HR: 0830h
AN: H51D-1108    [PDF]
TI: Climate Change Imprint in Spatial Patterns of Dune Fields
AU: * Werner, B
EM: bwerner@ucsd.edu
AF: Complex Systems Laboratory, Cecil and Ida Green Institute of Geophysics and Planetary Physics, University of California-San Diego, La Jolla, CA 92093-0225
AU: Kocurek, G
EM: garyk@mail.utexas.edu
AF: Department of Geology and Geophysics, University of Texas, Austin, TX 78712
AB: Although many techniques for probing the history of a dune field, such as statigraphic reconstruction and dating, are available, the information contained within the spatial pattern of dunes rarely has been utilized. Here we present a model study aimed at identifying characteristic signals of climate change in the spatially varying properties of a dune field. In the model, a dune field is characterized by spacing, orientation and density of defects (ends of crestlines), properties that vary continuously in both space and time. The model is forced with transport direction and magnitude that change with time. Defects migrate through the dune field at a speed greater than dunes. As a defect passes through a dune crestline, crest length decreases because of merger, resulting in an increase in spacing. Defect density decreases as oppositely facing defects annihilate. Orientation changes when oppositely facing defects migrate at different speeds. Defect density increases and spacing decreases on boundaries when sand is supplied from upwind, resulting in the creation of numerous small dunes. Spacing, defect density and orientation both advect and diffuse. The resulting set of coupled nonlinear partial differential equations is solved using a finite difference technique. Climate changes result in changes in properties of dune fields at the boundaries; these changes then propagate into the dune field and dissipate. For example, dune constructional episodes cause the development of a shock wave in defect density, originating at the upwind end of the field, that results in a permanent increase in spacing. The prospects for determining the occurrence and characteristics of past climate change from snapshots of modern dune fields will be assessed. Supported by National Science Foundation, Geology and Paleontology Program.
DE: 1824 Geomorphology (1625)
DE: 3220 Nonlinear dynamics
SC: Hydrology [H]
MN: 2003 Fall Meeting