25 Feb 2021

25 Feb 2021

Review status: this preprint is currently under review for the journal TC.

Controls on Greenland moulin geometry and evolution from the Moulin Shape model

Lauren C. Andrews1, Kristin Poinar2,3, and Celia Trunz4 Lauren C. Andrews et al.
  • 1Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
  • 2Department of Geology, University at Buffalo, Buffalo, NY, 14260, USA
  • 3Research and Education in eNergy, Environment and Water (RENEW) Program, University at Buffalo, Buffalo, NY, 14260, USA
  • 4Geosciences Department, University of Arkansas, Fayetteville, AR, 72701, USA

Abstract. Nearly all meltwater from glaciers and ice sheets is routed englacially through moulins, which collectively comprise approximately 10–14 % of the efficient englacial–subglacial hydrologic system. Therefore, the geometry and evolution of moulins has the potential to influence subglacial water pressure variations, ice motion, and the runoff hydrograph delivered to the ocean. We develop the Moulin Shape (MouSh) model, a time-evolving model of moulin geometry. MouSh models ice deformation around a moulin using both viscous and elastic rheologies and models melting within the moulin through heat dissipation from turbulent water flow, both above and below the water line. We force MouSh with idealized and realistic surface melt inputs. Our results show that variations in surface melt change the geometry of a moulin by approximately 30 % daily and by over 100 % seasonally. These size variations cause observable differences in moulin water storage capacity, moulin water levels, and subglacial channel size compared to a static, cylindrical moulin. Our results suggest that moulins are significant storage reservoirs for meltwater, with storage capacity and water levels varying over multiple timescales. Representing moulin geometry within subglacial hydrologic models would therefore improve their accuracy, especially over seasonal periods or in regions where overburden pressures are high.

Lauren C. Andrews 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 tc-2021-41', Anonymous Referee #1, 07 Apr 2021
  • RC2: 'Comment on tc-2021-41', Anonymous Referee #2, 31 Jul 2021

Lauren C. Andrews et al.

Data sets

Data supporting "Controls on Greenland moulin geometry and evolution from the Moulin Shape model" Andrews, Poinar, & Trunz

Model code and software

Moulin Shape (MouSh) model Andrews, Poinar, & Trunz

Lauren C. Andrews et al.


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Short summary
We introduce a model for moulin geometry motivated by the wide range of sizes and shapes of explored moulins. Moulins comprise 10–14 % of the Greenland en/subglacial hydrologic system and act as time-varying water storage reservoirs. Daily variations in moulin size (~30 %) exceed those in subglacial channel size (~10 %), especially during periods of changing melt. Moulin shape modulates the efficiency of the subglacial system that controls ice flow and should thus be included in hydrologic models.