Surge-type Glacier In Svalbard Research Articles

Surges in Three Svalbard Glaciers Derived from Historic Sources and Geomorphic Features

Surge-type glaciers in Svalbard are common and have been studied extensively. Whereas active phases of surges were observed and thoroughly investigated recently, data on surges in the past are limited. They are essential, however, to assess the duration of the surge cycle, to determine relation to climatic impulses, and to better understand triggering factors and the mechanism of this phenomenon. Three glaciers located in Recherchefjorden, NW Wedel Jarlsberg Land (Svalbard) were studied because they undergo the same regional climate conditions but differ by the basin’s size and morphology front types. The article employed different types of data, including geomorphological records, cartographic, graphic, and bibliographic sources. These sources permitted the determination of the location of the termini of glaciers and the quantitative and qualitative description of the rate of changes determined with computer analysis and statistical compilation. Such analysis of other data sources enabled the reconstruction of glaciers’ behavior in the past. Glacier surges in the study area correspond with this type of phenomenon in Svalbard. The results obtained showed a certain synchronization of surges in the 1820s and 1830s, the 1880s, the first half of the twentieth century, and particularly the last decade.

Over 400 previously undocumented Svalbard surge-type glaciers identified

Identifying glaciers that exhibit surge-type behavior is important when using evidence of ice front fluctuations as a proxy for reconstructing past climate oscillations. This study identifies previously undocumented surge-type glaciers in Svalbard, based on the presence of crevasse squeeze ridges in glacier forelands. Crevasse squeeze ridges are landforms suggested to be unique to surging glacier land systems. Estimates vary greatly as to the actual percentage of surge-type glaciers in Svalbard, and consequently their distribution pattern is poorly understood. A detailed survey of recent (2008–2012), high-resolution aerial imagery from TopoSvalbard, provided by the Norwegian Polar Institute, allowed for a survey of all the glacier forelands in Svalbard. Before our study, 277 individual glaciers in Svalbard have been documented to exhibit surge behavior. By using crevasse squeeze ridges as indicators of surge behavior, we have identified 431 additional glaciers that have surged. We suggest that this is a modest value as the unique surge landforms were not visible in approximately one-third of the forelands with documented surge histories. Limits to the crevasse squeeze ridge technique are presented and potential controlling factors for crevasse squeeze ridge formation/preservation are discussed.

Magnetic fabrics in the basal ice of a surge-type glacier

[1] Anisotropy of magnetic susceptibility (AMS) has been shown to provide specific useful information regarding the kinematics of deformation within subglacially deformed sediments. Here we present results from debris-rich basal glacier ice to examine deformation associated with glacier motion. Basal ice samples were collected from Tunabreen, a polythermal surge-type glacier in Svalbard. The magnetic fabrics recorded show strong correlation with structures within the ice, such as sheath folds and macroscopic stretching lineations. Thermomagnetic, low-temperature susceptibility, varying field susceptibility, and isothermal remanent magnetism acquisition experiments reveal that the debris-rich basal ice samples have a susceptibility and anisotropy dominated by paramagnetic phases within the detrital sediment. Sediment grains entrained within the basal ice are inferred to have rotated into a preferential alignment during deformation associated with flow of the glacier. An up-glacier directed plunge of magnetic lineations and subtle deviation from bulk glacier flow at the margins highlight the importance of noncoaxial strain during surge propagation. The results suggest that AMS can be used as an ice petrofabric indicator for investigations of glacier deformation and interactions with the bed.

Surface mass balance and ice flow of the glaciers Austre Lovénbreen and Pedersenbreen, Svalbard, Arctic

The glaciersAustre Lovenbreen and Pedersenbreen are located at Nylesund, Svalbard. The surface mass balance and ice flow velocity of both glaciers have been determined from the first year of observations (2005/2006), while the front edge of Austre Lovenbreen was also surveyed. The results are as follows：(1) The net mass balances of Austre Lovenbreen and Pedersenbreen are -0.44 and -0.20 m w.e., the annual ablation is -0.99 and -0.94 m w.e., and the corresponding equilibrium line altitudes are 478.10 and 494.87 m, respectively. (2) Austre Lovenbreen and Pedersenbreen are characterized as ice flow models of surge type glaciers in Svalbard. The horizontal vectors of the ice flow velocities are parallel or converge to the central lines of both glaciers, with lower velocities in the lower ablation areas and higher velocities in the middle and upper reaches of the glaciers. The vertical vectors of ice flow velocities show that there is a mass loss in the ablation areas, which reduces with increasing altitude, while there is a mass gain near the equilibrium line of Austre Lovenbreen. (3) The front edge of Austre Lovenbreen receded at an average rate of 21.83 m?a -1 , with remarkable variability a maximum rate of 77.30 m?a -1 and a minimum rate of 2.76 m?a -1 .

THE STUDIES OF SURFACE MASS BALANCE AND ICE FLOW ON GLACIERS AUSTRELOVéNBREEN AND PEDERSENBREEN,SVALBARD,ARCTIC

The glaciers Austre Lovenbreen and Pedersenbreen are located at Ny-lesund, Svalbard. Based on the observation of first year (2005/2006), surface mass balance and ice flow velocity of both glaciers have been analysed, while the front edge of Austre Lovenbreen has also been surveyed. The results are as following: (1) The net mass balance of Austre Lovenbreen and Pedersenbreen is -0.44 and -0.20 m w.e., respectively. Their annual ablation is -0.99 and -0.94 m w.e., respectively, and corresponding ELA is 478.10 and 494.87m, respectively. (2) Austre Lovenbreen and Pedersenbreen are characterized as ice flow model of surge-type glaciers in Svalbard. The level vectors of ice flow velocity are parallel or converge to the central lines of both glaciers, with slower velocities at the lower ablation area and relatively faster ones at the middle and upper part of glaciers. The mean, maximum and minimum of ice flow velocities on Austre Lovenbreen are 2.28, 3.91 and 0.81 m·a-1, and Pedersenbreen's are 6.74, 8.13 and 5.49 m·a-1. The vertical vectors of ice flow velocity show that there is a mass loss in the ablation area, which weakness with the increase of altitude, while there exists a mass gain near ELA on Austre Lovenbreen. The actual vertical displacement is in accord with the general pattern that motion is downward in the accumulation area, and is, by contrast, upward in the ablation area. (3) The front edge of Austre Lovenbreen has receded at an average rate of 21.83 m.a-1, with maximum 77.30 m.a-1 and minimum 2.76 m.a-1.

TEM PERATURE VAR IATION S AT THE GREAT WALL STATION (1985—2008) AND ZHON GSHAN STATION (1989—2008) , ANTARCTIC

The glaciers Austre Lovenbreen and Pedersenbreen are located at Ny-lesund, Svalbard. Based on the observation of first year (2005/2006), surface mass balance and ice flow velocity of both glaciers have been analysed, while the front edge of Austre Lovenbreen has also been surveyed. The results are as following: (1) The net mass balance of Austre Lovenbreen and Pedersenbreen is -0.44 and -0.20 m w.e., respectively. Their annual ablation is -0.99 and -0.94 m w.e., respectively, and corresponding ELA is 478.10 and 494.87m, respectively. (2) Austre Lovenbreen and Pedersenbreen are characterized as ice flow model of surge-type glaciers in Svalbard. The level vectors of ice flow velocity are parallel or converge to the central lines of both glaciers, with slower velocities at the lower ablation area and relatively faster ones at the middle and upper part of glaciers. The mean, maximum and minimum of ice flow velocities on Austre Lovenbreen are 2.28, 3.91 and 0.81 m·a-1, and Pedersenbreen's are 6.74, 8.13 and 5.49 m·a-1. The vertical vectors of ice flow velocity show that there is a mass loss in the ablation area, which weakness with the increase of altitude, while there exists a mass gain near ELA on Austre Lovenbreen. The actual vertical displacement is in accord with the general pattern that motion is downward in the accumulation area, and is, by contrast, upward in the ablation area. (3) The front edge of Austre Lovenbreen has receded at an average rate of 21.83 m.a-1, with maximum 77.30 m.a-1 and minimum 2.76 m.a-1.

Controls on the distribution of surge-type glaciers in Svalbard

AbstractWe analyzed the possible controls on the distribution of surge-type glaciers in Svalbard using multivariate logit models including 504 glaciers and a large number of glacial and geological attributes. Specifically we examined the potential effect of geological boundaries, mass-balance conditions and thermal regime on surging. It was found that long glaciers with relatively steep slopes overlying young fine-grained sedimentary lithologies with orientations in a broad arc clockwise from northwest to southeast are most likely to be of surge type. No relation between lithological boundaries and surge potential could be established. Possible explanations for length being conducive to surging are transport-distance-related substrate properties, distance-related attenuation of longitudinal stresses and the possible relation between thermal regime and glacier size. Analysis of glaciers with recorded radioecho sounding reveals that a polythermal regime, accumulation-area ratios close to balance and a large elevation span increase the surge potential. The logit models also enabled us to detect 19 new surge-type glaciers, to reclassify six glaciers as normal and to identify unusual surge-type glaciers. Our model results suggest that a polythermal regime and fine-grained potentially deformable beds are conducive to the surge potential of Svalbard glaciers.

Debris entrainment and transfer in polythermal valley glaciers

AbstractModes of debris entrainment and subsequent transfer in seven “normal” and five surge-type glaciers in Svalbard (76–79° N) are outlined in the context of the structural evolution of a glacier as the ice deforms during flow. Three main modes of entrainment and transfer are inferred from structural and sedimentological observations: (i) The incorporation of angular rockfall material within the stratified sequence of snow/firn/superimposed ice. This debris takes an englacial path through the glacier, becoming folded. At the margins and at the boundaries of flow units the stratified ice including debris is strongly folded, so that near the snout the debris emerges at the surface on the hinges and limbs of the folds, producing medial moraines which merge towards the snout. The resulting lines of debris are transmitted to the proglacial area in the form of regular trains of angular debris. (ii) Incorporation of debris of both supraglacial and basal character within longitudinal foliation. This is particularly evident at the surface of the glacier at the margins or at flow unit boundaries. It can be sometimes demonstrated that foliation is a product of strong folding, since it usually has an axial planar relationship with folded stratification. Foliation-parallel debris thus represents a more advanced stage of deformation than in (i). Although the presence of basal debris is problematic, it is proposed that this material is tightly folded ice derived from the bed in the manner of disharmonie folding. The readily deformed subglacial sediment or bedrock surface represents the plane of décollement. (iii) Thrusting, whereby debris-rich basal ice (including regelation ice) and subglacial sediments are uplifted into an englacial position, sometimes emerging at the ice surface. This material is much more variable in character than that derived from rockfalls, and reflects the substrate lithologies; diamicton with striated clasts and sandy gravels are the most common facies represented. Thrusting is a dynamic process, and in polythermal glaciers is probably linked mainly to the transition from sliding to frozen bed conditions. It is not therefore a solely ice-marginal or proglacial process.

Debris entrainment and transfer in polythermal valley glaciers

AbstractModes of debris entrainment and subsequent transfer in seven “normal” and five surge-type glaciers in Svalbard (76–79° N) are outlined in the context of the structural evolution of a glacier as the ice deforms during flow. Three main modes of entrainment and transfer are inferred from structural and sedimentological observations: (i) The incorporation of angular rockfall material within the stratified sequence of snow/firn/superimposed ice. This debris takes an englacial path through the glacier, becoming folded. At the margins and at the boundaries of flow units the stratified ice including debris is strongly folded, so that near the snout the debris emerges at the surface on the hinges and limbs of the folds, producing medial moraines which merge towards the snout. The resulting lines of debris are transmitted to the proglacial area in the form of regular trains of angular debris. (ii) Incorporation of debris of both supraglacial and basal character within longitudinal foliation. This is particularly evident at the surface of the glacier at the margins or at flow unit boundaries. It can be sometimes demonstrated that foliation is a product of strong folding, since it usually has an axial planar relationship with folded stratification. Foliation-parallel debris thus represents a more advanced stage of deformation than in (i). Although the presence of basal debris is problematic, it is proposed that this material is tightly folded ice derived from the bed in the manner of disharmonie folding. The readily deformed subglacial sediment or bedrock surface represents the plane of décollement. (iii) Thrusting, whereby debris-rich basal ice (including regelation ice) and subglacial sediments are uplifted into an englacial position, sometimes emerging at the ice surface. This material is much more variable in character than that derived from rockfalls, and reflects the substrate lithologies; diamicton with striated clasts and sandy gravels are the most common facies represented. Thrusting is a dynamic process, and in polythermal glaciers is probably linked mainly to the transition from sliding to frozen bed conditions. It is not therefore a solely ice-marginal or proglacial process.

Evolution of a Surge-Type Glacier in its Quiescent Phase: Kongsvegen, Spitsbergen, 1964–95

AbstractKongsvegen is a 102 km2sub-polar (polythermal) surge-type glacier in northwest Spitsbergen, Svalbard. It surged just before 1948 and is currently in its quiescent phase. Measurements of surface geometry since 1966 show a retreat of the front and strong thinning of up to 75 m in the ablation area, and a build-up of up to 32 m in the accumulation area. Present-day annual velocities along the glacier are low, from 1.4 up to 3.6 m a-1. The measured mean net balance for the period 1987-94 and the balance reconstructed back to 1967 show a weak positive balance of about 0.1 m w.e. The measured actual ice flux is low and the mass transfer down-glacier at the ELA is only about 3-20% of that required for steady state. Thus, the glacier is building up towards a new surge. The total thickening rate on Kongsvegen is somewhat higher than in other cases from Svalbard, but it is small compared with other well-studied surge-type glaciers in Alaska and the Pamirs. This relatively low rate of change is a function of the low accumulation rate and the relatively cold climate compared to other areas and is common for surge-type glaciers in Svalbard.

Evolution of a Surge-Type Glacier in its Quiescent Phase: Kongsvegen, Spitsbergen, 1964–95

AbstractKongsvegen is a 102 km2 sub-polar (polythermal) surge-type glacier in northwest Spitsbergen, Svalbard. It surged just before 1948 and is currently in its quiescent phase. Measurements of surface geometry since 1966 show a retreat of the front and strong thinning of up to 75 m in the ablation area, and a build-up of up to 32 m in the accumulation area. Present-day annual velocities along the glacier are low, from 1.4 up to 3.6 m a-1. The measured mean net balance for the period 1987-94 and the balance reconstructed back to 1967 show a weak positive balance of about 0.1 m w.e. The measured actual ice flux is low and the mass transfer down-glacier at the ELA is only about 3-20% of that required for steady state. Thus, the glacier is building up towards a new surge. The total thickening rate on Kongsvegen is somewhat higher than in other cases from Svalbard, but it is small compared with other well-studied surge-type glaciers in Alaska and the Pamirs. This relatively low rate of change is a function of the low accumulation rate and the relatively cold climate compared to other areas and is common for surge-type glaciers in Svalbard.

Quiescent-phase changes in velocity and geometry of Finsterwalderbreen, a surge-type glacier in Svalbard

Finsterwalderbreen is a 35 km2, polythermal glacier in southern Spitsbergen, which last surged at around the start of the 20th century, and is still in the quiescent phase. Surface elevations measured several times since 1898 show strong thinning and retreat at the front, and gradual build-up in the accumulation area. Present-day annual velocities increase from about 1 m a–1 at the snout to a maximum of 13 m a–1 near the equilibrium line, then drop to 5 m a–1 at the bergschrund. Summer velocities are higher than the annual average, and winter velocities are lower (10–60% of summer velocities, where both are measured over several months). Velocities measured along the glacier centre line in 1950–52 are higher than those measured in 1994–95 in the upper basin, but are lower in the ablation area, which may be attributable to changes in surface profile on recovery from the surge. The measured modern ice flux (≈2.5 x 10–3 km3 a–1 w.e.) is only about 60% of the flux required to maintain balance (≈4.1 x 10–3 km3 a–1 w.e.), as determined from continuing mass-balance studies. Multi-frequency radar profiles show that most of the glacier is at the pressure-melting point at the base. This is consistent with hydrological studies showing high suspended-sediment loads, and hydro-chemical evidence of high sulphate levels, both indicating a well-developed basal drainage system during the summer which probably accounts for the seasonal velocity variations. Since the glacier still has a temperate bed, and appears to be building up in the accumulation area, it may be developing towards another surge.

The rate of chemical weathering beneath a quiescent, surge-type, polythermal-based glacier, southern Spitsbergen, Svalbard

Glacierized basins in the high Arctic are believed to be regions of low chemical weathering rates, despite the lack of pertinent data, because it is believed that water does not flow in significant quantities through subglacial drainage systems. We have calculated chemical weathering rates at Finsterwalderbreen, a polythermal, surge-type glacier in Svalbard. Rates of 320 and 150 meq Σ+ m−1 year−1 were measured in 1994 and 1995, respectively. The corresponding water fluxes were 4.1 × 107 and 1.7 × 107 m3. We estimate that we have measured ~72% of the total annual discharge, hence the true annual chemical weathering rates are ~440 and 210 meq Σ+ m−2 year−1, respectively This gives a mean annual chemical weathering rate of 330 meq Σ+ m−2 year−1, which approximates the continental average of 390 meq Σ+ m−2 year−1 and is intermediate between chemical weathering rates measured on cold-based glaciers (~110–160 meq Σ+ m−2 year−1) and temperate glaciers (450–1000 meq Σ+ m−2 year−1). This suggests that there may be a direct link between chemical weathering rates and thermal regime, and that glacierized basins in the high Arctic cannot necessarily be considered as regions of low chemical weathering and CO2 drawdown.

Quiescent-phase changes in velocity and geometry of Finsterwalderbreen, a surge-type glacier in Svalbard

Finsterwalderbreen is a 35 km2, polythermal glacier in southern Spitsbergen, which last surged at around the start of the 20th century, and is still in the quiescent phase. Surface elevations measured several times since 1898 show strong thinning and retreat at the front, and gradual build-up in the accumulation area. Present-day annual velocities increase from about 1 m a–1 at the snout to a maximum of 13 m a–1 near the equilibrium line, then drop to 5 m a–1 at the bergschrund. Summer velocities are higher than the annual average, and winter velocities are lower (10–60% of summer velocities, where both are measured over several months). Velocities measured along the glacier centre line in 1950–52 are higher than those measured in 1994–95 in the upper basin, but are lower in the ablation area, which may be attributable to changes in surface profile on recovery from the surge. The measured modern ice flux (≈2.5 x 10–3 km3 a–1 w.e.) is only about 60% of the flux required to maintain balance (≈4.1 x 10–3 km3 a–1 w.e.), as determined from continuing mass-balance studies. Multi-frequency radar profiles show that most of the glacier is at the pressure-melting point at the base. This is consistent with hydrological studies showing high suspended-sediment loads, and hydro-chemical evidence of high sulphate levels, both indicating a well-developed basal drainage system during the summer which probably accounts for the seasonal velocity variations. Since the glacier still has a temperate bed, and appears to be building up in the accumulation area, it may be developing towards another surge.

The rate of chemical weathering beneath a quiescent, surge-type, polythermal-based glacier, southern Spitsbergen, Svalbard

Glacierized basins in the high Arctic are believed to be regions of low chemical weathering rates, despite the lack of pertinent data, because it is believed that water does not flow in significant quantities through subglacial drainage systems. We have calculated chemical weathering rates at Finsterwalderbreen, a polythermal, surge-type glacier in Svalbard. Rates of 320 and 150 meq Σ+ m−1 year−1 were measured in 1994 and 1995, respectively. The corresponding water fluxes were 4.1 × 107 and 1.7 × 107 m3. We estimate that we have measured ~72% of the total annual discharge, hence the true annual chemical weathering rates are ~440 and 210 meq Σ+ m−2 year−1, respectively This gives a mean annual chemical weathering rate of 330 meq Σ+ m−2 year−1, which approximates the continental average of 390 meq Σ+ m−2 year−1 and is intermediate between chemical weathering rates measured on cold-based glaciers (~110–160 meq Σ+ m−2 year−1) and temperate glaciers (450–1000 meq Σ+ m−2 year−1). This suggests that there may be a direct link between chemical weathering rates and thermal regime, and that glacierized basins in the high Arctic cannot necessarily be considered as regions of low chemical weathering and CO2 drawdown.

The duration of the active phase on surge-type glaciers: contrasts between Svalbard and other regions

AbstractMany glaciers in Svalbard and in other glacierized areas of the world are known to surge. However, the time series of observations required to assess the duration of fast motion is very restricted. Data on active-phase duration in Svalbard come from aerial photographs, satellite imagery, field surveys and airborne reconnaissance. Evidence on surge duration is available for eight Svalbard ice masses varying from 3 to 1250 km2. Worldwide, active-phase duration is recorded for less than 50 glaciers. Few observations are available on high polar ice masses. The duration of the active phase is significantly longer for Svalbard glaciers than for surge-type glaciers in other areas from which data are available. In Svalbard, the active phase may last from 3 to 10 years. By contrast, a surge duration of 1–2 years is more typical of ice masses in northwest North America, Iceland and the Pamirs. Ice velocities during the protracted active phase on Svalbard glaciers are considerably lower than those for many surge-type glaciers in these other regions. Mass is transferred down-glacier more slowly but over a considerably longer period. Svalbard surge-type glaciers do not exhibit the very abrupt termination of the active phase, over periods of a few days, observed for several Alaskan glaciers. The duration of the active phase in Svalbard is not dependent on parameters related to glacier size. The quiescent phase is also relatively long (50–500 years) for Svalbard ice masses. Detailed field monitoring of changing basal conditions through the surge cycle is required from surge-type glaciers in Svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago, which may also typify other high polar ice masses. The finding that surge behaviour, in the form of active-phase duration, shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges.

The duration of the active phase on surge-type glaciers: contrasts between Svalbard and other regions

AbstractMany glaciers in Svalbard and in other glacierized areas of the world are known to surge. However, the time series of observations required to assess the duration of fast motion is very restricted. Data on active-phase duration in Svalbard come from aerial photographs, satellite imagery, field surveys and airborne reconnaissance. Evidence on surge duration is available for eight Svalbard ice masses varying from 3 to 1250 km2. Worldwide, active-phase duration is recorded for less than 50 glaciers. Few observations are available on high polar ice masses. The duration of the active phase is significantly longer for Svalbard glaciers than for surge-type glaciers in other areas from which data are available. In Svalbard, the active phase may last from 3 to 10 years. By contrast, a surge duration of 1–2 years is more typical of ice masses in northwest North America, Iceland and the Pamirs. Ice velocities during the protracted active phase on Svalbard glaciers are considerably lower than those for many surge-type glaciers in these other regions. Mass is transferred down-glacier more slowly but over a considerably longer period. Svalbard surge-type glaciers do not exhibit the very abrupt termination of the active phase, over periods of a few days, observed for several Alaskan glaciers. The duration of the active phase in Svalbard is not dependent on parameters related to glacier size. The quiescent phase is also relatively long (50–500 years) for Svalbard ice masses. Detailed field monitoring of changing basal conditions through the surge cycle is required from surge-type glaciers in Svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago, which may also typify other high polar ice masses. The finding that surge behaviour, in the form of active-phase duration, shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges.