Polar and Alpine Events Calendar
We are very pleased to announce the first “Landscapes Live” online seminar of the summer 2021 block by Kelin Whipple (Arizona State) that will occur this week on Thursday 6th May at 7 am PST / 10 am EST / 3 pm GMT / 4 pm CET on:
“Quantifying the Role of Climate in Landscape Evolution”
This seminar will be live on Zoom and open to anyone interested (with a limit of 300 participants). You can register in advance for this Zoom meeting here: https://us02web.zoom.us/meeting/register/tZUqcOquqj0iGt11H6ZAYe7LzsKfopS35Bcl
Abstract: Climate influences surface processes in myriad ways. Here I focus on the influence of climate on the steady-state relief structure in tectonically active landscapes, with a particular focus on the steepness of bedrock channel profiles. Specifically, I focus on the question of how climate modulates the relationship between channel steepness (or topographic relief) and erosion rate (as a proxy for rock uplift rate in steady-state landscapes). This is importantly, if somewhat subtly, different from asking how climate influences erosion rate, which is not always the best way to pose the question. The goal of quantifying the role of climate in long-term landscape evolution has proven surprisingly elusive, as I will briefly review. The multitude of controls on channel steepness and the complexity added by thresholds for mobilizing coarse bed material and eroding bedrock are partly responsible. There is, however, well-developed theory for how the interaction of erosion thresholds and the stochastic distribution of floods combine to influence steady-state channel steepness. This theory predicts that runoff variability is a key control on the non-linearity of the relationship between erosion rate and channel steepness. Importantly, we now have a sound fundamental understanding of the controls on runoff variability, which sets up testable hypotheses, including predictions for the controls on the strength of climate-tectonic feedbacks in active orogens. As a teaser, it is possible that in many settings plant ecosystems dictate the strength of coupling between climate and tectonics, but not in the way vegetation is usually thought to influence erosion rates. Paired with these advances – and the related observation that mean annual rainfall emerges as a better climate metric than mean annual runoff – I will present a new channel steepness metric, ksn-q (proportional to unit stream power), that folds in climatic information by weighting drainage area by mean annual rainfall. I will share unpublished tests demonstrating the promise of this simple metric for capturing key aspects of the influence of climate on channel steepness. Armed with this new metric and understanding emerging from theory outlined above, I will highlight and discuss key findings and implications of the recent study by Adams et al. (2020). Adams et al. exploited the wealth of catchment-mean cosmogenic 10-Be erosion rate data in the eastern Himalaya to shed light on the relationships among topography, mean annual rainfall, and erosion rate. They find, quite shockingly, that a simple stream power model that incorporates the joint influence of thresholds and stochastic floods explains much of the observed influence of climate. Limitations and likely controls on remaining scatter will be discussed.
After registering, you should receive a confirmation email containing information about joining the meeting. We will also post the Zoom link for this meeting on the seminar website: https://osur.univ-rennes1.fr/LandscapesLive/.
The Landscapes Live online seminar series will then continue the following weeks with:
- Thursday 13th May at 3 pm GMT/ 4 pm CET: Benjamin Keisling, Lamont-Doherty Earth Observatory
- Thursday 20th May at 3 pm GMT/ 4 pm CET: Tamara Pico, University of California, Santa Cruz
- Thursday 27th May at 3 pm GMT/ 4 pm CET: Seulgi Moon, University of California, Los Angeles
- Thursday 3rd June at 3 pm GMT/ 4 pm CET: Giulia Sofia, University of Connecticut
- Thursday 10th June at 3 pm GMT/ 4 pm CET: Jane L. Andersen, Aarhus University
- Thursday 17th June at 3 pm GMT/ 4 pm CET: Laura Quick, University of Edinburgh
- Thursday 24th June at 3 pm GMT/ 4 pm CET: Anne Voigtländer, GFZ Potsdam
Previous talks are available on the website (https://osur.univ-rennes1.fr/LandscapesLive/).
The Landscapes Live team: Rebekah Harries, Michal Ben-Isreal, Pierre Valla, Philippe Steer, Steffi Tofelde, Charlie Shobe, Vivi Pederson and Boris Gailleton