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Glacierized coasts undergo faster geomorphic processes than unglaciated ones. We have studied changes of the coastal area in southern Svalbard with the glacier bridge between Torell Land and Sorkapp Land since the beginning of the 20th century. The existence of a continuous subglacial depression beneath the Hornbreen–Hambergbreen system has been debated since the 1960s, with inconclusive results. In this study we assess both the subglacial topography and the bathymetry of Hornsund Fjord and Hambergbukta bay. This included ~40 km of radar surveys over the glacial system and sea depth sounding. The extent of the glaciers from maps and satellite images together with digital terrain models and surface elevation data based on GPS profiling were used to analyse geometry changes of the glacier surfaces. The results confirm the existence a continuous subglacial depression below sea level (c. 40 m deep) between Hornsund and the Barents Sea. The Hornbreen-Hambergbreen system has changed in shape over the past century, reflecting its dynamic origin and activity, also exemplified by the sequential surges identified since 1899. There was a pre-surge build-up event of Flatbreen causing a surge and subsequent lowering of the Hornbreen-Hambergbreen terminus by the 1960s. After, the entire surface lowered, albeit with a delay in the Hornbreen terminal zone. Since the year 2000, Hornbreen terminus has retreated at an average rate of 106 m a-1; ~50% faster than that of Hambergbreen. If the retreat continues at the 2000 – 2015 average rate, the ice bridge between Hornsund and Hambergbukta will be broken sometime between 2055 and 2065 and the Hornsund strait will separate Sorkapp Land from the Spitsbergen island. The processes and events described in this study, particularly the effects of the glacier surge, may provide a model for changes likely to occur in other coastal glaciated regions experiencing rapid change.

The central Arctic is within the range of air pollution transported from industrial areas of Eurasia and North America. A poor network of weather stations means that there is limited information available about air quality and contaminant deposition in the Arctic environment. For this reason seasonal snow cover is an important source of information. Chemical properties of precipitation, snow cover and fresh snow were monitored at the Hornsund Polish Polar Station (Spitsbergen) and in the altitude profile of the Hans Glacier. Meteorological data from the coast and the glacier helped to examine in detail the impact of atmospheric processes on snow cover contamination. The episode with extremely acidic precipitation was recognized in snow cover analysed in spring 2006. The source area of pollution and type of synoptic situation which enhanced transfer of pollution to the European Arctic were identified. Changes in snow chemistry in the altitude profile demonstrated the impact of the atmospheric boundary layer on chemical properties of precipitation and snow cover. Non-sea salt SO 2 emissions and the role of nitrate in acidification should be considered a serious threat to the Arctic environment.

The likelihood of a subglacial lake beneath Amundsenisen Plateau at Southern Spitzbergen, Svalbard, pointed out by the flat signal within the Ground Penetrating Radar (GPR) remote survey of the area, is justified, here, via numerical simulation. This investigation has been developed under the assumption that the icefield thickness does not change on average, as it is confirmed by recently published physical measurements taken over the past 40 years. As a consequence, we have considered admissible to assume the temperature and density in-depth profiles, snow and firn layers included, to be stationary. The upper icefield surface and the rocky bed surface are known in detail. The mathematical numerical model is based on an unsteady Stokes formulation of the ice flow and on a Large Eddy Simulation formulation of the lake water flow. Following the numerical sensitivity results that we presented on a recent issue of this journal, we have, here, upgraded the model by improving the description of critical aspects of icefield thermo-mechanics, such as the local water release within temperate ice as a strain heating effect and ice sliding on the bedrock. The first issue impacts on ice texture, i.e. its constitutive equation, while the second one drives icefield surging. Actually, we have obtained 13% enhancement of the numerical value of the ice top surface velocity versus measured one, and physically consistent numerical ice sliding velocity values at the rocky bottom. Adopting a new physically sound initial subglacial lake water temperature and velocity fields, we present the numerical simulation of the whole system, icefield and conjectured subglacial lake, within a time slot of 20,000 d (physical time), when its evolution trend was clearly captured. By then, although the maximum value of water temperature keeps rather low, metastability appears to be overcome on more than half of the conjectured basin, with a progressive trend in time in support to the subglacial lake existence. We stress that the numerical subglacial lake surface converges to the GPR flat signal spot with tolerance equal to the GPR measuring error. Finally, we observe that the numerical simulation results meet quantitatively and qualitatively the fundamental aspects of the conjecture, so that further on-site investigations on the subglacial lake (e.g. drilling operations) appear fully justified.

Designing future-proof materials goes beyond a quest for the best. The next generation of materials needs to be adaptive, multipurpose, and tunable. This is not possible by following the traditional experimentally guided trial-and-error process, as this limits the search for untapped regions of the solution space. Here, a computational data-driven approach is followed for exploring a new metamaterial concept and adapting it to different target properties, choice of base materials, length scales, and manufacturing processes. Guided by Bayesian machine learning, two designs are fabricated at different length scales that transform brittle polymers into lightweight, recoverable, and supercompressible metamaterials. The macroscale design is tuned for maximum compressibility, achieving strains beyond 94% and recoverable strengths around 0.1 kPa, while the microscale design reaches recoverable strengths beyond 100 kPa and strains around 80%. The data-driven code is available to facilitate future design and analysis of metamaterials and structures (https://github.com/mabessa/F3DAS).

The authors propose a model of glacial mass balance based on correlations with meteorological observations and data from climate re-analysis. The minimum input data required include the following: average monthly temperature on the glacier and in its vicinity during summertime for a reference time period, average monthly air temperature, and average precipitation total at the nearest weather station or from re-analysis. This model was used to hindcast the mass balance and its components at Werenskioldbreen (southern Svalbard) over the period 1912–2005. The hindcast specific mass balance was then used to estimate the change in the thickness of the snout of Werenskioldbreen over the period 1958–1990. These results were compared with results obtained using a cartographic method. Comparing the topographic maps, the glacier front lowered 28.7 m on average over 32 years. The average difference in the calculation of the change in glacier thickness between these two methods amounted to 3.7 m (based on me...

Subglacial conduit systems are thought to consist of dendritic networks that exist at lower pressure than distributed systems and have locations that are determined by theoretical hydraulic potential. On glaciers with moulins, however, meltwater is delivered to glacier beds at discrete points, violating assumptions of uniform recharge needed to calculate potential. To understand how moulins affect subglacial conduit hydrology, we used speleological techniques to map 0.4 km of subglacial conduit at the base of a moulin in Hansbreen, Svalbard, and compared our observations with theoretical predictions. The conduit began in an area predicted to lack drainage, crossed equipotential contours at oblique rather than right angles and was locally anastomotic rather than dendritic. We propose moulin locations, which are determined by the locations of supraglacial streams and crevasses, control locations of subglacial recharge. Because conduits have no direct causal relationship with gradients in effective pressure, this recharge can form conduits in areas of glacier beds that may not be predicted by hydraulic potential theory to have conduits. Recharge by moulins allows hydraulic head to increase in conduits faster and to higher values than in adjacent distributed systems, resulting in an increase rather than a decrease in glacier sliding speeds above subglacial conduits.

Recent trends in nitrogen and sulphur compounds in air and precipitation from a range of Arctic monitoring stations are presented, with seasonal data from the late 70s to 2004 or 2005. Earlier findings of declining sulphur concentrations are confirmed for most stations, while the pattern is less clear for reduced and oxidized nitrogen. In fact there are positive trends for nitrogen compounds in air at several stations. Acidity is generally reduced at many stations while the precipitation amount is either increasing or stable. Variability of sulphate concentrations in air for the period 1991–2000 is reasonably well reproduced at most stations using an Eulerian, hemispherical model. Results for nitrogen compounds are weaker. Scenario studies show that even if large sulphur emission reductions take place in important source regions in South-East Asia in the coming decades, only small changes in Arctic deposition can be expected. This is because South-East Asian emissions have small influence north of the Arctic circle.

The melting of glaciers coming with climate change threatens the heritage of the last glaciation of Europe likely contained in subglacial lakes in Greenland and Svalbard. This aspect urges specialists to focus their studies (theoretical, numerical, and on-field) on such fascinating objects. Along this line, we have approached the validation of the conjecture of the existence of a subglacial lake beneath the Amundsenisen Plateau at South-Spitzbergen, Svalbard, where ground penetrating radar measurements have revealed several flat signal spots, the sign of the presence of a body of water. The whole investigation aspects, mathematical modeling and numerical simulation procedure, and the numerical results are presented through a trilogy of papers of which the present one is the last. The time-dependent mathematical model in the background of the numerical algorithm includes the description of dynamics and thermodynamics of the icefield and of the subglacial lake, with heat exchange and liquid/solid phase-change mechanisms at the interface. Critical modeling choices and confidence in the algorithm are granted by the numerical results of the sensitivity analysis versus the contribution of ice water content, of firn and snow layers at top of the icefield and versus the approximation of ice sliding on bedrock. The two previous papers deal with these issues, show successful comparison with local measured quantities, and demonstrate numerically the likelihood of the subglacial lake. In this work, we aim at providing the studied case and the numerical algorithm with a possible paradigmatic value. At this aim, we introduce on-field measurement data related to the physical characteristics of the Amundsenisen Plateau that justify the adoption of significant modeling simplifications, here, focussed from physical viewpoint. Furthermore, we present the numerical algorithm and discuss several representative results from the numerical test to point out the type of results coming from the procedure. Such results might, eventually, provide a support to the decision to undertake drilling operations for tracing the subglacial water bio-chemicals generally present within the accreted ice above the presumed ice/water front.

In order to study the seasonal and inter-seasonal variations in radio-wave velocity (RWV), radiophysical investigations were made at Hansbreen, a polythermal glacier in Spitsbergen, in July– August 2003 and April 2004. These investigations included repeated radar profiling (20 and 25 MHz) along a transverse profile, repeated common-midpoint measurements, continuous radar measurements during 8 days at a fixed site, meteorological observations, and continuous ice surface velocity monitoring by differential GPS. Seasonal and inter-seasonal RWV changes in the temperate ice layer are attributed, respectively, to rapid water redistribution within it during the summer, and to variations in water content from 2.1% in summer to 0.4% in spring. The reflection properties of the temperate ice layer correlate well with the air temperature, with a nearly semi-diurnal time lag. The temporal variability of the reflection properties of the internal horizon suggests enlargement of water inclusions or water drainage from the horizon. Repeated profiling shows a stable spatial pattern in bed reflection power interpreted as changes in water content controlled by bedrock topography. The spatial variations of internal reflection energy along the repeated profile correlate with the thickness of the cold ice layer and the occurrence of drainage and crevasse systems.

High-resolution ground-penetrating radar surveys at 50 MHz on the polythermal glaciers Hornbreen, Hambergbreen and several surrounding glaciers in southern Spitsbergen, Svalbard, are presented and interpreted. Accurate positioning was obtained using differential global positioning system (DGPS). Digital elevation models (DEMs) of the bedrock and surface were constructed. Comparison of DGPS data and surface DEMs with data from the topographic mappings from 1936 oblique stereoscopic aerial photographs and from Mission Russe in 1899–1901 shows that the Hornbreen and Hambergbreen surfaces are about 60–100 m thinner today in the upper part than at the beginning of the 20th century. Hornbreen has retreated by 13.5 km from the central part of the front, and Hambergbreen by 16 km. All the fronts of the nearby east-coast glaciers in this area have retreated. The bedrock DEM shows that the Hornbreen and Hambergbreen beds lie at –25 to 25 m a.s.l. The combination of sub-sea-level fronts and increasing steepness of the glaciers suggests that the low-lying glaciated valley filled by Hornbreen and Hambergbreen may become a partially inundated ice-free isthmus within perhaps 100 years.

Detailed ground-penetrating radar (GPR) surveys at 50 and 200 MHz on Hansbreen, a polythermal glacier in southern Svalbard, are presented and interpreted. Comparison of the variations in character of the radar reflections with borehole thermometry and water levels in moulins suggests that GPR can be used to study the hydrothermal properties of the glacier. The high resolution of the GPR data shows that the hydrothermal structure of the glacier is highly variable both along the centre line and on transverse profiles. Water contents for many places and depths within the glacier were calculated by estimating radar-wave velocities to point reflectors. We find typical water contents of 1-2% for the temperate ice, but wetter ice associated with surface crevassing and moulins (typically 4% water content). There is evidence that wet ice sometimes overlays drier ice. The hydrothermal structure is thus shown to be very complex. Temperature gradients in the cold ice indicate freezing rates of temperate ice below cold ice of 0.1-0.5 ma-1, while isolated point reflectors within the cold ice indicate large water-filled bodies that are probably related to the regular drainage structure of the glacier.

We present a new numerical procedure to assess the plausibility of a subglacial lake in case of relative small/moderate extension and surging temperate icefield. In addition to the flat signal from Ground Penetrating Radar remote survey of the area, early indication of a likely subglacial lake, required icefield data are: top surface elevation and bathymetry, top surface velocity at some points, in-depth temperature and density profiles of upper layer. The procedure is based on a mathematical model of the evolution of dynamics and thermo-dynamics of the icefield and of a subglacial lake. The Glen’s law is adopted for ice rheology and Stokes reduction is applied; Large Eddy Simulation technique is used for the lake. Ice/water phase change is described. Finite volumes for model discretization and a front-tracking technique to follow the moving interface characterize the numerical method. We have applied this procedure to the case of a subglacial lake conjectured in the area of Amundsenisen, Svalbard, and, here, the results of a sensitivity study are discussed. In particular we point out that the effect of firn and snow upper layers on the system, in terms of temperature field, density and water content, has to be included in the modeling, as it contributes to the overcoming of the ice metastable state and the release of subglacial water. Accordingly, ice water content changes have to be carefully described. The depth of the bed depression is confirmed to be critical for the formation of the lake.

Ariebreen is a small (0.37 km 2 )-valley glacier located in southern Spitsbergen. Our ground-penetrating radar surveys of the glacier show that it is less than 30 m thick on average, with a maximum thickness of 82 m, and it appears to be entirely cold. By analysing digital terrain models of the ice surface from different dates, we determine the area and volume changes during two periods, 1936-1990 and 1990-2007. The total ice volume of the glacier has decreased by 73% during the entire period 1936-2007, which is equivalent to a mean mass balance rate of -0.61±0.17 m y -1 w.eq. The glacier thinning rate has increased markedly between the first and second periods, from -0.50±0.22 to -0.95±0.17 m y -1 w.eq. Keywords: Ice-volume changes; ground-penetrating radar; thinning rate; Ariebreen; Spitsbergen; Svalbard (Published: 1 August 2013) To access the supplementary material for this article, please see Supplementary files in the column to the right (under Article Tools) Citation: Polar Research 2013, 32 , 11068, http://dx.doi.org/10.3402/polar.v32i0.11068

Recent work has shown that surface-to-bed drainage systems re-form annually on parts of the Greenland ice sheet and some High Arctic glaciers, leading to speed-up events soon after the onset of summer melt. Surface observations and geophysical data indicate that such systems form by hydrologically driven fracture propagation (herein referred to as ‘hydrofracturing’), although little is known about their characteristics. Using speleological techniques, we have explored and surveyed englacial drainage systems formed by hydrofracturing in glaciers in Svalbard, Nepal and Alaska. In Hansbreen, Svalbard, vertical shafts were followed through ∼60 m of cold ice and ∼10 m of temperate basal ice to a subglacial conduit. Deep hydrofracturing occurred at this site due to a combination of extensional ice flow and abundant surface meltwater at a glacier confluence. The englacial drainage systems in Khumbu Glacier, Nepal, and Matanuska Glacier, Alaska, USA, formed in areas of longitudinal compression and transverse extension and consist of vertical slots that plunge down-glacier at angles of 55° or less. The occurrence of englacial drainages initiated by hydrofracturing in diverse glaciological regimes suggests that it is a very widespread process, and that surface-to-bed drainage can occur wherever high meltwater supply coincides with ice subjected to sufficiently large tensile stresses.

[1] We estimate annual anomalies of the surface mass balance of glaciers on Svalbard for the period 2000–2005 (six years), by calculating the so-called ‘‘satellite-derived mass balance’’ (Bsat) from time series of satellite-derived surface albedos. The method needs no other input variables. Surface albedos are extracted from the Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra albedo product. We validate the MODIS albedos by comparing them with in situ measurements on Kongsvegen, and we find a low root-meansquare error of 0.04 for higher-quality MODIS data. Confidence in the MODIS product is also provided by realistic profiles of albedo along glacier centerlines. We apply the method to 18 glaciers that are evenly distributed over the archipelago. Correlation coefficients of time series of Bsat and direct measurements of the annual mass balance on Kongsvegen and Hansbreen are highly significant (0.94 and 0.82, respectively). Moreover, spatial distributions of the anomalies for individual years are coherent. Disadvantages of the method are that absolute values of the mass balance cannot be determined and that the interannual variability is underestimated. The latter might be corrected by equations to be established with mass balance models.

Conducting research in the remote and inaccessible parts of the Globe often demands specific logistical actions. Long-term research programmes are thus usually carried out by permanent research teams working in particular stations. The working conditions under such circumstances frequently fall short of the standards set for the average research centers and laboratories. Still, the quality of the data and information to be produced has to meet the established quality norm. The Polish Polar Station Hornsund, that has been working in Spitsbergen since 1957 can serve as a model of the research and logistical solutions to be adopted for other stations in the Arctic as well as in other remote parts of the world.

To improve our understanding of Svalbard-type polythermal glacier drainage, hydraulic geometry models of the subglacial hydrology of two contrasting glaciers in Svalbard have been constructed. The models are tested against a uniquely long and rich set of field observations spanning 45 years. Digital elevation models (DEMs) were constructed from bedrock data measured with ground penetrating radar and surface data of two medium-sized polythermal glaciers, Hansbreen and Werenskioldbreen, in south-west Spitsbergen. Hansbreen has a low angle bed with over-deepenings and a calving front, while Werenskioldbreen has steeper bed and terminates on land. Together they are representative of many Svalbard glaciers. The DEMs were used to derive maps of hydraulic potential and subglacial drainage networks. Validation of the models was done using field observations including location mapping and speleological exploration of active moulins, positions of main river outflows, dyetracing and water chemistry studies, and observations of water pressure inside moulins. Results suggest that the water pressure is generally close to ice overburden pressure but varies greatly depending on local conditions such as bed location, the thickness of cold ice layer, the thickness of the glacier and seasonal changes in meltwater input.

Decomposition yields of tetracycline hydrochloride /TC.HCl/ and chlorotetracycline hydrochloride /ClTC−HCl/ in methanol solution saturated with Ar or N2O were determined. Rate constants of the reaction es with some antibiotics were obtained: $$\begin{gathered} k/e_s^ - + ClTC \cdot HCl/ = 2 \cdot 49 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} ; \hfill \\ k/e_s^ - + TC \cdot HCl/ = 2 \cdot 86 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} \cdot \hfill \\ \end{gathered} $$