On the role of buoyant flexure in glacier calving

Wagner, Thomas; James, T. D.; Murray, Tavi; Vella, Dominic

doi:10.1002/2015gl067247

Cited by 47 publications

(66 citation statements)

References 48 publications

(102 reference statements)

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“…First, quantification of the associated mass loss suggests that fjord-scale melting is responsible for a substantial portion of the total mass lost due to submarine melting. The notch also creates a buoyant foot which exerts bending stresses on the ice behind, potentially promoting the opening of basal crevasses and large calving events (Benn et al, 2017;Wagner et al, 2016). Fjord-scale melting may therefore be a significant component of the calving front mass budget which ultimately determines glacier advance and retreat.…”

Section: Resultsmentioning

confidence: 99%

Localized Plumes Drive Front‐Wide Ocean Melting of A Greenlandic Tidewater Glacier

Slater

Straneo

Das

et al. 2018

Geophysical Research Letters

160

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Recent acceleration of Greenland's ocean‐terminating glaciers has substantially amplified the ice sheet's contribution to global sea level. Increased oceanic melting of these tidewater glaciers is widely cited as the likely trigger, and is thought to be highest within vigorous plumes driven by freshwater drainage from beneath glaciers. Yet melting of the larger part of calving fronts outside of plumes remains largely unstudied. Here we combine ocean observations collected within 100 m of a tidewater glacier with a numerical model to show that unlike previously assumed, plumes drive an energetic fjord‐wide circulation which enhances melting along the entire calving front. Compared to estimates of melting within plumes alone, this fjord‐wide circulation effectively doubles the glacier‐wide melt rate, and through shaping the calving front has a potential dynamic impact on calving. Our results suggest that melting driven by fjord‐scale circulation should be considered in process‐based projections of Greenland's sea level contribution.

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Section: Resultsmentioning

confidence: 99%

Localized Plumes Drive Front‐Wide Ocean Melting of A Greenlandic Tidewater Glacier

Slater

Straneo

Das

et al. 2018

Geophysical Research Letters

160

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show abstract

“…As a result, these glaciers produce large‐magnitude full‐thickness capsizing slab and rifting tabular calving events (Figure ), which exceed localized retreat from submarine melt. Under these conditions, terminus positions largely depend on buoyant flexure (Figure b) at the glacier front (James et al, ; Murray, Selmes, et al, ) set by the ice thickness/water depth ratio and the propagation of buoyancy‐induced basal crevasses (Murray, Selmes, et al, ; Wagner et al, ). It remains poorly understood how terminus undercutting from submarine melt might affect calving frequency at these types of glaciers, as calving likely outpaces undercutting, but it is possible that subglacial discharge enlarges basal crevasses initially formed due to buoyancy forces.…”

Section: Discussionmentioning

confidence: 99%

Reconciling Drivers of Seasonal Terminus Advance and Retreat at 13 Central West Greenland Tidewater Glaciers

et al. 2018

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The majority of Greenland tidewater glaciers undergo a seasonal cycle in terminus position, characterized by wintertime advance and summertime retreat. Understanding mechanisms that control seasonal cycles can help elucidate how tidewater glaciers regulate dynamic ice loss on longer timescales. However, controls on terminus position are numerous and complex. To address this, we compare time series of satellite‐derived terminus positions for tidewater glaciers in central west Greenland with observations of environmental forcings, including runoff at the grounding line, mélange presence, and, where available, ocean temperature in the proglacial fjord. We show that for most glaciers, seasonal terminus positions are more sensitive to glacial runoff than mélange or ocean thermal forcing. The strength of this relationship differs for two end‐member glacier types in the region, defined by their terminus geometry and dominant calving style. First, we find a strong relationship between magnitudes of runoff and terminus retreat at tidewater glaciers with shallow grounding lines (<400 m) that calve primarily through small‐magnitude serac failures. At these glaciers, subglacial plumes drive submarine melt and locally enhance retreat, causing heterogeneous position change across the terminus and local embayments where seasonal terminus changes are largest. In contrast, deep termini susceptible to buoyant flexure retreat sporadically through full ice thickness calving events less dependent on runoff. While less common, these glaciers deliver larger ice fluxes to the ocean. With predicted surface melt increases and diminished mélange coverage in a warming climate, our results reveal the impact of environmental forcings on diverse tidewater glacier systems in the region.

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“…Buoyancy-driven calving is an important process on large, fast-flowing outlet glaciers [59][60][61][62][63][64]. Rapid ice flow into deep water can create 'super-buoyant' conditions, in which ice fronts are out of hydrostatic equilibrium and subject to large upward-directed torque forces (Fig.…”

Section: Processes Of Frontal Ablationmentioning

confidence: 99%

Glacier Calving in Greenland

Benn

Cowton

Todd

et al. 2017

Curr Clim Change Rep

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In combination, the breakaway of icebergs (calving) and submarine melting at marine-terminating glaciers account for between one third and one half of the mass annually discharged from the Greenland Ice Sheet into the ocean. These ice losses are increasing due to glacier acceleration and retreat, largely in response to increased heat flux from the oceans. Behaviour of Greenland's marine-terminating ('tidewater') glaciers is strongly influenced by fjord bathymetry, particularly the presence of 'pinning points' (narrow or shallow parts of fjords that encourage stability) and overdeepened basins (that encourage rapid retreat). Despite the importance of calving and submarine melting and significant advances in monitoring and understanding key processes, it is not yet possible to predict the tidewater glacier response to climatic and oceanic forcing with any confidence. The simple calving laws required for ice-sheet models do not adequately represent the complexity of calving processes. New detailed process models, however, are increasing our understanding of the key processes and are guiding the design of improved calving laws. There is thus some prospect of reaching the elusive goal of accurately predicting future tidewater glacier behaviour and associated rates of sea-level rise.

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On the role of buoyant flexure in glacier calving

Cited by 47 publications

References 48 publications

Localized Plumes Drive Front‐Wide Ocean Melting of A Greenlandic Tidewater Glacier

Localized Plumes Drive Front‐Wide Ocean Melting of A Greenlandic Tidewater Glacier

Reconciling Drivers of Seasonal Terminus Advance and Retreat at 13 Central West Greenland Tidewater Glaciers

Glacier Calving in Greenland

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