An overview of late Holocene climate and environmental change inferred from Arctic lake sediment

The 14 papers in this Special Issue of the Journal of Paleolimnology report new records of Holocene climate and environmental change from Arctic lakes, with emphasis on the last 2000 years. The study sites span the high latitudes of North America and extend into northwestern Europe. The studies rely on multiple proxy indicators to reconstruct past climate, including: varve thicknesses, chironomid, diatom, and pollen assemblages, biogenic-silica and organic-matter content, oxygen-isotope ratios in diatoms, and the frequency of lake-ice-rafted aggregates. These proxies primarily document changes in past summer temperatures, the main control on physical and biological processes in lakes at high latitudes. The records will be integrated into a larger network of paleoclimate sites to investigate the spatial and temporal variability of climate change and to compare the paleoclimate inferences with the output of general circulation models. This is the Introduction to a series of fourteen papers published as a special issue dedicated to reconstructing late Holocene climate change from Arctic lake sediments. The special issue is a contribution to the International Polar Year and was edited by Darrell Kaufman.     

Holocene lake sediment records of Arctic hydrology

Although paleoclimatic research in the Arctic has most often focused on variations in temperature, the Arctic has also experienced changes in hydrologic balance. Changes in Arctic precipitation and evaporation rates affects soils, permafrost, lakes, wetlands, rivers, ice and vegetation. Changes in Arctic soils, permafrost, runoff, and vegetation can influence global climate by changing atmospheric methane and carbon dioxide concentrations, thermohaline circulation, and high latitude albedo. Documenting past variations in Arctic hydrological conditions is important for understanding Arctic climate and the potential response and role of the Arctic in regards to future climate change. Methods for reconstructing past changes in Arctic hydrology from the stratigraphic, isotopic, geochemical and fossil records of lake sediments are being developed, refined and applied in a number of regions. These records suggest that hydrological variations in the Arctic have been regionally asynchronous, reflecting the impacts of different forcing factors including orbitally controlled insolation changes, changes in geography related to coastal emergence, ocean currents, sea ice extent, and atmospheric circulation. Despite considerable progress, much work remains to be done on the development of paleohydrological proxies and their application to the Arctic.     

Pollen-based reconstructions of late Holocene climate from the central and western Canadian Arctic

Two lake-sediment cores from the western and central Canadian Arctic were used to investigate late Holocene climate variability in the region. Both cores were analyzed for pollen, organic matter, biogenic silica, and magnetic susceptibility, and were dated using a combination of ²¹⁰Pb and ¹⁴C techniques. Core MB01, from southwestern Victoria Island, provides a 2600-year-long record. Fossil pollen percentages, along with other parameters, suggest the occurrence of a cold period around 2400 cal year BP (450 BC), followed by slightly warmer conditions by 1800 cal year BP (150 AD), and a return to cooler conditions throughout much of the last millennium. Core SL06, from southern Boothia Peninsula, shows more subtle changes in pollen percentages over its 2500-year duration, but an increase in Cyperaceae and decrease in Oxyria pollen around 1400 cal year BP (550 AD) are indicative of warmer conditions at that time. Quantitative climate reconstructions from these pollen sequences were compared to two other pollen-based climate records from the region and indicate the presence of a widespread wet period ~1500 cal year BP (450 AD), and a cool and dry Little Ice Age. In the reconstructions based on pollen percentage data, the twentieth century summer temperature and annual precipitation in the central and western Canadian Arctic were comparable to that which occurred over the last 2500 years. However, pollen-influx values increase in the most recent sediments, suggesting high plant productivity during the late twentieth century.

Late Holocene environmental changes inferred from diatoms in a lake on the western Taimyr Peninsula, northern Russia

Changes in the diatom assemblages preserved in a sediment core taken from a small lake located north of arctic treeline on the western Taimyr Peninsula, Russia, were examined in order to investigate late Holocene (i.e., ca 5000 cal yr BP to present) climatic and environmental changes within the region. Early diatom assemblages were dominated by benthic Fragilaria taxa and indicate a transitional phase in the lake history, most likely reflecting lake development and environmental change associated with treeline retreat to the south of the study site. Concurrent with pollen and macrofossil evidence of a vegetation shift to shrub tundra in the catchment basin at ca 4200 cal yr BP, an increase in cold-water taxa, followed by little change in diatom assemblages until ca 2800 cal yr BP, suggests that conditions were relatively cool and stable at this time. The last 2000 years of the Middendorf Lake record have been marked by fluctuating limnological conditions, characterized by striking successional shifts between Fragilaria pinnata and Aulacoseira distans var. humilis. Recent conditions in Middendorf Lake indicate an increase in diatom taxa previously rare in the record, possibly associated with twentieth-century climatic warming. The Middendorf Lake record indicates that significant limnological change may occur in the absence of catchment vegetation shifts, suggesting late-Holocene decoupling of aquatic and terrestrial responses to climatic and hydrological change. Our study results represent one of the few paleoecological records currently available from northern Russia, and highlight the need for further development of calibration data sets from this region.     

青藏高原扎布耶盐湖晚全新世气候环境演化

青藏高原晚全新世气候变化具有不稳定性.在高原中部扎布耶盐湖边缘取得158.5cm沉积物,通过年代、孢粉、介形虫、粘土矿物、地球化学等多种环境指标,给出了湖区3.8cal. ka BP以来的气候环境演化.孢粉中草本花粉占绝对优势,其中又以蒿属为主,植被类型为水分条件稍好些的半荒漠化草原.粘土矿物主要是伊利石和绿泥石,伊/蒙混层矿物少量,说明湖区风化作用主要是物理风化.(Ca Mg)/CO2-3摩尔比值为0.22～0.96,小于1,CO2-3与Na 结合形成大量钠碳酸盐矿物如单斜钠钙石、氯碳钠镁石、水碱等.硼砂的出现说明湖区沉积环境稳定,但3.8～1.99 cal. ka BP硼等元素和碳酸盐含量变化幅度较大,湖区气候寒冷干燥,但冷暖干湿波动频繁.3.4～3.34 cal. ka BP介形虫壳大多破碎,说明此阶段水动力条件强,水体不稳定.1.99 cal. ka BP至今,气候相对温暖潮湿,波动较少.太阳辐射和西南季风强度的变化是造成气候变化的主要原因,冰川冻土对寒冷气候的放大作用也是湖区气候变化的一个重要原因.     

Diatom-based Holocene paleoenvironmental records from continental sites on northeastern Ellesmere Island, high Arctic, Canada

Stratigraphic changes in diatom assemblages from four small lakes on northeastern Ellesmere Island, high Arctic, Canada, provide a proxy lake-ice cover and paleoenvironmental record. Low absolute diatom abundances and a benthic Fragilaria (sensu lata) dominated assemblage during the postglacial (< 7.6 ka B.P.) to mid-Holocene record the moderating effects of locally retreating glaciers. Around 5.5 ka B.P. diatom concentrations begin to rise, reaching their highest levels (10⁹ valves per g dry sediment) between 4.2 and 3 ka B.P., interpreted to be the warmest period in this region. Topoclimatic differences between lakes on Hazen Plateau and those lower in Lake Hazen Basin account for the initial decline in diatom abundances in the upper lakes after 3 ka B.P. This change is thought to reflect a lowering of the regional snowline, accordant with widely recognized Neoglacial advances on Ellesmere Island and Greenland. Lakes in lower Lake Hazen Basin maintained extensive summer ice free conditions until ~ 1.9 ka B.P., after which diatom abundances declined, suggesting prolonged summer lake-ice cover through the remainder of the recovered Holocene record. Differences between the records presented here and those from coastal areas of the Canadian high Arctic highlight the unique topoclimatic characteristics and continentality of the Lake Hazen region, and possible effects that local marine environments may have had on coastal records. Such differences serve to demonstrate the inherent geographic variability of paleoenvironmental records from the high Arctic.     

基于北极航线的俄罗斯北极战略解析

北极航线是目前学术界关注的热点问题。我国学者多从中国的视角对此进行研究,而且研
究俄罗斯北极航线战略的成果较少。未来北极航线开发中俄罗斯将处于核心地位,研究俄罗斯的
北极航线战略问题意义深远。本文在收集大量第一手俄文资料的基础上,对俄罗斯北极航线开发
的历史、国家战略、北极政策实施的重点、机制和阶段进行了较深入的解析,以期对我国的北极航
线战略起到启示和借鉴作用。     

GCM-simulated hydrology in the Arctic duringn the past 21,000 years

The Paleoclimates from Arctic Lakes and Estuaries (PALE) project has chosen to conduct high resolution data-model comparisons for the Arctic region at 21 and 10 (calendar) ka BP. The model simulations for 21, 10, and 0 ka BP were conducted with the GENESIS 2.0 GCM. The 10 ka BP simulation was coupled to the EVE vegetation model. The primary boundary conditions differing from present at 21 ka BP were the northern hemisphere ice sheets and lower CO2, and at 10 ka BP were the orbital insolation and smaller northern hemisphere ice sheets. The purpose of this article is to discuss the hydrological consequences of these simulations.At the Last Glacial Maximum (21 ka BP) the large ice sheets over North America and Eurasia and the lower CO2 levels produced a colder climate than present, with less precipitation throughout the Arctic, except where circulation was altered by the ice sheets. At 10 ka BP greater summer insolation resulted in a warmer and wetter Beringia, but conditions remained cold and dry in the north Atlantic sector, in the vicinity of the remnant ice sheets. Less winter insolation at 10 ka BP resulted in colder and drier conditions throughout the Arctic. Precipitation - evaporation generally correlated with precipitation except where changes in the surface type (ice sheets, vegetation at 10 ka BP, or sea level at 21 ka BP) caused large changes in the evaporation rate. The primary hydrological differences (from present) at 21 and 10 ka BP correlated with the temperature differences, which were a direct result of the large-scale boundary condition changes.     

北极气候和陆地环境变化对第一产业影响研究进展

北极地区正在经历前所未有的气候及陆地环境变化,气温升高、植被绿化、冻土融化以及野火频发等因素已经对北极地区的第一产业产生了广泛而深远的影响。为了支撑气候变化背景下北极第一产业的可持续发展与相关政策的制定,有必要加强北极气候及陆地环境变化对第一产业影响的整体性认识。本文针对北极地区的种植业、畜牧业、林业以及渔业4个第一产业部门,系统梳理了它们受到气候及陆地环境变化影响的类型与程度。同时,本文基于跨部门视角总结了当前北极环境变化对第一产业影响的相关研究,并从5个方面进行了分析与展望：① 气候及陆地环境变化对第一产业的具体影响方式;② 整合局域性科学认识的挑战;③ 气候变化适应策略的制定与实施;④ 数据与方法层面的整合与创新;⑤ 气候变化影响下北极第一产业变化对中国的启示。本文总结了未来气候变化背景下北极第一产业研究的重点领域,可为中国参与北极第一产业资源的可持续利用与开发提供参考。     

毛乌素沙地东南缘全新世气候不稳定性

毛乌素沙地处于中国季风区的西北边缘,对气候变化敏感,是古气候演化和古环境变迁研究的理想场所。全新世气温回暖期,气候整体稳定但存在暖湿冷干的次级波动,不同类型沉积相组成的地层序列记录了全新世千年、百年尺度的气候不稳定性。对毛乌素沙地不同沉积序列的研究表明:(1)毛乌素沙地东南缘的沙漠/黄土边界带DLT、NB剖面粒度及Rb/Sr比值可作为气候变化的代用指标。>63 μm砂含量增加,Rb/Sr比值降低,揭示东亚冬季风增强,风成砂堆积,风沙活动加剧,气候干冷;反之,东亚夏季风增强,降水增多,风化成壤程度加大,气候暖湿。(2)毛乌素沙地东南缘沙漠/黄土边界带及低洼沟谷区年代概率密度函数的分析显示,全新世早期~8\^5 ka BP风成砂堆积,风沙活动加剧,气候表现为干冷;全新世中期8\^5 ka~3\^0 ka BP地势较高处古土壤广泛发育,地势低洼处发育湖沼相/泥炭层,但在6.0 ka BP左右存在气候转冷过程;全新世晚期3\^0 ka BP以来气候波动频繁。(3)毛乌素沙地气候变化与北大西洋冰筏冷事件、董哥洞石笋、季风边缘区湖泊、东部沙地等记录具有可对比性和相对一致性,反映出全新世千年和百年尺度上的气候变化主要受全球变化的影响,这对预测和模拟未来气候变化具有借鉴意义。     

Early and late Holocene water-level fluctuations of Lake Annecy, France: sediment and pollen evidence and climatic implications

Early and late Holocene water-level changes in Lake Annecy, France, were reconstructed from a sediment sequence from Annecy. Two early Holocene successive rises in lake level at ca. 8900-8700 BP are recorded. Another increase in lake level, beginning at ca. 780 BP, is documented. The higher lake-level conditions in Lake Annecy during the 9th millennium BP, i.e. between the Preboreal oscillation and the 8200 yr event, appear to coincide with a more widespread cooling period which has been recorded in western Europe, in the Greenland ice-sheet and the North Atlantic ocean. The rise in lake level at ca. 780 BP can be related to the early Little Ice Age.     

云南拱王山冰蚀湖相沉积剖面全新世孢粉记录与环境

对云南小江流域拱王山老碳房冰蚀湖相沉积剖面进行孢粉分析,结果显示,研究区自全新世以来经历了5次较明显的气候波动,即9 455~8 635 a(cal.)B.P.气候凉湿;8 635~7 095 a(cal.)B.P.气候冷湿;7 095~5 041a(cal.)B.P.气候寒冷而干燥;5 041~2 529 a(cal.)B.P.气候以凉湿为主;2 529 a(cal.)B.P.以来气候温暖湿润。分析结果与目前中国全新世新冰期与高温期交替及其气温变化规律有一定的差异。     

Arctic climate change discourse: the contrasting politics of research agendas in the West and Russia

In this paper we explore how Western scientific concepts and attitudes towards indigenous knowledge, as they pertain to resource management and climate change, differ from the prevailing view in modern Russia. Western indigenous leaders representing the Inuit and Saami peoples are actively engaged in the academic and political discourse surrounding climate change, whereas their Russian colleagues tend to focus more on legislation and self-determination, as a post-Soviet legacy. We contribute to the debate with data from the Nenets tundra, showing how different research has employed the three crucial Western research paradigms of climate change, wildlife management and indigenous knowledge on the ground. We suggest that the daily practice of tundra nomadism involves permanent processes of negotiating one's position in a changing environment, which is why "adaptation" is woven into the society, and cosmology as a whole, rather than being separable into distinct "bodies" of knowledge or Western-designed categories. We argue that research agendas should be placed in their proper local and regional context, and temporal framework: for example, by collaborating with herders on the topics of weather instead of climate change, herding skills instead of wildlife management, and ways of engaging with the tundra instead of traditional ecological knowledge.     

Geomorphology and late Holocene climatic change in Northeastern Spain

During the late Holocene, accumulation and downcutting stages affected the slopes and infilled valleys in the semiarid areas in NE Spain. The presence of archaeological remains, charcoal and ashes within slope deposits and valley fills makes it possible to carry out accurate datings. In the case of infilled valleys, the different accumulations may be diachronous at a regional level. These diachronisms among different infilled valleys may be caused by both human activity and complex responses of the system. On the slopes, one can distinguish between two accumulation periods separated by an incision period. The older accumulation stage has a widespread distribution and developed from the Bronze Age to the Iberian–Roman Epoch. The following accumulation period was formed in the Post-Medieval period and is spatially more restricted. Because of the widespread synchronism shown by these accumulations, a climatic cause is put forward as the possible triggering factor for the accumulation–incision stages in the slopes. The datings obtained indicate that the first accumulation corresponds to the Iron Age Cold Epoch (900–300 years B.C.) and the second to the Little Ice Age. Between both accumulation periods, a downcutting stage took place (approximately from 300 B.C. to 1450 A.D.). This downcutting interval can be related to the warm stages of the Subatlantic Period, during which there was a relatively lower percentage of vegetation cover. Finally, the last incision period, which is still taking place, has affected previous accumulations.     

Palynological study of Holocene sediments from Lake Doirani in northern Greece

A palynological investigation was conducted on two cores with Holocene sediments collected from the northeastern littoral part of the border Lake Doirani in northern Greece. The radiocarbon dates indicated that the analyzed sediments accumulated during the last 5000 yrs. The pollen-stratigraphic record revealed the environmental changes in the catchment area, starting from a natural undisturbed landscape to one modified by increasing anthropogenic influences. The tree vegetation dominated by Quercus woods in the lowlands and byPinus, Abies, and Fagus at higher altitudes, lasted for the period 2900 - 830 cal. B.C. Subsequently it was replaced by xerothermic herb and tree vegetation as a result of intensive human activity - and farming and stock-breeding. The accumulation of sediments with more sand and gravel in historical time was the result of increased erosion.     

近百年北极涛动对中国冬季气候的影响

北极涛动 (AO) 是北半球冬季热带外行星尺度大气环流最重要的一个模态,对北半球及区域气候有重要影响。利用中国近50年和近百年气温和降水资料分析了北极涛动对我国冬季气候的影响。当AO指数偏强时,我国大部分地区冬季气温偏高,同时降水也偏多。AO和西伯利亚高压对我国冬季气候的影响在年际和年代际尺度上有不同的特征, 在年际尺度上西伯利亚高压对我国气温的影响要远强于AO,而AO对我国降水的影响则比西伯利亚高压的影响要显著。这种关系也可以通过比较分析对流层低层和中高层环流形势在AO不同位相时的变化得到进一步验证。这说明AO对我国冬季气温和降水影响的机制是不一样的。在年代际尺度上,AO对气温和降水都有显著的影响。AO和西伯利亚高压一起能解释近百年来我国冬季温度和降水方差的35% 和11%。     

Late Holocene climate change and human disturbance on Andros Island, Bahamas

A 2 m sediment core from Church's Blue Hole on Andros Island, Bahamas provides the first paleoecological record from the Bahama Archipelago. The timing of events in the lower portion of the core is uncertain due to inconsistencies in the radiocarbon chronology, but there is evidence that a late Holocene dry period altered the limnology of Church's Blue Hole and supported only dry shrubland around the site. The dry period on Andros may correlate with a widespread dry period in the Caribbean from 3200 to 1500 yr BP. After the dry period ended, a more mesic climate supported tropical hardwood thicket around Church's Blue Hole. At c. 740 radiocarbon yr BP there is a sudden rise in charcoal concentration and a rapid transition to pinewoods vegetation, while at c. 430 radiocarbon yr BP charcoal concentration drops, but is higher again near the top of the core. Although climatic shifts could have caused these changes in vegetation and charcoal concentration, the changes post-date human colonization of the Bahamas and may reflect human arrival, followed by the removal of humans c. 1530 AD and the recolonization of Andros Island c. 200 years later.This is the 12th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.     

A comparison of climate changes between Arctic and China in the last 600 years

A compilation of paleoclimate records from lake sediments, trees, ice cores, and historical documents provide a view of China and Arctic environmental changes in the last 600 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic Ocean, Arctic and Greenland and ice cores from the Qinghai-Tibet Plateau, confirming the linkage of environmental changes of different time scales between the Arctic and China. It is shown that the changes of precipitation, temperature and sea ice cover in Arctic were correlated with climate changes in China. This paper also developed a comparative research on the climate changes between Arctic and China both during the Little Ice Age (LIA) and the instrumental observation period. Cycles and trend of temperature variations during LIA and temperature and precipitation during the instrumental observation period are performed. We found some similarities and differences of environmental changes between Arctic and China.     

东疆北部全新世气候不稳定性的湖泊沉积记录

对新疆东疆北部巴里坤湖2.5 m深的沉积剖面进行了年代学、沉积物粒度、TOC、磁化率和CaCO₃含量分析,对比研究确定了巴里坤湖的碳库年龄约为750 a,据此建立了研究剖面的年代序列。研究表明,各气候代用指标序列揭示了巴里坤湖地区全新世期间存在多次干湿气候波动,并伴随着一系列突发气候事件,其中有6次事件可以与全新世北大西洋浮冰碎屑事件及GISP2冰芯氧同位素记录进行良好对比,且呈现出显著约1.6 ka的变化周期,表明高纬度北大西洋地区的气候变化可能通过对西风环流的影响与中国西北干旱区的气候变化密切相关。谱分析揭示出研究区气候变化还具有显著的200 a,133 a,108 a和77 a周期,可能与太阳活动周期有关。6300—5200 cal a BP和4300—3500 cal a BP期间巴里坤湖地区气候较为干旱,结合广泛的区域对比认为,中全新世干旱事件具有普遍性。     

近600年来北极与中国气候变化的对比

A compilation of paleoclimate records from lake sediments, trees, ice cores, and historical documents provide a view of China and Arctic environmental changes in the last 600 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic Ocean, Arctic and Greenland and ice cores from the Qinghai-Tibet Plateau, confirming the linkage of environmental changes of different time scales between the Arctic and China. It is shown that the changes of precipitation, temperature and sea ice cover in Arctic were correlated with climate changes in China. This paper also developed a comparative research on the climate changes between Arctic and China both during the Little Ice Age (LIA) and the instrumental observation period. Cycles and trend of temperature variations during LIA and temperature and precipitation during the instrumental observation period are performed. We found some similarities and differences of environmental changes between Arctic and China.