CENTENNIAL-INTERDECADAL CLIMATIC CHANGES IN THE OKHOTSK SEA DURING HOLOCENE: RESULTS FROM POLLEN ANALYSIS AND GEOCHEMICAL PROXY RECORDS

Our recent work in the Sea of Okhotsk reveals records of millenial to interdecadal cyclic climatic changes in this subarctic NW-Pacific marginal sea and the adjacent Amur river drainage basin. The Amur watershed undergoes exteme seasonal as well as longer term climatic changes. Within this area the humid SE-Asia monsoon regime in summer is contrasted by cold, dry continental climate from NE-Siberia in wintertime. These two patterns show considerable variability in both strength and lateral extent on multifaceted timescales. Thus this region seems crucial for our comprehension of complex changes and shifts of atmospheric and oceanographic systems in the Far East and western North Pacific region. We recovered a suite of gravity cores from water depths between 650 m and 1000 m off the E Sakhalin continental margin. There, biosiliceous primary productivity and considerably high terrigenous sediment supply by the Amur river drainage system are main contributors to a depositional environment that leads to sedimentation rates between 30 and 120 cm/kyr. Our present age models consist of AMS radiocarbon control points from planktic foraminifera and benthic shell fragments as well as correlations of magnetic susceptibility values to existing reference records. Thus, to date, our investigations gain an average temporal resolution of 50-200 years between discrete samples for the Holocene. Based on a multiproxy approach, we use colour-scan values as well as content and accumulation rates of biogenic opal as a proxy for primary productivity while trace and minor and element distributions in the terrigenous fraction serve as indicator for riverine sediment supply. While these datasets provide high-resolution records, stable isotope data of benthic and planktic foraminifera supplement our results on a coarser temporal scale. Our results show high frequency oscillations in Amur river discharge and biogenic productivity that can be correlated to other regional records and also to oxygen isotope records of the Greenland GISP II ice core record. Beneath major deglaciation incidents like Younger Dryas or Terminations Ib and Ic, we also feel confident to recognize significant short-term events like the onset of the Preboreal, the Holocene climatic optimum and the subsequent Late Holocene Cooling with the Medieval Warm Period or the Little Ice Age.