Abstract
Abstract. A recent ocean modelling study indicates that possible changes in circulation may bring warm deep-ocean water into direct contact with the grounding lines of the Filchner–Ronne ice streams, suggesting the potential for future ice losses from this sector equivalent to ~0.3 m of sea-level rise. Significant advancements have been made in our knowledge of both the basal topography and ice velocity in the Weddell Sea sector, and the ability to accurately model marine ice sheet dynamics, thus enabling an assessment to be made of the relative sensitivities of the diverse collection of ice streams feeding the Filchner–Ronne Ice Shelf. Here we use the BISICLES ice sheet model, which employs adaptive-mesh refinement to resolve grounding line dynamics, to carry out such an assessment. The impact of realistic perturbations to the surface and sub-shelf mass balance forcing fields from our 2000-year "reference" model run indicate that both the Institute and Möller ice streams are highly sensitive to changes in basal melting either near to their respective grounding lines, or in the region of the ice rises within the Filchner–Ronne Ice Shelf. These same perturbations have little impact, however, on the Rutford, Carlson or Foundation ice streams, while the Evans Ice Stream is found to enter a phase of unstable retreat only after melt at its grounding line has increased by 50% of likely present-day values.
Highlights
IntroductionNear to the grounding lines of these ice streams, the bed topography has been observed to deepen significantly inland (a configuration often called a reverse slope), and to be smooth, with few potential pinning points (Ross et al, 2012)
A recent geophysical survey has highlighted the potential for a marine ice sheet instability (e.g. Mercer, 1978) at both the Institute and Möller ice streams in the Weddell Sea sector of West Antarctica
From this it is clear that the ice streams discharging into the Filchner–Ronne Ice Shelf can be divided into three groups: (1) those that respond very slowly and require large changes to the forcing fields to produce any retreat; (2) those quick to respond to changes in melt at their grounding lines; and (3) those which respond very quickly to a melt increase, but only after a threshold has been passed
Summary
Near to the grounding lines of these ice streams, the bed topography has been observed to deepen significantly inland (a configuration often called a reverse slope), and to be smooth, with few potential pinning points (Ross et al, 2012). While these ice streams currently show no signs of the dynamicthinning behaviour that has been observed in the Amundsen Sea region (Payne et al, 2004; Joughin et al, 2010; Pritchard et al, 2012), ocean modelling studies suggest that changes to current circulation patterns may result in greater melting at the base of the Filchner–Ronne Ice Shelf (Hellmer et al, 2012). In this paper we employ an ice sheet model to investigate the possibility that thinning of the Filchner–Ronne Ice Shelf, and the consequent reduction of buttressing at the grounding lines of its tributary ice streams, could lead to the loss of grounded ice (cf. the Larsen B Ice Shelf collapse; Scambos et al, 2004).
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