Pub Date : 2024-12-22DOI: 10.1016/j.gloplacha.2024.104688
Jackson C. McCaffrey, Stephen J. Gallagher, Malcolm W. Wallace, Tanita Averes, Stanislaus G. Fabian, Katja Lindhorst, Lars Reuning, Sebastian Krastel
The tropical North West Shelf of Australia hosts a diverse range of modern reefs. Six shelf edge isolated atolls are present north of 18°S including: Ashmore Reef, Scott Reef and Seringapatam Reef, and three Rowley Shoals. The Ningaloo Reef is a fringing reef around the North West Cape at 22°S. All of these reefs are the remnants of a vast 2000 km long barrier reef that drowned during the Late Miocene (∼10 Ma). Despite extensive hydrocarbon exploration in the region, the history of these isolated reefs is not well known. Seismic analyses combined with stratigraphic analyses of International Ocean Discovery Site U1464 near the Rowley Shoals has revealed that these modern isolated atolls have a complex evolution related to climate and tectonism as they managed to survive on their Miocene barrier reef foundation.
{"title":"The Rowley Shoals atolls: Remnants of a Miocene great barrier reef on the north-west Australian margin","authors":"Jackson C. McCaffrey, Stephen J. Gallagher, Malcolm W. Wallace, Tanita Averes, Stanislaus G. Fabian, Katja Lindhorst, Lars Reuning, Sebastian Krastel","doi":"10.1016/j.gloplacha.2024.104688","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104688","url":null,"abstract":"The tropical North West Shelf of Australia hosts a diverse range of modern reefs. Six shelf edge isolated atolls are present north of 18°S including: Ashmore Reef, Scott Reef and Seringapatam Reef, and three Rowley Shoals. The Ningaloo Reef is a fringing reef around the North West Cape at 22°S. All of these reefs are the remnants of a vast 2000 km long barrier reef that drowned during the Late Miocene (∼10 Ma). Despite extensive hydrocarbon exploration in the region, the history of these isolated reefs is not well known. Seismic analyses combined with stratigraphic analyses of International Ocean Discovery Site U1464 near the Rowley Shoals has revealed that these modern isolated atolls have a complex evolution related to climate and tectonism as they managed to survive on their Miocene barrier reef foundation.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"72 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905669","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}
The mid-latitude Westerlies and the East Asian winter monsoon (EAWM) are two major atmospheric circulation systems influencing dust activities in the Northern Hemisphere (NH). However, the interplay between these wind systems and their effects on regional dust activities remain poorly understood. In this study, we present a well-dated aeolian sedimentary sequence from the loess section (ZES) on the southern slope of the Qilian Mountains in the northeastern Qinghai-Tibetan Plateau (NE-QTP). It provides insights into the response of dust activities to these wind systems for the last 18.5 ka. We developed a detailed chronology for ZES section based on luminescence dating of multiple signals from 29 samples (yielding a total of 87 ages). The luminescence sensitivities and element analysis of the sediments indicate a shift in dust source around 7.5 ka, contributed to a transition in the atmospheric circulation controls of the NE-QTP. Specially, our findings suggest that dust activity was likely dominated by EAWM from 18.5 ka to 7.5 ka and by the Westerlies after 7.5 ka across this area. We propose that increased NH ice volume (NHIV) significantly enhanced the EAWM via strengthening Siberian High, driving dust activities over the high mountains during the Last Deglaciation and Early Holocene. In contrast, as NHIV decreased during the middle-to-late Holocene, the EAWM weakened and retreated from this area, allowing the Westerlies to dominate dust activities. Additionally, grain-size parameters of sediments were used to infer variations in the intensities of these winds, revealing a gradual weakening of EAWM since the Last Deglaciation and a marked intensification of the Westerlies during the warm middle Holocene. Under the current global warming scenario, we predict that the Westerlies will continue to dominate dust activities across the NE-QTP, with a potential increase in dust activities if the Westerlies enhance.
{"title":"Alternating dominance of Westerlies and East Asian winter monsoon on dust activities across the northeastern Qinghai-Tibet Plateau since 18.5 ka","authors":"Hao Long, Yun Cai, Jingran Zhang, Liangqing Cheng, Linhai Yang, Hongyi Cheng","doi":"10.1016/j.gloplacha.2024.104684","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104684","url":null,"abstract":"The mid-latitude Westerlies and the East Asian winter monsoon (EAWM) are two major atmospheric circulation systems influencing dust activities in the Northern Hemisphere (NH). However, the interplay between these wind systems and their effects on regional dust activities remain poorly understood. In this study, we present a well-dated aeolian sedimentary sequence from the loess section (ZES) on the southern slope of the Qilian Mountains in the northeastern Qinghai-Tibetan Plateau (NE-QTP). It provides insights into the response of dust activities to these wind systems for the last 18.5 ka. We developed a detailed chronology for ZES section based on luminescence dating of multiple signals from 29 samples (yielding a total of 87 ages). The luminescence sensitivities and element analysis of the sediments indicate a shift in dust source around 7.5 ka, contributed to a transition in the atmospheric circulation controls of the NE-QTP. Specially, our findings suggest that dust activity was likely dominated by EAWM from 18.5 ka to 7.5 ka and by the Westerlies after 7.5 ka across this area. We propose that increased NH ice volume (NHIV) significantly enhanced the EAWM via strengthening Siberian High, driving dust activities over the high mountains during the Last Deglaciation and Early Holocene. In contrast, as NHIV decreased during the middle-to-late Holocene, the EAWM weakened and retreated from this area, allowing the Westerlies to dominate dust activities. Additionally, grain-size parameters of sediments were used to infer variations in the intensities of these winds, revealing a gradual weakening of EAWM since the Last Deglaciation and a marked intensification of the Westerlies during the warm middle Holocene. Under the current global warming scenario, we predict that the Westerlies will continue to dominate dust activities across the NE-QTP, with a potential increase in dust activities if the Westerlies enhance.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"11 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884634","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}
Corals' regulation of internal calcifying fluid (CF or cf) chemistry is crucial for their extraordinary calcification capacity, endowing them with a certain ability to cope with environmental changes such as anthropogenic ocean acidification (OA) and warming. However, it remains unclear whether the impacts of these changes on corals have substantially surpassed their regulation capacity, particularly in comparison to the CF chemistry responses to natural climate variability with minor or no human perturbation. In this study, we reconstructed the pH, dissolved inorganic carbon, and carbonate ion concentrations in coral CF (pHcf, DICcf, and [CO32−]cf) during the Mid- to Late-Holocene, by analyzing the skeletal δ11B and B/Ca of 80 Porites spp. from eastern Hainan Island in the South China Sea (SCS). Our records indicate considerable inter-colony variations in CF chemistry, with maximum disparities reaching 0.18 units for pHcf and 1664 μmol/kg for DICcf. With this in mind, we found no clear responses of coral DICcf to the climate fluctuations during the past ∼5500 years, nor evident differences in pHcf and [CO32−]cf across pre-industrial natural epochs. However, pHcf and [CO32−]cf of modern corals have significantly declined compared to fossil corals. Further analyzes compiling global data on Porites spp. also confirm this pronounced pHcf decrease in modern corals, suggesting the limitations of pantropical corals to counteract OA by up-regulating pHcf. Importantly, these fossil and modern corals reveal a clear long-term pHcf descending trend parallel to atmospheric CO2 changes, supporting the reliability of coral δ11B in recording long-term changes in seawater pH (pHsw).
{"title":"From holocene to anthropogenic impact: Surpassing coral's pH up-regulation capacity under ocean acidification","authors":"Huiling Kang, Xuefei Chen, Guangchao Deng, Jian-xin Zhao, Gangjian Wei","doi":"10.1016/j.gloplacha.2024.104683","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104683","url":null,"abstract":"Corals' regulation of internal calcifying fluid (CF or cf) chemistry is crucial for their extraordinary calcification capacity, endowing them with a certain ability to cope with environmental changes such as anthropogenic ocean acidification (OA) and warming. However, it remains unclear whether the impacts of these changes on corals have substantially surpassed their regulation capacity, particularly in comparison to the CF chemistry responses to natural climate variability with minor or no human perturbation. In this study, we reconstructed the pH, dissolved inorganic carbon, and carbonate ion concentrations in coral CF (pH<ce:inf loc=\"post\">cf</ce:inf>, DIC<ce:inf loc=\"post\">cf</ce:inf>, and [CO<ce:inf loc=\"post\">3</ce:inf><ce:sup loc=\"post\">2−</ce:sup>]<ce:inf loc=\"post\">cf</ce:inf>) during the Mid- to Late-Holocene, by analyzing the skeletal δ<ce:sup loc=\"post\">11</ce:sup>B and B/Ca of 80 <ce:italic>Porites</ce:italic> spp. from eastern Hainan Island in the South China Sea (SCS). Our records indicate considerable inter-colony variations in CF chemistry, with maximum disparities reaching 0.18 units for pH<ce:inf loc=\"post\">cf</ce:inf> and 1664 μmol/kg for DIC<ce:inf loc=\"post\">cf</ce:inf>. With this in mind, we found no clear responses of coral DIC<ce:inf loc=\"post\">cf</ce:inf> to the climate fluctuations during the past ∼5500 years, nor evident differences in pH<ce:inf loc=\"post\">cf</ce:inf> and [CO<ce:inf loc=\"post\">3</ce:inf><ce:sup loc=\"post\">2−</ce:sup>]<ce:inf loc=\"post\">cf</ce:inf> across pre-industrial natural epochs. However, pH<ce:inf loc=\"post\">cf</ce:inf> and [CO<ce:inf loc=\"post\">3</ce:inf><ce:sup loc=\"post\">2−</ce:sup>]<ce:inf loc=\"post\">cf</ce:inf> of modern corals have significantly declined compared to fossil corals. Further analyzes compiling global data on <ce:italic>Porites</ce:italic> spp. also confirm this pronounced pH<ce:inf loc=\"post\">cf</ce:inf> decrease in modern corals, suggesting the limitations of pantropical corals to counteract OA by up-regulating pH<ce:inf loc=\"post\">cf</ce:inf>. Importantly, these fossil and modern corals reveal a clear long-term pH<ce:inf loc=\"post\">cf</ce:inf> descending trend parallel to atmospheric CO<ce:inf loc=\"post\">2</ce:inf> changes, supporting the reliability of coral δ<ce:sup loc=\"post\">11</ce:sup>B in recording long-term changes in seawater pH (pH<ce:inf loc=\"post\">sw</ce:inf>).","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"3 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905670","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}
Pub Date : 2024-12-18DOI: 10.1016/j.gloplacha.2024.104679
Chao Chang, Thomas J. Algeo
The Cambrian Explosion was an unprecedented bioevolutionary event that witnessed rapid diversification of marine invertebrate phyla and establishment of metazoan-dominated marine ecosystems. Nitrogen is a critical nutrient element essential for all life on Earth, and its biogeochemical cycling in the ocean is tightly associated with marine redox conditions. Numerous nitrogen isotope investigations of the Ediacaran-Cambrian (E-C) transition have been undertaken, but an integrated analysis of contemporaneous nitrogen cycling has not been achieved yet. Here, we compile published nitrogen isotope data for the South China Craton over the interval from ∼550 Ma (late Ediacaran) to ∼514 Ma (late Stage 3 of early Cambrian) with the goals of identifying key changes in the nitrogen cycle and their relationship to marine redox evolution and the Cambrian Explosion. Combined with independent redox proxy data, our δ15N dataset provides insights into spatio-temporal variation in rates of denitrification and N2 fixation induced by marine redox fluctuations, which constrains the distribution of suboxic environments and the relative position of the oceanic redoxcline. On this basis, we propose a new model of marine nitrogen-cycle evolution during the E–C transition in which (1) nitrate availability modulated the ecological development and distribution of eukaryotic primary producers, and (2) nitrate-replete ecological niches for eukaryotic primary producers, especially benthic algae expanded significantly during Cambrian Age 3, and (3) increasing biological pump efficiency promoted organic burial and net O2 release, thus contributing to oceanic oxygenation and the radiation of early animals.
{"title":"Nitrogen cycling and marine redox evolution during the Ediacaran–Cambrian transition","authors":"Chao Chang, Thomas J. Algeo","doi":"10.1016/j.gloplacha.2024.104679","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104679","url":null,"abstract":"The Cambrian Explosion was an unprecedented bioevolutionary event that witnessed rapid diversification of marine invertebrate phyla and establishment of metazoan-dominated marine ecosystems. Nitrogen is a critical nutrient element essential for all life on Earth, and its biogeochemical cycling in the ocean is tightly associated with marine redox conditions. Numerous nitrogen isotope investigations of the Ediacaran-Cambrian (<ce:italic>E</ce:italic>-C) transition have been undertaken, but an integrated analysis of contemporaneous nitrogen cycling has not been achieved yet. Here, we compile published nitrogen isotope data for the South China Craton over the interval from ∼550 Ma (late Ediacaran) to ∼514 Ma (late Stage 3 of early Cambrian) with the goals of identifying key changes in the nitrogen cycle and their relationship to marine redox evolution and the Cambrian Explosion. Combined with independent redox proxy data, our δ<ce:sup loc=\"post\">15</ce:sup>N dataset provides insights into spatio-temporal variation in rates of denitrification and N<ce:inf loc=\"post\">2</ce:inf> fixation induced by marine redox fluctuations, which constrains the distribution of suboxic environments and the relative position of the oceanic redoxcline. On this basis, we propose a new model of marine nitrogen-cycle evolution during the E–C transition in which (1) nitrate availability modulated the ecological development and distribution of eukaryotic primary producers, and (2) nitrate-replete ecological niches for eukaryotic primary producers, especially benthic algae expanded significantly during Cambrian Age 3, and (3) increasing biological pump efficiency promoted organic burial and net O<ce:inf loc=\"post\">2</ce:inf> release, thus contributing to oceanic oxygenation and the radiation of early animals.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"25 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884637","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}
Pub Date : 2024-12-18DOI: 10.1016/j.gloplacha.2024.104681
Jinlong Du, Jun Tian, Aixue Hu, Yongqiang Yu, Baohuang Su, Dabang Jiang
The presence of the Tibetan Plateau is believed to lower pCO2atm by stimulating weathering carbon sink, during which the global ocean is considered a passive carbon reservoir despite the tremendous marine carbon inventory. Yet, recent studies reveal that the orographic forcing of the Tibetan Plateau could lead to drastic changes in ocean circulation, which would substantially affect basin-scale carbon storage and hence pCO2atm. However, this connection between the presence of the Tibetan Plateau and changes in the oceanic carbon inventory remains insufficiently investigated. Here, by employing a state-of-the-art ocean-biogeochemical model, we explore the role of the Tibetan Plateau in determining basin-scale carbon storage patterns based on an idealized experimental design. We find that the presence of the Tibetan Plateau substantially enhances deep Pacific carbon storage and hence lowers pCO2atm via essential reorganization of the meridional overturning circulation, particularly associated with the development of the Pacific halocline. Moreover, the presence of the Tibetan Plateau greatly affects the oceanic carbon uptake in the Northern Hemisphere, which is likely controlled by the variations in surface alkalinity.
{"title":"The presence of the Tibetan Plateau lowers atmospheric CO2 levels via the Atlantic-Pacific carbon seesaw","authors":"Jinlong Du, Jun Tian, Aixue Hu, Yongqiang Yu, Baohuang Su, Dabang Jiang","doi":"10.1016/j.gloplacha.2024.104681","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104681","url":null,"abstract":"The presence of the Tibetan Plateau is believed to lower <ce:italic>p</ce:italic>CO<ce:inf loc=\"post\">2</ce:inf><ce:sup loc=\"post\">atm</ce:sup> by stimulating weathering carbon sink, during which the global ocean is considered a passive carbon reservoir despite the tremendous marine carbon inventory. Yet, recent studies reveal that the orographic forcing of the Tibetan Plateau could lead to drastic changes in ocean circulation, which would substantially affect basin-scale carbon storage and hence <ce:italic>p</ce:italic>CO<ce:inf loc=\"post\">2</ce:inf><ce:sup loc=\"post\">atm</ce:sup>. However, this connection between the presence of the Tibetan Plateau and changes in the oceanic carbon inventory remains insufficiently investigated. Here, by employing a state-of-the-art ocean-biogeochemical model, we explore the role of the Tibetan Plateau in determining basin-scale carbon storage patterns based on an idealized experimental design. We find that the presence of the Tibetan Plateau substantially enhances deep Pacific carbon storage and hence lowers <ce:italic>p</ce:italic>CO<ce:inf loc=\"post\">2</ce:inf><ce:sup loc=\"post\">atm</ce:sup> via essential reorganization of the meridional overturning circulation, particularly associated with the development of the Pacific halocline. Moreover, the presence of the Tibetan Plateau greatly affects the oceanic carbon uptake in the Northern Hemisphere, which is likely controlled by the variations in surface alkalinity.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"132 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884639","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}
Pub Date : 2024-12-16DOI: 10.1016/j.gloplacha.2024.104680
Yan-Xia Xue, Yao Wu, Chao-Jun Chen, Jun-Yun Li, Hai Cheng, Chuan-Chou Shen, Jian Zhang, Ting-Yong Li
There are still a series of controversies about the variation patterns and spatial differences of the Asian summer monsoon (ASM) during the Heinrich Stadials (HSs). Using stalagmite δ18O records from Yangkou Cave, Southwest China, this study revealed the climate dynamics of 6 weak ASM events corresponding to Heinrich events since the last glacial period. During the Asian Heinrich Stadial (AHS) 1–6, the ASM intensity in northern China responded rapidly to climate change in the North Atlantic, whereas the response in southern China was gradual. Ocean-atmosphere interactions under the bipolar “see-saw” mechanism dominated the ASM dynamics during the HSs. The ASM strengthening in the south of the Asian monsoon region was earlier and more gradual than in the north during the termination of the AHS, implying that the Southern Hemisphere high latitudes and tropical oceans played a critical role in the termination of millennial-scale abrupt climatic events. According to our observations, variations in moisture transport distances resulted in spatial differences in amplitude of stalagmite δ18O during the AHSs, implying that δ18O can reflect the hydrological imprint of variation in the ASM circulation.
{"title":"Evolution of the Asian summer monsoon during the Heinrich events 1–6","authors":"Yan-Xia Xue, Yao Wu, Chao-Jun Chen, Jun-Yun Li, Hai Cheng, Chuan-Chou Shen, Jian Zhang, Ting-Yong Li","doi":"10.1016/j.gloplacha.2024.104680","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104680","url":null,"abstract":"There are still a series of controversies about the variation patterns and spatial differences of the Asian summer monsoon (ASM) during the Heinrich Stadials (HSs). Using stalagmite δ<ce:sup loc=\"post\">18</ce:sup>O records from Yangkou Cave, Southwest China, this study revealed the climate dynamics of 6 weak ASM events corresponding to Heinrich events since the last glacial period. During the Asian Heinrich Stadial (AHS) 1–6, the ASM intensity in northern China responded rapidly to climate change in the North Atlantic, whereas the response in southern China was gradual. Ocean-atmosphere interactions under the bipolar “see-saw” mechanism dominated the ASM dynamics during the HSs. The ASM strengthening in the south of the Asian monsoon region was earlier and more gradual than in the north during the termination of the AHS, implying that the Southern Hemisphere high latitudes and tropical oceans played a critical role in the termination of millennial-scale abrupt climatic events. According to our observations, variations in moisture transport distances resulted in spatial differences in amplitude of stalagmite δ<ce:sup loc=\"post\">18</ce:sup>O during the AHSs, implying that δ<ce:sup loc=\"post\">18</ce:sup>O can reflect the hydrological imprint of variation in the ASM circulation.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"1 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884633","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}
Net Primary Productivity (NPP) is an index for assessing ecosystem services and productivity on land. However, previous studies focused solely on NPP changes across ecological regions, overlooking the comparative advantage of the impacts of land changes and climatic variations on various forms of NPP as indicators of ecosystem degradation and restoration across different eco-political milieux. This study comparatively analyzed land cover changes and examined NPP trends and their effects using Mann-Kendall Theil-Sen slopes, the Pearson correlation, and advanced geostatistical methods in the Lake Chad Basin (LCB) and the Aral Sea Basin (ASB). We found that from 2000 to the present and projected to 2030, cropland is expected to expand by 2.20 %, leading to a reduction of shrubland by −2.40 % in LCB. Likewise, a probable increase of 1.1 % in grassland is expected to further reduce waterbodies in ASB by −1.5 %. These potential changes are the resultant effect of the present human-induced NPP (HNPP) reduction of −5.92gC/m2/yr across 2.44 × 103 km2 and 29.84gC/m2/yr across 14.32× 103 km2, indicating human-dominated degradation (HDD) in LCB. Whereas, in ASB, the influence of HNPP by −8.12 gC/m2/yr across 14.32 × 103 km2 and by 4.00gC/m2/yr across 7.24× 103 km2 indicate incipient human-dominated restoration scenarios. Consequent to the warming temperature, climate fluctuations are characterized by HDD in LCB, whereas in ASB, they are characterized by climate-induced degradation. Apprehending these evolving dynamics in endorheic lakes can provide insight into potential restoration trajectories for future land degradations.
{"title":"Combined impacts of land change and climate variability on ecosystem net primary productivity in arid regions","authors":"Emeka Edwin Igboeli, Ogbue Chukwuka, Friday Uchenna Ochege, Chukwuemeka Anthony Onyekwelu, Qing Ling, Chukwuedozie Ajaero, Rafiq Hamdi, Mijanur Rahman, Alphonse Kayiranga, Geping Luo","doi":"10.1016/j.gloplacha.2024.104682","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104682","url":null,"abstract":"Net Primary Productivity (NPP) is an index for assessing ecosystem services and productivity on land. However, previous studies focused solely on NPP changes across ecological regions, overlooking the comparative advantage of the impacts of land changes and climatic variations on various forms of NPP as indicators of ecosystem degradation and restoration across different eco-political milieux. This study comparatively analyzed land cover changes and examined NPP trends and their effects using Mann-Kendall Theil-Sen slopes, the Pearson correlation, and advanced geostatistical methods in the Lake Chad Basin (LCB) and the Aral Sea Basin (ASB). We found that from 2000 to the present and projected to 2030, cropland is expected to expand by 2.20 %, leading to a reduction of shrubland by −2.40 % in LCB. Likewise, a probable increase of 1.1 % in grassland is expected to further reduce waterbodies in ASB by −1.5 %. These potential changes are the resultant effect of the present human-induced NPP (HNPP) reduction of −5.92gC/m<ce:sup loc=\"post\">2</ce:sup>/yr across 2.44 × 10<ce:sup loc=\"post\">3</ce:sup> km<ce:sup loc=\"post\">2</ce:sup> and 29.84gC/m<ce:sup loc=\"post\">2</ce:sup>/yr across 14.32× 10<ce:sup loc=\"post\">3</ce:sup> km<ce:sup loc=\"post\">2</ce:sup>, indicating human-dominated degradation (HDD) in LCB. Whereas, in ASB, the influence of HNPP by −8.12 gC/m<ce:sup loc=\"post\">2</ce:sup>/yr across 14.32 × 10<ce:sup loc=\"post\">3</ce:sup> km<ce:sup loc=\"post\">2</ce:sup> and by 4.00gC/m<ce:sup loc=\"post\">2</ce:sup>/yr across 7.24× 10<ce:sup loc=\"post\">3</ce:sup> km<ce:sup loc=\"post\">2</ce:sup> indicate incipient human-dominated restoration scenarios. Consequent to the warming temperature, climate fluctuations are characterized by HDD in LCB, whereas in ASB, they are characterized by climate-induced degradation. Apprehending these evolving dynamics in endorheic lakes can provide insight into potential restoration trajectories for future land degradations.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"65 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884640","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}
Global warming has significantly accelerated the retreat of glaciers and expansion of glacial lakes in the central Himalayas, thereby heightening the risks of various disasters, including ice avalanches, rock avalanches, and glacial lake outburst floods (GLOFs). These events pose considerable threats to the lives and properties of individuals residing in downstream areas. Consequently, conducting comprehensive research into the geographical distribution, formation, and evolutionary processes of glacial lakes, along with assessments of the potential impacts of GLOFs on climate change, is critically important for developing strategies to mitigate associated risks. To address this need, we propose a dynamic threshold method (known as OTSU) to facilitate the automatic and precise extraction of glacial lake boundaries in the central Himalayas. This innovative approach leverages the enhanced normalized difference water index (ENDWI), derived from multi-temporal Landsat series remote sensing imagery and Sentinel-2A /2B datasets, which were sourced from the Google Earth Engine (GEE) platform for the years 1990–2022. In addition to extracting lake boundaries, we examined the spatiotemporal evolution characteristics of glacial lakes in the region. Moreover, mathematical statistics were employed to systematically organize and analyse the GLOF disaster events in the central Himalayas. Finally, thoroughly investigate the interplay between glacial lake evolution and climate change, we incorporated relevant meteorological data. The present findings reveal that: 1) Glacial lakes are primarily distributed in the border area between China and Nepal in the central Himalayas, composed of non-contact lakes with glaciers, and concentrated in the altitude range of 3600–5900 m. 2) Since the 1990s, the expansion of glacial lakes is predominated by small glacial lakes in the central Himalayas; there have been 847 new glacial lakes, and the area and volume of glacial lakes has increased by 88.61 ± 4.64 km2 and 24.72 ± 2.59 km3, respectively. 3) Global warming, coupled with the escalating rates of glacial meltwater, serves as the primary catalyst for the proliferation of glacial lakes. This multifaceted approach aims to provide a clearer understanding of the dynamics at play in this vulnerable region and to inform effective risk management strategies. Since 1950, there has been a significant increase in the frequency of GLOFs, with the month of June demonstrating the highest incidence, followed closely by August. These glacial lake outbursts are predominantly instigated by ice avalanches. The present findings provide valuable scientific insights that could contribute to the mitigation of regional natural disasters.
{"title":"Temporal and spatial changes of glacial lakes in the central Himalayas and their response to climate change based on multi-source remote sensing data","authors":"Xiaoqiang Cheng, Donghui Shangguan, Chengsheng Yang, Wangping Li, Zhaoye Zhou, Xiaojie Liu, Da Li, Xiuxia Zhang, Huilan Ding, Zewei Liu, Yi Yu, Xiaoxian Wang, Beibei He, Qin Yang, Yaojun Li, Rongjun Wang, Yadong Liu, Lingzhi Deng, Yanzi Shi","doi":"10.1016/j.gloplacha.2024.104675","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104675","url":null,"abstract":"Global warming has significantly accelerated the retreat of glaciers and expansion of glacial lakes in the central Himalayas, thereby heightening the risks of various disasters, including ice avalanches, rock avalanches, and glacial lake outburst floods (GLOFs). These events pose considerable threats to the lives and properties of individuals residing in downstream areas. Consequently, conducting comprehensive research into the geographical distribution, formation, and evolutionary processes of glacial lakes, along with assessments of the potential impacts of GLOFs on climate change, is critically important for developing strategies to mitigate associated risks. To address this need, we propose a dynamic threshold method (known as OTSU) to facilitate the automatic and precise extraction of glacial lake boundaries in the central Himalayas. This innovative approach leverages the enhanced normalized difference water index (ENDWI), derived from multi-temporal Landsat series remote sensing imagery and Sentinel-2A /2B datasets, which were sourced from the Google Earth Engine (GEE) platform for the years 1990–2022. In addition to extracting lake boundaries, we examined the spatiotemporal evolution characteristics of glacial lakes in the region. Moreover, mathematical statistics were employed to systematically organize and analyse the GLOF disaster events in the central Himalayas. Finally, thoroughly investigate the interplay between glacial lake evolution and climate change, we incorporated relevant meteorological data. The present findings reveal that: 1) Glacial lakes are primarily distributed in the border area between China and Nepal in the central Himalayas, composed of non-contact lakes with glaciers, and concentrated in the altitude range of 3600–5900 m. 2) Since the 1990s, the expansion of glacial lakes is predominated by small glacial lakes in the central Himalayas; there have been 847 new glacial lakes, and the area and volume of glacial lakes has increased by 88.61 ± 4.64 km<ce:sup loc=\"post\">2</ce:sup> and 24.72 ± 2.59 km<ce:sup loc=\"post\">3</ce:sup>, respectively. 3) Global warming, coupled with the escalating rates of glacial meltwater, serves as the primary catalyst for the proliferation of glacial lakes. This multifaceted approach aims to provide a clearer understanding of the dynamics at play in this vulnerable region and to inform effective risk management strategies. Since 1950, there has been a significant increase in the frequency of GLOFs, with the month of June demonstrating the highest incidence, followed closely by August. These glacial lake outbursts are predominantly instigated by ice avalanches. The present findings provide valuable scientific insights that could contribute to the mitigation of regional natural disasters.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"115 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841208","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}
Heterotrophic bacterial production represents an important part of microbial food web processes in marine ecosystems and plays a significant role in biogeochemical carbon cycle. As environmental factors have changed in marginal seas of the Western Pacific Ocean over the past 20 years, the response and regulation of bacterial production remain poorly understood. In this study, we quantified bacterial production rates using the 3H-leucine incorporation method and investigated the factors influencing bacterial production distributions in the East China Sea and the Yellow Sea. Our data revealed that bacterial production varied largely (1.6–24.4 mg C m−3 d−1) in the surface waters, and higher rates were observed at temperate sites in the East China Sea. Incubation experiments under different temperature or nutrient conditions demonstrated that elevated temperature or the addition of silicate, DIN and phosphate could simulate heterotrophic activity. The decadal increases of BP could be a result of microbial response to the variations in temperature, nutrient levels, and dissolved oxygen that are closely linked to food-web dynamics and biogeochemical processes. High ratios of integrated bacterial production to primary production suggested bacterial production could be supported by non-phytoplanktonic carbon sources, while the low bacterial growth efficiency indicated that a large fraction of carbon was respired in the offshore waters. These results provided insights into the regulations of BP and heterotrophic response to environmental evolution in marginal seas of the Western Pacific Ocean.
异养细菌的产生是海洋生态系统微生物食物网过程的重要组成部分，在生物地球化学碳循环中起着重要作用。近20年来，随着西太平洋边缘海域环境因素的变化，对细菌产生的反应和调控仍知之甚少。本研究采用3h -亮氨酸掺入法定量研究了东海和黄海海域细菌产量分布的影响因素。我们的数据显示，细菌产量在地表水中变化很大（1.6-24.4 mg C m−3 d−1），并且在东海温带地区观察到更高的速率。不同温度和营养条件下的培养实验表明，提高温度或添加硅酸盐、DIN和磷酸盐可以模拟异养活性。BP的年代际增加可能是微生物对温度、营养水平和溶解氧变化的反应，这些变化与食物网动态和生物地球化学过程密切相关。综合细菌生产与初级生产的高比率表明细菌生产可能由非浮游植物碳源支持，而细菌生长效率低表明大部分碳是在近海水域呼吸的。这些结果为揭示西太平洋边缘海BP的变化规律和异养响应环境演化提供了新的思路。
{"title":"Regulation and response of heterotrophic bacterial production to environmental changes in marginal seas of the Western Pacific Ocean","authors":"Qiao Liu, Jinyan Wang, Xiao-Jun Li, Ni Meng, Gui-Peng Yang, Guiling Zhang, Guang-Chao Zhuang","doi":"10.1016/j.gloplacha.2024.104678","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104678","url":null,"abstract":"Heterotrophic bacterial production represents an important part of microbial food web processes in marine ecosystems and plays a significant role in biogeochemical carbon cycle. As environmental factors have changed in marginal seas of the Western Pacific Ocean over the past 20 years, the response and regulation of bacterial production remain poorly understood. In this study, we quantified bacterial production rates using the <ce:sup loc=\"post\">3</ce:sup>H-leucine incorporation method and investigated the factors influencing bacterial production distributions in the East China Sea and the Yellow Sea. Our data revealed that bacterial production varied largely (1.6–24.4 mg C m<ce:sup loc=\"post\">−3</ce:sup> d<ce:sup loc=\"post\">−1</ce:sup>) in the surface waters, and higher rates were observed at temperate sites in the East China Sea. Incubation experiments under different temperature or nutrient conditions demonstrated that elevated temperature or the addition of silicate, DIN and phosphate could simulate heterotrophic activity. The decadal increases of BP could be a result of microbial response to the variations in temperature, nutrient levels, and dissolved oxygen that are closely linked to food-web dynamics and biogeochemical processes. High ratios of integrated bacterial production to primary production suggested bacterial production could be supported by non-phytoplanktonic carbon sources, while the low bacterial growth efficiency indicated that a large fraction of carbon was respired in the offshore waters. These results provided insights into the regulations of BP and heterotrophic response to environmental evolution in marginal seas of the Western Pacific Ocean.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"294 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884636","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}
Pub Date : 2024-12-11DOI: 10.1016/j.gloplacha.2024.104677
Kunyuan Ma, Linda Hinnov, Zhihong Wang, Kai Wang, Ruiwen Zong, Xinsong Zhang, Junjun Song, Yang Bai, Yiming Gong
The Hongguleleng Formation in western Junggar, northwest China preserves a rich variety of fossils and was previously regarded as a “refugium” during the Late Devonian biotic crisis. Uncertainty in the age of the Hongguleleng Formation has persisted for a considerable time. In this study, cyclostratigraphic analysis was carried out on the Upper Devonian Bulongguoer and Wulankeshun sections from western Junggar, northwest China. Time series analysis and modeling of iron (Fe) concentration proxy data reveal variations with frequencies comparable to those of the Earth's long and short orbital eccentricity, obliquity, and precession index in both successions. Interpreted 405-kyr long orbital eccentricity cycles were used to establish floating astronomical time scales (FATs) for the two successions. From these FATs the depositional duration of the Hongguleleng Formation is calculated as 11.5 ± 0.58 Myr. The Devonian-Carboniferous boundary age of 359.3 ± 0.3 Ma was chosen as a time “anchor”, resulting in an astronomically determined age of 370.2 ± 0.66 Ma for the base of the Hongguleleng Formation. Combined with conodont biostratigraphy, this age indicates that the Hongguleleng Formation in western Junggar does not reach down to the Frasnian-Famennian boundary. Sedimentary noise modeling of the reconstructed Fe concentration time series provides an interpretation of sea-level variations in the Paleo-Asian Ocean controlled by astronomical forcing from very long orbital eccentricity cycles (g4–g3) throughout the Late Devonian period. Intensified monsoonal climates during these orbital eccentricity cycle maxima led to elevated terrigenous input and strengthened upwelling, which enhanced primary productivity in the western Junggar. We propose an “astronomical climate change” model as a driving mechanism that led to biotic recovery in the Famennian Hongguleleng Formation.
{"title":"Astronomically forced dynamics of Late Devonian (Famennian) sea level and biotic recovery in western Junggar, Northwest China","authors":"Kunyuan Ma, Linda Hinnov, Zhihong Wang, Kai Wang, Ruiwen Zong, Xinsong Zhang, Junjun Song, Yang Bai, Yiming Gong","doi":"10.1016/j.gloplacha.2024.104677","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104677","url":null,"abstract":"The Hongguleleng Formation in western Junggar, northwest China preserves a rich variety of fossils and was previously regarded as a “refugium” during the Late Devonian biotic crisis. Uncertainty in the age of the Hongguleleng Formation has persisted for a considerable time. In this study, cyclostratigraphic analysis was carried out on the Upper Devonian Bulongguoer and Wulankeshun sections from western Junggar, northwest China. Time series analysis and modeling of iron (Fe) concentration proxy data reveal variations with frequencies comparable to those of the Earth's long and short orbital eccentricity, obliquity, and precession index in both successions. Interpreted 405-kyr long orbital eccentricity cycles were used to establish floating astronomical time scales (FATs) for the two successions. From these FATs the depositional duration of the Hongguleleng Formation is calculated as 11.5 ± 0.58 Myr. The Devonian-Carboniferous boundary age of 359.3 ± 0.3 Ma was chosen as a time “anchor”, resulting in an astronomically determined age of 370.2 ± 0.66 Ma for the base of the Hongguleleng Formation. Combined with conodont biostratigraphy, this age indicates that the Hongguleleng Formation in western Junggar does not reach down to the Frasnian-Famennian boundary. Sedimentary noise modeling of the reconstructed Fe concentration time series provides an interpretation of sea-level variations in the Paleo-Asian Ocean controlled by astronomical forcing from very long orbital eccentricity cycles (<ce:italic>g</ce:italic><ce:inf loc=\"post\">4</ce:inf>–<ce:italic>g</ce:italic><ce:inf loc=\"post\">3</ce:inf>) throughout the Late Devonian period. Intensified monsoonal climates during these orbital eccentricity cycle maxima led to elevated terrigenous input and strengthened upwelling, which enhanced primary productivity in the western Junggar. We propose an “astronomical climate change” model as a driving mechanism that led to biotic recovery in the Famennian Hongguleleng Formation.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"172 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841257","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}
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