HR: 1330h
AN: OS12A-0191    [PDF]
TI: Response of the Ganges dispersal system to climate change: a source-to-sink view since the last interstade
AU: * Goodbred, S L
EM: sgoodbred@notes.cc.sunysb.edu
AF: Stony Brook University, Marine Sciences Research Center, Stony Brook, NY 11794-5000 United States
AB: The forcing of sediment dispersal systems by climate is widely accepted, but our understanding of source-to-sink responses remains limited. Here, a comprehensive overview of climate impacts on the Ganges River dispersal-system is provided since the last interstade. Evidence from multiple source-to-sink components reveals major, coeval responses to variation in the South Asian monsoon. At $>$3000 km from its mountain headwaters to deep-sea fan, the Ganges dispersal system is immense and yet shows tight coupling between source area, catchment basin, and coastal and marine depocenters. Furthermore, sedimentary signals appear to propogate through the entire system at least as fast as our current chronological resolution of 1-2 kyr. This tight linkage of source-to-sink components is considered a function of the southwest (summer) monsoon's overwhelming control on regional hydrology. About 80% of the Ganges discharge and 95% of its sediment load are delivered to the margin during only four months, making the system extremely sensitive to this seasonal forcing. Also, the regional scale and distribution of the monsoon weather system means that changes in atmospheric circulation affect the entire drainage basin rather than local subcomponents. Finally, despite its present intensity, strength of the summer monsoon has varied significantly over the past 150 kyr under orbitally driven changes in insolation and global (glacial) boundary conditions. The resulting changes in precipitation, both well above and below modern values, have forced responses of glacier advance/retreat, riverine alluviation/incision, and varying sediment fluxes to the margin and deep-sea fan. Overall conclusions are that (1) this immense dispersal system responds to multimillennial-scale ($<$10$^{4}$ yr) climate change in a system-wide and largely contemporaneous manner and (2) that major sedimentary signals can be transferred rapidly from source to sink with little apparent attenuation. Furthermore, these acute responses to climate change have produced sedimentary/stratigraphic features that diverge from traditional sequence models in their nature and timing.
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1815 Erosion and sedimentation
DE: 3022 Marine sediments--processes and transport
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting