Climatic Changes in the Okhotsk Sea During the Past 60,000 Years - Teleconnections to Siberia, Southeast Asia, and Greenland?

Based on sedimentary records from the Okhotsk Sea, we reconstruct millennial to interdecadal-scale changes in terrigenous flux, sea-ice cover, and marine productivity over the past 60,000 years and relate these changes to the climatic evolution of the SE Asian monsoon, the high latitude Siberian Far East, and Greenland. Changes in the depositional environment of the Okhotsk Sea are recorded on stadial/interstadial timescales, though current age control does not yet allow to infer precise phase leads or lags from our time series. We use contents and accumulation rates of opal and chlorines as well as color scanning data as proxies for biogenic productivity while minor elemental compositions and amounts of terrigenous fraction serve as indicators for terrestrial sediment supply. Distinct increases in surface producitvity are observed during interstadial periods. Our results also show higher amounts of terrigenous matter during deglaciation and stadial phases. Analogous to today_s winter situation, general circulation models suggest a strengthened Siberian High and a pronounced Aleutian Low during colder times. In consequence, predominant northerly wind directions, reduced Amur River discharge, and lowered summer insolation favor the formation of sea ice and suppress biogenic productivity. Climatic amelioration during interstadials leads to a dynamic and mobile sea ice cover with northward propagating oscillating ice margins. Sea ice thawing and fluvial runoff promotes terrigeneous flux and nutrient supply, causes surface freshening, and the stabilization of the water column. Both, the high nutrient concentrations and water column stratification cause effective nutrient utilization, and favor marine productivity. Analogous to the today%s summer atmospheric circulation pattern of a pronounced Mongolian Heat Low and a strong Hawaian High, we assume that prevailing SE monsoonal winds during interstadial times, induce higher precipitation rates in the Amur drainage area, and hence, enhance the freshwater discharge to the Okhotsk Sea. Higher frequency oscillations in the terrigenous supply can be correlated to proxy series of the Greenland GISP II ice core record. Spectral and wavelet analysis performed on the Holocene elemental analysis time series reveal several centennial to multidecadal periodicities with a maximum power of a 940-year cycle in the interval between 8500 and 4000 years. In the youngest interval of 0 to 4000 years, though, a transition towards a 1200-year cyclicity appears, yet to be explained. On shorter time scales we observe significant cyclicities within the centennial and interdecadal range (e.g. at ca. 280, 86 or 60 years). As these periodicities are partly known from other low-latitudinal, monsoonal reference records, these findings further support the notion of a transmission of low latitude climate forcing to the Okhotsk Sea via the amount of freshwater, latent heat and sediment discharge by the Amur.