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The climate response of tropical Southeast Asia to abrupt climate change originating from high northern latitudes remains poorly understood. Here, marine sediments recovered from the Northwest Borneo Trough are analyzed to trace variations in terrigenous material composition associated with sea level and palaeoflood activities over the past 40 ka. We describe for the first time the influence of sea level change on terrigenous deposition from a tropical island with small mountainous rivers surrounded by narrow continental shelves and the coupling between North Atlantic dynamics and climate feedbacks in tropical Southeast Asia during the Dansgaard‐Oeschger stadials. This study demonstrates that climate oscillations occurring at high northern latitudes can be transmitted to tropical Southeast Asia through the functions of sea level, the East Asian winter monsoon and the Intertropical Convergence Zone. Such information is fundamental to correctly assessing future sea level rise and flood risks in tropical Southeast Asia. Plain Language Summary: Sea level rise and extreme climate events are two global climate issues currently faced by humanity under the background of global warming. However, the climate feedbacks in tropical Southeast Asia remain unknown, although portions of this region are now densely populated. Here, a gravity core retrieved from the Northwest (NW) Borneo Trough is employed to reveal variations in terrigenous material composition and their controlling factors over the past 40 ka. We found that the terrigenous sediments delivered to the NW Borneo Trough are primarily sourced from NW Borneo, and their deposition is mainly controlled by sea level change and flooding. Further in‐depth analysis reveals that northern high‐latitude cooling could cause floods in NW Borneo both in the modern and during the past by influencing the East Asian winter monsoon (EAWM) and/or the Intertropical Convergence Zone (ITCZ). Furthermore, our new records suggest that a stronger EAWM during cold stadials could have transported high levels of northerly moisture to NW Borneo, resulting in relatively higher speleothem δ18O values in NW Borneo. In short, abrupt climate changes in the high‐latitude Northern Hemisphere can be transmitted to tropical Southeast Asia through the functions of sea level, the EAWM and the ITCZ. Key Points: Sea level change and flooding are the main controlling factors for terrigenous deposition from tropical Southeast AsiaNorthern high‐latitude cooling could lead to the outbreak of floods in Northwest Borneo via atmospheric teleconnectionClimate oscillations occurring at high northern latitudes can be transmitted to tropical Southeast Asia [ABSTRACT FROM AUTHOR]

Recent research has suggested that East Asia has experienced a prevailing monsoon climate since the Eocene. However, there is little knowledge about the development of the East Asian monsoon system before the Miocene, particularly in southern China, due to a lack of well‐dated continuous sediment records. Here, we present new magnetic proxy records from International Ocean Discovery Program Site U1501 in the northern South China Sea. We conducted rock magnetic experiments, made scanning electron microscopy observations and performed diffuse reflectance spectrum analysis on the late Eocene‐early Oligocene core sediments. The magnetic signal of the sediments is dominated by detrital magnetite and titanomagnetite formed during the silicate weathering and erosion processes, which were used to infer the evolution of summer monsoon precipitation in southern China. Our results along with geochemical and clay mineral data from Site U1501 strongly indicate that the East Asian summer monsoon generally weakened across the Eocene‐Oligocene transition. This change was linked to coeval global cooling rather than tectonic processes. Prior to the Eocene‐Oligocene transition, the summer monsoon intensified, likely due to the latest Eocene warming event caused by the enhancement of the Atlantic Meridional Overturning Circulation, which may have preconditioned the Earth system for the greenhouse‐to‐icehouse transition. Plain Language Summary: To date, there is little knowledge regarding the long‐term evolution of monsoon climate in South China before the Miocene due to a lack of well‐dated continuous sediment records. The recent International Ocean Discovery Program Expedition 368 retrieved continuous late Eocene‐early Oligocene sediments at Site U1501 within the northern South China Sea, thus providing an opportunity to fill this gap. In this study, we investigate the evolution of the East Asian summer monsoon in South China during the late Eocene‐early Oligocene through a comprehensive analysis of the magnetic properties of the sediments. The results strongly indicate that the summer monsoon generally weakened across the Eocene‐Oligocene transition, which was linked to coeval global cooling. A short‐term strengthening of the summer monsoon prior to the Eocene‐Oligocene transition was also recorded. This change is attributed to the warming caused by the latest Eocene strengthening of the Atlantic Meridional Overturning Circulation, which may have preconditioned the Earth system state before causing a transition into an icehouse Earth. Key Points: The environmental magnetic record in the northern South China Sea indicates monsoon evolution during the late Eocene to early OligoceneThe East Asian summer monsoon weakened across the Eocene‐Oligocene transitionGlobal cooling drove the long‐term weakening of East Asian summer monsoon [ABSTRACT FROM AUTHOR]

Despite the importance of the westerlies to the global climate system, we still know little about their long‐term evolution and possible orographic controls during the late Cenozoic because of the lack of sedimentary records with precise chronological control. Eolian deposition in the North Pacific preserved past information about the westerlies, the major wind system delivering Asian dust to the Pacific. A continuous, high‐resolution eolian flux record since 23 Ma was reconstructed from sediments at Deep Sea Drilling Project Site 296 in the North Pacific. Combined with dust flux at Ocean Drilling Program Site 1208, variations in their difference indicated a northwards shift of the westerlies during 23‒9 Ma and a relatively stable state since then. We suggest that Tibetan uplift since the early Miocene began to drive the poleward shift of the westerlies until 9 Ma, after which the westerlies remained relatively stable over Asia on million‐year timescales. Plain Language Summary: The Northern Hemisphere Westerly wind is a significant component of planetary‐scale atmospheric circulation and has a large impact on regional and global climate change. Although numerous modern observations and orbital time‐scale studies of the Westerly wind have been conducted, we still know little about its evolution on million‐year time‐scales, which may modulate the overall amplitude of short‐term variations. Eolian deposition in the North Pacific has preserved precious information about the westerlies in the past. A continuous and high resolution eolian flux record dating from 23 Ma was reconstructed from sediments at Deep Sea Drilling Project Site 296 in the Northwest Pacific. Combined with dust records at Ocean Drilling Program Site 1208 to the east, we constrain how the path and strength of the Northern Hemisphere Westerlies have changed since the early Miocene. The two eolian records indicate a northwards shift of the westerlies between 23 and 9 Ma and a relatively stable state since then. We suggest that stepwise uplift of the Tibetan Plateau since at least the early Miocene began to drive the northwards shift of the Northern Hemisphere Westerlies until about 9 Ma, after which the westerlies remained relatively stable over Asia‐North Pacific on million‐year timescales. Key Points: We reconstruct the eolian flux record in the North Pacific since 23 Ma at high resolutionThe Northern Hemisphere Westerlies shifted northward between 23 and 9 Ma and have remained relatively stable since thenTibetan uplift drove the northward shift of Northern Hemisphere Westerlies in the early late Miocene [ABSTRACT FROM AUTHOR]

Oxygen content in the deep ocean plays a vital role in biogeochemical processes and has significant impacts on the global carbon cycle. The Japan Sea is a semiclosed basin with only shallow water connection to the Western North Pacific, and its redox history has been sensitively affected by tectonic and climatic changes in the past. Studies of paleo‐redox changes in the Japan Sea focused on the tectonic and orbital scales since the Pliocene remain scarce to date. Here, we present two high‐resolution paleo‐redox records during the last 4 Ma at IODP Sites U1425 and U1430 drilled in the Japan Sea. Our authigenic U (uranium) and U/Al records suggest remarkable changes of Japan Sea redox history from relatively oxic to periodic oxic‐anoxic conditions at ∼1.7 Ma. This was mainly caused by the restricted input of North Pacific oxygen‐rich water due to the uplift of northeastern Japan during late Pliocene and early Pleistocene, and opening of the Tsushima Strait and the periodic intrusion of Tsushima Warm Current following sea level change during glacial‐interglacial cycles since ∼1.7 Ma. Orbital changes of Japan Sea redox history suggest the existence of a long eccentricity cycle of 400 ka associated with East Asian summer monsoon rainfall evolution throughout the last 4 Ma. Changes of the amplitude of sea level and inflow of Tsushima Warm Current combined with the East Asian monsoon evolution produced eccentricity and obliquity cycles in Japan Sea redox environment after ∼1.7 Ma, as well as a transition from relatively oxic to anoxic conditions during glacials before and after Middle Pleistocene Transition. Plain Language Summary: Oxygen is a prerequisite for marine organisms' cellular respiration. Changes in the ocean oxygen levels can significantly impact the ocean ecosystem and even the global carbon cycle. During the geological time, shifts between ocean anoxia and oxygenation can be regulated by tectonic and climatic changes through water mass vertical mixing and current evolution. Here, we provided two paleo‐redox records during the last 4 Ma at IODP Sites U1425 and U1430 drilled in the Japan Sea. Remarkable changes from relatively oxic to periodic oxic‐anoxic conditions in the Japan Sea have been found at ∼1.7 Ma. This was mainly caused by the restricted input of the North Pacific oxygen‐rich water due to the uplift of the northeastern Japanese islands, and the opening of the Tsushima Strait in the southwestern Japanese islands and periodic intrusion of Tsushima Warm Current following sea level change, as well as East Asian monsoon evolution during glacial‐interglacial cycles since ∼1.7 Ma. Key Points: Paleo‐redox history in the Japan Sea during the last 4 Ma has been reconstructedTectonic activities of northeastern and southwestern Japan Sea controlled redox change at ∼1.7 MaSea level and East Asian monsoon changes regulated orbital paces of Japan Sea redox history since ∼1.7 Ma [ABSTRACT FROM AUTHOR]

Carbon release from the North Pacific in glacial‐interglacial cycles has been mainly linked to the North Pacific Intermediate Water (NPIW) formation and associated carbon/nutrient water upwelling and biological productivity changes. However, relationship between NPIW and atmospheric CO2 change in the early interglacial remains unclear. Here we report a high‐resolution sediment record of NPIW evolution based on paleo‐redox changes in the Western North Pacific during the last 400 ka. Our proxy and model results reveal a delayed collapse of NPIW after the glacial termination was coeval with decreased salinity of intermediate water and increased net rainfall in the North Pacific. Such weakened NPIW formation in the North Pacific probably make a contribution to maintain high atmospheric CO2 concentrations through weakened intermediate‐to‐deep ocean stratification and reduced subsurface biological pump net efficiency, countering the return to more stratified conditions in the Southern Ocean, which should drive down atmospheric CO2 during the early interglacial. Plain Language Summary: The high‐latitude North Pacific is an important region where ocean interacts with the atmospheric carbon cycle. CO2 outgassing from the interior ocean of North Pacific to the surface is mainly controlled by the upwelling as well as the biological productivity determined by the NPIW formation. Relationship between changes in the NPIW and atmospheric CO2 in the early interglacial remains unclear. Here we reconstructed the NPIW evolution during the last 400 ka, and combined with climate model results, we found a delayed collapse of NPIW compared with the Southern Ocean deglacial warming, which was synchronous with the decreased seawater salinity in response to increased net rainfall in the North Pacific. This NPIW collapse after glacial termination should weaken the intermediate‐to‐deep ocean stratification, and thus favored the upwelling of nutrient/carbon‐rich deep water to the surface. Besides, combined with the decreased nutrient‐poor subtropical waters supply from the weakened Pacific meridional overturning circulation, the biological pump net efficiency was reduced and thus consumed less CO2. These would counter the return to more stratified conditions in the Southern Ocean, which should drive down atmospheric CO2 during the early interglacial, and thus probably make a contribution to maintain high atmospheric CO2 concentration during the early interglacial. Key Points: NPIW evolution during the last 400 ka was reconstructed based on the paleo‐redox changes in the northern Okinawa TroughPrecessional changes of NPIW formation were mainly forced by the net rainfall in the North PacificDelayed collapse of NPIW probably contributed to maintain high atmospheric CO2 concentrations during the early interglacial [ABSTRACT FROM AUTHOR]

A multiproxy study including organic carbon and bulk nitrogen isotopes along with major and trace element concentrations in sediments from Integrated Ocean Drilling Program (IODP) Sites U1425 and U1430 in the Japan Sea have been conducted in order to trace deep‐water evolution in the Japan Sea and the North Pacific since the late Miocene. The high total organic carbon (TOC) flux, as well as other published geochemical and sedimentary evidence, indicates the occurrence of anoxic deep‐water in the Japan Sea before ∼7.4 Ma. The low‐nitrogen isotope values probably suggest nearly complete denitrification. In contrast, the sharply enhanced biological production but decreased burial of organic matter during ∼7.4–4 Ma, as shown by high enrichment factor of Ba (BaEF) values, together with low TOC flux, highlights enhanced deep‐water oxygenation in the Japan Sea during that time. We suggest that deep‐water formation in the North Pacific ventilated the deep Japan Sea via northern deep seaways before the sea became semi‐closed in the early Pliocene. The synchronously increased equator‐to‐pole temperature gradients driven by late Miocene global cooling may have caused southward shift of mid‐latitude storm tracks, coupled with the weakened East Asian summer monsoon and moisture transport, leading to decreased precipitation in mid‐latitude regions. The potential increases in surface salinity in the North Pacific may have broken the ocean stratification and favored deep‐water formation, and further caused deep‐water ventilation in the Japan Sea. Plain Language Summary: Deep‐water formation plays a significant role in deep ocean ventilation in the modern North Atlantic and South Ocean, while absent in the North Pacific. Whether deep‐water formation occurred in the North Pacific in the late Miocene global cooling remains unknown. The Japan Sea is an ideal place to test this phenomenon since it had deep‐water exchange with the North Pacific during the late Miocene‐early Pliocene. We analyze the organic carbon and bulk nitrogen isotopes and major and trace element concentrations of sediments since 11 Ma from IODP Sites U1425 and U1430 in the Japan Sea. During ∼7.4–4 Ma, the enhanced biological production along with decreased organic carbon burial indicates enhanced deep‐water oxygenation in the Japan Sea. We attribute this to potential deep‐water formation in the North Pacific, which was probably caused by weakened precipitation in mid‐latitude regions of the Northern Hemisphere and the resultant increased surface salinity in the North Pacific during the late Miocene cooling. Key Points: Paleoproductivity and paleoredox evolution in the Japan Sea since 11 Ma was reconstructedLow‐organic burial efficiency was caused by deep‐ocean oxygenation during ∼7.4–4 MaDeep‐water formed in the North Pacific ventilated the deep Japan Sea during the late Miocene‐early Pliocene [ABSTRACT FROM AUTHOR]

Shelf mud is an important sink for fluvial sediment, and it is sensitive to variations in river discharge and ocean circulation, which are significantly influenced by climate change. However, the evolution of shelf mud in response to climate change during the Holocene is poorly understood. Here, we present high‐resolution sedimentary records of heavy minerals and mass accumulation rates (MARs) from the East China Sea shelf to study the response mechanisms of the Holocene shelf mud supply, transport, and sedimentation to the climate‐driven variations in fluvial discharge and ocean currents. The results indicate that the shelf mud primarily originates from the Changjiang (Yangtze) River and has been mainly transported by wind‐driven longshore currents in suspension since approximately 8.0 ka. A comparison of the MARs with several shelf mud sedimentation‐rate records and climate changes during the Holocene on millennial timescales showed that strong (weak) precipitation in the river basin, which is positively linked with Asian summer monsoon and El Niño‐driven storms, could intensify (weaken) the fluvial sediment supply, thereby increasing (decreasing) the shelf mud deposition flux. On multicentennial timescales, changes in the relative intensities of different ocean currents due to climate oscillations during the Holocene could generate frequent migrations of the current shear front (a hydrodynamic barrier), which has trapped an abundance of suspended materials on the shoreward side and resulted in rapid mud sedimentation (~2.3 g/cm2/year) at different sites during different periods. Therefore, our study highlights that the Holocene shelf mud evolution responds sensitively to climate changes on different timescales. Key Points: The Changjiang River mud has been mainly carried southward by wind‐driven longshore currents since 8.0 kaHolocene shelf mud supply is modulated by precipitation from summer monsoons and El Niño‐related stormsHolocene rapid shelf mud sedimentation is directly linked with climate‐driven migrations of ocean currents [ABSTRACT FROM AUTHOR]

Quaternary East Asian winter monsoon (EAWM) evolution has long been attributed to high‐latitude Northern Hemisphere climate change. However, it cannot explain the distinct relationships of the EAWM in the northern and southern East Asian marginal sea in paleoclimatic records. Here we present an EAWM record of the northern East China Sea over the past 300 ka and a transient climate simulation with the Kiel Climate Model through the Holocene. Both proxy record and simulation suggest anticorrelated long‐term EAWM evolution between the northern East China Sea and the South China Sea. We suggest that this spatial discrepancy of EAWM can be interpreted as El Niño–Southern Oscillation (ENSO)‐like controlling, which generates cyclonic/anticyclonic wind anomalies in the northern/southern East Asian marginal sea. This research explains much of the controversy in nonorbital scale variability of Quaternary EAWM records in the East Asian marginal sea and supports a potent role of tropical forcing in East Asian winter climate change. Plain Language Summary: The modern East Asian winter monsoon (EAWM) is influenced by the combined effects of both the high‐latitude Northern Hemisphere (e.g., Siberian High) and the low‐latitude Western Pacific (e.g., El Niño–Southern Oscillation) and plays a major role in regulating atmospheric energy of East Asia and even the Northern Hemisphere. Its anomalies may cause extremely cold/warm winter weather or climate events, which result in profound societal and economic influences on the densely populated region of East Asia. Especially, some studies found the EAWM displays spatial discrepancies in northern and southern East Asia and can result in a colder/warmer north corresponding to a warmer/colder south. Our study shows anticorrelations of EAWM evolution between the northern East Asian marginal sea and the South China Sea since the late Quaternary. We suggest that such spatial discrepancies of EAWM evolution were controlled by El Niño–Southern Oscillation‐like processes in the tropical Pacific. During El Niño‐like conditions, the anomalous northwesterlies in the northern East Asian marginal sea led to a strengthened EAWM in this region. In contrast, anomalous southwesterlies in the South China Sea favored the occurrence of a weakened EAWM. The opposite situation occurred under La Niña‐like conditions. Key Points: Clay minerals in northern Okinawa Trough were derived from Yellow River and KyushuReversed EAWM evolution in the northern and southern East Asian marginal sea was revealedENSO‐like processes cause spatial discrepancy of Quaternary EAWM evolution [ABSTRACT FROM AUTHOR]

Abstract: El Niño/Southern Oscillation (ENSO) activity and the Pacific Walker Circulation are controlled by the zonal sea surface temperature (SST) gradient between the western and Eastern Equatorial Pacific (EEP) and the corresponding barometric difference. Variations in the zonal SST gradient since the early Pleistocene have primarily been triggered by changes in the SST in the Eastern Equatorial Pacific. However, the response of the ENSO‐like long‐term state to the cooling of the EEP and its coupling role with tropical Pacific climate changes are still not well established. Here we present a high‐resolution grain‐size record spanning the last 2.36 Myr, obtained from marine core sediment located in the West Philippine Sea in order to decipher the tropical pacific climate changes and reveal its controlling mechanism. By combining our data with other long‐term climatic records from the Equatorial Pacific, we demonstrate that the cooling of SST and enhanced upwelling in the EEP resulted in the development of the Walker Circulation and increased monsoon precipitation in Luzon from 2.2 to 1.6 Myr, from 1.2 to 0.8 Myr, and since 0.2 Myr ago. The progressive cooling of the high‐latitudes in the Quaternary may be responsible for our observation here. A newly identified 100 kyr dominant period between 2.2 and 1.6 Myr in the ENSO‐like modulated Pacific climate records indicates that the ENSO‐like system may play a key role in facilitating or responding to the global climate changes. [ABSTRACT FROM AUTHOR]

High-resolution multiproxy records, including clay minerals and Sr-Nd-Pb isotopes of the clay-sized silicate fraction of sediments from IODP Site U1429 in the northern Okinawa Trough, provide reliable evidence for distinct control mechanism on fine-grained sediments input from the Yellow River and the southern Japanese Islands to the northern Okinawa Trough since 34 ka BP. Provenance analysis indicates that the sediments were mainly derived from the Yellow River and the island of Kyushu. Since the last glacial, clay-sized sediments transported from the Yellow River to the study site were strongly influenced by sea-level fluctuation. During low sea-level stage (∼34-14 ka BP), the paleo-Yellow River mouth was positioned closer to the northern Okinawa Trough, favoring large fluvial discharge or even direct input of detrital sediments, which resulted about four times more flux of clay-sized sediments supply to the study area as during the relatively high sea-level stage (∼14-0 ka BP). The input of Kyushu-derived clay-sized sediments to the study site was mainly controlled by the Kuroshio Current and Tsushima Warm Current intensity, with increased input in phase with weakened Kuroshio Current/Tsushima Warm Current. Our study suggests that the Kuroshio Current was very likely flowed into the Okinawa Trough and thus influenced the fine-grained sediment transport in the area throughout the last glacial and deglacial. During ∼34-11 ka BP, the Kyushu clay-sized sediment input was mainly controlled by the Kuroshio Current. Since ∼11 ka BP, the occurrence of Tsushima Warm Current became important in influencing the Kyushu fine-grained sediment input to the northern Okinawa Trough. [ABSTRACT FROM AUTHOR]

The influence of hydrodynamics on the chemical composition of sediments is based on the uneven distribution of element abundances in different size fractions. In this study, 72 size-fractional sediments from the Huanghe (Yellow River) and Changjiang (Yangtze River) riverbeds were measured with XRD, SEM, ICP-AES and ICP-MS. The analysis results show that the mineral and chemical characteristics change with grain size in the Huanghe and Changjiang sediments. According to the principal components analysis, three independent geochemical factors were found. The first factor elements, Zr, Hf, Th, U, Y, La and TiO2 are influenced by the existence of heavy minerals. The second factor elements, Al2O3, alkalis, alkaline earth (excluding Ca and Sr) and most of the transitional metals are dominated by clay minerals. The third factor group includes Ca and Sr, which were controlled by calcium-bearing mineral contents and chemical weathering intensities. The various grain size distributions greatly affect the mineralogical and chemical compositions of bulk sediments. Compared to other size fractions, the 5-6PHI size fractions of the Huanghe and Changjiang sediments have special mineralogical and chemical compositions, and intermediate volume percentages. Weight or volume percentage of each size fraction may be more suitable than mean grain-size of the bulk sediment to elucidate the grain size effects. Chemical Index of Alteration (CIA) values increase steeply with decreasing grain size, while Weathering Index of Parker (WIP) values are relatively stable. Because of the big influence of the abundance of clay minerals on CIA values, it is questionable to use CIA as a proxy of weathering intensity. Considering the clay mineral effects, stability in values and heterogeneous material properties, WIP has the potential to indicate the chemical weathering intensity of sediments. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]