普若岗日冰原及其小冰期以来的冰川变化

普若岗日是藏北高原最大的由数个冰帽型冰川组合成的大冰原.冰川覆盖面积422.58km²,冰储量为52.5153km³.冰川雪线海拔5620～5860m.冰原呈辐射状向周围微切割的宽浅山谷溢出50多条长短不等的冰舌,最大的可伸至山麓地带,形成宽尾状冰舌.在一些下伸较低的冰舌段,形成有许多冰塔林,以雄伟壮观的连座冰塔林和雏形冰塔林为主.在东南部一些冰舌段雏形冰塔林的上部,分布着奇特的新月型雪冰丘和链状排列有序的雪冰丘.小冰期以来,普若岗日的冰川呈退缩趋势.环绕冰舌分布的冰碛序列,在北部和东南部普遍可区分出3道.对比研究认为,分别属于小冰期3次寒冷期冰进的遗迹.而西部小冰期冰川作用的范围较小.按小冰期最盛时的规模量测当时的冰川面积,和现在相比该时段内冰川面积减少了24.20km²,当时冰川面积比现在大57%.由此引起的冰川资源的减少为3.6583km³,相当于36.583×10⁸m³的水量.在普若岗日西侧,小冰期后期至20世纪70年代,冰川退缩了20m;70年代至90年代末,冰川退缩了40～50m;平均1.5～1.9m·a^-1;1999年9月至2000年10月,退缩4～5m.明显反映出逐渐加剧的变化趋势.和其它地区相比较,普若岗日冰原变化比较小,表现出比较稳定的状。     

Study on the change of Keqikaer Glacier during the last 30 years,Mt. Tuomuer,Western China

Using radio echo sounder, ice thickness of Keqikaer Glacier tongue was measured in 1981 and 2004. Data obtained by comparing topographical maps, aerial and satellite photographs at different times, illustrates changes of the thickness and advance/retreat of Keqikaer Glacier. Keqikaer Glacier has been in intensive retreat since the 1990s and become thinner since the 1980s. Measured thickness of the ice tongue indicates reducing with a speed of 0.5–1.5 m a⁻¹ since 1981. The shrinkage of the glacier terminus is less than 2% of the total length during the last 30 years; however, the retreat of terminus position and the thinning of the ice thickness provides significant information that these glaciers on the south slope of Mt. Tuomuer are in an intensively decreasing phase in recent time.     

A refined understanding of the paleoenvironmental history recorded at the Okanagan Centre section,an MIS 4 stratotype,south‐central British Columbia,Canada

The Okanagan Centre section is the stratotype for marine oxygen isotope stage (MIS) 4 sediments (Okanagan Centre Drift) in the southern interior of British Columbia, Canada. Previous work suggested that these sediments record two glacial and two interglacial cycles. This study reports on detailed sedimentological and geochronological investigations of lithostratigraphic units comprising the Okanagan Centre sequence, revealing successive deposition of subaqueous and subaerial outwash, a subglacial till and glaciolacustrine sediments during MIS 4. A limiting optical age of 113 ± 8 ka defines the base of this sequence. Sedimentological, paleopedological, optical dating and tephrochronological data from sediments near the middle of the sequence reveal soil development (MIS 3) in eolian sediments deposited on a river terrace overlying a deglaciated surface. Within these sediments, identification of Mt. St. Helens set C tephra suggest sedimentation between 50 and 35k ¹⁴C a BP. Optical dating corroborates the tephrochronology and suggests that this surface formed after ～52 ± 7 ka. The record of MIS 2 glaciation is restricted to deglaciation, and overlies MIS 3 sediments above an unconformity possibly related to regional subglacial meltwater erosion. Eolian sediments containing Mt Mazama set O tephra (～7.62k cal a BP) cap the sequence.     

Ice-core pollen record of climatic changes in the central Andes during the last 400 yr

This paper presents a high-resolution ice-core pollen record from the Sajama Ice Cap, Bolivia, that spans the last 400 yr. The pollen record corroborates the oxygen isotopic and ice accumulation records from the Quelccaya Ice Cap and supports the scenario that the Little Ice Age (LIA) consisted of two distinct phases—a wet period from AD 1500 to 1700, and a dry period from AD 1700 to 1880. During the dry period xerophytic shrubs expanded to replace puna grasses on the Altiplano, as suggested by a dramatic drop in the Poaceae/Asteraceae (P/A) pollen ratio. The environment around Sajama was probably similar to the desert-like shrublands of the Southern Bolivian Highlands and western Andean slopes today. The striking similarity between the Sajama and Quelccaya proxy records suggests that climatic changes during the Little Ice Age occurred synchronously across the Altiplano.     

Relative sea-level history from the Lambert Glacier region, East Antarctica, and its relation to deglaciation and Holocene glacier readvance

We present a relative sea-level (RSL) history, constrained by AMS radiocarbon-dated marine-freshwater transitions in isolation basins from a site adjacent to the Lambert Glacier, East Antarctica. The RSL data suggest an initial ice retreat between c. 15,370 and 12,660 cal yr B.P.. Within this period, meltwater pulse IA (mwp IA, between c. 14,600-14,200 and 14,100-13,700 cal yr B.P.) occurred; an exceptionally large ice melting event, inferred from far-field sea-level records. The RSL curve shows a pronounced highstand of approximately 8 m between c. 7570-7270 and 7250-6950 cal yr B.P. that is consistent with the timing of the RSL highstand in the nearby Vestfold Hills. This is followed by a fall in RSL to the present. In contrast to previous findings, the isolation of the lakes in the Larsemann Hills postdates the isolation of lakes with similar sill heights in the Vestfold Hills. An increase in RSL fall during the late Holocene may record a decline in the rate of isostatic uplift in the Larsemann Hills between c. 7250-6950 and 2847-2509 cal yr B.P., that occurred in response to a documented mid-Holocene glacier readvance followed by a late-Holocene retreat.     

祁连山西段小冰期以来的冰川变化研究

根据航空摄影相片、地形图、遥感影像数据,分析了祁连山西段自小冰期至1990年的冰川变化,得出该地区在小冰期至1956年间冰川面积减小幅度为16.9%,冰川储量减少了14.1%;1956-1990年间冰川仍以退缩为主,此时段冰川面积和储量减小量占1956年时相应量的10.3%和9.3%.分析认为冰川退缩主要与1956-1966年时段气温偏高、降水偏少有关,而且该流域区对应于1956-1966年间强负物质平衡的冰川退缩可能出现于1960年代中期至1970年代中期.     

西昆仑山古里雅冰帽深钻孔冰温的稳定态分析

在西昆仑山古里雅冰帽海拔６０７０ｍ处钻孔，深３０９ｍ，上部２００ｍ进行了温度测量。对实测资料作稳定态分析后，得出冰内温度梯度大，底部达融点的结果。算出地热通量为１１２ｍＷ／ｍ＾２，与青藏高原为高地热区的观点一致。     

Multibeam bathymetric and sediment profiler evidence for ice grounding on the Chukchi Borderland, Arctic Ocean

Multibeam bathymetry and 3.5-kHz sub-bottom profiler data collected from the US icebreaker Healy in 2003 provide convincing evidence for grounded ice on the Chukchi Borderland off the northern Alaskan margin, Arctic Ocean. The data show parallel, glacially induced seafloor scours, or grooves, and intervening ridges that reach widths of 1000 m (rim to rim) and as much as 40 m relief. Following previous authors, we refer to these features as “megascale glacial lineations (MSGLs).” Additional support for ice grounding is apparent from stratigraphic unconformities, interpreted to have been caused by ice-induced erosion. Most likely, the observed sea-floor features represent evidence for massive ice-shelf grounding. The general ESE/WNW direction of the MSGLs, together with sediment, evidently bulldozed off the Chukchi Plateau, that is mapped on the western (Siberian) side of the plateau, suggests ice flow from the Canada Basin side of Chukchi Borderland. Two separate generations of glacially derived MSGLs are identified on the Chukchi Borderland from the Healy geophysical data. The deepest and oldest extensive MSGLs appear to be draped by sediments less than 5 m thick, whereas no sediment drape can be distinguished within the resolution of the sub-bottom profiles on the younger generation.     

A new procedure for separating and measuring radiogenic isotopes (U, Th, Pa, Ra, Sr, Nd, Hf) in ice cores

A new method for the radiogenic isotope (U–Th–Pa–Ra, Sr, Nd, Hf) analysis of the soluble and insoluble components found within ice cores is presented. Melting experiments with rock standards in the presence of EDTA indicate that carbonates, as well as silicates, can be buffered sufficiently to preclude dissolution. The use of EDTA allows adsorbing species, such as Th and Hf, to remain in solution during melting thus fully separating the dust (insoluble) and sea salt (soluble) components of the ice after filtration. A new elemental separation scheme for low sample masses, less than 5 mg solid material, utilizes 4 primary ion exchange columns and two “clean-up” columns to fully isolate U, Th, Pa, Ra, Sr, Nd, and Hf while maintaining high yields. Elution schemes measured for USGS rock standards and a Chinese loess are presented to provide a comparison for variable matrix compositions. Mass spectrometer techniques were modified to measure small aliquots of the standards, equivalent to the amounts found in ice core samples, 10 ng and less. A MC-ICPMS was employed for the measurement of U, Th, Pa, Ra, and Hf; results of the experiments show that with ion yields up to 1%, rock standards have errors for ²³⁴U/²³⁸U of 1%, ²³⁰Th/²³²Th of 1.5%, [²²⁸Ra] of 9%, and ¹⁷⁶Hf/¹⁷⁷Hf of 100 ppm. MC-TIMS measurements of Sr and Nd show similar errors for small sample sizes: ⁸⁷Sr/⁸⁶Sr of 50 ppm and ¹⁴³Nd/¹⁴⁴Nd of 80 ppm. This new analytical method increases the number of possible tracers measured from a single sample, reducing separation times and sample consumption, as well as providing the addition of a radiometric clock, U-series, to the traditional suite of isotopic tracers, Sr, Nd, and Hf.     

利用GPS提取南极Amery冰架海潮信号

潮汐运动是冰架短期垂直运动的来源, 对冰架影响十分显著. 选取2003/2004年度南极夏季期间中国在Amery冰架上连续5 d的GPS数据, 利用GAMIT/GLOBK进行数据处理, 获取了由海潮引起的冰架垂向运动时间序列;垂直方向精度优于0.18 m, 并且和中国南极中山验潮站的潮汐变化曲线进行了对比, 获得了一致的结论. 利用GPS测量海潮可为精化南极地区的海潮模型提供可靠的现场数据, 对南极冰盖物质平衡研究及冰海交互动力学模型研究有着重要的作用.     

古里雅冰帽硝酸根离子的来源分析

古里雅冰帽的ＮＯ３＾－离子主要来自亚洲粉尘和闪电，它周围附近的地表对冰帽ＮＯ３＾－离子的贡献较少。现代人类活动产生的ＮＯｘ气体及海洋中的ＮＯ３＾－离子能够到达冰帽之上的量是微不足道的。     

Glacial dynamics and transport of debris during the final phases of the Weichselian Glaciation,southwest Skåne,Sweden

Late Weichselian glacial sediments were studied in three sections west of Lund, southwest Sweden. The lowermost sedimentary unit is a lodgement till containing rock fragments derived from the northeast-east. Fabric analyses indicate successive ice flow directions: from the northeast, east-northeast, south-southeast and then east. The last active ice movement in the area was from the east. Above the lodgement till are deglaciation sediments consisting of meltout till, flow till and glaciofluvial sand and gravel deposited in a subaerial stagnant-ice environment. The uppermost unit consists of glaciolacustrine clay and silt, containing abundant ice-rafted debris, deposited during a short-lived transgression phase when stagnant ice was still present in the area. At the westernmost site investigated, the petrographical composition of the deglaciation deposits displays a gradual change, with upwards increasing components of Cretaceous chalky limestone. The presence of this rock type requires a period of glacial transport from the south. This stratigraphy cannot be explained with traditional glaciodynamic models. A possible scenario can, however, be constructed using a previously published model (Lagerlund, 1987) where marginal ice domes in the southwestern Baltic area interact with the main Scandinavian Ice Sheet.     

Glacial imprints of the Okanogan Lobe,southern margin of the Cordilleran Ice Sheet

The glacial geomorphology of the Waterville Plateau (ca. 55 km²) provides information on the dynamics of the Okanogan Lobe, southern sector of the Cordilleran Ice Sheet in north‐central Washington. The Okanogan Lobe had a profound influence on the landscape. It diverted meltwater and floodwater along the ice front contributing to the Channeled Scabland features during the late Wisconsin (Fraser Glaciation). The glacial imprint may record surge behaviour of the former Okanogan Lobe based on a comparison with other glacial landsystems. Conditions that may have promoted instability include regional topographic constraints, ice marginal lakes and dynamics of the subglacial hydrological system, which probably included a subglacial reservoir. The ice‐surface morphology and estimated driving stresses (17–26 kPa) implied from ice thickness and surface slope reconstructed in the terminal area also suggest fast basal flow characteristics. This work identifies the location of a fast flowing ice corridor and this probably affected the stability and mass balance of the south‐central portion of the Cordilleran Ice Sheet. Evidence for fast ice flow is lacking in the main Okanogan River Valley, probably because it was destroyed during deglaciation by various glacial and fluvial processes. The only signature of fast ice flow left is the imprint on the Waterville Plateau. Copyright © 2004 John Wiley & Sons, Ltd.     

Early Holocene climate signals from stable isotope composition of ice wedges in the Chara Basin,northern Transbaikalia,Russia

Stable isotope composition of syngenetic and epigenetic ice wedges, radiocarbon age, and pollen spectra of the surrounding deposits were studied during long term investigations at the "Belyi Klyuch" site on the first(6-8 m height) terrace of the Chara River(720 m.a.s.l.) in northern Transbaikalia to assess climatic conditions during ice-wedge formation. It was revealed that Holocene ice wedges had been formed from 10 to 7.5 ka 14 C BP. The isotope composition(δ~(18)O, δ~2 H) of relict ice wedges is the lightest and amounts-23‰ and-185‰, correspondingly. The isotopic compositions of ice lenses from sandy loam above ice wedges are-15.7‰, and-133‰; of small ice wedge in peat and sand are-15.3‰ and-117.9‰, accordingly.Interpretation of the ice wedge isotope composition has yielded that mean winter temperatures during cold stages of Holocene optimum were lower than today, during warm stages they were close to modern ones. During the coldest stages of Holocene optimum the total annual freezing index varied from-5100 to-5700 ℃ degree days, i.e. 300-600 ℃ degree days colder than during extremely severe modern winters. The total annual thawing index varied from 1300 to 1800 ℃ degree days, which was slightly higher than modern ones.     

敦德冰芯中微粒含量与沙尘暴及气候的关系

在敦德冰芯不同粒径（＞２．０ｕｍ,２．０～２５ｕｍ,＞５．０４ｕｍ）的微粒数据处理基础上,进行了微粒的变化特征以及微粒所揭示的气候信息分析,并将其与小冰期以来的气候变化记录进行了对比．结果表明,微粒含量变化与极地微粒研究所得的结论基本一致,即微粒含量高时,气候多为冷干;微粒含量低时,气候多为暖湿微粒变化异常于这一规律时,多为尘暴发生之时微粒含量的多少与当地的大风强度、地形、尘暴的规模、频率和强度有关     

Last Deglaciation Climatic Fluctuation Record by the Palaeo-Daocheng Ice Cap,Southeastern Qinghai-Tibetan Plateau

The last deglaciation, a key period for understanding present and future climate changes, has long been the hot topic for palaeoclimatological study. The Qinghai-Tibetan Plateau(QTP) is often a target study area for understanding hemispheric, or even global environment changes. The glacial landforms on the QTP provide a unique perspective for its climate change. In order to investigate the onset of the last deglaciation at the QTP and its regional correlation, the terrestrial cosmogenic nuclides(TCN) 10 Be and 26 Al surface exposure dating was chosen to date the roche moutonnée, the polished surface and the moraine debris located at the palaeo-Daocheng Ice Cap(pDIC), southeastern QTP. Our results show that the onset of the last deglaciation is at about 19 ka, followed by another warming event occurring around 15 ka in the p-DIC area. These timings agree well with other records, e.g. equivalent with a rapid sea level rise at 19 ka and the onset of B?lling warming event at about 15 ka. Thus, our new data can provide good reveal constraint on the climate evolution at the QTP.     

Till mélange at Amsdorf, central Germany: sediment erosion, transport and deposition in a complex, soft-bedded subglacial system

Glacial mélange in the open-cast mine at Amsdorf, central Germany, consists of several square meters of large, sorted sediment blocks embedded in till. The blocks are composed of largely intact to slightly deformed glaciofluvial and glaciolacustrine sand, silt and clay, initially deposited in a proglacial lake (2–3 km up-ice) and subsequently overridden by a glacier. The blocks typically have cuboid to subrounded outlines, are randomly distributed in the till, and the contacts with the surrounding till are distinctly sharp. Underneath the mélange are varved clays which exhibit strong deformations occasionally intervening with entirely undisturbed areas. It is suggested that the blocks were entrained into debris-rich basal-ice by bulk freeze-on when the glacier sole was lowered onto the bottom of an overridden lake. After entrainment the blocks were transported englacially and re-deposited (with far-traveled till matrix) as a melt-out till from stagnant ice. The glacier moved mainly by sliding enhanced by low-permeability varved clays in the substratum. The glacier is believed to have been of a polythermal type. These results show that bulk freeze-on can lead to entrainment of soft sediment blocks at least 20 m² in size, and that these blocks can be englacially transported with little or no deformation for several kilometers and more. The occurrence of deformed and undeformed clays under the till mélange indicates a possible mosaic of coupled and decoupled ice, the latter caused by a thin, transient subglacial water film separating the bed from the glacier.     

Climate change on the Yucatan Peninsula during the Little Ice Age

We studied a 5.1-m sediment core from Aguada X'caamal (20° 36.6′N, 89° 42.9′W), a small sinkhole lake in northwest Yucatan, Mexico. Between 1400 and 1500 A.D., oxygen isotope ratios of ostracod and gastropod carbonate increased by an average of 2.2‰ and the benthic foraminifer Ammonia beccarii parkinsoniana appeared in the sediment profile, indicating a hydrologic change that included increased lake water salinity. Pollen from a core in nearby Cenote San José Chulchacá showed a decrease in mesic forest taxa during the same period. Oxygen isotopes of shell carbonate in sediment cores from Lakes Chichancanab (19° 53.0′N, 88° 46.0′W) and Salpeten (16° 58.6′N, 89° 40.5′W) to the south also increased in the mid-15th century, but less so than in Aguada X'caamal. Climate change in the 15th century is also supported by historical accounts of cold and famine described in Maya and Aztec chronicles. We conclude that climate became drier on the Yucatan Peninsula in the 15th century A.D. near the onset of the Little Ice Age (LIA). Comparison of results from the Yucatan Peninsula with other circum-Caribbean paleoclimate records indicates a coherent climate response for this region at the beginning of the LIA. At that time, sea surface temperatures cooled and aridity in the circum-Caribbean region increased.