Calibration of a higher-order 3-D ice-flow model of the Morteratsch glacier complex, Engadin, Switzerland

Abstract

We have reconstructed the ice thickness distribution of the Morteratsch glacier complex, Switzerland, and used this to simulate its flow with a higher-order 3-D model. Ice thickness was measured along transects with a ground-penetrating radar and further extended over the entire glacier using the plastic flow assumption and a distance-weighted interpolation technique. We find a maximum ice thickness of 350 ±52.5 m for the central trunk of Vadret da Morteratsch, resulting from a bedrock overdeepening. The average thickness of the glacier complex is 72.2 ±18.0 m, which corresponds to a total ice volume of 1.14 ± 0.28 km3. The flow of the glacier is modelled by tuning the rate factor and the sliding parameters taking into account higher-order terms in the force balance. The observed velocities can be reproduced closely (root-mean-square error of 15.0 m a-1, R2 = 0.93) by adopting a sliding factor of 12 x 10–16 m7 N–3 a-1 and a rate factor of 1.6 x 10-16 Pa-3 a-1 . In this setting, ice deformation accounts for 70% of the surface velocity and basal sliding for the remaining 30%. The modelled velocity field reaches values up to 125 ma-1, but also indicates an almost stagnant front and confluence area, which are crucial for understanding the ongoing glacier retreat.

Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change

“…Since both the rate factor (A) and sliding parameter (β) depend on driving stress (Flowers et al, 2008;Zekollari et al, 2013), one can keep the same surface velocities by reducing one parameter and increasing the other. Hence it is challenging to pick a unique combination without more empirical knowledge about their relative importance (Le Meur and Vincent, 2003;Aðalgeirsdóttir et al, 2011;Zekollari et al, 2013). This underlines the motivation behind keeping our ensemble after the calibration.…”

“…In sparsely measured areas, ice thickness H was estimated directly from the surface slope α, assuming perfect plasticity (Paterson, 1994, p. 240). Based on detailed ice thickness measurements and information on the surface slope on Midtdalsbreen, a yield stress of 150-180 kPa was used, in agreement with other mountain glaciers (Cuffey and Paterson, 2010, p. 297;Zekollari et al, 2013). Over the flat areas near ice divides and ice ridges, as well as near ice margins, manual extrapolation was required to obtain a smooth ice surface (K. Melvold, personal communication, 2009).…”

Calibration of a mathematical model of Marukh Glacier, Western Caucasus

“…В настоящей работе ледник считается изо термическим, поэтому реологическая функция заменяется на параметр A fl . Вектор скорости ба зального (глыбового) скольжения считается про порциональным напряжению на нижней грани це в третьей степени [19]:…”

Sensitivity, stability and future evolution of the world's northernmost ice cap, Hans Tausen Iskappe (Greenland)

“…This HO approximation and its numerical implementation (Fürst et al, 2011) have been successfully applied at different scales, ranging from small mountain glaciers (Zekollari et al, 2013(Zekollari et al, , 2014Zekollari and Huybrechts, 2015) to entire ice sheets (Fürst et al, , 2015. All ice-free patches located within the present-day ice cap, which mainly coincide with mountain peaks and steep ridges, are explicitly kept ice-free in the simulations, as the processes that prevent accumulation here (mostly snowdrift by wind and related to the steep topography) are not captured in our models.…”

“…A variety of recent studies exist for individual glaciers (e.g. Le Meur and Vincent, 2003;Jouvet et al, 2009Jouvet et al, , 2011Aðalgeirsdóttir et al, 2011;Duan et al, 2012;Zekollari et al, 2013Zekollari et al, , 2014Hannesdóttir et al, 2015;Réveillet et al, 2015), but for ice caps such detailed studies are limited (Aðalgeirsdóttir et al, 2005(Aðalgeirsdóttir et al, , 2006Flowers et al, 2005Flowers et al, , 2007Flowers et al, , 2008 Published by Copernicus Publications on behalf of the European Geosciences Union.…”