09 Jan 2023
 | 09 Jan 2023

Revisiting the role of vertical shear in analytic ice shelf models

Chris Miele, Timothy C. Bartholomaus, and Ellyn M. Enderlin

Abstract. Analytic modeling of ice shelf flow began when Weertman derived an expression for the strain rates within an unconfined shelf, of uniform thickness, extending only in one direction. Nearly two decades later, Thomas generalized Weertman's analysis to ice shelves of nonuniform thickness, deriving one of the most well-known analytic models in glaciology: . However, despite the prevalence of this model in both historical and contemporary texts, there remain persistent miscommunications regarding the role of vertical shear in its construction. In Thomas' original approach, vertical shear stress was considered negligible in the stress balance; in a significant contrast, the same model is typically derived in contemporary texts by the neglect of basal resistance. These two approaches are not equivalent, and yet, it remains common to misinterpret vertical shear stress as typically neglected in current ice shelf modeling studies. This manuscript provides clarification on this pervasive misconception. We emphasize that vertical shear stress should not be interpreted as negligible in the construction of general shallow shelf models. However, we also demonstrate that the vertical shear stress inherent in Thomas' expression does not give rise to a well-defined vertical shear strain rate. For situations in which vertical shear stress in shallow ice shelf models is of interest, we provide guidance on how to best calculate it.

Chris Miele et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-1310', Anonymous Referee #1, 26 Jan 2023
    • AC1: 'Reply on RC1', Chris Miele, 27 Jan 2023
  • RC2: 'Review of “Revisiting the role of vertical shear in analytic ice shelf models” by C. Miele et al.', Anonymous Referee #2, 16 Mar 2023
    • AC2: 'Reply on RC2', Chris Miele, 16 Mar 2023
  • RC3: 'Comment on egusphere-2022-1310', Josefin Ahlkrona, 21 Mar 2023
    • AC3: 'Reply on RC3', Chris Miele, 21 Mar 2023
  • RC4: 'Comment on egusphere-2022-1310', Anonymous Referee #4, 21 Mar 2023
    • AC4: 'Reply on RC4', Chris Miele, 21 Mar 2023
  • EC1: 'Editor Comment on egusphere-2022-1310', Reinhard Drews, 23 Mar 2023

Chris Miele et al.

Chris Miele et al.


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Short summary
Vertical shear stress (the stress orientation usually associated with vertical gradients in horizontal velocities) is a key component of the stress balance of ice shelves. However, partly due to historical assumptions, vertical shear is often misspoken of today as "negligible" in ice shelf models. We address this miscommunication, providing conceptual guidance regarding this often-misrepresented stress. Fundamentally, vertical shear is required to balance thickness gradients in ice shelves.