Seismic evidence for complex sedimentary control of Greenland Ice Sheet flow

Kulessa, Bernd; Hubbard, Alun; Booth, Adam; Bougamont, Marion; Dow, Christine F.; Doyle, Samuel; Christoffersen, Poul; Lindbäck, Katrin; Pettersson, Rickard; Fitzpatrick, A.; Jones, Glenn

doi:10.1126/sciadv.1603071

Cited by 49 publications

(65 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The basal traction τ b time series was calculated using the Mohr‐Coulomb failure criterion that describes the plastic shear strength of the porous layer that underlies Store Glacier (Hofstede et al, ) and several other glaciers in Greenland (Booth et al, ; Bougamont et al, ; Christianson et al, ; Dow et al, ; Kulessa et al, ; Walter et al, ). The Mohr‐Coulomb failure criterion is expressed as (equation 12 of Christoffersen & Tulaczyk, ):

τ_{b} = c_{0} + N \tan μ,

where c 0 is the apparent cohesion, N = p i − p w the effective normal stress (the pressure at the ice‐bed interface), and μ the sediment internal friction angle.…”

Section: Methodsmentioning

confidence: 99%

Physical Conditions of Fast Glacier Flow: 3. Seasonally‐Evolving Ice Deformation on Store Glacier, West Greenland

et al. 2019

Self Cite

View full text Add to dashboard Cite

Temporal variations in ice sheet flow directly impact the internal structure within ice sheets through englacial deformation. Large‐scale changes in the vertical stratigraphy within ice sheets have been previously conducted on centennial to millennial timescales; however, intra‐annual changes in the morphology of internal layers have yet to be explored. Over a period of 2 years, we use autonomous phase‐sensitive radio‐echo sounding to track the daily displacement of internal layers on Store Glacier, West Greenland, to millimeter accuracy. At a site located ∼30 km from the calving terminus, where the ice is ∼600 m thick and flows at ∼700 m/a, we measure distinct seasonal variations in vertical velocities and vertical strain rates over a 2‐year period. Prior to the melt season (March–June), we observe increasingly nonlinear englacial deformation with negative vertical strain rates (i.e., strain thinning) in the upper half of the ice column of approximately −0.03 a−1, whereas the ice below thickens under vertical strain reaching up to +0.16 a−1. Early in the melt season (June–July), vertical thinning gradually ceases as the glacier increasingly thickens. During late summer to midwinter (August–February), vertical thickening occurs linearly throughout the entire ice column, with strain rates averaging 0.016 a−1. We show that these complex variations are unrelated to topographic setting and localized basal slip and hypothesize that this seasonality is driven by far‐field perturbations in the glacier's force balance, in this case generated by variations in basal hydrology near the glacier's terminus and propagated tens of kilometers upstream through transient basal lubrication longitudinal coupling.

show abstract

τ_{b} = c_{0} + N \tan μ,

where c 0 is the apparent cohesion, N = p i − p w the effective normal stress (the pressure at the ice‐bed interface), and μ the sediment internal friction angle.…”

Section: Methodsmentioning

confidence: 99%

Physical Conditions of Fast Glacier Flow: 3. Seasonally‐Evolving Ice Deformation on Store Glacier, West Greenland

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Recent evidence [73][74][75] suggests that parts of the ice sheet are underlain by subglacial sediments. In such areas, efficient drainage where it exists is likely to be characterised by channels (or 'canals' [2]) incised both down in to the sediments as well as up into the ice, while inefficient drainage may occur via Darcian flow through the sediments [2].…”

Section: Subglacial Meltwater Processesmentioning

confidence: 99%

“…In such areas, efficient drainage where it exists is likely to be characterised by channels (or 'canals' [2]) incised both down in to the sediments as well as up into the ice, while inefficient drainage may occur via Darcian flow through the sediments [2]. Bougamont et al [76] used an ice flow model incorporating a deformable sediment bed to show that observed temporal variations in ice flow could be explained by changes in the strength of subglacial sediment due to seasonal influxes of surface-derived meltwaters; three~2-km long seismic profiles from south-west GrIS [75] also suggest that ice flow velocity scales with local subglacial sediment strength (but also with surface meltwater input). Nevertheless, there is as yet no empirical evidence for pervasive subglacial sediment cover [77,78], in particular beneath the slower flowing land-terminating sections of the ice sheet, so the importance of associated ice dynamical impacts remains unknown.…”

Section: Subglacial Meltwater Processesmentioning

confidence: 99%

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Nienow

Sole

Slater

et al. 2017

Curr Clim Change Rep

100

View full text Add to dashboard Cite

Purpose of the Review This review discusses the role that meltwater plays within the Greenland ice sheet system. The ice sheet's hydrology is important because it affects mass balance through its impact on meltwater runoff processes and ice dynamics. The review considers recent advances in our understanding of the storage and routing of water through the supraglacial, englacial, and subglacial components of the system and their implications for the ice sheet. Recent Findings There have been dramatic increases in surface meltwater generation and runoff since the early 1990s, both due to increased air temperatures and decreasing surface albedo. Processes in the subglacial drainage system have similarities to valley glaciers and in a warming climate, the efficiency of meltwater routing to the ice sheet margin is likely to increase. The behaviour of the subglacial drainage system appears to limit the impact of increased surface melt on annual rates of ice motion, in sections of the ice sheet that terminate on land, while the large volumes of meltwater routed subglacially deliver significant volumes of sediment and nutrients to downstream ecosystems. Summary Considerable advances have been made recently in our understanding of Greenland ice sheet hydrology and its wider influences. Nevertheless, critical gaps persist both in our understanding of hydrology-dynamics coupling, notably at tidewater glaciers, and in runoff processes which ensure that projecting Greenland's future mass balance remains challenging.

show abstract

“…Furthermore, as we 5 hypothetise an identical basal drag over time, we underestimate the acceleration of the ice flow of the glaciers due to the basal lubrification coming from meltwater or rainfall percolation at depth and reaching the bedrock (Kulessa et al, 2017). An other limit of the GRISLI model is its simple representation of the grounding line position and thus of the buttressing effect which could impact the ice dynamics (Gagliardini et al, 2010).…”

Section: Limits Of the Modelsmentioning

confidence: 99%

Assessment of the Greenland ice sheet – atmosphere feedbacks for the next century with a regional atmospheric model fully coupled to an ice sheet model

clec’h¹,

Fettweis²,

Quiquet³

et al. 2017

Preprint

View full text Add to dashboard Cite

Abstract. In the context of global warming, the projected Greenland sea level rise contribution is mainly controlled by the interactions between the Greenland ice sheet (GrIS) and the atmosphere, in particular through the temperature and surface mass balance -elevation feedback. In order to evaluate the importance of these feedbacks, we used three methods to represent the interactions between the GrIS model GRISLI and the polar regional atmosphere model MAR, under the RCP 8.5 scenario from 2020 to 2150. In the simplest method, there is no coupling, MAR computes varying atmospheric conditions using a constant 5 GrIS geometry (topography and extent) set to observations and GRISLI is forced by these results. The second is a one-way coupling method which represents the interactions by correcting offline the MAR outputs to account for topography changes computed by GRISLI. The third method is a full two-way coupling in which the ice sheet topography and extent seen by the atmospheric model evolve after each ice sheet model time step. Due to the ice sheet elevation feedback, the two-way coupling method amplifies the projected decrease in surface mass balance, the increase in surface temperature and the GrIS surface 10 thinning for the coastal regions, compared to the no coupling method. Compared to both the one-way and the no coupling methods, the two-way coupling allows the changes of fine scale processes to be represented, such as the increase in katabatic winds over the coast. As a consequence, in 2150, the two-way coupling method computes a GrIS melting contribution to sea level rise 9.3 % larger than the no coupling method, and 2.5 % larger than the one-way coupling methods. After 150 years, the GrIS extent seen by MAR in the two-way method is 52 400 km 2 lower than with the no coupling method. Furthermore, 15 in 2150, using a fix ice sheet mask, as in the no coupling method, overestimates by 24 % the SLR contribution from SMB compared to the use of the ice sheet mask as simulated in the two-way method. Beyond the century time-scale, a two-way method becomes necessary in order to avoid an underestimation of the projected ice sheet volume, topography and ice extent reduction. The one-way coupling method however seems to be sufficient to represent the interactions for projections until the end of the 21 st century. The no coupling method always underestimates the projected ice sheet volume loss significantly due 20 to the lack of feedback between the GrIS and the atmosphere. 1The Cryosphere Discuss., https://doi

show abstract

Seismic evidence for complex sedimentary control of Greenland Ice Sheet flow

Abstract: Seismic data show that subglacial sediment slip causes a complex flow response of the Greenland Ice Sheet to climate warming.

Cited by 49 publications

References 61 publications

Physical Conditions of Fast Glacier Flow: 3. Seasonally‐Evolving Ice Deformation on Store Glacier, West Greenland

Physical Conditions of Fast Glacier Flow: 3. Seasonally‐Evolving Ice Deformation on Store Glacier, West Greenland

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Assessment of the Greenland ice sheet – atmosphere feedbacks for the next century with a regional atmospheric model fully coupled to an ice sheet model

Contact Info

Product

Resources

About