HR: 1340h
AN: PP13C-1417    [Abstracts]
TI: Rapid Climatic and Oceanographic Changes in the Okhotsk Sea during the Holocene
AU: * Lembke-Jene, L
EM: Lester.Lembke-Jene@awi.de
AF: Alfred-Wegener-Institute for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven, 27568, Germany
AU: Tiedemann, R
EM: Ralf.Tiedemann@awi.de
AF: Alfred-Wegener-Institute for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven, 27568, Germany
AU: Nuernberg, D
EM: dnuernberg@ifm-geomar.de
AF: IFM-GEOMAR Leibniz-Institute for Marine Sciences, Am Seefischmarkt 1-3, Kiel, 24148, Germany
AB: We report on records of centennial- to millennial-scale climatic changes in the Okhotsk Sea and the adjacent continental Amur river watershed, thereby confirming the significant potential of this realm for paleoclimatic reconstructions. High biogenic productivity, delivery of Ice-Rafted Debris (IRD), highly variable hydrographic conditions, and terrigenous sediment supply by the Amur�s drainage system closely interact in this region and form the depositional environment. According to our stratigraphic framework, average sedimentation rates in the hemipelagic sediment cores vary between 30 and 160 cm/kyr. Thus, our study provides insight into rapid climatic changes on millenial and shorter timescales for the last deglaciation and the Holocene. Biogenic opal and chlorines serve as biogenic productivity proxies, elemental compositions derived from XRF-scanning as indicators for riverine sediment supply and sea- ice action. Whereas these datasets provide high-resolution records, stable isotope data of benthic and planktic foraminifera as well as countings of terrestrial pollen and IRD data supplement our results on lower temporal scales. The last deglaciation is characterized by repeated pronounced maxima in IRD and according elemental concentrations, pointing to a high supply of terrigenous siliciclastics. During the Holocene, high-frequency oscillations in Amur river discharge can be correlated to the oxygen isotope record of the Greenland NGRIP ice core. We observe significant cyclicities within the millennial and centennial range with a mid-Holocene shift in the significant frequencies. As these periodicities are partly known from other low-latitudinal, monsoonal reference records, these findings may support the notion of a transmission of low latitude climate forcing to the higher latitudes, possibly via freshwater discharge and latent heat transport by the Amur. From ca. 6.5 kyr BP onwards, we recognize a Holocene climatic optimum in various proxy records, whereas starting at about 4 kyr BP slightly deteriorating colder climatic conditions prevail. Planktic and benthic foraminiferal stable isotope data from the Sakhalin margin suggest high hydrographic variability in discharged freshwater. This in turn influences the stratification of regional surface water masses and the average thermocline depth, as well as the formation of intermediate waters that precondition the ventilation and hydrographic properties of the subarctic North Pacific.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4924 Geochemical tracers
DE: 9320 Asia
DE: 9355 Pacific Ocean
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting