Channelized Ice Melting in the Ocean Boundary Layer Beneath Pine Island Glacier, Antarctica

Stanton, Timothy P.; Shaw, William J.; Truffer, Martin; Corr, Hugh; Peters, L. E.; Riverman, K. L.; Bindschadler, Robert; Holland, David M.; Anandakrishnan, S.

doi:10.1126/science.1239373

Cited by 113 publications

(164 citation statements)

References 24 publications

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“…Generally, melt that begins at depth is sustained by entrainment of additional warm water as the buoyant meltwater plume rises along the underside of the ice (Jenkins, 2011). Basal melt channels have been observed in many locations around Antarctica (e.g., Alley et al, 2016) and are thought to form in the location where the meltwater plume rises along the bottom of the shelf (Marsh et al, 2016;Stanton et al, 2013). The shallowing of this channel as it curves along the grounding line to the western margin of Dotson is consistent with this model of channel formation.…”

Section: History Of Meltmentioning

confidence: 99%

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

et al. 2018

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Abstract. Crosson and Dotson ice shelves are two of the most rapidly changing outlets in West Antarctica, displaying both significant thinning and grounding-line retreat in recent decades. We used remotely sensed measurements of velocity and ice geometry to investigate the processes controlling their changes in speed and grounding-line position over the past 20 years. We combined these observations with inverse modeling of the viscosity of the ice shelves to understand how weakening of the shelves affected this speedup. These ice shelves have lost mass continuously since the 1990s, and we find that this loss results from increasing melt beneath both shelves and the increasing speed of Crosson. High melt rates persisted over the period covered by our observations (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014), with the highest rates beneath areas that ungrounded during this time. Grounding-line flux exceeded basin-wide accumulation by about a factor of 2 throughout the study period, consistent with earlier studies, resulting in significant loss of grounded as well as floating ice. The near doubling of Crosson's speed in some areas during this time is likely the result of weakening of its margins and retreat of its grounding line. This speedup contrasts with Dotson, which has maintained its speed despite increasingly high melt rates near its grounding line, likely a result of the sustained competency of the shelf. Our results indicate that changes to melt rates began before 1996 and suggest that observed increases in melt in the 2000s compounded an ongoing retreat of this system. Advection of a channel along Dotson, as well as the grounding-line position of Kohler Glacier, suggests that Dotson experienced a change in flow around the 1970s, which may be the initial cause of its continuing retreat.

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Section: History Of Meltmentioning

confidence: 99%

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

et al. 2018

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“…2). Basal melting inside channels can be significantly larger (Stanton et al, 2013), correspondingly influencing ice-shelf stability (Sergienko, 2013). Adjustment towards hydrostatic equilibrium resulting from basal melting can weaken ice shelves through crevasse formation (Vaughan et al, 2012).…”

Section: R Drews Et Al: Density From Wide-angle Radarmentioning

confidence: 99%

Constraining variable density of ice shelves using wide-angle radar measurements

Drews

Brown²,

Matsuoka

et al. 2016

The Cryosphere

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Abstract. The thickness of ice shelves, a basic parameter for mass balance estimates, is typically inferred using hydrostatic equilibrium, for which knowledge of the depthaveraged density is essential. The densification from snow to ice depends on a number of local factors (e.g., temperature and surface mass balance) causing spatial and temporal variations in density-depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar data sets (10 MHz) collected at five sites on Roi Baudouin Ice Shelf (RBIS), Dronning Maud Land, Antarctica. We reconstruct depth to internal reflectors, local ice thickness, and firn-air content using a novel algorithm that includes traveltime inversion and ray tracing with a prescribed shape of the depthdensity relationship. For the particular case of an ice-shelf channel, where ice thickness and surface slope change substantially over a few kilometers, the radar data suggest that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals that the firn inside the channel is 4.7 % denser than that outside the channel. Hydrostatic ice thickness calculations used for determining basal melt rates should account for the denser firn in ice-shelf channels. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.

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“…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. 1).…”

Section: S Berger Et Al: Spatial Variability Of Ice Shelf Basal Masmentioning

confidence: 99%

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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Channelized Ice Melting in the Ocean Boundary Layer Beneath Pine Island Glacier, Antarctica

Cited by 113 publications

References 24 publications

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

Constraining variable density of ice shelves using wide-angle radar measurements

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

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