40 Aeolian Systems in Time and Space

This session explores research focused on all aspects of aeolian processes and landforms, including dunes, dust, and loess in modern and ancient aeolian systems on Earth and other planets.

Sunday, 19 October 2025
1:30 PM - 5:30 PM
HBGCC, 212AB

A tale of two states: Climate and river dynamics influence aeolian state transitions and morphodynamics in bistable dunefields

Paper number: 40-1
Program: Technical Sessions
Time: 1:35 PM – 1:50 PM

Authors

  • Joshua Caster Presenting Author
    US Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, AZ
  • Joel Sankey
    US Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, AZ
  • Temuulen Sankey
    Northern Arizona University, School of Informatics, Computing, and Cyber Systems, Flastaff, AZ
  • Taylor Joyal
    Northern Arizona University, School of Earth and Sustainability, Flagstaff, AZ
  • Matthew Bowker
    Northern Arizona University, School of Forestry, Flagstaff, AZ

Abstract

Alternative stable state theory describes how systems can occur and transition between states, under similar environmental conditions, such as the co-occurrence of bare and vegetated dunes within a single climate regime. Theory posits that transitions between states occur when perturbed by changes in climate, ecologic drivers, and disturbance. Here we examine the roles of disturbance to river flow regime and sediment supply changes as geomorphic drivers of state transitions in bistable aeolian dunefields. We specifically study 24 fluvially-sourced aeolian dunefields distributed over two desert climate regimes with potential for aeolian bistability along 400 km of the Colorado River in Grand Canyon National Park, USA. We analyze dunefield morphodynamics from four decades of topographic change detection data following alteration of flood dynamics and sediment availability by upstream dam emplacement and operations to test the importance of fluvial-aeolian interactions on state transitions. Across the study area, we observed both active states, identified by dunes with indicators of aeolian sediment transport, and inactive states that lack indicators of aeolian sediment transport primarily owing to biological cover. We find that the transition from active states to inactive states occurs with the reduction of flood magnitudes and fluvially-sourced aeolian sediment supplies. This finding is especially pronounced within the hotter desert climate regime, where winter precipitation is greater, supporting more extensive biological soil crust and invasive grass cover. Dunefield morphodynamic analyses show that the active to inactive state transition coincides with reductions in dune movement but not necessarily lower rates of erosion. Counter-to-expectations, the relative amount of positive and negative sediment volume changes – or sediment imbalance – in the dunefields were more erosional, even with greater vegetation cover and less aeolian sediment transport. This result highlights the importance of interconnections between non-aeolian processes during and following aeolian state transitions.  While alternative states are usually stable and long-lasting, here we show that changes in fluvial and aeolian sediment supply can drive state transitions that are enhanced by climate and ecological feedbacks. As fluvial-aeolian interactions are ubiquitous throughout Earth’s past and present, we anticipate that these findings are important for understanding landscape evolution and are relevant for supporting management of these sensitive systems.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413460

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