Abstract
ABSTRACTDetermining the position and stability of the grounding line of a marine ice sheet is a major challenge for ice-sheet models. Here, we investigate the role of lateral shear and ice-shelf buttressing in grounding line dynamics by extending an existing boundary layer theory to laterally confined marine ice sheets. We derive an analytic expression for the ice flux at the grounding line of confined marine ice sheets that depends on both local bed properties and non-local ice-shelf properties. Application of these results to a laterally confined version of the MISMIP 1a experiment shows that the boundary condition at the ice-shelf front (i.e. the calving law) is a major control on the location and stability of the grounding line in the presence of buttressing, allowing for both stable and unstable grounding line positions on downwards sloping beds. These results corroborate the findings of existing numerical studies that the stability of confined marine ice sheets is influenced by ice-shelf properties, in contrast to unconfined configurations where grounding line stability is solely determined by the local slope of the bed. Consequently, the marine ice-sheet instability hypothesis may not apply to buttressed marine ice sheets.
Highlights
Satellite observations of surface elevation and velocity changes of the ice sheets show widespread dynamic thinning of outlet glaciers and ice streams in Greenland and West Antarctica (e.g. Pritchard and others, 2009; Shepherd and others, 2012)
Many existing studies investigating grounding line dynamics focus on laterally unconfined marine ice sheets that transition into freely floating ice shelves (e.g. Nowicki and Wingham, 2008; Durand others, 2009a; Tsai and others, 2015)
In the analysis described below, we first consider the dynamics of the ice shelf separately from the grounded ice sheet
Summary
Satellite observations of surface elevation and velocity changes of the ice sheets show widespread dynamic thinning of outlet glaciers and ice streams in Greenland and West Antarctica (e.g. Pritchard and others, 2009; Shepherd and others, 2012). Many existing studies investigating grounding line dynamics focus on laterally unconfined marine ice sheets that transition into freely floating ice shelves (e.g. Nowicki and Wingham, 2008; Durand others, 2009a; Tsai and others, 2015) In this case, the ice-shelf extent and configuration do not affect the grounded ice sheet and its dynamics can be modelled independently of the ice shelf (MacAyeal and Barcilon, 1988). Analytic studies of confined marine ice sheets have mainly focused on the ice shelf, in particular on identifying the boundary layer structure of confined ice shelves and/or on deriving solutions of the ice velocity in the downstream parts of the ice shelf (e.g. Hindmarsh, 2012; Pegler and others, 2013; Wearing and others, 2015; Pegler, 2016) This has led to the development of models that parameterise the effect of buttressing in laterally integrated ‘flow-line’ models (Dupont and Alley, 2005; Hindmarsh, 2012; Pegler, 2016). Readers not interested in the details of the derivation of the ice flux expression can skip Sections 3 and 4
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
