Late Holocene variations in Arctic shelf hydrology and sea-ice regime: evidence from north of the Lena Delta

Diatom assemblage studies are used to interpret past changes in river runoff (salinity) and sea-ice regime in the vicinity of the vast Lena River delta, southern Laptev Sea shelf. On the basis of their distribution in surface sediments, the shelf region outside the strong influence of riverine waters is characterized by a dominance in sea-ice diatoms and other marine species. Their numbers increase steeply (>20%) within the area of drifting pack ice. In contrast, the marginal zone of the delta, where exceedingly low salinities prevail, is marked by freshwater diatoms showing values higher than 70%. Using the environmental information from the surface sediments, the downcore distribution patterns of the main ecological groups of diatoms were investigated on a sediment core that covers the past 2800 cal. years BP. Although the freshwater group indicates some temporal variations in salinities, the study site north of the Lena River delta remained under a dominantly riverine influence for most of the three recognized phases. In contrast, the relative abundance of sea-ice species gives evidence that pack-ice conditions were more severe during the oldest phase (older than ~2700 cal. years BP). The most significant changes are observed in the uppermost core section (younger than ~300 cal. years BP) when the relative abundance of freshwater diatoms decreases from 80% down to below 20%. This dramatic decrease is interpreted as a major shift from a more northward-directed to the modern, dominantly eastern outflow pattern. Because the dispersal and fate of riverine waters and its role on the ice regime as well as on water mass properties is a central issue in understanding short- and longer-term climatic changes in the Arctic and beyond, it needs to be tested using more cores if this most recent change in outflow pattern from the delta is connected to climate change or simply a result of channel migration within the delta.     

Isotope (δD, δ<Superscript>18</Superscript>О) systematics in waters of the Russian Arctic seas

Oxygen and hydrogen isotope analysis was performed to study the processes of distribution of water masses and modification of their salinity in the Russian Arctic seas. A wealth of new isotopic data was obtained for freshwater (river runoff, Novaya Zemlya glaciers) and seawater samples collected along a set of extended 2D profiles in the Barents, Kara, and Laptev Seas. The study presents the first δD values measured for the Northeast Atlantic Deep Water NEADW dominated the water column of the Barents Sea (S = 34.90 ± 0.05, δD = +1.55 ± 0.4‰, δ¹⁸O = +0.26 ± 0.1‰, n = 44). This water mass is present in the Kara Sea and western Laptev Sea. The relationship between δD, δ18О, and salinity data was used to calculate the fractions of waters of different origin, including the fractions of continental runoff in waters of the Barents, Kara, and Laptev Seas. It was shown that the relationships between the isotopic parameters (δD, δ¹⁸О) and salinity in waters of the Kara and Laptev Seas is controlled by the intensity of continental runoff and sea ice processes. Sea ice formation is the main factor controlling the formation of the water column on the Laptev Sea shelf, whereas the surface waters of the middle Kara Sea are dominated by the contribution of river runoff. A very strong stratification in the Kara Sea is caused by the presence of a relatively fresh surface layer mostly contributed by estuarine water inputs from the Ob and Yenisei Rivers. The contribution of river waters reaches 40–60% in the surface layer in the central part of the sea and decreases to a few percent down 100 m water depth. Stratification in the western part of the Laptev Sea is controlled by the contribution of freshwater input from the Lena River and modification of salinity by sea ice formation.     

Paleohydrologic regimes in the southwestern Great Basin, 0–3.2 my ago,compared with other long records of “gobal” climate

The oxygen-isotope record from fossil foraminifera in deep-sea sediments is commonly used as a proxy for global ice volume. The linkage between δ¹⁸O and ice volume, however, is probably nonlinear. We have developed a simple numerical model of the isotopic response of the oceans to ice-volume change. The major features it simulates are (1) the changing mean isotopic composition of snow as a function of ice volume (colder snow temperatures forced by climate change and higher-elevation accumulation areas imply more negative mean δ¹⁸O); (2) the nonequilibrium isotopic composition of ice sheets (the past history of an ice sheet is integrated into its mean isotopic composition, which introduces a lag of isotopic “ice volume,” i.e., the measured δ¹⁸O record, scaled to ice-volume units, behind true ice volume); (3) selective preservation of isotopically more negative (colder, higher-latitude) ice (this geographic effect can selectively amplify or dampen the isotopic response to the ice-volume signal). We illustrate the response of our model to simple hypothetical ice-volume transitions of ice growth and ice decay. Sensitivity tests are illustrated for all model parameters. The results suggest that oxygen-isotope records reproduce the general patterns of ice-volume change fairly accurately. The foraminiferal isotope record, however, may misrepresent the true amplitude of the ice-volume signal and lag true ice volume by 1000 to 3000 yr.     

Sediment transport to the Laptev Sea (Siberian Arctic) during the Holocene — evidence from the heavy mineral composition of fluvial and marine sediments

Heavy mineral studies of East Siberian river sediments, Laptev Sea surface sediments, and a sediment core of the western Laptev Sea were carried out in order to reconstruct the pathways of modern and ancient sediment transport from the Siberian hinterland to the Laptev Sea. The modern heavy mineral distribution of Laptev Sea surface sediments reflects mainly the riverine input. While the eastern and central part of the Laptev Sea is dominated by amphibole, which is supplied by the Lena River, the western part is dominated by pyroxene imported from the Siberian Trap basalts by the Khatanga River. The distribution of garnet and opaque minerals is additionally influenced by hydrodynamic processes. As a consequence of their high density, these minerals are predominantly deposited close to the river mouths. Heavy mineral and sedimentological studies of a sediment core of the western Laptev Sea were applied to reconstruct the postglacial history of the shelf area during the last 11 ka. In the lowermost interval of the core (> c. 10 ka), high accumulation rates and a heavy mineral composition similar to that of the modern Khatanga river indicate fluvial conditions. Additionally, the high mica content in this interval may indicate meltwater inflow from the Byrranga mountains. Strong variations in accumulation rates, grain-size distribution, and heavy mineral composition are observed in the time interval between c. 10 and 6 ka, which represents the main transgression of the Laptev Sea shelf. During the uppermost interval (<6 ka), rather stable conditions similar to the modem situation prevailed.     

1936—2017年北极勒拿河流域气候变化及其对径流的影响

北极河流径流的变化会影响海冰热力过程和海洋温盐环流。基于全球降水气候学中心（GPCC）及俄罗斯水文气象部提供的1936—2017年间的气温、 降水和径流数据, 分析了北极勒拿河（Lena River）流域近80年来的气候和径流变化特征, 并探究了气候变化对径流的影响。通过分析得出： 研究期内勒拿河流域气温上升0.18 ℃·（10a）^-1, 降水量增加率为4.7 mm·（10a）^-1, 径流增加399 m³·s^-1·（10a）^-1。各个季节的径流均呈增加趋势, 其中春季径流增加最为明显, 冬季次之。春季径流的增加主要是由春季气温升高所致的积雪加速消融造成的, 其次是春季降水的补给。夏、 秋季径流增加的主要原因是降水的贡献, 气温升高加剧蒸发反而使径流减少。冬季径流的增加, 是由于气温升高导致冻土退化或活动层厚度增加, 促进更多冻结水进入径流过程, 致使径流增加。     

山西应县护驾岗冲沟阶地地层粒度特征与沉积环境

山西应县护驾岗冲沟阶地地层形成于66.46～33.62 ka,根据该剖面地层的粒度分布特征对该地区冲沟阶地的沉积环境进行了探讨。护驾岗冲沟阶地剖面的粒度分布特征显示:(1)剖面地层总体表现为自下而上由粗到细的正韵律沉积特征,结合野外观察将其分为4段(A—D段);(2)A段粒度分布特征变化不大,均以细砂为主,频率曲线为不对称单峰,概率累积曲线为2段式,以跃移搬运为主,分选相对较好,水动力较强,沉积环境稳定;(3)B—C段粒度分布特征变化较大,以粉砂和细砂为主,频率曲线为不对称双峰,概率累积曲线为2段式,以跃移搬运为主,分选较差,水动力较强,沉积环境不稳定;(4)D段粒度分布特征变化不大,以粉砂为主,频率曲线为不对称单峰,概率累积曲线为2段式,以悬移搬运为主,分选相对较好,水动力较弱,沉积环境稳定。总体来说,冲沟阶地形成于河流沉积环境,顶部为河漫滩沉积环境。粒度分布特征与古里雅冰芯氧同位素变化基本一致,因此护驾岗冲沟阶地粒度特征与沉积环境的变化归因于气候变化。     

Validation of ice‐wedge isotopes at Yituli'he,northeastern China as climate proxy

Inactive ice wedges are still present today at Yituli'he in the middle Da Xing'anling (Greater Hinggan) Mountains in northeastern China, which is the southernmost known site (50°37′N) with ice wedges in the Northern Hemisphere. However, it is uncertain whether the ice‐wedge isotope composition, characterized by low δ¹⁸O, δD and low deuterium excess values, is representative of the isotope signature of a broader region. In this paper, the ice‐wedge isotope compositions were examined in the context of the stable isotopes of precipitation from the nearby Global Network of Isotopes in Precipitation (GNIP) stations. In addition, the pollen spectra from the host sediments were analysed to provide additional information on local vegetation in order to better understand the climate conditions favouring ice‐wedge formation. The pollen spectra suggest that the Yituli'he ice wedges developed during the colder and wetter period after 6000 cal. a BP. The isotopes in the Yituli'he ice wedges are consistent with the isotope background recorded in atmospheric precipitation collected at the nearby GNIP stations. When the snow‐melt froze into ice veinlets, the isotope signals did not change substantially because of the strong, cold, continental anticyclones in winter as well as a strong temperature inversion that prevail in the Da Xing'anling Mountains. As the climate pattern did not change substantially, the neoglacial cold period is unlikely to have allowed for strong secondary fractionation of isotope records during ice‐wedge formation. Thus, the annual isotope signature can be interpreted as a valid archive of climate data.     

中国寒区水文学研究的新阶段 ——记我国杰出寒区水文学家叶柏生研究员的创新与贡献

我国杰出的寒区水文学家叶柏生研究员不幸因公殉职. 选取了叶柏生研究员若干代表性研究成果, 包括与他人的合作研究成果, 重点从冰川水文、 冻土水文和区域水文变化三方面总结了其对寒区水文学发展所做的创新与贡献. 文章列出了每项研究成果的核心内容, 并给予了简要评述. 所选成果中, 冰川水文方面研究涉及冰川对河川径流的调节作用、 冰川径流对气候变化的响应机理等; 冻土水文研究着重介绍了多年冻土变化对流域径流过程及其变化影响方面的系统性成果; 区域水文变化研究方面, 选取了降水观测误差修正、 气候变化对区域径流的影响等方面的创新成果. 这些研究成果极大地提高了我国在世界寒区水文学研究的地位, 对认识寒区水文过程及气候变化对水资源的影响具有重要科学意义.     

Organic matter in the bottom sediments of the Ob Bay: Distribution,nature, and sources

The lateral variability of main geochemical parameters of dispersed organic matter (DOM) in the bottoms sediments of the Ob Bay was studied using materials of areal geological survey. It was found that they correspond to background compositions of estuarine-delta facies of the Western Arctic shelf, being mainly determined by the influx of river run-off and coastal abrasion. The distribution of DOM and its components is controlled by the hydrodynamic regime of the water area and grain-size composition of sediments. The molecular composition of hydrocarbon markers (n-alkanes, cyclanes, and arenes) confirms the dominant role of terrigenous humic material in the formation of DOM of the bottom sediments, while temporal stability of quantitative and qualitative geochemical characteristics indicates the stability of the Ob Bay ecosystem.     

Oxygen isotope and palaeotemperature records from six Greenland ice‐core stations: Camp Century,Dye‐3, GRIP,GISP2, Renland and NorthGRIP

Oxygen isotope variations spanning the last glacial cycle and the Holocene derived from ice‐core records for six sites in Greenland (Camp Century, Dye‐3, GRIP, GISP2, Renland and NorthGRIP) show strong similarities. This suggests that the dominant influence on oxygen isotope variations reflected in the ice‐sheet records was regional climatic change. Differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios. Palaeotemperature estimates have been obtained from the records using three approaches: (i) inferences based on the measured relationship between mean annual δ¹⁸O of snow and of mean annual surface temperature over Greenland; (ii) modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile, or (iii) by using Monte Carlo simulation techniques. The third of these approaches was adopted to reconstruct Holocene temperature variations for the Dye 3 and GRIP temperature profiles, which yields remarkably compatible results. A new record of Holocene isotope variations obtained from the NorthGRIP ice‐core matches the GRIP short‐term isotope record, and also shows similar long‐term trends to the Dye‐3 and GRIP inverted temperature data. The NorthGRIP isotope record reflects: (i) a generally stronger isotopic signal than is found in the GRIP record; (ii) several short‐lived temperature fluctuations during the first 1500 yr of the Holocene; (iii) a marked cold event at ca. 8.2 ka (the ‘8.2 ka event’); (iv) optimum temperatures for the Holocene between ca. 8.6 and 4.3 ka, a signal that is 0.6‰ stronger than for the GRIP profile; (v) a clear signal for the Little Ice Age; and (vi) a clear signal of climate warming during the last century. These data suggest that the NorthGRIP stable isotope record responded in a sensitive manner to temperature fluctuations during the Holocene. Copyright © 2001 John Wiley & Sons, Ltd.     

Alkane and PAH biomarkers as tracers of terrigenous organic carbon in Arctic Ocean sediments

We present the first sedimentary biomarker study encompassing the entire Arctic Ocean. A large data set of organic markers for terrigenous, petroleum and combustion inputs [alkanes, hopanes and steranes, parent and alkyl polycyclic aromatic hydrocarbons (PAHs)] is examined for patterns in space and time using principal components analysis (PCA) and partial least squares (PLS). Biomarker patterns reveal the central Arctic Ocean basin sediments to be compositionally distinct from those of the Mackenzie River/Beaufort Sea and Barents Sea, but similar to those of the Laptev Sea. PAH distributions reflected in PAH ratios and PCA projections demonstrate that Arctic Ocean sediment is dominated by natural inputs to the extent that anthropogenic combustion PAHs are not significant. We find only modest changes between the glacial and post-glacial sediments for atmospherically transported hydrocarbon biomarkers, while particle associated biomarkers were captured strongly at basin edges during the glacial period, and much more evenly transported across basins during the post-glacial period. The orders of magnitude decreases in particle associated petrogenic alkanes and PAHs in central basins during glacial times, coupled with the uniformity of most petrogenic biomarker parameters for most basin and shelf locations, reflect a massive reduction in ice transport that makes the margins the most likely source of petrogenic material for the Pleistocene/Holocene central Arctic basins. The proximity of large coal deposits of various maturity levels along the Lena River, the overlap in PAH and biomarker composition of the Laptev Sea and surficial sediments from the central Arctic Ocean and the location of the Laptev Sea at the origin of the main Transpolar Drift all point to eroded coals from the Lena River/Laptev Sea as the likely source of petrogenic hydrocarbons to the central Arctic Ocean. The ubiquitous presence of allochthonous coal in Arctic Ocean surface sediments provides a major constraint on the use of petrogenic biomarkers to infer the presence of subsurface petroleum reserves.     

南海北部晚第四纪高分辨率浮游氧同位素地层学及其古气候信息

对南海北部MD05-2904孔45 m的连续沉积物中提取的浮游有孔虫Globigerinoides ruber(白色)进行稳定同位素分析, 得到晚MIS 8以来(时间跨度257 ka, 平均时间分辨率228 a)的高分辨率沉积记录, δ18O和δ13C的频谱分析显示了强烈的岁差(23.4 ka、19.8 ka)、半岁差(11.7 ka、9.9 ka)周期.MD05-2904孔MIS 24时间段的氧同位素记录了格陵兰冰心中发现的Dansgaard/Oeschger和Heinrich事件.与葫芦洞石笋记录及南海邻区浮游有孔虫氧同位素记录的对比显示了受季风控制的区域因素, 如降雨、河流输入导致的盐度变化等对表层海水组成的影响.氧同位素在MIS 3、MIS 6的早期以及MIS 7.4偏轻; 而在MIS 5.5偏重, 这种现象解释为降雨量和蒸发量共同作用的结果.而末次冰盛期高达6570 cm/ka的沉积速率反映了低海平面时孔位离岸距离缩短带来丰富的沉积物源.      

Late Quaternary ice-rich permafrost sequences as a paleoenvironmental archive for the Laptev Sea Region in northern Siberia

Ice-rich permafrost sequences with large polygonal ice wedges represent excellent archives for paleoenvironmental reconstruction. Such deposits contain numerous well-preserved records (ground ice, paleosols, peat beds, different types of fossils), which permit characterization of environmental conditions during a clearly defined period of the past 60 ka. Based on field investigations carried out within framework of the German-Russian project "Laptev Sea System 2000" on the Bykovsky Peninsula (SE of the Lena Delta) results from cryolithological studies, sedimentological analyses, as well as new radiocarbon data are presented. For the first time it is shown that the Ice Complex accumulated without significant interruptions from approximately 60 k.y. B.P. until the end of the Pleistocene. Geochemical data (total organic carbon, C/N, '¹³C_org) and the mass-specific magnetic susceptibility clearly show changing environmental conditions from stadial to interstadial times in the Late Pleistocene and during the transition to the Holocene. These results permit us to reconstruct the development of an Arctic periglacial landscape in the coastal lowland during Ice Complex formation in the Late Quaternary. This evolution coincided generally with the global environmental trend up to marine isotope stage 4.     

Estimation of atmospheric paleo-circulation based on isotope composition of ice wedges

Cryostratigraphy of frozen late-Pleistocene sediments was studied in natural exposures at the Arctic coastal area. The isotope composition of ice wedges was determined. The data base on isotope composition of syngenetic ice wedges and modern elementary ice veins was compiled for the Eurasian Arctic based on obtained data and available literature sources. Spatial distribution of the isotope composition of ice wedges, which indicates paleo-climatic conditions, was determined separately for Marine Isotope Stages (MISs) from MIS 1 to MIS 4 for the Eurasian Arctic. The pattern of this distribution has remained stable during the last 50 000 years, which indicates a stable trend in atmospheric circulation from 50 000 yr BP to the present.     

Hydrogeochemical and isotopic study of the Kumho River, Korea: implications for anthropogenic and seasonal effects

The geochemical and isotopic compositions of river water are controlled by different factors. The seasonal and spatial variations in the geochemical composition, δD, δ¹⁸O, and δ¹⁵N–NO₃ of the Kumho River were investigated to reveal the geochemical processes occurring at different seasons. The Kumho River, which runs through different geologic terrains with different land use characteristics, is the largest tributary of the Nakdong River, the longest river in South Korea. The data varied significantly according to the land use and the season. Each monitoring station showed the lowest concentrations of various ions during July, the rainy season, due to the increase of precipitation rate. The ionic concentrations gradually increased downstream by the mineral weathering and anthropogenic activity. At the upper regions of the river, Ca and HCO₃, which are closely associated with mineral weathering, were the most dominant cation and anion, respectively. The relatively high Si concentration of the headwater samples, caused by the weathering of volcanic rocks, also showed the importance of weathering in the upper regions mainly composed of volcanic rocks. The downstream regions of the Kumho River are mainly influenced by sedimentary rocks. At the lower reaches of the river, especially near the industrial complexes in Daegu, the third largest city in Korea, Na, Cl, and SO₄ became the dominant ions, indicating that the anthropogenic pollution became more important in regulating the chemical composition of the river. The increasing (Ca + Mg + Na + K)/HCO₃ ratio downstream also indicates that the anthropogenic effects became more important as the river flows downstream. The isotopic compositions of δD and δ¹⁸O indicate that the river waters were significantly affected by evaporation during May and July, but the evaporation effect was relatively low during October. The isotopic composition of δ¹⁵N–NO₃ increased downstream, also confirming that anthropogenic effects became more significant at the lower reach of the river and near Daegu.     

The Oxygen Isotope Composition of Ice Wedges of Ayon Island and Paleotemperature Reconstructions of the Late Pleistocene and Holocene of the Northern Chukotka

Syngenetic ice wedges have been investigated on Ayon Island. Their isotope composition and the geochemical characteristics of both ice wedges and enclosing sediments have been obtained; four ice-wedge stages have been distinguished. Paleo temperature reconstructions for Ayon Island and adjacent territories of northern Chukotka have been obtained based of these results. Almost identical trends in the distribution of ice-wedge isotope characteristics in the Arctic islands and in the lower reaches of the Kolyma River were observed, as well as differences in the magnitude of isotope oscillations during the transition from the Late Pleistocene to the Holocene compared to ice wedges of the Lower Kolyma region.     

An approach to estimate Lower Jurassic seawater oxygen‐isotope composition using δ18O and Mg/Ca ratios of belemnite calcites (Early Pliensbachian,northern Spain)

Palaeotemperature estimates from the oxygen‐isotope compositions of belemnites have been hampered by not knowing ancient seawater isotope compositions well enough. We have tackled this problem using Mg/Ca as a proxy for temperature and here, we present a ~2 Ma record of paired Mg/Ca and δ¹⁸O measurements of Jurassic (Early Pliensbachian) belemnites from the Asturian basin as a palaeo‐proxy of seawater oxygen‐isotope composition. From the combined use of the two approaches, we suggest a δ¹⁸O_w composition of about ?0.1‰ for the Jamesoni–Ibex zones. This value may have been increased by about 0.6‰ during the Davoei Zone due to the effect of waters with a different δ¹⁸O_w composition. These findings illustrate the inaccuracy of using a globally homogeneous ice‐free value of δ¹⁸O_w = ?1‰ for δ¹⁸O_carb‐based palaeotemperature reconstructions. Our data suggest that previous palaeotemperatures calculated in the region from δ¹⁸O values of belemnites may have been underestimated as the seawater oxygen isotopic composition could have been higher.     

Sedimentary architecture of a glaciolacustrine braidplain delta: proxy evidence of a pre‐Middle Wisconsinan glaciation (Grimshaw gravels,Interior Plains,Canada)

The erosional nature of glacial systems commonly results in removal of direct evidence of previous glaciation (e.g. till and moraine). Therefore, reconstruction of former ice‐margin positions may rely, in part, on indirect (proxy) evidence from the sedimentary record. This study examines the facies and sedimentary architecture of a pre‐Middle Wisconsinan sand and gravel deposit (the ‘Grimshaw gravels’), which is positioned between areas where previous stratigraphical investigations have identified single (Late Wisconsinan) and multiple (pre‐Middle to Late Wisconsinan) glaciation by the Laurentide Ice Sheet. Five facies associations (FAs) are characterized within the deposit, which, together with the sedimentary architecture, record a transition from a braided river environment in the west (FA1‐3) to a gravelly braidplain delta front in the east (FA4 and 5). We propose that the Grimshaw gravels braid delta formed at the margin of a body of water that occupied the ancestral Peace River valley, probably impounded by the LIS; hence, the Grimshaw braid delta provides proxy evidence of the presence of an ice margin (previously unrecognized) in the Peace River lowland prior to the Middle Wisconsinan. This study provides further understanding of the origin of the Grimshaw gravels deposit, allowing re‐evaluation of previous models of formation. These findings offer insight into the glacial history of the southwestern margin of the LIS, and may help to refine ice‐sheet reconstructions spanning the Wisconsinan glaciation.     

北麓河多年冻土区降水及河水稳定同位素特征分析

为了进一步全面理解和探索青藏高原水文水循环过程,采用同位素方法并结合气象资料对青藏高原北麓河区域2011年6~12月降水和河水稳定同位素时空特征进行分析。探讨了北麓河降水同位素与日平均气温、降水量之间的相互关系,同时也对比分析了北麓河降水和河水的同位素变化特征。结果表明:北麓河降水同位素在整个观测期内总体受温度控制,但存在季节变化,其中6~9月降水同位素受到温度和降水量效应的共同控制,9月以后则主要受温度的影响。河水同位素与降水同位素相似的变化特征,体现了降水补给特征,另外降水量也能够影响河水同位素变化:降水量小则降水对其影响较小,反之则大。与北麓河降水线相比,河水δ18O~δD关系的斜率和截距偏大,揭示该区域河水除了受大气降水的补给外,还受到区域水体内循环和蒸发分馏作用的影响。     

青藏高原东缘叠溪海盆地40～30kaBP高分辨率快速气候变化记录

对岷江上游地区叠溪古堰塞湖底部沉积物进行AMS14C定年,得到其沉积时间起始时间约为40.5kaBP。通过沉积物粒度特征的研究得知,粒度指标可以反映降水量变化进而反映气候干湿变化,此外,粒度均值曲线与格陵兰冰心(GISP2)及南京葫芦洞石笋氧同位素曲线的显著相似性说明,粒度特征对全球性气候变化有响应,可以反映气候的冷暖变化。由此,研究区古气候演变可以划分为3个阶段:阶段Ⅰ(40.5～33.4kaBP)气候冷干,阶段Ⅱ(33.4～31.7kaBP)气候暖湿,阶段Ⅲ(31.7～31.1kaBP)气候较暖湿。而粒度均值曲线与冰心及石笋氧同位素曲线的差异,一方面可能是由于地理位置的差异,另一方面可能与当时太阳辐射变化情况以及季风作用有关。