HR: 10:20h
AN: U42A-01 INVITED     [Abstracts]
TI: Multidecadal to Centennial-scale Climate Variability in the Holocene as Recorded in Northern Red Sea Sediments
AU: * Arz, H W
EM: harz@gfz-potsdam.de
AF: GeoForschungsZentrum-Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Lamy, F
EM: flamy@gfz-potsdam
AF: GeoForschungsZentrum-Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Paetzold, J
EM: juergen.paetzold@uni-bremen.de
AF: Research Center for Ocean Margins, Univ. Bremen, Klagenfurter Strasse, Bremen, 28359 Germany
AB: Proxy data for past surface ocean properties and continental rainfall based on two high resolution sediment cores from the northernmost part of the Gulf of Aqaba (core GeoB 5804-4) and the northern Red Sea (core GeoB 5836-2) were used to infer hydrological changes at the southern margin of the Mediterranean climate zone during the Holocene. Past hydrographic conditions were deduced from stable oxygen isotope measurements on tests of shallow dwelling planktic and benthic foraminifera. A second, independent data-set from GeoB 5804-4 is the terrigenous sand accumulation record as an indicator of changes in the eolian input from the surrounding desert areas. Several multicentennial-scale variations can be observed in both the marine and continental proxies. An overwhelming correspondence of our records with e.g. North Atlantic proxy record of changes in drift ice and 14C tree ring data suggest a broad teleconnective response to Holocene variations in solar output probably involving long-term changes in AO/NAO-like anomaly pattern throughout the Holocene. One very special paleoclimate archive in the northern Red Sea is the anoxic sediment from the brine-filled Shaban Deep. The Shaban Deep is a small-scale basin filled with oxygen-depleted, highly saline brine. Sediments retrieved from this basin are partly laminated and most probably document annual deposition cycles. The laminated interval between 6400 and 4200 years BP documents multidecadal to centennial variations in the carbonaceous (coccoliths) versus siliceous (diatoms) sedimentation and generally lines up with variations in solar activity. At 4.2 ka the lamination in the sediment disappears and the Shaban Deep turns into an oxygenated environment, suggesting the temporary absence of the brine. Stable oxygen isotopes of planktonic foraminifera show a sharp increase (less than 100 years) pointing to a strong positive sea surface salinity anomaly. This "evaporation event" probably enhanced deep-water formation and ventilation of the small basin. The timing and strengths of the environmental changes ~4.2 ka, suggests that this event is the regional expression of the major drought event at 4.2 ka BP, which is widely observed in the neighbouring regions, and that strongly affected Middle East agricultural civilisations.
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1050 Marine geochemistry (4835, 4850)
SC: Union [U]
MN: 2004 AGU Fall Meeting