Actively evolving subglacial conduits and eskers initiate ice shelf channels at an Antarctic grounding line

Drews, Reinhard; Pattyn, Frank; Hewitt, Ian; Ng, Felix; Berger, Sophie; Matsuoka, Kenichi; Helm, Veit; Bergeot, Nicolas; Favier, Lionel; Neckel, Niklas

doi:10.1038/ncomms15228

Cited by 54 publications

(80 citation statements)

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“…Almost all ice shelf channels at RBIS are connected to the grounding line and may arise from water-filled subglacial conduits injecting subglacial melt water into the ice shelf cavity, driving a spatially localized buoyant melt water plume (Jenkins, 2011;Le Brocq et al, 2013;Drews et al, 2017;Sergienko, 2013). Such localized melting near the grounding zone has been previously observed on Pine Island Ice Shelf using similar methods as done here (Dutrieux et al, 2013). However, on Pine Island Ice Shelf, background melt rates are an order of magnitude larger than what is observed here Rignot et al, 2013) and Dutrieux et al (2013) analysed DEMs separated by 3 years (compared to the 1-year time period used here).…”

Section: Discussionsupporting

confidence: 67%

“…near ice shelf channels). We refer to previous publications (Dutrieux et al, 2013;Moholdt et al, 2014;Shean et al, 2017) that further explain differences between Eulerian and Lagrangian approaches. In the following, we describe surface velocities in Sect.…”

Section: Basal Mass Balance From Mass Conservationmentioning

confidence: 99%

“…the difference between refreezing and melting. Point measurements with phase-sensitive radars (Marsh et al, 2016;Nicholls et al, 2015), global navigation satellite system (GNSS) receivers (Shean et al, 2017), observations from underwater vehicles (Dutrieux et al, 2014) and analysis from high-resolution satellites (Dutrieux et al, 2013;Wilson et al, 2017) have shown that BMB varies spatially on sub-kilometre scales. Ice shelf channels are one expression of localized basal melting (Stanton et al, 2013;Marsh et al, 2016) which, after hydrostatic adjustment, form curvilinear depressions visible at the ice shelf surface (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Detailed response to the reviewes, modifications made on manuscript tc-2017-41 and new supplementary

Berger¹

2017

Preprint

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Ice shelves control the dynamic mass loss of ice sheets through buttressing and their integrity depends on the spatial variability of their basal mass balance (BMB), i.e. the difference between refreezing and melting. Here, we present an improved technique -based on satellite observations -to capture the small-scale variability in the BMB of ice shelves. As a case study, we apply the methodology to the Roi Baudouin Ice Shelf, Dronning Maud Land, East Antarctica, and derive its yearly averaged BMB at 10 m horizontal gridding. We use mass conservation in a Lagrangian framework based on high-resolution surface velocities, atmosphericmodel surface mass balance and hydrostatic ice-thickness fields (derived from TanDEM-X surface elevation). Spatial derivatives are implemented using the total-variation differentiation, which preserves abrupt changes in flow velocities and their spatial gradients. Such changes may reflect a dynamic response to localized basal melting and should be included in the mass budget. Our BMB field exhibits much spatial detail and ranges from −14.7 to 8.6 m a −1 ice equivalent. Highest melt rates are found close to the grounding line where the pressure melting point is high, and the ice shelf slope is steep. The BMB field agrees well with on-site measurements from phase-sensitive radar, although independent radar profiling indicates unresolved spatial variations in firn density. We show that an elliptical surface depression (10 m deep and with an extent of 0.7 km × 1.3 km) lowers by 0.5 to 1.4 m a −1 , which we tentatively attribute to a transient adaptation to hydrostatic equilibrium. We find evidence for elevated melting beneath ice shelf channels (with melting being concentrated on the channel's flanks). However, farther downstream from the grounding line, the majority of ice shelf channels advect passively (i.e. no melting nor refreezing) toward the ice shelf front. Although the absolute, satellite-based BMB values remain uncertain, we have high confidence in the spatial variability on sub-kilometre scales. This study highlights expected challenges for a full coupling between ice and ocean models.

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Section: Discussionsupporting

confidence: 67%

Section: Basal Mass Balance From Mass Conservationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Detailed response to the reviewes, modifications made on manuscript tc-2017-41 and new supplementary

Berger¹

2017

Preprint

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“…4). Almost all ice shelf channels at RBIS are connected to the grounding line and may arise from water-filled subglacial conduits injecting subglacial melt water into the ice shelf cavity, driving a spatially localized buoyant melt water plume (Jenkins, 2011;Le Brocq et al, 2013;Drews et al, 2017;Sergienko, 2013). Such localized melting near the grounding zone has been previously observed on Pine Island Ice Shelf using similar methods as done here (Dutrieux et al, 2013).…”

Section: Discussionmentioning

confidence: 67%

Detecting high spatial variability of ice shelf basal mass balance, Roi Baudouin Ice Shelf, Antarctica

et al. 2017

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Abstract. Ice shelves control the dynamic mass loss of ice sheets through buttressing and their integrity depends on the spatial variability of their basal mass balance (BMB), i.e. the difference between refreezing and melting. Here, we present an improved technique -based on satellite observations -to capture the small-scale variability in the BMB of ice shelves. As a case study, we apply the methodology to the Roi Baudouin Ice Shelf, Dronning Maud Land, East Antarctica, and derive its yearly averaged BMB at 10 m horizontal gridding. We use mass conservation in a Lagrangian framework based on high-resolution surface velocities, atmosphericmodel surface mass balance and hydrostatic ice-thickness fields (derived from TanDEM-X surface elevation). Spatial derivatives are implemented using the total-variation differentiation, which preserves abrupt changes in flow velocities and their spatial gradients. Such changes may reflect a dynamic response to localized basal melting and should be included in the mass budget. Our BMB field exhibits much spatial detail and ranges from −14.7 to 8.6 m a −1 ice equivalent. Highest melt rates are found close to the grounding line where the pressure melting point is high, and the ice shelf slope is steep. The BMB field agrees well with on-site measurements from phase-sensitive radar, although independent radar profiling indicates unresolved spatial variations in firn density. We show that an elliptical surface depression (10 m deep and with an extent of 0.7 km × 1.3 km) lowers by 0.5 to 1.4 m a −1 , which we tentatively attribute to a transient adaptation to hydrostatic equilibrium. We find evidence for elevated melting beneath ice shelf channels (with melting being concentrated on the channel's flanks). However, farther downstream from the grounding line, the majority of ice shelf channels advect passively (i.e. no melting nor refreezing) toward the ice shelf front. Although the absolute, satellite-based BMB values remain uncertain, we have high confidence in the spatial variability on sub-kilometre scales. This study highlights expected challenges for a full coupling between ice and ocean models.

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“…Evidence of this process is given by the observation of elevated melt on the Coriolis‐favored side of DISC (Figure S7) supporting the hypothesis that water flowing within DISC is deflected by Coriolis and thus is guided by the channel itself. This conceptual method of channel formation is distinct from that of subglacially sourced channels such as that observed in Roi Baudoin ice shelf (Drews et al, ), as the buoyant driver required for the high velocities that lead to amplified melt (Jenkins, ) comes from the melt itself, not the fresh subglacial runoff. This may be why the melt (and hence the channel) can persist to the ice shelf front, rather than diminishing with distance from the grounding line, and suggests that the presence of CDW is prerequisite for the DISC to exist.…”

Section: Discussionmentioning

confidence: 99%

Channelized Melting Drives Thinning Under a Rapidly Melting Antarctic Ice Shelf

Gourmelen

Goldberg

Snow

et al. 2017

Geophysical Research Letters

115

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Ice shelves play a vital role in regulating loss of grounded ice and in supplying freshwater to coastal seas. However, melt variability within ice shelves is poorly constrained and may be instrumental in driving ice shelf imbalance and collapse. High‐resolution altimetry measurements from 2010 to 2016 show that Dotson Ice Shelf (DIS), West Antarctica, thins in response to basal melting focused along a single 5 km‐wide and 60 km‐long channel extending from the ice shelf's grounding zone to its calving front. If focused thinning continues at present rates, the channel will melt through, and the ice shelf collapse, within 40–50 years, almost two centuries before collapse is projected from the average thinning rate. Our findings provide evidence of basal melt‐driven sub‐ice shelf channel formation and its potential for accelerating the weakening of ice shelves.

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Actively evolving subglacial conduits and eskers initiate ice shelf channels at an Antarctic grounding line

Cited by 54 publications

References 62 publications

Detailed response to the reviewes, modifications made on manuscript tc-2017-41 and new supplementary

Detailed response to the reviewes, modifications made on manuscript tc-2017-41 and new supplementary

Detecting high spatial variability of ice shelf basal mass balance, Roi Baudouin Ice Shelf, Antarctica

Channelized Melting Drives Thinning Under a Rapidly Melting Antarctic Ice Shelf

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