Simulated retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry

Steiger, Nadine; Nisancioglu, Kerim H.; Åkesson, Henning; Fleurian, Basile de; Nick, F. M.

doi:10.5194/tc-12-2249-2018

Cited by 15 publications

(14 citation statements)

References 95 publications

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“…Terminus positions are taken from a number of published sources (Fig. 2, Table S1, Andresen et al, 2012;Steiger et al, 2018;5 Lea et al, 2014;Haubner et al, 2018;Catania et al, 2018;Cowton et al, 2018;Moon and Joughin, 2008;Joughin et al;Bunce et al, 2018;Carr et al, 2017). Broadly, these records can be organised into long records from a handful of individual glaciers, and shorter satellite-era records from almost all significant tidewater glaciers in Greenland (Figs 2a and 2b).…”

Section: Terminus Positionsmentioning

confidence: 99%

Past and future response of Greenland's tidewater glaciers to submarine melting

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Straneo

Felikson

et al. 2019

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The effect of the North Atlantic Ocean on the Greenland Ice Sheet through submarine melting of Greenland's tidewater glacier calving fronts is thought to be a key driver of widespread glacier retreat, dynamic mass loss and sea level contribution from the ice sheet. Despite its critical importance, problems of process complexity and scale hinder efforts to represent the influence of submarine melting in ice sheet-scale models. Here we propose parameterizing tidewater glacier terminus position as a simple linear function of submarine melting, with submarine melting in turn estimated as a function 5 of subglacial runoff and ocean temperature. The relationship is tested, calibrated and validated using datasets of terminus position, runoff and ocean temperature covering the full ice sheet and surrounding ocean from the period 1960-present. We demonstrate a statistically significant link between multi-decadal tidewater glacier terminus position and submarine melting and show that the proposed parameterisation has predictive power when considering a population of glaciers. An illustrative 21st century projection is considered suggesting that tidewater glaciers in Greenland will undergo little further retreat in a low 10 emissions RCP2.6 scenario. In contrast, a high emissions RCP8.5 scenario results in a median retreat of ∼6 km, with 35% of glaciers experiencing retreat exceeding 10 km. Our study provides a long-term and ice sheet-wide assessment of the sensitivity of tidewater glaciers to submarine melting and proposes a practical and empirically validated means of incorporating ocean forcing into models of the Greenland ice sheet.

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Section: Terminus Positionsmentioning

confidence: 99%

Past and future response of Greenland's tidewater glaciers to submarine melting

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Straneo

Felikson

et al. 2019

Preprint

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“…As a marine-type glacier system residing on a retrograde bed with bedrock elevation as much as ∼ 800 m below sea level ( Fig. 1c), the Fleming system is accordingly potentially vulnerable to marine ice sheet instability (Mercer, 1978;Thomas and Bentley, 1978;Weertman, 1974). The acceleration and greater dynamic thinning of the FG over 2008-2015 suggests the possible onset of unstable rapid grounding line retreat (Walker and Gardner, 2017;Zhao et al, 2017), which has been confirmed by Friedl et al (2018).…”

Section: Introductionmentioning

confidence: 83%

“…The background image is the bedrock from (a) and the black contours are the same ones as in (b). Mercer, 1978;Thomas and Bentley, 1978;Weertman, 1974). This marine ice sheet instability has been invoked to explain the recent widespread and rapid grounding line retreat of glaciers in the Amundsen Sea sector, likely triggered by increased basal melting reducing the buttressing influence of ice shelves (Rignot et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Basal friction of Fleming Glacier, Antarctica – Part 2: Evolution from 2008 to 2015

et al. 2018

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Abstract. The Wordie Ice Shelf–Fleming Glacier system in the southern Antarctic Peninsula has experienced a long-term retreat and disintegration of its ice shelf in the past 50 years. Increases in the glacier velocity and dynamic thinning have been observed over the past two decades, especially after 2008 when only a small ice shelf remained at the Fleming Glacier front. It is important to know whether the substantial further speed-up and greater surface draw-down of the glacier since 2008 is a direct response to ocean forcing, or driven by feedbacks within the grounded marine-based glacier system, or both. Recent observational studies have suggested the 2008–2015 velocity change was due to the ungrounding of the Fleming Glacier front. To explore the mechanisms underlying the recent changes, we use a full-Stokes ice sheet model to simulate the basal shear stress distribution of the Fleming system in 2008 and 2015. This study is part of the first high resolution modelling campaign of this system. Comparison of inversions for basal shear stresses for 2008 and 2015 suggests the migration of the grounding line ∼9 km upstream by 2015 from the 2008 ice front/grounding line positions, which virtually coincided with the 1996 grounding line position. This migration is consistent with the change in floating area deduced from the calculated height above buoyancy in 2015. The retrograde submarine bed underneath the lowest part of the Fleming Glacier may have promoted retreat of the grounding line. Grounding line retreat may also be enhanced by a feedback mechanism upstream of the grounding line by which increased basal lubrication due to increasing frictional heating enhances sliding and thinning. Improved knowledge of bed topography near the grounding line and further transient simulations with oceanic forcing are required to accurately predict the future movement of the Fleming Glacier system grounding line and better understand its ice dynamics and future contribution to sea level.

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“…This meltwater can transfer heat throughout the ice column through discharge within crevasses and moulins thus softening the ice (Phillips et al, 2010). Incorporating a continuum damage model in BISI-CLES would further exaggerate the shear margin weakening, as it raises the nonlinear dependence of strain rates on stress fields (Sun et al, 2017).…”

Section: Horizontal Shearing and Viscositymentioning

confidence: 99%

“…Nick et al (2013) prescribed a flow band that has a near uniform width of 5 km near the terminus. Later modeling work using a similar model suggested that stability of the glacier is fundamentally controlled by geometry, and in reality the width varies along the ice stream (Steiger et al, 2018). Nick et al (2013) chose sets of parameters that produced small interannual retreats of Jakobshavn from 2000-2010, which may limit mass loss and retreat.…”

Section: Comparison With Previous Estimatesmentioning

confidence: 99%

Simulated retreat of Jakobshavn Isbræ during the 21st century

et al. 2019

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The early 21st century retreat of Jakobshavn Isbrae into its overdeepened bedrock trough was accompanied by acceleration to unprecedented ice stream speeds. Such dramatic changes suggested the possibility of substantial mass loss over the rest of this century. Here we use a threedimensional ice sheet model with parameterizations to represent the effects of ice mélange buttressing, crevasse-depthbased calving and submarine melting to adequately reproduce its recent evolution. We are the first study on Jakobshavn Isbrae that solves for three-dimensional ice flow coupled with representations of hydro-fracturing-induced calving and mélange buttressing. Additionally, the model can accurately replicate interannual variations in grounding line and terminus position, including seasonal fluctuations that emerged after arriving at the overdeepened basin and the disappearance of its floating ice shelf. Our simulated ice viscosity variability due to shear margin evolution is particularly important in reproducing the large observed interannual changes in terminus velocity. We use this model to project Jakobshavn's evolution over this century, forced by ocean temperatures from seven Earth system models and surface runoff derived from RACMO, all under the IPCC RCP4.5 climate scenario. In our simulations, Jakobshavn's grounding line continues to retreat ∼ 18.5 km by the end of this century, leading to a total mass loss of ∼ 2068 Gt (5.7 mm sea level rise equivalent). Despite the relative success of the model in simulating the recent behavior of the glacier, the model does not simulate winter calving events that have become relatively more important.Published by Copernicus Publications on behalf of the European Geosciences Union.

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Simulated retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry

Cited by 15 publications

References 95 publications

Past and future response of Greenland's tidewater glaciers to submarine melting

Past and future response of Greenland's tidewater glaciers to submarine melting

Basal friction of Fleming Glacier, Antarctica – Part 2: Evolution from 2008 to 2015

Simulated retreat of Jakobshavn Isbræ during the 21st century

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