Winter Monsoon Research Articles

Biochemical and physiological effects of propagule type and auxin concentration on adventitious root formation in novel Jasmine genotypes

Jasmine is primarily propagated through asexual methods, and bio-stimulants can improve soil fertility around plant roots. Some jasmine genotypes are mainly propagated through cuttings; however, the rooting process is slow and inconsistent. Specific jasmine genotypes are primarily propagated through cuttings, but the rooting process is slow and uneven. This study evaluated the regeneration potential of stem cuttings by investigating the effects of auxins and various propagule types on adventitious root formation, along with associated biochemical changes. A field experiment conducted by the Department of Floriculture and Landscaping at TNAU, Coimbatore, Tamil Nadu, from December 2023 to June 2024, during the winter monsoon, investigated the rooting of stem cuttings in three Jasminum genotypes using auxin. Stem cuttings of J. sambac Double Flower type (DF), J. grandiflorum White Flower type (WF) and a new cultivar of J. multiflorum CO.1 Winter Jasmine (CO.1 WJ) were treated with three Indole-3-Butyric Acid (IBA) concentrations (0.5, 1, 1.5 g L-1) and distilled water as control. Utilizing a Factorial, Completely Randomized Design for terminal and semi-hardwood cuttings, the study found that rooting hormone significantly enhanced root formation and stem and shoot growth. Semi-hardwood cuttings of J. sambac (DF) treated with 1g L-1 IBA had the highest rooting rate (88.60%), number of roots (9.34), root length (12.74 cm), shoot length (10.26 cm) and number of leaves (6.60). The highest rooting rate of 48.15% was obtained from the terminal cuttings of J. grandiflorum (WF) that had been treated with 1g L-1 IBA, in addition to other parameters such as number of roots (13.52), root length (12.03 cm), shoot length (14.30 cm), and number of leaves (13.48). On the other hand, J. multiflorum (CO.1 WJ) recorded the highest rooting rate of 72.23%, root number of 16.52, root length of 17.22 cm, shoot length of 14.14 cm and number of leaves, which was pegged at 31.70 when terminal cuttings were treated with 1g L-1 IBA. The current findings indicate that the application of auxins is crucial for promoting early root initiation and achieving higher rooting success, making it advantageous for vegetative propagation.

A Regional Paleoclimate Record of the Tropical Aeolian Sands during the Last Deglaciation in Hainan, China

The KLD segment of the Kenweiyuan section in Wenchang, Hainan, China is a set of aeolian sand deposits of the Last Deglaciation. The chemical element and heavy mineral analysis performed in this study reveals the chemical index of alteration (CIA) in the segment to be as high as 93–95, with all the heavy minerals identified as stable and extremely stable making up 38–45% of the total. Furthermore, the zircon, tourmaline, and rutile content (ZTR index) of the segment is determined to range between 48–71. The (Al2O3 + TOFE)/SiO2 ratios display obvious fluctuations from old to new strata in the segment, with the low values corresponding to Heinrich event (H1), Dansgaard-Oeschager (D-O), and Younger Dryas (YD) and the high values corresponding to Bølling and Allerød. Our study suggests that these fluctuations are attributed to the alternation of the East Asian winter and summer monsoons. Hainan Island is also impacted by the surface ocean climate of the South China Sea, and characteristics of the KLD segment may be connected to the climate changes in the North Atlantic related to the winter monsoon season or westerlies. Furthermore, the segment presents a clear response to millennium-scale climate changes during the Last Deglaciation on Hainan Island. Based on the high CIA values in the KLD segment, and particularly due to the observed stable detrital minerals, the ratios can be linked to the overall tropical climate, indicating a relatively warm tropical climate environment in the Last Deglaciation in Hainan. The high CIA values also reveal the cause of aeolian sand formation under the tropical environmental conditions in the low latitude region of China in the Late Quaternary.

Seasonal Dynamics of Trichodesmium and Phytoplankton Communities in the Eastern Arabian Sea: Winter Vs Spring-inter monsoon

The filamentous marine cyanobacterium Trichodesmium forms extensive blooms in tropical seas, where it plays an important role in nitrogen fixation. This study investigated Trichodesmium-associated phytoplankton in the Eastern Arabian Sea (EAS) during bloom and nonbloom conditions. Trichodesmium blooms over the continental shelf primarily comprised of T. erythraeum and T. thiebautii during the Spring Inter Monsoon (SIM) and T. erythraeum during the Winter Monsoon (WM). T. erythreaum blooms have rarely been reported from the north-east Arabian Sea during WM. Trichomes comprised of 143-1552 cells during the WM, with filaments ranging from 1339 to 13163 µm in length. Non-diazotrophic groups like diatoms and dinoflagellates were associated with Trichodesmium during both seasons within the bloom waters. The study found a novel symbiotic relationship between the heterocystous diazotroph Richelia intracellularis and Nitzschia sicula during WM blooms. This research expands knowledge of lesser-known phytoplankton species and their associations in the EAS.

Chlorophyll-a and suspended matter variability in a data-scarce coastal-estuarine ecosystem

Analyzing the variability of chlorophyll-a (Chl-a) and total suspended matter (TSM) in estuarine and coastal environments is crucial for understanding ecosystem health, guiding environmental management decisions, and evaluating climate change impacts. Satellite remote sensing offers a powerful tool for this analysis due to its extensive spatial and temporal coverage. Although several algorithms exist for complex coastal and estuarine waters, long-term datasets such as GlobColor's Ocean Color (OC5) and neural network (NN) algorithms are frequently used for robust variability analysis. This study uses the GlobColor NN algorithm to investigate the seasonal and inter-annual variability of Chl-a and TSM in a data-scare region, namely the Meghna estuary in Bangladesh and its adjacent coastal fringe. The other algorithm (i.e. OC5), while offers the longest time series, cannot be used in this region due to the high number of invalid pixels. Therefore, this study examines different environmental factors (i.e. sea surface temperature (SST), photosynthetically active radiation (PAR), rainfall, zonal (ZWC) and meridional (MWC) wind components, and ocean currents) and climatic indices (i.e., El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD)) to understand their influence on the seasonal and inter-annual variability of Chl-a and TSM derived from the GlobColor NN algorithm. Empirical orthogonal function analysis identifies the seasonal signal as dominant in the study region. The seasonal cycle of Chl-a is influenced by factors including MWC, TSM, SST, and rainfall. In contrast, TSM seasonal variations are primarily driven by rainfall and MWC. Post-monsoon Chl-a inter-annual fluctuations are mainly linked to TSM inter-annual variability, with secondary influences from monsoon rainfall and the winter ENSO index. Inter-annual changes in TSM are primarily associated with the winter ENSO index and monsoon rainfall. This research elucidates the primary mechanisms influencing Chl-a and TSM variability in the Meghna estuary and its adjacent coast, thus advancing the understanding of the dynamics in the study region. The information obtained through this study is valuable for scientists, policymakers, and stakeholders involved in the sustainable management of the Meghna estuary and its coastal resources, particularly in the context of climate change.

Industrially induced warming triggered synchronous intensity changes in the East Asian summer and winter monsoons

Anomalies in the East Asian monsoon system significantly disrupt the densely populated East Asian region, underscoring the importance of understanding such changes and improving current predictive abilities. On the basis of instrumental records, previous studies have shown that the East Asian winter monsoon (EAWM) and summer monsoon (EASM) interact with each other. However, owing to the lack of long-term high-resolution EAWM records, it remains unclear how and whether human activity has affected the phase relationship between the EASM and EAWM since the Industrial Revolution. In this study, we present a precisely dated high-resolution EAWM record for the last 300 years from a crater lake in northeastern China. Our results indicate that the EAWM intensity was relatively weak and fluctuated significantly between 1700 and 1850 CE. After 1850 CE, the EAWM strengthened rapidly and exceeded its intensity observed at the end of the Little Ice Age. In addition, a comparison of our reconstructed EAWM record with the published EASM record clearly shows in-phase variations during the Current Warm Period. We concluded that the climatic effects of industrially induced warming enhance the EAWM by slowing the Atlantic meridional overturning circulation and increasing the meridional temperature gradient, while also strengthening the EASM by increasing hemispheric meridional gradients and affecting other large-scale processes. Under the sustained intensification of human activity, the EASM and EAWM are likely to continue exhibiting synchronous variations in the future.

Shear lines trigger heavy rainfalls in the Philippines during the winter monsoon

Heavy rainfall events (HREs) occur almost throughout the year in the Philippines, with relatively limited research during the winter monsoon. This study analyzes the 20-year (2003–2022) daily precipitation from 55 rain gauges and Integrated Multi-satellitE Retrievals for GPM (IMERG) from November to February. HREs are classified into three clusters by employing a cluster analysis on the most pertinent principal modes extracted from the principal component analysis. Each cluster exhibits a distinct heavy rainfall spatial pattern, mostly showing more than 50 mm/day of rainfall in the eastern part of the country. We noted that heavy rainfall in the Philippines during the winter monsoon occurs during a strong East Asian Winter Monsoon and caused by the interaction of shear line and low-level cyclonic vortex. The different location of rainfall maxima in each HRE cluster is a result of the variation of locations of the shear line and cyclonic vortex.

Contrasting orbital rhythms preserved in loess grain-size records across the Chinese Loess Plateau

The loess-paleosol sequences on the Chinese Loess Plateau (CLP) are among the best terrestrial archives for recording orbital-scale global paleoenvironmental and East Asian monsoon changes during the Quaternary Period. Dust provenance and climate patterns vary across the CLP due to its vast size. However, whether available climate proxies were influenced by varying signals from the different dust source areas remains unknown. Here we present time series analysis results of high-resolution grain-size records from four loess sections (Jingbian, Xifeng, Baoji, and Weinan sections) spanning a north to south transect in the eastern CLP across the past 0.7 Ma. By comparison with data from the previously reported Luochuan section in the eastern CLP, and the Gulang, Menyuan, Jingyuan, Lanzhou, and Linxia sections in the western CLP, it is revealed that the dominant orbital signal in grain size variations in the eastern CLP is the ∼100-kyr ice-age cycle, with precession only very weakly expressed. By contrast, western CLP records exhibit both ∼100-kyr and ∼ 20-kyr precession cycles. We show that this contrasting orbital patterns between the eastern and western CLP are likely to be influenced by the climate signals from the respective source regions. We propose that the grain size variations in the western CLP not only contain the ∼100-kyr ice-age related winter monsoon cycles but also precession cycles related to the mid-latitude Westerlies and the Tibetan Plateau. The grain size variations in the eastern CLP are, by contrast, mainly influenced by ∼100-kyr ice-age cycle-regulated winter monsoon changes. The spatial diversity of periodicity in loess grain-size records from the CLP suggests that caution should be taken when discussing the periodicities of loess records based on any single site.

An OSL-dated, stacked Holocene dust mass accumulation rate record on the Chinese Loess Plateau and its implications for Northern Hemisphere dust activity

Accurate reconstruction of geological dust activity is crucial for understanding past climate change and its interaction with dust cycle. Loess on the Chinese Loess Plateau (CLP) is an ideal and sensitive material for revisiting past dust activity. Previously, the changes in the dust mass accumulation rate (MAR) over various time scales were widely established on the CLP. However, few absolutely dated dust records have been obtained and synthesized for the Holocene. This study addresses this gap by compiling 23 optically stimulated luminescence-dated Holocene loess sections across the CLP. We developed a high-quality chronology via Bayesian age-depth modeling and derived a MAR record for each section. Then, we obtained a mean MAR record for the CLP by stacking individual records. We propose that, in contrast to site-specific MARs, stacked MARs represent the mean dust accumulation conditions for the entire CLP and can be used to track relatively large-scale dust activity and climate change. The stacked MAR record suggests a moderate weakening trend of dust accumulation from ∼11.5 to 7.5 thousand years ago (ka BP), followed by a pronounced strengthening trend from ∼7.5 to 3.0 ka BP. A comparison with other regional dust records reveals a shift in dust activity at ∼8–6 ka BP in northern China and western Mongolia. We argue that the East Asian winter and summer monsoons jointly contributed to Holocene mean dust MAR variations on the CLP by changing dust transport wind energy and dust source aridity, respectively. A comparison of Holocene dust records in Asia with those in the northwestern Pacific Ocean and Greenland suggests asynchronous variations in dust activity between proximal and distal Asia-sourced dust deposition. This is because, unlike proximal deposition, distal deposition can be controlled not only by the dust source conditions but also by the intensity and the position of the Westerlies.

Early Pleistocene Orbital‐Scale Variability in Australian Northwest Shelf Sediments

AbstractPaleoclimate proxy records from regions sensitive to humidity/aridity extremes provide crucial insights into the natural forcing mechanisms underlying long‐term climate variability in broader regions. One such area is Northwest Australia, where the Australian monsoon impacts its northernmost fringes, which are bordered by the Great Sandy Desert inland. Marine sediments from the Australian Northwest Shelf record fluvial run‐off and eolian dust input during the wet and dry seasons, respectively. The location is therefore ideal for investigating long‐term variability in the Australian monsoon and Northwest Australian dust flux over orbital timescales. However, there are few continuous, high‐resolution paleoclimate records from this region spanning the early Pleistocene, when strong ice‐climate feedbacks of the late Pleistocene did not yet dominate global climate. Here, we present geochemical and environmental magnetic proxy records that reveal %CaCO3 and dust‐flux variability between 2.9 and 1.6 million years (Myr) ago from International Ocean Discovery Program Expedition 356 Site U1464 on the Australian Northwest Shelf. We establish a new, orbitally‐tuned chronology for Site U1464, primarily based on ∼400 thousand year (kyr) eccentricity cyclicity in %CaCO3, and observe strong obliquity variability (41 and 54 kyr periodicities) but almost no precession signal in the dust‐flux records. We propose that the 41 kyr cycle in Northwest Australian dust flux could be a linear response to East Asian winter monsoon intensity and/or the summer inter‐tropical insolation gradient (SITIG), whereas the 54 kyr cyclicity might be a non‐linear response to obliquity amplitude modulation via the SITIG effect on the cross‐equatorial atmospheric circulations.

Teleconnection Between Early Winter Monsoon System and Harmful Algal Blooms in Shallow Lake Taihu

AbstractThere is a long history of observation and monitoring at local scales with a focus on meteorological modulation of lakes, however, the features at the local scale are heavily influenced by large‐scale atmospheric circulation. Harmful algal blooms (HABs) in large shallow eutrophic lakes are susceptible to local meteorological conditions, but their response to climate system variability is rarely considered. This study reveals that HABs in Lake Taihu, the third largest freshwater lake in subtropical China, are promoted by the weakened East Asian monsoon system in precursory early winter, but show no response in late winter with the low temperature unfavorable for algal metabolism. The weak early winter monsoon system is characterized as the northward‐shifted polar front jet and eastward‐tilted East Asian Trough. The accompanied anomalous descending motion decelerates surface winds over the middle to lower reaches of the Yangtze River including Taihu basin by strengthening atmospheric stratification and decreasing turbulent activity in the lower troposphere. The weakened surface winds reduce sediment resuspension and improve underwater light availability in Lake Taihu, providing favorable light condition for phytoplankton growth. It is indicated that the early‐winter surface winds rather than simultaneous nutrient supply, play a dominant role on the interannual variability of algal biomass in Lake Taihu. The positive algal biomass anomaly in early winter tends to persist and promote HABs in the following warmer seasons. Our finding validates the interannual teleconnection between climate system and HAB variation in Lake Taihu, and provides insights on predicting HABs in subtropical East Asian shallow lakes.

Relationship between Newly Fallen Snow Density and Polarimetric Parameters Obtained from X-Band Radar Observations along the Sea of Japan Coast in January 2021

Abstract The density of newly fallen snow ρN is an important parameter for assessing accumulated snowfall depth. We examined the relationships between polarimetric parameters of X-band radar and the ρN in dry snow cases with ground temperatures less than 0°C. Our study was based on observations at Niigata Prefecture, Japan, along the coastal region of the Sea of Japan. This region is subjected primarily to sea-effect snow during the winter monsoon season, and convective clouds and rimed snow are common. We assumed that snow particles that accumulated on the ground originated from altitudes above an altitude with a temperature of −15°C, and we focused on the ratio of the differential phase KDP to radar reflectivity Zh, which is influenced by both aspect ratio and inverse particle size. We found that KDP/Zh at an altitude with a temperature of −15°C exhibited a greater magnitude for lower ρN values. Its correlation coefficient was the best among the polarimetric parameters that we examined. The difference in ice crystal flatness is highlighted rather than the difference in size because aggregation growth has not progressed at this altitude. On the basis of this result, we propose an empirical relationship between KDP/Zh at an altitude with a temperature of −15°C and ρN on the ground, thereby facilitating the estimation of snowfall depth by combining the estimated ρN with the liquid equivalent snowfall rate from, for example, Zh or KDP. Significance Statement This study aims to estimate the density of newly fallen (just-accumulated) snow from polarimetric radar observations. Understanding the newly fallen snow density will help to determine the exact snowfall depth. Focusing on polarimetric parameters at an altitude with a temperature of −15°C, we conducted radar and ground-based observations of snow particles and found that the newly fallen snow density of dry snow can be estimated. We were able to highlight the difference in ice crystal flatness before aggregation growth progressed by focusing on higher altitudes.

Precession‐Driven Variations in the Indonesian Throughflow Thermocline and Its Implications on the Agulhas Leakage

AbstractThe Indonesian Throughflow (ITF) thermocline, as exclusive water source for the “warm water route” of the Atlantic Meridional Overturning Circulation (AMOC), provides waters that exit the Indian Ocean and join the AMOC upper limb via the Agulhas Leakage (AL). Hence, investigating long‐term variations in the ITF thermocline and its implications on the AL is important for understanding dynamics of the AMOC. Here, the thermohaline history of the ITF thermocline was reconstructed for the last ∼410 kyr based on δ18O and Mg/Ca of planktonic foraminifera from International Ocean Discovery Program Site U1483. By integrating the new and published records, we found that precession drives variation of the ITF thermocline through modulating the intensity of the Australian‐Indonesian winter monsoon, El Niño‐Southern Oscillation‐like states and formation of the North Pacific Tropical Water, in turn exerting a transoceanic influence on the amount of the AL and seawater temperature and salinity of the South Atlantic thermocline.

Mio-pliocene evolution of deep-water channels on the northeastern Bengal fan: Records of signals of Himalaya uplift and South Asian Monsoon from source areas

Submarine channels, acting as major conduits for delivering terrestrial sediments into the deep sea, are sensitive to source-region uplift and climate variations. Using new 3D seismic data, previously published paleoenvironmental data, and IODP/ODP data, we characterize stratigraphic time changes in deep-water channels on the northeastern Bengal Fan and suggest that their long-term evolution relates to contemporaneous changes of Himalaya uplift and South Asian Monsoon. Our results show that around the boundary between the Miocene and Pliocene Epochs, the sedimentary characteristics of deep-water channels were changing at about the same time as decreased rates of Himalaya uplift and changes in the monsoonal climate. It is strongly suggested that environmental signals could successfully propagate from the Himalaya to the deep sea and play a dominant control on the long-term evolution of deep-water channels. During the late Miocene, orogen-wide and substantial Himalaya uplift and humid monsoonal climates (dominance of summer monsoon) generated a sediment supply with high fluxes, which allowed coarser-grained sediments to reach further into the basin and thus caused the formation of larger-scale, non-leveed erosional channels that have avulsion and confluence phenomena. After the Miocene, local and limited Himalaya uplift and arid monsoonal climates (dominance of winter monsoon) led to a sediment supply with low fluxes, during which only finer-grained sediments reached deep water and gave rise to smaller-scale, leveed aggradational channels that mainly have splay deposits. Between the late-Miocene and post-Miocene periods, detrital zircon U-Pb ages of Bengal Fan samples from IODP cores reflect a sediment provenance change from the mixing of Brahmaputra and Ganges Rivers to the end-member of Brahmaputra River, broadly coeval with the variations of Himalaya uplift and South Asian Monsoon. Moreover, Bengal Fan cores record a Mio-Pliocene decrease in sedimentation rates and maximum grain sizes and an increase in mudstone contents, consistent with the variations of sediment yield in the source catchments. Observations and interpretations from the current study, therefore, contribute to a better understanding of how the long-term evolution of submarine channels respond to tectonic and climatic perturbations in source areas and may help recognizing similar process-response relationships in other areas.

Sedimentation rate changes across the Chinese Loess Plateau from luminescence dating of Malan loess in the Sanmen Gorge

Abstract The Chinese Loess Plateau (CLP), recognized as the world's largest loess plateau, has been a subject of ongoing debate regarding the continuity of its sedimentary loess sequence due to its intricate depositional environment. In this study, we conducted dating on a 9.8-m-long Malan loess core obtained from the Sanmen Gorge in the southern CLP using optically stimulated luminescence (OSL). The OSL dates indicate loess deposition between 52.4 and 11.3 ka, with no apparent hiatus on a millennial scale, and a sedimentation rate (SR) exhibiting six distinct episodes. Additionally, a comprehensive review of 613 OSL ages from 18 sections at 14 sites across the CLP was conducted. The results reveal loess deposition at most sites shows no apparent hiatus on a millennial scale over the past 60 ka, except for two specific locations. High SR episodes during Marine Isotope Stage (MIS) 3 across the CLP were attributed to heightened dust emissions from the source region and an enhanced dust deposition efficiency, while MIS 2 deposits were influenced by an intensified East Asian winter monsoon. Low SR episodes during MIS 1 at most sites were likely associated with reduced atmospheric transportation and pedogenesis. Spatially heterogeneous SR variations across the CLP might be influenced by local depositional environments.

Desert-oasis evolutionary process in the Tarim Basin since ∼ 2.2 ka B.P. during the late Holocene and their environmental implications

Oases, serving as ideal locations for human settlements in arid regions, exhibit extreme sensitivity to regional climatic fluctuations. Consequently, the oasis deposition sediments play a pivotal role in the study of regional paleoenvironmental changes and the exploration of prehistoric human-environment interactions. The YSD and STM sections, both typical aeolian-lacustrine sections located at the edge of the Tarim Basin, were investigated in this study. By analyzing optically stimulated luminescence (OSL) dating results and grain-size proxy indicators, the environmental evolution patterns in the Tarim Basin since approximately 2.2 ka BP were reconstructed. Additionally, the parametric end-member analysis on the grain-size data was conducted to explore the environmental significance revealed by each end-member. The research findings indicate that: (1) ∼ 2.2–1.8 ka B.P., sediment morphology and grain-size parameters indicate that the climate in the Tarim Basin recorded by the STM section was relatively dry, with rivers gradually receding and frequent sand-drift activities. During the development of the YSD section (∼1.67–1.5 ka B.P.), the environmental conditions in the Tarim Basin transitioned to a relatively humid phase, with the Yarkand River experienced multiple episodes of natural diluvial deposition. The grain-size data of two sections both comprise five sedimentary dynamic components, serving as sensitive indicators of regional humidity conditions and winter monsoon intensity. (2) The oasis development in the Tarim Basin during the late Holocene (particularly refers to between ∼ 2.2 ka B.P. and ∼ 1.4 ka B.P.) exhibits a significant positive correlation with temperature records. (3) Environmental changes and human activities jointly regulate the spatial and temporal distribution and number of archeological sites during the development of both sections. However, the dominance of the two factors varied across different historical periods.

Air-sea CO2 exchange in the western Pacific influenced by monsoon and giant diatom (Ethmodiscus rex) blooms during the last deglaciation

The concentration of atmospheric CO2 increased rapidly during the last deglaciation due to CO2 outgassing from oceans. However, records of deglacial surface seawater pCO2-sw are sparse, hindering our understanding of the process and mechanism of air-sea CO2 exchange and its influence on glacial-interglacial climate change. Here we reconstructed surface seawater pCO2-sw for the last deglacial period using carbon isotope composition (δ13C) of giant diatom (Ethmodiscus rex) frustules from deep-sea sedimentary core collected in the Philippine Sea, western Pacific. Results showed that air-sea CO2 was fluctuating in the western Pacific during the last deglaciation. The gradients of air-sea CO2 are dominated by monsoon and biological productivity. The enhanced East Asian winter Monsoon and shallow thermocline during late Heinrich Stadial 1 maintained equilibrium in the air-sea CO2 exchange balance. During the Bølling period, enhanced East Asian Summer Monsoon has been observed to accelerate the dissolution of eolian-dust and promoted the growth of Ethmodiscus rex, which has been linked to increased primary productivity and, consequently, the uptake of atmospheric CO2 in the western Pacific. During the Allerød period, continued enhancement of EASM allowed the Philippine Sea to act as a weak CO2 source releasing CO2 to the atmosphere. During the Younger Dryas period, as the EASM weaken and the EAWM strengthen, ΔpCO2(sw-atm) decreased. Our findings highlight the tropical ocean’s role in deglacial air-sea CO2 exchange and provide insights into the monsoonal and biological drivers of the processes.

Quaternary provenance changes in the loess deposits of the western Chinese Loess Plateau: Insights from U-Pb age spectra of detrital zircon

The western region of the Chinese Loess Plateau (CLP) on the western side of the Liupan Mountains connects the Tibetan Plateau with the deserts of the northern arid zones. This region is key for understanding of the coupled relationship between tectonic uplift and surface processes (erosion and climate) on the Tibetan Plateau; however, the variation of Quaternary wind-dust sources in the region remains uncertain, confounding analysis. In this paper, we conduct a source tracing investigation using detrital zircon U-Pb dating of 12 loess layers from the Huining aeolian sedimentary sequence of the western CLP, reconstruct the history of provenance changes during the Quaternary Period, and further explore driving mechanisms. Results show that aeolian dust from the western CLP is mainly from the northeastern margin of the Tibetan Plateau (NTP). At 1.8–1.66 Ma, the main source region was the NTP, which corresponds to the Episode C uplift event of the Tibetan Plateau. The dominant source area transitioned to the Gobi Altay Mountains (GAMs) around 1.5–1.4 Ma. This shift suggests that the tectonic uplift of the Tibetan Plateau had entered a period of stasis following the conclusion of Episode C, leading to increased transport of detrital material from the GAMs by the East Asian Winter Monsoon. After 1.24 Ma, the dominant source region abruptly changed from the GAMs to the NTP and lasted until 0.04 Ma. The topographic fluctuations caused by the Kunhuang Movement appears to have been the main reason for the sudden source change. Based on our results and evidence from previous studies, the source changes that occurred during the Quaternary Period were in response to a combination of tectonic events and climate change. Comparison of zircon age spectra between the eastern and western CLP further support the idea that the Plateau Winter Monsoon was the main transport system for aeolian dust in the western CLP.

Western Mongolian Plateau exhibits increasing Holocene temperature

The scarcity of Holocene winter temperature records from the core area of the Mongolian-Siberian High (MSH) hampers our understanding of the long-term evolution of the MSH and its modulation of the East Asian Winter Monsoon (EAWM). Here we use the body size of Pediastrum, a new and sensitive temperature proxy, from the sediments of Tolbo Lake in the western Mongolian Plateau, to reconstruct changes in winter temperature in the core area of the MSH during the Holocene. A large-scale investigation of modern Pediastrum body size across East Asia indicates that it is an accurate proxy indicator for mean winter temperature. The Holocene winter temperature based on Pediastrum body size from Tolbo Lake shows a general warming trend with the maximum at ∼2.6 ka. The current warming has attained the magnitude of the previous Holocene maximum, despite the underlying forcing being different. The mid-late Holocene winter warming in inland Eurasia may have weakened the MSH and reduced the intensity of the EAWM.

Changing circulations challenge the sustainability of cold water mass and associated ecosystem under climate change

Bottom cold water mass provides abundant nutrients and cool water in summer, playing a pivotal role in the productivity of marine ecosystem and sustainable aquaculture development. Located in the most densely populated region, the Yellow Sea cold water mass (YSCWM) is a unique one influencing hundreds of millions of people living in the rim of the Yellow Sea. As anthropogenic carbon emissions continue, how the YSCWM will be altered by climate change becomes a pressing issue, but remains elusive. Using an unprecedented set of climate models with high resolution and biogeochemical components, we find that the volume of the YSCWM will shrink by 48% to 2040–2050, along with the bottom temperature warming of 0.4 ± 0.1 °C dec−1 and the dissolved oxygen concentration declining of 0.09 ± 0.04 mg (L dec)−1. The significant destruction of the YSCWM is driven by the strengthened Yellow Sea Warm Current (YSWC). The reduced land-sea thermal contrast is the cause of the circulation change, by weakening the East Asian winter monsoon. Due to the resultant profound habitat reduction for marine life, predicting the change of the YSCWM will have far-reaching influences on the future policy-making for sustainable development of offshore aquaculture.

Impact of seasonal variations in fronts on suspended sediments transport off the coastal area of Fujian Province

The Zhejiang-Fujian (Zhe-Min) coastal muddy area plays a crucial role in facilitating sediment exchange through a cross-front. The mud depocenter off the Zhe-Min coastal area is a source of suspended sediment that can be transported to the continental shelf of the East China Sea (ECS). Although the front of the inner shelf of the ECS has been extensively reported, the cross-front material transport off the coastal area of Zhe-Min in summer has not been well studied, especially using measured data. To reveal how the front controls the transport of suspended sediment, this study focuses on the impact of fronts on the dispersion of suspended sediment off the coastal area of Fujian Province in different seasons. The results indicate that the front acts as a barrier, inhibiting the dispersion of suspended sediment into the sea. The high-concentration suspended sediment is mainly found to the northwest of the front, with an average SSC of 8.5 mg/L in winter and 3.1 mg/L in summer. The suspended sediment concentration (SSC) follows a V-shaped distribution along the cross-isobath transects, with lower SSC observed at the 50-m isobath compared with the shallow water area and the deep water area. The SSC at the front was the lowest, with an average concentration of 2.3 mg/L in winter and 1.9 mg/L in summer. The front is crucial for the development of the Zhe-Min coastal muddy area. The winter monsoon is strong, resulting in a sufficient supply of suspended sediments in the muddy area and a high transport flux of suspended sediments in the nearshore. The front hinders the dispersion of high-concentrated sediment from the nearshore to the offshore, resulting in the deposition of fine-grained sediments in the nearshore and the formation of an inner shelf muddy sedimentary zone. The findings of this study will help improve our understanding of the sediment source-to-sink processes in the ECS and land–sea interactions.