Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2017-41
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
07 Apr 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal The Cryosphere (TC) and is expected to appear here in due course.
Detecting high spatial variability of ice-shelf basal mass balance (Roi Baudouin ice shelf, Antarctica)
Sophie Berger1, Reinhard Drews2, Veit Helm3, Sainan Sun1, and Frank Pattyn1 1Laboratoire de glaciologie, Université libre de Bruxelles, Brussels, Belgium
2Bavarian Academy of Sciences and Humanities, Munich, Germany
3Alfred Wegener Institute, Bremerhaven, Germany
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 a novel 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 within a Lagrangian framework based on high-resolution surface velocities, atmospheric-model surface mass balance and hydrostatic ice-thickness fields (derived from TanDEM-X surface elevation). Spatial derivatives are implemented using the total-variation differentiation, which avoids spatial averaging hence loss of spatial resolution. Our BMB field exhibits high detail and ranges from −14.8 to 8.6 m a−1 ice equivalent. Highest melt rates are found close to the grounding line where the basal ice-shelf slope is the steepest. The BMB field agrees well with on-site measurements from phase-sensitive radar, although unresolved spatial variations in firn density determined from profiling radar occur. We show that the surface expression of an englacial lake (0.7 × 1.3 km2 wide and 30 m deep) 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 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.

Citation: Berger, S., Drews, R., Helm, V., Sun, S., and Pattyn, F.: Detecting high spatial variability of ice-shelf basal mass balance (Roi Baudouin ice shelf, Antarctica), The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-41, in review, 2017.
Sophie Berger et al.
Sophie Berger et al.
Sophie Berger et al.

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Short summary
Floating ice shelves act as a plug for the Antarctic ice sheet. The efficiency of this plug depends on how and how much the ocean melts the ice from below. This study uses satellite images to produce a very detailed map of basal melting of an Antarctic ice shelf. Although the large scale melting pattern of the ice shelf agrees well with previous studies, our map shows that basal melting varies a lot over short distances (< 1 km) and that our technique is able to detect this local variability.
Floating ice shelves act as a plug for the Antarctic ice sheet. The efficiency of this plug...
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