Seasonal Surface-Velocity Variations on a Sub-Polar Glacier in West Greenland

Andreasen, Jørn-Ole

doi:10.3189/s0022143000006651

Cited by 15 publications

(22 citation statements)

References 24 publications

(24 reference statements)

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“…H odge, 1974;Iken, 1978) but a lso in pola r regions such as Al as ka (R aymond a nd H a rriso n, 1988), Arctic Canada (Iken, 1974) a nd Greenland (e.g. Paterso n, 1961Andreasen, 1985). It was not, however, observed on th e fast-m oving J a kobshav ns Isbne in West Greenland (Echelmeyer a nd H arrison, 1990).…”

Section: Discussionmentioning

confidence: 99%

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

1997

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ABSTRACT. Finsterwalderbreen is a 35 km 2 , poly thermal glacier in southern Spitsbergen, which last surged at around the start of the 20th century, and is stil l 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 I at the snout to a maximum of 13 m a I near the equilibrium line, then drop to 5 m a-I 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 nux (~2.5 x 10 3 km 3 a Iw.e.) is only about 60% of the nux required to maintain balance (~4.1 x 10 3 km 3 a -I 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 hydrochemical 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.

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Section: Discussionmentioning

confidence: 99%

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

1997

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“…Subglacial discharge (Qsg) is confined to the lowest two cells near the bottom. Horizontal and vertical resolution at the glacier front are 10 m. of the seasonal surface runoff is discharged at the base of the glacier through a series of drainage channels [Andreasen, 1985;Zwally et al, 2002;Das et al, 2008;Catania et al, 2008].…”

Section: Model Setupmentioning

confidence: 99%

Seasonal variability of submarine melt rate and circulation in an East Greenland fjord

et al. 2013

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[1] The circulation in a glacial fjord driven by a large tidewater glacier is investigated using a nonhydrostatic ocean general circulation model with a melt rate parameterization at the vertical glacier front. The model configuration and water properties are based on data collected in Sermilik Fjord near Helheim Glacier, a major Greenland outlet glacier. The approximately two-layer stratification of the fjord's ambient waters causes the meltwater plume at the glacier front to drive a "double cell" circulation with two distinct outflows, one at the free surface and one at the layers' interface. In summer, the discharge of surface runoff at the base of the glacier (subglacial discharge) causes the circulation to be much more vigorous and associated with a larger melt rate than in winter. The simulated "double cell" circulation is consistent, in both seasons, with observations from Sermilik Fjord. Seasonal differences are also present in the vertical structure of the melt rate, which is maximum at the base of the glacier in summer and at the layers' interface in winter. Simulated submarine melt rates are strongly sensitive to the amount of subglacial discharge, to changes in water temperature, and to the height of the layers. They are also consistent with those inferred from simplified one-dimensional models based on the theory of buoyant plumes. Our results also indicate that to correctly represent the dynamics of the meltwater plume, care must be taken in the choice of viscosity and diffusivity values in the model. Citation: Sciascia, R., F. Straneo, C. Cenedese, and P. Heimbach (2013), Seasonal variability of submarine melt rate and circulation in an East Greenland fjord,

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“…As argued in recent studies, one of the largest seasonal controls on the fjord's circulation and submarine melting is subglacial discharge (Qsg) [Motyka et al, 2003;Jenkins, 2011;Xu et al, 2012;Sciascia et al, 2013]. In summer, a fraction of the surface runoff reaches the bed of Greenland's glaciers and is discharged at depth into the fjord [Andreasen, 1985;Zwally et al, 2002;Catania et al, 2008;Das et al, 2008]. Geothermal melting and frictional melting at the base of the glacier are present throughout the year but are a small fraction ($8%) of the total subglacial discharge [Mernild et al, 2010].…”

Section: Initial Conditions-seasonal Variabilitymentioning

confidence: 99%

Impact of periodic intermediary flows on submarine melting of a Greenland glacier

et al. 2014

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The submarine melting of a vertical glacier front, induced by an intermediary circulation forced by periodic density variations at the mouth of a fjord, is investigated using a nonhydrostatic ocean general circulation model and idealized laboratory experiments. The idealized configurations broadly match that of Sermilik Fjord, southeast Greenland, a largely two layers system characterized by strong seasonal variability of subglacial discharge. Consistent with observations, the numerical results suggest that the intermediary circulation is an effective mechanism for the advection of shelf anomalies inside the fjord. In the numerical simulations, the advection mechanism is a density intrusion with a velocity which is an order of magnitude larger than the velocities associated with a glacier-driven circulation. In summer, submarine melting is mostly influenced by the discharge of surface runoff at the base of the glacier and the intermediary circulation induces small changes in submarine melting. In winter, on the other hand, submarine melting depends only on the water properties and velocity distribution at the glacier front. Hence, the properties of the waters advected by the intermediary circulation to the glacier front are found to be the primary control of the submarine melting. When the density of the intrusion is intermediate between those found in the fjord's two layers, there is a significant reduction in submarine melting. On the other hand, when the density is close to that of the bottom layer, only a slight reduction in submarine melting is observed. The numerical results compare favorably to idealized laboratory experiments with a similar setup.

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Seasonal Surface-Velocity Variations on a Sub-Polar Glacier in West Greenland

Cited by 15 publications

References 24 publications

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

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

Seasonal variability of submarine melt rate and circulation in an East Greenland fjord

Impact of periodic intermediary flows on submarine melting of a Greenland glacier

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