Spitsbergen Glaciers Research Articles

Comparison of Hydrothermal Structure of Two Glaciers in Spitsbergen and Tian Shan Based on Radio-Echo Sounding Data

Comparison of Hydrothermal Structure of Two Glaciers in Spitsbergen and Tian Shan Based on Radio-Echo Sounding Data

Seasonal dynamics of snow ablation on selected glaciers in central Spitsbergen derived from Sentinel-2 satellite images

AbstractThe dynamics of seasonal snow ablation on six glaciers in central Spitsbergen (Dicksonland) were assessed by examining a set of Sentinel-2 satellite images covering the summer ablation season for the period 2016–19. All glaciers lost 80% or more of their surface snow cover during the studied ablation seasons. This bolsters the recently observed trend of local glacier thinning, even at higher altitudes. Snow ablation dynamics are highly dependent on the glaciers altitudes, their position relative to the prevailing wind direction and the exposure to insolation. The accumulation areas of the studied glaciers were delimited based on the overlap of the minimum extent of snow-covered areas in the four consecutive studied summer seasons. The high temporal and spatial resolutions of available images enabled a detailed description of the seasonal snow ablation dynamics. Moreover, an estimate of the average number of days with below threshold glacier snow cover was made. This study contributes to our understanding of recent processes and might further support the modelling of glacier melt and subsequent runoff.

Quality Assessment and Glaciological Applications of Digital Elevation Models Derived from Space-Borne and Aerial Images over Two Tidewater Glaciers of Southern Spitsbergen

In this study, we assess the accuracy and precision of digital elevation models (DEM) retrieved from aerial photographs taken in 2011 and from Very High Resolution satellite images (WorldView-2 and Pléiades) from the period 2012–2017. Additionally, the accuracy of the freely available Strip product of ArcticDEM was verified. We use the DEMs to characterize geometry changes over Hansbreen and Hornbreen, two tidewater glaciers in southern Spitsbergen, Svalbard. The satellite-based DEMs from WorldView-2 and Pléiades stereo pairs were processed using the Rational Function Model (RFM) without and with one ground control point. The elevation quality of the DEMs over glacierized areas was validated with in situ data: static differential GPS survey of mass balance stakes and GPS kinematic data acquired during ground penetrating radar survey. Results demonstrate the usefulness of the analyzed sources of DEMs for estimation of the total geodetic mass balance of the Svalbard glaciers. DEM accuracy is sufficient to investigate glacier surface elevation changes above 1 m. Strips from the ArcticDEM are generally precise, but some of them showed gross errors and need to be handled with caution. The surface of Hansbreen and Hornbreen has been lowering in recent years. The average annual elevation changes for Hansbreen were more negative in the period 2015–2017 (−2.4 m a−1) than in the period 2011–2015 (−1.7 m a−1). The average annual elevation changes over the studied area of Hornbreen for the period 2012–2017 amounted to −1.6 m a−1. The geodetic mass balance for Hansbreen was more negative than the climatic mass balance estimated using the mass budget method, probably due to underestimation of the ice discharge. From 2011 to 2017, Hansbreen lost on average over 1% of its volume each year. Such a high rate of relative loss illustrates how fast these glaciers are responding to climate change.

Glaciers on Svalbard survived the Holocene thermal optimum

About 60% of Svalbard is covered by glaciers today, but many of these glaciers were much reduced in size or gone in the Early Holocene. High resolution modeling of the glacial isostatic rebound reveals that the largest glaciers in Nordaustlandet and eastern Spitsbergen survived the Early Holocene warming, while the smaller, more peripheral glaciers, especially in the northwest, started to form about 5,500 years ago, and reached 3/4 of their current size about 600 years ago. Relative sea level has been rising during the last few millennia in the north and western parts of Spitsbergen, while land still emerges in the remaining part of Svalbard. Here we show that this sea level rise in the northwest is caused by the regrowth of glaciers in the Mid- to Late Holocene that slowed down, and even reversed, the post-glacial isostatic uplift and caused the crust to subside over large areas of Spitsbergen.

Submarine landform assemblages and sedimentary processes in front of Spitsbergen tidewater glaciers

New swath-bathymetric data from the inner parts of the three Svalbard fjords Ymerbukta, Trygghamna, and Magdalenefjorden reveal the landform assemblages deposited in front of tidewater glaciers in west and northwest Spitsbergen. Overridden moraines in Ymerbukta, a tributary of Isfjorden in central west Spitsbergen, record several re-advances of the Esmarkbreen glacier at the head of the fjord after deglaciation, and glacial lineations formed in seafloor sediments are indicative of fast ice advance during one of these events. A terminal moraine and associated debris lobe mark the maximum ice extent during the Holocene, which, implied by the presence of crevasse-squeeze ridges, is likely related to a surge of Esmarkbreen. Several De Geer moraines provide evidence for subsequent slow and step-wise retreat. In the adjacent Trygghamna and in Magdalenefjorden in northwest Spitsbergen the landforms are similar but the absence of overridden moraines and glacial lineations shows that the glaciers probably only re-advanced once during the Holocene and that ice flow was relatively slow. Terminal moraines and associated debris lobes mark the maximum extent of these advances and formed during the Little Ice Age (LIA). In Magdalenefjorden the relatively small size of the debris lobe suggests that the ice margin was at its maximum position for only a short period of time, or that sediment availability was restricted during the LIA advance. Similar to Esmarkbreen the retreat phase of the glaciers in Trygghamna and Magdalenefjorden was also characterised by periods of still-stand or small re-advances, although the comparatively small number of De Geer moraines in all three fjords shows that these landforms probably formed much less frequently than previously thought. Sub-bottom profiler data, four sediment cores and six radiocarbon dates from Magdalenefjorden further provide information about the Holocene sedimentary environments in a northwest Spitsbergen fjord. The main source of sediment is glacial meltwater entering the fjord from the surrounding coastline, which has led to the accumulation of thick sequences of fine-grained mud. Stratified and laminated muds record glacier-proximal conditions, probably related to a LIA re-advance of Waggonwaybreen around 300calaBP, where the interplay of a range of glacimarine processes led to the formation of partially rhythmic couplets of one coarser and one finer layer, accumulated at a rate of around 3cma−1. Multiple sandy layers intercalated with the glacimarine mud provide evidence for the occurrence of gravitational mass-flow events like turbidity currents. In ice-distal settings, massive to weakly stratified, occasionally bioturbated mud accumulated at a lower rate of 0.04–0.49cma−1. Occasional clasts and diamictic layers show that the depositional environment in Magdalenefjorden is also influenced by sedimentation from icebergs and sea ice, but the ubiquitous glacimarine mud underscores the predominance of meltwater-related sedimentation in the fjord.

Snow deposition patterns on southern Spitsbergen glaciers, Svalbard, in relation to recent meteorological conditions and local topography

ABSTRACTWe present a detailed study on snow cover on six different glaciers in southern Spitsbergen, Svalbard: Amundsenisen, Flatbreen, Hansbreen, Nannbreen, Storbreen and Werenskioldbreen. Fieldwork was carried out in April–May 2013, at the end of the accumulation season, to determine large-scale spatial distribution patterns of snow cover on glaciers surrounding the Hornsund Fjord. Snow depth was measured using an 800 MHz ground-penetrating radar (GPR). In addition, the structure of the snowpack was determined by digging snow pits and collecting snow cores from different glacier facies. These samples were subsequently analysed against circulation types and meteorological data from selected sites. In particular, snow patterns were compared against rain-on-snow events. The mean snow depth measures ranged from 1.90 m (Werenskioldbreen) to 3.80 m (Amundsenisen), whereas the accumulation gradient ranged from 15 cm 100 m−1 (Storbreen) to 74 cm 100 m−1 (Nannbreen). These results followed previous observations, suggesting a decrease in snow accumulation from coastal areas towards the island’s interior. The estimated snow water equivalent values were lower than those measured in the 1990s and during 2010 (Hansbreen: c. −48%), with the exception of Amundsenisen (c. +17%). The relatively high densities found in the snowpack did not compensate for the shallow snow depths measured, which can be ascribed to low precipitation totals and an increased frequency of rain events during the winter months.

Modeling the Controls on the Front Position of a Tidewater Glacier in Svalbard

Calving is an important mass-loss process at ice sheet and marine-terminating glacier margins, but identifying and quantifying its principal driving mechanisms remains challenging. Hansbreen is a grounded tidewater glacier in southern Spitsbergen, Svalbard, with a rich history of field and remote sensing observations. The available data make this glacier suitable for evaluating mechanisms and controls on calving, some of which are considered in this paper. We use a full-Stokes thermomechanical 2D flow model (Elmer/Ice), paired with a crevasse-depth calving criterion, to estimate Hansbreen’s front position at a weekly time resolution. The basal sliding coefficient is re-calibrated every four weeks by solving an inverse model. We investigate the possible role of backpressure at the front (a function of ice melange concentration) and the depth of water filling crevasses by examining the model’s ability to reproduce the observed seasonal cycles of terminus advance and retreat. Our results suggest that the ice-melange pressure plays an important role in the seasonal advance and retreat of the ice front, and that the crevasse-depth calving criterion, when driven by modelled surface meltwater, closely replicates observed variations in terminus position. These results suggest that tidewater glacier behavior is influenced by both oceanic and atmospheric processes, and that neither of them should be ignored.

Fifty years of geophysical researches of glaciers in Institute of Geography, the Russian Academy of Sciences, 1966–2016

In 1967‑2015, Institute of Geography of the USSR/Russian Academy of Sciences together with other organizations carried out field expeditions in different areas of mountain and polar glaciations in many regions: the Polar Urals, Caucasus, Pamir, Zailiysky and Jungar Alatau, Tien‑Shan, Pamir‑Alai, the Kamchatka Peninsula, the Pyrenees, the Arctic – Spitsbergen, Novaya Zemlya, Franz Josef and Severnaya Zemlya, and Antarctica – on the ice flow B, and in the sub‑Antarctic – Islands King George, Galindez, and Livingston. The gravimetric and ground and aerial radar observations were made in these expeditions. About 300 glaciers of different morphological types and sizes with cold, subpolar and temperate thermal regime were studied. Basic results of these studies are the following: (1) the new data on the ice thicknesses, ice volumes, subglacial relief, internal structure, and thermal state of the glaciers were obtained; (2) the two‑layered (polythermal) glaciers consisting of the upper layer of cold ice and the lower layer of temperate water‑filled ice had been revealed in Svalbard for the first time; spatial distribution of cold, polythermal and temperate glaciers had been determined; (3) the evidences were obtained that measured changes in thickness of the upper cold ice layer in polythermal glaciers can be used to estimate the long‑period variations of regional climates and serve as regional paleothermometers; (4) methods for estimating the water content in temperate and polythermal glaciers from the RES data were developed; and its space‑time variations in temperate ices of the Svaldbald glaciers were estimated since even small water content inside of them can noticeably change their dynamic behavior; (5) methods for estimating the ice volume within glaciers in large regions of mountain and polar glaciations had been created; the ice storages were estimated in Svalbard, Franz Josef Land, Dzhungrsky Alatau, the Great Caucasus, and Mt. Elbrus; (6) detailed data on the ice thicknesses and the subglacial relief had been obtained for 40 glaciers in framework of different national and international programs and projects; the data can be used to solve a wide range of practical and theoretical problems, including numerical modeling. These studies demonstrated the following: (1) the use of monopulse radars VIRL‑6 and VIRL‑7 of decameter range (the central frequency is 20 MHz) with digital recording of the radar and GPS data is quite efficient for ground‑based and airborne (from helicopters) radio‑echo sounding of mountain and polar glaciers with their ice thicknesses up to 500–600 m; (2) it was found that thicknesses of glaciers in the Caucasus and Tien Shan can reach 330–430 m, while in regions of mountain, ice‑sheet and transitional glaciation on the Spitsbergen Archipelago – 300, 560 and 600 m, respectively, on the ice caps of the Franz‑Josef Land and Severnaya Zemlya – 450 and 813 m, and on King George and Livingston Islands (Sub‑Antarctica) – 330 and 500 m; (3) large parts of ice caps and outlet glaciers in Svalbard, Franz Josef Land, Severnaya Zemlya which beds were located below the sea level were found. Precisely these parts can be undergone quick shortening due to climate warming, and, thus, cause formation of icebergs making threats for ships and gas‑oil marine platforms in the Barents and Kara seas; (4) data of the measurements made possible to calculate volumes of a number of investigated glaciers and ice caps and to estimate the ice storages in large areas of mountain and polar glaciations (the Jungar Alatau, Great Caucasus, Spitsbergen, Franz Josef Land); (5) decreasing of glacier volumes on the Franz Josef Land and some Spitsbergen glaciers for the last decades had been estimated. Analysis of the data obtained had shown that considerable part of polythermal glaciers in Spitsbergen belong to type of surging glaciers; they have the winter englacial runoff and form the near‑glacier icings. It allows considering such glaciers as dynamically unstable, predisposed to surges as well as possible sources of winter water supply and additional sources of paleoinformation about long‑period variations of regional climate.

Micromorphology of modern tills in southwestern Spitsbergen – insights into depositional and post-depositional processes

AbstractTextural properties and microstructures are commonly used properties in the analysis of Pleistocene and older glacial deposits. However, contemporary glacial deposits are seldom studied, particularly in the context of post-depositional changes. This paper presents the results of a micromorphological study of recently deposited tills in the marginal zones of Hansbreen and Torellbreen, glaciers in southwestern Spitsbergen. The main objectives of this study were to compare modern tills deposited in subglacial and supraglacial conditions, as well as tills that were freshly released from ice with those laid down several decades ago. The investigated tills are primarily composed of large clasts of metamorphic rocks and represent coarse-grained, matrix-supported diamictons. The tills reveal several characteristic features for ductile (e.g.turbate structures) and brittle (e.g.lineations, microshears) deformations, which have been considered to be indicative of subglacial conditions. In supraglacial tills, the same structures are common as in the subglacial deposits, which points to the preservation of the primary features, though the sediment was transferred up to the glacier surface due to basal ice layer deformation and redeposited as slumps, or to formation of similar structures due to short-distance sediment re-deposition by mass flows. This study revealed that it might not be possible to distinguish subglacial and supraglacial tills on the basis of micromorphology if the latter are derived from a subglacial position. The only noted difference was the presence of iron oxide cementation zones and carbonate dissolution features in supraglacial tills. These features were found in tills that were deposited at least a few years ago and are interpreted to be induced by early post-depositional processes involving porewater/sediment interactions.

Do morphometric parameters and geological conditions determine chemistry of glacier surface ice? Spatial distribution of contaminants present in the surface ice of Spitsbergen glaciers (European Arctic).

The chemism of the glaciers is strongly determined by long-distance transport of chemical substances and their wet and dry deposition on the glacier surface. This paper concerns spatial distribution of metals, ions, and dissolved organic carbon, as well as the differentiation of physicochemical parameters (pH, electrical conductivity) determined in ice surface samples collected from four Arctic glaciers during the summer season in 2012. The studied glaciers represent three different morphological types: ground based (Blomlibreen and Scottbreen), tidewater which evolved to ground based (Renardbreen), and typical tidewater glacier (Recherchebreen). All of the glaciers are functioning as a glacial system and hence are subject to the same physical processes (melting, freezing) and the process of ice flowing resulting from the cross-impact force of gravity and topographic conditions. According to this hypothesis, the article discusses the correlation between morphometric parameters, changes in mass balance, geological characteristics of the glaciers and the spatial distribution of analytes on the surface of ice. A strong correlation (r=0.63) is recorded between the aspect of glaciers and values of pH and ions, whereas dissolved organic carbon (DOC) depends on the minimum elevation of glaciers (r=0.55) and most probably also on the development of the accumulation area. The obtained results suggest that although certain morphometric parameters largely determine the spatial distribution of analytes, also the geology of the bed of glaciers strongly affects the chemism of the surface ice of glaciers in the phase of strong recession.

Accelerating retreat and high-elevation thinning of glaciers in central Spitsbergen

Abstract. Svalbard is a heavily glacier-covered archipelago in the Arctic. Dickson Land (DL), in the central part of the largest island, Spitsbergen, is relatively arid and, as a result, glaciers there are relatively small and restricted mostly to valleys and cirques. This study presents a comprehensive analysis of glacier changes in DL based on inventories compiled from topographic maps and digital elevation models for the Little Ice Age (LIA) maximum, the 1960s, 1990, and 2009/2011. Total glacier area has decreased by ∼ 38 % since the LIA maximum, and front retreat increased over the study period. Recently, most of the local glaciers have been consistently thinning in all elevation bands, in contrast to larger Svalbard ice masses which remain closer to balance. The mean 1990–2009/2011 geodetic mass balance of glaciers in DL is among the most negative from the Svalbard regional means known from the literature.

Diversity and distribution of Tardigrada in Arctic cryoconite holes

<p>Despite the fact that glaciers and ice sheets have been monitored for more than a century, knowledge on the glacial biota remains poor. Cryoconite holes are water-filled reservoirs on a glacier’s surface and one of the most extreme ecosystems for micro-invertebrates. Tardigrada, also known as water bears, are a common inhabitant of cryoconite holes. In this paper we present novel data on the morphology, diversity, distribution and role in food web of tardigrades on Arctic glaciers. From 33 sampled cryoconite holes of 6 glaciers on Spitsbergen, in 25 tardigrades were found and identified. Five taxa of Tardigrada (Eutardigrada) were found in the samples, they are: <em>Hypsibius dujardini</em>, <em>Hypsibius </em>sp. A, <em>Isohypsibius </em>sp. A., <em>Pilatobius</em> <em>recamieri</em>, and one species of Ramazzottiidae. <em>H. dujardini </em>and <em>P. recamieri</em> were previously known from tundra in the Svalbard archipelago. Despite the number of studies on Arctic tundra ecosystems, <em>Hypsibius</em> sp. A, one species of Ramazzottiidae and <em>Isohypsibius</em> sp. A are known only from cryoconite holes. Tardigrade found in this study do not falsify the hypothesis that glaciers and ice sheets are a viable biome (characteristic for biome organisms assemblages - tardigrades). Diagnosis of <em>Hypsibius</em> sp. A, <em>Isohypsibius</em> sp. A, and species of Ramazzottiidae with discussion on the status of taxa, is provided. To check what analytes are associated with the presence of tardigrades in High Arctic glacier chemical analyses were carried out on samples taken from the Buchan Glacier. pH values and the chemical composition of anions and cations from cryoconite hole water from the Buchan Glacier are also presented. The current study on the Spitsbergen glaciers clearly indicates that tardigrade species richness in cryoconite holes is lower than tardigrade species richness in Arctic tundra ecosystems, but consists of unique cryoconite hole species. As cryoconite tardigrades may feed on bacteria as well as algae, they are primary consumers and grazers - secondary consumers of the decomposer food chain in this extreme ecosystem. </p>

Hydrothermal structure of a polythermal glacier in Spitsbergen by measurements and numerical modeling

Thickness of the upper cold ice layer in the ablation area of the polythermal glacier Grønfjordbreen (Spitsbergen) was estimated by means of numerical modeling. The results were compared with data of radio-echo sounding of the same glacier obtained in 1979 and 2012. Numerical experiments with changing water content in the lower layer of temperate ice and surface snow cover thickness made possible to compare calculated and modeled cold ice thicknesses and to estimate their changes for 33‑year period caused by regional climate change. According to data of radio-echo sounding, thickness of the cold ice layer decreased, on average, by 34 m. Numerical modeling shown similar results: the cold ice layer became thinner by 31 m and 39 m at altitudes 100–300 a.s.l. under the snow cover thickness of 1 m and 2 m. We explain this by rising of annual mean air temperature by 0,6 °С as compared to data of the nearest meteorological station Barentsburg in the same period. We believe that changes in cold ice layer thickness in polythermal glaciers can be used for estimation of changes in such regional climatic parameter as mean air temperature at different altitudes of the glacier surface in the ablation area.

Eskers formed at the beds of modern surge-type tidewater glaciers in Spitsbergen

This is the author accepted manuscript. The final version is available from the Geological Society of London via https://doi.org/doi.org/10.1144/M46.70

Former dynamic behaviour of a cold-based valley glacier on Svalbard revealed by basal ice and structural glaciology investigations

AbstractLarge numbers of small valley glaciers on Svalbard were thicker and more extensive during the Little Ice Age (LIA), demonstrated by prominent ice-cored moraines up to several kilometres beyond present-day margins. The majority of these glaciers have since experienced a long period of strongly negative mass balance during the 20th century and are now largely frozen to their beds, indicating they are likely to have undergone a thermal transition from a polythermal to a cold-based regime. We present evidence for such a switch by reconstructing the former flow dynamics and thermal regime of Tellbreen, a small cold-based valley glacier in central Spitsbergen, based on its basal sequence and glaciological structures. Within the basal sequence, the underlying matrix-supported diamict is interpreted as saturated subglacial traction till which has frozen at the bed, indicating that the thermal switch has resulted in a cessation of subglacial sediment deformation due to freezing of the former deforming layer. This is overlain by debris-poor dispersed facies ice, interpreted to have formed through strain-induced metamorphism of englacial ice. The sequential development of structures includes arcuate fracture traces, interpreted as shear planes formed in a compressive/transpressive stress regime; and fracture traces, interpreted as healed extensional crevasses. The formation of these sediment/ice facies and structures is indicative of dynamic, warm-based flow, most likely during the LIA when the glacier was significantly thicker.

Regional passive seismic monitoring reveals dynamic glacier activity on Spitsbergen, Svalbard

Dynamic glacier activity is increasingly observed through passive seismic monitoring. We analysed near-regional-scale seismicity on the Arctic archipelago of Svalbard to identify seismic icequake signals and to study their spatial–temporal distribution within the 14-year period from 2000 until 2013. This is the first study that uses seismic data recorded on permanent broadband stations to detect and locate icequakes in different regions of Spitsbergen, the main island of the archipelago. A temporary local seismic network and direct observations of glacier calving and surging were used to identify icequake sources. We observed a high number of icequakes with clear spectral peaks between 1 and 8 Hz in different parts of Spitsbergen. Spatial clusters of icequakes could be associated with individual grounded tidewater glaciers and exhibited clear seasonal variability each year with more signals observed during the melt season. Locations at the termini of glaciers, and correlation with visual calving observations in situ at Kronebreen, a glacier in the Kongsfjorden region, show that these icequakes were caused dominantly by calving. Indirect evidence for glacier surging through increased calving seismicity was found in 2003 at Tunabreen, a glacier in central Spitsbergen. Another type of icequake was observed in the area of the Nathorstbreen glacier system. Seismic events occurred upstream of the glacier within a short time period between January and May 2009 during the initial phase of a major glacier surge. This study is the first step towards the generation and implementation of an operational seismic monitoring strategy for glacier dynamics in Svalbard. Keywords: Iceberg calving; glacier surge; icequake; cryo-seismology; Svalbard. (Published: 4 December 2015) Citation: Polar Research 2015, 34 , 26178, http://dx.doi.org/10.3402/polar.v34.26178

The polar sulfur cycle in the Werenskioldbreen, Spitsbergen: Possible implications for understanding the deposition of sulfate minerals in the North Polar Region of Mars

In this study we investigated the polar cycling of sulfur (S) associated with the Werenskioldbreen glacier in Spitsbergen (Svalbard). Sulfide-derived S comprised 0.02–0.42wt% of the fine-grained fraction of proglacial sediments. These sediments originated from glacial erosion of Precambrian sulfide-rich quartz and carbonate veins. In summer 2008, the δ34S of dissolved SO4 in glacier melt waters (+9‰ to +17‰) was consistent with SO4 generation from oxidation of primary sulfide minerals in the bedrock (+9‰ to +16‰). The calculated monthly SO4 load was ∼6881kg/month/km2 in the main glacier stream. Subsequent evaporation and freezing of glacial waters lead to precipitation, accumulation, and temporary storage of sulfate salt efflorescences in the proglacial zone. These salts are presumably ephemeral, as they dissolve during annual snow/glacial melt events.Hydrated sulfates such as gypsum are also important constituents of the low-elevation areas around the polar ice cap of Planum Boreum on Mars. The origin of this gypsum on Mars might be better understood by using the investigated polar S cycle in Spitsbergen as a foundation. Assuming a trace sulfide content in the basaltic bedrock on Mars, the weathering of sulfides within the fine, porous texture of the ancient aeolian strata (basal unit) underlying Planum Boreum could have created elevated SO4 fluxes (and gypsum precipitation) during episodic thawing/melting events in the past. Limited water activity and prevailing dry conditions on the surface of Mars are the likely factors that accounted for the larger accumulation and preservation of polar gypsum on the surface and its broad aeolian distribution around Planum Boreum. This suggestion is also supported by an experiment showing that gypsum sand can be transported, under dry conditions, over great distances (∼2000km) without a significant loss of mass.

Succession of vascular plants in front of retreating glaciers in central Spitsbergen

Abstract Vegetation succession in front of five retreating glaciers was studied using phytosociological relevés (60) located at different distances between the Little Ice Age (LIA) moraines and the present glacier fronts around Petunia Bay. Approximate dating of succession stages was based on a study of the changing position of glacier fronts in the past approximately 100 years. The described succession corresponds to the uni-directional, non-replacement model of succession. All constituent species, except one, present in the nearby old tundra have colonized the glacier forelands since the end of the LIA. The first species appeared about 5 years after deglaciation. The latest succession stages closely re- semble the old tundra.

Surface and bed morphology of Hansbreen, a tidewater glacier in Spitsbergen

Surface and bed morphology of Hansbreen, a tidewater glacier in SpitsbergenHansbreen, a medium size tidewater glacier in Southern Spitsbergen (Svalbard) is one of the most intensively studied glaciers in the Arctic. This work presents new digital elevation models of its surface and basal topography based on data collected during GPS/GPR campaigns conducted in the spring seasons of 2005 and 2008, as well as on other recent topographic/bathymetric sources. The mean thickness of the glacier is calculated as 171 m and its volume is estimated to be 9.6 (±0.1) km3. The main feature of the bedrock morphology is a vast depression that is overdeepened below sea level and extends as far as 11 km upstream from the glacier front. This depression is divided into four individual basins by distinct sills that are related to the main geological/tectonic features of the area. The bedrock morphology affects considerably the glacier's surface topography. The influence of bedrock and surface relief on the subglacial drainage system geometry is discussed. Vast depressions on the glacier surface favor concentration of meltwater and development of moulin systems.

Ecophysiology and ultrastructure of Ancylonema nordenskiöldii (Zygnematales, Streptophyta), causing brown ice on glaciers in Svalbard (high arctic)

At the arctic archipelago of Svalbard, bare glacier surfaces are populated by microalgae like Ancylonema nordenskioldii (Zygnematales, Streptophyta). The resulting blooms cause, due to a vacuolar pigmentation, brownish colourations of the glacier surface. This freshwater ice alga has been described from several polar and alpine glaciers; however, these reports lacked data about the ecophysiology or ultrastructure. Considering the harsh environmental conditions of the exceptional habitat, such as permanently low temperatures, exposure to high irradiation or a short vegetation period, the aim of this study was to elucidate cellular adaptations of A. nordenskioldii. Thus, samples were collected at two glaciers in Spitsbergen. The cytoarchitecture of the cylindrical cells, which are arranged in unbranched filaments, demonstrates active cells with Golgi bodies, mitochondria and rough endoplasmic reticulum close to the nucleus when investigated by transmission electron microscopy (TEM). The cell walls are pore less and only 90 nm thin. A. nordenskioldii only sporadically produces oblong zygotes when two filaments conjugate. The most remarkable cytological feature is peripheral brownish vacuoles, appearing osmiophil and electron dense by TEM. Aqueous extracts of this pigmentation show a broad absorption in the visible light and in the UV. Consequently, a protection against excessive irradiation is provided. Photosynthesis measurements performed at different temperatures and light levels indicate that the metabolism is adapted to temperatures close to the freezing point as well as to high light conditions. Therefore, A. nordenskioldii can be regarded as metabolically and cytological well adapted to live on glaciers.