Annual Mass Balance of Blue Glacier, USA: 1955–97

Mass changes of Blue Glacier, USA are calculated from topographic maps made from vertical aerial photography in late summer of 1939, 1952, 1957, and 1987, along with laser altimetry flown in June 1996. Changes in elevation between maps were adjusted for seasonal variations in the snow cover, and to account for the ablation between the date of photography and 1 October. Topography obtained from the laser altimetry was adjusted for snow thickness and glacier motion to estimate topography of 1 October 1995. The mass of Blue Glacier has changed less than 7 m (water equivalent) during this 56 year period which is minor compared with other glaciers in the region and elsewhere in the world. Glacier-average annual mass balances, beginning in 1956, have been calculated either from stake measurements and probing of late-season snow, or from a regression analysis using late-season measurements of the equilibrium line altitude. A comparison with the changes derived from surface maps shows values obtained from field measurements are too positive by about 0.4 m a^?1 , indicating that considerable caution is needed when interpreting time series of mass balance. Two alternative time series of mass balance consistent with the long-term mass changes are created by making simple adjustments: (1) a single constant is subtracted from each value so that the series is consistent with the 1957–95 mass change; (2) one constant is subtracted from each value over 1957–87 and another is subtracted from each value over 1987-95 so that the series is consistent with both the 1957–87 and 1987–95 mass changes. The mass balance of Blue Glacier was generally positive until the mid-1970s and negative since. The fluctuations of mass balance closely resemble those of snowfall on the glacier as estimated from the joint distribution of temperature and precipitation. The climate in western Washington was cooler and wetter during the decade before the mid-1970s, but the trend since has been towards warmer and drier conditions.     

Mass Balance Reconstruction Since 1963 and Mass Balance Model for East Rathong Glacier,Eastern Himalaya,Using Remote Sensing Methods

In this study mass balance, accumulation, ablation, runoff and temperature lapse rate for the East Rathong glacier are estimated for the time period 1963–2011 using remote sensing methods and climate data. A mass balance model is proposed for the glacier that computes mass balance as difference of volumes of consecutive years. Volume estimates of glacier are based on application of volume–area scaling law to glacier area computed from satellite images. It is observed that the glacier is summer‐accumulation type. Time series analysis is applied to the annual mass balance series. The annual mass balance of the glacier is showing a statistically significant negative trend. It is also showing a statistically significant shift in the year 1985. Change in the mean of mass balance before and after the shift year is 0.19 m w.e. Cumulative mass balance suggests that the glacier has lost ～11 m w.e. or 0.047 km³ during the last 48 years.     

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.     

Snow,runoff, and mass balance modeling for the entire Mittivakkat Glacier (1998–2006), Ammassalik Island,SE Greenland

Geografisk Tidsskrift, Danish Journal of Geography 108(1):121–136, 2008

SnowModel, a physically-based snow evolution modeling system that includes four submodels—MicroMet, EnBal, SnowPack, and SnowTran-3D—was used to simulate eight full-year (1998/99 through 2005/06) evolutions of snow accumulation, blowing snow sublimation, evaporation, snow and ice surface melt, runoff, and mass changes on the entire Mittivakkat Glacier (31 km²) in southeast Greenland. Meteorological observations from two meteorological stations inside the glacier catchment were used as model input, and glaciological mass balance observations were used for model calibration (1998/99 through 2001/02) and validation (2002/03 through 2005/06) of winter snow simulations. As confirmed by observations, the spatially modeled end-of-winter snow water equivalent (SWE) accumulation increased with elevation up to 700–800 m a.s.l. in response to elevation, topography, and dominating wind direction, and maximum snow deposition occurred on the lee side of the ridge east and south of the glacier. Simulated end-of-summer cumulative runoff decreased with elevation and minimum runoff occurred on the shadowed side of the ridge east and south of the glacier. The modeled test period averaged annual mass balance was 65 mm w. eq. y^?1 or ～8% more than the observed. For the simulation period, the glacier net mass balance varies from -199 to -1,834 mm w.eq. y^?1, averaging -900 (±470) mm w.eq.y^?1. The glacier averaged annual modeled precipitation ranged from 1,299 to 1,613 mm w.eq. y^?1, evaporation and sublimation from 206 to 289 mm w.eq., and runoff from 1,531 to 2,869 mm w.eq. y^?1. The model simulated Mittivakkat Glacier net loss of900 mm w.eq. y^?1 contributes approximately 42% to the average simulated runoff of 2,140 mm w.eq. y^?1, indicating a mean specific runoff of 67.8 l s^?1 km^?2.     

珠穆朗玛峰北坡东绒布冰川成冰作用的新认识

冰川成冰作用的研究对于选择冰芯钻取点具有重要的科学意义。前人对珠穆朗玛峰北坡冰川成冰作用的研究,由于缺少高海拔区域的实测资料而具有一定的局限性。文章通过1998年东绒布冰川垭口处(6 500 m a. s. l.)11 m冰芯和海拔6 450 m处20 m冰芯剖面的成冰作用过程研究,认识到由于水、热条件的逐年波动,冰川成冰作用也处于变化之中。珠穆朗玛峰北坡东绒布冰川高海拔区域,在一定的水、热条件下(如气温较低和降水量较大等),再冻结-重结晶作用依然占主导地位,该成冰作用至少在垭口部位是有分布的。而一般在气温较高或降水量较少等条件下,冰川的成冰作用则以冷渗浸-重结晶作用为主。     

A Mass Balance Model that Uses Low-altitude Meteorological Observations and the Area–Altitude Distribution of a Glacier

A glacier mass balance model that requires only low-altitude precipitation and temperature observations and the glacier's areaaltitude distribution is presented as an alternative to direct field measurements. Input to the model for South Cascade Glacier are daily weather observations at stations 30–60 km from the glacier and at altitudes 1300 to 1500 m lower than the glacier. The model relies on the internal consistency of mass balance variables that are generated by simulation using the low-altitude weather data. The daily values of such balance variables as snowline altitude, zero balance altitude, glacier balance, balance flux and the accumulation area ratio are correlated throughout the ablation season using two-degree polynomial regressions to obtain the lowest fitting error. When the minimum average error (or maximum R ²) is attained, the generated balances and other variables are considered to be real. A simplex optimization technique is used to determine the optimal coefficient values that are used in algorithms to convert meteorological observations to snow accumulation and snow and ice ablation. The independently produced simulation results for the 1959–1996 period are compared with balances measured at the glacier. The agreement between annual balances for individual years is fair and between long-term volume changes measured by the geodetic method is excellent.     

Glacier balance trends in the Kongsfjorden area, western Spitsbergen, Svalbard, in relation to the climate

For the last thirty years, the mean net balance of two glaciers, Austre Brøggerbreen and Midre Lovénbreen, has been -0.43 and -0.34 m of water equivalent (w.e.). respectively. The mean net balance of Kongsvegen, a tidewater glacier that has been measured since 1987, is 0.11 m w.e. The negative balances of the two first glaciers are driven by the increase in atmospheric temperature which occurred at the end of the Little Ice Age at the beginning of the century. The positive balance of Kongsvegen is due to its higher elevation and larger accumulation area. There is no significant trend in the net balances and no increase of the melting has been detected during the last thirty years.
A correlation coefficient of R = 0.83 has been obtained between the net balance of Lovénbreen and the winter precipitation, together with the summer temperature recorded at the neighbouring station of Ny-Ålesund since 1969. With 14 years of data, the correlation coefficient between the net balance and climatic parameters does not increase consistently by introducing any radiation component, but the coefficient correlation between the summer balance of Austre Brøggerbreen and summer temperature increases from 0.68 to 0.77 when introducing global and long-wave radiation for July and August. Weather conditions and the frequency of their changes influence the balance between global and long-wave radiation and changes in albedo values.     

南极普里兹湾临近海域夏季纽鳃樽对浮游植物的摄食研究

于 1 998年 1 2月至 1 999年 1月南极夏季 ,对南大洋普里兹湾临近海域主要被囊类纽鳃樽的数量密度分布进行了现场调查 ,同时于 - 3站对纽鳃樽对浮游植物的摄食率利用肠道色索法和颗粒递减法进行了现场研究。调查结果表明 ,纽鳃樽主要分布于调查海区的浮冰区北部边缘及其以北的开阔水域。在密集区其数量密度高达 2 795ind..1 0 0 0 m- 3,浮冰区几乎没有发现。 - 3站现场摄食实验结果显示 ,纽鳃樽个体肠道色素含量变化范围为 0 .1 4～ 1 .2 7μg.ind.- 1,平均为0 .98μg.ind.- 1。肠道色素法测得的纽鳃樽对浮游植物的摄食率为 7.9μg.ind.- 1d- 1,滤水率为2 81 ind.- 1d- 1。颗粒递减法测得纽鳃樽滤水率为 1 5.3± 4.61 ind.- 1d- 1,比肠道色素法所得结果偏低。虽然由此推算纽鳃樽群体的日摄食量只占浮游植物现存量的 0 .8% ,但是对于初级生产力却有一定的摄食压力 ( 72 .2 % )。     

Applicability of an ultra-long-range terrestrial laser scanner to monitor the mass balance of Muz Taw Glacier, Sawir Mountains, China

Glacier mass balance is a key component of glacier monitoring programs. Information on the mass balance of Sawir Mountains is poor due to a dearth of in-situ measurements. This paper introduces the applicability of an ultra-long-range terrestrial laser scanner(TLS) to monitor the mass balance of Muz Taw Glacier, Sawir Mountains, China. The Riegl VZ?-6000 TLS is exceptionally well-suited for measuring snowy and icy terrain. Here, we use TLS to create repeated high spatiotemporal resolution DEMs, focusing on the annual mass balance(June 2, 2015 to July 25, 2016). According to TLS-derived high spatial resolution point clouds, the front variation(glacier retreat) of Muz Taw Glacier was 9.3 m. The mean geodetic elevation change was 4.55 m at the ablation area. By comparing with glaciological measurements, the glaciological elevation change of individual stakes and the TLS-derived geodetic elevation change of corresponding points matched closely, and the calculated balance was-3.864±0.378 m w.e.. This data indicates that TLS provides accurate results and is therefore suitable to monitor mass balance evolution of Muz Taw Glacier.     

MODELLING LONG‐TERM SUMMER AND WINTER BALANCES AND THE CLIMATE SENSITIVITY OF STORBREEN,NORWAY

Measurements of winter balance (b_w) and summer balance (b_s) have been carried out at Storbreen since 1949. Here we apply a simple mass balance model to study the climate sensitivity and to reconstruct the mass balance series priorto 1949. The model is calibrated and validated with data from an automatic weather station (AWS) operating in the ablation zone of Storbreen since 2001. Regression analysis revealed that b_w was best modelled using precipitation data southwest of the glacier. Results from the model compared well with reported mass balance values for the period 1949–2006, obtained correlations (r) for b_w and b_s varied between 0.83 and 0.87 depending on model set up. Reconstruction of the mass balance series for the period 1924/1925–1948/1949 suggested a cumulative mass deficit of c. 30 m w.e. mainly due to highly negative summer balances, but also lower b_wthan the average for 1949–2006. Calculated change in specific mass balance for a ±1°C change in air temperature was ±0.55 m w.e., whereas a ±10 % increase in precipitation represented a change of ±0.20 m w.e. Model results further indicated that for a 2°C warming, the ablation season will be extended by c. 30 days and that the period of ice melt at the AWS location will increase from c. 40 to c. 80 days.     

Glacier Retreat, Mass-Balance and Thinning: Sermilik Glacier, South Greenland

This study documents thinning and retreat of the South Greenland ice margin and discusses possible reasons in the light of mass‐balance and change of dynamic conditions. Analyses of satellite images have shown that the glacier tongue of Sermilik glacier disintegrated within the past 15 years. Furthermore, the observed thinning close to the Sermilik glacier front was as much as 120 m water equivalent during this period. This figure was derived by comparing surface elevation data from a digital elevation model (1985) and laser altimeter measurements from the year 2000, showing surface elevation changes along a flow line of Sermilik glacier. Mass‐balance data from in situ measurements performed at a centre flow line of the glacier are presented. These data are compared to results from remote sensing analyses of the study area. Net ablation reconstruction over the last 41 years from positive‐degree‐day modelling, at various locations along the Sermilik glacier massbalance transect, shows an increase during the past decades. These analyses indicate that only 55% of the total thinning in this area can be explained by mass‐balance changes. The remaining 45% of the thinning is attributed to changes in the dynamic behaviour of the glacier, such as an increase of creep towards the end of the twentieth century. The significant thinning along the Qagssimiut lobe can also be explained as a combination of mass‐balance changes and changes in ice dynamic behaviour.     

Mass Balance Methods on Kongsvegen, Svalbard

On the glacier Kongsvegen (102 km²) in northwest Spitsbergen, Svalbard, traditional mass balance measurements by stake readings and snow surveying have been conducted annually since 1987. In addition, repeated global positioning system (GPS) profiling, shallow core analysis and ground-penetrating radar (GPR) surveying have been applied. The purpose of this paper is to evaluate the input from the different methods, especially the GPS profiling, using the results from the traditional direct method as a reference. The annual flow rate on Kongsvegen is low (2 ? 3 m a^?1), and the emergence velocity is almost negligible. Thus the geometry changes of the glacier, i.e. the change in altitude per distance from the head of the glacier, should reflect the change in net balance of the glacier. The mean annual altitude change from the longitudinal, centreline GPS profiles was compared to the direct stake readings and showed a very good agreement. On Kongsvegen the measured actual ice flux is so low that the mass transfer down-glacier at the mean equlibrium line altitude is less than 10% of what is needed to maintain steady-state geometry. This is clearly shown in the changing altitude profiles. GPS profiling can be used on large glaciers in remote areas to monitor geometry changes, ice flow and net mass balance changes. However, it requires that the centreline profile changes are representative for the area/altitude intervals, i.e. that the accumulation and ablation pattern is evenly distributed. For this purpose the GPR surveying quickly gave the snow distribution variability over long distances. Shallow cores drilled in different altitudes in the accumulation area were analysed to detect radioactive reference layers from the fallout after the Chernobyl accident in 1986, and showed very good agreement to the direct measured net balance. Thus older reference horizons from bomb tests in 1962 could be used to extend the net balance series backwards.     

Accumulation in Svalbard glaciers deduced from ice cores with nuclear tests and Chernobyl reference layers

Mean net annual balance and the related spatio-temporal variations have been determined on the basis of well-dated artificial layers in shallow ice cores (Chernobyl, 1986, and atmospheric thermonuclear tests, mainly in 1961-62 in Novaya Zemlya). Seventy ice cores from 13 Svalbard glaciers have been analysed. On each glacier, in its accumulation area and at the highest elevation, one ice core was recovered down to about 40 m and sampled for radioactivity measurements to determine the 1986 and 1962-63 layer (1954 was the initial date of the nuclear tests). For each glacier, at least five complementary ice cores from the accumulation area were analysed to determine the Chernobyl reference layer. Six ice cores exhibit both the Chernobyl and nuclear tests layers and are of special interest in this study.
This work provides new data on the deposition rates of natural and artificial radioisotopes. Using ice cores samples from the Arctic glaciers, even with superimposed ice accumulation, it is possible to distinguish between the Chernobyl and the nuclear tests fallouts. This work also shows that the mean annual net balance did not significantly change for at least five ice core locations in the Svalbard glaciers for the two periods extending from 1963 to 1986 to the recent date of drilling.     

MODIS Derived Equilibrium Line Altitude Estimates for Purogangri Ice Cap,Tibetan Plateau,and their Relation to Climatic Predictors (2001–2012)

The variation of the equilibrium line altitude can be used as an indicator for glacier mass balance variability. Snow lines at the end of the ablation period are suitable proxies for the annual equilibrium line altitude on glaciers. We investigate snow lines at Purogangri ice cap on the central Plateau in order to study the interannual variability of glacier mass balance. Datasets of the daily Moderate Resolution Imaging Spectroradiometer snow product MOD10A1 were used to infer transient snow line variability during 2001–2012 and to derive regional‐scale, annual equilibrium line altitude. The Moderate Resolution Imaging Spectroradiometer snow albedo embedded within the snow product was compared with high‐resolution Landsat imagery. An albedo threshold was established to differentiate between ice and snow and the 13th percentile of the altitudes of snow‐covered pixels was chosen to represent the snow line altitude. The second maximum of the snow line altitudes in the ablation period was taken as a proxy for the annual equilibrium line altitude. A linear correlation analysis was carried out (1) between interannual variability of the equilibrium line altitude at Purogangri ice cap and various climate elements derived from the High Asia Reanalysis, and (2) between interannual variability of the equilibrium line altitude and the circulation indices North Atlantic Oscillation and Indian Summer Monsoon. Results suggest that air temperature and meridional wind speed above ground in July, as well as the lower tropospheric zonal wind in June and August play a crucial role in the development of the annual equilibrium line altitude.     

QUANTIFYING UNCERTAINTY IN USING MULTIPLE DATASETS TO DETERMINE SPATIOTEMPORAL ICE MASS LOSS OVER 101 YEARS AT KÅRSAGLACIÄREN,SUB‐ARCTIC SWEDEN

Glacier mass balance and mass balance gradient are fundamentally affected by changes in glacier 3D geometry. Few studies have quantified changing mountain glacier 3D geometry, not least because of a dearth of suitable spatiotemporally distributed topographical information. Additionally, there can be significant uncertainty in georeferencing of historical data and subsequent calculations of the difference between successive surveys. This study presents multiple 3D glacier reconstructions and the associated mass balance response of Kårsaglaciären, which is a 0.89 ± 0.01 km² mountain glacier in sub‐arctic Sweden. Reconstructions spanning 101 years were enabled by historical map digitisation and contemporary elevation and thickness surveys. By considering displacements between digitised maps via the identification of common tie‐points, uncertainty in both vertical and horizontal planes were estimated. Results demonstrate a long‐term trend of negative mass balance with an increase in mean elevation, total glacier retreat (1909–2008) of 1311 ± 12 m, and for the period 1926–2010 a volume decrease of 1.0 ± 0.3 × 10^–3 km³ yr^–1. Synthesising measurements of the glaciers’ past 3D geometry and ice thickness with theoretically calculated basal stress profiles explains the present thermal regime. The glacier is identified as being disproportionately fast in its rate of mass loss and relative to area, is the fastest retreating glacier in Sweden. Our long‐term dataset of glacier 3D geometry changes will be useful for testing models of the evolution of glacier characteristics and behaviour, and ultimately for improving predictions of meltwater production with climate change.     

Evidencing a large body of ice in a rock glacier,Vanoise Massif,Northern French Alps

The Sachette rock glacier is an active rock glacier located between 2660 and 2480 m a.s.l. in the Vanoise Massif, Northern French Alps (45° 29′ N, 6° 52′ E). In order to characterize its status as permafrost feature, shallow ground temperatures were monitored and the surface velocity measured by photogrammetry. The rock glacier exhibits near‐surface thermal regimes suggesting permafrost occurrence and also displays significant surface horizontal displacements (0.6–1.3 ± 0.6 m yr^–1). In order to investigate its internal structure, a ground‐penetrating radar (GPR) survey was performed. Four constant‐offset GPR profiles were performed and analyzed to reconstruct the stratigraphy and model the radar wave velocity in two dimensions. Integration of the morphology, the velocity models and the stratigraphy revealed, in the upper half of the rock glacier, the good correspondence between widespread high radar wave velocities (>0.15–0.16 m ns^–1) and strongly concave reflector structures. High radar wave velocity (0.165–0.170 m ns^–1) is confirmed with the analysis of two punctual common mid‐point measurements in areas of exposed shallow pure ice. These evidences point towards the existence of a large buried body of ice in the upper part of the rock glacier. The rock glacier was interpreted to result from the former advance and decay of a glacier onto pre‐existing deposits, and from subsequent creep of the whole assemblage. Our study of the Sachette rock glacier thus highlights the rock glacier as a transitional landform involving the incorporation and preservation of glacier ice in permafrost environments with subsequent evolution arising from periglacial processes.     

中国西部大陆性冰川与海洋性冰川物质平衡变化及其对气候响应——以乌源1号冰川和帕隆94号冰川为例

为认识全球变暖背景下中国西部大陆性冰川与海洋性冰川物质平衡变化及其对气候响应,本研究以天山乌鲁木齐河源1号冰川和藏东南帕隆94号冰川为例,结合大西沟与察隅站气象资料,对1980 — 2015年两条冰川的物质平衡变化特征及差异进行了分析。结果表明：36 a来乌源1号冰川与帕隆94号冰川物质平衡总体上均呈下降趋势,累积物质平衡达-17102与-8159 mm w.e.,相当于冰川厚度减薄19与9.01 m,且分别于1996、2004年左右发生突变。同期两条冰川所处区域年均温呈显著上升趋势,而降水量却表现出不同的变化态势;二者年内气温分配相仿,但降水分配差异较大。初步分析认为气温上升是导致乌源1号冰川与帕隆94号冰川物质亏损的主要原因,冰川区气温和降水变化幅度的差异和地性因子（坡度、冰川面积）的不同使得乌源1号冰川对气候变化响应的敏感性高于帕隆94号冰川,由于目前海洋性冰川物质平衡监测时段相对较短,为深入研究中国西部冰川物质平衡变化及过程仍需加强对冰川的持续观测。     

Decadal‐Scale Changes of the Ödenwinkelkees,Central Austria,Suggest Increasing Control of Topography and Evolution Towards Steady State

Small mountain glaciers have short mass balance response times to climate change and are consequently very important for short‐term contributions to sea level. However, a distinct research and knowledge gap exists between (1) wider regional studies that produce overview patterns and trends in glacier changes, and (2) in situ local scale studies that emphasise spatial heterogeneity and complexity in glacier responses to climate. This study of a small glacier in central Austria presents a spatiotemporally detailed analysis of changes in glacier geometry and changes in glaciological behaviour. It integrates geomorphological surveys, historical maps, aerial photographs, airborne LiDAR data, ground‐based differential global positioning surveys and Ground Penetrating Radar surveys to produce three‐dimensional glacier geometry at 13 time increments spanning from 1850 to 2013. Glacier length, area and volume parameters all generally showed reductions with time. The glacier equilibrium line altitude increased by 90 m between 1850 and 2008. Calculations of the mean bed shear stress rapidly approaching less than 100 kPA, of the volume–area ratio fast approaching 1.458, and comparison of the geometric reconstructions with a 1D theoretical model could together be interpreted to suggest evolution of the glacier geometry towards steady state. If the present linear trend in declining ice volume continues, then the Ödenwinkelkees will disappear by the year 2040, but we conceptualise that non‐linear effects of bed overdeepenings on ice dynamics, of supraglacial debris cover on the surface energy balance, and of local topographically driven controls, namely wind‐redistributed snow deposition, avalanching and solar shading, will become proportionally more important factors in the glacier net balance.     

Mass balance and area changes of four High Arctic plateau ice caps, 1959–2002

Abstract Small, stagnating ice caps at high latitudes are particularly sensitive to climatic fluctuations, especially with regard to changes in ablation season temperature. We conducted mass balance measurements and GPS area surveys on four small High Arctic plateau ice caps from 1999–2002. We compared these measurements with topographic maps and aerial photography from 1959, and with previously published data. Net mass balance (b_n) of Murray Ice Cap was ?0.49 (1999), ?0.29 (2000), ?0.47 (2001), and ?0.29 (2002), all in meters of water equivalent (m w.eq.). The mass balance of nearby Simmons Ice Cap was also negative in 2000 (b_n=?0.40 m w.eq.) and in 2001 (b_n=?0.52 m w.eq.). All four ice caps experienced substantial marginal recession and area reductions of between 30 and 47% since 1959. Overall, these icecaps lost considerable mass since at least 1959, except for a period between the mid‐1960s and mid‐1970s characterized regionally by reduced summer melt, positive mass balance, and ice cap advance. The regional equilibrium line altitude (ELA) is located, on average, above the summits of the ice caps, indicating that they are remnants of past climatic conditions and out of equilibrium with present climate. The ice caps reached a Holocene maximum and were several times larger during the Little Ice Age (LIA) and their current recession reflects an adjustment to post‐LIA climatic conditions. At current downwasting rates the ice masses on the Hazen Plateau will completely disappear by, or soon after, the mid‐21st century.     

Internal Structure and Permafrost Characteristics of the Rock Glaciers of Southern Carpathians (Romania) Assessed by Geoelectrical Soundings and Thermal Monitoring

Six rock glaciers in the Southern Carpathians have been investigated by means of geoelectrical soundings in order to detect their internal stratigraphy and the existence of frozen sediments. In the case of three relict rock glaciers, the electrical resistivity measurements indicated a typical internal structure. Low resistivity values (<10 kΩm) which are typical of unfrozen fine‐grained materials were obtained, but high resistivity values (25–240 kΩm) measured in the Pietroasa, Ie?u and Pietrele rock glaciers denote the presence of sediments cemented by interstitial ice and ice lenses. Based on the moderate resistivity values, the ice content is probably low to medium in the upper portion of these rock glaciers, that is, above 2040 m. At two sites (Pietroasa and V?iuga rock glaciers), ground surface temperature (GST) evolution was monitored using digital dataloggers. Mean annual ground surface temperature and GST regime throughout the winter were extracted from the recordings and confirmed the probability of permafrost occurrence in Pietroasa rock glacier. In the Ie?u and Pietrele rock glaciers, measurements of bottom temperatures of the winter snow cover were performed in March 2012. Considering the thick active layer, the reduced ice content and the presence of scarce vegetation on their surface it could be assumed that the permafrost exists in marginal conditions in the Southern Carpathians. The ground ice in permafrost is produced by the groundwater freezing or by snow banks buried by coarse angular boulders following large rockfalls.