Evolution of ice-shelf channels in Antarctic ice shelves

Abstract

Abstract. Ice shelves buttress the continental ice flux and mediate ice-ocean interactions. They are often traversed by channels in which basal melting is enhanced, impacting iceshelf stability. Here, channel evolution is investigated using a transient, three-dimensional full Stokes model and geophysical data collected on the Roi Baudouin Ice Shelf (RBIS), Antarctica. The modeling confirms basal melting as a feasible mechanism for channel creation, although channels may also advect without melting for many tens of kilometers. Channels can be out of hydrostatic equilibrium depending on their width and the upstream melt history. Inverting surface elevation for ice thickness using hydrostatic equilibrium in those areas is erroneous, and corresponding observational evidence is presented at RBIS by comparing the hydrostatically inverted ice thickness with radar measurements. The model shows that channelized melting imprints the flow field characteristically, which can result in enhanced horizontal shearing across channels. This is exemplified for a channel at RBIS using observed surface velocities and opens up the possibility to classify channelized melting from space, an important step towards incorporating these effects in ice-ocean models.

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

“…These surface depressions reflect basal incisions resulting in curvilinear tracts of thin ice. In some areas, ice shelf channels are twice as thin as their surroundings (Drews, 2015). However, the impact of ice shelf channels on ice shelf integrity is yet unclear because, on the one hand, excessive basal melting beneath ice shelf channels may prevent ice-shelf-wide thinning (Gladish et al, 2012;Millgate et al, 2013) but, on the other hand, increased crevassing due to channel carving may structurally weaken the ice shelf .…”

“…Analyses on Derwael Ice Rise Callens et al, 2016) and the larger catchment area suggest that the RBIS is a relatively stable sheet-shelf system on millennial timescales. The RBIS contains a number of ice shelf channels (Drews, 2015, and arrows in Fig. 2e), many of which start at the grounding line and extend over 230 km to the ice shelf front.…”

“…2e) by imposing hydrostatic equilibrium on surface freeboard (Bindschadler et al, 2011b;Chuter and Bamber, 2015;Drews, 2015) derived from the TanDEM-X satellites. The details of hydrostatic inversion are presented in the following two sections.…”

“…Although this is not a direct validation, as the field data cover a different period, the comparison is insightful to understand the spatial variability in our LBMB field. The derived LBMB is only valid in freely floating areas, which excludes not only the grounding zone but also other small-scale features such as ice shelf channels where viscous inflow can occur (Humbert et al, 2015;Drews, 2015). (Examples where this may be the case are discussed in Sect.…”

Modelled fracture and calving on the Totten Ice Shelf

“…The across flow features are hypothesised 20 to be the source of across flow surface features observed downstream on the Totten IS. It is possible that along flow basal crevasses could be a nucleus for the formation of basal channels, which subsequently grow by enhanced melting (Drews, 2015). This is a potential mechanism for the development of grounding-line sourced channels, the cause of which can be unclear in the absence of obvious subglacial hydrology (Alley et al, 2016).…”