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Ice Sheet Modelling & Scientific Workflows in Glaciology

Collaborative research on ice sheet modelling & scientific workflows to predict sea level rise. Utilizing Elmer/Ice software and HiDEM for ice calving simulations. Development of abstract workflows for glacier models.

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Ice Sheet Modelling & Scientific Workflows in Glaciology

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  1. HPC use case:Glaciology/Ice sheet modelling and supporting scientific workflows Helmut Neukirchen helmut@hi.is University of Iceland Using slides from Shahbaz Memon, Dorothée Vallot and Thomas Zwinger

  2. About me • Helmut Neukirchen. • Professor of Computer Science and Software Engineering, University of Iceland. • Software Engineering for Distributed Systems, e.g. HPC/eScience such as scientific workflows. • Collaboration with Jülich Supercomputing Centre, Germany. • Morris Riedel coming every year as guest professor to Uni Iceland. • Worthwhile as associated partner of NeIC just like partners in Estonia. • Organised HPC Workshop in Iceland this August. • Supported by NeIC, success according to participant evaluation. Helmut Neukirchen: Ice sheet modelling / Scientific workflows

  3. Context of use case • NordForsk funded Nordic Centre of Excellence eSTICC (eScience Tools for Investigating Climate Change at High Northern Latitudes). • Climate modelling (millions of CPU hours needed in Norway), • Ice sheet modelling (to predict sea level rise): • 2 senior researchers: • Helmut Neukirchen (Scientific workflows, Uni Iceland), • Thomas Zwinger (Glaciology, CSC, Finland). • 2 PhD students: • Shahbaz Memon (Scientific workflows, Uni Iceland and Jülich Supercomputing Centre, Germany), • Dorothée Vallot (Glaciology, Uni Uppsala, Sweden). Helmut Neukirchen: Ice sheet modelling / Scientific workflows

  4. Use case: Glacier flow and calving • Ice deformation and sliding • Modelled as a continuous process (finite element method). • Calving • Modelled as discrete process (discrete element model). Helmut Neukirchen: Ice sheet modelling / Scientific workflows

  5. Elmer/Ice • Elmer: Finite Element Method (FEM) Software. • Elmer/Ice add-on for modelling ice sheet flow. • Mainly developed by Thomas Zwinger at CSC, • Open source, • Parallel processing. • In FEM, finite elements may have different sizes (and even shapes). • Adaptive mesh of finite elements: fine grained where a lot of stress occurs, coarse where minor stress. • Helps to save CPU time. 5 Helmut Neukirchen: Ice sheet modelling / Scientific workflows

  6. Helsinki Discrete Element Model (HiDEM) for ice calving Water depth Ice Water • Particle-based model of calving [Jan Åström et al.: A Particle-based simulation model for glacier dynamics, Cryosphere, 2013]. • Parallel processing, • Closed-source. • Only available on CSC cluster Sisu. • All particles of same size. • High spatial (in the size of the cracks) and temporal (spatial scales divided by speed of sound) resolution. • Computationally very expensive. 6 Helmut Neukirchen: Ice sheet modelling / Scientific workflows

  7. Scientific workflow: coupling FEM & DEM Shared Preprocessing Serial Generate Mesh Serial ElmerSolver Parallel Cluster 1 Elmer-> Particle Serial Loop Until Num. Observations Originally: 2000 Lines of code shell script Parallel Particle Calving Cluster 2 Particle-> Elmer Serial Workflow engine of UNICORE middleware Helmut Neukirchen: Ice sheet modelling / Scientific workflows

  8. Use Case: Kronebreen glacier, Spitsbergen, Svalbard • One of the largest glacier streams on Svalbard. • Draining about 690 km2. • Average speed: 2 m/d. • Status: • Executed models coupled via shell script by Dorothée Vallot. • Many iteration desirable: comparing model with reality observed for every 11 days for 3 years. • 5000 CPU h FEM + 20 000 CPU h DEM for every iteration. • Abstract scientific workflows developed without any allocated CPU time by Shahbaz Memon. • Tested using local runs with dummy calving. Helmut Neukirchen: Ice sheet modelling / Scientific workflows

  9. Status and Conclusion • UNICORE middleware for workflows operational at CSC since last week. • Elmer/Ice and HiDEM anyway installed at CSC. • Now, waiting for CPU cycle allocation at CSC. • 200 000 h applied for via Dellingr last Thursday. • Would allow a few iterations of coupled ice sheet models for Kronebreen. • Both needed by Dorothée Vallot to finish her PhD on modelling Kronebreen and by Shahbaz Memon to evaluate his workflow abstraction. • Outlook: generic one-click ice sheet simulation possible for glaciologists via Shahbaz’s workflow. • May result in need of even further CPU hours. • Note: in addition to glaciologists in Uppsala and Helsinki, also glaciologists at University of Iceland do extensive simulations (coupled climate/ice sheet). • Use cluster from Danish Met. Office (located at Icelandic Met. Office), but also Icelandic HPC cluster Garpur for smaller trial runs. Helmut Neukirchen: Ice sheet modelling / Scientific workflows

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