Abstract
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 water-equivalent 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.
Highlights
About 74 % of the grounded ice sheet of Antarctica drains into the Southern Ocean through floating ice shelves (Bindschadler et al, 2011)
It has been hypothesized that enhanced meltwater production at the ice-shelf surface can lead to hydrofracturing, whereby meltwater-filled crevasses open up under the pressure exerted at the crevasse tip by the column of standing meltwater (Scambos et al, 2003; Van der Veen, 2007), and/or where drainage of meltwater lakes induces fracture by strong flexural stresses (MacAyeal and Sergienko, 2013)
The surface height increased quite gradually, suggesting that precipitation occurs in frequent small-magnitude events, rather than in a small number of large accumulation events per year
Summary
About 74 % of the grounded ice sheet of Antarctica drains into the Southern Ocean through floating ice shelves (Bindschadler et al, 2011). Dupont and Alley, 2005; Gagliardini et al, 2010), ice shelves strongly modulate the flux of ice into the ocean, thereby exerting an important control over the contribution of mass variations of the Antarctic Ice Sheet to global sea level. P. Kuipers Munneke et al.: Surface mass balance on Larsen C ice shelf. It is believed that these ice-shelf collapses along the Antarctic Peninsula have been attributed, at least in part, to warming of the near-surface atmosphere (Morris and Vaughan, 2003). There is a need to describe the surface mass balance (SMB) of these ice shelves accurately
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