Roughness of Ice Shelves Is Correlated With Basal Melt Rates

Watkins, R.; Bassis, J. N.; Thouless, M.D.

doi:10.1029/2021gl094743

Cited by 18 publications

(40 citation statements)

References 58 publications

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“…Observations also suggest complex relations between ocean conditions, melting rate, and basal ice properties. For example, ice-penetrating radar and autonomous underwater vehicles have shown that melting depends on the ice roughness or slope of the ice-water interface [11,15,65]. Further modelling and analysis would be useful for elucidating the effects that these processes have on the evolution of ice-shelf topography that is generated by melting at the base.…”

Section: Discussionmentioning

confidence: 99%

Linear analysis of ice-shelf topography response to basal melting and freezing

Stubblefield¹,

Meyer²,

Wearing³

2023

Preprint

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Floating ice shelves in Antarctica and Greenland limit land-ice contributions to sea level rise by resisting the flow of grounded ice. Melting at the surface and base of ice shelves can lead to destabilisation by promoting thinning and fracturing. Basal melting often results in channelised features that manifest as surface topography due to buoyancy. The assumption of hydrostatic flotation commonly underlies estimates of basal melting rates. However, numerical simulations and ice-penetrating radar data have shown that narrow topographic features do not necessarily satisfy the local flotation condition. Here, we introduce a linearised model for ice-shelf topographic response to basal melting perturbations to quantify deviations from hydrostatic flotation and the stability of topography. While hydrostatic flotation is the dominant behaviour at wavelengths greater than the ice thickness, ice elevation anomalies diminish relative to the perfect flotation condition at smaller wavelengths. The linearised analysis shows that steady solutions are stable. However, we do not consider physical effects such as fracturing, which could lead to instability. We find a Green’s function for one-dimensional steady-state solutions in the absence of background advection. We validate the linearised analysis by comparing numerical solutions to a nonlinear ice-flow model with steady-state solutions obtained via the Green’s function.

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Section: Discussionmentioning

confidence: 99%

Linear analysis of ice-shelf topography response to basal melting and freezing

Stubblefield¹,

Meyer²,

Wearing³

2023

Preprint

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“…Other processes that have been found to have an influence over ice shelves are basal roughness and polynyas. Watkins et al (2021) found that the roughness of ice shelves was correlated with basal melt rates, as interesting as it is Larter (2022) addressed that more measurements around Antarctica are necessary to corroborate that the correlation holds. Non-etheless, Bianchi et al (2001) carried out an assessment of the underlying roughness of 10 ice tongues and ice shelves in the Western Ross sea and Pennel Coast.…”

Section: Spatial Relations Between Basal Mass Balance and Geographica...mentioning

confidence: 96%

Basal mass balance and prevalence of ice tongues in the Western ross sea

et al. 2023

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Ice tongues at the fringes of the Antarctic ice sheet lose mass primarily through both basal melting and calving. They are sensitive to ocean conditions which can weaken the ice both mechanically or through thinning. Ice tongues, which are laterally unconfined, are likely to be particularly sensitive to ocean-induced stresses. Here we examine ice tongues in the Western Ross Sea, by looking into the factors affecting their stability. We calculate the basal mass change of twelve Antarctic ice tongues using a flux gate approach, deriving thickness from ICESat-2 height measurements and ice surface velocities from Sentinel-1 feature-tracking over the same period (October 2018 to December 2021). The basal mass balance ranges between −0.14 ± 0.07 m yr−1 and −1.50 ± 1.2 m yr−1. The average basal mass change for all the ice tongues is −0.82 ± 0.68 m of ice yr−1. Low values of basal melt suggest a stable mass balance condition in this region, with low thermal ocean forcing, as other studies have shown. We found a heterogeneous basal melt pattern with no latitudinal gradient and no clear driver in basal melt indicating that local variables are important in the persistence of ice tongues in the absence of a strong oceanographic melting force. Moreover, thanks to the temporal resolution of the data we were able to resolve the seasonal variability of Drygalski and Aviator Ice Tongues, the two largest ice tongues studied.

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“…In order to provide some forewarning of when basal melting is driving an ice shelf into a highly vulnerable state though, it would be useful to have a simple quantitative measure of how its structural integrity has been impacted. Results from analyses of variations in ice thickness, or "roughness", of ice shelves by Watkins et al (2021; https://doi.org/10.1029/2021GL094743) raise the tantalizing prospect that this may provide such a measure.…”

Section: A Way Of Measuring Impact On Structural Integrity?mentioning

confidence: 99%

“…By analyzing radio-echo sounding (RES) profiles from airborne surveys Watkins et al (2021; https://doi. org/10.1029/2021GL094743) examined the spectral signature of variations in roughness on seven ice shelves of a range of sizes and in different settings.…”

Section: A Way Of Measuring Impact On Structural Integrity?mentioning

confidence: 99%

Basal Melting, Roughness and Structural Integrity of Ice Shelves

Larter

2022

Geophysical Research Letters

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Ice shelves, extensions of glaciers that float over the ocean, act as buttresses restraining the flow of glaciers feeding into them. They restrict outflow from many of the largest glaciers and ice streams in Antarctica. This concept had been considered theoretically for decades, but its reality was very clearly demonstrated by the collapse of the Larsen B Ice Shelf on the east side of the Antarctic Peninsula in 2002 and the subsequent increase in flow velocity of glaciers that had previously flowed into it (De Angelis & Skvarca, 2003;Scambos et al., 2004). Collapse of ice shelves that larger glaciers flow into leading to acceleration of their flow into the ocean would increase the Antarctic contribution to global sea-level rise.Many large glaciers in West Antarctica and some covering large parts of East Antarctica flow on beds that increase in depth upstream. For these glaciers, ice thinning resulting from such flow acceleration would force retreat of their grounding lines, where glacier ice starts to float as it flows toward the ocean. This in turn has the potential to initiate runaway retreat through a feedback process called Marine Ice Sheet Instability (MISI;Schoof, 2007;Weertman, 1974).A further possibility is that sudden ice-shelf collapse could leave tall ice cliffs in which gravitational stress from the mass above water and buoyancy from the submerged part exceeds the yield strength of the ice. Where glacier beds increase in depth upstream, resulting cliff failure would expose even taller cliffs, potentially leading to runaway retreat through a different feedback process called Marine Ice Cliff Instability (MICI; Bassis & Jacobs, 2013;Crawford et al., 2021). There are no examples of MICI having driven substantial retreat during the relatively short period of modern observations of ice-sheet change, but characteristics of iceberg-keel plow marks over an

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Roughness of Ice Shelves Is Correlated With Basal Melt Rates

Cited by 18 publications

References 58 publications

Linear analysis of ice-shelf topography response to basal melting and freezing

Linear analysis of ice-shelf topography response to basal melting and freezing

Basal mass balance and prevalence of ice tongues in the Western ross sea

Basal Melting, Roughness and Structural Integrity of Ice Shelves

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