HR: 15:10h
AN: NG43A-07    [Abstracts]
TI: Dynamics of a Barchan Dune Field: a Discrete Numerical Model
AU: * Littlewood, R C
EM: ryan.littlewood@duke.edu
AF: Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Sciences; Center for Nonlinear and Complex Systems, Duke University, Durham, NC, USA, Old Chemistry Building Box 90227 Duke University, Durham, NC 27708, United States
AU: Murray, A B
EM: abmurray@duke.edu
AF: Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Sciences; Center for Nonlinear and Complex Systems, Duke University, Durham, NC, USA, Old Chemistry Building Box 90227 Duke University, Durham, NC 27708, United States
AU: Andreotti, B
EM: andreotti@pmmh.espci.fr
AF: Laboratoire des Physique et Mecanique des Milieux Heterogenes, ESPCI, 10 rue Vauquelin, Paris, 75231, France
AU: Claudin, P
EM: claudin@ccr.jussieu.fr
AF: Laboratoire des Physique et Mecanique des Milieux Heterogenes, ESPCI, 10 rue Vauquelin, Paris, 75231, France
AB: Barchans are crescent-shaped dunes that form on solid ground in areas with a relatively low sand supply and a unidirectional wind regime. Isolated barchans have been successfully modeled with regard to their shape and propagation velocity. However, emergent effects that arise for the case of a field of dunes have proven difficult to capture. These behaviors include selection of a preferred size and spacing within a patch of dunes and additionally the presence within a dune field of multiple patches, greatly extended in the downwind direction, each exhibiting a different dominant size. It is suspected that these sorting inhomogeneities in the dune field are self- organized and not the result of external forcing. Here, we present the results of modeling efforts using a discrete numerical model representing a field of barchan dunes. We use simplified equations for dune shape, mass balance, and propagation. Dunes interact by merging and by means of the downwind sand flux. Additionally, we include a simplified treatment of dune calving. Tentative conclusions can be drawn from the rich behavior of the model. In it, spatial inhomogeneities can arise due to feedbacks triggered by stochastic fluctuations about critical values of the input parameters. Isolated groups propagate at velocities independent of those of their constituent dunes. Size selection occurs to a limited extent due to the onset of calving at a critical size. In sum, the model displays some of the emergent dune field characteristics that have not previously been replicated.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 4430 Complex systems
DE: 4435 Emergent phenomena
DE: 4460 Pattern formation
DE: 4485 Self-organization
SC: Nonlinear Geophysics [NG]
MN: 2007 Fall Meeting