HR: 0800h
AN: PP21A-1371    [Abstracts]
TI: A Continental Shelf Sediment Transport Proxy Record of Decadal Atmospheric and Oceanographic Variability in Southern Alaska
AU: * Vienne, W F
EM: wvienn1@ufl.edu
AF: Department of Geological Sciences, University of Florida, P.O. Box 112120, Gainesville, FL 32611-2120 United States
AU: Jaeger, J
EM: jaeger@geology.ufl.edu
AF: Department of Geological Sciences, University of Florida, P.O. Box 112120, Gainesville, FL 32611-2120 United States
AB: The Gulf of Alaska (GOA) margin is a prime location to study and quantitatively model glacial climate and continental margin sedimentation. Coupled oceanographic and atmospheric processes control sediment transport and sedimentation patterns on the GOA continental shelf, and consequently contain a proxy record for regional climate variability. However, the specifics of this coupled relationship between climate and sediment transport have not been studied. In collaboration with the GOA-NEP GLOBEC program, gravity cores were taken at three sites of high sedimentation rates along the GOA margin in 2001 and 2003 representing proximal and distal shelf depocenters. Chronologies were established using Pb-210 and Cs-137 and sedimentation rates vary from 0.3 to 3 cm/yr, providing near-annual to decadal-scale resolution. High-spatial resolution grain-size analyses and multi-sensor core logging of bulk density and magnetic susceptibility were measured to recognize relationships between these three proxies of sediment transport in each core and between sites. The time series of these properties have been compared to oceanographic and atmospheric instrumental records--generally beginning in the early to middle 20th century--such as sea level pressure, temperature, significant wave height, and wind speed. The three measured properties positively correlate within each core and between each core, indicating that these are likely controlled by similar sediment transport processes, such as wave resuspension and bottom-current transport, at all three sites. Strong correlation on a decadal scale was found between the physical properties of the cores and the instrumental records of temperature and significant wave height, as well as variability in regional precipitation. Also, there is a marked increase in bulk density, magnetic susceptibility, and grain size values from the late 1970's onward, which corresponds to the timing of a shift from a negative to a positive regime in the Pacific Decadal Oscillation. These results suggest that temporal variability in grain size, bulk density, and magnetic susceptibility on Alaska's continental shelf are, in part, controlled by changes in wind speed, wind direction, and wave height.
DE: 4808 Chemical tracers
DE: 4863 Sedimentation
DE: 4267 Paleoceanography
DE: 3022 Marine sediments--processes and transport
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting