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The Bengal Fan, as the largest submarine fan in the world, receives a large amount of sediments discharged from the Himalayas through the Ganges-Brahmaputra (G-B) river system. However, previous studies of this system seldom focused on the role of channels, which are widely developed in the Bengal Fan, in sediment transportation over the last glacial cycle. Here, we discuss the coupled sedimentary archive in two gravity cores along the Active Channel in the Bengal Fan. Our findings are based on grain size, clay minerals, and Sr and Nd isotope compositions of these two sediment cores. End-member modeling of grain-size data reveals that the intermediate end-member represents the flux of distal fluvial particles from the G-B river system, the fine end-member denotes regional sediment supply of weathered volcanic materials, especially from the eastern Indian Peninsula, and the coarse end-member probably reflects nearby terrigenous input, aeolian input and/or volcanic glass. Sediment provenance analysis based on clay minerals, and Sr and Nd isotopes confirmed sediment supply from the G-B river system which was characterized by high illite percentage, high 87Sr/86Sr ratios and low eNd values, especially during five stages (50–45 ka, 42–37 ka, 31–28.5 ka, 24–20 ka and 14–9 ka). During these stages, heavy fine-grained sediment supply from the G-B river system was discharged into the study area under the influence of climate change rather than sea-level fluctuation, additionally emphasizing the importance of channels in the sediment transport process. Moreover, we find a significant alteration of sediment sources at ∼26 ka, which may be related to conversion of the deep-water currents in the Bay of Bengal.

The South China Sea (SCS) is connected to the West Pacific through a deep channel in the Luzon Strait. Thus the SCS deep water is sensitive to the evolution of Pacific Ocean circulation, which significantly influences the global climate system. Geochemical data (Pb isotope and redox-sensitive elements data) and magnetic data were determined for a Fe–Mn nodule obtained from Jiaolong seamount in the central SCS. These records reflect interactions between changes in ice sheets, deep Pacific circulation, and weathering inputs to the deep SCS during the Pliocene and Quaternary. Our results show that the SCS deep-water environment can be divided into three major Stages (Stages 1–3). Stage 1 (∼4.8–1.4 Ma) was characterized by a well-oxygenated Pacific Deep Water (PDW) and lower dust inputs; then moderate stable deep-water ventilation and greater inputs of Asian dust occurred during Stage 2 (1.4–0.9 Ma). During Stage 3 (

As an integral part of the Earth's climate system, the Kuroshio Current (KC) plays a crucial role in shaping the regional oceanography and climate in the Northern Hemisphere. However, how the KC dynamics have varied over glacial-interglacial cycles is still under debate. The dynamic transfer and accumulation of submarine hydrothermal source materials by deep-reaching KC offer us a unique opportunity to examine the variations in dynamics of the KC. Here, we used novel proxies of sedimentary mercury (Hg) and antimony (Sb) in core MD01-2404 retrieved from the middle Okinawa Trough (OT) to reconstruct the evolution of the KC hydrodynamics over the last 92,000 years. We infer the enrichments of sedimentary Hg and Sb to signify hydrothermal input, which is delivered laterally to the study site by deep circulation in association with the KC, thus indicating the dynamics of KC. Overall, both the sedimentary Hg and Sb in core MD01-2404 indicate a persistent influence on the KC dynamics within the OT over the last glacial-interglacial cycles. Furthermore, our Hg and Sb proxies suggest a significantly weakened influence during the last deglaciation and last glacial period while a strengthened influence during the Holocene and late Marine Isotope Stage 5. Our studies imply that the orbital-scale dynamics of KC are controlled by tropical atmosphere-ocean interactions induced by sea surface temperature changes and regulated by the extratropical climate conditions.

The Quaternary East Asian summer rainfall evolution reconstructed with the Chinese speleothem δ18O records shows the consistency throughout the region of East Asia, and has long been considered equivalent to the monsoon intensity. Its variation and teleconnection with global climate were usually interpreted by the meridional shift of the intertropical convergence zone (ITCZ). However, many other proxy records, climate simulations and meteorological observations suggest the inconsistent rainfall patterns in the different regions of East Asia on multi-timescales. Such spatial heterogeneity in Quaternary East Asian summer rainfall indicates that the hydroclimate in this region is not fully paced by the migration of the ITCZ. Here, we report a sediment record of rainfall evolution during the last 400 ka in the northern East China Sea, and this record, in combination with a transient climate model simulation, indicates an out-of-phase relationship between rainfall over middle-southeastern East Asia and northern and southwestern East Asia on the precession band, with high boreal summer insolation corresponding to the increased rainfall intensity in the northern and southwestern East Asia, however, decreased rainfall intensity in the middle East Asia. We attribute this regional heterogeneity in East Asian rainfall to the reorganization of the Hadley circulation, including shifts in the ascending branch (ITCZ) and descending branch (subtropical westerly jet), in response to changes in the hemispheric meridional temperature gradient. Our results highlight the crucial role of the Hadley circulation in the East Asian hydroclimate and have important implications for future climate projections.

To test the biological effectiveness of iron fertilization by Asian aeolian dust and volcanic ash in the stratified high-nitrate, low-chlorophyll subarctic Pacific Ocean over long-time scales, we analysed sediments with ages between 2.8 and 0.9 Ma at ODP Site 885/886. This site lies far from the influence of other iron sources (e.g. icebergs or lateral iron transportation) and the water column has been stratified since intensification of northern hemisphere glaciation (iNHG) at ∼2.7 Ma, which limits nutrient upwelling and makes it an ideal location for testing iron bioavailability of different atmospheric sources that fell onto the surface ocean. We investigate diatom assemblages and opal export changes, and compare them with the properties of iron minerals in Asian aeolian dust and volcanic ash. Our results reveal that Asian aeolian dust contains mostly unreactive iron-bearing minerals that supplied limited bioavailable iron for diatom growth at Site 885/886. Diatom productivity changes were dominated by upwelling/stratification changes over long timescales, and by sporadic iron fertilization from volcanic ash inputs. Iron from volcanic ash particles is likely to have become bioavailable because such particles dissolved more readily due to their high porosity and ultra-fine size.

The alkenone unsaturation index ( U 37 k ′ ) as proxy for sea surface temperature (SST) is an important tool in paleoclimatology for reconstructing past ocean temperature variability. Typically, U 37 k ′ recorded in marine surface sediments shows a linear correlation with modern mean annual SST. However, in high-latitude oceanic regions, such as the subpolar Pacific, U 37 k ′ -based SSTs do overestimate the mean annual temperature by up to 6 °C, potentially leading to obscured paleoclimatic information drawn from stratigraphic U 37 k ′ -records. The reason for this “warm bias” is still not well understood. Here, we present a compilation of 97 sediment surface samples from Multicores collected in the Bering Sea, the Okhotsk Sea and the North Pacific to evaluate the alkenone-temperature proxy against observational data from the North Pacific. Sediment surface samples were analysed for alkenones and the derived U 37 k ′ -indices converted to water temperatures using different calibration equations established in the literature. U 37 k ′ -based SSTs were then compared to instrumental SST data, as well as modern alkenone flux data from sediment traps in the North Pacific. Our results confirm that most U 37 k ′ -based SSTs from the subpolar Pacific are 2–6 °C too warm compared to instrumental mean annual SSTs for calibrations applied. However, with an uncertainty at the level of ±1.5 °C or less reconstructed SSTs fit quite well to modern autumn temperatures north of the Subarctic Front (SAF), when maximum export flux of alkenones to the seafloor is indicated by sediment trap data. South of the SAF, reconstructed SSTs largely mimic the modern mean annual SST signal with an uncertainty of ±1.5 °C or less, which is likely due to the attenuation of seasonality and longer growth season of coccolithophorids according to sediment trap data. Our study further demonstrates that U 37 k ′ , when seasonality in alkenone production and export are known and considered, is able to provide reasonable estimates of SSTs in modern high-latitude ocean settings. We conduct a case study using available alkenone time-series derived from a sediment core collected from the south-western Okhotsk Sea to better understand the potential effect of seasonality in alkenone production on stratigraphic U 37 k ′ -record in the subpolar Pacific. The case study from the Okhotsk Sea indicates that even a small shift in seasonality may lead to strongly biased SSTs with broader regional implications for paleoclimate reconstructions in high-latitude ocean settings.

Glacial-interglacial sea level changes have caused drastic variations in the surface hydrography, ventilation and ecosystem structure in the Japan Sea. Previous reconstructions using microfossils and geochemical proxies suggested decreased productivity and a more calcareous plankton community during glacial periods. However, the inferred community structure change is not consistent with significantly lower salinity in the Japan Sea during the glacials, which would have had a deleterious effect on calcareous plankton growth. Here, biomarker records of ODP Site 797 are generated to further evaluate phytoplankton productivity and community structure changes in the Japan Sea over the last 166 kyr. Although the contents of the phytoplankton biomarkers changed by two to three orders of magnitude, there were no clear glacial-interglacial patterns as sediment biomarker contents reflected the combined effect of production and water column degradation. The collective assessments of our biomarker records and published records support previous conclusions of decreased productivity in the Japan Sea during the glacials. However, a community structure proxy based on the alkenone/brassicasterol ratio reveals a shift from a diatom-dominated community during the glacials to a coccolithophorid-dominated community during the interglacials, mainly as a result of surface salinity variations in the Japan Sea controlled by sea-level changes. Previous community structure reconstruction using biogenic carbonate/silica ratio could have been complicated by the different environmental factors governing silica and CaCO 3 dissolution in the Japan Sea.