Beschreibung: Paleoceanographic evidence commonly indicates that Last Glacial Maximum surface temperatures in the Japan Sea were comparable to modern conditions, in striking difference to colder neighboring regions. Here, based on a core from the central Japan Sea, our results show similar UK′37- and TEXL86-derived temperatures between 24.7-16.3 ka BP, followed by an abrupt divergence at ~16.3 ka BP and a weakening of divergence after ~ 8.7 ka BP. We attribute this process to a highly stratified glacial upper ocean controlled by the East Asian Summer Monsoon, increasing thermal gradient between surface and subsurface layers during the deglaciation and the intrusion of Tsushima Warm Current since the mid Holocene, respectively. Therefore, we suggest threshold-like changes in upper-ocean temperatures linked to sea-level rise and monsoon dynamics, rather than just sea surface temperatures, play a critical role in shaping the thermal and ventilation history of this NW Pacific marginal sea.

Beschreibung: Collection of Alkenone temperatures derived from 42 Multicorer sediment surface samples of the subpolar North Pacific and its marginal seas (Okhotsk Sea and Bering Sea). Multicores were collected during several expeditions to the Okhotsk Sea, Bering Sea and North Pacific from 1997 to 2013 (R/V Akademik M.A. Lavrentyev cruise LV27 (Nürnberg et al., 1997); R/V Akademik M.A. Lavrentyev cruise LV28 (Biebow and Hütten, 1999); R/V Marshal Gelovany cruise GE99 (Biebow et al., 2000); R/V Akademik M.A. Lavrentyev cruise LV29 (Biebow et al., 2003); R/V Sonne cruise SO178, (Dullo and Biebow, 2004); R/V Sonne cruise SO201-2, Dullo et al., 2009); R/V Akademik M.A. Lavrentyev cruise LV55 (Gorbarenko, 2012); R/V Akademik M.A. Lavrentyev cruise LV63 (Gorbarenko, 2014).

Beschreibung: Investigating the composition and distribution of pelagic marine sediments is fundamental in the field of marine sedimentology. The spatial distributions of surface sediment are unclear due to limited investigation along the Emperor Seamount Chain of the North Pacific. In this study, a suite of sedimentological and geochemical proxies were analyzed, including the sediment grain size, organic carbon, CaCO3, major and rare earth elements of 50 surface sediment samples from the Emperor Seamount Chain, spanning from ∼33°N to ∼52°N. On the basis of sedimentary components, we divide them into three Zones (I, II, and III) spatially with distinct features. Sediments in Zone I (∼33°N–44°N) and Zone III (49.8°N–53°N) are dominated by clayey silt, and mainly consist of sand and silty sand in Zone II. The mean grain size of the sortable silt shows that the hydrodynamic condition in the study area is significantly stronger than that of the abyssal plain, especially at the water depth of 1,000–2,500 m. The CaCO3 contents in sediments above 4,000 m range from 20 to 84% but decrease sharply to less than 1.5% below 4,000 m, confirming that the water depth of 4,000 m is the carbonate compensation depth of the study area. Strong positive correlations between Al2O3 and Fe2O3, TiO2, MgO, and K2O (R 〉 0.9) in the bulk sediments indicate pronounced contributions of terrigenous materials from surrounding continent mass to the study area. Furthermore, the eolian dust makes contributions to the composition of bulk sediments as confirmed by rare earth elements. There is no significant correlation between grain size and major and minor elements, which indicates that the sedimentary grain size does not exert important effects on terrigenous components. There is significant negative δCe and positive δEu anomalies at all stations. The negative Ce anomaly mainly exists in carbonate-rich sediments, inheriting the signal of seawater. The positive Eu anomaly indicates widespread volcanism contributions to the study area from active volcanic islands arcs around the North Pacific. The relative contributions of terrestrial, volcanic, and biogenic materials vary with latitude and water depth in the study area.