Elmer/Ice News

Significant change in the dynamics of tidewater glaciers after a calving event are mainly tied to a sudden loss of resistive stresses. This article investigates how such a stress perturbation affects the whole glacier upstream. Simulations (using Elmer/Ice) and perturbation theory revealed that calving events and subsequent terminus readvance produce quasi-periodic, sawtooth oscillations in stress that originate at the terminus and propagate upstream with speeds significantly exceeding ice velocities. In laterally resisted glaciers, these signals decay within an upstream distance equivalent to a few ice thicknesses. Terminus fluctuations caused by individual calving events tend to be much higher frequency than climate variations. Thus, individual calving events have little direct impact on the viscous delivery of ice to the terminus. This suggests that the primary mechanism by which calving events can trigger instability is by causing fluctuations in stress that weaken the ice and lead to additional calving and sustained terminus retreat. Our results further demonstrate a stronger response to calving events in simulations that include the full stress tensor, highlighting the importance of accounting for higher order stresses when developing calving parameterizations for tidewater glaciers.

Read more: Amundson, J., M. Truffer, and T. Zwinger, 2022. Tidewater glacier response to individual calving events. Journal of Glaciology, 1-10, doi:10.1017/jog.2022.26 

The response of glaciers in Tibet Plateau and the wider area of High Mountain Asia to on-going and future climate change is a topic of concern. Little work has been done on small Tibetan Plateau glacier responses to climate warming with mechanistic models, but no simulations on a large Tibet glacier to our knowledge. We apply three-dimensional full-Stokes model to simulate the evolution of Da Anglong Glacier, a large glacier (6.66 km²) in the western Tibet Plateau from the year 2016 to 2098, using projected temperatures and precipitations from the 25-km-resolution RegCM4 nested within 3 Earth System Models simulating the RCP2.6 and RCP8.5 scenarios. The surface mass balance is estimated by degree-day method using a quadratic elevation-dependent precipitation gradient. A geothermal flux of 60 mW m^-2 produces a better fit to measured surface velocity than lower heat fluxes, and represents a new datum in this region of sparse heat flux observations. The ensemble mean simulated glacier volume loss during 2016-2098 amounts to 38% of the glacier volume in the year 2016 under RCP2.6 and 83% under RCP8.5. Simulation from 2016 to 2098 without ice dynamics leads to an underestimation of ice loss of 22-27% under RCP2.6 and 16-24% under RCP8.5, showing that ice dynamics play an important amplifying factor in ice loss for this glacier, unlike for small Tibetan glaciers where SMB dominates glacier change.

Read more:  Zhao W., L. Zhao, L. Tian, M. Wolovick and J.C. Moore, 2022. Simulating the Evolution of Da Anglong Glacier, Western Tibetan Plateau over the 21st Century. Water, 14(2), 271, doi:10.3390/w14020271 

CSC and IGE invite you to join the 2022 online Elmer/Ice workshop.  The idea behind this workshop is to listen to and discuss  talks given by developers and - most importantly - the users (=you). Hence we encourage you to submit a title (no abstract needed) of a 10 - 15 minute talk. You can do so in the registration form, which is accessible under the link https://ssl.eventilla.com/event/JBab5  There you need to provide your name + valid email address, else registration and attendance is free of charge

It will be held  as  a Zoom-Webinar on Wednesday,  2. February, 2022, from 9 am-12 am Central European Time (CET = UTC+1) . We apologize that this schedule leads to inconvenient times, mainly for the Americas and a wide range of the Pacific region. Nevertheless, we will record the event and make those talks for which we get permission available online.

Looking forward to seeing you, 

Olivier Gagliardini (IGE), Thomas Zwinger and the Elmer-Team at CSC