Report: Exploring the Interplay between Solid Earth Tectonics and Surface Processes using Community Codes Mini-Workshop

AGU Fall Meeting 2013, San Francisco, USA

Workshop Conveners: Phaedra Upton1, Mark Behn2, John Jaeger3

1GNS Science, New Zealand; 2Woods Hole Oceanographic Institution; 3University of Florida

About 30 scientists with a wide range of interests spanning field-based to modeling studies, spent the Wednesday night of AGU at the Grand Hyatt San Francisco exploring the interplay between solid Earth tectonics and surface processes with an emphasis on using community codes. The workshop was associated with AGU sessions EP33B and EP43E/44A, sponsored by GeoPRISMS, and supported by the Community Surface Dynamics Modelling System (CSDMS). The workshop was prompted by the inclusion of a new Geodynamics Focus Research Group into CSDMS 2.0, co-chaired by Phaedra Upton (GNS Science, New Zealand) and Mark Behn (WHOI). The AGU sessions and the Mini-Workshop created an opportunity to bring together members of the long-term tectonics community with members of the CSDMS community, particularly those interested in surface processes in actively deforming terrestrial settings. The workshop began with half an hour of informal discussions over snacks and posters. The formal part of the evening began with a welcome and introduction from Peter van Keken, the incoming chair of GeoPRISMS. Phaedra Upton, co-chair of the Geodynamics FRG, introduced CSDMS and the Geodynamics FRG. She was followed by Irina Overeem (CSDMS) who gave an overview of the support, website, modelling tool, and educational repository offered by CSDMS. Three invited speakers, Ritski Huismans, Brian Yanites, and Louis Moresi then shared their thoughts and experiences using coupled modeling approaches to link solid Earth tectonics and surface processes. Ritski Huismans described his efforts to include surface processes into his geodynamic models. He discussed some of the computational issues of linking the two types of processes with significantly different spatial and temporal scales. He described how models have improved with increasing computational power allowing higher resolution. Brian Yanites talked about modelling surface processes as a geomorphologist working in tectonically active regions. He focused on rivers as “rivers (or glaciers) dictate orogen scale relief”. He discussed the commonly used streampower law and its limitations and showed a series of models of river incision in an uplifting region that took into account other mechanisms including bed properties (e.g., erodibility) and river capture. Louis Moresi, one of the developers of the geodynamics open source code Underworld, related many of the lessons they have learnt while building a versatile, multi-scale, community code. He conceded they did not reach all their goals, having produced a very powerful and versatile code but one which is challenging to use and thus has not been widely adopted by the community.

Following these three presentations, the floor was open for discussion. Themes that arose included:

  • The potential for more collaboration between CSDMS and the long term tectonics working group Computational Infrastructure for Geodynamics (CIG).
  • Coupling is important and interesting because of the potential for feedbacks between surface processes (e.g., erosion and re-deposition) on long term tectonic proecesses
  • We need to be careful to do the coupling correctly, this requires including researchers from both communities.
  • An important issue is the mismatch of spatial and temporal scales between tectonic and surface processes. What are the best computational methods to deal with these different scales?
  • As the community, we need to think about whether we should be moving toward meshless methods.
  • The importance of bookkeeping for stratigraphy. In coupling between a landscape evolution model and a tectonic code, the overlap is not just the 2D land surface, thus coupling needs to be in 3D extending to a depth beneath the surface that records deposition.
  • One action item that came out of the meeting is that there is immediate value in coupling a high resolution 2.5D tectonic model with a landscape evolution model.Specifically, while 3D is essential for some problems, it is not necessary for all problems and often a 2D model output (extrapolated into the 3rd dimension) is sufficient and has the advantage of being higher resolution and faster to run. Therefore, it was proposed that the Geodynamics Focused Research group works to release a 2D model into CSDMS soon. This model could be coupled with existing landscape evolution models to produce some simple test cases to look at key feedbacks between fault evolution and surface processes.

The meeting came to an end with a feeling of energy and momentum. However, it is important to keep the dialogue going. In particular, there are several upcoming meetings that are relevant to both the long term tectonics and surface processes communities:

We look forward to developments facilitated by linkages between GeoPRISMS and CSDMS.

Reference information
Exploring the Interplay between Solid Earth Tectonics and Surface Processes using Community Codes, Upton, P., Behn, M., Jaeger, J.

GeoPRISMS Newsletter, Issue No. 32, Spring 2014. Retrieved from http://geoprisms.nineplanetsllc.com