Subglacial topography, ice thickness, and bathymetry of
Kongsfjorden, northwestern Svalbard

Lindbäck, Katrin; Kohler, Jack; Pettersson, R.; Nuth, C.; Langley, Kirsty; Messerli, Alexandra; Vallot, Dorothée; Matsuoka, Kenichi; Brandt, O.

doi:10.5194/essd-2018-37

Cited by 9 publications

(21 citation statements)

References 25 publications

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“…Close to the subglacial discharge locations, a changing grounding-line fan of sediments has been observed (Trusel et al, 2010), potentially ensuring a pinning point if the glacier were to advance in the future. Luckman et al (2015) showed that calving rates are strongly correlated with subsurface fjord temperatures, indicating that the dominant control on calving is melt undercutting, followed by collapse of the sub-aerial part.…”

Section: Study Areamentioning

confidence: 99%

“…The glacier front position undergoes seasonal oscillations, showing advance during the winter and spring followed by retreat in the summer and autumn. Since 2011, the summer retreat has outpaced the winter advance, with an overall net retreat of ∼ 2 km between 2011 and 2015 after a relatively stable period since the 1990s (Schellenberger et al, 2015;Luckman et al, 2015;Köhler et al, 2016). Velocities at the front can reach 5 m d −1 in the summer with large seasonal and annual variations associated with basal sliding velocity .…”

Section: Study Areamentioning

confidence: 99%

“…The initial surface topography includes different available surface digital elevation models (DEMs) and is described in Vallot et al (2017). Ice surface velocities were derived from feature tracking of TerraSAR-X image pairs in slant range using correlation windows of 200 × 200 pixels at every 20 pixels, and subsequently ortho-rectified to a pixel size of 40 m using a DEM (Luckman et al, 2015). Images were acquired roughly every 11 days for the period May-October 2013.…”

Section: Observed Geometry Surface Velocities and Front Positionsmentioning

confidence: 99%

“…Buoyant meltwater plumes entrain warm ocean water (Jenkins, 2011) and are thought to enhance melt undercutting (Slater et al, 2015) at the ice cliff triggering collapse of the ice above. Luckman et al (2015) investigated controls on seasonal variations in calving rates and showed that calving variations at Kronebreen, the glacier this study focuses on, are strongly correlated with sub-surface ocean temperature changes linked to melt undercutting of the calving front. However, direct measurements of oceanic properties, ice dynamics, frontal geometries and mean volumetric frontal ablation rates are still too scarce to quantify the relationship between ocean processes, subglacial discharge and ice dynamics and one must rely on modelling.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, it has been suggested that ocean warming could play an important role in determining glacier calving rate and acceleration, by impacting submarine melt rates (D. M. Luckman et al, 2015). Straneo and Heimbach (2013) proposed two mechanisms responsible for the increase of submarine melt rates at the ice-ocean interface in Greenland: a warmer and thicker layer of Atlantic water in the fjords and an increase in subglacial discharge mainly during summer and autumn.…”

Section: Introductionmentioning

confidence: 99%

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Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard

et al. 2018

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Abstract. In this paper, we study the effects of basal friction, sub-aqueous undercutting and glacier geometry on the calving process by combining six different models in an offlinecoupled workflow: a continuum-mechanical ice flow model (Elmer/Ice), a climatic mass balance model, a simple subglacial hydrology model, a plume model, an undercutting model and a discrete particle model to investigate fracture dynamics (Helsinki Discrete Element Model, HiDEM). We demonstrate the feasibility of reproducing the observed calving retreat at the front of Kronebreen, a tidewater glacier in Svalbard, during a melt season by using the output from the first five models as input to HiDEM. Basal sliding and glacier motion are addressed using Elmer/Ice, while calving is modelled by HiDEM. A hydrology model calculates subglacial drainage paths and indicates two main outlets with different discharges. Depending on the discharge, the plume model computes frontal melt rates, which are iteratively projected to the actual front of the glacier at subglacial discharge locations. This produces undercutting of different sizes, as melt is concentrated close to the surface for high discharge and is more diffuse for low discharge. By testing different configurations, we show that undercutting plays a key role in glacier retreat and is necessary to reproduce observed retreat in the vicinity of the discharge locations during the melting season. Calving rates are also influenced by basal friction, through its effects on near-terminus strain rates and ice velocity.

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Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Observed Geometry Surface Velocities and Front Positionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard

et al. 2018

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Biogeochemistry and microbiology of high Arctic marine sediment ecosystems—Case study of Svalbard fjords

Jørgensen

Laufer

Michaud

et al. 2020

Limnology & Oceanography

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Fjord ecosystems of the high Arctic are distinct from fjords of temperate latitudes due to the influence of glaciers, icebergs, sea ice, and the permanently low temperatures. The sediment microbiology and biogeochemical processes were analyzed during an international research program with multiple field studies in Svalbard, situated between the Barents Sea and the Arctic Ocean. We here describe the physical and geochemical setting and the predominant microbiological processes in several fjords. Physiological studies of sediments and pure cultures show how the predominantly psychrophilic bacteria are adapted to the near‐zero temperature. The microbial communities include bacteria responsible for organic matter hydrolytic degradation, fermentation, and terminal oxidation to CO2. These processes drive the cycling of carbon, sulfur, iron, and manganese. The balance between the dominant sediment microbial processes changes along transects out through the fjords, reflecting the varying impact of the glacier‐derived rock flour, rich in metal oxides at the head, and the plankton‐derived, labile, marine organic matter at the mouth. Due to accelerated warming of Arctic ecosystems, glaciers are retreating with impacts on the physical, chemical, and biological functioning of the fjord sediment ecosystems.

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Subglacial sediment distribution from constrained seismic inversion, using MuLTI software: examples from Midtdalsbreen, Norway

et al. 2019

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Fast ice flow is associated with the deformation of subglacial sediment. Seismic shear velocities, Vs, increase with the rigidity of material and hence can be used to distinguish soft sediment from hard bedrock substrates. Depth profiles of Vs can be obtained from inversions of Rayleigh wave dispersion curves, from passive or active-sources, but these can be highly ambiguous and lack depth sensitivity. Our novel Bayesian transdimensional algorithm, MuLTI, circumvents these issues by adding independent depth constraints to the inversion, also allowing comprehensive uncertainty analysis. We apply MuLTI to the inversion of a Rayleigh wave dataset, acquired using active-source (Multichannel Analysis of Surface Waves) techniques, to characterise sediment distribution beneath the frontal margin of Midtdalsbreen, an outlet of Norway's Hardangerjøkulen ice cap. Ice thickness (0-20 m) is constrained using co-located GPR data. Outputs from MuLTI suggest that partly-frozen sediment (Vs 500-1000 m s −1 ), overlying bedrock (Vs 2000-2500 m s −1 ), is present in patches with a thickness of ∼4 m, although this approaches the resolvable limit of our Rayleigh wave frequencies (14-100 Hz). Uncertainties immediately beneath the glacier bed are <280 m s −1 , implying that MuLTI cannot only distinguish bedrock and sediment substrates but does so with an accuracy sufficient for resolving variations in sediment properties.

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Subglacial topography, ice thickness, and bathymetry of Kongsfjorden, northwestern Svalbard

Cited by 9 publications

References 25 publications

Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard

Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard

Biogeochemistry and microbiology of high Arctic marine sediment ecosystems—Case study of Svalbard fjords

Subglacial sediment distribution from constrained seismic inversion, using MuLTI software: examples from Midtdalsbreen, Norway

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