Recent rift formation and impact on the structural integrity of the Brunt Ice Shelf, East Antarctica

Rydt, Jan De; Gudmundsson, G. Hilmar; Nägler, Thomas; Wuite, Jan; King, Edward C.

doi:10.5194/tc-12-505-2018

Cited by 37 publications

(71 citation statements)

References 34 publications

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“…An extensive network of GPS monitoring stations has been established on the Brunt Ice Shelf as part of the infrastructure for Halley VI Research Station (Anderson et al, 2014). Recently, two significant new rifts developed in the ice shelf (De Rydt et al, 2018), one an extension of "Chasm 1" (Fig. 1), which has remained unchanged since the 1970s; one a new rift named "Halloween Crack" (from the date of formation on 31 October 2016).…”

Section: Study Areamentioning

confidence: 99%

The internal structure of the Brunt Ice Shelf from ice-penetrating radar analysis and implications for ice shelf fracture

2018

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Abstract. The rate and direction of rift propagation through ice shelves depend on both the stress field and the heterogeneity (or otherwise) of the physical properties of the ice. The Brunt Ice Shelf in Antarctica has recently developed new rifts, which are being actively monitored as they lengthen and interact with the internal structure of the ice shelf. Here we present the results of a ground-penetrating radar survey of the Brunt Ice Shelf aimed at understanding variations in the internal structure. We find that there are flow bands composed mostly of thick (ca. 250 m) meteoric ice interspersed with thinner (ca. 150 m) sections of ice shelf that have a large proportion of sea ice and seawater-saturated firn. Therefore the ice shelf is, in essence, a series of ice tongues cemented together with ice mélange. The changes in structure are related both to the thickness and flow speed of ice at the grounding line and to subsequent processes of firn accumulation and brine infiltration as the ice shelf flows towards the calving front. It is shown that rifts propagating through the Brunt Ice Shelf preferentially skirt the edges of blocks of meteoric ice and slow their rate of propagation when forced by the stress field to break through them, in contrast to the situation on other ice shelves where rift propagation speeds up in meteoric ice.

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Section: Study Areamentioning

confidence: 99%

The internal structure of the Brunt Ice Shelf from ice-penetrating radar analysis and implications for ice shelf fracture

2018

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“…4). In addition, this ramp shows a curvilinear long axis that is aligned to the direction of modern flow of the Brunt Ice Shelf (De Rydt et al, 2018). Super-imposed iceberg berms are observed frequently on heavily scoured shelves of glaciated continental margins (e.g.…”

Section: Iceberg Ramp Formationmentioning

confidence: 94%

“…Recent crevasse and crack formation and their growth may lead to widespread loss of bed contact with the only remaining pinning point, McDonald Ice Rumples (Fig. 1), which may result in rapid ice shelf disintegration in the near future (Hodgson et al, 2019;De Rydt et al, 2018). The permanent British research station Halley (Fig.…”

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Past ice sheet-seabed interactions in the northeastern Weddell Sea Embayment, Antarctica

Arndt¹,

Larter²,

Hillenbrand³

et al. 2019

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Abstract. The Antarctic Ice Sheet extent in the Weddell Sea Embayment (WSE) during the Last Glacial Maximum (LGM; ca. 19–25 calibrated kiloyears before present, cal. ka BP) and its subsequent retreat from the shelf are poorly constrained, with two conflicting scenarios being discussed. Today, the modern Brunt Ice Shelf, the last remaining ice shelf in the northeastern WSE, is only pinned at a single location and recent crevasse development may lead to its rapid disintegration in the near future. We investigated the seafloor morphology on the northeastern WSE shelf and discuss its implications, in combination with marine geological records, for reconstructions of the past behaviour of this sector of the East Antarctic Ice Sheet (EAIS), including ice-seafloor interactions. Our data show that an ice stream flowed through Stancomb-Wills Trough and acted as the main conduit for EAIS drainage during the LGM. Post-LGM ice-stream retreat occurred stepwise, with at least three documented grounding line still stands, and the trough had become free of grounded ice by ~10.5 cal. ka BP. In contrast, slow-flowing ice once covered the shelf in Brunt Basin and extended westwards toward McDonald Bank. During a later time period, only floating ice was present within Brunt Basin, but large ‘ice slabs’ enclosed within the ice shelf occasionally ran aground at the eastern side of McDonald Bank, forming ten unusual ramp-shaped seabed features. These ramps are the result of temporary ice-shelf grounding events buttressing the ice further upstream. To the west of this area, Halley Trough very likely was free of grounded ice during the LGM, representing a potential refuge for benthic shelf fauna at this time.

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“…Note that these figures do not capture shallowing of the brittle-ductile transition due to marine ice accretion, as discussed later. Figure 2 shows that several ice shelves that have recently experienced large calving events (Larsen C), collapsed (Wilkins), and those with rapidly propagating rifts (Brunt) have significant regions with thin brittle ice H < H * (17,23,24).…”

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confidence: 99%

“…Fast propagation, in contrast, occurs rates at least equal tens of kilometers per week, a lower bound because observations are typically limited to approximately weekly satellite flyover times (17,23,24). Sparse in situ observations suggest that propagation speeds may be much faster, with one lower bound on the order of km/min (23).…”

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Ice shelf stability and the brittle–ductile transition

Lipovsky¹

2018

Preprint

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Fracturing processes limit the ability of floating ice shelves to stabilize marine ice sheets. Ice shelf fracturing may occur as either horizontally propagating rifts or vertically propagating and possibly water-filled crevasses. Here, I argue that ice shelves are most susceptible to brittle fracture when their thickness is less than the brittle-ductile transition thickness H * , defined as the depth at which the overburden pressure equals the local yield strength in tension. A fracture mechanical analysis, compared with time-lapse imagery and thickness maps demonstrate the ice dynamical role of the brittle-ductile transition.These findings suggest the existence of a calving-thinning instability whereby thinning-induced brittleness increases calving rates and reduces buttressing.Global mean sea level rise is expected to accelerate by the year 2100. Although the likely range for sea level rise rate by the year 2100 is 0.8 to 1.6 cm/a (1), a physically plausible set of models suggest that this could be an underestimate due to ice dynamical instabilities in Antarctica (2). Sea level rise rates result from such instability may be as large as 3 cm/a by 2100 and 6 cm/a by around 2150. The spread in these estimates has profound planning implications (1), therefore motivating the careful study of the underlying physical processes. Rapid sea level rise scenarios generally involve the widespread fracturing, calving, and break-up of the ice shelves (3) and an ensuing acceleration of grounded ice (4). Given this importance, the 1 Non-peer reviewed EarthArXiv preprint

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Recent rift formation and impact on the structural integrity of the Brunt Ice Shelf, East Antarctica

Cited by 37 publications

References 34 publications

The internal structure of the Brunt Ice Shelf from ice-penetrating radar analysis and implications for ice shelf fracture

The internal structure of the Brunt Ice Shelf from ice-penetrating radar analysis and implications for ice shelf fracture

Past ice sheet-seabed interactions in the northeastern Weddell Sea Embayment, Antarctica

Ice shelf stability and the brittle–ductile transition

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