Geomorphic and climatic change over the past 12,900 yr at Swiftcurrent Lake, Glacier National Park, Montana, USA

Glaciated alpine landscapes are sensitive to changes in climate. Shifts in temperature and precipitation can cause significant changes to glacier size and terminus position, the production and delivery of organic mass, and in the hydrologic energy related to the transport of water and sediment through proglacial environments. A sediment core representing a 12,900-yr record collected from Swiftcurrent Lake, located on the eastern side of Glacier National Park, Montana, was analyzed to assess variability in Holocene and latest Pleistocene environment. The spectral signature of total organic carbon content (%TOC) since ~ 7.6 ka matches that of solar forcing over 70-500 yr timescales. Periodic inputs of dolomite to the lake reflect an increased footprint of Grinnell Glacier, and occur during periods when sediment sinks are reduced, glacial erosion is increased, and hydrologic energy is increased. Grain size, carbon/nitrogen (C/N) ratios, and %TOC broadly define the termination of the Younger Dryas chronozone at Swiftcurrent Lake, as well as major Holocene climate transitions. Variability in core parameters is linked to other records of temperature and aridity in the northern Rocky Mountains over the late Pleistocene and Holocene.     

天山托木尔峰科其喀尔巴西冰川表面运动速度特征分析

天山托木尔峰科其喀尔巴西冰川是典型的树枝状山谷冰川,利用3组(6期)ASTER遥感影像通过COSI-corr软件反演了该冰川表面运动速度.与花杆测量数据进行对比,反演冰川表面运动速度平均绝对误差为3.1 m·a-1,相对误差为11.9%,二者在空间上的分布基本一致,表明其反演精度符合要求.在此基础上,分析冰川表面运动速...     

天山乌鲁木齐河源1号冰川雪层中NO_3~-的演化过程

根据2004年11月至2005年10月在天山乌鲁木齐河源1号冰川积累区采集的雪坑样品研究发现,雪层中NO3-平均浓度存在季节性变化特征,湿季（4~10月）的NO3-浓度明显低于干季（11月至次年3月）。特别是在春季,在雪层上部出现的浓度峰,经过夏季淋溶改造,稀释并合并为稳定的浓度峰;雪层中各浓度峰普遍处于向下迁移的过程...     

Selected Trace Elements in Snowpack on Urumqi Glacier No. 1, Eastern Tianshan, China: As Yielded by Leaching Treatment Representative of Real-World Environmental Conditions

To investigate the seasonal variability and potential environmental significance of trace elements in mountain glaciers, the surface snow and snow pit samples were collected at Urumqi Glacier No. 1 (43o06'N, 86o49'E, 4 130 m a.s.l.), eastern Tianshan (天山), from September 2002 to September 2003, and analyzed for Li, V, Cr, Mn, Co, Cu, and Ba. The samples were acidified (leached) in a manner intended to reasonably approximate the extent to which the natural hydrologic and weathering cycles would liberate elem...     

科其喀尔冰川冰面湖温度变化及其热机制

基于2007年7～9月对科其喀尔冰川消融区冰面湖、表碛、裸冰的温度和消融观测,分析三者的温度变化特征及其差异,探讨冰面湖的热机制.结果表明:科其喀尔冰川冰面湖表层水温受瞬时天气状况影响明显,变化趋势与气温一致,但不如气温变化剧烈并有1～3h滞后性;由于白天冰川融水注入与表层暖水混合下沉,深层湖水在一天的14～16时左右...     

Snow accumulation, melt, mass loss, and the near-surface ice temperature structure of Irenebreen, Svalbard

This study examines the mass balance, accumulation, melt, and near-surface ice thermal structure of Irenebreen, a 4.1 km² glacier located in northwest Spitsbergen, Svalbard. Traditional glaciological mass balance measurements by stake readings and snow surveying have been conducted annually at the glacier since 2002, yielding a mean annual net mass balance of −65 cm w.e. for the period 2002–2009. In 2009, the annual mass balance of Irenebreen was −63 cm w.e. despite above-average snow accumulation in winter. The near-surface ice temperature in the accumulation area was investigated with automatic borehole thermistors. The mean annual surface ice temperatures (September–August) of the accumulation area were −3.7 °C at 1 m depth and −3.3 °C at 10 m depth. Irenebreen is potentially polythermal, with cold ice and a temperate surface layer during summer. This temperate surface layer is influenced by seasonal changes in temperature. In winter, the temperature of all the ice is below the melting point and temperate layers are probably present in basal sections of the glacier. This supposition is supported by the presence of icings in the forefield of Irenebreen.     

Concentration of trace elements and their sources in a snow pit from Yuzhu Peak, north-east Qinghai-Tibetan Plateau

In order to understand the potential influence of pollution from human activity on the natural cycle of trace elements in the atmosphere over the eastern Kunlun mountains, north-eastern part of the Qinghai-Tibetan Plateau, concentrations of Al, Fe, Ba, Cd, Co, Cr, Cu, Li, Ni, Zn, Pb, Sb, Sr, U and V in a 75 cm-deep snow pit recovered from 5,800 m a.s.l. of the Yuzhu Peak Glacier on October 25, 2009, were determined by a sector field inductively coupled plasma mass spectrometry. The results indicate that concentrations of the measured trace elements vary by orders of magnitude from one element to another ranging from the minimum value 1.2 pg/g (U) to the maximum value 293 ng/g (Fe); the value of Max/Min ranges from 7 pg/g (Sd) to 358 pg/g (Li). EFc values of measured trace elements show that there are other important sources except dust for Cd, Sb, Zn, Pb and Cu. Comparison of the concentrations of the measured trace elements with those in other areas in the Tibetan Plateau indicates that trace element concentrations for Yuzhu Peak are lower than those in east Tianshan and Muztagh Ata (Pamirs). Concentrations of some trace elements are also lower than those in East Rongbuk Glacier. However, concentrations of all measured trace elements are extensively higher than those in Greenland and the Antarctic.     

Sampling strategy to describe the temporal hydrochemical characteristics of an alpine proglacial stream

A hierarchical sampling programme (including continuous monitoring, twice-daily sampling and sampling at hourly intervals over selected 24 hour periods) was devised to support hydrochemical and hydrological research programmes on an alpine proglacial stream. The rationale for the research and for the sampling programme are explained and the hydrochemical time series generated over an ablation season are analysed to assess the degree to which they support the study aims. It appears that there is no satisfactory substitute for the chemical analysis of at least two water samples taken at approximately maximum and minimum discharge every day, if seasonal variations in meltwater chemistry are to be effectively characterized. Such time series data can be used to estimate Box-Jenkins transfer function-noise models between particular solutes (SO²⁻₄, Ca²⁺, Mg²⁺, Na⁺ and possibly K⁺) and either discharge or electrical conductivity, which can then be used to fill any short gaps in the data. This approach is not satisfactory even for filling short gaps in the twice-daily determinations of pH, HCO⁻₃ and NO⁻₃. At the diurnal time-scale (based on hourly determinations over 24 hour periods) electrical conductivity seems to provide a good surrogate for most of the solutes studied. HCO⁻₃, SO²⁻₄, Ca²⁺ and Mg²⁺ were found to be particularly strongly related to electrical conductivity and there was little if any significant serial autocorrelation in the residuals from all of the simple linear regression relationships that were estimated between individual species and conductivity. It is concluded that the hierarchical sampling design was suitable for the purposes of the study, and that the continuous monitoring of electrical conductivity provides excellent supporting information to the chemical analysis of water samples if it is used carefully as a means of short term calibration and interpolation of the solute record.     

Fluctuations of the South Patagonian Ice-field during the last glaciation and the Holocene

Mapping along a transect from the southeastern margin of the South Patagonian Ice-field in Torres del Paine National Park (Chile) to the limits of fresh moraines of the last glacial cycle indentified eight glacier advances. The four younger ones have been dated by dendrochronology, tephrochronology and radiocarbon dating. Although the bases of 10 m deep bogs were sampled, close limiting radiocarbon dates were not obtained because bog formation in this rain-shadow area appears not to have commenced until ca.12000 yr ago. The outermost Little Ice Age moraine formed during the seventeenth century and three inner ones were deposited around ad 1805, 1845 and after 1890. Densely vegetated older moraines contiguous with Little Ice Age deposits are possibly of late Holocene age. Tephra from the eruption of Reclus volcano at ca. 11 880 yr BP was incorporated by a readvance that deposited large multiple moraines 10–16 km from the modern ice-front; the oldest basal peat found inside the moraine has been dated to ca. 9200 yr BP. These bracketing dates indicate that some eastern outlet glaciers of the ice-field advanced at a time when some western tidewater outlet glaciers terminated inside their modern limits. This questions the view of J. H. Mercer and other that Patagonian glaciers did not readvance during the late-glacial interval. A stadial event also occurred when the glaciers were some 18–20 km from their modern positions and is closely dated to ca. 11880 yr BP because Reclus pumice flushed down-glacier forms thick upper beds in outwash deltas deposited in proglacial lakes. The four older moraines pre-date the late-glacial eruption of Reclus but are not dated closely. Comparison of their spatial extent with well-dated moraines in the Chilean Lakes Region suggests that they may mark advances culminating at ca. 14000 yr BP, ca. 20000 yr BP and earlier.     

Impact of post-mixing chemical reactions on the major ion chemistry of bulk meltwaters draining the haut glacier d'arolla,valais, Switzerland

Until now, alpine glacial meltwaters have been assumed to consist of two components, dilute quickflow and concentrated delayed flow, the mixing of which has been regarded as chemically conservative for the major dissolved ions and electrical conductivity. Dye tracing results suggest that this two-component model adequately represents the sub-glacial hydrology of the Haut Glacier d'Arolla, Switzerland. However, laboratory dissolution experiments in which various concentrations of glacial rock flour are placed in dilute solutions show that this rock flour is highly reactive and suggest that bulk meltwaters may acquire significant amounts of solute through rapid chemical reactions with suspended sediment which occur after mixing of the two components. This view is supported by detailed analysis of variations in the hydrochemistry of meltwaters draining from the Haut Glacier d'Arolla over three diurnal cycles during the 1989 melt season. Variations in the composition of bulk meltwaters are controlled by two main factors: dilution of the delayed flow component by quickflow, and the extent of post-mixing reactions. The latter depends on the suspended sediment concentration in bulk meltwaters and on the duration of contact between these waters and suspended sediment. Seasonal changes in the magnitude of these factors result in changes in the character and causes of diurnal variations in meltwater chemistry. In June, these variations reflect discharge-related variations in residence time within a distributed subglacial drainage system; in July, when a channelized drainage system exists beneath the lower glacier, they primarily reflect the dilution of delayed flow by quickflow; in August, when suspended sediment concentrations are particularly high, they reflect varying degrees of solute acquisition by post-mixing reactions with suspended sediment that take place in arterial channels at the glacier bed.