Elastic deformation plays a non-negligible role in Greenland’s outlet glacier flow

Christmann, Julia; Helm, Veit; Khan, Shfaqat Abbas; Kleiner, Thomas; Müller, Ralf; Morlighem, Mathieu; Neckel, Niklas; Rückamp, Martin; Steinhage, Daniel; Zeising, Ole; Humbert, Angelika

doi:10.1038/s43247-021-00296-3

Cited by 25 publications

(38 citation statements)

References 79 publications

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“…B10). Christmann et al (2021) derived similar magnitudes in the viscoelastic simulation of 79 • North Glacier considering linearized strains. The magnitude of elastic strain in the across-flow direction is caused by the lateral compression and varies slightly to higher values around the channel due to the geometry of the channel.…”

Section: Discussionmentioning

confidence: 71%

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On the evolution of an ice shelf melt channel at the base of Filchner Ice Shelf, from observations and viscoelastic modeling

et al. 2022

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Abstract. Ice shelves play a key role in the stability of the Antarctic Ice Sheet due to their buttressing effect. A loss of buttressing as a result of increased basal melting or ice shelf disintegration will lead to increased ice discharge. Some ice shelves exhibit channels at the base that are not yet fully understood. In this study, we present in situ melt rates of a channel which is up to 330 m high and located in the southern Filchner Ice Shelf. Maximum observed melt rates are 2 m yr−1. Melt rates inside the channel decrease in the direction of ice flow and turn to freezing ∼55 km downstream of the grounding line. While closer to the grounding line melt rates are higher within the channel than outside, this relationship reverses further downstream. Comparing the modeled evolution of this channel under present-day climate conditions over 250 years with its present geometry reveals a mismatch. Melt rates twice as large as the present-day values are required to fit the observed geometry. In contrast, forcing the model with present-day melt rates results in a closure of the channel, which contradicts observations. The ice shelf experiences strong tidal variability in vertical strain rates at the measured site, and discrete pulses of increased melting occurred throughout the measurement period. The type of melt channel in this study diminishes in height with distance from the grounding line and is hence not a destabilizing factor for ice shelves.

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Section: Discussionmentioning

confidence: 71%

“…The GPS processing is similar to the method used by Christmann et al (2021). With the Waypoint GravNav 8.8 processing software, we applied a kinematic precise point positioning (PPP) processing for the GPS data that were stored in daily files.…”

Section: Global Positioning System (Gps) Processingmentioning

confidence: 99%

On the evolution of an ice shelf melt channel at the base of Filchner Ice Shelf, from observations and viscoelastic modeling

et al. 2022

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“…This may partly been due to the fact that ice is a brittle material and fractures are propagating very fast (about a third of the speed of sound), but more prominent that ice is responding to change in stress state on short time scales elastically (e.g. Christmann et al, 2021). Once a change in the calving front situation occurs the elastic stress redistribute instantaneously and can trigger further follow up events as well as lead to a modified viscous response over month-years, see Rankl et al (2017) for WIS.…”

Section: Discussionmentioning

confidence: 99%

“…Please note that no tidal correction has been applied to the 2013 and 2021 DEM's. The tidal elevation is expected to be in the range of 1 m based on the measurements of Reeh et al (2000), Christmann et al (2021) and the FES2014b ocean tide model (Lyard et al, 2006) . software (Beyer et al, 2018) to obtain a high resolution DEM and orthomosaic of the 2021 crack area.…”

Section: A4 Laser Scannermentioning

confidence: 99%

Precursor of disintegration of Greenland's largest floating ice tongue

Humbert

Helm²,

Neckel³

et al. 2022

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Abstract. The largest floating tongue of Greenland’s ice sheet, Nioghalvfjerdsbræ, has so far been relatively stable with respect to areal retreat. Curiously, it experienced significant less thinning and ice flow acceleration than its neighbour Zacharias Isbræ. Draining more than 6 % of the ice sheet, Nioghalvfjerdsbræ might become a large contributor to sea level rise in the future. Therefore, the stability of the floating tongue is a focus of this study. We employ a suite of observational methods to detect recent changes. We found that the calving style has changed at the southern part of the eastern calving front from normal tongue-type calving to a crack evolution initiated at frontal ice rises reaching 5–7 km and progressing further upstream compared to 2010. The calving front area is further weakened by a substantial increase of a zone of fragments and open water at the tongue’s southern margin, leading to the formation of a narrow ice bridge. These geometric and mechanical changes are a precursor of instability of the floating tongue. We complement our study by numerical ice flow simulations to estimate the impact of future break-up or disintegration events on the ice discharge. These idealised scenarios reveal that a loss of the south-eastern area would lead to 1 % of increase of ice discharge at the grounding line, while a sudden collapse of the frontal area (46 % of the floating tongue area) will enhance the ice discharge by 8.3 % due to loss in buttressing.

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“…On length scales considerably larger than ∼ 1 m moulins, as well as in problems where elastic flexure is more central to the geometry, elastic deformation remains important. These applications include ice shelves (e.g., Reeh et al, 2003;, large marine-terminating glaciers (Christmann et al, 2021), crevasse opening (Poinar et al, 2017), and rapid supra-and subglacial lake drainage (Dow et al, 2016(Dow et al, , 2015Lai et al, 2021).…”

Section: The Role Of Elastic Deformation In Ice Sheet Hydrologymentioning

confidence: 99%

Controls on Greenland moulin geometry and evolution from the Moulin Shape model

2022

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Abstract. Nearly all meltwater from glaciers and ice sheets is routed englacially through moulins. Therefore, the geometry and evolution of moulins has the potential to influence subglacial water pressure variations, ice motion, and the runoff hydrograph delivered to the ocean. We develop the Moulin Shape (MouSh) model, a time-evolving model of moulin geometry. MouSh models ice deformation around a moulin using both viscous and elastic rheologies and melting within the moulin through heat dissipation from turbulent water flow, both above and below the water line. We force MouSh with idealized and realistic surface melt inputs. Our results show that, under realistic surface melt inputs, variations in surface melt change the geometry of a moulin by approximately 10 % daily and over 100 % seasonally. These size variations cause observable differences in moulin water storage capacity and moulin water levels compared to a static, cylindrical moulin. Our results suggest that moulins are important storage reservoirs for meltwater, with storage capacity and water levels varying over multiple timescales. Implementing realistic moulin geometry within subglacial hydrologic models may therefore improve the representation of subglacial pressures, especially over seasonal periods or in regions where overburden pressures are high.

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Elastic deformation plays a non-negligible role in Greenland’s outlet glacier flow

Cited by 25 publications

References 79 publications

On the evolution of an ice shelf melt channel at the base of Filchner Ice Shelf, from observations and viscoelastic modeling

On the evolution of an ice shelf melt channel at the base of Filchner Ice Shelf, from observations and viscoelastic modeling

Precursor of disintegration of Greenland's largest floating ice tongue

Controls on Greenland moulin geometry and evolution from the Moulin Shape model

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