We are very pleased to announce the first&n
bsp;“Landscapes Live” online seminar of the summer 20
21 block by Kelin Whipple (Arizona State) that w
ill occur this week on Thursday 6th May at&nb
sp;7 am PST / 10 am EST / 3 pm GMT / 4 pm CET on:
“Quantifying th e Role of Climate in Landscape Evolution”
This seminar will be live on Zoom and open to anyone int erested (with a limit of 300 participants). You can register in advance for this Zoom meeting here: https://us02web.zoom.us/meeting/register/tZUqcOquqj0iGt11H6ZAYe7Lzs KfopS35Bcl
Abstract: Climate in fluences surface processes in myriad ways. Here I focus on the influence of climate on the steady-state relief structure in tectonically active landsc apes, with a particular focus on the steepness of bedrock channel profiles. Specifically, I focus on the question of how climate modulates the relatio nship between channel steepness (or topographic relief) and erosion rate (a s a proxy for rock uplift rate in steady-state landscapes). This is importa ntly, if somewhat subtly, different from asking how climate influences eros ion rate, which is not always the best way to pose the question. The goal o f quantifying the role of climate in long-term landscape evolution has prov en surprisingly elusive, as I will briefly review. The multitude of control s on channel steepness and the complexity added by thresholds for mobilizin g coarse bed material and eroding bedrock are partly responsible. There is, however, well-developed theory for how the interaction of erosion threshol ds and the stochastic distribution of floods combine to influence steady-st ate channel steepness. This theory predicts that runoff variability is a ke y control on the non-linearity of the relationship between erosion rate and channel steepness. Importantly, we now have a sound fundamental understand ing of the controls on runoff variability, which sets up testable hypothese s, including predictions for the controls on the strength of climate-tecton ic feedbacks in active orogens. As a teaser, it is possible that in many se ttings plant ecosystems dictate the strength of coupling between climate an d tectonics, but not in the way vegetation is usually thought to influence erosion rates. Paired with these advances – and the related observation tha t 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 climati c information by weighting drainage area by mean annual rainfall. I will sh are unpublished tests demonstrating the promise of this simple metric for c apturing key aspects of the influence of climate on channel steepness. Arme d with this new metric and understanding emerging from theory outlined abov e, 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 catchme nt-mean cosmogenic 10-Be erosion rate data in the eastern Himalaya to shed light on the relationships among topography, mean annual rainfall, and eros ion rate. They find, quite shockingly, that a simple stream power model tha t incorporates the joint influence of thresholds and stochastic floods expl ains much of the observed influence of climate. Limitations and likely cont rols on remaining scatter will be discussed.
After registering, you shoul d receive a confirmation email containing information about joining the mee ting. We will also post the Zoom link for this meeting on the seminar websi te: https://osur.univ-rennes1.fr/LandscapesLive/.
The Landscapes Live online seminar series will the n continue the following weeks with:
Previous talks are available on the website (https://osur.univ-rennes1.fr/LandscapesLive/).
Landscapes Live is the EGU Geomorphology Division's virtual webinar series focused
on sharing exciting geomorphology research throughout the international sci
entific community. Feel free to contact us if you have questions or su
ggestions: This email address is being prot
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/p> Best wishes, The Landscapes Live team: Rebekah Harries, Michal Ben-Is
real, Pierre Valla, Philippe Steer, Steffi Tofelde, Charlie Shobe, Vivi Ped
erson and Boris Gailleton