HR: 1330h
AN: PP42A-0862    [PDF]
TI: Rapid Oceanographic and Climatic Changes in the Okhotsk Sea During the Past 15,000 Years
AU: * Lembke-Jene, L
EM: llembke@geomar.de
AF: GEOMAR Research Center for Marine Geosciences, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Tiedemann, R
EM: rtiedemann@geomar.de
AF: GEOMAR Research Center for Marine Geosciences, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Nuernberg, D
EM: dnuernberg@geomar.de
AF: GEOMAR Research Center for Marine Geosciences, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Kozdon, R
EM: rkozdon@geomar.de
AF: GEOMAR Research Center for Marine Geosciences, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Nicole, B
EM: nbiebow@geomar.de
AF: Tethys Geoconsulting GmbH, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Roehl, U
EM: uroehl@rcom-bremen.de
AF: DFG Research Center Ocean Margins, PO box 330 440, Bremen, 28334 Germany
AU: Gorbarenko, S
EM: gorbarenko@poi.dvo.ru
AF: V.I. Il'ichev Pacific Oceanological Institute, 43 Baltiyskaya Street, Vladivostok, 690041 Russian Federation
AB: Our work focuses on sediment cores that disclose short-term climatic and oceanographic variability in the Okhotsk Sea. During summer, the region is dominated by the SE-Asia monsoon. It transports the vast majority of moisture via precipitation into the drainage basin of the Amur, the only large Siberian river not discharging into the Arctic Ocean and influences the amount of freshwater and sediment discharge into the Okhotsk Sea. The pattern is contrasted by cold, dry continental climate in wintertime, exerting influence on the lateral and temporal extent of the winter sea ice covering the Okhotsk Sea for nearly nine months per year. These two patterns show considerable variability in both strength and lateral extent on multifaceted timescales. Our cores were retrieved at the continental margins off Kamchatka and Sakhalin. The age models were derived from AMS radiocarbon datings, supported by the occurrence of a tephra layer. Maximum sedimentation rates exceed 120cm/kyr during the last 8000 years, decreasing to 20 cm/kyr in older parts of the cores. Accordingly, we achieve an average temporal resolution of 20-200 years between discrete samples, depending on the proxies we use. Content and accumulation rates of biogenic opal reveal information about short-term changes in primary productivity while minor element distributions derived from XRF core-scanning are taken as indicators for riverine sediment supply. Stable isotope data of benthic and planktic foraminifera supplement our results revealing information about the formation of Okhotsk Sea Intermediate Water, ventilating the mid-depth water masses of the NW-Pacific. Apart from displaying global events as the Terminations Ia and Ib or the Younger Dryas, our results provide evidence for the onset of of permafrost melting in the hinterland and possibly a destabilization of gas hydrates in the Sakhalin margin around 9,000 yr B.P. Besides, during Holocene, we observe high-frequency oscillations in both Amur river discharge and biogenic productivity that can be correlated to oxygen isotope records of the Greenland GISP2 ice core record. We compare these cyclic changes in sediment supply with the GISP2 record and low-latitude reference sites. Spectral analysis reveals several millennial-interdecadal periodicities, with a 940-year cycle in the early Holocene interval of 8500-4000 years BP. In the younger part from 0-4000 years BP, a transition towards a 1200-year cyclicity appears. The occurrence of these cyclic changes within the same frequency spectra in either record substantiate a tight connection between our study area and the climate in the North Atlantic region during the past ca. 8,000 years BP.
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
DE: 4870 Stable isotopes
DE: 9320 Asia
DE: 9355 Pacific Ocean
DE: 9604 Cenozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting