Collaborative Research: Climatic Control of Erosion Rates and Landscape Morphology - Quantifying the Influence of Fluvial Thresholds

Purdue University, West Lafayette IN

Investigators

Abstract

This project seeks to advance understanding of land surface response to climate change through study of evolving landforms on the Hawaiian islands. This research will improve scientists’ ability to decipher the record of past climates from landforms and to anticipate land surface response to future climate change. Planned research activities focus on the role of extreme events in canyon cutting – a topic that is central to landscape response to climate change but has received insufficient attention. The team will recruit two undergraduates from underrepresented communities in Hawaii to participate in the research effort and to attend an international professional conference to learn about opportunities and establish network connections. Outreach and hands-on public educational activities will be developed at both Arizona State University and the University of Indiana, including through participation of undergraduates in research efforts. All resulting research data will be made publicly available. This research will extend prior studies of the Hawaiian islands by examining landscapes across a span of islands, and thus landscape ages, and across the dramatic differences in rainfall between windward and leeward slopes, emphasizing the role of geomorphic thresholds and the extreme events that can exceed them. Preliminary investigation indicates that the kilometer-deep canyons common to all of the islands were cut rapidly to depths similar to the present day, after which incision stagnated because channel gradient decreased below a climate-dependent threshold for moving large boulders in channels. This study will systematically test the hypothesis that canyon cutting on the Hawaiian islands has been limited by boulder transport thresholds. A combination of methods will be deployed, including detailed field measurements, digital elevation model analyses, 40Ar/39Ar dating of inset lava flows, and estimates of catchment-mean erosion rates from cosmogenic 36Cl in magnetite in river sediment – a novel method only recently developed. This research represents an opportunity to advance understanding of climatic control on landscape evolution in general, and to quantify how fluvial incision thresholds critically modulate connections among climate, topography, and erosion rate. The Hawaiian islands provide unique conditions to directly measure fluvial thresholds and to quantitatively assess their role modulating climatic control of landscape evolution. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.