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Results from the Ice Thickness Models Intercomparison eXperiment Phase 2 (ITMIX2)

Farinotti, Daniel and Brinkerhoff, Douglas J. and Fürst, Johannes J. and Gantayat, Prateek and Gillet-Chaulet, Fabien and Huss, Matthias and Leclercq, Paul W. and Maurer, Hansruedi and Morlighem, Mathieu and Pandit, Ankur and Rabatel, Antoine and Ramsankaran, RAAJ and Reerink, Thomas J. and Robo, Ellen and Rouges, Emmanuel and Tamre, Erik and van Pelt, Ward J. J. and Werder, Mauro A. and Azam, Mohod Farooq and Li, Huilin and Andreassen, Liss M. (2021) Results from the Ice Thickness Models Intercomparison eXperiment Phase 2 (ITMIX2). Frontiers in Earth Science, 8 . Art. No. 571923. ISSN 2296-6463.

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Knowing the ice thickness distribution of a glacier is of fundamental importance for a number of applications, ranging from the planning of glaciological fieldwork to the assessments of future sea-level change. Across spatial scales, however, this knowledge is limited by the paucity and discrete character of available thickness observations. To obtain a spatially coherent distribution of the glacier ice thickness, interpolation or numerical models have to be used. Whilst the first phase of the Ice Thickness Models Intercomparison eXperiment (ITMIX) focused on approaches that estimate such spatial information from characteristics of the glacier surface alone, ITMIX2 sought insights for the capability of the models to extract information from a limited number of thickness observations. The analyses were designed around 23 test cases comprising both real-world and synthetic glaciers, with each test case comprising a set of 16 different experiments mimicking possible scenarios of data availability. A total of 13 models participated in the experiments. The results show that the inter-model variability in the calculated local thickness is high, and that for unmeasured locations, deviations of 16% of the mean glacier thickness are typical (median estimate, three-quarters of the deviations within 37% of the mean glacier thickness). This notwithstanding, limited sets of ice thickness observations are shown to be effective in constraining the mean glacier thickness, demonstrating the value of even partial surveys. Whilst the results are only weakly affected by the spatial distribution of the observations, surveys that preferentially sample the lowest glacier elevations are found to cause a systematic underestimation of the thickness in several models. Conversely, a preferential sampling of the thickest glacier parts proves effective in reducing the deviations. The response to the availability of ice thickness observations is characteristic to each approach and varies across models. On average across models, the deviation between modeled and observed thickness increase by 8.5% of the mean ice thickness every time the distance to the closest observation increases by a factor of 10. No single best model emerges from the analyses, confirming the added value of using model ensembles.

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Additional Information:© 2021 Farinotti, Brinkerhoff, Fürst, Gantayat, Gillet-Chaulet, Huss, Leclercq, Maurer, Morlighem, Pandit, Rabatel, Ramsankaran, Reerink, Robo, Rouges, Tamre, van Pelt, Werder, Azam, LI and Andreassen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Received: 12 June 2020; Accepted: 28 September 2020; Published: 21 January 2021. The work is a contribution of the Working Group of Ice Thickness Estimation, which acted under the umbrella of the International Association of Cryospheric Sciences. We are thankful to all researchers that contributed to the dataset of ITMIX phase one (, as well as to Ivan Lavrentiev, Geir Moholdt, and Thomas Schuler for the additional data provided for Austre Groenfjordbreen, and to Etienne Berthier for providing the DEM of Chhota Shigri. Results provided by JF are based on numerical simulations conducted at the high-performance computing center of the Regionales Rechenzentrum Erlangen (RRZE) of the University of Erlangen-Nuremberg. JF was financed by the German Research Foundation (DFG) within the Svalbard-iFLOWbed project, Grant FU1032/1-1. AR and FG acknowledge the support of LabEx OSUG@2020 (Investissements d’avenir—ANR10 LABX56). MW was partly funded by the ESA project Glaciers_cci (4000109873/14/I-NB). Data Availability Statement: The i) datasets originally distributed to the participating modellers, ii) results submitted by every modeller, iii) data shown in the main figures, as well as iv) an extended set of figures are found at The source code for the ensemble-approach GilletChaulet is available at Author Contributions: DF designed the study, with input from JF, MH, LA and other participants of ITMIX phase one. DF, DB, JF, PG, FG, MH, PL, HM, MM, AP, AR, RR, TR, ElR, EmR, ET, WvP, and MW performed the modeling with individual approaches. MA and AP provided data for Chotta Shigri Glacier. With inputs from all co-authors, DF evaluated the results, wrote the manuscript, and designed and produced all figures and tables. Conflict of Interest: Author AP was employed by the company Tata Consultancy Services (TCS). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer (DS) declared a past co-authorship with one of the authors (MM) to the handling editor.
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)FU1032/1-1
Agence Nationale pour la Recherche (ANR)ANR10 LABX56
European Space Agency4000109873/14/I-NB
Subject Keywords:glaciers, ice caps, ice thickness, modeling, intercomparison
Record Number:CaltechAUTHORS:20210226-090334959
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Official Citation:Farinotti D, Brinkerhoff DJ, Fürst JJ, Gantayat P, Gillet-Chaulet F, Huss M, Leclercq PW, Maurer H, Morlighem M, Pandit A, Rabatel A, Ramsankaran R, Reerink TJ, Robo E, Rouges E, Tamre E, van Pelt WJJ, Werder MA, Azam MF, Li H and Andreassen LM (2021) Results from the Ice Thickness Models Intercomparison eXperiment Phase 2 (ITMIX2). Front. Earth Sci. 8:571923. doi: 10.3389/feart.2020.571923
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108234
Deposited By: Tony Diaz
Deposited On:26 Feb 2021 17:19
Last Modified:26 Feb 2021 17:19

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