Massive subsurface ice formed by refreezing of ice-shelf melt ponds

Hubbard, Bryn; Luckman, Adrian; Ashmore, David W.; Bevan, Suzanne; Kulessa, Bernd; Munneke, Peter Kuipers; Philippe, Morgane; Jansen, Daniela; Booth, Adam; Sevestre, Heïdi; Tison, Jean‐Louis; O’Leary, Martin; Rutt, I. C.

doi:10.1038/ncomms11897

Cited by 85 publications

(106 citation statements)

References 42 publications

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“…The occurrence of ice lensing within the firn has been observed in Cabinet Inlet, Larsen C by Hubbard et al (2016) and annual layers of high density were observed on Larsen C by Gourmelen et al (2009). Furthermore, the large features of solid ice observed by Hubbard et al (2016) suggest that significant saturation of the firn and refreezing of meltwater had previously occurred.…”

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confidence: 94%

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Modelling the fate of surface melt on the Larsen C Ice Shelf

Buzzard¹,

Feltham²,

Flocco³

2018

Preprint

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Abstract. Surface melt lakes lower the albedo of ice shelves leading to additional surface melting. This can substantially alter the surface energy balance and internal temperature and density profiles of the ice shelf. Evidence suggests that melt lakes also played a pivotal role in the sudden collapse of the Larsen B Ice Shelf in 2002.Here a recently developed, high physical fidelity model accounting for the development cycle of melt lakes is applied to the Larsen C Ice Shelf, Antarctica's most northern ice shelf and one where melt lakes have been observed. We simulate current 5 conditions on the ice shelf using weather station and reanalysis data, and investigate the impacts of potential future increases in precipitation and air temperature on melt lake formation, where concurrent increases lead to an increase in lake depth.Finally, we assess the viability of future crevasse propagation through the ice shelf due to surface meltwater accumulation.

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mentioning

confidence: 94%

“…Furthermore, the large features of solid ice observed by Hubbard et al (2016) suggest that significant saturation of the firn and refreezing of meltwater had previously occurred.…”

mentioning

confidence: 99%

Modelling the fate of surface melt on the Larsen C Ice Shelf

Buzzard¹,

Feltham²,

Flocco³

2018

Preprint

View full text Add to dashboard Cite

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“…ground-penetrating radar, firn density modelling, and satellite images identified a massive subsurface body of anomalously warm and dense ice (Hubbard et al, 2016). This body of ice was interpreted to be the result of the intense melt and regular surface ponding that occurs in this area.…”

Section: Introductionmentioning

confidence: 99%

“…In late 2015 we drilled four boreholes in addition to that reported by Hubbard et al (2016), consisting of two directly downstream from Cabinet Inlet and two downstream from Whirlwind Inlet (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Centuries of intense surface melt on Larsen C Ice Shelf

et al. 2017

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Abstract. Following a southward progression of ice-shelf disintegration along the Antarctic Peninsula (AP), Larsen C Ice Shelf (LCIS) has become the focus of ongoing investigation regarding its future stability. The ice shelf experiences surface melt and commonly features surface meltwater ponds. Here, we use a flow-line model and a firn density model (FDM) to date and interpret observations of meltaffected ice layers found within five 90 m boreholes distributed across the ice shelf. We find that units of ice within the boreholes, which have densities exceeding those expected under normal dry compaction metamorphism, correspond to two climatic warm periods within the last 300 years on the Antarctic Peninsula. The more recent warm period, from the 1960s onwards, has generated distinct sections of dense ice measured in two boreholes in Cabinet Inlet, which is close to the Antarctic Peninsula mountains -a region affected by föhn winds. Previous work has classified these layers as refrozen pond ice, requiring large quantities of mobile liquid water to form. Our flow-line model shows that, whilst preconditioning of the snow began in the late 1960s, it was probably not until the early 1990s that the modern period of ponding began. The earlier warm period occurred during the 18th century and resulted in two additional sections of anomalously dense ice deep within the boreholes. The first, at 61 m in one of our Cabinet Inlet boreholes, consists of ice characteristic of refrozen ponds and must have formed in an area currently featuring ponding. The second, at 69 m in a mid-shelf borehole, formed at the same time on the edge of the pond area. Further south, the boreholes sample ice that is of an equivalent age but which does not exhibit the same degree of melt influence. This west-east and north-south gradient in the past melt distribution resembles current spatial patterns of surface melt intensity.

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“…In Cainet Inlet (Fig. 1), the firn contains a massive subsurface ice layer (Hubbard et al, 2016), influencing ice-shelf temperatures, density, and potentially, flow properties. The occurrence of föhn winds has increased in recent decades (Cape et al, 2015), contributing to the destabilization of Larsen B ice shelf through increased meltwater production.…”

Section: Introductionmentioning

confidence: 99%

Observationally constrained surface mass balance of Larsen C ice shelf, Antarctica

et al. 2017

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Abstract. The surface mass balance (SMB) of the Larsen C ice shelf (LCIS), Antarctica, is poorly constrained due to a dearth of in situ observations. Combining several geophysical techniques, we reconstruct spatial and temporal patterns of SMB over the LCIS. Continuous time series of snow height (2.5-6 years) at five locations allow for multi-year estimates of seasonal and annual SMB over the LCIS. There is high interannual variability in SMB as well as spatial variability: in the north, SMB is 0.40 ± 0.06 to 0.41 ± 0.04 m w.e. year −1 , while farther south, SMB is up to 0.50 ± 0.05 m w.e. year −1 . This difference between north and south is corroborated by winter snow accumulation derived from an airborne radar survey from 2009, which showed an average snow thickness of 0.34 m w.e. north of 66 • S, and 0.40 m w.e. south of 68 • S. Analysis of ground-penetrating radar from several field campaigns allows for a longer-term perspective of spatial variations in SMB: a particularly strong and coherent reflection horizon below 25-44 m of waterequivalent ice and firn is observed in radargrams collected across the shelf. We propose that this horizon was formed synchronously across the ice shelf. Combining snow height observations, ground and airborne radar, and SMB output from a regional climate model yields a gridded estimate of SMB over the LCIS. It confirms that SMB increases from north to south, overprinted by a gradient of increasing SMB to the west, modulated in the west by föhn-induced sublimation. Previous observations show a strong decrease in firn air content toward the west, which we attribute to spatial patterns of melt, refreezing, and densification rather than SMB.

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Massive subsurface ice formed by refreezing of ice-shelf melt ponds

Cited by 85 publications

References 42 publications

Modelling the fate of surface melt on the Larsen C Ice Shelf

Modelling the fate of surface melt on the Larsen C Ice Shelf

Centuries of intense surface melt on Larsen C Ice Shelf

Observationally constrained surface mass balance of Larsen C ice shelf, Antarctica

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