Surge-type Glaciers Research Articles

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.

Elevation changes (1949–1995) of Black Rapids Glacier, Alaska, derived from a multi-baseline InSAR DEM and historical maps

AbstractWe have constructed a new digital elevation model (DEM) of the 1995 surface of Black Rapids Glacier, a surge-type glacier in the central Alaska Range, using ERS-1/-2 repeat-pass interferometry. We isolated the topographic phase from three interferograms with contrasting perpendicular baselines. Numerous phase-unwrapping errors caused by areas of poor coherence were corrected in all three interferograms, using a novel, iterative, semi-automated approach that capitalizes on the multi-baseline nature of the dataset. Comparison of our DEM with a 1949 US Geological Survey DEM and with 1973–95 ground survey data shows the gradual return of Black Rapids Glacier to a pre-surge hypsometry following a surge in 1936/37. Maximum elevation changes along the glacier center line in the ablation and accumulation areas are, respectively, −249 and +63 m (−5.4 and +1.4 m a−1). Maximum elevation changes of survey points at nearby locations are −4.9 m a−1 (1975–84) and +0.5 m a−1 (1975–85). Center-line thickening of +62 m between 1949 and 1995 (+1.4 m a−1), just above the Loket tributary in the upper part of the ablation zone, indicates dynamic thickening following the 1936/37 surge.

Remote sensing of glacier change in West Greenland: accounting for the occurrence of surge-type glaciers

AbstractAutomated glacier mapping from thresholded band ratios of multispectral satellite data is a well-established technique to update glacier inventories over large and remote regions. The local glaciers and ice caps on Greenland are of particular interest for such efforts, as they have been only partly mapped, mainly during the 1940s–60s, and their potential contribution to global sea-level rise could be large. Here we use three Landsat ETM+ scenes from 2001 covering Disko Island (Qeqertarsuaq) and the Nuussuaq and Svartenhuk peninsulas, West Greenland, to map the glacier extent in 2001 of 1172 entities. We also manually digitize Little Ice Age (LIA) extents from clearly visible trimlines for a subsample of 500 entities. In this region with numerous surge-type glaciers, the related area-change calculation is challenging and we consider different samples with and without known surging glaciers. For the three regions the mean area changes are –28%, –20% and –23%, respectively, when known surge-type glaciers are excluded. The glaciers on smaller islands and peninsulas closer to the margin of the ice sheet show a lower mean area change of –15%. Moreover, lower (–16%) and upper (–21%) bounds are calculated for the overall area changes in the entire region between the LIA and 2001 using different upscaling assumptions. Cumulative length changes since the LIA are found to be slightly lower for surge-type glaciers.

Identification and characteristics of surge-type glaciers on Novaya Zemlya, Russian Arctic

AbstractWe present a comprehensive new inventory of surge-type glaciers on the Novaya Zemlya archipelago, using high-resolution (up to 4 m) satellite imagery from 1976/77 (Hexagon), 1989 (Landsat TM), 2001 (Landsat ETM+) and 2006 (ASTER). A total of 692 glaciers and their forelands were observed for glaciological and geomorphological criteria indicative of glacier surging (e.g. looped moraines, heavy surface crevassing, surface potholes, thrust-block moraines, concertina eskers). This enabled the identification of 32 potential surge-type glaciers (compared with four previously identified) representing 4.6% of the total but 18% by glacier area. We assess the characteristics of surge-type glaciers. Surge-type glaciers are statistically different from non-surge-type glaciers in terms of their area, length, surface slope, minimum elevation, mid-range elevation and terminus type. They are typically long (median length 18.5 km), large (median area 106.8 km2) outlet glaciers, with relatively low overall surface slopes (median slope 1.7°) and tend to terminate in water (marine or lacustrine). They are predominantly directed towards and located in the more maritime western region of the Russian Arctic, and we suggest that surge occurrence might be related to large and complex catchment areas that receive increased delivery of precipitation from the Barents Sea.

Glacier velocities across the central Karakoram

AbstractOptical matching of ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) satellite image pairs is used to determine the surface velocities of major glaciers across the central Karakoram. The ASTER images were acquired in 2006 and 2007, and cover a 60×120km region over Baltoro glacier, Pakistan, and areas to the north and west. The surface velocities were compared with differential global position system (GPS) data collected on Baltoro glacier in summer 2005. The ASTER measurements reveal fine details about ice dynamics in this region. For example, glaciers are found to be active over their termini even where they are very heavily debris-covered. The characteristics of several surge-type glaciers were measured, with terminus advances of several hundred meters per year and the displacement of trunk glaciers as surge glaciers pushed into them. This study is the first synthesis of glacier velocities across this region, and provides a baseline against which both past and future changes can be compared.

Surge of a small East Greenland glacier, 2001–2007, suggests Svalbard-type surge mechanism

Clusters of surge-type glaciers occur in many areas peripheral to the Greenland ice sheet (Weidick, 1988). In East Greenland (68–72° N), 30–70% of glaciers are of surge type, but only five of these have been described (Jiskoot and others, 2003, and references therein). Regional surge characteristics and dynamics have been used to suggest a hydrologically controlled surge mechanism, with surge behaviour that is more Alaskan-type than Svalbard-type in this region (Jiskoot and others, 2001, 2003; Murray and others, 2002, 2003; Pritchard and others, 2005).

Dynamics of a small surge-type glacier using one-dimensional geophysical inversion

AbstractWe investigate the dynamics of a small surge-type valley glacier as part of a study to characterize glacier response to climate in the Donjek Range, southwest Yukon, Canada. Pole displacements were measured using kinematic GPS techniques during three consecutive summer field seasons. Measured surface velocities range from <10 m a−1over the lower 1500 m of the 5 km long glacier to a maximum of ∼25–35 m a−1over the upper 3500 m. Basal velocities along an approximate flowline are reconstructed from the measured surface velocities using inverse methods. Control tests are used to validate the inversion scheme, and sensitivity tests are performed to evaluate the influence of the flow-law coefficient, shape factor and longitudinal averaging length. Inversion of the real data shows that basal motion accounts for 50–100% of the total surface motion along the flowline. Based on these results, and several other lines of evidence, we suggest this glacier may be undergoing a slow surge.

Submarine landforms characteristic of glacier surges in two Spitsbergen fjords

Well-preserved submarine landforms, all less than 100 years old, are imaged on high-resolution swath bathymetry obtained from Van Keulenfjorden and Rindersbukta (inner Van Mijenfjorden), Spitsbergen, Svalbard. Several tidewater glaciers in these fjords have surged in the last few hundred years. Streamlined landforms, found within the limits of known surges, are interpreted as mega-scale glacial lineations (MSGL) formed subglacially beneath actively surging ice. Large transverse ridges are terminal moraines formed by thrusting at the maximum position of glacier surges. Sediment lobes at the distal margins of terminal moraines are interpreted as glacigenic debris flows, formed either by failure of the frontal slopes of thrust moraines or from deforming sediment extruded from beneath the glacier. Sinuous ridges are eskers, formed after surge termination by the sedimentary infilling of subglacial conduits. Concordant ridges, parallel to former ice margins, are interpreted as minor push moraines, probably formed annually during winter glacier readvance. Discordant ridges, oblique to former ice margins, are interpreted as crevasse-squeeze ridges, forming when soft subglacial sediments are injected into basal crevasses. These submarine landforms have been deposited in the following sequence based on cross-cutting relationships between them, linked to stages of the surge cycle: (1) MSGL; (2a) terminal moraines and (2b) lobe-shaped debris flows; (3) isolated areas of crevasse-fill ridges; (4) eskers and (5) annual retreat ridges. A descriptive landsystem model for tidewater surge-type glaciers has been developed, whose wider applicability is emphasised by comparison with two areas in Isfjorden, Spitsbergen. The model also has a number of features in common with landsystem models for terrestrial surge-type glaciers, but is likely to be more complete since submarine landforms are particularly well preserved. The landforms discussed here may be produced and preserved in different proportions in the varied environmental settings where surging glaciers are found.

Impact of multiple glacier surges—a geomorphological map from Brúarjökull, East Iceland

Please click here to download the map associated with this article. Simultaneously with geological field investigations at the surge-type glacier Brúarjökull in August 2003, aerial photographs covering the central part of the glacier including the Kringilsárrani area were recorded with the purpose of mapping glacial landforms. A glacial geomorphological map has been completed at a scale 1:16,000 including more than 20,000 landforms from an area of c. 8 km2. Manual classification of landforms was carried out directly in stereoscopic view using a digital photogrammetric workstation taking full advantage of the texture, topography and spatial context of individual landforms. We mapped subglacial lineations such as flutes and drumlins on till plains, pitted outwash, eskers, minor meandering ridges, crevasse fill ridges, ice-free dead-ice moraine and concertina ridges, outwash fans and lake sediment plains. In addition, erosional drainage channels, ice-marginal ridges, overridden end-moraines, and extra-marginal ice wedge polygons and collapsed palsas were mapped. The mapped glacial landforms originate from at least four surges: pre-1810, 1810, 1890 and 1964. The distribution of landforms on the Brúarjökull fore-eld has close resemblance to landform assemblages of palaeo-ice streams. The present terrain surface at Brúarjökull is the cumulated result of multiple landform generations because each surge has superimposed a new association of landforms on older surfaces.

Spatial mapping of multi-year superimposed ice on the glacier Kongsvegen, Svalbard

AbstractGround-penetrating radar (GPR) and satellite ERS-2 synthetic aperture radar (SAR) are used to map the thickness and extent of the superimposed ice (SI) zone on the surge-type glacier Kongsvegen, Svalbard. GPR imagery shows sub-horizontal SI layers lying unconformably above a discrete boundary. Below this boundary, the ice has a GPR signature similar to that of ice further down-glacier in the ablation zone. This boundary is posited to represent the closing of crevasses that were created during the last surge of Kongsvegen in ∼1948. Open crevasses would have interrupted the formation of sheet layers of SI due to efficient vertical drainage of the snowpack. Aerial photographs suggest that the crevasses closed sometime in the period 1956–66. A classified SAR image from 2003 is used to delineate the extent of the SI zone. The SI extent in the SAR image agrees well with the SI zone mapped by GPR. Using the SI spatial depth distribution, we estimate the mean annual accumulation of superimposed ice to be 0.16 ± 0.06 m w.e. a−1 (locally up to 0.43 m a−1 w.e.). This corresponds to ∼15–33% of the local winter balance and ∼5–10% of the total winter balance measured since 1987.

20th-century glacier fluctuations on Disko Island (Qeqertarsuaq), Greenland

AbstractThis study assesses glacier fluctuations on Disko Island (Qeqertarsuaq), central West Greenland, during the 20th century. A total of 247 glaciers, of which 75 are classified as surge-type glaciers, are included, representing about 95% of the glacierized area. Based on expedition accounts and early maps, it is concluded that recession rates were highest during the first half of the century. Between 1953 and 2005, 70% of the glaciers showed recession, 28% remained stationary and 2% experienced overall advance due to glacier surging. The mean recession rate of quiescent surge-type glaciers was 20 ma–1 compared to 8ma–1 for normal glaciers. Identification of changes in glacier length controlled by climate changes is achieved by excluding surge-type glaciers from the dataset. The result indicates that glaciers with ablation areas facing in the arc south to northwest, covering an area above 5 km2 and having a terminus elevation below 800 m are the most climate-sensitive.

Positive mass balance during the late 20th century on Austfonna, Svalbard, revealed using satellite radar interferometry

AbstractDetermining whether increasing temperature or precipitation will dominate the cryospheric response to climate change is key to forecasting future sea-level rise. The volume of ice contained in the ice caps and glaciers of the Arctic archipelago of Svalbard is small compared with that of the Greenland or Antarctic ice sheets, but is likely to be affected much more rapidly in the short term by climate change. This study investigates the mass balance of Austfonna, Svalbard’s largest ice cap. Equilibrium-line fluxes for the whole ice cap, and for individual drainage basins, were estimated by combining surface velocities measured using satellite radar interferometry with ice thicknesses derived from radio-echo sounding. These fluxes were compared with balance fluxes to reveal that during the 1990s the total mass balance of the accumulation zone was (5.6±2.0)×108m3 a–1. Three basins in the quiescent phase of their surge cycles contributed 75% of this accumulation. The remaining volume may be attributable either to as yet unidentified surge-type glaciers, or to increased precipitation. This result emphasizes the importance of considering the surge dynamics of glaciers when attempting to draw any conclusions on climate change based on snapshot observations of the cryosphere.

Response of glaciers in northwestern North America to future climate change: an atmosphere/glacier hierarchical modeling approach

AbstractThe response of glaciers to changing climate is explored with an atmosphere/glacier hierarchical modeling approach, in which global simulations are downscaled with an Arctic MM5 regional model which provides temperature and precipitation inputs to a glacier mass-balance model. The mass balances of Hubbard and Bering Glaciers, south-central Alaska, USA, are simulated for October 1994–September 2004. The comparisons of the mass-balance simulations using dynamically-downscaled vs observed temperature and precipitation data are in reasonably good agreement, when calibration is used to minimize systematic biases in the MM5 downscalings. The responses of the Hubbard (a large tidewater glacier) and Bering (a large surge-type glacier) mass balances to the future climate scenario CCSM3 A1B, a ‘middle-of-the-road’ future climate in which fossil and non-fossil fuels are assumed to be used in balance, are also investigated for the period October 2010–September 2018. Hubbard and Bering Glaciers are projected to have increased accumulation, particularly on the upper glaciers, and greater ablation, particularly on the lower glaciers. The annual net balance for the entire Bering Glacier is projected to be significantly more negative, on average (–2.0ma–1w.e., compared to –1.3ma–1w.e. during the hindcast), and for the entire Hubbard Glacier somewhat less positive (0.3ma–1w.e. compared to 0.4 ma–1w.e. during the hindcast). The Hubbard Glacier mass balances include an estimated iceberg calving flux of 6.5 km3 a–1, which is assumed to remain constant.

Geometry change between 1990 and 2003 at Finsterwalderbreen, a Svalbard surge-type glacier, from GPS profiling

AbstractSurface mass-balance and geometry data are key to quantifying the climate response of glaciers, and confidence in data synthesis and model interpretations and forecasts requires data from as wide a range of locations and glacier types as possible. This paper presents measurements of surface elevation change at the Svalbard surge-type glacier Finsterwalderbreen, by comparing a 1990 digital elevation model (DEM) with a surface GPS profile from 2003. The pattern of elevation change is consistent with that previously noted between 1970 and 1990, and reflects the continued quiescent-phase evolution of the glacier, with mass loss in the down-glacier/receiving area of up to –1.25mw.e. a–1, and mass gain in the up-glacier/reservoir area of up to 0.60 mw.e. a–1; the area-weighted, mean change for the whole glacier is 0.19mw.e. a–1. The spatial pattern of elevation increase and decrease is complex, and the boundary between thickening and thinning determined by combining GPS and DEM data does not appear to correspond with the equilibrium-line altitude determined from surface mass-balance measurements. There is no evidence yet of a decrease in the rate of reservoir area build-up driven by mass-balance change resulting from the warmer winter air temperatures, and decreased proportion of snowfall in total precipitation, noted at meteorological stations in Svalbard.

Multivariate Controls on the Incidence of Glacier Surging in the Karakoram Himalaya

ABSTRACTSurge-type glaciers experience cyclic flow instabilities characterized by alternating periods of slow and fast flow. The geographical distribution of surge-type glaciers has been shown to be distinctly non-random in that they are clustered in some regions yet are completely absent from others. In order to identify factors that influence glacier surging, a number of environmental and glacial attributes were examined for an area in the Karakoram Himalaya, Central Asia. A new GIS-based glacier inventory was produced using a combination of ASTER and Landsat remotely sensed images and paper maps. A total of 150 glaciers were digitized, with 19 of these (12.6%) being classified as of surge-type. Attribute data for 10 glacial and environmental attributes were recorded either during the digitization phase or extracted automatically from the GIS. Simple data visualization techniques revealed a positive correlation between glacier surging and glacier length, area, perimeter size, average width, debris cover, and orientation. The use of univariate logit regression analysis showed that length, area, perimeter, average width, and the heaviest debris cover class showed significant correlation with surging. Multivariate logit regression techniques were employed to show that length, area, average width, and debris cover were all multicollinear, with the strongest statistically modeled relationship using the variable perimeter size. The significance of glacier perimeter on surging may be explained by an increased availability of avalanche-fed snow and debris material which may act as a mass balance proxy. The findings that glacier size (in particular length and perimeter) is most strongly related to surging are consistent with the findings of studies in a number of different regions.

Subglacial decoupling at the sediment/bedrock interface: a new mechanism for rapid flowing ice

On millennial or even centennial time scales, the activity of rapid flowing ice can affect climate variability and global sea level through release of meltwater into the ocean and positive feedback loops to the climate system. At the surge-type glacier Brúarjökull, an outlet of the Vatnajökull ice cap, eastern Iceland, extremely rapid ice flow was sustained by overpressurized water causing decoupling beneath a thick sediment sequence that was coupled to the glacier. This newly discovered mechanism has far reaching consequences for our understanding of fast-flowing ice and its integration with sediment discharge and meltwater release.

Ice‐cored drumlins at the surge‐type glacier Brúarjökull, Iceland: a transitional‐state landform

AbstractThis paper presents data on a glacial landform that, to our knowledge, has not previously been described in the literature: the ice‐cored drumlin. The study area is the forefield of the surge‐type glacier Brúarjökull at the northeastern margin of the Vatnajökull ice cap, East Iceland. Based on sedimentological field investigations and aerial photograph interpretation, a qualitative model for the formation of ice‐cored drumlins is proposed. The drumlin core consists of stagnant glacier ice from a previous advance and bubbly ice formed by snowdrifts, which were incorporated during the most recent advance—the 1963–64 surge. This advance deposited a mantle of basal till and streamlined the ice‐cored moraines. Till deformation and deposition on the drumlin ice‐core is facilitated by a substratum of low‐permeability ice‐cored moraines.In the present climate, the ice‐core is subject to melting and the drumlin landform will degrade. The ongoing melting of the core and re‐sedimentation of the till cover cause the originally streamlined subglacial landform to develop into a patch of hummocky moraine surrounded by a basal till sheet. Thus, ice‐cored drumlins are a transitional‐state landform in the surging glacier landsystem at Brúarjökull rather than a ‘final’ landform. Copyright © 2005 John Wiley & Sons, Ltd.

Observations of debris-rich naled associated with a major glacier surge event, Disko Island, West Greenland

Glacier naled formation is associated with surge-type glaciers both during active surging and in quiescence. During the 1995–98 surge of Kuannersuit Glacier, Disko Island, West Greenland, turbid winter runoff produced an extensive naled accretion with a distinct debris-rich stratification. After surge termination the summer occurrence of naledi gradually decreased and disappeared within 5 years. The fine-grained debris was deposited on top of outwash deposits on bars and banks. Observations at the margin of surrounding glaciers revealed that only surge-type glaciers in their quiescent phase had proglacial naled assemblages, although these lacked incorporated debris. This indicates that surge-type glaciers have a significant impact on the occurrence of naledi primarily because their subglacial thermal conditions and water storage capacity allow significant winter runoff implying high hydraulic pressure on proglacial outwash plains. Copyright © 2005 John Wiley & Sons, Ltd.

Temporal variations in flow velocity at Finsterwalderbreen, a Svalbard surge-type glacier

AbstractInter- and intra-annual velocity variations are well known on alpine glaciers, but their importance for Arctic glaciers has only been recognized more recently. This paper presents flow velocity data from Finsterwalderbreen, a 35 km2 polythermal surge-type glacier in southern Svalbard that is presently ∼100 years into its quiescent phase. Field measurements of glacier surface velocities are available from 1950-52 and 1994-97, and mean velocities for the last decade are estimated for the lower glacier using cables drilled to the glacier bed. These velocities show substantial seasonal variations indicating that basal sliding is an important component of surface velocities and interannual fluctuations of up to 75%, possibly indicating variations in subglacial water storage. Several lines of evidence indicate that this glacier has an extensive subglacial hydrological system, generally considered to be a prerequisite for surge-type glaciers, which is at least partly pressurized. Information on surface morphology from 1898 onwards shows that the glacier has experienced continuous retreat since the last surge in about 1910, and has now retreated ∼1.5 km further back than its previous pre-surge position in 1898. Tracking of moraine loops on terrestrial and aerial photographs acquired over a 100 year period indicates that the surge period of Finsterwalderbreen may be lengthening in response to climate changes.

Till genesis and glacier motion inferred from sedimentological evidence associated with the surge-type glacier, Brúarjökull, Iceland

AbstractA study employing macro- and micro-sedimentological techniques was conducted at three sites with recently deglaciated sediments in the proglacial area of Brúarjökull, a surge-type outlet glacier of the Vatnajökull ice cap, Iceland. Tills at these sites were likely deposited and deformed during the 1963/64 surge. At the height of the last surge, these sediments were beneath 90-120 m of ice, and associated basal shear stresses would have been 24-32 kPa. Tills associated with the surge at these sites formed by a combination of subglacial sediment deformation and lodgement and are thus regarded as ‘hybrid tills’. The tills show evidence of both ductile and brittle deformation. Discontinuous clay lenses within the tills, indicating local ice-bed decoupling and sliding, imply that subglacial water pressures were spatially and temporally variable during the surge. The thickness of the subglacial deforming-till layer was 50-90 cm.