocean features, the mesoscale eddies are omnipresent and have significant impact on the overlying atmosphere. Based on the comprehensive review of the influence of mesoscale eddies on the atmospheric boundary layer and the local circulation, the corresponding physical mechanisms and their impacts on weather systems were presented systematically. ①Eddy-induced SST anomalies may modify the surface wind speed, horizontal divergence, cloud and precipitation through turbulence heat flux anomalies. Meanwhile, additional secondary circulations arise over the eddies. What is more, there are obvious regional and seasonal differences for atmospheric responses. ② Studies in the South China Sea, the Kuroshio Extension region and the Southern Ocean indicate that atmospheric responses to mesoscale eddies can be explained by the changes of sea level pressure or the vertical momentum transport. These two mechanisms can be distinguished by the phase relationship between the atmospheric anomaly center and the eddy core. Diagnosis on the inner dynamical processes may draw better conclusions. ③The energy conversions are affected by mesoscale eddies, which may affect storm tracks and jet streams, and finally result in distant influences on weather patterns. Moreover, sea temperature anomalies from sea surface to the thermocline associated with mesoscale eddies have significant impacts on the intensification and the maintenance of tropical cyclones.     

Sensitivity of the Northern Hemisphere climate system to extreme changes in Holocene Arctic sea ice

The extent of seasonal and perennial sea ice changed dramatically through the Late Quaternary and these changes influenced both the ocean and atmosphere by controlling the exchange of energy, moisture and gases between them, and by altering the planetary albedo. Reconstructing the changing patterns of sea ice distribution in the recent past remains one of the outstanding challenges to the paleo-community. To evaluate the importance of these reconstructions we performed sensitivity tests using NCAR's Community Climate Model (CCM3), and a series of prescribed sea ice extents designed to capture the full range of Arctic sea ice variability under interglacial (Holocene) and full glacial (Last Glacial Maximum) boundary conditions. Our simulations indicate that surface temperatures and sea level pressures in winter (DJF) are most sensitive to changes in sea ice, and that these changes are propagated over the surrounding land masses in the North Atlantic, but that equivalent changes in sea ice produce smaller corresponding changes in temperature or sea level pressure in the North Pacific region. A comparison between CLIMAP (Map Chart Series MC-36, Geological Society of America, Boulder, CO, 1981) and a more realistic assessment of LGM sea ice yields dramatic changes in winter temperatures and precipitation patterns across Eurasia. These differences, forced only by changed sea ice conditions, reinforce the need to develop accurate maps of past sea ice to correctly simulate Late Quaternary environments. Such reconstructions also will be essential to validate the next generation of sea ice models.     

Geological Drilling in Polar Regions: Progress and Perspectives

The Antarctic and the Arctic regions play a key role in global sea level change and carbon cycle, and reserve key information of the Cenozoic transition from a green-house to an ice-house Earth. They have become hot spots in earth science studies. The geological drilling projects in both polar regions (e.g., DSDP/ODP/IODP/ICDP) have achieved remarkable successes, which have freshened the knowledge of global environmental and climatic evolution. Along with the Cenozoic global cooling, the timing of glaciation was almost synchronous on both the Antarctic and the Arctic. Accompanied with the Antarctic ice sheet build-up and increased terrestrial weathering, the enhanced formation of Antarctic Bottom Water exerts significant impact on global ocean circulation. The volume of unstable West Antarctic Ice Sheet fluctuates during glacial-interglacial periods showing 40 ka obliquity cycles, its volume significantly reduced or collapsed during several peak interglacials or long warm intervals. The Southern Ocean plays a significant role modulating atmospheric CO₂ concentration, global deep water circulation and nutrient distribution, productivity at different time scales. Sea level responses to the waxing and waning of polar ice sheets at different time intervals were tested, which provide valuable clue for predicting future sea level changes. The upcoming IODP drilling projects on polar regions will keep focusing on the high latitude ice sheet development, Southern Ocean paleoceanographic evolution, land-ocean linkages in the Arctic, and the impacts on the global climate, which will provide important boundary conditions for predicting global future climate evolution.