Global and Planetary Change最新文献

{"title":"Stalagmite records of spatiotemporal hydroclimatic variations in monsoonal China during 47–12 ka BP","authors":"Miaomiao Wang,&nbsp;Haiwei Zhang,&nbsp;Youwei Li,&nbsp;Rui Zhang,&nbsp;Jian Wang,&nbsp;Hanying Li,&nbsp;Yuteng Zhao,&nbsp;Xiaomei Zhang,&nbsp;Zeyuan Liang,&nbsp;Youfeng Ning,&nbsp;Hai Cheng","doi":"10.1016/j.gloplacha.2024.104639","DOIUrl":"10.1016/j.gloplacha.2024.104639","url":null,"abstract":"<div><div>Recent high-resolution sediment records, such as Greenland ice cores and Chinese stalagmites, have greatly enhanced our understanding of millennial-scale climate variability during Heinrich Stadials (HSs) of the Last Glacial Period, particularly highlighting the diminished intensity of the Asian Summer Monsoon (ASM). These records reveal precise temporal correlations between high-latitude climate changes and low-latitude monsoon variability, especially in the Asian monsoon region. However, the scarcity of stalagmite records from southeastern China has limited our understanding of the spatio-temporal patterns of monsoonal precipitation variability during these abrupt climate events, as most published records are concentrated in central-northern and southwestern China. In this study, we present a high-resolution hydroclimate reconstruction based on stalagmite YXG01 from Yindi Cave, Hubei Province, China, using 42 U-Th dates and 698 δ¹⁸O and δ¹³C isotope measurements, spanning the 11.92–47.47 ka BP interval. Our δ¹⁸O record shows four positive excursions, indicating significantly weakened ASM intensity during the four most recent HSs (HS1 to HS4), consistent with previous studies. During these HSs, freshwater influx into the North Atlantic weakened the Atlantic Meridional Overturning Circulation, cooled Northern Hemisphere temperatures, and reduced ASM circulation/intensity, resulting in consistent positive δ¹⁸O shifts in precipitation and stalagmites across the East Asian monsoon region. We found that the amplitude of stalagmite δ¹⁸O variations during the HSs decreases progressively from Southwest China to Southeast China, a trend that aligns with simulated changes in precipitation δ¹⁸O. The smaller amplitude of δ¹⁸O shifts in southeastern China during the HSs may be linked to increased moisture contributions from the western Pacific Ocean and enhanced local precipitation. During these HSs, anti-phased variations between YXG01 δ¹⁸O and δ¹³C, together with temperature reconstructions and model simulations, suggest favorable hydroclimatic conditions in the mid-lower reaches of the Yangtze River Valley. Increased precipitation and moderate temperature may have enhanced vegetation growth, resulting in lower speleothem δ¹³C values despite the overall weakening of ASM circulation. Our new speleothem YXG01 record reveals two important observations from Southeast China: a smaller amplitude of speleothem δ¹⁸O shifts and anti-phased δ¹⁸O and δ¹³C variations during the HSs. Further model simulations are necessary to fully explore the underlying climate dynamics driving these patterns.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"244 ","pages":"Article 104639"},"PeriodicalIF":4.0,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142718380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New Sea-ice biomarker data from Bering-Chukchi Sea surface sediments and its significance for pan-Arctic proxy-based sea-ice reconstruction","authors":"Jiang Yi-ao Zhang ,&nbsp;Xiaotong Xiao ,&nbsp;Ruediger Stein ,&nbsp;Wenshen Xiao ,&nbsp;Rujian Wang ,&nbsp;Yang Ding ,&nbsp;Lupeng Nie ,&nbsp;Meixun Zhao","doi":"10.1016/j.gloplacha.2024.104642","DOIUrl":"10.1016/j.gloplacha.2024.104642","url":null,"abstract":"<div><div>Sea ice is an essential component in polar regions and plays an important role in global climate changes. Knowing sea-ice variabilities on long-term time scales is critical to understand the rapid sea-ice decline in recent decades and to predict future Arctic changes. In this study, a suite of biomarkers including highly branched isoprenoids (IP₂₅ and HBI III (Z)) and sterols (brassicasterol and dinosterol) were measured in 55 surface sediments from the Bering-Chukchi Sea to central Arctic Ocean transect. PIP₂₅ indices were calculated with sea-ice biomarker IP₂₅ and phytoplankton biomarkers (brassicasterol, dinosterol and HBI III (Z)). The new data were combined with published data (<em>n</em> = 875) to complete the pan-Arctic dataset of biomarkers (<em>n</em> = 1062) in surface sediments. The compiled extended total data in general support previous pan-Arctic PIP₂₅ studies and by this the reliability of the PIP₂₅ approach for (paleo) sea-ice reconstructions. Furthermore, this study provides an extended basis for semi-quantitative paleo-sea-ice reconstruction in different regions of the Arctic Ocean. Phytoplankton biomarkers HBI III (Z) display highest values near the winter sea ice (WSI) edge in the pan-Arctic, reflecting the ice-edge conditions. P_IIIIP₂₅ show significant correlations with satellite spring/summer and autumn sea-ice concentration in the Pacific Sector of the pan-Arctic dataset (Bering-Chukchi Sea shelves, Chukchi Borderland and Canada Basin), and with spring/autumn sea-ice concentration in the Atlantic sector of the pan-Arctic dataset (Fram Strait, East Greenland shelf and Barents Sea). P_IIIIP₂₅ index seems to be reliable to reconstruct the paleo-sea-ice conditions in the Pan-Arctic, as well as P_BIP₂₅ and P_DIP₂₅ (using brassicasterol and dinosterol as phytoplankton biomarker, respectively). Furthermore, regional calibrations of comprehensive biomarker and PIP₂₅ datasets against known sea-ice conditions would add further confidence in their application for paleo-sea-ice reconstruction. Based on our extended HBI III dataset we did not find that the HBI TR₂₅ index was a reliable proxy for phytoplankton spring blooms on pan-Arctic scales. Certainly, deciphering the origin of certain biomarkers (e.g. HBI III (Z) and (E)) is still crucial for their application in further validation of PIP₂₅ and TR₂₅ indices application.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"244 ","pages":"Article 104642"},"PeriodicalIF":4.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Human settlement and destructive activities disrupt the positive contribution of dust to plant biomass growth over the past 2000 years","authors":"Lin Chen ,&nbsp;Youliang Huang ,&nbsp;Menghan Qiu ,&nbsp;Zhilun Li ,&nbsp;Rui Yang ,&nbsp;Mengjing Li ,&nbsp;Huiling Sun ,&nbsp;Lixiong Xiang ,&nbsp;Shanjia Zhang ,&nbsp;Xiaozhong Huang ,&nbsp;Aifeng Zhou","doi":"10.1016/j.gloplacha.2024.104640","DOIUrl":"10.1016/j.gloplacha.2024.104640","url":null,"abstract":"<div><div>The dual pressures of global warming and increased anthropogenic activities pose significant threats to terrestrial vegetation ecosystems. To better understand the impacts of climate change and human activities on terrestrial vegetation ecosystems, we reconstructed the changes in vegetation and plant biomass over the past 4500 years using <em>n</em>-alkane records from sediments of two alpine lakes in northwestern China: Xiannv Lake and Tianchi Lake. Our results indicate that changes in the spatial variability of plant biomass are not related to temperature and precipitation. Furthermore, CO₂ fertilization and nutrient inputs from dust contributed to the observed changes in plant biomass. We also compared the history of human activities in the Tianshan Mountains, the eastern Silk Road, and the Hunsandak Sandy Land, and find that the demand for plant resources—whether for human settlement, military construction, or warfare—may have caused a sudden decline in terrestrial vegetation, thereby disrupting the positive effects of dust on plant biomass growth.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"244 ","pages":"Article 104640"},"PeriodicalIF":4.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Response of atmospheric CO2 changes to the Abyssal Pacific overturning during the last glacial cycle","authors":"Yanan Zhang ,&nbsp;Gang Li ,&nbsp;Jimin Yu ,&nbsp;Yi Zhong ,&nbsp;Jianghui Du ,&nbsp;Xun Gong ,&nbsp;Xiaodong Jiang ,&nbsp;Congcong Gai ,&nbsp;Shiying Li ,&nbsp;Qingsong Liu","doi":"10.1016/j.gloplacha.2024.104636","DOIUrl":"10.1016/j.gloplacha.2024.104636","url":null,"abstract":"<div><div>Despite its critical role in regulating the global climate and carbon cycle, the evolution of deep Pacific circulation has not been fully deciphered during the last glacial cycle. The effect of deep Pacific hydrographic change (e.g. oxygenation and circulation) on atmospheric CO₂ variation is still uncertain. Here, we study redox-sensitive elements including V-U-Mn and benthic foraminiferal δ¹³C at the HYIV2015-B9 site in the southern South China Sea (SCS) to reconstruct the oxygenation and δ¹³C signals of water masses during the last glacial cycle. The intra-basin benthic foraminiferal δ¹³C gradient suggests enhanced stratification of the deep Pacific during the glacial compared to the interglacial, implying sluggish abyssal Pacific overturning. This is consistent with weak Pacific Deep Water (PDW) ventilation, as indicated by high contents of authigenic V and U, and low authigenic Mn. The inferred sluggish abyssal Pacific overturning is probably associated with less transport of Lower Circumpolar Deep Water, facilitating the expansion of respired carbon storage in the glacial deep Pacific. Meanwhile, the atmospheric CO₂ rise is closely related to active abyssal Pacific overturning since late MIS 5, particularly when considering the impact of Southern Ocean upwelling modulated by Earth's obliquity. Overall, our data indicate the critical role of abyssal Pacific overturning in the carbon cycle, revealing the potential pathway for deep carbon dioxide outgassing in the North Pacific.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"244 ","pages":"Article 104636"},"PeriodicalIF":4.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evapotranspiration increase is more sensitive to vegetation greening than to vegetation type conversion in arid and semi-arid regions of China","authors":"Yixuan Zhu ,&nbsp;Zhoutao Zheng ,&nbsp;Guang Zhao ,&nbsp;Juntao Zhu ,&nbsp;Bo Zhao ,&nbsp;Yihan Sun ,&nbsp;Jie Gao ,&nbsp;Yangjian Zhang","doi":"10.1016/j.gloplacha.2024.104634","DOIUrl":"10.1016/j.gloplacha.2024.104634","url":null,"abstract":"<div><div>Evapotranspiration (ET) is a crucial component of both the water cycle and energy balance, with vegetation being a key factor influencing ET. Vegetation impacts ET primarily through two modes: vegetation growth change (VGC) and vegetation type conversion (VTC). Despite the different mechanisms by which VGC and VTC influence ET, previous studies have rarely differentiated their individual effects. This has left the relative contributions of VGC and VTC to ET changes unclear. To address this gap, this study focuses on the arid and semi-arid regions of China (ASAC), where substantial vegetation changes have been observed. The spatiotemporal patterns of ET in ASAC were analyzed using remote sensing ET data from 2001 to 2018. The leaf area index (LAI) and land use/land cover (LULC) data were incorporated to perform pairwise comparison and contribution analysis to investigate the specific effects of VGC and VTC on ET. The results revealed a significant increase in mean annual ET across ASAC, with a rate of 4.5 mm/yr (<em>p</em> &lt; 0.05). This increase was more pronounced in forest land and cropland compared to grasslands. ET increased across all seasons, with the largest increase occurring in summer, accounting for approximately 50 % of the annual ET increment. The pairwise comparison and contribution analysis indicated that ET in ASAC is more sensitive to vegetation greening than to VTC. VTC played a moderating role in ET changes, with relative contribution ranging from 1.3 % to 57.8 % across different LULC change types. These findings enhance our understanding of how vegetation changes influence ET. They can also provide valuable insights for land management strategies in ASAC, aiming to optimize vegetation construction and promote ecosystems sustainability.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"244 ","pages":"Article 104634"},"PeriodicalIF":4.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intra-seasonal variations of dust activity over East Asia in spring 2023 and their mechanisms","authors":"Xiaoling Wu ,&nbsp;Chenglai Wu ,&nbsp;Zhaohui Lin ,&nbsp;Mingzhu Yang","doi":"10.1016/j.gloplacha.2024.104638","DOIUrl":"10.1016/j.gloplacha.2024.104638","url":null,"abstract":"<div><div>Dust activity in East Asia has shown multi-scale temporal variations in the past. Many studies have been devoted to the interannual variations of dust activity, but little attention is paid to its variations at the intra-seasonal scale and our knowledge on this is still limited. Several dust storms have occurred over East Asia in spring 2023, which is taken as a good example for us to explore the intra-seasonal variations of dust activity. Based on station observations of dust events, meteorology reanalysis, and satellite observations of surface vegetation cover, here we find that there is much difference in dust storm activity between March and April of 2023 in terms of both the location and intensity. Dust storms mainly occurred in the central and eastern parts of Inner Mongolia and in the central and northern parts of Tarim Basin in March. In contrast, they mainly occurred in the western part of Inner Mongolia, eastern part of Northwest China, and a large region of Tarim Basin. For the regional mean number of dust storm days (N_DS), it is significantly higher than the climatological mean value of 2003–2022 in April but lower for March of 2023. Further analysis reveals that the frequency of strong wind is below (above) the climatological mean for March (April) in the Tarim Basin and Gobi Deserts, indicating that wind speed may play a key role in the intra-seasonal variations of dust storm activity, although its effect is offset or enhanced by that of soil moisture and vegetation cover to a lesser extent. The shift of wind field is closely related to the evolution of geopotential height from positive anomaly in March to negative anomaly in April in Mongolia Plateau and southern Central Siberia at 500 hPa. Overall these results highlight the intra-seasonal variation of dust activity in spring 2023 in East Asia and the essential role of associated atmospheric circulation in driving this.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"244 ","pages":"Article 104638"},"PeriodicalIF":4.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distribution and fluxes of trimethylamine in the Northwest Pacific marginal seas","authors":"Fei Jiang ,&nbsp;Zhen Zhou ,&nbsp;Jinyan Wang ,&nbsp;Wen-Jia Guan ,&nbsp;Qiao Liu ,&nbsp;Shi-Hai Mao ,&nbsp;Xiao-Jun Li ,&nbsp;Ni Meng ,&nbsp;Gui-Peng Yang ,&nbsp;Guang-Chao Zhuang","doi":"10.1016/j.gloplacha.2024.104635","DOIUrl":"10.1016/j.gloplacha.2024.104635","url":null,"abstract":"<div><div>Trimethylamine (TMA) is one of the dominant volatile amines that can impact atmospheric nucleation and serve as important carbon and nitrogen sources for microbes in marine environments. Despite the significance of this climate relevant gas, the distribution, fluxes and controls of TMA remain largely unconstrained in the ocean. Here we reported the abundance of TMA in the water column, sediment and atmosphere of Northwest Pacific marginal seas, and illustrated the distribution, source and exchange fluxes across the sea-air and sediment-water interfaces. TMA in surface waters ranged from 0.3 nM to 10.1 nM (2.5 ± 2.6 nM) and decreased from inshore to offshore waters. Significant relationships were observed between TMA and chlorophyll <em>a</em>, suggesting the biological control of TMA production from phytoplankton. The average sea-to-air flux of TMA in the Yellow Sea and East China Sea was 0.12 μmol m⁻² d⁻¹, contributing to an annual emission of 0.7 Gg N TMA to the atmosphere, which suggested a significant relative contribution of continental shelf seas to global oceanic TMA emissions. In marine sediments, dissolved TMA in the porewater was low (2.5–22.4 nM), while the exchangeable and base-extractable pools of TMA from the solid phase were much more abundant (&gt; 200 nmol kg⁻¹). Surface sediment was a source of TMA in the overlying waters, and the estimated sediment-water flux was 3.5 nmol m⁻² d⁻¹. Collectively, these results shed light on the sources and sinks of TMA across the air-sea and sediment-water interfaces and highlighted the importance of coastal waters as a significant source of TMA to the atmosphere.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"244 ","pages":"Article 104635"},"PeriodicalIF":4.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New insights into Holocene dust activity in eastern Uzbekistan","authors":"Yougui Song ,&nbsp;Haoru Wei ,&nbsp;Mengping Xie ,&nbsp;Shugang Kang ,&nbsp;Xiulan Zong ,&nbsp;Nosir Shukurov ,&nbsp;Shukhrat Shukurov ,&nbsp;Yun Li ,&nbsp;Yue Li ,&nbsp;Mingyu Zhang","doi":"10.1016/j.gloplacha.2024.104633","DOIUrl":"10.1016/j.gloplacha.2024.104633","url":null,"abstract":"<div><div>Central Asia is a substantial source of long-range-transported dust, yet the historical and geological variability of dust activity in this region remains poorly understood. This study presents a Holocene record of dust activity from a 6.2-m loess section located near Tashkent in the westerlies-dominated region of eastern Uzbekistan, Central Asia. Utilizing the quartz optically stimulated luminescence dating protocol, we employed grain-size analysis and trace-element geochemistry to reconstruct Holocene dust activity. Dating indicated that this section was deposited over the last 9.6 ka. Four grain-size end-member (EM) components were identified, each representing different atmospheric circulation patterns and sedimentary environments. End-member 2, with a modal size of 11.2 μm, likely represents particles transported by upper-level westerlies, while EM 3, with a modal size of 28.3 μm, is associated with near-surface winds linked to dust storms. Zirconium is concentrated in coarse particles, whereas Rb is enriched in finer particles during dust deposition. Therefore, higher Zr/Rb ratios indicate stronger or more distant dust transport; hence, the Zr/Rb ratio is a reliable indicator of dust activity. Holocene dust activity was reconstructed using the EM 3 component and Zr/Rb ratio, revealing several extreme dust-storm events. During the early–middle Holocene (9.6–5 ka), dust activity was stronger but less frequent compared with the subsequent shift to lower intensity but higher frequency dust events. The long-term orbital-scale decline in Holocene dust activity can be attributed to reduced solar insolation and weakening of the Siberian High since the early Holocene. On a centennial to millennial scale, extreme dust-storm events are teleconnected with cold ice-rafted debris events in the North Atlantic. Projections for the coming century suggest that dust activity in eastern Uzbekistan may further decline, accompanied by an increase in precipitation. This study provides new insights into understanding and predicting dust storms in Central Asia.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104633"},"PeriodicalIF":4.0,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-elevation Qilian Mountains and its inspiration for tectonics and biodiversity during the late Middle Miocene","authors":"Yongheng Yang ,&nbsp;Yunfa Miao ,&nbsp;Xuelian Wang ,&nbsp;Tao Zhang ,&nbsp;Liwu Li","doi":"10.1016/j.gloplacha.2024.104632","DOIUrl":"10.1016/j.gloplacha.2024.104632","url":null,"abstract":"<div><div>The accurate paleoelevation reconstruction of the Qilian Mountains is critical to advancing our understanding the integrity of the Tibetan Plateau (TP) uplift model, its deep structural mechanisms, and corresponding connections with climatic, environmental, and biodiversity changes. Recently, the first quantitative reconstruction of the paleomidrange (i.e., average elevation of the basin and mountains) of the northern Tibetan Plateau (NTP) was completed, using innovative palynological paleoaltimetry-TP/TPAP [(<em>Tsuga</em>% + <em>Podocarpus</em>%) / (<em>Tsuga</em>% + <em>Podocarpus</em>% + <em>Abies</em>% + <em>Picea</em>%)] ratios, which revealed a rapid uplift of the NTP from low to high elevations during the late Middle Miocene. Here, we analyzed the Ebotu Fauna pollen record (13–12 Ma) from the Hongyazi Basin, situated within the Qilian Mountains, to directly infer the paleoelevation of this region. The pollen assemblages were predominantly composed of conifers (average of 64.0 %), including <em>Picea</em>, <em>Cedrus</em>, and <em>Pinus</em> of the Pinaceae, as well as Cupressaceae, with broadleaves and steppes taxa each accounting for &lt;15 %. This pollen composition evidently reflects a vegetation type dominated by high-mountain conifers forest, consistent with Middle Miocene pollen assemblages from the Qaidam Basin. Application TP/TPAP ratios yielded a paleomidrange of 3492 ± 87 m at 13–12 Ma. Combined with the known elevation of the Qaidam Basin during this period (1885 ± 566 m), the elevation of the Qilian Mountains was calculated to be 4338 ± 653 m. In turn, an elevation of 2646 ± 740 m was obtained for the Hongyazi Basin. This high-elevation terrain provides evidence to support the multi-stage convective removal model of the TP caused by crustal shortening and thickening. It also led to the formation of a humid ecosystem dominated by conifers forest in the Qilian Mountains, supporting the diversification of mammalian taxa.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104632"},"PeriodicalIF":4.0,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Widespread upper-ocean deoxygenation in the Alpine-Mediterranean Tethys during the Toarcian Oceanic Anoxic Event","authors":"Wenhan Chen ,&nbsp;David B. Kemp ,&nbsp;Hugh C. Jenkyns ,&nbsp;Stuart A. Robinson ,&nbsp;Shouyi Jiang ,&nbsp;Chengrong Pan ,&nbsp;Chao Li","doi":"10.1016/j.gloplacha.2024.104631","DOIUrl":"10.1016/j.gloplacha.2024.104631","url":null,"abstract":"<div><div>The early Toarcian (∼183 Ma) was characterized by pronounced climate warming associated with massive release of ¹³C-depleted carbon to the exogenic system, as evidenced by globally recognized negative carbon-isotope excursions (N-CIE) in biospheric carbon reservoirs. Global warming during this interval triggered a variety of environmental perturbations, of which large-scale marine deoxygenation (as indicated by the presence of widespread organic carbon-rich deposits) is arguably diagnostic and led to the naming of the interval in question as the Toarcian Oceanic Anoxic Event (T-OAE). Nevertheless, the spatial variability of water-column redox during the T-OAE is unclear because most sedimentological and geochemical methods used to infer marine redox are likely reflective of bottom-water and/or pore-water conditions. Here we report new I/(Ca + Mg) and Cerium (Ce)-anomaly data from two carbonate successions from northern Italy that encompass the T-OAE interval. Both successions were deposited in the Alpine-Mediterranean Tethys; one in a shallow-water platform setting and the other within a pelagic environment. Both successions record an abrupt drop in I/(Ca + Mg) values, coupled with positive excursions in Ce-anomaly records at the onset of the T-OAE N-CIE. The synchronized changes in marine iodate depletion and Ce enrichment suggest widespread and significant upper-ocean deoxygenation in the Alpine-Mediterranean Tethys. This redox pattern is attributed to an expanded oxygen minimum zone (OMZ) formed as a result of sluggish oceanic circulation under climate warming, augmented by enhanced dissolved oxygen consumption due to increased nutrient availability and the consequent eutrophication in both proximal and distal settings. Because reduced seawater dissolved oxygen [O₂] would increase the ecological stress and constrict any potentially hospitable habitats, the broad synchroneity between biotic turnovers and upper-ocean deoxygenation in the Alpine-Mediterranean Tethys is compatible with a potential causal link.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104631"},"PeriodicalIF":4.0,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}