Glacier–plume or glacier–fjord circulation models? A 2-D comparison for Hansbreen–Hansbukta system, Svalbard

Eva De Andrés,Jaime Otero,Francisco J. Navarro,Waldemar Walczowski

doi:10.1017/jog.2021.27

Abstract

AbstractUp to 30% of the current tidewater mass loss in Svalbard corresponds to frontal ablation through submarine melting and calving. We developed two-dimensional (2-D) glacier–line–plume and glacier–fjord circulation coupled models, both including subglacial discharge, submarine melting and iceberg calving, to simulate Hansbreen–Hansbukta system, SW Svalbard. We ran both models for 20 weeks, throughout April–August 2010, using different scenarios of subglacial discharge and crevasse water depth. Both models showed large seasonal variations of submarine melting in response to transient fjord temperatures and subglacial discharges. Subglacial discharge intensity and crevasse water depth influenced calving rates. Using the best-fit configuration for both parameters our two coupled models predicted observed front positions reasonably well (±10 m). Although the two models showed different melt-undercutting front shapes, which affected the net-stress fields near the glacier front, no significant effects on the simulated glacier front positions were found. Cumulative calving (91 and 94 m) and submarine melting (108 and 118 m) along the simulated period showed in both models (glacier–plume and glacier–fjord) a 1:1.2 ratio of linear frontal ablation between the two mechanisms. Overall, both models performed well on predicting observed front positions when best-fit subglacial discharges were imposed, the glacier–plume model being 50 times computationally faster.

Highlights

Mass losses by glaciers and ice caps are projected to account for 79–157 mm of global mean sea-level rise (SLR) to the end of the 21st century, depending on the emission scenario (Huss and Hock, 2015)
Another characteristic common to the three scenarios, despite having different discharge fluxes, is that the submarine melt rates (SMRs) produced until week 7 is
An important aspect is that, in the plume model, maximum SMR takes place at the fjord surface (Fig. 4a), except for the first weeks of Scenario 0, when the maximum SMR occurs at intermediate depths, between 16 and 27 m

Summary

Introduction

Mass losses by glaciers and ice caps (glaciers) are projected to account for 79–157 mm of global mean sea-level rise (SLR) to the end of the 21st century, depending on the emission scenario (Huss and Hock, 2015). They entrain large volumes of ambient fjord waters, increasing their initial volume by more than an order of magnitude (Mortensen and others, 2013; Mankoff and others, 2016) and acting as the engine of convection-driven circulation in the fjords (Motyka and others, 2013; De Andrés and others, 2018), favouring the input of warmer ocean waters (Straneo and others, 2011) Due to their turbulent nature, the buoyant plumes enable ocean heat transfer to the ice, enhancing submarine glacier-front melting (Sciascia and others, 2013; Xu and others, 2013; Kimura and others, 2014; Slater and others, 2015, 2018). Submarine melting results in a change of shape of the submerged part of the glacier front that has an impact on calving rates (O’Leary and Christoffersen, 2013; Luckman and others, 2015; De Andrés and others, 2018; Schild and others, 2018; Vallot and others, 2018; How and others, 2019) by altering

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Conclusion