High Arctic Glacier Research Articles

An investigation into the mechanisms controlling seasonal speedup events at a High Arctic glacier

Seasonal variations in ice motion have been observed at several polythermal ice masses across the High Arctic, including the Greenland Ice Sheet. However, such variations in ice motion and their possible driving mechanisms are rarely incorporated in models of the response of High Arctic ice masses to predicted climate warming. Here we use a three‐dimensional finite difference flow model, constrained by field data, to investigate seasonal variations in the distribution of basal sliding at polythermal John Evans Glacier, Ellesmere Island, Canada. Our results suggest that speedups observed at the surface during the melt season result directly from changes in rates of basal motion. They also suggest that stress gradient coupling is ineffective at transmitting basal motion anomalies to the upper part of the glacier, in contrast to findings from an earlier flow line study at the same glacier. We suggest that stress gradient coupling is limited through the effect of high drag imposed by a partially frozen bed and friction induced by valley walls and significant topographic pinning points. Our findings imply that stress gradient coupling may play a limited role in transmitting supraglacially forced basal motion anomalies through Arctic valley and outlet glaciers with complex topographic settings and highlight the importance of dynamically incorporating basal motion into models predicting the response of the Arctic's land ice to climate change.

Modeling the refreezing of meltwater as superimposed ice on a high Arctic glacier: A comparison of approaches

The refreezing of meltwater is known to be a critical factor when assessing the mass balance state of glaciers in the high Arctic. Several different models of this process are widely used in numerical glacier simulations but, as yet, no attempt has been made to compare these approaches or to assess their relative performance against field measurements. Such models are likely to include implicit calibrations which may prove to be invalid under conditions different from those for which they were constructed. We test a selection of six refreezing algorithms taken from the literature against field measurements of net mass balance and superimposed ice formation made at a high Arctic glacier. Running these models for 1971–2002 using daily meteorological data and forward until 2050 using a range of future scenarios for the climate of Svalbard we are able to make the following conclusions concerning mass balance modeling: (1) The choice of meltwater refreezing model has a significant impact on the calculated net mass balance of a glacier. (2) Three of the models tested could, with suitable tuning, simultaneously reproduce both superimposed ice quantities and net mass balance measurements within their respective bounds of uncertainty, while the other three could not. (3) In situations where the model can be tuned to field measurements indicative of mass balance, future predictions of mass balance are largely independent of the specific meltwater refreezing model used.

Viral dynamics in cryoconite holes on a high Arctic glacier (Svalbard)

Viruses are an abundant and dynamic constituent of microbial communities in aquatic ecosystems. In this study we characterized the abundance of viruses associated first with the bottom sediment and overlying water of cryoconite holes and second with shallow ice cores of two different glaciers in Svalbard. Viral abundances were ca. 10–100 times lower than the average for marine and freshwater ecosystems in temperate regions. Virus to bacterium ratios (VBR) (average > 10, range between 0.7 and 74 in the water and ice samples) and a strong positive correlation between viral and bacterial abundance (r = 0.93, p < 0.01, N = 57) indicate that viruses most probably play an important role in controlling bacterial mortality and hence biogeochemical cycling on glaciers. Samples taken along a transect from the glacier ablation area to proglacial ponds in its forefield showed that viral abundance increased in response to a higher host availability, which in turn probably resulted from an increase in temperature and higher mineral levels in the ponds. In a transplantation experiment, viruses from cryoconite holes were incubated with a bacterial community from a proglacial lake. Results from the transplantation experiment showed that viruses from cryoconite holes were able to infect bacteria from proglacial lakes and thus influence biogeochemical cycles across different glacial ecosystems. Our data therefore suggest that viruses in cryoconite holes may be able to infect a broad range of bacterial species.

Influence of the Arctic Circumpolar Vortex on the Mass Balance of Canadian High Arctic Glaciers

AbstractVariability in July mean surface air temperatures from 1963 to 2003 accounted for 62% of the variance in the regional annual glacier mass balance signal for the Canadian High Arctic. A regime shift to more negative regional glacier mass balance occurred between 1986 and 1987, and is linked to a coincident shift from lower to higher mean July air temperatures. Both the interannual changes and the regime shifts in regional glacier mass balance and July air temperatures are related to variations in the position and strength of the July circumpolar vortex. In years when the July vortex is “strong” and its center is located in the Western Hemisphere, positive mass balance anomalies prevail. In contrast, highly negative mass balance anomalies occur when the July circumpolar vortex is either weak or strong without elongation over the Canadian High Arctic, and its center is located in the Eastern Hemisphere. The occurrence of westerly positioned July vortices has decreased by 40% since 1987. The associated shift to a dominantly easterly positioned July vortex was associated with an increased frequency of tropospheric ridging over the Canadian High Arctic, higher surface air temperatures, and more negative regional glacier mass balance.

Evidence for widespread anoxia in the proglacial zone of an Arctic glacier

The major ion (SO 4 2−, HCO 3 −, NO 3 −) and stable isotope composition ( δ 18O–H 2O, δ 18O–SO 4 2−, δ 34S–SO 4 2− and DIC- δ 13C) of ground- and surface water samples collected from the proglacial zone of a retreating high Arctic glacier, (Finsterwalderbreen, Svalbard) indicate the widespread occurrence of microbially-mediated processes under anoxic conditions. The δ 18O–SO 4 2− of active layer groundwaters, lake and stream waters is strongly depleted in 18O compared to the δ 18O–H 2O, and stable isotope mass balance arguments indicate that 75–95% of SO 4 2− in these waters is produced by the oxidation of sulphide minerals using Fe(III) and NO 3 − under anoxic conditions. Consistent with this is the frequent loss or depletion of NO 3 − from ground- and surface waters. SO 4 2− concentrations and δ 18O–SO 4 2− and δ 18O–H 2O data suggest that much of the SO 4 2− is generated anoxically early in the melt season in 18O depleted snowmelt, and is immobilized as sulphate salts in near surface moraine due to evaporative concentration. These salts are remobilized later in the season by rainfall and glacial flood events and cause the δ 18O–SO 4 2− of proglacial meltwaters to be < δ 18O–H 2O. The latter become isotopically heavy through the melt season due to evaporation. The lack of any relationship between δ 34S–SO 4 2− and δ 18O–SO 4 2− and relatively heavy DIC- δ 13C values in proglacial waters suggests that sulphate reduction is not a significant process. Acidity produced during anoxic oxidation of sulphides appears to drive chemical weathering in the proglacial zone, enabling high chemical weathering rates to be maintained despite the absence of dissolved oxygen. Similar findings have been reported from subglacial environments, where anoxic sulphide oxidation is widely observed. The absence of evidence for sulphate reduction in the proglacial groundwaters, however, suggests that the degree of anoxia in deglaciated settings may not be widespread as in subglacial environments, where significant sulphate reduction has been observed.

Carbon and nitrogen limitation of soil microbial respiration in a High Arctic successional glacier foreland near Ny-Ålesund, Svalbard

The hypotheses that carbon and nitrogen availability limit microbial activity, and that the key factors limiting microbes vary along the successional gradient were tested in a High Arctic glacier foreland. We examined the responses of the respiration rate and the phospholipid fatty acid content to the addition of carbon and/or nitrogen. Soil samples were collected from the early stage and late stage of primary succession in the foreland of a glacier near Ny-Ålesund, Svalbard. The addition of both carbon (glucose) and nitrogen (ammonium nitrate) engendered an increase in the microbial respiration rate in the early stage of succession. In contrast, the addition of either carbon or nitrogen did not increase the microbial respiration rate. In the late stage of succession the addition of carbon alone, as well as the addition of both carbon and nitrogen, increased the microbial respiration rate. However, neither the addition of carbon nor the addition of nitrogen affected the total phospholipid fatty acid content (an index of microbial biomass) for any soil within 15 days of incubation at 10 ° C. An increase in the respiration rate was therefore attributed to changes in the physiological activities of the microbial community, such as enzymatic activity. Our study suggests that microbial respiration was limited by the low availability of both carbon and nitrogen in the early stage of succession. Thereafter, nitrogen limitation is mitigated.

Carbon and nitrogen limitation of soil microbial respiration in a High Arctic successional glacier foreland near Ny-Ålesund, Svalbard

The hypotheses that carbon and nitrogen availability limit microbial activity, and that the key factors limiting microbes vary along the successional gradient were tested in a High Arctic glacier foreland. We examined the responses of the respiration rate and the phospholipid fatty acid content to the addition of carbon and/or nitrogen. Soil samples were collected from the early stage and late stage of primary succession in the foreland of a glacier near Ny-Ålesund, Svalbard. The addition of both carbon (glucose) and nitrogen (ammonium nitrate) engendered an increase in the microbial respiration rate in the early stage of succession. In contrast, the addition of either carbon or nitrogen did not increase the microbial respiration rate. In the late stage of succession the addition of carbon alone, as well as the addition of both carbon and nitrogen, increased the microbial respiration rate. However, neither the addition of carbon nor the addition of nitrogen affected the total phospholipid fatty acid content (an index of microbial biomass) for any soil within 15 days of incubation at 10 ° C. An increase in the respiration rate was therefore attributed to changes in the physiological activities of the microbial community, such as enzymatic activity. Our study suggests that microbial respiration was limited by the low availability of both carbon and nitrogen in the early stage of succession. Thereafter, nitrogen limitation is mitigated.

Proglacial succession of biological soil crusts and vascular plants: biotic interactions in the High Arctic

To evaluate the hypothesis that biological soil crusts facilitate the establishment and maintenance of vascular plants during succession, we studied the distribution patterns of crusts and vascular plants along a High Arctic glacier foreland and compared the success of plants growing in and out of crusted substrate. Multivariate analyses determined that distance from the glacier and crust cover were the most important variables, explaining 11% and 9% of the variance in the vegetation data, respectively. Surfaces colonized by biological soil crusts generally supported higher plant densities and showed positive associations with the most dominant, long-lived plant species such as Saxifraga oppositifolia L., Salix arctica Pall., and Dryas integrifolia Vahl. Crusts facilitate plant establishment and growth in early and midsuccession but may compete for available resources further along the chronosequence. This study recognizes subtle direct influences of crust on vegetation density but also draws attention to a much larger overall positive effect on community structure. Succession on this foreland proceeds via a “directional-replacement” model and supports a well-developed community of biological soil crusts and vascular plants with greater species richness, cover, and density compared with other glacier foreland vegetation communities previously investigated on Ellesmere Island, Nunavut.

Yeasts in high Arctic glaciers: the discovery of a new habitat for eukaryotic microorganisms

Recently a new habitat for microbial life has been discovered at the base of polythermal glaciers. In ice from these subglacial environments so far only non-photosynthetic bacterial communities were discovered, but no eukaryotic microorganisms. We found high numbers of yeast cells, amounting to a maximum of 4,000 CFU ml(-1) of melt ice, in four different high Arctic glaciers. Twenty-two distinct species were isolated, including two new yeast species. Basidiomycetes predominated, among which Cryptococcus liquefaciens was the dominant species (ca. 90% of total). Other frequently occurring species were Cryptococcus albidus, Cryptococcus magnus, Cryptococcus saitoi and Rhodotorula mucilaginosa. The dominant yeast species were psychrotolerant, halotolerant, freeze-thaw resistant, unable to form mycelium, relatively small-sized and able to utilize a wide range of carbon and nitrogen sources. This is the first report on the presence of yeast populations in subglacial ice.

Hydrology and dynamics of a polythermal (mostly cold) High Arctic glacier

AbstractTo improve our understanding of the interactions between hydrology and dynamics in mostly cold glaciers (in which water flow is limited by thermal regime), we analyse short‐term (every two days) variations in glacier flow in the ablation zone of polythermal John Evans Glacier, High Arctic Canada. We monitor the spatial and temporal propagation of high‐velocity events, and examine their impacts upon supraglacial drainage processes and evolving subglacial drainage system structure. Each year, in response to the rapid establishment of supraglacial–subglacial drainage connections in the mid‐ablation zone, a ‘spring event’ of high horizontal surface velocities and high residual vertical motion propagates downglacier over two to four days from the mid‐ablation zone to the terminus. Subsequently, horizontal velocities fall relative to the spring event but remain higher than over winter, reflecting channelization of subglacial drainage but continued supraglacial meltwater forcing. Further transient high‐velocity events occur later in each melt season in response to melt‐induced rising supraglacial meltwater inputs to the glacier bed, but the dynamic response of the glacier contrasts with that recorded during the spring event, with the degree of spatial propagation a function of the degree to which the subglacial drainage system has become channelized. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Chemical and Isotopic Switching within the Subglacial Environment of a High Arctic Glacier

Natural environmental isotopes of nitrate, sulphate and inorganic carbon are discussed in conjunction with major ion chemistry of subglacial runoff from a High Arctic glacier, Midre Lovenbreen, Svalbard. The chemical composition of meltwaters is observed to switch in accordance with subglacial hydrological evolution and redox status. Changing rapidly from reducing to oxidizing conditions, subglacial waters also depict that 15N/14N values show microbial denitrification is an active component of nutrient cycling beneath the glacier. 18O/16O ratios of sulphate are used to elucidate mechanisms of biological and abiological sulphide oxidation. Concentrations of bicarbonate appear to be governed largely by the degree of rock: water contact encountered in the subglacial system, rather than the switch in redox status, although the potential for microbiological activity to influence ambient bicarbonate concentrations is recognised. Glaciers are therefore highlighted as cryospheric ecosystems supporting microbial life which directly impacts upon the release of solute through biogeochemically mediated processes.

Superimposed ice regime of a high Arctic glacier inferred using ground-penetrating radar, flow modeling, and ice cores

[1] A 900 MHz ground-penetrating radar (GPR) profile, collected along 1.7 km of the centerline of a high Arctic glacier in Svalbard, is interpreted using shallow ice core data and thermomechanical flow modeling. Four distinct zones are visible in the image and correspond to areas of firn, recent and older superimposed ice, and ablation zone glacier ice on the ground. The areas of firn and superimposed ice are characterized by relatively steeply and gently dipping internal reflecting horizons (IRH), respectively, in the radar image. The IRHs arise from permittivity contrasts due to density variations, produced in firn by alternating firn and ice layers, and in superimposed ice by varying air bubble content. Recently formed and older superimposed ice can be distinguished in the GPR image. A three-dimensional flow model is used to indicate the long-term mass balance and flow history responsible for the spatial distribution and orientation of superimposed ice IRHs in the radar image. Results indicate that the IRH distribution can only be explained by invoking a down-glacier shift in mean 30 year equilibrium line altitude (ELA) by 20–30 m, compared with measured mean 30 year ELA. They also suggest that many of the superimposed IRHs are relict features, produced >100 years B.P., when the ELA was 100–150 lower than at present. This work advocates combined GPR and flow modeling as a unique tool for validating mass balance measurements and/or inferring the mass balance/dynamic history of a glacier beyond a recent measurement period.

Geocryological processes linked to High Arctic proglacial stream suspended sediment dynamics: examples from Bylot Island, Nunavut, and Spitsbergen, Svalbard

AbstractRecent research has identified differences in processes contributing to suspended sediment concentration (SSC) dynamics in proglacial streams between High Arctic and alpine catchments, but does not examine processes explicitly linked to the periglacial environment. Three glacierized basins were studied: Austre Brøggerbreen and Midre Lovénbreen, Svalbard (79°N, 12°E) and Glacier B28, unofficially named Stagnation Glacier, Bylot Island, Nunavut (73°N, 78°W). SSC variations were modelled from continuous turbidity, discharge and meteorological data throughout the summer months. Three statistical tools were utilized: principal component analysis, change‐point analysis and multivariate regression. These are shown to be effective in identifying subperiods of distinctive geocryological and glaciofluvial characteristics. Multivariate regression for the subseasons included autoregressive integrated moving‐average modelling, and showed that SSC variations were related not only to discharge variability, but also to fluctuations in energy fluxes. The results are interpreted in terms of spatio‐temporal changes in sediment mobilization and supply associated with changes in the relative importance of fluvial, glacial and periglacial processes. This evidence supports the notion of important linkages between glacial, fluvial and periglacial systems, but exemplifies distinct variability between High Arctic glaciers. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Interannual variability in the spatial distribution of winter accumulation at a high-Arctic glacier (Finsterwalderbreen, Svalbard), and its relationship with topography

AbstractGlacier mass balance and hydrology are strongly influenced by the distribution of snow accumulation at the start of the melt season. Two successive end-of-winter snow-cover surveys at Finsterwalderbreen, Svalbard, are here used to investigate the interannual variability in the spatial distribution of accumulation, and its relationship with topography. 40–62% of the variance in snow depth was not determined by elevation (assessed by linear regression of snow depth on surface elevation), which could not therefore necessarily be used as a sole predictor of the spatial distribution of accumulation here. Principal components (PC) analysis of the topographic variables elevation, slope, north–south and east–west aspects shows that only two of six PCs, determined for 2years’ sampling locations, had maximum loadings on altitude; aspect was more important, with maximum loadings on four PCs. Hierarchical cluster analysis was then applied to these PCs: significant correlations with accumulation in each of two terrain clusters were given by (1) elevation and slope, (2) east–west aspect only (1999); (1) elevation only, (2) no significant correlations (2000). There is strong interannual variability not only in the magnitude of winter accumulation (0.41 mw.e. in 1999, 0.58 mw.e. in 2000), but also in its spatial distribution, and its relationship with topography.

Subglacial drainage processes at a High Arctic polythermal valley glacier

AbstractDye-tracer experiments undertaken over two summer melt seasons at polythermal John Evans Glacier, Ellesmere Island, Canada, were designed to investigate the character of the subglacial drainage system and its evolution over a melt season. In both summers, dye injections were conducted at several moulins and traced to a single subglacial outflow. Tracer breakthrough curves suggest that supraglacial meltwater initially encounters a distributed subglacial drainage system in late June. The subsequent development and maintenance of a channelled subglacial network are dependent upon sustained high rates of surface melting maintaining high supraglacial inputs. In a consistently warm summer (2000), subglacial drainage became rapidly and persistently channelled. In a cooler summer (2001), distributed subglacial drainage predominated. These observations confirm that supraglacial meltwater can access the bed of a High Arctic glacier in summer, and induce significant structural evolution of the subglacial drainage system. They do not support the view that subglacial drainage systems beneath polythermal glaciers are always poorly developed. They do suggest that the effects on ice flow of surface water penetration to the bed of predominantly cold glaciers may be short-lived.

Surface mass balance of the Ward Hunt Ice Rise and Ward Hunt Ice Shelf, Ellesmere Island, Nunavut, Canada

The Ward Hunt Ice Rise and Ward Hunt Ice Shelf, located on Ellesmere Island, Canada, are two of the northernmost land ice masses on the North American continent. Surface mass balance measurements (excluding calving and subice processes) began in 1959 on the ice rise and in 1966 on the ice shelf but were frequently interrupted, most recently between 1986 and 2002. The surface balance of the ice rise and ice shelf follows the temporal pattern seen on other measured High Arctic glaciers. The overall surface mass losses over the last 45 years have been comparatively low (1.68 m water equivalent (w eq) for the ice rise and 3.1 m w eq for the ice shelf), which reflects their proximity to the Arctic Ocean. Nevertheless, the ice shelf appears to have weakened sufficiently in recent years to raise concerns about its possible disintegration in the near future. The 2002/2003 balance year was the most negative year on record (−0.33 m w eq for the ice rise and −0.54 m w eq for the ice shelf). Dynamical stresses related to wind, wave, and tidal action may further accelerate this process, as open water conditions on the Arctic Ocean become more prevalent. The Ward Hunt Ice Rise has so far remained in a reasonably healthy state in terms of its overall surface mass balance, although its long‐term survival is also threatened by current and predicted future climatic conditions.

Hydrology, geochemistry and Sr isotopes in solids and solutes of the meltwater from Mittivakkat Gletscher, SE Greenland

This study was initiated to investigate elemental fractionation and Sr isotope systematics associated with glacial erosion by direct comparison of particulate and dissolved load in glacial runoff. Discharge measurements along with chemical and Sr isotope investigations were carried out at the Mittivakkat Gletscher (Glacier), Ammassalik Ø, Southeast Greenland. Major bedrock types are the Ammassalik Intrusive Complex (AIC) of mafic composition and garnet–granite gneiss (GGG) of acidic composition. Mechanical denudation rates (1 mm a−1) reflected in the major outflow are in the range of temperate valley glaciers in Norway. Chemical denudation rates (32 t km−2 a−1) and estimated rates of CO2 drawdown by silicate weathering (720–100 kgC km−2 a−1) are low compared to global mean and match values measured for High Arctic glaciers on Svalbard. The contrast in chemical and Sr isotope composition of bedrock makes Sr isotope ratios a powerful tool for determining source areas of solid and dissolved load. High Ca/K ratios in water compared to suspended particulate matter (SPM) indicate faster dissolution of Ca minerals. By contrast, in GGG bedrock, where biotite and K-feldspar are abundant, Sr isotope ratios in solutes are higher than in SPM, supporting preferential release of 87Sr from a K-mineral lattice.

Stable isotope evidence for microbial sulphate reduction at the bed of a polythermal high Arctic glacier

Glacier beds may be host to a range of microbial communities, which drive oxic waters towards anoxia along certain hydrological flowpaths. Chemical and isotopic signatures in meltwaters from Finsterwalderbreen, a polythermal glacier on sedimentary bedrock in Svalbard, show clear evidence for anoxia at the glacier bed. Increases in δ34S and δ18O of sulphate indicate that microbial sulphate reduction has resulted in significant decreases in sulphate concentration. The δ13C of the dissolved inorganic carbon (DIC) is isotopically light (δ13C=−8‰), which is consistent with the use of bedrock kerogen and/or the necromass of sulphide oxidising bacteria as organic substrates for the sulphate-reducing bacteria. Calculated rates of organic carbon mineralisation correspond to ∼10% of the total annual DIC flux of the glacial meltwaters. This microbial ecosystem is chemoautotrophically based, ultimately being sustained by the kerogen and/or bacterial necromass and sulphides in the bedrock. This work suggests that glacier beds can be refugia for life when climatic and/or atmospheric conditions are otherwise inclement and also supports the contention that microbial life is present in subglacial Lake Vostok.

Carbon Isotope Discrimination in Diverging Growth Forms of Saxifraga oppositifolia in Different Successional Stages in a High Arctic Glacier Foreland

We investigated carbon isotope discrimination of two morphs of Saxifraga oppositifolia and other plant species in a glacier foreland in the High Arctic at Ny-Ålesund, Svalbard, Norway. At this site, soil conditions vary considerably along with the progress of primary succession within a small area. We compared growth forms and δ13C values, which reflect long-term leaf gas exchange characteristics, of plants growing in different successional stages with different soil conditions. Even though the soil mass water content (water mass/dry mass) increased from 10% to 140% with the progress of succession, the water and nitrogen content of the soil had negligible effects on the δ13C values of the observed species. The δ13C values were determined mainly by species and growth forms. We compared two morphs of S. oppositifolia, the prostrate form (P-form) and the cushion form (C-form), on the same riverbank in the glacier foreland. Regardless of the successional stage, the δ13C values of the C-form were about 2‰ more negative than those of the P-form. The ground cover area per plant mass (GA) of the C-form was less than 30% that of the P-form, and the product of GA and stomatal conductance appears to be an important factor in the relationship between transpiration and photosynthesis of a whole plant. We suggest that the relationship between GA and the root mass fraction is a crucial factor affecting the water utilization in high arctic environments. We also examined the relationship between life form and water utilization for other phototrophs, including lichens, mosses, narrow-leaved grasses, perennials, and shrubs.

Aerial dispersal of invertebrates over a high-Arctic glacier foreland: Midtre Lov�nbreen, Svalbard

Aerial dispersal of the invertebrate community was studied at seven sites along a chronosequence across the proglacial region of a retreating high-Arctic glacier, Midtre Lovenbreen, Svalbard, Norway. Invertebrates were sampled using water and sticky traps in successive summers. Large numbers of Diptera, Hymenoptera and Araneae were caught by both trap types and these groups were present at all sites, including the youngest and unvegetated site 1. Lower sticky traps (≤25 cm) caught >95% of individuals. Numbers of species tended to increase with site age. Total catch, however, often peaked at site 4 and then declined. Araneae were the exception, in which species number stabilised by site 2, but total catch increased from sites 1 to 7. Invertebrates rapidly reached newly exposed land surfaces. A few ballooning spiders were caught on upper sticky traps but evidence of wind dispersal by Collembola or mites was lacking.