Additional External Researchers:
Tina van de Flierdt, Greg Downing (student), Allison Franzese (student)
The motivation of this funding is to better understand the mechanisms of rapid climate change. Two main projects are to understand what the sediment patterns in the tropics are trying to tell us about the processes in those regions (winds, currents, upwelling), and to examine the record of the penultimate glaciation for evidence of massive iceberg Armadas from the Hudson Strait. (1) The Eastern Equatorial Pacific is a highly dynamic region where both oceanographic and atmospheric systems interact. From the paleoclimatic perspective, it is a high priority to characterize the sensitivity of this region to rapid global climate change and to identify potential analogs to present variability patterns. In this context, marine sediments represent the key archive, which allow us to investigate the linkage between atmospheric and oceanographic systems in the course of a natural-driven rapid climatic change. This project uses multiple tracers in the equatorial Pacific, including constant flux proxies (230Th, 3He, and 10Be at some selected locations) with radiogenic isotopes (Sr, Nd) as proxies of provenance and faunal and geochemical measures of sea surface temperature. This project will not only provide the first map of the source regions of the detrital component across the entire equatorial Pacific but also - together with the information on the mass fluxes from extraterrestrial 3He - help to improve our understanding of the sedimentation patterns in the equatorial Pacific. Additionally, the project will yield important insights about variations in upwelling along the South American margin during times of climatic change. We are initiating a similar project in the equatorial Atlantic Ocean (overlapping with the Broecker et al. funding). (2) In the last glacial interval "Heinrich events" involve a series of sudden releases of massive amounts of ice from Hudson Strait into the North Atlantic, which result in a large influx of fresh water into the regions of North Atlantic Deep Water production. The effects on regional climate are clearly seen, and there appear to be correlative global climate changes as well. Although the Heinrich events in the last glacial have been studied intensively, much less is known about the older glaciations. Core V28-82 in the eastern North Atlantic is ideally located to characterize ice-rafting events in MIS 6. Counts of ice-rafted detritus grains reveal two major events, one at the termination of MIS 6 (H11). In addition to taking multiple approaches to study Stage 6 at high temporal resolution in V28-82 (including magnetic susceptibility, census of ice-rafted detritus, flux from 230Th-excess measurement, sea surface temperature from the abundance of the polar species, N. pachyderma (s.) surface salinity from 18O of N. pachyderma (s.)), a magnetic susceptibility survey of a suite of cores across the North Atlantic confirms that the results from V28-82 are representative of region. The initial results from MIS 6 appear to indicate that the penultimate glaciation behaved differently than the last glaciation with respect to large-scale, abrupt behavior of the Laurentide Ice Sheet. This difference likely has important implications relating to both the behavior of the ice sheets and to abrupt climate change.
Cross Cutting Themes:
Comer Science and Education Foundation